1 00:00:08,480 --> 00:00:16,640 Okay. Good afternoon, everybody. It's a great pleasure to welcome my old friend all afternoon to give the colloquium. 2 00:00:17,030 --> 00:00:21,379 So if the market is not true and the challenges of our treaties with, we'd like to buy it. 3 00:00:21,380 --> 00:00:31,459 But in the late 1980s, when you worked on worked on Diamond, they were very I remember they were very, very keen on only diamonds. 4 00:00:31,460 --> 00:00:37,250 And I don't think anybody would really have predicted to what extent diamonds would become important technologically, 5 00:00:37,880 --> 00:00:47,180 as important as they have over the last decade or so, after he was in office about for about ten years, and then moved on to King's College, 6 00:00:47,180 --> 00:00:53,270 London, and then in 2000 to move to the White House, where he's now professor. 7 00:00:54,260 --> 00:01:02,839 The market is a complete fan for selling of diamonds and a diamond is just about is you know is ever been to 8 00:01:02,840 --> 00:01:08,450 Mars and he's a solar physicist who if you walked up to sit down beside you in the coffee room and said, 9 00:01:08,840 --> 00:01:12,620 I've got something interesting, you won't be you want to see it, right? 10 00:01:13,220 --> 00:01:20,410 You should say yes, because something will come out of the clock and you can be sure that it's time, maybe the time, right? 11 00:01:20,690 --> 00:01:26,750 But beyond that, you have no idea of what properties that you would build, have expected have done that is going to happen. 12 00:01:26,990 --> 00:01:31,640 So March 31st, the estate markets talk to us about engineering feedbacks and Don. 13 00:01:32,150 --> 00:01:37,160 John, thank you very much for the kind introduction as it made me smile because of course, 14 00:01:38,300 --> 00:01:43,280 when I was here in the nineties doing diamond research and the people that 15 00:01:43,280 --> 00:01:46,850 were hardest to convince that it was going to be used for one day were APAC. 16 00:01:47,540 --> 00:01:51,980 And I think that's probably true for many people's research careers. 17 00:01:52,670 --> 00:01:58,340 So. This is going to be hopefully a little bit of light relief, of course. 18 00:01:58,550 --> 00:02:02,930 Matthew Dale, Ben Breese, a Ph.D. students who've done most of the work. 19 00:02:03,770 --> 00:02:07,240 Ben Green is a postdoc and has lots of very, very good ideas. 20 00:02:07,250 --> 00:02:13,280 A very bright young post-doc, Anita Shima, and the soil collaborators in Japan. 21 00:02:13,730 --> 00:02:21,800 And of course, I'm just the administrator who writes the grant applications and is very rarely allowed in the lab anymore. 22 00:02:22,910 --> 00:02:26,010 And this is just to get that way early. 23 00:02:26,030 --> 00:02:32,689 So this is just advertising a collaborative project in which Warwick and Oxford are both partners. 24 00:02:32,690 --> 00:02:38,810 We have a doctoral training centred centre focussed on diamond science and technology, 25 00:02:39,260 --> 00:02:48,620 and this is looking at all applications of diamond and and all sorts of science that can be done with diamond. 26 00:02:50,360 --> 00:03:01,190 And I think we're very lucky in that we have some very, very able PhD students now who are taking this forward. 27 00:03:02,820 --> 00:03:07,200 So as John said, I'm now at the University of Warwick. 28 00:03:08,220 --> 00:03:13,080 These are just some pictures of part of our laboratory. 29 00:03:13,720 --> 00:03:18,390 And Warwick is a very young university compared to Oxford. 30 00:03:18,870 --> 00:03:27,270 And there are some advantages to having greenfield sites to when you want to build new buildings and generate and lab space and. 31 00:03:28,300 --> 00:03:36,220 I have colleagues that do Solid-state Anima and several colleagues am pinched from Oxford who are now working. 32 00:03:36,220 --> 00:03:48,520 Warwick So we have a range of shared lab space and we do magnetic resonance from zero field all the way up to 20. 33 00:03:48,550 --> 00:03:55,930 Tesla And the system at the Frontier is a system for dynamic nuclear polarisation. 34 00:03:57,130 --> 00:04:03,459 And here we have a 200 gigahertz extended interaction classroom strong. 35 00:04:03,460 --> 00:04:09,880 So if you go and look at the cases outside, you will see some of the early 1940s closed on and that's basically where the 36 00:04:09,880 --> 00:04:14,860 technology has got to and certainly the upper limits of the frequencies that work. 37 00:04:16,390 --> 00:04:26,620 And then it is in a Perspex box because this is generating ten watts at this very, very high frequency. 38 00:04:26,920 --> 00:04:31,540 And an interesting phenomenon is that you have lots of nerve endings near the surface. 39 00:04:32,020 --> 00:04:40,210 The skin depth of the microwaves is very short at these high frequencies, and it hurts like [INAUDIBLE] if you put your hand in the beam. 40 00:04:40,990 --> 00:04:54,130 So it's advisable not to. Now, when you come anywhere and give a talk on Diamond, this is what people think of this is a 50 carat, 41 00:04:55,360 --> 00:04:58,899 flawless d in colour, which is the best colour you can get. 42 00:04:58,900 --> 00:05:02,320 Natural diamond. That was sold. 43 00:05:02,710 --> 00:05:05,740 It would build your new building and the stone. 44 00:05:07,200 --> 00:05:15,020 Well, nearly. Anyway, pretty close. And and this is a blight to anybody working on Diamond, because before you start, 45 00:05:15,030 --> 00:05:21,660 everybody thinks it's going to be phenomenally expensive to work on Diamond. 46 00:05:22,140 --> 00:05:26,190 And then everybody thinks that, well, diamonds come out of the ground. 47 00:05:26,370 --> 00:05:35,910 So how on earth could you have a semiconductor type technology based on a material whose properties you can't control? 48 00:05:38,440 --> 00:05:49,239 But synthetic diamond has been around since the 1950s and primarily is used, as have been traditional ones, 49 00:05:49,240 --> 00:05:57,130 exploiting the properties of extreme hardness and high thermal conductivity. 50 00:05:57,670 --> 00:06:01,920 So applications are cutting, sawing, grinding, 51 00:06:01,930 --> 00:06:09,129 so the cutting and drilling and you wouldn't have Airbuses without diamond tools 52 00:06:09,130 --> 00:06:14,650 because two machine the composite materials and the bottom left the shearing. 53 00:06:14,650 --> 00:06:27,250 That's a a bit for oil and gas drilling so that cutter can manage about 15 kilometres before the cutting tools become blunted. 54 00:06:28,030 --> 00:06:30,880 And this is not a good business to be in at the moment. 55 00:06:31,090 --> 00:06:39,850 And exploration has crashed and disappeared for a while, but the technology is hugely impressive. 56 00:06:40,630 --> 00:06:44,320 And over on the bottom right, you've got where parts coated in diamond. 57 00:06:44,770 --> 00:06:52,210 So very low friction surface and very stable dimensions don't change. 58 00:06:52,660 --> 00:06:57,340 And so again, a huge number of applications there. 59 00:06:58,030 --> 00:07:08,410 So here we're talking about a worldwide business that is two, three, $4 billion a year just using. 60 00:07:09,940 --> 00:07:15,999 The abrasive properties. Now, clearly, as a scientist, 61 00:07:16,000 --> 00:07:26,230 we would like to go beyond simply exploiting one of the properties of Diamond because diamonds got a whole combination of extreme properties. 62 00:07:26,950 --> 00:07:36,250 So electronics. As a colleague at work, Evan Parker said, Diamond is the material of the future, and it always will be. 63 00:07:37,210 --> 00:07:44,020 And in many ways this is sort of true, as in it's very hard to beat silicon for any electronic application. 64 00:07:45,220 --> 00:07:51,640 But in terms of thermal management and diamonds, thermal diffusivity, 65 00:07:51,640 --> 00:07:57,820 the rate that you can spread heat is 25 times better than copper and it is a very good insulator. 66 00:07:58,540 --> 00:08:11,110 So there are many applications where Diamond is integral in thermal management and there's a whole generation of gallium nitride power electronics, 67 00:08:11,530 --> 00:08:18,490 which is probably going to be enabled because the GAN is either bonded to or grown on diamond. 68 00:08:19,850 --> 00:08:25,280 Hyper infrared windows and diamond has displaced materials like zinc, 69 00:08:25,280 --> 00:08:33,380 selenite and refractive index doesn't change very quickly with temperature, high thermal conductivity mechanically very strong. 70 00:08:33,740 --> 00:08:37,610 You can put very precise coatings on it. 71 00:08:38,240 --> 00:08:42,379 And I'm sure people in the audience know more about this than I do. 72 00:08:42,380 --> 00:08:50,150 But the 13 nanometre lithography that Intel and others are working on is a molten drop of ten. 73 00:08:50,150 --> 00:08:55,640 I believe this drips is hit by a ten kilowatt infrared laser to vaporise it. 74 00:08:56,060 --> 00:09:01,580 And then in turn, internal electronics of now atomic physics transitions emit the light at 39 metres. 75 00:09:02,470 --> 00:09:08,590 So it's about ten kilowatts in, 400 watts out, and there's only going to be about half a dozen of these systems. 76 00:09:09,490 --> 00:09:14,210 But integral to it are the diamond windows to get the laser beam in. 77 00:09:15,910 --> 00:09:20,530 Wastewater treatment is one of my favourite. You get an example a little bit later on. 78 00:09:20,890 --> 00:09:25,270 You can Dope Diamond with Boron, which has a very high solubility in Diamond, 79 00:09:25,630 --> 00:09:30,640 such that it becomes metallic and even superconducting at low temperatures. 80 00:09:31,480 --> 00:09:36,490 But it can be metallic and yet retain many of the properties of diamond. 81 00:09:36,670 --> 00:09:44,350 It's chemically inert, doesn't corrode, doesn't fail, and it is possible to make very good electrodes out of it. 82 00:09:44,770 --> 00:09:51,640 And this business is now starting up using diamond electrodes to treat effluent. 83 00:09:53,080 --> 00:09:56,860 And so from diners to poo as the undergraduates like that. 84 00:09:58,870 --> 00:10:05,220 And of course, on the far right, some of the emerging applications are in quantum technologies. 85 00:10:05,230 --> 00:10:06,760 And I'll talk very briefly about that. 86 00:10:06,760 --> 00:10:13,840 But I'm not going to put many much emphasis on that today, but I'm sure others will talk about that here to great length. 87 00:10:15,730 --> 00:10:20,740 So where do diamonds come from? So the top left is a picture of the carting mine. 88 00:10:21,190 --> 00:10:23,830 This is one of the diverse group mines in Canada. 89 00:10:24,490 --> 00:10:33,910 So if anybody watches the program Ice Road Truckers in the winter, this is where the trucks are going, taking the equipment to build the mine. 90 00:10:35,650 --> 00:10:40,630 In the summer, it looks very pretty, but the mosquitoes are the size of light aircraft. 91 00:10:41,380 --> 00:10:44,620 And it is not it's not a pleasant place to be any time of the year. 92 00:10:46,070 --> 00:10:50,830 And in the bottom is the mine is now closed in Russia, the money mine. 93 00:10:51,340 --> 00:10:54,390 And there's a scale bar with a Lada and a truck. 94 00:10:54,400 --> 00:10:59,980 And you can see them heading down. This is up in northern Siberia. 95 00:11:00,280 --> 00:11:05,530 And the hole got so deep that it was so hot at the bottom that the permafrost was melting and the mine was falling into itself. 96 00:11:06,610 --> 00:11:12,340 So they gave up with that in the end. But this was the clue as to where diamonds came from. 97 00:11:12,550 --> 00:11:18,790 It had been transported in these vault kind of pipes, kimberlite pipes, from a few hundred kilometres down. 98 00:11:18,910 --> 00:11:23,560 So it was believed that Diamond was created under conditions of high pressure. 99 00:11:24,040 --> 00:11:27,580 It is the densest 3D form of carbon. 100 00:11:27,700 --> 00:11:31,870 So this seemed to make sense and high pressure. And I put this up because the. 101 00:11:31,870 --> 00:11:36,310 Berman Simon Lane is a really significant Oxford contribution. 102 00:11:37,030 --> 00:11:50,590 So Bobby Berman and some of you will remember I was funded as a postdoc by the De Beers group of companies in 1947, 103 00:11:51,010 --> 00:11:58,420 when De Beers realised that they couldn't do all of the research they needed to do to understand the physical properties of diamonds themselves. 104 00:11:59,080 --> 00:12:06,850 They had to get help from universities, and that started a university program of sponsoring research that's now been going 67 years. 105 00:12:07,450 --> 00:12:13,419 And Sir Francis Simon called Bobby Berman and he'd had a dinner in Christchurch 106 00:12:13,420 --> 00:12:16,870 with Nicky Oppenheimer and the king of asteroid Nicky Oppenheimer's grandfather, 107 00:12:17,320 --> 00:12:20,740 and said to him, Just Bill is what you need. 108 00:12:21,220 --> 00:12:29,950 So the Clarendon did, and Bobby's first challenge was to calculate the equilibrium line between graphite and diamonds, 109 00:12:29,950 --> 00:12:33,100 which is now known in the literature as the Berman Simon line. 110 00:12:33,940 --> 00:12:43,820 So you can see to go from graphite to diamond, we've got to go up in pressure to be able to do it. 111 00:12:45,070 --> 00:12:51,310 And the first reaction of somebody like me who knows very little about crystal growth is how hard can it be? 112 00:12:52,210 --> 00:13:00,400 As in, you take a supersaturated solution, you dangle, you'll see crystal in you let the solution evaporate in your crystal gracefully. 113 00:13:00,760 --> 00:13:06,940 And if you're going to be really high tech about it, you put a little dust cover over the top so particles don't drop into your solution. 114 00:13:07,600 --> 00:13:08,830 So it must be easy. 115 00:13:10,630 --> 00:13:20,020 While natural diamonds are typically formed about 200 kilometres down where you pass the Bourbon Simon line and you are in the diamond stable region, 116 00:13:20,530 --> 00:13:26,409 there is an argument as to where the carbon comes from and it's probably been grown 117 00:13:26,410 --> 00:13:32,500 from methane as a carbon source down there or a subducted organic carbon material. 118 00:13:33,070 --> 00:13:39,820 But interestingly, and natural diamonds are all 1000000000 to 3 and a half billion years old. 119 00:13:40,450 --> 00:13:46,180 Statistically, look, there looks like there's two epochs when they were grown and they've not been growing since. 120 00:13:46,990 --> 00:13:49,389 So we should rush out and buy on natural diamonds. 121 00:13:49,390 --> 00:14:00,340 They are a finite resource now and the temperature at a 150 kilometres down is about 1200 degrees C. 122 00:14:00,590 --> 00:14:10,450 So this is the region of growth. So we can reproduce that in the lab, of course, but we need a solvent in which carbon is soluble. 123 00:14:11,110 --> 00:14:17,770 So transition metals are good, but of course we're gonna have to melt it for it to work as a solvent. 124 00:14:19,330 --> 00:14:24,850 So we are talking about temperatures above 3000 degrees C So we're inside effectively the core 125 00:14:24,850 --> 00:14:30,700 of a nuclear reactor to get the temperatures required and to get to 152 kilometres down, 126 00:14:30,700 --> 00:14:33,319 we have to take the Eiffel Tower and balance it on a Coke. 127 00:14:33,320 --> 00:14:41,230 Can those sort of pressures we're talking about, so high pressures, high temperature, this is probably not that easy. 128 00:14:42,490 --> 00:14:46,210 So Top Left is a historical picture from 1954. 129 00:14:46,870 --> 00:14:50,319 And do we have any Americans here? Uh oh, yes. 130 00:14:50,320 --> 00:14:53,800 I wouldn't be too rude then about Americans. The Americans didn't trust the British. 131 00:14:54,520 --> 00:14:57,850 The De Beers were a UK based company, 132 00:14:58,120 --> 00:15:01,749 and it became clear during the Second World War that diamonds were terrifically important 133 00:15:01,750 --> 00:15:08,350 for machining components made out of all sorts of metals and other hard materials. 134 00:15:08,920 --> 00:15:13,960 And the US government was very nervous that it didn't have any supply of diamonds. 135 00:15:14,380 --> 00:15:19,870 So it funded with General Electric, the so-called Superabrasive project to grow synthetic diamond. 136 00:15:20,470 --> 00:15:31,540 So G effectively has infinite funding and this is Tracy Hall are working on their first high pressure high temperature press to get to 137 00:15:31,540 --> 00:15:43,000 these extreme conditions to grow diamond and they were the first to succeed so say that was in 1954 and the top picture is a press hole. 138 00:15:44,040 --> 00:15:46,560 Using these so-called buzz presses. 139 00:15:46,590 --> 00:15:55,560 And underneath them you can see the captain in the bars press is about a two and a half centimetres cube dimension, 140 00:15:56,340 --> 00:16:03,480 and it sits in a little pressure vessel with these anvils and then a secondary set of anvils, and it's water pressure to generate external pressure. 141 00:16:03,930 --> 00:16:11,310 So these will get you to 1500 degrees C and five and a half GIGAPASCALS So you can routinely grow diamonds. 142 00:16:11,700 --> 00:16:15,570 And that's actually a factory growing synthetic gemstones. 143 00:16:16,770 --> 00:16:22,530 So again, this is sort of a blight in that any venture capitalist says to you, Well, 144 00:16:22,560 --> 00:16:28,620 why would I bother investing in a material for 20 years to make quantum photonic devices 145 00:16:28,620 --> 00:16:34,470 or semiconductor devices when I can grow the diamond and then sell them as gemstones? 146 00:16:35,250 --> 00:16:44,230 Well, I'll say it is a nuisance. But beneath you have some pictures, historical pictures from China. 147 00:16:44,620 --> 00:16:54,910 Just showing one institute, the evolution of their so-called cubic high pressure, high temperature press over 20 years. 148 00:16:55,420 --> 00:16:59,770 And the one bottom right. And it's the same person. 149 00:16:59,770 --> 00:17:11,860 I've not just used a smaller person. This is a press with an internal capsule volume of about the size of a Coke can. 150 00:17:13,300 --> 00:17:26,140 This is an amazing technology. And there's a Russian company called New Diamond Technology who have taken this Chinese president, 151 00:17:26,140 --> 00:17:34,060 have re-engineered the capsule with a very secret bit. But last year, they announced that the succeeded in growing a 50 carat diamond. 152 00:17:34,630 --> 00:17:40,120 And speaking to them earlier this week, they say by the middle of the year, 153 00:17:40,120 --> 00:17:45,190 they should have a press release when they can go to golf ball size and synthetic diamonds. 154 00:17:47,170 --> 00:17:53,200 Structurally, they're amazing, as in the very low dislocation is very low internal strain, reasonable purity. 155 00:17:54,850 --> 00:18:00,190 And and, of course, this activity is going on worldwide. 156 00:18:00,370 --> 00:18:10,420 Top Left is a national project in Japan for which the senior researcher has won the emperor's medal. 157 00:18:11,140 --> 00:18:16,570 And it's a 5000 ton press built by Sumitomo Electric. 158 00:18:17,140 --> 00:18:23,360 And and they have cheated here they are, small students. And but it is absolutely huge. 159 00:18:23,690 --> 00:18:31,610 And it's two stories beneath where you're looking. So that's actually up on the gantry to load the samples. 160 00:18:32,510 --> 00:18:40,729 This has a volume which anybody who works in high pressures, it sounds very, very good, doesn't it? 161 00:18:40,730 --> 00:18:48,050 Sounds quite modest. We're talking about something that's two centimetres long and one and a half centimetres in diameter, 162 00:18:48,560 --> 00:18:55,520 and this press can generate 25 gigapascals and sustain 3000 degrees c. 163 00:18:56,410 --> 00:19:00,610 So this press has achieved, in a sense, one of the holy grails. 164 00:19:01,270 --> 00:19:11,900 They can take nano crystalline graphite and just squeeze heat and turn them into nano crystalline diamond ceramics. 165 00:19:12,610 --> 00:19:22,510 So this is diamond, but it's made up of nanoparticles. And these I've just taken as an example of the bottom left as opposed to the gemstone. 166 00:19:23,140 --> 00:19:26,890 The other is a ball pairing. 167 00:19:27,430 --> 00:19:31,270 But the others are anvils for high pressure, high temperature research. 168 00:19:31,960 --> 00:19:35,950 So these are not single crystal diamonds, so they don't cleave. 169 00:19:36,640 --> 00:19:38,980 So they're much tougher than a single crystal diamond. 170 00:19:39,340 --> 00:19:50,020 But I'm sure the future for large volume diamond anvil cells with these being the diamond anvil. 171 00:19:50,410 --> 00:20:00,190 And so rather than achieving pressures of sort of 50, 100 gigapascals on micron sized samples, 172 00:20:00,610 --> 00:20:07,080 it will soon be able to be done on millimetre and then even centimetre cubed size sample. 173 00:20:07,090 --> 00:20:13,540 So a whole revolution coming there and and cubic presses such as the one on the 174 00:20:13,540 --> 00:20:20,440 bottom right are used routinely to take natural diamonds that are brown in colour, 175 00:20:20,980 --> 00:20:25,800 heat them up under a stabilising pressure and turn them colourless. 176 00:20:26,990 --> 00:20:35,960 So you go for something that you can buy for about $10 a character, something even sell as a big diamond for 1000 to $10000 per carat as a gemstone. 177 00:20:36,680 --> 00:20:43,370 So, of course, a lot of the Gem Labs and DeBeers and I said it's a few billion. 178 00:20:44,390 --> 00:20:48,500 Is the market in dollars for synthetic diamond for industrial applications? 179 00:20:49,820 --> 00:20:58,730 In 2013, the gem market in the US was two and a half times the mobile phone market. 180 00:20:59,870 --> 00:21:09,290 It is ginormous still. So there is a big motivation and to be able to differentiate between natural and synthetic diamonds. 181 00:21:10,680 --> 00:21:14,820 And. Which are the natural diamonds on this picture? 182 00:21:18,180 --> 00:21:25,550 Which of the synthetic ones? Well, as I probably would say straight away, diamonds are not usually yellow. 183 00:21:25,940 --> 00:21:36,020 The ones in the middle are synthetic. They're yellow because they are nitrogen doped with a few tends to 100 ppm of nitrogen. 184 00:21:37,140 --> 00:21:44,190 The gemstones on the left are rough diamonds, and you can see some nice features that are natural. 185 00:21:44,610 --> 00:21:47,700 They've grown with this very octahedron morphology. 186 00:21:48,900 --> 00:21:53,430 The diamonds on the top right are synthetic. 187 00:21:54,720 --> 00:22:03,750 And the we're talking about demons here that have appeared to concentrations of maybe only tens of parts per billion impurities. 188 00:22:04,520 --> 00:22:17,490 And but they grow with this quote, octahedron morphology and the uptake of impurities is different in the different crystalline growth zones. 189 00:22:18,640 --> 00:22:25,900 So they're very easy to distinguish between natural and synthetic diamonds, even though they can be grown colourless. 190 00:22:26,710 --> 00:22:38,600 The big one is not quite to scale. It's only 17 millimetres across and that's a synthetic ten carat cushion cut 191 00:22:38,840 --> 00:22:45,710 diamond that is approaching semiconductor grade impurity that was grown last year. 192 00:22:46,040 --> 00:22:50,150 And this is from the company who say that they will hit some 50 and 100 carats. 193 00:22:50,270 --> 00:23:00,650 And this year, in terms of substrates for the electronics and materials, this is a real potential breakthrough. 194 00:23:01,580 --> 00:23:06,690 And now high pressure, high temperature growth is sort of exciting. 195 00:23:07,020 --> 00:23:11,600 Now, when these presses go wrong, there are very large explosions. 196 00:23:11,690 --> 00:23:16,430 They're very expensive. You are really pushing physics to the limits. 197 00:23:16,940 --> 00:23:21,380 The tungsten carbide anvils, a way beyond their yield strength. 198 00:23:22,370 --> 00:23:26,330 And the steel backing is often beyond its melting point. 199 00:23:27,980 --> 00:23:32,120 In terms of the pressure, the temperature conditions inside the press. 200 00:23:32,690 --> 00:23:37,040 So if the cooling fails momentarily, you have a big problem on these. 201 00:23:37,490 --> 00:23:39,200 So this is proper science. 202 00:23:40,670 --> 00:23:52,540 Now, CVD growth of diamond chemical vapour deposition, on the other hand, is sort of a little too clinical as in this is a semiconductor growth made, 203 00:23:52,550 --> 00:23:57,980 some technology pinched from the growth of other materials silicon, silicon carbide. 204 00:23:58,700 --> 00:24:03,950 And it's slightly challenging to do it with diamond. 205 00:24:04,160 --> 00:24:17,090 And there is one interesting step that you'd go back to and you'd say, well, CVD happening at some atmospheric pressures at temperatures of well, 206 00:24:17,570 --> 00:24:21,710 the substrate isn't melting and the temperature might be 800 degrees C, 207 00:24:22,640 --> 00:24:29,900 but 800 degrees C and as sub atmospheric pressure is certainly not the right side of the Berman Simon line to grow diamond. 208 00:24:30,770 --> 00:24:39,409 So kinetics wins out over thermodynamics here and the diamond is grown from a mixture of a carbon containing gas and hydrogen. 209 00:24:39,410 --> 00:24:49,580 And it's the hydrogen stabilises, the growing diamond surface and is such an aggressive action that nothing else survives except diamond. 210 00:24:50,570 --> 00:24:54,920 So you can grow single crystal diamond on single crystal diamond substrates. 211 00:24:55,250 --> 00:25:00,680 There's work grain, single crystal diamond or really mosaics to be truthful on substrates like iridium, 212 00:25:01,190 --> 00:25:07,310 but large polycrystalline diamond wafers can be grown and the process is one 213 00:25:08,210 --> 00:25:14,900 where you have a hydrogen terminated surface atomic hydrogen comes in abstracts, 214 00:25:14,900 --> 00:25:19,100 the hydrogen from the surface creates a radical site, and at the frontier, 215 00:25:19,430 --> 00:25:25,490 a carbon radical comes in and bonds and the diamond is grown layer by layer by layer. 216 00:25:26,660 --> 00:25:33,650 The growth rates can be very high. You can approach, uh, 50 microns per hour. 217 00:25:34,850 --> 00:25:40,280 So just think about how many atomic layers are coming down. And of course you've got a very scalable process. 218 00:25:40,910 --> 00:25:45,710 So all sorts of diamond metals can be produced by this route. 219 00:25:46,160 --> 00:25:53,780 The top left is an atlas that is sold by Bruker and other manufacturers inside the FDR machines. 220 00:25:54,350 --> 00:25:58,549 So the diamond optics are now used routinely for FDR and the metal. 221 00:25:58,550 --> 00:26:08,240 You've got some diamond discs. The big piece of diamond is 150 millimetres across and four millimetres thick polycrystalline diamond. 222 00:26:08,570 --> 00:26:14,690 It's a Jared from window so that can handle ten kilowatts to get the fusion reaction going and won't let the tritium out. 223 00:26:15,740 --> 00:26:24,380 And if you like your music, this up here is a diamond tweeter sold by Bowers. 224 00:26:24,470 --> 00:26:28,360 Wilkins won the Queen's Award for Innovation. 225 00:26:30,110 --> 00:26:42,550 Firstly, on academic salaries at Warwick. At £5,000 a speaker, they're a little too expensive for me, but apparently they sound wonderful. 226 00:26:42,780 --> 00:26:47,990 I was just using the stiffness of diamond and bottom. 227 00:26:48,260 --> 00:26:56,990 Here is a diamond that has been etched to produce a moth II, a photonic structure on the surface. 228 00:26:57,560 --> 00:27:01,700 So this doesn't need an anti reflection coating. 229 00:27:01,700 --> 00:27:11,270 It's built in out of the diamond. So this is one of the infrared windows that can handle many kilowatts of power at ten microns. 230 00:27:11,870 --> 00:27:16,490 So a technology developed just down the road by element six on the Harwell campus. 231 00:27:17,450 --> 00:27:25,519 And this little device here, the one that we call the barcode, if I could just get the mouse to work so I can see the mouse. 232 00:27:25,520 --> 00:27:27,230 You can't. The one that looks like a barcode, 233 00:27:27,890 --> 00:27:35,660 that's actually a piece of polycrystalline intrinsic diamond in which we laser machined trenches overgrown 234 00:27:35,690 --> 00:27:43,129 with boron doped diamond and then polished back to ring veil the visually addressable electrodes. 235 00:27:43,130 --> 00:27:47,570 And above it you can see a structure that has got three different band electrodes. 236 00:27:48,140 --> 00:27:56,000 So my colleague Julie MacPherson at Warwick is very much using that for analytical science 237 00:27:56,930 --> 00:28:02,620 and it looks like there's a good chance it will go on the next Mars mission as well. 238 00:28:02,640 --> 00:28:14,870 The analytical tools for looking for organic material and heavy metals in Martian soil and the electrode to the left. 239 00:28:15,680 --> 00:28:19,100 The writing is not pure vanity that we put it there. 240 00:28:19,940 --> 00:28:26,899 We laser machine the writing at a shallow depth so that when the technician polishing 241 00:28:26,900 --> 00:28:31,490 away that boron doped overgrowth knows that when the writing starts to disappear, 242 00:28:31,490 --> 00:28:35,840 he's perfect on the electrode. So it's there as a marker. 243 00:28:36,770 --> 00:28:41,030 But I put, of course, this fellow down here in the bottom left. 244 00:28:41,960 --> 00:28:50,030 A lot of the commercial activity is predicated on growing gem diamonds for gem applications. 245 00:28:50,690 --> 00:28:59,330 And as a rule of a pretty good estimate, I think it's still less than 1% of the gem market is synthetic diamond, 246 00:28:59,690 --> 00:29:05,599 but people are buying synthetic diamonds and all of the reputable Gem Labs certificate, 247 00:29:05,600 --> 00:29:09,470 the stone will be able to tell you whether it's natural or synthetic. 248 00:29:10,040 --> 00:29:14,810 And looking at the websites such as pure grown diamonds, you can go and look for yourself. 249 00:29:15,620 --> 00:29:25,460 The synthetics are selling for between a 50 and a 20% discount compared to naturals, but buy them as in there they are available if you want them. 250 00:29:26,540 --> 00:29:39,230 So I'm just going to spend a few minutes talking about some of the research that has been enabled for us by the ability to grow. 251 00:29:39,740 --> 00:29:43,730 Diamond But now, of course, we don't just want to grow it. 252 00:29:43,790 --> 00:29:50,540 We want to be able to control and tailor the properties such that it's useful for us. 253 00:29:51,080 --> 00:29:57,260 So growth is still an emerging technology to do it as good as we would like. 254 00:29:57,740 --> 00:30:07,820 But certainly processing and utilising doping and impurities defects in Diamond is still very much an emerging field. 255 00:30:08,950 --> 00:30:12,519 So I chose to put this in because it was filled. 256 00:30:12,520 --> 00:30:18,850 Clip Stein and Bell Hayes at Oxford who got me really interested in this. 257 00:30:20,510 --> 00:30:28,250 So this is a copy of a Clarendon design for a unique axial stress cell that fits in an Oxford instrument Christ hat. 258 00:30:29,600 --> 00:30:34,340 But at the bottom and in the picture, you can see we've got some diamond anvils. 259 00:30:34,770 --> 00:30:42,530 Yeah. And these are nano polycrystalline diamond angles and we can apply to our sample of interest. 260 00:30:43,310 --> 00:30:49,890 Six Gigapascals of uni axial stress. And to actually macroscopic and quite large samples. 261 00:30:50,490 --> 00:31:03,629 Mm. To a couple of. Mm. Keep that sample is sitting inside a loop gap resonator and this comes back to the jar from the magnetron. 262 00:31:03,630 --> 00:31:11,130 So you can see in the display case outside rather than using a cavity we've used a structure 263 00:31:11,130 --> 00:31:17,700 that is much smaller than the microwave wavelength which is made up of loops and gaps. 264 00:31:17,880 --> 00:31:26,430 The gaps are capacitors, the loops are inductors. So there's a whole range of microwave resonant structures you can produce for doing 265 00:31:26,430 --> 00:31:34,860 spectroscopy from 1 to 100 gigahertz that have dimensions of millimetres to tens of microns. 266 00:31:35,770 --> 00:31:44,410 So they're brilliant for high pressure work where you want to have a small sample so you can generate large pressures, 267 00:31:44,770 --> 00:31:47,799 but you want to have very good sensitivity. 268 00:31:47,800 --> 00:31:52,330 So you don't want a large cavity with the energy density spread out over the cavity. 269 00:31:52,780 --> 00:31:56,260 You want a small resonator structure. 270 00:31:57,280 --> 00:32:01,690 And these are made out of heavy machinery, all ceramic and just silver plated. 271 00:32:02,800 --> 00:32:10,520 The quality factor of the resonator is less than that of a cavity, probably by a factor of ten. 272 00:32:10,540 --> 00:32:14,960 Typically. So we're talking about queues of 1000 rather than 10,000. 273 00:32:15,470 --> 00:32:23,360 But the filling factor ETA I as a rule of thumb, how many lines of the microwave magnetic field you've generated go through? 274 00:32:23,360 --> 00:32:29,420 The sample is between one and two orders of magnitude higher than for a cavity. 275 00:32:29,930 --> 00:32:35,330 So you're talking for a small sample, something that gives you an order of magnitude extra sensitivity. 276 00:32:36,020 --> 00:32:45,740 But you can do experiments at very high pressures and low or high temperatures, and you've got the possibility of optical excitation. 277 00:32:47,240 --> 00:32:52,280 So one of the simplest defects in diamond is the substitution of nitrogen. 278 00:32:53,330 --> 00:32:57,650 Donor. Nitrogen is next to carbon in the periodic table. 279 00:32:58,040 --> 00:33:02,940 It's about the same size, if any chemist. 280 00:33:02,960 --> 00:33:12,470 Please stop listening for a second. You can treat nitrogen as carbon with one extra electron just a bit heavier. 281 00:33:13,940 --> 00:33:17,300 So it'll bond into the diamond structure. 282 00:33:17,420 --> 00:33:26,030 And we all know from our semiconductor physics that we could treat it as a nitrogen plus and an electron in a hydrogen type orbital. 283 00:33:26,030 --> 00:33:31,310 And this is going to give us a shallow DNA, just like phosphorus in silicon. 284 00:33:33,110 --> 00:33:39,830 But it doesn't. It gives us a donor where the donor activation energy is nearly two electron volts. 285 00:33:40,700 --> 00:33:44,120 Diamond is the most incompressible material. 286 00:33:45,590 --> 00:33:52,340 But the nitrogen likes to be three fold coordinate as if it were bonded in ammonia with a lone pair. 287 00:33:53,390 --> 00:34:00,690 So it actually relaxes and in one direction between the nitrogen one of its carbon neighbours. 288 00:34:00,710 --> 00:34:04,040 That bond extends by 25%. 289 00:34:04,790 --> 00:34:10,940 The most incompressible material and quantum quantum mechanics makes the bond extend by a huge amount. 290 00:34:11,360 --> 00:34:19,670 And this drops the energy of the down electron to a level where it's absolutely, utterly useless for electronics. 291 00:34:20,420 --> 00:34:26,590 Yeah. The shallowest end diamond we have in diamond is about .6.7 heavy, 292 00:34:27,050 --> 00:34:32,180 at which point any semiconductor device energy engineer just starts laughing and leaves. 293 00:34:33,380 --> 00:34:36,770 It is not gaming electronic material in the sense that silicon is. 294 00:34:38,120 --> 00:34:47,770 But of course this extra electron has gone into the antibody orbital between a knife from one of its carbon neighbours and it can choose, 295 00:34:47,780 --> 00:34:52,620 it can go into this one, this one, this one or that one. 296 00:34:52,620 --> 00:35:06,160 I can't do both at the same time. I apologise. And actually we can perturb which one it chooses to go into by applying a large stress to the sample. 297 00:35:06,640 --> 00:35:17,620 So if we apply the stress along a11 direction for two of the possible sites which stress is coming down from the roof, which are these two? 298 00:35:18,310 --> 00:35:22,000 There's a component of stress along the extended bond direction. 299 00:35:23,020 --> 00:35:26,950 Yeah. The other two are actually lying flat in this plane. 300 00:35:26,950 --> 00:35:37,180 And there's no component of stress along the. So we've separated them out with stress that two of the sides see compression and the other two don't. 301 00:35:38,180 --> 00:35:44,030 If we put magnetic fields, do some magnetic resonance along a direction perpendicular to the stress, 302 00:35:44,420 --> 00:35:50,210 then we can separate out sites one and two from three and four, one and two. 303 00:35:50,600 --> 00:35:57,020 See a component of stress along the extended nitrogen bond axis three and four don't. 304 00:35:58,720 --> 00:36:07,690 So here we show an example of an EPR spectrum I recorded as the first derivative from this substitution like life donor, 305 00:36:09,180 --> 00:36:13,570 a single electron coupled to a nitrogen nucleus which has nuclear spin one. 306 00:36:13,930 --> 00:36:21,020 So it splits the spectrum into three lines. And then remember that we have differently oriented sites. 307 00:36:21,020 --> 00:36:27,940 So the outer lines are split into those from sites one and two and those from sites three and four. 308 00:36:28,810 --> 00:36:34,180 And if you look at the outer two lines, there's two sites, three and four, two sites, one and two. 309 00:36:34,180 --> 00:36:38,080 Out of the intensity that should make for the middle line is four. 310 00:36:38,470 --> 00:36:44,650 Where am I is equal to nought. There's no high profile splitting on that line and that's all four sites contributing in the same place. 311 00:36:44,650 --> 00:36:55,330 In the spectrum we apply a stress of only one gigapascals and we can see that the EPR transition from sites one and two gets smaller. 312 00:36:55,780 --> 00:36:59,859 As the defect says. I don't like this squash very much. 313 00:36:59,860 --> 00:37:06,400 I'm going to rotate away. I'm going to tunnel into a different orientation where I have lower energy. 314 00:37:07,180 --> 00:37:13,360 So it's a straightforward problem. We have a configuration coordinate to equal potential wells, if you like. 315 00:37:13,660 --> 00:37:22,390 We apply the stress, we make one higher energy and the defects orientate themselves in lower energy configuration. 316 00:37:23,260 --> 00:37:29,770 You take the stress off and they will gradually re-orientate at 200 K, 317 00:37:29,770 --> 00:37:39,370 we're talking about 3000 seconds for them to re-orientate back to the random equilibrium orientation at room temperature every 5 seconds. 318 00:37:39,850 --> 00:37:45,549 This defect is reorientate to a different configuration, which is quite remarkable. 319 00:37:45,550 --> 00:37:55,540 In a stiff material like Diamond, it was proposed that well, the question was raised as in for quantum technologies, 320 00:37:55,720 --> 00:38:01,629 Diamond is very useful because it's got a very high debye temperature, spin, lattice relaxation. 321 00:38:01,630 --> 00:38:05,860 Times are very long. Where does the spin lattice relaxation come from? 322 00:38:06,550 --> 00:38:14,170 So if it were a direct process, so we absorb a microwave transition, how does the electron get back to the ground state? 323 00:38:14,740 --> 00:38:17,920 It can do it by emitting a funnel and come back to the ground state. 324 00:38:18,490 --> 00:38:26,860 It could be a ROM and process where we have a virtual level, but the same sort of idea, photons in, photons out or it could be even. 325 00:38:26,860 --> 00:38:38,499 And this is what was proposed to this defect. Non spin conserving reorientation site three has been perturbed by some internal strain such as the 326 00:38:38,500 --> 00:38:44,530 defect re-orientate and the electron tunnels between different levels and can change spin states. 327 00:38:44,530 --> 00:38:50,530 And that's a mechanism for spin lattice relaxation. So that's what we went after trying to prove. 328 00:38:51,790 --> 00:38:56,980 And we did it with a straight forward saturation recovery experiment to measure t one. 329 00:38:57,340 --> 00:39:04,090 I've just put that up to show you the quality of the data is very good and we can measure the recovery time. 330 00:39:05,190 --> 00:39:09,210 And I won't dwell on this too long because it was an experiment. 331 00:39:09,220 --> 00:39:19,020 It was a complete and utter disaster because stress had absolutely no effect on the reorientation of the t one of this defect. 332 00:39:19,320 --> 00:39:24,460 And that's because the reorientation rate is much slower than the relaxation rate. 333 00:39:24,900 --> 00:39:34,980 So what was in the literature was incorrect. And the speed of relaxation is not determined by reorientation. 334 00:39:36,550 --> 00:39:40,060 But then we carried on because the student just started and was upset. 335 00:39:40,270 --> 00:39:44,230 So we decided that we would measure the spin echo decay. 336 00:39:44,590 --> 00:39:49,060 So as well as we are looking at the recovery of the equilibrium magnetisation. 337 00:39:49,450 --> 00:39:59,170 We look to see whether or not if we tilted the spins and then let them evolve in the X-Y plane for the one way, two poles and reflect them. 338 00:40:00,010 --> 00:40:05,860 Look at the echo signal. This is determined by spin, spin, relaxation. 339 00:40:06,610 --> 00:40:11,020 So we measured that people are interested in diamond because the spin, spin, 340 00:40:11,230 --> 00:40:19,930 relaxation times are what are going to limit any quantum technology type applications, whether it's sensing or even computing. 341 00:40:20,680 --> 00:40:22,630 And in these diamonds, 342 00:40:24,100 --> 00:40:31,510 the t twos are or I should say the phase memory times are quite short because we're working with high concentrations of defects. 343 00:40:33,470 --> 00:40:39,330 But I just want to emphasise a point. When you make this measurement, you're not just measuring the intrinsic to. 344 00:40:40,220 --> 00:40:46,490 You're actually measuring the phase memory time because when you do these pulses in the experiment, 345 00:40:47,300 --> 00:40:55,160 I might be spent over here that you're monitoring if my pulse flips another spin over here and it 346 00:40:55,160 --> 00:41:01,640 changes spin state the magnetic field that it's producing that I see has changed so effectively. 347 00:41:02,000 --> 00:41:06,740 My resonance frequency changes. It's like my t to time has changed. 348 00:41:07,280 --> 00:41:10,820 So this is dependent on the concentration of the defect. 349 00:41:11,570 --> 00:41:11,959 Truly, 350 00:41:11,960 --> 00:41:18,890 we have to call this the phase of memory time because it depends on the dipolar coupling between different defects and whether or not we flip them. 351 00:41:19,850 --> 00:41:26,720 I'll skip that slide, but just show you that the face memory times do depend on stress, 352 00:41:27,410 --> 00:41:34,940 that actually we can make the face memory times the effective to longer for some of the sites. 353 00:41:35,780 --> 00:41:39,500 And the explanation is really quite simple. 354 00:41:40,400 --> 00:41:48,890 If you have two spins that flip flop at the same energy, that process will happen with very high probability. 355 00:41:49,720 --> 00:41:55,480 But if you've applied a stress such as the one along the direction, the stress, 356 00:41:56,050 --> 00:42:02,470 the probability now of me having friends in my vicinity that are orientated the same way has dropped. 357 00:42:03,750 --> 00:42:09,960 So the probability of the flip flop reaction to relax has been switched off. 358 00:42:10,800 --> 00:42:14,610 So my phase memory time should be longer. 359 00:42:15,420 --> 00:42:17,370 But if I'm a defect oriented parent, 360 00:42:17,370 --> 00:42:23,670 if the stress and my number of neighbours that are perpendicular to the stress have increased because I have applied the stress, 361 00:42:23,970 --> 00:42:28,080 the phase memory time should decrease and that's exactly what happens. 362 00:42:28,530 --> 00:42:36,360 But this just shows a way of being able to control the relaxation properties by applying universal stress. 363 00:42:36,750 --> 00:42:42,540 And you can in principle, grow in stress by using isotope heterostructures to change the properties. 364 00:42:44,880 --> 00:42:54,690 Just another quick example. In the last 5 minutes or so, I've picked a very simple defect, the interstitial defect in Diamond. 365 00:42:55,110 --> 00:42:58,710 So we've forced two attempts to go on to the latter of. 366 00:42:59,700 --> 00:43:06,020 This defect is called are. It was first seen at the University of Reading hence ah, 367 00:43:06,560 --> 00:43:15,709 but it was John Owen in Oxford who actually studied this and published the first really significant paper in nature, 368 00:43:15,710 --> 00:43:20,870 suggesting that this in fact was the isolated interstitial in diamond. 369 00:43:21,290 --> 00:43:30,190 That was not proved until the work led by Michael Baker in the 1990s and is now actually under pinned a 370 00:43:30,200 --> 00:43:36,170 lot of the understanding of interstitial and interstitial defect reactions in three or five materials. 371 00:43:38,080 --> 00:43:43,590 But you can see that this defect has an effect of electron spin of one. 372 00:43:43,600 --> 00:43:52,420 It comes from an excited state, lots of nice properties, but let's just think about it very simply as if we force two atoms on a lattice site. 373 00:43:53,650 --> 00:43:58,720 So it can be oriented along. Hour, one one hour. 374 00:43:59,020 --> 00:44:02,470 I want I along the three key directions. 375 00:44:03,320 --> 00:44:06,860 And again, as we look at the EPR transitions from this defect, 376 00:44:07,220 --> 00:44:15,510 we can identify lines one and four on the diagram come from the defect that is pointing along one lines. 377 00:44:15,530 --> 00:44:19,640 Two and three in a spectrum come from the defects that are lying along one out. 378 00:44:19,700 --> 00:44:33,920 Or I want to. So stress is a really useful probe of the different orientations of these defects and even in a processing and processing. 379 00:44:37,340 --> 00:44:41,900 If you want prices dimmers to control diffusion and interstitial diffusion is the dominant mechanism. 380 00:44:42,260 --> 00:44:47,329 You can control the trajectory in the rate of diffusion by applying a stress to stop this defect, 381 00:44:47,330 --> 00:44:50,660 being able to rotate between the different orientations. 382 00:44:51,620 --> 00:44:57,860 So, again, a high pressure cell and this now is in Japan at the Japanese Atomic Energy Authority. 383 00:44:58,250 --> 00:45:07,610 Underneath an electron beam to do the irradiation, to damage the diamond, to create the interstitial defect while applying a large uni axial stress. 384 00:45:08,480 --> 00:45:12,680 And here's a summary of the results of different stresses. 385 00:45:13,130 --> 00:45:18,150 Did we get any preferential orientation? Well, finally we did that. 386 00:45:18,170 --> 00:45:27,380 Three Gigapascals you have a spectrum with the magnetic field oriented along either this direction which saw the stress or perpendicular to it, 387 00:45:27,920 --> 00:45:32,570 and then take the difference in the spectrum. And you'll see that there's a huge difference. 388 00:45:33,320 --> 00:45:38,639 It hasn't worked very well. Rather than a probability of a third along this direction. 389 00:45:38,640 --> 00:45:44,760 A third along that direction, a third on that direction. So, in other words, a third parallel, two thirds perpendicular. 390 00:45:45,180 --> 00:45:50,220 We've got a dramatic change of .27 parallel, 2.73. 391 00:45:50,790 --> 00:45:54,180 But this actually tells a lot during the irradiation. 392 00:45:54,510 --> 00:46:04,169 There's actually so much electronic excitation that the stress we've applied is insignificant to the actual dynamics of this defect, 393 00:46:04,170 --> 00:46:07,230 being able to rotate and migrate during the experiment. 394 00:46:08,340 --> 00:46:12,750 So what we did instead is created these defects by irradiation. 395 00:46:13,500 --> 00:46:17,010 And then this is very much a Heath Robinson experiment. 396 00:46:17,850 --> 00:46:22,290 You've got a big cooling stage at the back and a little laser, 397 00:46:22,380 --> 00:46:31,500 which the students refer to as a death ray on top 914 nanometres less than £1,000.42 watts of output power. 398 00:46:33,390 --> 00:46:41,730 So this can be centred on a fibre focus on a lens and diamonds do not like that much power in 10 milliseconds. 399 00:46:42,240 --> 00:46:47,770 You can set them on fire. How are we to demonstrate the health and safety? 400 00:46:47,790 --> 00:46:52,740 We put a brick in the way and you drill a hole through the the brick very quickly. 401 00:46:53,670 --> 00:47:01,560 So the laser enclosure has to have thicker aluminium plates than anything else, because if you get it wrong, you can melt through the aluminium. 402 00:47:02,070 --> 00:47:08,490 But we can nail the diamonds very quickly and very controlled temperatures using optical heating 403 00:47:08,700 --> 00:47:16,780 while the diamond is subjected to a unique axial stress and to experimental spectrum up above. 404 00:47:16,800 --> 00:47:24,960 Now you can say that very different. I won't dwell on this, but the key thing is that as we apply greater and greater stress, 405 00:47:25,560 --> 00:47:32,430 we can actually get to a point where we are over 90% of the defects oriented, perpendicular to the stress. 406 00:47:32,880 --> 00:47:36,450 Now the stress makes a big, big effect. 407 00:47:36,960 --> 00:47:43,410 Yeah, we can actually start to study the dynamics of the reorientation of this defect. 408 00:47:44,130 --> 00:47:51,870 So here's a sample where the defects were preferentially oriented by annealing them under a unique axial stress 409 00:47:52,590 --> 00:47:59,010 and then enabled very gently while doing the spectroscopy to monitor the recovery to the equilibrium orientation. 410 00:48:00,420 --> 00:48:08,250 So this is not studying the growth diffusion, which we've been doing for many, many years as we see a defect. 411 00:48:08,790 --> 00:48:14,820 The defect disappears. We have to make a whole range of assumptions about what processes are important. 412 00:48:14,970 --> 00:48:22,650 Is it the step by step diffusion process? Is it a recombination event at the end that's got a huge barrier that determines the process? 413 00:48:23,040 --> 00:48:26,190 We're doing none of that here because we're not losing the defect. 414 00:48:26,580 --> 00:48:37,670 We are looking at the defect reorienting. So we actually can extract an activation energy for this defect, changing its local configuration. 415 00:48:38,180 --> 00:48:41,720 And then you can go to high temperature and actually look at the loss of the defect as well. 416 00:48:42,020 --> 00:48:47,000 So you can break down the different processes in the different steps in the diffusion. 417 00:48:48,640 --> 00:48:52,310 So I'm watching the clock. Yeah. 418 00:48:52,450 --> 00:48:59,799 2 minutes. Good. So using stress with a whole range of spectroscopy gives us a whole range of 419 00:48:59,800 --> 00:49:06,550 different things we can do to actually control the defects that are in the diamond. 420 00:49:07,300 --> 00:49:13,300 But I can't come and give it all without talking about the next negatively charged night and Vegas centre, 421 00:49:13,360 --> 00:49:26,410 which I'll just spend a couple of minutes on at the end. And there are more papers per year published in Nature and Science on this defect alone, 422 00:49:27,190 --> 00:49:33,349 and this is for the last five years than there are on graphene. Absolute explosion. 423 00:49:33,350 --> 00:49:39,560 As in, since I started this lecture, three more papers have been published on or utilising this defect. 424 00:49:41,010 --> 00:49:47,610 And that is because. Yeah. And the entry V for it, I'll just touch on very briefly right at the end. 425 00:49:47,880 --> 00:49:52,890 But you can see it's like a sister, both trigger on symmetry. 426 00:49:53,190 --> 00:49:57,750 It's a vacancy surrounded by one nitrogen or a vacancy surrounded by three nations. 427 00:49:59,010 --> 00:50:01,920 So envy. What is so great about it? 428 00:50:03,180 --> 00:50:16,740 And to do this very quickly, it has a luminescence transition in the visible at 67 nanometres between an excited state and a ground state. 429 00:50:17,310 --> 00:50:25,410 And the intensity of that luminescence depends on which spin state the defect is in. 430 00:50:25,920 --> 00:50:31,290 If it's in the Mexico's Norte State as Mexico's one grand state, then it is bright. 431 00:50:32,220 --> 00:50:35,290 If you can put it into the Mexico's plus or minus one state. 432 00:50:35,700 --> 00:50:46,170 It is about 30% darker. So you can actually read that the state and Spain is in by monitoring the luminescence and the visible. 433 00:50:46,860 --> 00:50:52,500 Now, of course, the luminescence is visible. You can do the detector similar to that in your mobile phone, just a bit more expensive. 434 00:50:53,130 --> 00:51:00,690 And you can get two single photon counting type sensitivities so you can detect one photon being emitted from this defect. 435 00:51:01,780 --> 00:51:05,790 Now, if the intensity is the number of photons emitted depends on the spin state, 436 00:51:06,340 --> 00:51:11,889 then you can drive this EPR transition and you can change the population in the 437 00:51:11,890 --> 00:51:19,360 bright state and read out the spin state by monitoring the fluorescent intensity. 438 00:51:20,050 --> 00:51:27,610 So that's exactly what's done in the top, right? And colleagues, Jason Smith and others, we're particularly proud of this. 439 00:51:27,610 --> 00:51:31,060 This was sort of came to fruition in 2009. 440 00:51:31,450 --> 00:51:39,010 And this week we've had first year graduate students in the lab showing me the correlation 441 00:51:39,280 --> 00:51:45,220 spectroscopy that they can measure a single colour centre because it's the photon statistics. 442 00:51:45,670 --> 00:51:50,290 You can't have two photons at the same time and in the same practical they showed 443 00:51:50,290 --> 00:51:54,249 that they can manipulate the electron in this one defect and the single centre. 444 00:51:54,250 --> 00:52:02,650 Obama So in the space of seven years, it's come from nature to a graduate and afternoon experiment. 445 00:52:03,640 --> 00:52:07,420 And this can be done at room temperature because of the properties of diamond. 446 00:52:07,540 --> 00:52:13,660 So this trace of here as we sweep the microwave frequency is actually showing room temperature 447 00:52:14,380 --> 00:52:18,820 data looking at the fluorescence of a single defect so we can readout the spin state. 448 00:52:19,510 --> 00:52:25,720 So quite simply put, if you apply a magnetic field, you get two transitions rather than one. 449 00:52:26,050 --> 00:52:30,790 The separation between those two transitions tells you the magnetic field so you can read out the field. 450 00:52:31,870 --> 00:52:40,210 This is an experiment done by Ronald Walsworth and colleagues at Harvard, and I picked it just because it's such a nice example. 451 00:52:40,660 --> 00:52:43,270 So you have a plate, a diamond with these energy centres in it. 452 00:52:44,050 --> 00:52:51,720 Sitting on top of the plate are these magneto tactic bacteria that navigate in the sludge by having little nano magnets inside. 453 00:52:51,730 --> 00:53:01,070 And so you can tell which way is up. And using the envy centre as an atomic sized magnetometer. 454 00:53:01,550 --> 00:53:16,850 The magnetic field was measured for individual bacteria and you could do the field profile and then the battery was put into an atom and killed, 455 00:53:17,030 --> 00:53:24,710 unfortunately. And then the magnetic field was then calculated from the picture of where the magnetic nanoparticles were. 456 00:53:25,640 --> 00:53:29,870 So there's a whole range of different optical. 457 00:53:33,080 --> 00:53:36,770 Magnetometers, base techniques that are based on the notion of the centre. 458 00:53:37,730 --> 00:53:45,380 And I said that I was just going to mention the entry defect, and I've done this for a bit of fun in the last 30 seconds. 459 00:53:46,010 --> 00:53:54,380 Here is the spectrum from the 1970s. This is what gets an EPR spectroscopy such as myself excited, lots and lots of lines. 460 00:53:56,330 --> 00:54:02,180 And if you look at the black spectra at the top, this is what was published in terms of an experiment on the left and the theory on the right. 461 00:54:02,540 --> 00:54:06,020 And it looked right. Yeah, everybody was happy. 462 00:54:06,290 --> 00:54:08,089 All the lines in the right place. 463 00:54:08,090 --> 00:54:14,719 We understood everything about this, but if we put the magnetic field in another direction of the high centre direction, it didn't work at all. 464 00:54:14,720 --> 00:54:20,270 But we didn't put that in the paper. We didn't show anybody that because the model wasn't good enough. 465 00:54:20,930 --> 00:54:28,400 But now, with modern synthesis technology rather than ground with 1914, which has got a nuclear speed of one, you can date with 1915. 466 00:54:28,880 --> 00:54:33,590 So this reduces the number of transitions in the spectrum from 729 to 8. 467 00:54:34,890 --> 00:54:40,320 Yeah. Towards the magnitude? Definitely. Good. The EPR spectrum is then very simple. 468 00:54:40,320 --> 00:54:46,590 You can fit it perfectly for 1915. When you go back to 1940 and you've only got one unknown parameter, 469 00:54:46,590 --> 00:54:53,940 the quadrupole interaction and for an arbitrary direction tada, you can simulate it. 470 00:54:54,980 --> 00:55:01,790 Now I've put that up because in 98% of natural diamonds, this defect is prevalent. 471 00:55:02,000 --> 00:55:06,710 And this is the first thing that Gem Labs will use to tell you whether or not this is a natural diamond. 472 00:55:07,190 --> 00:55:11,700 So actually, in terms of impact, this is important to. 473 00:55:14,130 --> 00:55:19,050 But you look at this defence structure and I won't go through this and labour the point, 474 00:55:19,050 --> 00:55:27,000 but actually it's three nice and long paths pointing in to a vacancy with an unpaid electron on a carbon radical. 475 00:55:27,450 --> 00:55:33,120 The group theory is actually quite simple. You've only got three possible states and they all have to be spin a half states. 476 00:55:33,960 --> 00:55:41,760 So there is absolutely no chance with this defect of doing all the clever tricks that you can do with the night and bangs, 477 00:55:41,760 --> 00:55:48,540 of the effect of shining light and getting 100% optical polarisation to enable room temperature readout in a single spin. 478 00:55:48,540 --> 00:55:51,210 No chance of doing that whatsoever. 479 00:55:51,930 --> 00:55:59,760 But of course, when you shine light on the top of the spectrum in the dark and the bottom is a spectrum under light, which is now spin polarised. 480 00:56:02,000 --> 00:56:05,100 So although it's theoretically impossible, it works. Yeah. 481 00:56:05,840 --> 00:56:15,380 And it means that the we believe and this is research in progress that the Coulson and carefully another Oxford model for modelling these defect 482 00:56:15,390 --> 00:56:23,090 structures in terms of the dangling orbitals the molecular orbital approach that's what everything else we have in diamond doesn't work for this. 483 00:56:24,080 --> 00:56:31,670 This is probably actually a defect that can sit in the positive charge state with a band electron in hydrogen IC type orbitals. 484 00:56:32,270 --> 00:56:41,420 That gives you a whole set of extra defect states that can be high spin that can then give rise to optical spin polarisation. 485 00:56:42,420 --> 00:56:51,329 And this might be right. It might be wrong, let's be honest. But it is exciting in that if you have the nice legacy defects which your qubits 486 00:56:51,330 --> 00:56:55,410 which are really useful and you want to be able to change the coupling between them, 487 00:56:55,890 --> 00:57:04,320 you have the entry of defect site that and now it has a wave function that extends just like a hydrogen tank. 488 00:57:04,320 --> 00:57:07,650 Orbital can talk to the defects in this facility. 489 00:57:08,130 --> 00:57:10,860 They excited and switch that interaction off. 490 00:57:11,370 --> 00:57:20,640 So you might have a quantum link here where you can control the interaction between distant nitrogen and vacancy defects. 491 00:57:21,090 --> 00:57:25,560 And this is I stand in front of you and say this is quantum technology. 492 00:57:25,860 --> 00:57:29,670 It's not spin physics that people were doing in the Clarendon 50 years ago. 493 00:57:31,020 --> 00:57:31,890 Thank you for your attention.