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Master class II with Bart van Wees

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Erkannte Entitäten
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I think we should continue soul and where where of so what you see from this picture you see that the spacing between the sample of this pop concerts of the end for the low energy is bigger as it either said the reason is headed particles always more we say there with a small the Toussaint velocity so the Lorentz force and which is actually elected charge times the velocity times in magnetic fields is always the same but if you see this day if you remember those calls that in momentum space they have to make if you go toward the 0 energy they have to make smaller and smaller groups in momentum space so that so so that the sense of moral support the state the PTT and they have to make small in order to make a elope you need less momentum they're going to make a move that the frequency will increase and increased energy becomes an issue quantise it's then you could these contests levels long low levels where you clearly see that the spacing is not called is the biggest basic you also see that now we get along well level at 0 and said this ship you can understand as the addition all of this makes the face sector of buying you go this Barry phase behavior of this so spin variable so if you look at it again now if you this season is in the center now again if you go toward the edge you see that this year long low-level actually well they makes native to love the levels that because 1 of them goes up this is the election body and the other 1 goes down as is the whole parts so that the juicy also something like this and I think this is quite fit you Busey that also the high along the levels they and does anybody has an idea what is going I should mention that he definitely genocea so that unity is 4th year because we have to Spain's 1 up 1 down right that it's always so I mean it's just factors too and we have to rally came came prior to the generators for With the nevertheless see that is global go toward the edge and that that that that this this number level is going to Split soul so if as anybody in idea why this somehow these elections are feeling the property of the edge and I cannot say
too much about it but just to show you the show you the edge structure African colonies Co
I'm just going to put this in this this is it this is because of the problems as to which of course this is 1 typical NH Shostakovich's called
armchair because you have a nice chat here you have a nice said he and the other 1 obviously would be it's and future nicely you have theatrical on the the use of new get in its structure which is exec and sense of course these these clearly selectors outpost awards the edge and when they went there for a code to perform the skipping or its they're also going to feel at the boundary condition which is put on by DH In this case 11 years the boundary
condition is such that there will be a difference between the election indicate indicate Prime so you could say Well that's interesting physics that you can't you can still use the the edges in most cases however it's a nuisance because you cannot control the edges how do you generally want to make a nice piece of graffiti and want to be sure that cigarette ads or it is armchair charity it's pretty difficult so you have no control very we since it uses it's a very little control about about this spitting on the other hand it's usually much smaller than the splitting so you do not really care about can you now say something for if you look at it about the behavior of disqualification single-layer well if your goal is to affirm energy goes from here to here you exceed 1 let you you basically cross 1 model of normal levels it's 4 times the generous To this 40 squared which is still the standard step but this guy the basic duties if it is on display at the pier so he began as usual at this so that is still as so you can also understand head this anomalous behavior of the quantum Hall effect in single layer graffiti with his picture Sonata was a clever question some gives you that demanded that he should also say something about what happened in double-layer images maybe the same thing happens in a Double-A sold that's not to a double layer Oguendo before we turn to double that just made mention this 1 so this is the long level sequence in single layer coughing this is the 0 energy we have a very because of the big energy spacing between the 1st but this year along the level and the 1st long level so if you express this in terms of temperature on Calvin you get something like this and this is interesting because it tell you if you have a field of only 1 Tesla which is not a big fan disk typical spacing is already corresponds to a temperature of foreigners 20 Gulf which means that you can actually observed the quantum Hall effect even at room temperature this ship was shown in 1988 and I believe while data used to much bigger field about 30 Kessler and this had room temperature and you see also this is again the the holy systems as a function of the gate voltage AUC to clear formation of the plateaus is of course not very accurate yet but they are the proper values when should be at or near the room temperature and the reason is because of this relatively big uh slung level space because of this very very fast Sacaton albeit motion shape could save many useful because the quantum Hall effect is used as the standard for assistance if you now can do it instead of having to cool down your sample in a crisis that and applied magnetic field you could do that at temperature that might be useful as well studied this is not yet useful because it's not get the butt of this soaking opened a cutesy of 10 to the 8 slipped into the vault into the mine is a goat and undermines 9 which you need habits who knows what might come out of yeah that was an
outstanding educator this 1 this so there has been no problem the value of the United States not only I had a look at this calculation it's see pages long and not I have another look at it and I said Well so this a complicated it's OK I can see a little bit about that because if you have in the part of the bulk of graffiti so maybe that's because then let us consider it came came around to go from OK to cater primarily you really have to invest a lot of momentum because you have to and that is using also easy and so so you could say almost the action go it's going it's happening with elections which stayed close to the case the value of the goes of the paper and you can actually use these means of called and drawings solve the main lesson is that in the Balkans gave the state primaries do not mix however if you have 1 specific age which is the object which you can't really tell you will you can see what is happening there is an elected coming which is described by some way function which which and it's a basically reflected from the ejection if you now want to impose the proper boundary conditions that you find that you have to use both at the the the scattering from the edges mixes developing and this is the reason why why why why and this apparently worked in such a way that the energy can even go about it was the announcement was made I would not you know I would not be used as principle all it would be possible if you Fermi energy to sit somewhere here where you you have this state occupied in all this was going to good use it but it is very very complicated and you have to realize that this is obtained from a calculation I think it is a simple calculation where you only include hopping between neighbors between sites in the besides well it's not yet clear if you really need to include also the hopping between the 8 sites in the sites and so you could say something certain next nearest neighbor with review would include that then already this kind of subtleties already change however this is not is dead is rigid and this is this you cannot avoid but this 1 is motion
by the defendant was the question so if I if I know we Sadia this enormous quantum Hall effect is proof of single-layer amenities I have to show that violate graffiti beds differently so this is by layer graffiti what you see is that you basically have to accept letters and you have shifted she is quite yet you have basically shift that the label by basically half a letter spacing this amounted to much because of that but you can realize that what you have to do now so if you know really want to look at the electronic state against while we have used this hopping had between the a cited the besides to calculate the states of single acre-feet now we have to use of course the coupling we have to include the coupling between the uh between them the year the different layers and you can of course do that by law in first-order is by introducing some cobbling element which is the government 1 had between these 2 atoms which happened to be on top of each other and of course you can also take a company between between this 1 and this 1 against 1 more complicated than that but that's only for this 1 then you you get the Hambletonian which little with similar to what we have seen before but now looks like this so now it it does not have the 1st of all it already has mind that's already indifference the single-layer basically did not have a mom this what has amassed and you see that now it's still has all the elements of the diamond all but I see that that is a square details are not so important what is important what finally comes out of it so now we in single layer graffiti we basically had this nice diagonal cone-shaped dispersion at the end and basically the what the energy-dependent linearly on the momentum that which basically said developing means that we had this Marsalis electrons here we get something which still has a nice curvature and then corresponds with a certain Moss this is the sequence of lumber levels again this is not the it's it's not easy calculations but it's very different from graffiti from single-A graffiti I can you show it here just look at this 1 and if I do this is this was the normal situation where yourself fixed sequence of long low levels which are equally spaced and have a spacing of age but ominous eh and he this was the situation for Single-A defeat here at the special 0 energy level then we have the next 1 and then with sensors biggest energy spacing and become smaller and smaller and of course we can hold this is the case for violated the feeling that is still this behavior at the station is not fully constant but what especially if that the generosity of the Lommel level at 0 energy becomes twice as much I don't have a good argument for that it is also related to some kind of many faced that but it's important to realize that now if you change your Fermi energy from here to here then of course you the occupation of this low-level goes from 0 to 1 but you changed twice the amount of states as if you would go here and because it is so that basically means that again and this is the the violin case if you now a look at the Bilal case you have a jump but this is 0 and this is this is the 1st but that now you see that you do have a regular sequel all that old all the steps basically understate the where's the freedom in Pensacola graffiti at the 1st divorce was on behalf of the rest of the steps here all the steps of the state so this is how you can recognize it's a bit technical and where to study how you can distinguish a double-layer from from In this way you can go on to just 3 layers of sediment set of it and it becomes more and more Michigan this is the answer to the question if it would be violated that it would be like
what can you do it by layoffs that's very important thing which you can do which which single just do not have there's no gap in single layer so you can't not switch off the conductors of field-effect effect consists of about remembered is typically the shape you can you ate at the neutrality .period uses is the highest that itself you UK should be also whatever if you really want to make a decent consistent evidence which would nominal so you have to Due to think about the solution and what you can do in is the following now I will try to
illustrate that mission use this isn't too late yesterday and the layer now I'm going to make a gate on which recall well there is 1 thing was and wrote to plot making gay political supporters series to move here and I'm going to apply a positive faulted suggests 1 Channon negative voltage to that 1 sold if this would be a single layer there will be no effect because this positive gate voltage wants to attract electrons negative gate wants detect holes if the scaffold as you're saying there's no net effect if it is to buy a layer that is also no net effect on the density the because it's still 0 but that that is of course an electric fields and this lakes the future on this so the potential of this nature will be a little bit higher than the potential that led the energy levels if this would be be isolated levels or unless it is it will be to independent layers of graffiti and the energy level
of this 1 won't miss it I would have to be careful with the potential which shifts relative to that but now it's by laying there where we already know that we we have to include the coupling between usually sold let's see what happens a hundred just goes to show you this this this again this is Hambletonian in in the matrix for form uh why have because we already sold that this we already life these days basically this from the single goofy Haven this describes the long you could hear the mob rows and columns this formation the describes the wave the law the wave function on a site in the 1st lady this is the way from some the B side in the 1st lady of the the 80 day atoms in the 2nd layer and this has to be entered in the 2nd leg of his you recognize headed this mechanism and you can you conclude that had by a by adding a negative potential at 2 to these elements and a positive potential to development and now you have to remember that the machinery you have to diagnose lighted etc. etc. and calculating the energy levels and this is what you get this was the case for violated the the without any fault itself these 2 layers are basically equivalent and this is a voltage applied and now you see nice seeing what happens is you chase the events search and now you have a gap there is a range of of energies where there are no states so in principle if you have a if you can also should at the same time she shift your Fermi energy therefore is of how could you do this supposed you you apply unless I pushed them temples here has assumed tenfold and his minus 10 holes so that would give you this kind of structure I this and now let's say you make this share plus 15 balls and this would be minus 5 so the difference in the story the difference in the indicate voltage remains the same so the electric field remains the same so your your bands you splitting remains the same but the only thing you have denial you have changed average gate voltage so and in 1 case you have attracted more electrons you have attracted more also residue of shifted because shift affirmed the energy and now you see what happens if fermions since you're states here and the gap and states 3 systems and then again you go into the election states principle by distant you could make a while artificial semiconductor it is very practical answers the knowledge we have because this really depends also on the fact that you have 1st of all you have to make a relatively big electric fields because these are very close together so this if you even if you have a big electric field this potential changes only a little without that so it's not so practical and also you have to have material which is really really high-quality otherwise well they're all kind of imperfections which misses at this but in principle this is what you could could do OK let me say a bit more about to convene in general so this is what I basically discussed and there's a nice analogy with high-energy physics that it's the UK like the equations for Masters particles I have not basically explained occured as I think I've explained to Iraq equation which you can actually described for a lot for the generation of electrons and holes from from radiation that is an interesting phenomenon which is called colliding tunneling which is a lot which also can be modeled his caffeine I'm not going to say as much above that once we have clearly already two-dimensional physics quantum Hall effect we can go to one-dimensional systems we can make agreements become a quantum dots the people are doing that we are also looking into that have badly etching out a small range of caffeine we can also use some kind of self-assembly that's also very nice and so you can make basically make small molecules which basically consists of a lot of Texaco's cinnamon nice regular weight if you can really increase that you can really make artificial feeding so that this hasn't been very interesting direction technological application that you just mentioned their sensors so the nice thing about the thing is that all the electors out of service you could say Well so what metals there also existed and that if you put something on metals you only change the connectivity at the surface and there are lots of lots of layers below so the effect on a lot of effect will be extremely small so so whatever you put on survey of a metal isn't going to change the the properties too much in casino obviously it will make us all all the electors in the coffee see what is on the surface so you can use it to detect guest molecules of gas happens even in this very high sensitivity you can actually even measure 1 if you make a device small enough it was shown that you can really see steps In the end the resistance and each of these steps should correspond basically by having just 1 guests at the more 1 guest monocle absorbed somewhere to your feet so there's a sense of the way to do that I have basically already said that you could think about making alternatives for silicon technology that might bite imitating the making artificial semiconductors using violated the fee that is clearly not estimates in its infancy and because people are trying to do that and you really have to export is so of course I will go to believe that Cathedral replace silicon but certainly in the area of sends Austin dedicated devices clearly Covina it all in making an impact good thing preparation the could state method that shows not very useful for application of obviously and because it has a low-cost box which is to discourage statements but it's also has the highest "quotation mark spot you really have to find your way but fits that is the chemical a CVD tricks you can prepare graffiti all metals and other techniques and tomorrow I think there will also be demonstration of uh we will also show some graffiti which is also made in a different way there are also some some the techniques for preparing the graffiti layers picking it up from a from my surface offer of a solution not going to say too much less good thing spintronics up probably will not have too much time to discuss about that but that is clearly also wanted in 2011 suspended goofy so I said they did so not so
nice to have a good feel invisible nice properties but it has to sit on a substrate and the substrate is silicon oxide and that is not a nice a smooth material so let's get rid of the substrate so how you do that the uneasy look at that level we had silicon silicon oxide could feed the remembered this this this this picture of this field effective we had contacts gold well now we make a device like that and we put it in a chance HF is a very nasty assets which eats up quite a lot of things including also work people if you're not careful bones for instance yeah but it eats up the silicon oxide that it doesn't at the gold so so imagine review Gaultier starts Eden the silicon oxide and it stops at a selected so what you can do it if you don't if this would be a silicon oxide fuel you can actually make region where this could in principle where this graffiti will be suspended Of course you have to be careful had because there if if you if you would have this in solution and you take it out and added that I of course there will also be always the the interface between the but this this is going to die so so this will be a still be still summer summer some equity and and only dead and which will basically moving certain direction because of drives and there will be some surface tension which connected story you have the interests of drivers in in in a in a careful way but then indeed you can make suspends the fee now you not there yet because it's still all kind of germs on the substrate so what you do is you pass a very high current between them and so this is not a property of the graffiti it's a very good electrical conductor is also very urgent so you can you can achieve very very high temperatures without a caffeine disintegrate but what happens in all the world altogether during a dispute "quotation mark evaporates or whatever so this is called current annealing so in that way you can really make a graffiti layer which is almost ideal the very nice this is picture of such a later this is done with the transmission like microscope which is a very very high resolution so you can use a single is already here by later I had more free but it doesn't work with what you see is of course you can recognize in this nicely armchair edges and he had another 6 signatures which you see that something attached looks like but there's still something attached to it so it's not clear what it could be maybe hydrogen or something like that but that the case that what is done here is that the high energy electron beam is focused on the graffiti and that is a detective in the niece and of course to be miscarried and that of course makes finally picture like this but at the same time you can actually see that that is the whole which is formed he grows so too particularly some of these items are embracing bartered away I went time progresses history could make controls if you like you can make controls very small holes in the in the in the in the membrane so wide why what can you do with it well that if people actually looking into that so if you have a small hole and you whoever debate and you have to take to visit Pulitzer released for this whole and in the meantime you can measure the resistance the electrical resistance between the top and the bottom you might imagine that every units of the DNA which is a little bit bigger it fills the hole that it conducted stocks is more difficult for for I used to go through and the smaller smaller there a smaller units follows the conductor's goes up again and then of course you cannot make a nice DNA you can use sequencing with this would seek secrecy with this technique so this is a little bit of future what future activities but still it shows what you can do with this kind of of of Christine based membranes question here you if you were from the electronic traction of what the government is thinking of staying in the area of simulated for a single I would say that that the same principle and you will be the same as you have sex and pattern and for the moment I have to be really careful applications this is a graffiti probably not a single later I have to stay on a flexible substrates that what is the problem with optoelectronics so the problem is you have to get the light out of the summer some direction so this is a light-emitting diode this is actually a lot better than this is based on organic materials with capital you haven't handled it you have to apply obviously a voltage between them to supplied current and the problem is that 1 of these electorate has to be transparent for life because the lightest the going and dinner which is used intent oxide which is out of I mean it's certainly not the easy Asia material to handle you would like to replace had 1 way to replace it is consistently placed by because this is the reason I think it's a relatively good conductor is that is as we've shown and that it has a very nice aspect is that it has some some something which is universal life absorption and universal means that the absorption of light In a specific machine so it's it's it's not you free and it's not invited but someone in the light machine and instructions given by buying which is well-defined comes all foreign office find it's so typically 1 over 100 and 37 so basically 1 layer of conceding absorption about 2 . 2 per cent of the light and 2 layers you can basically at the the absorption and of course it is not so much so so if you make a single of your view 1 of these elections of graffiti you only lose something like 2 . 2 per cent of the light of by the way this is also related to the Scotch tape method effectively can distinguish single-layer graffiti from from from 2 layers of latest in Italy and Britain related to the fact that this this absorption nicely increases with the number of late
this is a nice from now on show this week but is it's a funny but funny take so let me just make this is a material which has an index of refraction and want and this is too so now we have a light coming with a certain angle and now it is the school Seiko on it is called seeking to write and now we have a law which says that the 2 sides of the Taiwan divided by the of the 2 the intervals over and want this is no small operators sciences still it is basically fundamental law for this section but what you see the only thing you can do if you end up with a finger like this you end up with an angle like this so why is that because usually the index of infection is positive however compressible also make materials which have a negative index of refraction for life which is tricky business I'll show you that you can also do this with elections using the so what do you do this is like a few layers and now I'm making and to college I have 1 region where I have a gates which can be on top of on the bottom of this matter too much I apply positive voltage this is my gate I applied a negative so remember positive voltage is going to attract elections so what I have to say but I also have used system this is this is my energy diagram this is the 1st energy should you should realize of course that the system is in equilibrium so the Fermi energy is likely see deferred usually is always the same but I have attracted the lecterns you that basically means that they have pulled out all the energy level so he had this will be my my my 0 energy and here of course I would have my called for in this case the letter so here I am the same thing and but now the opposite way I have basically this will be now my my familiarity this is my hero energy now I am in the regime of the whole so this is not Michael the trick is the following have a source this is a sort of election and I have a problem and I want to know can making the image of the source here so as to simply as well can I make basically a model of a lets that because that is what the lens that's computer lessons here and then I will start my mind race will start from this source in this direction and that has to be the direction to be changed and focused in the direction of my focal point here and hear the same thing is said so be elected can I make a lens and just you can do that because let's look at it now we have to be always has to to begin with we believe if careful so let's look at elections which we have a velocity in this direction so that would be great if re-elected sitting here if you sit on this call this election has only has no no no velocity bi-directional India In its action where can I go well it has to conserve the energy because the energy is really meant say so it has to end up here because this is the slope of the cold so here again had assisted the slope of the cold and rest because 6 of appeal but you see the momentum is changed because clearly this was the government that this had at the positive momentum now sits on the other side and went in this case what is topic if that's not clear why the widest did so well yeah because there is there is a difference of potential those electric field would you cannot show the initial position
that affected what happens is the velocity so by just the fact that you have to do well but you go from the lectern called to Holcomb and you have to change the velocities will remain the same but the momentum exchanged you
correctly show that you get the pattern like this and so that elections which start out In this let me let me in this in this industry should they go like this and then at the interface emotionless Chase ideas and they're basically focused on you and the same holds for electors you set the course I have to say that this has to
be perfectly symmetrical because the 1st at the gate voltage which apply here and there has to be exactly opposite so they get the nice systematic picture then you
can actually get this of course is very nice because you have some artificial lens you don't have to do anything uh anything special not not complicated geometries just had transition between the doctor and end of Is that a drawback on the yes because this is a great 1 could say these are race is like a geometrical optics and of course you know that there is also the client defections a few really taking into account that the well lighted these waves also these elections of course they have a certain way aspect to it turns out that you cannot truly focused all week even tho start with point you cannot get married to refocus it in the port you always get something which has a finite size there but it's not necessarily a problem what is the problem is of course that you really have fewer graffiti you could see it has to be an extremely high quality because suppose your electors gathered here that it will go a different direction and continue it will never end up nicely in .period this is called the 1st our hold
lands that is addition scientists and basically year came up with this idea again it looks like you have made a material which is a negative image of perfection I'm going
to skip this part because this is what basically our contribution was to convene in view of the time let me just
skip it so I want to go
2 last part and last can
we have Covina help this is my daughter used a of and I have come to India to to give a little bit of impression of the size this is electrostatic loudspeakers so I when I have time which is not too much at the moment and I lost some pundits at told this electrostatic loudspeakers it's that simple it is stated in a frame of what the PVC jokes just from a formal electricity tubes and using these nice course at Yosemite white so that this like this there's another state or like this the idea is that you apply your sound signal you applied is between the state of and it is now that in between you have a thin membrane and as you put it at a certain voltage high-voltage why because you want to have served certain lot of big charge to sit on the membrane that's the only role of the membrane here you have your sound signal so the electric field of the sound signal both Bush's dismemberment of so this is how it works the nice thing of course is that it's his commune relatively light compared to got loudspeakers where you really have to more much more Moss he dismembered canopies will be very very light so you get a high quality sound reproduction while I was just interested in the principal and I wanted to work didn't want to spend too much money so that is why won't and is mandating what I use for the membrane was kitchen foil you can really statutes cushion dead until Ted after a while but because you can really stated you know but now comes the problem you have to make it conducting because it doesn't have to conduct much but just enough to keep that you can't you can have a chart showing that several ways when is sold but that's very very key and the other 1 you can only guess that this graphite so the idea is
to take this you take the good fight you take summer cotton wool from what's to illustrate that here but you can imagine put a graphite on the news media it out and used up quite a lot because otherwise you get all these good all these good fights their parts only cut particles you don't wanna you really want to have a school and now it says this is from a book on this and that's I will translate a former do it do it yourself Mayor of the electrostatic loudspeaker bought it he says what you should do is you should hear about discussed fight ended typical uses value should be of the order of 10 killed I have not seen this by the way because then we would already have Annabelle because remember this this this is banking that is almost close to this unit of the systems of unit of conducted Friday while I can tell you what I measured at home 5 people which is almost the same as people measure in these and this goofy Field effect right so what is what is now
happening again I have cannot prove it but the idea is again it's basically analog office of the Scots statements of that of course this graphite is very messy as a Europe without Italy maybe some some Fidelity big flakes sitting there the it's time you go your cotton wool you take off toward a more layups and of course it it is finally of course you get a conducting path as 1st of all you have your below the percolation threshold that very high exists and then put on mortar you get a conducting boss and then when you get this conducted by users 5 so not uniformly absolutely not evidence he seems to indicate that your but the critical conviction boss is a key determined by a single layer because if I would then layers I would nominate a five-year-long would make 500 on it and then so then I came up with the idea how you make you know if you insist on so this is the the floral sofa she made the gate residue cover 1 1 1 site is graphite and then it doesn't matter if it's a of limit-up that's going to Newgate electoral isn't too much then hit another the venue during the governor this carefully and whatever doubt because that has to be Europe's single defeat player in major-league history then you apply adhesive voltage between your legs you have made and and so this is your gates and a new measure the resistance I have not that I studied at home but the problem is that if you go from 1 layer with graphite 1 side and the other side that is relatively the big probability for short circuit if you look carefully I'm sure that you must be able to do it so that that you do not have a short circuit that there is a problem that this fall is my candidacy so unique kilovolt probably to apply for your gate voltage so if you do at least could be could be the careful and I was not able to do that hits you but you can try and convince yourself that if you measure the existence of this was indeed you get something like 6 or so I'm not kidding OK
I think you died I would and and allowing for some more questions I'd like to stop here but I've given you a glance of what can be done with graffiti I actually wanted to make a list of all the topics which I did not discuss the settlements on the way because it will take several several flights that will do it if you want to get more information since we are now at full I like to work as well refer you to the web sites of the to remember which actually is the website of the full program on few based tonics which involves troops from Delft University Life University from University in and 9 major universities and you see some in lieu of the various groups into the program where you can further there and get some from but I like to stop you think you question you mentioned that people application in terms of customers hold reversible the members would be 1 of the guest speakers said that this is a company that has again retailers basically faces auction
so I just sticking to Ugandan member of a source also led to store effects which can have if you put that at the moment will probably be 1 of them is charge that there could be some jobs between 1 of would actually don't be so so obviously that will change the 2nd 1 is that Saskatchewan and Saskatchewan of course always reduces the resistance and if you include bowling ball depends where you are in this issue are .period neutrality .period you should you think clearly if if the doping goes this way and that that it would the sure you you will reduce the issues that both of were so 2 effects which you could also be used to to work distinguished type 1 of the basic this is used for this season's Michigan reversed you can also fictionalized defeat with assessment next that indeed EU you only make it different from those connected with the models you want to detect that is already very active area in the area of nanotubes yeah for sure it will also have some some consequences here but it's more complicated this discussing pocket maybe I should show up in the middle you
want see these effects for instance if you if you mentioned his
curve and room-temperature In
atmosphere you don't get a nice
because what you get is said Western would you get if you go this way then you get the peak here if you go this way then you could be there why is that there is basically charge on your on your graffiti which can can can can come back and go away so this is always measured effective 2 but it shows the sensitivity of your refused to whatever it is go to and vote for the occasion I would like to work the so he warned that the good length the like like elections if you would like to the call and a lot the control of the and the was OK so all you will
not all you want if you want to do to chase the strength of the lands here because I value has been at the end of the month in the eyes of the
decks also if you want to control the strength of the lens is pretty clear what you can do anything
you just who you increase your gate voltage but the problem is you you there and and I
I don't have that I don't have the drawing near you while you're always stuck to the principle that this distance has to be the same as the state's it's not like a real then so you work your you different you you can you if you approach showed the lens standards focal point to changes in that doesn't work because if you do that then if you if you would approach in a situation in which would put your point here then there will still be some folks think but it will not fall and that the .period so that you really have to have as a statement that he had promised land between 2 to lot 2 sides but then you
can still use the strength of your lands by changing uh to date book controlled I told you so I don't know if this is a very useful thing and that is a nice example of this strange behavior of of elected to it In graphic there and I don't think so to be on know what people have been focusing a lot all this this interface said because you have the transition from people in the region have and which we were a that this condition I don't think it has been major because complicated you really have to have your and your letter scattering means the path from the bigger than this facing because of the letters Askatasuna units doesn't work anymore and that is very difficult to do well if you have suspended caffeine you could do it uh but then you have to make a suspended US West to tapes it's in the public eye and so it's a complicated expert so I don't think it has been done on it you have to
for 1 thing new yeah I did well obviously I thought about the about this question and and and to be
honest OK I could say well that you that you control this goofy technology to such an extent that you Canadian a controlled way make devices which have a well-defined bands structure like this example was violated graffiti but then basically I'm already assuming that that this is a useful way to go and I'm not convinced about that so I don't think this this year question has has a well it's a single answer and what we do know is is that the amount of activities in this area so and that is said that is you wouldn't even as evanescence of integrating supermarket you can look it up in the bile kind of goofiness the few times I was with all the news of on the conceded that in the year so that every basically every relevant that aspect is already being looked at what is of course very crucial and I think that this should be an element which is
important and air that
this is not a practical way to make graffiti writers it's it's very nice 2 tool to exporting media the fundamental at the gate if fundamental Web properties with no not at would you like to do it will have is a well-defined way to make a few layers only substance for audiences by by the Justice techniques which have shown that is at 1 group the group of altogether which should mention where she was already doing that for several years that was trying to make the Finlayson silicon carbide and what they did is that took silicon carbide he did it and so that the silicon disappears from the surface and then you lose your your left the several layers and the problem was that they could not shouldered into a single graffiti and and then you needed to Scott state to itself so I would say certainly there has to be more and more developments in that area so you can really making relatively large a size Kerfien layers of high-quality coffee makers because there is no fundamental reason why can we do so I think that said would be 1 of the challenges the true the strongest material it depends on what you call strongest that I mean if you have the perfect sickness purpose and it depends on what you know you if you it's usually defined as the percentage by which you can stretch it because and and this can be searched by 10 per cent of something and that is I think a lot of money I'm I'm not an expert in mechanical properties but there is 1 important reason for that because they're very little defects and because I showed you this transmission electron microscope while this is only a small area that people have actually been looking for defects that could not find any defects so there is no if you if you start to their area of course starts to break somewhere but at the very moment if there are no differences can start somewhere so this is 1 reason I think this is it can we speak it it can be a strained by about 10 per cent and which is more than any other despite the more for example spiders OK if you are OK it can be sustained and the force which which which it can withstand life to the sickness is the biggest 1 is you can have a problem with it I think that is yet so you can call your own the answer is yes as usual and on and what about ostriches and I II and III again have to be careful about what what is relevant here and again this is the big area which had been almost skirts is what the entire picture have given despite the protocol normally directly elected by the use of that structure and then we started following the selectors in areas that have been them on thousand this year and the only thing we say stars to occupy all these levels but does not start to modify the states it only occupied and clearly factual qualification is a measure of of collective action sold the interesting thing about the feeling is that this because of the two-dimensional nature and also because of the fact that you very velocities calls that the nature of electronic transaction changes to better so this is very destruction abolishing this very interesting 1 because it's in a different parameter and I can only tell you the difference was part of the city testing Europe also is suspended because then you get highest quality the problem of getting the disposal of the violence from the land lines you version of its somewhere it was all this case the size of and size of the way of life and they the 1st of the the 2 of you look a lot so but that's just about everyone someone and then you have to have wavelengths 1 which would be likely to be I think it was also a question which we could by electoral reflection I thought she was having probably that but I don't know what I want accommodates the easy way to do to check singular about and in more easygoing applied this complex and with good good Mark II but I don't know about the incident OK no questions also I hope that I have given you a bit of a flavor of of of proceeding as a very interesting material uh where we had had heading it's not but it's not clear in my opinion it basically I the nice thing about defeated it has something in it for everybody including our high-energy physicists and will practical work people like like experimentalists of course on the final also was part of the story but maybe will approach it from a different point of view I'm pretty sure that the family that knowing only 5 and thank you for it thanks
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Metadaten

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Titel Master class II with Bart van Wees
Untertitel Graphene: from Scotch tape technique to anomalous quantum Hall effect
Serientitel Physics@FOM Veldhoven 2011
Autor Wees, Bart van
Lizenz CC-Namensnennung - keine kommerzielle Nutzung - keine Bearbeitung 3.0 Deutschland:
Sie dürfen das Werk bzw. den Inhalt in unveränderter Form zu jedem legalen und nicht-kommerziellen Zweck nutzen, vervielfältigen, verbreiten und öffentlich zugänglich machen, sofern Sie den Namen des Autors/Rechteinhabers in der von ihm festgelegten Weise nennen.
DOI 10.5446/18000
Herausgeber CityTV.nl
Foundation for Fundamental Research on Matter (FOM)
Erscheinungsjahr 2011
Sprache Englisch
Produzent CityTV.nl

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Dauer 54:45

Inhaltliche Metadaten

Fachgebiet Physik
Abstract I will give basic introduction into the physics and technology of graphene, a one atom thick hexagonal lattice of carbon atoms. Starting from the elementary electronic sp2 bonding states between adjacent carbon atoms, I will show how the two-dimensional electronic bandstructure of graphene is be obtained. The role of the Schrodinger equation is replaced by the so-called Dirac equation, which decribes a two-component wave function. This leads to very rich physics and a interesting analogy with high energy physics. From an experimental point of view I will give a demonstration of the Scotch tape technique which made it possible to obtain single graphene layers for the first time. This made it possible to observed new effects, such as the anomalous quantum Hall effect, in field effect transistors based on single graphene layers. Various techniques to improve the quality and/or the quantity of the graphene layers will be discussed, including suspended graphene and techniques to grow graphene on various substrates. Finally a future outlook will be given.
Schlagwörter graphene
physics

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