#homecmos IRC log for Friday, 2012-03-23

azonenberggo for it00:08
didjawhy do people heat silicon up to really hot temperatures like in this paper? (page 2 http://dl.dropbox.com/u/68719865/prl-strain-in-nanoscale-germanium-hut-clusters.pdf )00:15
didjathey say specifically: "The substrates were polished Si(001) wafers, cleaned by prolonged outgassing at 875 K followed by flashing to 1425 K."00:15
didjadoes this mean that they are making the silicon oxide disintegrate too?00:15
azonenbergdidja: i think they're trying to burn off any contamination on the surface00:18
azonenbergand no, lol00:18
azonenberg1400K = around 1100C00:18
azonenbergheating in atmosphere at that temperature will actually *grow* oxide00:19
didjaso the germanium grown on top of it is definitely on SiO2?00:20
didjai don't know why people are so hazy about what they mean in papers00:20
didjajust come out and say it damn it00:20
azonenbergI havent read the paper yet00:22
azonenbergkinda tired, been working all day00:22
azonenbergwill go back and look probably tomorrow00:22
didjawell this was done in UHV00:31
didjaand another paper seems to suggest temperatures as low as 600-800 C are enough for thermal decomposition of 1 nm thick native oxide00:31
azonenbergHmm00:31
azonenbergSo you're heating oxide in vacuum00:31
azonenbergand tryingto break it apart?00:31
azonenbergor they are, at least00:31
azonenbergthe only two reasons i've seen for heating silicon are growing oxide00:32
azonenbergand diffusion00:32
didjahttp://dl.dropbox.com/u/68719865/nanoscale-in-situ-investigation-of-ultrathin-silicon-oxide-thermal-decomposition.pdf00:32
didjathe dealy-grove model breaks down under 20 nm of thermal oxide i think00:33
azonenbergdidja: interesting00:33
didjadeal-grove i meant00:33
azonenbergyeah, i know what you mean00:33
didjashoot don't trust me on that. i just read that somewhere and now i can't find remember where00:34
azonenberg20nm thoguh?00:34
azonenbergthats a lot00:34
azonenberg20A maybe00:34
azonenbergi cant say i'm surprised that it breaks down under extremes00:34
azonenbergand its meant for air, not vacuum00:34
didjahttp://www-inst.eecs.berkeley.edu/~ee143/fa10/lectures/Lec_07.pdf00:35
didja< 20nm00:35
didjapage 1900:35
berndjdidja, as far as i understand it the wavelengths you're using for x-ray diffraction are such that the fact that you have an insulating layer etc is completely invisible00:36
didjasay that again?00:36
didjathe Si underneath (mechanical substrate) is visible and it's i think n-type doped00:37
didjathe SiO2 though... does SiO2 even show up as anything in XRD?00:37
didjait's amorphous so i imagine it just adds a lot of background noise?00:37
berndjvisible in that you can see how its atoms are arranged wrt each other, but not visible in the sense that you can't see that it's "below" whatever else you're looking at00:38
didjasure00:39
didjaso if Si is visible in the xray spectra? is Ge visible in the XRD spectra? SiO2 is amorphous so by definition you sould not see any distinct peaks in its XRD spectra00:40
didjawhy do people do experiments on Si (111) substrates?00:56
didjai still haven't really gotten a good grasp of crystallography00:56
didjajust last week i was pouring over communication systems stuff, now that the final is over, i can get back to stuff i like a bit more00:57
didjawell, comm. systems was fun, but no lab = no fun00:57
didjaazonenberg: how do you do research by the way? i'm looking forward to being a graduate student, but i'm scared too of the daunting task of being responsible for coming up with new ideas that have to work (publishable stuff)03:13
azonenbergdidja: your advisor is likely to be a good resource there13:47
azonenberghe'll know the field well and have a good idea of where the holes are13:47
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