なかのにっき

3.3e14 * (47.9 / 6.02e23) [g/atom] * 50 [cm^2] * (60 * 110) [sec] → 8.7 [mg]

http://tomos.webmasters.gr.jp/diary/

http://tomos.webmasters.gr.jp/diary/d200303a.html#t02-2

By means of scanning tunneling microscopy, the Si(313)12x1 surface has been found to be, after Si(111)7x7, another stable elemental semiconductor surface with a metallic nature. On the basis of the details revealed by the high resolution STM images, an atomically rough model consisting of trenches and a variety of building entities has been proposed for the surface structure for further investigation. The common features of major stable silicon surfaces as well as the similarities and differences between these surfaces and their germanium counterparts are discussed in the context of the driving forces behind the reconstruction of elemental semiconductor surfaces.

By means of scanning tunnel microscopy the surface morphology of reconstructed Au(001) surfaces has been studied after bombardment with 600 eV Ar ions as a function of dose, in the range of 10^13 to 10^16 ions/cm2, and the experimental results analyzed in the light of molecular dynamics simulations using a glue potential. At low dose (5x10^13 ions/cm^2) new defects, different from the commonly observed vacancy islands are reported. They appear as depressions 0.06 nm deep, with a characteristic width of 1.44 nm. Bombardment with similar doses of Pt(001) show the same general behavior. Molecular dynamics simulations with a realistic glue potential that reproduces the hexagonal-like Au(001) reconstruction, confirm that these depressions are in fact two-dimensional /3 dislocation dipoles originated by the relaxation of vacancy rows on the ridges of the topmost reconstructed layer. These two-dimensional dipoles are seen to dissociate into individual two-dimensional dislocations that display the characteristics of ordinary bulk dislocations, e.g. glide or climb. At higher doses (3x10^14 ions/cm^2), but well below a nominal removal of 1 monolayer, vacancy islands, one atomic spacing high, are seen to nucleate on these depressions. With increasing ion damage these vacancy islands become the dominant feature. For doses of about 10^15 ions/cm^2, other defects related to the reconstruction, such as perpendicular reconstruction domains and unreconstructed patches of (001) square symmetry, become visible.

We report on the complex dielectric tensor components of four chalcopyrite semiconductors in an optical energy range (1.4-5.2 eV, from 0.9 eV for CuInSe2) determined at room temperature by spectroscopic ellipsometry. Our results were obtained on single crystals of CuInSe2, CuGaSe2, CuInS2, and CuGaS2. Values of refractive indices n, extinction coefficients k, and normal-incidence reflectivity R in the two different polarizations are given and compared with earlier data where available. We analyze in detail the structures of the dielectric function observed in the studied energy region. Critical-point parameters of electronic transitions are obtained from a fitting of numerically calculated second-derivative spectra d^2e(w)/dw^2. Experimental energies and polarizations are discussed on the basis of published band-structure calculations.

ZnO typifies a class of materials that can be doped via native defects in only one way: either n type or p type. We explain this asymmetry in ZnO via a study of its intrinsic defect physics, including Zn_O, Zn_i, V_O, O_i, and V_Zn and n-type impurity dopants, Al and F. We find that Zn_O is n type at Zn-rich conditions. This is because (i) the Zn interstitial, Zn_i, is a shallow donor, supplying electrons; (ii) its formation enthalpy is low for both Zn-rich and O-rich conditions, so this defect is abundant; and (iii) the native defects that could compensate the n-type doping effect of Zn_i (interstitial O, Oi, and Zn vacancy, V_Zn), have high formation enthalpies for Zn-rich conditions, so these "electron killers" are not abundant. We find that Zn_O cannot be doped p type via native defects (O_i, V_Zn) despite the fact that they are shallow (i.e., supplying holes at room temperature). This is because at both Zn-rich and O-rich conditions, the defects that could compensate p-type doping (V_O, Zn_i, Zn_O) have low formation enthalpies so these "hole killers" form readily. Furthermore, we identify electron-hole radiative recombination at the V_O center as the source of the green luminescence. In contrast, a large structural relaxation of the same center upon double hole capture leads to slow electron-hole recombination (either radiative or nonradiative) responsible for the slow decay of photoconductivity.

The bonding and electronic structure of TiN thin films grown by sputtering have been characterized by means of resonant photoemission spectroscopy using synchrotron radiation. Specifically we found a complex resonance profile that exhibits a maximum at 45 eV followed by a second structure at 50 eV. The intensity enhancement observed at 45 and 50 eV is consistent with the resonant photoemission of the Ti 3d states involved in the valence band of TiN and the multiplet configuration of the [Ti 3p^5 3d^2]* excited states. The autoionizing character of the [Ti 3p^5 3d^2]* states could also be confirmed by observation of the corresponding autoionization emission. The resonance is used to determine the Ti 3d contribution to the valence band. The results are in good agreement with calculated Ti 3d partial density of states.

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