Authors: K.F. Ho, C.D. Beling, S. Fung, M. Biasini, Gabriel Ferro, M. Gong
111
Authors: M. Yoshino, Y. Shinzato, Masahiko Morinaga
Abstract: Formation energies of various defects in Al2O3 and SiO2 are calculated by using the plane-wave pseudopotential method. Also, the formation energies of Schottky defects and Frenkel defects are evaluated on the basis of these calculations. It is shown that formation energies of these defects are higher in SiO2 than in Al2O3. In other words, less defects are formed in SiO2 than in Al2O3. It is also found that the principal defect is the cation Frenkel defect in Al2O3 but the anion Frenkel defect in SiO2. These results agree with the experimental results that Al ions diffuse preferably in Al2O3 but oxygen ions diffuse in SiO2 at high temperatures.
713
Authors: Daniel Macdonald, Prakash N.K. Deenapanray, Andres Cuevas, S. Diez, Stephan W. Glunz
Abstract: Oxygen-rich crystalline silicon materials doped with boron are plagued by the presence of a well-known carrier-induced defect, usually triggered by illumination. Despite its importance in photovoltaic materials, the chemical make-up of the defect remains unclear. In this paper we examine whether the presence of excess silicon self-interstitials, introduced by ion-implantation, affects the formation of the defects under illumination. The results reveal that there is no discernible change in the carrier-induced defect concentration, although there is evidence for other defects caused by interactions between interstitials and oxygen. The insensitivity of the carrier-induced defect formation to the presence of silicon interstitials suggests that neither interstitials themselves, nor species heavily affected by their presence (such as interstitial boron), are likely to be involved in the defect structure, consistent with recent theoretical modelling.
497
Authors: Hideharu Matsuura, Nobumasa Minohara, Yusuke Inagawa, Miyuki Takahashi, Takeshi Ohshima, Hisayoshi Itoh
Abstract: From the temperature dependence of the hole concentration p(T) in a lightly Al-doped
4H-SiC epilayer irradiated with several fluences of 200 keV electrons, the density of Al acceptors
with 0.2 V E + eV decreases significantly with increasing fluence, whereas the density of unknown
defects with 0.37 V E + eV increases with fluence and then decreases slightly. Although only C
vacancies increase with fluence because 200 keV electrons can displace only C atoms, only the
increase in the density of C monovacancies cannot explain the changes of p(T) by 200 keV
electron irradiation. It may be necessary to consider the relationship between C vacancies and Al
acceptors.
379
Authors: Hui Ling Zhang, Qun Bo Fan, Fu Chi Wang, Feng Zhang
Abstract: To enhance the high-temperature stability of zirconate pyrochlore structures, one has to focus
on their transformation to the disordered state, fluorite. An atomistic simulation calculation is presented
in this paper to predict the propensity of rare earth zirconate pyrochlores to transform to fluorite at high
temperature. By detailed calculation of defect formation energy of cation antisites and Frenkel pair, as
well as their interactions, the mechanisms of disorder transformation are ascertained. The results show
that the tendency of cation disorder is less than the anion’s and disorder transformation will accelerate in
advanced stage. The calculation of defect energy in pyrozirconates with different cation on the A site have
proved helpful in unraveling their different order-disorder transformation tendency.
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