Self-consistent quasiparticle GW (sc-QPGW) calculations are used to calculate the electronic properties of α-Si 3 N 4 and β-Si 3 N 4 , as well as α-SiO 2 (quartz). The optical properties are evaluated by solving the Bethe-Salpeter equation in the Tamm-Dancoff approximation. For quartz, the predicted dielectric function is in good agreement with experimental data, with the onset of absorption located about 1.2 eV below the direct quasiparticle gap. For Si 3 N 4 , the theoretical dielectric function is fairly structureless and the onset of absorption corresponds to an exciton with a binding energy of 0.6 eV. The calculated sc-QPGW data are compared to more approximate calculations using G 0 W 0 , GW 0 , and a local multiplicative potential V (r) designed to predict accurate one-electron band gaps. Although these calculations yield similar one-electron energies as the sc-QPGW approach, the bands are too narrow, leading to a "compressed" optical spectrum with too small excitation energies at higher energies. Finally, we report the absolute shifts of the conduction-and valence-band edges in silicon nitride and silicon to facilitate the prediction of band alignments at silicon/silicon-nitride interfaces.

УПРУГИЕ СВОЙСТВА НАНОСТРУКТУРИРОВАННЫХ МАТЕРИАЛОВ И ИХ РАДИАЦИОННАЯ СТОЙКОСТЬАннотация. Проведены расчеты модуля Юнга наноструктурированного материала в зависимости от размеров и объемной доли нанокристаллов на примере объемного nc-TiN/a-Si 3 N 4 нанокомпозита. Показано, что определяющую роль здесь играют модули упругости a-Si 3 N 4 матрицы и самих nc-TiN нановключений и их соотношения. Исследована кинетика дефектной подсистемы с учетом рекомбинационных процессов и действия стоков, которыми являются нанокристаллы, при радиационном воздействии на нанокомпозит.Ключевые слова: наноструктурированные материалы, упругие модули, радиационное воздействие, напряжения, радиационные дефекты.Для цитирования. Углов, В. В. Упругие свойства наноструктурированных материалов и их радиационная стойкость / В. В. Углов // Вес. Нац. акад. навук Беларусi.

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Modern electronic devices are unthinkable without the well-controlled formation of interfaces at heterostructures. These often involve at least one amorphous material. Modeling such interfaces poses a significant challenge, since a meaningful result can only be expected by using huge models or by drawing from many statistically independent samples. Here we report on the results of high throughput calculations for interfaces between crystalline silicon (c-Si) and amorphous silicon nitride (a-Si3N3.5:H), which are omnipresent in commercially available solar cells. The findings reconcile only partly understood key features. At the interface, threefold coordinated Si atoms are present. These are caused by the structural mismatch between the amorphous and crystalline part. The local Fermi level of undoped c-Si lies well below that of a-SiN:H. To align the Fermi levels in the device, charge is transferred from the a-SiN:H part to the c-Si part resulting in an abundance of positively charged, threefold coordinated Si atoms at the interface. This explains the existence of a positive, fixed charge at the interface that repels holes.

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