Theoretical Study of the Lithium Diffusion in the Crystalline and Amorphous Silicon as well as on its Surface

Using the PAW DFT-GGA method and numerical solving of master equation the diffusion rates of lithium atoms inside both crystal and amorphous silicon of LixSi (x= 0..0.5) composition have been calculated for different temperatures. It is shown the diffusion rate for amorphous silicon is ~10 times greater than that for the crystal silicon. For both structures the rate is increased by 1.5-2 orders of magnitude while the lithium concentration is increased up to 0.5 value. This should result in that the LixSi/Si interface will be sharp. This fact has been further confirmed using molecular dynamic calculations based on Angular Dependent Potential (ADP) model. Also binding energies of Li atoms lying on different sites of Si (001) surface as well as the potential barriers for the atom jumps both along the surface and in the subsurface layers have been calculated. The data show the Li atoms move along the surface very easily but their jumps into subsurface layers are very difficult due to the high potential barrier values.

Fabrication of InGaAs/GaAs Light-Emitting Diodes with GaMnSb Ferromagnetic Injector Layer

The electroluminescence properties of ferromagnetic GaMnSb/GaAs diodes have been investigated. It has been found that diodes properties are significantly dependent on GaMnSb layer electrical properties. The intensity of electroluminescence of the diode with semiconductor GaMnSb contact is relatively low, that is due to a high potential barrier at the interface. In case of metallic GaMnSb/GaAs contact high hole injection efficiency provides relatively high electroluminescence intensity. Investigated light-emitting diodes can be prospective for investigation of spin injection effects.

Hot-electron Phototransistors in Hydrogenated Amorphous Silicon

ABSTRACTIt has been shown that useful current gains can be obtained in hot-electron device structures containing very thin chromium disilicide layers of nanometer dimensions in hydrogenated amorphous silicon [1]. The a-Si:H/a-CrSi2/a-Si:H device structure made using PECVD and sputtering techniques naturally forms a hot-electron transistor device where the electrons are emitted across a high potential barrier on one side of the silicide and are collected over a low barrier on the other. Recent results [2] have shown that current gains can be in excess of 40 in structures having a-CrSi2 bases ∼1 nm thick.Here we outline the relatively simple technology used to make these devices and examine their performance as phototransistors in which the photo-current is amplified by hot-electron transistor action. The speed of response can be maximised by operating the phototransistor with high electric field across the collector since it is the transit time of the photo-induced carriers that determines the response time. We show that these devices provide a useful new active element for large area amorphous silicon electronics.

Determination of a High Potential Barrier Hindering Internal Rotation in 2-Methylcyclopentanone and α-Methyl-γ-Butyrolactone by Microwave Fourier Transform Spectroscopy

The microwave spectra of α-methyl-γ-butyrolactone and 2-methylcyclopentanone have been reinvestigated using microwave Fourier transform spectroscopy. A-E splittings due to internal rotation of the methyl group have been observed in the ground and several vibrationally excited states for both molecules. From an internal-axis-method analysis of these splittings, values of the methyl group internal rotation barrier of 2.61 kcal mol-1 for α-methyl-γ-butyrolactone and 2.41 kcal mol-1 for 2-methylcyclopentanone have been obtained.