I. Shlimak

An experimental determination of the critical exponents at the metal-insulator transition

Abstract This work deals with a determination of the magnitude of the critical exponents and their ratio from an analysis of the temperature dependence of the conductivity and magnetoresistivity of doped Ge 〈 As 〉 with an impurity concentration making it an insulator near the metal-insulator transition. The values found are ˥˩ = 0.60 ± 0.04 , ξ = 1.38 ± 0.07, ξ ˥˩ = 2.3 ± 0.2 ; neither the critical exponents nor their ratio depend on compensation within 0

Neutron transmutation doping in semiconductors: Science and applications

Different aspects of neutron transmutation doping (NTD) of silicon and germanium are considered, with a special emphasis on the contribution by scientists of the Ioffe Physicotechnical Institute, Russian Academy of Sciences, to the solution of these problems. Fundamental studies related to determination of the cross sections of thermal-neutron capture by isotopes of semiconducting materials, annealing of radiation defects produced by fast reactor neutrons, and the use of NTD for probing the structure of the Ge impurity band are reviewed. Problems involved in industrial-scale production of NTD-Si, application of NTD-Si and NTD-Ge to fabrication of power thyristors, nuclear-particle and IR detectors, deep-cooled thermistors, and bolometers are discussed. The paper concludes with a consideration of prospects in the application of NTD-Si and NTD-Ge based on the use of materials with a controlled isotopic composition.

Fluctuation-stimulated variable-range hopping

A qualitatively new transport mechanism is suggested for hopping of carriers according to which the variable-range hopping (VRH) arises from the resonant tunneling between transport states brought into resonance by Coulomb potentials produced by surrounding sites with fluctuating occupations. A semiquantitative description of the hopping transport is given based on the assumption that fluctuations of energies of hopping sites have spectral density 1/f.

Structure and Spatial Distribution of Ge Nanocrystals Subjected to Fast Neutron Irradiation

The influence of fast neutron irradiation on the structure and spatial distribution of Ge nanocrystals (NC) embedded in an amorphous SiO2 matrix has been studied. The investigation was conducted by means of laser Raman Scattering (RS), High Resolution Transmission Electron Microscopy (HR-TEM) and X-ray photoelectron spectroscopy (XPS). The irradiation of Ge-NC samples by a high dose of fast neutrons lead to a partial destruction of the nanocrystals. Full reconstruction of crystallinity was achieved after annealing the radiation damage at 8000C, which resulted in full restoration of the RS spectrum. HR-TEM images show, however, that the spatial distributions of Ge-NC changed as a result of irradiation and annealing. A sharp decrease in NC distribution towards the SiO2 surface has been observed. This was accompanied by XPS detection of Ge oxides and elemental Ge within both the surface and subsurface region.

1f hopping noise in crystalline germanium

Abstract The low-frequency current noise (f = 0.1–50 Hz) has been measured in samples of p-Ge〈Ga〉 and n-Ge〈As〉 at temperatures 1.3–4.2 K, where the d.c. conductivity is determined by the nearest-neighbour-hopping mechanism of charge transport. It is shown that the spectral density of the noise has a 1 f - form and is proportional to the square of the applied voltage in accordance with the Hooge formula. However, the temperature dependence of the noise is much weaker than that of the d.c. resistivity, which is controlled by the concentration of mobile carriers in the critical network. Possible explanations of this effect are discussed.

Raman scattering and electrical resistance of highly disordered graphene

Raman scattering (RS) spectra and current-voltage characteristics at room temperature were measured in six series of small samples fabricated by means of electron-beam lithography on the surface of a large size

Switching phenomena in elastic polymer films

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Fabrication of uniform Ge-nanocrystals embedded in amorphous SiO2 films using Ge-ion implantation and neutron irradiation methods

industrial monolayer graphene film. Samples were irradiated by different doses of

Localization of Charge Carriers in Monolayer Graphene Gradually Disordered by Ion Irradiation

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Hopping conductivity in gated δ-doped GaAs: universality of prefactor

ion beam up to