Carrier transport in porous silicon

Carrier transport in porous silicon layers has been studied by the time-of-flight method in the strong injection mode at temperatures T=290–350 K and electric field strengths F=(1.5–7)×10⁴ V cm^?1. The electron and hole drift mobilities μ_e≈2×10^?3 cm² V^?1 s^?1 and μ_h≈6×10^?4 cm² V^?1 s^?1 were obtained at T=292 K and F=4×10⁴ V cm^?1. An exponential temperature dependence of drift mobility with activation energy of ～0.38 and ～0.41 eV for, respectively, electrons and holes was established. It is shown that the type of time dependences of the photocurrent associated with carrier drift and the superlinear dependence of the transit time on the reciprocal of the voltage applied to a sample allow use of the concept of space-charge-limited currents under the conditions of anomalous dispersive transport. The experimental data are accounted for in terms of the model of transport controlled by carrier trapping into localized states with energy distribution near the conduction and valence band edges described by an exponential function with a characteristic energy of ～0.03 eV.     

Voltage oscillations in the case of the switching effect in thin layers of Ge–Sb–Te chalcogenides in the current mode

The I–V characteristics obtained for layers of chalcogenide vitreous semiconductor of the Ge–Sb–Te system in the current-generator mode are investigated. The instability region, i.e., the region of conductivity oscillations, observed in the case of the switching effect under conditions of a set current is revealed. The key parameters describing these oscillations and the conditions of their occurrence are investigated in detail. Analysis of the obtained data shows that, to explain the oscillations in the instability region, it is necessary to take into account an increase in the current density and the process of heat exchange between the current filament that arises in the film upon switching and the environment.     

Improving metal-cutting precision by attention to tool-replacement systems

The contribution of tool error to machining precision is examined.     

Coadsorption of ascorbic acid and α-tocopherol antioxidants on partially trimethylsilylated silica surface

The interaction of hydrophilic-hydrophobic silica with α-tocopherol and ascorbic acid is investigated. Desorption of antioxidants from the silica surface into water, ethanol, and Vaseline oil is studied. Ascorbic acid and α-tocopherol are found to be adsorbed on the hydrophilic and hydrophobic parts of the silica surface, respectively. The antioxidants are shown to adsorb-desorb independently.     

A television endoscopic system with a heat-resistant silicon carbide mirror

A heat-resistant television endoscopic system, based on a mirror made of a wideband-gap semiconductor (silicon carbide), is designed. The system ensures visualization of studied objects in a temperature range of 20–1000°C. The wavelet functions applied for processing low-contrast images of objects allowed us to increase their quality and refining.