Narrow Results

Experimental measurements of photoresistivity under terahertz (THz) radiation in low magnetic fields at conditions of cyclotron resonance (CR) in two-dimensional electron system (2DES) of GaAs/AlGaAs nanostructures are presented and discussed. We report the experimental discovery of "CR-vanishing effect" (CRV) in GaAs/AlGaAs heterostructures with high mobility as a well-defined gap on CR-line that is independent on incident THz power. Our analysis shows that the CRV may appear in systems with well correlated state of 2D electrons such as plasma waves and others. Fundamental nature of these correlated states of electrons in 2DES is discussed. Future THz detectors utilizing the new correlated states in 2DES may expand horizons for supersensitive detection in sub-THz and THz frequencies ranges.

By using reactive magnetron sputtering system, titanium dioxide thin films were fabricated onto quartz substrate, and then modified by Ge and Si atoms that were introduced with ion implantation method. XRD, AFM, XPS, and UV-vis were used to characterize these films, and X-ray photoelectron spectroscopy (XPS) was adopted to examine the atomic chemical states of implanted titanium dioxide thin films. The results show that there are Ge and silicon oxides precipitations in TiO₂ matrices. The implanted Ge + Si thin film exhibits an intense absorption band within visible region, which will further benefit its practical applications.

Influence of large radiation defects — disordered regions on photoconductivity of semiconductors Ge and Si, compensated as a result of an irradiation with fast neutrons and 1 GeV protons, is investigated. For the first time, the combined role of disordered regions and a large-scale potential relief in photoelectrical properties of Ge and Si, irradiated by high energy particles is defined. The model of photoconductivity that takes into consideration disordered regions as specific sensitizing recombination centers and allows formation of the spatial potential relief is developed.

Hollow germanium tubular nanostructures have been obtained by a hydrothermal process at a temperature of 400°C and pressure of 7 MPa with quick cooling to room temperature. Transmission electron microscopy (TEM) and high-resolution transmission electron microscopy (HRTEM) show that the germanium tubular nanostructures are polycrystalline and have open-end structures at the tips. The diameter of germanium tubular nanostructures is about 40–70 nm and the inner pore size is about 10 nm in average. We propose the rolling mechanism for the formation of tubular nanostructures from lamellar nanostructures to explain the possible formation process of germanium tubular nanostructures.

The ballistic performance of Si and Ge nanowire (NW) is compared in this study. Current–voltage characteristic is obtained by self-consistently solving the nonequilibrium Green’s function (NEGF) transport equation with Poisson’s equation. The result is obtained at $⟨001⟩$ channel orientation. Simulation result shows Ge NW gives higher ON-state current than Si NW, when OFF-state current is made equal by gate metal work function engineering. However, at subthreshold region, performance of NW FET for both material is almost identical. The intravalley and intervalley electron–phonon scattering effect is also calculated using the deformation potential theory and the self-consistent Born approximation. It is found that electron–phonon scattering effect is more pronounced at ON-state of Si NW FET. The ballistic current decreases with the decrease in diameter of the Si NW FET due to electron–phonon scattering.