Motivated by recent experimental observations of Tongay et al. [Nano Lett. 12, 5576 (2012)] we show how the electronic properties and Raman characteristics of single layer MoSe 2 are affected by elastic biaxial strain. We found that with increasing strain: (1) the E and E Raman peaks (E 2g and E 1g in bulk) exhibit significant redshifts (up to ∼30 cm −1 ), (2) the position of the A 1 peak remains at ∼180 cm −1 (A 1g in bulk) and does not change considerably with further strain, (3) the dispersion of low energy flexural phonons crosses over from quadratic to linear, and (4) the electronic band structure undergoes a direct to indirect band gap crossover under ∼3% biaxial tensile strain. Thus the application of strain appears to be a promising approach for a rapid and reversible tuning of the electronic, vibrational, and optical properties of single layer MoSe 2 and similar MX 2 dichalcogenides.

We have investigated the annealing effect on the structural, optical and electrical properties of copper oxide films prepared on glass substrates by chemical deposition. The films were annealed in air for different temperatures ranging from 200 to 350 • C. X-ray diffraction patterns showed that the films as-deposited and annealed at 200 and 250 • C are of cuprite structure with composition Cu 2 O. Annealing at 300 • C converts these films to CuO. This conversion is accompanied by a shift in the optical band gap from 2.20 eV to 1.35 eV. Also this conversion was obtained by the dc electrical conductivity and FTIR spectroscopy measurements.

No abstract

We presented the results of optical and electrical studies of the properties of hydrogenated amorphous silicon (a-Si:H) film which was prepared by hot wire method. Using transmittance measurements, the dielectric constant of the a-Si:H was determined. The temperature-dependent conductivity was measured using the two-point probe method in the temperature range 115–326 K. It was shown that the temperature-dependent conductivity can be well explained by the nearest-neighbor hopping conduction and the Efros–Shklovskii variable-range hopping conduction models. A clear transition from the nearest-neighbor hopping conduction mechanism to the Efros–Shklovskii variable-range hopping conduction mechanism was also observed. The transition between two conduction regimes and characteristic hopping temperatures, as well as the complete set of parameters describing the properties of the localized electrons (the localization length, the hopping energy, the hopping distance, the width of the Coulomb gap, and the value of the density of states at the Fermi level) were determined.

No abstract