L. Enrique Sansores

Band structure and bulk modulus calculations of germanium carbide

Band-structure calculations of germanium carbide (GeC) show that it is a new indirect wide band gap semiconducting material, which crystallizes in both cubic and hexagonal phases. Through the density functional and total-energy technique in the generalized gradient approximation, the two polytypes 3C and 2H of GeC were studied. According to our calculations, it is a hard material with a percentage of covalency of about 80–90%. Important energy gaps were determined. The bulk modulus, density of states, and charge density were calculated. For the bulk modulus calculations, Murnaghan’s equation of state was used under elastic deformation to measure hardness. Our calculations showed that this semiconducting material crystallizes in zincblend ( E g = 1.76 eV) and wurtzite ( E g = 2.5 eV) structures.

Dependency of reactive magnetron-sputtered SiC film quality on the deposition parameters

Abstract SiC thin films have been prepared by using RF reactive magnetron sputtering (RF-RMS). The deposition parameters have been varied over a wide range to optimize the quality of the films; substrate temperature from 700 to 1000°C, Ar/CH 4 composition from 80:20 to 50:50 and RF power from 100 to 200 W. The samples have been characterized by X-ray diffraction, Rutherford backscattering, profilometry, FTIR spectroscopy and ellipsometry. The results show that good quality silicon carbide films can be prepared by using the RF-RMS technique.

The energy gap in a-Si1 − xCg: H alloys

Abstract The electronic structure of amorphous tetrahedral clusters of the type a-Si 1 − x C g : H are studied using the pseudopotential SCF Hartree-Fock approximation. The reduced energy gap isgiven by E g r ( x ) − 1 + 0.84 x for x ⩽ 0.5, whereas experimentally E g r ( x ) = 1 + 0.96 x . For x ⩾ 0.5 the dip in the gap value reported experimentally is verified.

Calculations of the Electronic Structure of Vacancies in a-Si:H

The electronic structure of random clusters has been used in the literature as representative of the electronic structure of random solids. In this work a calculation of the local density of states (LDOS) and charge density contours for clusters of the type XSi 20 H 28 with X an Si atom, a vacancy or 4 hydrogen atoms, has been carried out. The method used was a pseudopotential SCF Hartree-Fock and the HONDO program. It is found that the generation of a vacancy in the center of the cluster (removal of the central Si atom), introduces p-like states in the energy gap of the LDOS for the region near the center of the cluster. The saturation of the dangling bonds of the vacancy with 4 hydrogen atoms removes the states within the gap. These results are also borne out by the charge density contours, thereby reinforcing the importance of amorphous cluster calculations in the understanding of the electronic structure of amorphous solids.