The Diffusion Isotope Effect and Diffusion Mechanism in Liquid Cu-Ag and Cu-Ni Alloys

In this paper, the diffusion isotope effect and diffusion mechanism are investigated by means of molecular dynamics simulations in two liquid alloys, Ni-Ag and Ni-Cu. The values for the diffusion isotope effect parameter allow for the estimate of the number of atoms which are moving cooperatively in a basic diffusion event as experienced by a given atomic species. It is shown that the composition dependence of ND is typically very small. However, the temperature dependence of this parameter is much more pronounced. In addition, it is shown that, on average, in these alloys and temperatures considered, ND is limited to the range: 5<ND<17. This is consistent with results of molecular dynamics simulations on the average coordination number calculations. This would suggest that, together with a given atom, depending on temperature, the neighbouring atoms are all involved in the basic diffusion event.

Anomalous Nernst effect dependence on composition in Fe100-X Rh X alloys

We studied the anomalous Nernst effect in CsCl-type Fe100-X Rh X (X = 45, 48, 50, 52, 54, 60) with a thickness of 50 nm deposited on a thermally oxidized Si substrate. Samples with X < 48 certainly have a ferromagnetic phase, exhibiting the anomalous Nernst effect. The composition dependence of the anomalous Nernst coefficient S yx agreed with the transverse thermoelectric conductivity α yx. |S yx | and |α yx | were maximized at X = 48, which has a ferromagnetic state close to the phase transition state. The maximization of |α yx | at X = 48 can be explained using band structure-based calculations , where |α yx | rapidly increases near the phase transition.

Al Composition Dependence of Band Offsets for SiO2 on α-(AlxGa1-x)2O3

Valence band offsets were measured by X Ray Photoelectron Spectroscopy for SiO2 deposited by Atomic Layer Deposition on α-(AlxGa1-x)2O3 alloys with x= 0.26-0.74 grown with a continuous composition spread to enable investigations of the band alignment as a function of the alloy composition. From measurement of the core levels in the alloys, the bandgaps were determined to range from 5.8 eV (x=0.26) to 7eV (x=0.74). The valence band offsets were -1.2 eV for x=0.26, -0.2 eV for x=0.42, 0.2 eV for x=0.58 and 0.4 eV for x=0.74. Given the bandgap of the SiO2 was 8.7 eV, this led to conduction band offsets of 4.1 eV (x=0.26) to 1.3 eV (x=0.74). The band alignments were nested for x>0.5 , but at lower Al contents the conductions band offsets were negative, with a staggered band alignment. This shows the challenge of finding appropriate dielectrics for this ultra-wide bandgap semiconductor system.

Composition Dependence of Electronic, Elastic, and Polarization Properties of Wurtzite InxGa1-xN and CdxZn1-xO Ternary Alloys

We report the results of density functional theory calculations of several properties of wurtzite-structured InGaN and CdZnO alloys. It is shown that the investigated properties, including the internal parameter, bandgap, mechanical moduli, and electric polarization are nonlinear functions of alloy composition, as they deviate from the linear behavior predicted by Vegard’s law. Based on these results, InGaN and CdZnO are materials whose properties can be tuned via In and Cd concentrations. The spontaneous and piezoelectric polarizations considerably affect the properties of alloys-based devices due to the huge electric fields that build up at the heteroineterfaces. In this work we propose a method of controlling such fields by employing the composition dependence of the total polarization. We support this proposal by showing that, in the case of InGaN, an optimal alloy composition can be found that effectively reduces the polarization-induced electric fields, thereby improving the efficiency of optoelectronic applications.