In this work, stoichiometric Sb2Te3 thin films with various thicknesses were deposited on a flexible substrate using RF magnetron sputtering. The grain size and thickness effects on the thermoelectric properties, such as the Seebeck coefficient (S), electrical conductivity (σ), power factor (PF), and thermal conductivity (k), were investigated. The results show that the grain size was directly related to film thickness. As the film thickness increased, the grain size also increased. The Seebeck coefficient and electrical conductivity corresponded to the grain size of the films. The mean free path of carriers increases as the grain size increases, resulting in a decrease in the Seebeck coefficient and increase in electrical conductivity. Electrical conductivity strongly affects the temperature dependence of PF which results in the highest value of 7.5 × 10−4 W/m·K2 at 250°C for film thickness thicker than 1 µm. In the thermal conductivity mechanism, film thickness affects the dominance of phonons or carriers. For film thicknesses less than 1 µm, the behaviour of the phonons is dominant, while both are dominant for film thicknesses greater than 1 µm. Control of the grain size and film thickness is thus critical for controlling the performance of Sb2Te3 thin films.
We present the effects of In−N distribution and high pressure on the zincblende phase (0–5 GPa) of In
x
Ga
1−
x
As
0.963
N
0.037
(
x
=0.074, 0.111 and 0.148). Structural, electronic, and optical properties are analyzed, and it is found that non‐isotropic distribution of In−N (type C) possesses the minimum free energy for the InGaAsN conventional cell system. An increasing indium content reduces the formation enthalpy of InGaAsN. The formation enthalpy, conduction band minimum, strength of covalent bonds, and electron density differences in free space of InGaAsN are decreased under high‐pressure conditions. The dielectric performance and static permittivity of InGaAsN are lower than that of GaAs, for which the dielectric performance transforms to conductor performance at high frequency. The optimum photoabsorption coefficient is found at the composition of In
0.111
Ga
0.889
As
0.963
N
0.037
(3In−N), which very well relates to the literature.
We have investigated an effect of N incorporation on InGaAsN on Ge (001), which is proposed to be a part of the InGaP(N)/InGaAs/InGaAsN/Ge four-junction solar cell, and on its growth behavior. Results obtained from high resolution X-ray diffraction and Raman scattering demonstrated that high quality In0.11Ga0.89As1-yNy films with N (y) contents up to 5% were successfully grown on n-type doped Ge (001) substrate by metalorganic vapor phase epitaxy using low-temperature (500°C) GaAs buffer layer. As expectation, the In0.11Ga0.89As0.96N0.04 film is examined to be under lattice-matching condition. Anti-phase domains were observed for the film without N incorporation, which exhibits submicron-size domains oriented along the [110] direction on the grown surface. With increasing N content, the domains become less orientation, and present in a larger domain size. Based on results of transmission electron microscopy, a high density of anti-phase domains was clearly observed at the interface of low-temperature GaAs buffer layer and Ge substrate. On the other hand, it is found to drastically reduce within the N-contained InGaAsN region. Furthermore, the lattice-matched In0.11Ga0.89As0.96N0.04 film is well developed to reduce the density of anti-phase domains.
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