Antimony Telluride Thin Films Research Articles

In-situ monitoring of the growth of Bi2 Te2 and Sb2 Te3 films and Bi2 Te3-Sb2 Te3 superlattice using spectroscopic ellipsometry

In this work, we present in-situ monitoring of the growth of bismuth telluride (Bi2Te3) and antimony telluride (Sb2Te3) thin films as well as Bi2 Te3-Sb2Te3 superlattice using a spectroscopic ellipsometer (SE). Bi2Te3 and Sb2 Te3 films were grown by metalorganic chemical vapor deposition (MOCVD) at 350 C. A44-wavelength ellipsometer with spectral range from 404 nm to 740 nm was used in this work. The optical constants of Bi2 Te3 and Sb2Te3 at growth temperature were determined by fitting a model to the extracted in-situ SE data of optically thick Bi2 Te3 and Sb2 Te3 films. Compared to the optical constants of Bi2 Te3 and Sb2 Te3 at room temperature, significant temperature dependence was observed. Using their optical constants at growth temperature, the in-situ growth of Bi2 Te3 and Sb2 Te3 thin films were modeled and excellent fit between the experimental data and data generated from the best-fit model was obtained. In-situ growth of different Bi2 Te3-Sb2 Te3 superlattices was also monitored and modeled. The growth of Bi2 Te3 and Sb2 Te3 layers can be seen clearly in in-situ SE data. Modeling of in-situ superlattice growth shows perfect superlattice growth with an abrupt interface between the two constituent films.

Preparation and characterization of p-type Sb2Te3 and n-type Bi2Te3 thin films grown by coevaporation

p -type antimony telluride thin films and n-type bismuth telluride thin films have been deposited by coevaporation on glass substrates. The conditions for deposition have been investigated as a function of substrate temperature (Ts), flux ratio (Fr=F(Te)/F(Sb, Bi)) and optimized to achieve a high thermoelectric power factor. The quality of deposited films, e.g. structure, composition and morphology, has been examined by x-ray diffraction, energy dispersive x-ray analysis, flame atomic absorption spectroscopy, and with an atomic force microscope. The thermoelectric properties of the thin films have been evaluated by room temperature measurement of the Seebeck coefficient, Hall coefficient, and electrical resistivity. Both the crystallinity and the transport properties are strongly affected by nonstoichiometry with the highly stoichiometric samples exhibiting a high crystallinity and high thermoelectric power factor. The Seebeck coefficient and electrical conductivity of p-type Sb2Te3 thin film (αp, σp) and n-type Bi2Te3 thin films (αn, σn) were found to be about 185 μV/K, 0.32×103 Ω−1 cm−1 and −228 μV/K, 0.77×103 Ω−1 cm−1, respectively. The results indicate that good quality antimony telluride and bismuth telluride thin films grown by coevaporation are promising candidate materials for use in the fabrication of micro-Peltier modules.

Structure and electrical properties of vacuum-deposited antimony telluride thin films on an amorphous substrate

Sb2Te3 thin films, 50–109 nm thick, have been prepared by vacuum evaporation on to quartz substrates. Electrical properties of as-deposited and annealed films show that the activation energy is thickness dependent. Optical measurements indicate that there is an indirect transition having an energy of 1.9 eV. Transmission electron micrographs show the fine grains of the deposit.

A thermodynamic study of gas transport in the growth of antimony telluride thin films

In order to determine the growing conditions of thin films of Sb 2Te 3 in the hot wall epitaxy (HWE) technique, a thermodynamic model for the sublimation of the Sb 2Te 3 phase was studied. The equilibrium constant was calculated, and the expressions for the fluxes and pressures of the components were determined. From these results, equations for the sticking coefficient and the deposition rate, expressed as functions of the source and substrate temperatures only, were formulated.