Year

2011

Degree Name

Master of Engineering - Research

Department

Institute for Superconducting and Electronic Materials

Abstract

Bismuth telluride and antimony telluride alloys are the most widely studied and used thermoelectric materials because they have higher thermoelectric performances than other materials at room temperature. Currently, the low-dimensional thermoelectric materials win the attention of many researchers.

Thin films of n-type Bi2Te3 were fabricated on glass substrates at room temperature using pulsed laser deposition. Samples were characterized by using X-ray diffraction, scanning electron microscopy, Raman spectroscopy, and a physical properties measurement system. The XRD and Raman results show that crystalline films can be easily achieved at room temperature, and all films have a preferred crystal growth texture along the (015) direction. SEM indicates that the films are high-quality and smooth. The Seebeck coefficient, electrical resistivity, and magnetoresistance were measured over wide ranges of temperature and magnetic field. It was found that Seebeck coefficient of the films were significant enhanced after annealing process.

Bi0.5Sb1.5Te3 thin films were deposited on glass substrates by pulsed laser deposition method at room temperature. Annealing effect on properties of the films was studied by structural, morphology and physical characterizations. It was found that the as-grown amorphous film crystallizes at annealing temperature of 473 K. A semiconductor-metal transition was observed in annealed films. A linear magnetoresistance (MR) was investigated in the annealed films in a magnetic field up to 13 T without saturation at low temperature.

Bi2Te3 thin films were prepared by pulsed laser deposition on PVC, Si(111) and LaAlO3(100) substrates at room temperature. All the samples are single phase. The films on LaAlO3(100) substrates possess better crystallization than those on Si(111). The surface of as-grown films on PVC substrate is rough, others are smooth. The resistivity of the film on Si(111) substrate is much larger than the resistivity of the films on other substrates. The resistivity of the thin films decreases gradually when the annealing temperature increases from room temperature to 523 K. Negative values of thermopower are obtained in the films on Si(111) substrate.

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