Award Date

8-2011

Degree Type

Thesis

Degree Name

Master of Science in Electrical Engineering (MSEE)

Department

Electrical and Computer Engineering

First Committee Member

Rama Venkat, Chair

Second Committee Member

Nathan Newman

Third Committee Member

Thomas Hartmann

Graduate Faculty Representative

Ravhi Kumar

Number of Pages

113

Abstract

Thermoelectric devices can generate electrical power as a result of their ability to produce electrical currents in the presence of thermal gradients. They can also produce refrigerative cooling when electrical power is supplied to them. Among the potential semiconducting silicides, CrSi 2 is attractive because of its high thermal and chemical stability and its potential for thermoelectric application. CrSi2 /SiO2 thin-film structures were prepared using RF sputtering. As deposited and annealed (300°C to 600°C) thin films were characterized for their structural, electrical, and thermoelectric transport properties. As-sputtered CrSi 2 film is amorphous at room temperature and crystallizes around 300°C independent of thickness. Resistivity of the as-deposited 1ìm films is 1.20 mΩ-cm, whereas, the annealed films were not electrically conducting as a result of the formation of cracks in the film. The measured Seebeck voltage of the 1ìm films is markedly enhanced upon annealing and reaches a value of 81μV/K; close to that of bulk CrSi 2 . The 0.1μm-thick film exhibit an increase in the resistivity up to 0.9mΩ-cm upon annealing at 300°C, which drops for higher temperature anneals. This behavior is not well-understood. The Seebeck voltages of the 0.1μm thin films increase with annealing temperatures, reaching a maximum value of 62μV/K. Thermoelectric power factors for 0.1 μm thin films exhibit a similar behavior to that of the Seebeck coefficients; increasing with temperature and reaching a plateau value of 10 -3 W/(K2 m) at around 400°C to 450°C. These results suggest that annealed thin films of thicknesses in the range of 0.1μm are more suitable for device applications when glass substrates are employed. In order a deposit ternary and higher order alloys, a three gun sputtering system was designed, built and tested for its level of vacuum levels and cleanliness. The tests showed that the three-gun sputtering system is of vacuum levels of 10 -9 Torr and shows extremely low level of impurities and is ready for future sputtering works in this area.

Keywords

Chromium compounds; Semiconductor films -- Analysis; Silicides; Thermal electromotive force; Thermoelectric materials; Thin films — Electric properties

Disciplines

Electrical and Computer Engineering | Electronic Devices and Semiconductor Manufacturing | Semiconductor and Optical Materials

Language

English


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