Type: 
Senior Thesis Presentation
Date-Time: 
Thursday, May 22, 2014 - 14:30 to 15:15
Location: 
Weniger 212
Event Speaker: 
Rodney Snyder
Local Contact: 
Tate
Abstract: 

The Van der Pauw method for transport measurements of conductivity and carrier concentration were tested on indium-tin-oxide (ITO) films and silicon wafers, and then implemented on Cu10-xAgxZn2Sb4S13 thin films. ITO was used as a test case for high temperature transport measurements because it a well characterized semi-metal. The mobility of ITO as a function of temperature is for a = -0.3. This proportionality is consistent with scattering dominated by phonon. Silicon was measured as a test case because it is a well characterized semiconductor that can be controllably doped n and p-type. Rectangular wafers were measured: 620-μm thick, <100>-oriented n-type Si and <111> 650-μm thick, <111>-oriented p-type Si. For p-type Si, ρ = 21 mΩcm and p = 6.25x1018 cm-3, for n-type Si, ρ = 14 mΩcm and n = 9.5x1017 cm-3. The power factors for n- and ¬p-doped silicon were measured at 3.0·10-3 W/mK2.
The room-temperature resistivity and Seebeck coefficient of thin film variants of the mineral tetrahedrite Cu12Sb4S13 were measured. In bulk form, tetrahedrite has shown promise as a good thermoelectric material. Thin films of Cu10-xAgxZn2Sb4S13 with a thickness of 360 nm were produced by e-beam deposition. The Seebeck coefficients ranged from 10 to 113 μV/K and the resistivity from 8 to 50 mΩcm. Together, these values yield power factors S2/ρ ranging from 10-7 to 10-4 W/mK2, approaching the range of their bulk counterparts.