Seebeck and resistivity measurements are made on thin film CdS and Zn_xCd_1-xS samples in an apparatus of original design over a temperature range from near liquid nitrogen temperature to room temperature. The temperature dependence of mobility and carrier concentration is studied in CdS films of varying thicknesses (3 µm to 14.0 µm) and in Zn_xCd_1-xS films of varying zinc content (0 ≤ x ≤ .35) . Scattering is found to be grain boundary dependent in all films except the thinest CdS film measured (3.0 µm) in which lattice scattering dominates. The grain boundary barrier height increases with film thickness in CdS films due to a decrease in carrier concentration as film thickness increases making electron traps at the grain boundary influential. As the zinc concentration is increased the carrier concentration decreases and the grain boundary barrier height increases as seen in the CdS films. / Master of Science