Transport properties of undoped and NH_(3)-doped polycrystalline SnO_(2) with low background electron concentrations

摘要

A series of polycrystalline 1 μm thick SnO_(2) films were deposited onto borosilicate glass substrates by atmospheric pressure chemical vapor deposition. Unintentionally doped as-grown SnO_(2) layers had electron concentrations and mobility of 2-4×10~(17) cm~(-3) and 25-30 cm~(2)/V s, respectively. Potential barriers and trap concentrations were calculated to be 30 meV and 2.3×10~(12) cm~(-2), respectively. Upon N_(2)/vacuum annealing at 670 K for 15-20 min, the potential barrier height decreased to 8 meV and the electron mobility increased to 58 cm~(2)/V s. When doped with ammonia, the mobility of as-grown samples decreased to 0.5 cm~(2)/V s. The magnitude of the potential barriers varied, with ammonia doping, from 175 to 31 meV with trap densities of 4.7-1.2×10~(12) cm~(-3), respectively. Upon vacuum/N_(2) annealing at 670 K for 20 min, the electron mobilities of ammonia doped films recovered to 50-71 cm~(2)/V s, whereas the height of the potential barriers decreased to 3-4 meV with trap concentrations of 8-9×10~(11) cm~(-2). The observed changes in the electrical properties are well described by a double back-to-back Schottky barrier model.