Growth optimization and crossover of transport mechanisms in Bi2Se3 thin films.

We report the growth, structural characterization, and transport studies of Bi2Se3 thin film on single crystalline silicon (Si), Si/SiO2, quartz, and glass substrates by thermal evaporation method. Our results show that 300 0 C is the optimum substrate temperature to obtain the c-axis (0 0 1) oriented Bi2Se3 films on all the substrates. The film grown on the Si substrate has the minimum crystalline disorder. The EDX results show that film on Si substrate is bismuth deficient, the film on Si/SiO2 substrate is selenium deficient, and the film on quartz substrate is near perfect stoichiometric providing a way to tune the electronic properties of Bi2Se3 films through substrate selection. The film grown on quartz show the highest mobility (2.7×10 4 cm 2 /Vs) which drops to 150 cm 2 /Vs for Si, 60 cm 2 /Vs for Si/SiO2, and 0.9 cm 2 /Vs for glass substrate. Carrier concentration is n-type for Bi2Se3 films on Si (~10 18 cm -3 ), quartz (~10 18 cm -3 ) and Si/SiO2 (~10 19 cm -3 ) substrate with a clear indication of frozen out effect around 50 K for Si/SiO2 and Si substrate. Longitudinal resistivity of Bi2Se3 film on Si/SiO2 substrate shows different behavior in three different temperature regions: a temperature dependent resistivity region due to electron-phonon scattering, a nearly temperature independent resistivity region due to electron-phonon and electron-ion scattering, and a quantum coherent transport region.