Growth optimization and crossover of transport mechanisms in Bi2Se3thin films.

We report the growth, structural characterization, and transport studies of Bi2Se3thin film on single crystalline silicon (Si), Si/SiO2, quartz, and glass substrates by thermal evaporation method. Our results show that 300 °C is the optimum substrate temperature to obtain thec-axis (001) oriented Bi2Se3films on all the substrates. The film grown on the Si substrate has the minimum crystalline disorder. The energy-dispersive x-ray spectroscopy results show that film on Si substrate is bismuth deficient, the film on Si/SiO2substrate is selenium deficient, and the film on quartz substrate is near perfect stoichiometric providing a way to tune the electronic properties of Bi2Se3films through substrate selection. The film grown on quartz shows the highest mobility (2.7 × 104cm2V-1s-1) which drops to 150 cm2V-1s-1for Si, 60 cm2V-1s-1for Si/SiO2, and 0.9 cm2V-1s-1for glass substrate. Carrier concentration is n-type for Bi2Se3films on Si (∼1018cm-3), quartz (∼1018cm-3) and Si/SiO2(∼1019cm-3) substrate with a clear indication of frozen out effect around 50 K for Si/SiO2and Si substrate. Longitudinal resistivity of Bi2Se3film on Si/SiO2substrate shows different behavior in three different temperature regions: 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.