Charge compensation by phase segregated Sb2Se3 phase in Bi1.95Sb0.05Se3 topological insulator by laser fluence

Abstract

We report the charge compensation in topological insulator thin films due to the laser fluence-induced segregation of the Sb2Se3 phase. Sb doped Bi2Se3 films were deposited on commercial Si substrates coated with 300 nm of amorphous SiO2 using the Pulsed Laser Deposition technique at different laser fluence of 1.25 J-cm-2, 1.87 J-cm-2, 2.75 J-cm-2, and 3.25 J-cm-2. The grazing x-ray diffraction measurements revealed the growth of rhombohedral Bi2Se3 films on SiO2 with additional peaks corresponding to the Sb2Se3 peaks. The phase fraction of the segregated Sb2Se3 systematically reduces as the laser fluence increases. The magnetoresistance measured at temperatures 3K-20K was compared across different samples deposited at various laser fluences. The sample deposited at 1.25 J-cm-2 exhibits a bulk-insulating nature with an order decrease in the carrier density. The weak antilocalization quantum correction to the magneto conductivity was analyzed using the Hikami Larkin Nagaoka Theory. As the laser fluence increases the deduced value of coefficient alpha, number of conduction channels was found to be 0.5, 1.5, 2.5, and 5.0, and the quantum phase coherence length lphi ranges from 10 nm to 150 nm. The power factor gamma of the temperature dependence of lphi also varies as 0.37, 0.45, 0.69, and 0.92, respectively. The charge compensation due to the non-TI, ptype Sb2Se3 phase is believed to cause the reduction in the bulk carrier density n, and enhanced surface state contribution.