Signature of weak-antilocalization in sputtered topological insulator BiSe thin films with varying thickness.

We report a low-temperature magneto transport study of BiSe thin films of different thicknesses (40, 80 and 160 nm), deposited on sapphire (0001) substrates, using radio frequency magnetron sputtering technique. The high-resolution x-ray diffraction measurements revealed the growth of rhombohedral c-axis {0003n} oriented BiSe films on sapphire (0001). Vibrational modes of BiSe thin films were obtained in the low wavenumber region using Raman spectroscopy. The surface roughness of sputtered BiSe thin films on sapphire (0001) substrates were obtained to be ~ 2.26-6.45 nm. The chemical and electronic state of the deposited BiSe was confirmed by X-ray photoelectron spectroscopy and it showed the formation of BiSe compound. Resistivity versus temperature measurements show the metallic nature of BiSe films and a slight up-turn transition in resistivity at lower temperatures < 25 K. The positive magneto-resistance value of BiSe films measured at low temperatures (2-100 K) confirmed the gapless topological surface states in BiSe thin films. The quantum correction to the magnetoconductivity of thin films in low magnetic field is done by employing Hikami-Larkin-Nagaoka theory and the calculated value of coefficient 'α' (defining number of conduction channels) was found to be 0.65, 0.83 and 1.56 for film thickness of 40, 80 and 160 nm, respectively. These observations indicate that the top and bottom surface states are coupled with the bulk states and the conduction mechanism in BiSe thin films varied with the film thicknesses.