Microstructural and magneto-transport characterization of Bi$_{\mathrm{2}}$Se$_{\mathrm{x}}$Te$_{\mathrm{3-x}}$ topological insulator thin films grown by pulsed laser deposition method*

Bi$_{\mathrm{2}}$Se$_{\mathrm{x}}$Te$_{\mathrm{3-x}}$ topological insulator thin films were grown on Al$_{\mathrm{2}}$O$_{\mathrm{3\thinspace }}$(0001) substrate by pulsed laser deposition (PLD). XRD and other structural characterization measurements confirm the growth of the textured Bi$_{\mathrm{2}}$Se$_{\mathrm{x}}$Te$_{\mathrm{3-x}}$ thin films on Al$_{\mathrm{2}}$O$_{\mathrm{3\thinspace }}$substrate. The magneto-transport properties of thick and thin Þlms were investigated to study the effect of thickness on the topological insulator properties of the Bi$_{\mathrm{2}}$Se$_{\mathrm{x}}$Te$_{\mathrm{3-x\thinspace }}$films. A pronounced semiconducting behavior with a highly insulating ground state was observed in the resistivity vs. temperature data. The presence of the weak anti-localization (WAL) effect with a sharp cusp in the magnetoresistance measurements confirms the 2-D surface transport originating from the TSS in Bi$_{\mathrm{2}}$Se$_{\mathrm{x}}$Te$_{\mathrm{3-x}}$ TI films. A high fraction of surface transport is observed in the Bi$_{\mathrm{2}}$Se$_{\mathrm{x}}$Te$_{\mathrm{3-x}}$ TI thin films which decreases in Bi$_{\mathrm{2}}$Se$_{\mathrm{x}}$Te$_{\mathrm{3-x}}$ TI thick films. The Cosine ($\theta )$ dependence of the WAL effect supports the observation of a high proportion of 2-D surface state contribution to overall transport properties of the Bi$_{\mathrm{2}}$Se$_{\mathrm{x}}$Te$_{\mathrm{3-x}}$ TI thin films. Our results show promise that high quality Bi$_{\mathrm{2}}$Se$_{\mathrm{x}}$Te$_{\mathrm{3-x}}$ TI thin films with significant surface transport can be grown by PLD method to exploit the exotic properties of the surface transport in future generation spintronic devices.