Growth and characterization of Ba$_{8}$Ga$_{16}$Ge$_{30}$ Type I clathrate thin films grown by pulsed laser deposition

Ba$_{8}$Ga$_{16}$Ge$_{30 }$thin films were successfully grown on Si (100) substrates using pulsed laser deposition process. Clathrates are studied for potential thermoelectric (TE) applications with few reports of thin film growth due to intrinsic difficulty in growing the caged structures in thin film form. Growth of stoichiometric Ba$_{8}$Ga$_{16}$Ge$_{30 }$thin films is complicated by non-congruent evaporation during the ablation process resulting in Ga or Ge deficient films, degrading their properties. We report a systematic study of the growth parameters for stoichiometric Ba$_{8}$Ga$_{16}$Ge$_{30 }$thin films. The laser ablated plasma plumes were analyzed using ICCD imaging and optical emission spectroscopy enabling optimization of growth parameters. Film thickness profiles of various target-substrate distances were plotted to estimate an optimum deposition rate. Surface morphologies and structure of the as-deposited films were examined using a scanning electron microscope and x-ray diffraction technique. This investigation provides a new direction towards the growth of high quality thin films for potential TE device applications.