Ultraviolet-assisted pulsed laser deposition: a new technique for the growth of thin oxide films at medium and low temperatures

Abstract

The crystallinity, stoichiometry and optical and electrical properties of thin Y<SUB>2</SUB>O<SUB>3</SUB>, ZnO and Ba<SUB>0.5</SUB>Sr<SUB>0.5</SUB>TiO<SUB>3</SUB> films grown using an in situ ultraviolet (UV)- assisted pulsed laser deposition (UVPLD) technique have been studied. With respect to films grown by conventional PLD under similar conditions but without UV illumination, the UVPLD grown films exhibited better quality, especially for lower substrate temperatures. They also contained less physisorbed oxygen than the conventional PLD grown layers. These improvements can be explained by the action of several factors. Firstly, deep UV photons and ozone ensure a better in situ cleaning of the substrate. Secondly, the presence during the ablation-growth process of more reactive gaseous species like ozone and atomic oxygen formed by photodissociation of molecular O<SUB>2</SUB> promotes the oxygenation of the films. Thirdly, absorption of UV photons by adatoms could result in an increased surface mobility. All these factors have a beneficial effect upon crystalline growth, especially for moderate substrate temperatures, where the thermal energy available for the process is rather limited.