Growth studies of Ba(1-x)K(x)BiO3-delta thin films by pulsed-laser deposition

A study is presented on pulsed-laser deposition of thin films of Ba1−xKxBiO3−δ (BKBO) and its parent compound BaBiO3−δ (BBO). BKBO is a non-cuprate high-TC (30 K) superconductor with relatively long coherence length (5 nm) and shows BCS like behavior. Therefore, BKBO is an attractive candidate for superconducting electronic device applications. Furthermore, the insulator BBO is suitable as barrier material. We deposited BKBO thin films from potassium-overdoped targets (Ba0.6K0.8BiO3−δ) in order to compensate for the volatility of potassium in our efforts to obtain superconducting Ba1−xKxBiO3−δ (x=0.3–0.4) thin films. The deposition parameters and annealing procedure were optimized to achieve good quality films. Especially, the substrate temperature is important, because it influences simultaneously the content of potassium and crystallinity of the growing film. This combination hampers the optimization, because they cannot be controlled independently. Furthermore, we will present our first attempts to control the stoichiometry using intervals of different pulsed-laser repetition rates.