Effect of substrate temperature and oxygen pressure on the microstructure of thin YBa2Cu3O7-δ film deposited on MgO by pulsed-laser ablation

The microstructure of thin YBa2Cu2O7-δ films, prepared by pulsed-laser ablation, at a range of oxygen pressures and substrate temperatures has been investigated. The thin films were deposited directly onto specially prepared, electron-transparent thin-foil substrates of (001)-oriented MgO. Independent variation of the two parameters was found to affect the microstructure of the thin film. For example, at low substrate temperatures (600°C), the film was found to consist of small (<50 nm diam.) interconnected islands, while at higher substrate temperatures (750°C), the film consisted of much larger (> 100 nm diam.) isolated islands. These larger islands were faceted parallel to low index planes (e.g. {100} and {110}). The differences observed in the microstructure of films grown at the two temperatures was related to the degree of mobility of the ablated species on the substrate surface.