YBa2Cu3O y liquid-phase epitaxy films of a orientation grown under ultra-low supersaturation caused by a homogeneous nucleation catastrophe.

Using liquid-phase epitaxy, a novel approach is reported for preparing a pure a-axis-oriented YBa2Cu3O y film ( a-film) on a (110) NdGaO3 substrate in ambient air, which is hard to achieve through conventional processes since its formation requires an extremely low supersaturation state. In the new process, instead of commonly used growth processes in a metastable zone, a-films were grown in an unstable zone of the Y-Ba-Cu-O solution. Under that circumstance, a homogeneous nucleation catastrophe occurred in the solution, leading to instantaneous consumption of most of the supersaturated Y solute. Thus a high degree of supersaturation rapidly relaxed to an ultra-low level. By controlling either the cooling rate or the growth temperature, a wide window for the formation of the a-film was gained. In principle, this new method should be universally valid for more crystal or film growth processes, particularly when an ultra-low supersaturation is required in solution. [ABSTRACT FROM AUTHOR]