Self-limiting adsorption and in situ optical monitoring for atomic layer epitaxy of oxide superconductors layer epitaxy of oxide superconductors

Abstract Preliminary steps toward atomic layer epitaxy of YBa 2 Cu 3 O x (CVD) which may be a suitable method for atomic layer epitaxy since the sticking probability of precursors to the growing substrate surface can be controlled digitally. The feasibility of self-limiting adsorption of precursors for CVD of YBa 2 Cu 3 O x was investigated using an ultrahigh vacuum CVD apparatus. Experimental observation using a mass analyzer of the amount of adsorbed species for various adsorption times, gas flow rates, and temperatures provides possible, although not conclusive, evidence of self-limiting adsorption. We applied in situ optical diagnostics for the first time to layer-by-layer CVD of YBa 2 Cu 3 O x . Variations in reflectance signals of a 780 nm diode laser from the growing surface were observed, similar to reflectance high-energy electron diffraction oscillation, upon sequential supply of precursors and oxygen. The amplitude of the change in reflectance was surprisingly large. The transient time and steady-state reflectance level depend on the species of the surface. A possible mechanism of reflectance oscillation is discussed.