YBa₂Cu₃O_yliquid-phase epitaxy films ofaorientation grown under ultra-low supersaturation caused by a homogeneous nucleation catastrophe

Abstract

Using liquid-phase epitaxy, a novel approach is reported for preparing a pure a-axis-oriented YBa 2 Cu 3 O y film (a-film) on a (110) NdGaO 3 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.

The Orientation Transition and Control of REBaCu3Oy Films Grown by Liquid Phase Epitaxy

“…Those results seem to be inconsistent with the conventional thought that a low supersaturated state favors the a -axis oriented growth. Hence, unlike traditional methods which fabricate the a -films in the metastable zone, it is probable that the low supersaturation can be achieved in the unstable zone in the air by lowering the growth temperature ( T g ) . Additionally, it is also known that the metastable zone width could be influenced by the cooling rate ( R ) during the process, − and therefore, the ultralow supersaturation can be anticipated by adjusting the two growth parameters, i.e., T g and R .…”

“…Optical micrographs of the Y123 films grown in the flux of Ba:Cu = 3:5, at different temperatures and various cooling rates: (a) Sample I, T g = 1233 K, R = 0.3 K/min, presenting an a- axis oriented microstructure, characterized by elliptical spirals islands; (b) Sample II, T g = 1253 K, R = 2.2 K/min, presenting a c- axis oriented microstructure, characterized by square spiral islands; (c) Sample III, T g = 1248 K, R = 2.2 K/min, presenting an a/c- axis-mixed oriented microstructure, characterized by rectangularly shaped a- grains coexisting in the c -axis oriented matrix …”

“…XRD patterns of the Y123 films grown from the liquid with the Ba:Cu ratio of 3:5, at different temperatures and various cooling rates: (a) Sample I, T g = 1233 K, R = 0.3 K/min; (b) Sample II, T g = 1253 K, R = 2.2 K/min; (c) Sample III, T g = 1248 K, R = 2.2 K/min. The asterisk in (c) may represent an impurity phase identified as Ba 2 Cu 3 O 6 …”

“…So far, various oriented epitaxial YBCO films have been reported on the NGO substrates with crystallographic orientation origin clarified, − shedding novel light on such a regime. More recently, based on those theories, effective novel approaches have been developed to tune supersaturation in the solution for the controllable growth of oriented films. − Moreover, it is achievable to grow the a- and c -axis oriented phase ( a -, c -phase) on an identical NGO substrate. Through fine manipulating supersaturation, desirable artificial microstructures, such as a/c grain boundary structures and a -grains composited with c -films have been successfully fabricated, − which expand the application field of REBCO films and facilitate the exploration of underlying physics.…”

New Magneto‐Optical Film of Ce,Ga:GIG with High Performance

“…For preparing a magneto‐optical film with high quality, the deposit method and the substrate are all important. At present, several film growth techniques such as pulsed laser deposition technology, liquid phase epitaxy (LPE) method, sol–gel method, metal‐organic chemical vapor deposition (MOCVD) method, and the radio‐frequency (RF) magnetron sputtering technique have been applied. Among these methods, frequently used pulsed laser deposition technology cannot be applied for mass production because the thin film deposition area is small, the equipment is relatively expensive, and the high‐energy laser is unsafe for the user.…”