Atomic graphoepitaxy: A growth model for c-axis in-plane-aligned, a-axis oriented YBa2Cu3Ox thin films

Abstract
The simple growth model of pure a‐axis‐oriented YBa2Cu3Ox thin films on (100)‐oriented SrLaGaO4 substrates of a K2NiF4‐type structure is proposed. This is called ‘‘atomic graphoepitaxy.’’ The model is based on an atomic‐scale geometry of the (100) surface of K2NiF4‐type substrates, which is characterized by atomic‐scale grooves made of oxygen octahedra running along the 〈010〉 direction. These grooves are assumed to act as preferential nucleation sites of c‐axis in‐plane‐aligned, a‐axis‐oriented YBa2Cu3Ox. Based on this hypothesis, the pure a‐axis‐oriented thin films are successfully obtained on (100)‐oriented Nd2CuO4 substrates of K2NiF4‐type structure.