Characterization of the interface between laser ablated YBCO film and buffered sapphire substrate

Abstract

Pulsed laser deposition was used to deposit both the buffer layer and YBa 2Cu 3O 7−x (YBCO) film on sapphire substrate. The interface between laser ablated YBCO thin film and the r-plane sapphire substrate has been characterized by comparing the results of a transmission electron microscopy (TEM) and an Auger electron spectroscopy (AES) depth profile. Buffer layer of PrBa 2Cu 3O 7−x (PBCO) was used to block the interdiffusion. The interfaces of YBCO on sapphire and YBCO on PBCO buffered sapphire have been compared. The intermediate diffusion layer between the YBCO film and the bare sapphire is observed. But the diffusion layer between the YBCO thin film and the PBCO buffered substrate was barely observed directly by the cross-section image of TEM. The thickness of the diffusion layer in the film on bare sapphire is about 30 nm which is consistent with the result of the AES depth profile. Also PBCO layer thickness was systematically reduced to find the minimum buffer layer thickness to prevent the interdiffusion. AES results show that the diffusion between the YBCO thin film and the substrate is effectively blocked even with 5 nm thick PBCO buffer layer.