Anisotropic chemical expansion due to oxygen vacancies in perovskite films

In scientifically intriguing and technologically important multifunctional ABO3 perovskite oxides, oxygen vacancies are most common defects. They cause lattice expansion and can alter the key functional properties. Here, it is demonstrated that contrary to weak isotropic expansion in bulk samples, oxygen vacancies produce strong anisotropic strain in epitaxial thin films. This anisotropic chemical strain is explained by preferential orientation of elastic dipoles of the vacancies. Elastic interaction of the dipoles with substrate-imposed misfit strain is suggested to define the dipolar orientation. Such elastic behavior of oxygen vacancies is anticipated to be general for perovskite films and have critical impacts on the film synthesis and response functions.

COPPER OXIDE THIN FILM SYNTHESIS, CHARACTERIZATION AND APPLICATION AS CATHODE IN PHOTOELECTROCATALYTIC CELL FOR METHYL ORANGE DEGRADATION

A copper oxide thin film was synthesized through a copper sheet annealing process that was carried out using a gas stove, furnace and 1000 W tungsten . The product and its response were measured using a and then characterized by XRD, SEM and EDX. Furthermore, the copper oxide was applied as a photocathode in a cell with Platinum (Pt) as the anode for methyl orange degradation, and the thin film annealed at 60 sec produced the highest current density. According to XRD and EDX results, copper oxide structure was dominated by Cu2O, while SEM showed the presence of a Cu2O porous surface. Methyl orange solution degradation also showed the best result for the copper oxide annealed at 60 sec and in all pH variations, while the best degradation was obtained at pH 1.

Editorial for the Special Issue on ‘Metal Oxide Thin Film: Synthesis, Characterization, and Application’

The last two decades have witnessed the development of new technologies for thin-film deposition and coating [...]

Thin-film synthesis of superconductor-on-insulator A15 vanadium silicide

We present a new method for thin-film synthesis of the superconducting A15 phase of vanadium silicide with critical temperature higher than 13 K. Interdiffusion between a metallic vanadium film and the underlying silicon device layer in a silicon-on-insulator substrate, at temperatures between 650 and 750 °C, favors formation of the vanadium-rich A15 phase by limiting the supply of available silicon for the reaction. Energy dispersive X-ray spectroscopy, X-ray photoelectron spectroscopy, and X-ray diffraction verify the stoichiometry and structure of the synthesized thin films. We measure superconducting critical currents of more than 106 amperes per square centimeter at low temperature in micron-scale bars fabricated from the material, and an upper critical magnetic field of 20 T, from which we deduce a superconducting coherence length of 4 nm, consistent with previously reported bulk values. The relatively high critical temperature of A15 vanadium silicide is an appealing property for use in silicon-compatible quantum devices and circuits.