Lithium manganese oxide films fabricated by electron beam directed vapor deposition

Abstract

Lithium manganese oxide thin films have been grown using a gas jet based, electron beam directed vapor deposition technique. The deposition rate could be controlled by the electron beam power as well as the gas jet density and speed. This enabled films to be grown at deposition rates up to 16nm∕s which is a significantly higher deposition rate than that reported for the growth of this material by sputtering and other vapor deposition techniques. The lithium manganese oxide films grown by this approach were slightly manganese deficient with a composition Li1+xMn2−yO4, where 0.08<x<0.125 and y∼0.2. After annealing in air at 700°C, thin films grown with a low jet speed had a cubic spinel structure and were composed of very small size grains. The small grain size resulted from the vapor phase formation of clusters and resulted in a nanocrystalline random film texture. These films were highly porous with a spongelike interconnected pore network. The use of a higher jet speed and lower growth pressure resulted in less vapor phase clustering. The films contained small, uniformly distributed pores and exhibited a significant ⟨111⟩ texture. These annealed films appeared well suited for use as the cathode layers in thin film Li∕Li-ion batteries.