Structural and Electrical Properties of Calcium Manganese Oxide Thin Films

Calcium manganese oxide (CaMnO₃ abbreviated as CMO) is a metal oxide thin film belonging to the ABO₃ perovskite family of materials, where A is an alkaline earth metal, B is a transition metal, and O is oxygen. Electrical resistivity, a property of interest for applications of CMO in renewable energy technologies, can be controlled by introducing vacancies at the oxygen site of the crystal lattice, which are produced when the material is oxygen deficient. We will present recent results from our research on controlling oxygen deficiency in epitaxial thin films of CMO which are grown using pulsed laser deposition (PLD). Previous research has shown that for CMO films grown on (100) oriented LaAlO₃ (LAO) substrates, tensile strain present help stabilize oxygen deficiency. The resistivity of these films is strongly thickness dependent. Thinnest films, which are coherently strained films show resistivity which is orders of magnitude less than that of the fully oxygenated material. In addition to film thickness, film growth parameters such as oxygen pressure and laser fluence (energy density) used for the deposition also control oxygen stoichiometry, and thus the structural and electrical properties of the film. We will present our results on the dependence of structural and electrical properties of CMO films on the laser fluence and oxygen growth pressure.