Growth conditions of CuAlO2 films — Thermodynamic considerations

CuAlO2 (CAO) is a metastable phase. However, it can be obtained at room temperature in air under certain conditions. p(O2), T, and heating and cooling rate upon annealing of as-deposited CAO in pulsed laser deposition and other deposition methods act simultaneously on its formation (and disintegration upon cooling) and survival of crystallites contacting each other. Conversion of CAO into crystallized CuAl2O4 and CuO below the phase boundary at 1003 °C (at 0.21 atm O2) is a very slow process helping to maintain the compound under ambient conditions. Conductivity is a function of the annealing parameters. With thick films on sapphire substrates, annealing can lead to an interconnected network of crystallites which assures electrical conductivity.