Epitaxial growth on MgO on (001) surfaces of silver single-crystal film substrates

The epitaxial growth of evaporated MgO films (<25–4000 Å) on smooth (001) surfaces of silver single-crystal film substrates at a temperature inthe range 25°–200°C has been studied by reflection high energy electron diffraction. At substrate temperatures below 150°C, MgO is oriented with its (111) plane parallel to the surface of the substrate. The (111) orientation is fibrous. At 150°C a major fraction of the deposit is oriented in parallel and at 200°C only the parallel orientation is observed. The deposit initially grows as oriented three-dimensional nuclei. As the film thickness increases to 500 Å, randomly oriented MgO is simultaneously formed at the surface. With further increase in thickness the degree of epitaxial orientation decreases and at 1000 Å a small amount of one- degree (111) orientation appears at the surface. At 4000 Å the surface orientation becomes one-degree (111); the (111) orientation is interpreted as a final growth orientation.