Growth of Large Crystalline Grain Al Thin Films on Amorphous Substrates

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Abstract
(111) uniquely oriented large crystalline grain Al thin films have been grown on amorphous substrates such as glass or fused quartz. Al has been evaporated by means of an electron beam in a vacuum of 10-7 mbar which was obtained by a conventional oil diffusion pump in conjunction with a titanium sublimation pump and a series of shields cooled at the liquid nitrogen temperature. By studying the variation of the grain size as a function of the growth temperature, a large increase in the grain size has been found at a substrate temperature 100°C below the Al melting point. This has been interpreted as due to the beginning of the metal surface melting and, as a consequence, to the quasi rheotaxial growth of the metal on itself. When the growth has been carried out at a substrate temperature close to the Al melting point (625°C), the grain size has been found out to increase exponentially as a function of the film thickness with a slope which slows down at a thickness of about 1 pm. (111) oriented columnar grains with a size of 50 – 100 pm, hitherto unreported, have been obtained on glass substrates kept at a maximum temperature of 655 °C. The surface morphology of the Al films has been studied by SEM microscopy while the film structural properties have been studied by an X-ray powder-diffracto-meter and by computer - controlled pole figure goniometer.