Effects of substrate temperature, deposition pressure, and thickness on the morphology of ultrathin platinum film on SiO 2/Si substrate

Abstract

The dependence on thickness of the resistance of platinum film deposited by electron-beam evaporation at room temperature onto a thermally grown SiO 2 substrate, shows that the platinum film is in a discontinuous island form when the thickness is less than 1.3 nm. At about 2 nm the film is very continuous electrically but porous. For platinum film deposited at 250 °C, it appears that the morphology is an island form when the thickness is less than 0.5 nm, and in a continuous porous form at about 1.8 nm. As the platinum deposition temperature increases, the film morphology, including the island dimensions or grain size and the gaps between islands or pores, becomes more uniform but has larger grains. Also, it appears that when both the background pressure and deposition temperature are varied, the increase in deposition temperature has a dominant effect in increasing the grain's base area, but that the grain's average height Z rms increases at lower pressure (10 −8 Torr) and tends to decrease at higher pressure (10 −6 Torr). The morphology of an ultrathin metal film on an insulator substrate can also be determined by measuring the electrical properties of the film. For example, measuring the film's impedance at different temperatures, frequencies, or applied bias can reveal that the film is either in discontinuous island form or in continuous form.