Characterization of the Topography and Thickness of Gallium Thin Films by Scanning Tunneling Microscopy

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Result date: 01/01/2016
Author: R. T. Bratfalean,
Institute: Department of Molecular and Biomolecular Physics, National Institute of Research and Development for Isotopic and Molecular Technologies, Romania
Publication: Instrum Sci. Technol.,
Instrument: MBE Systems
Scanning tunneling microscopy (STM) was employed to characterize the topography of 32 and 4 µm thick gallium films; thicknesses that have not yet been addressed. The STM images revealed submicron grains on both surfaces although a reduced grain density was observed on the thinner film. The granular structure may be explained by a thin gallium oxide layer that acted as an elastic membrane against liquid gallium underneath that expanded during freezing of the sample. We also believe that the same gallium oxide layer is also responsible for an intriguing effect that appears as soon as the tungsten tip lands on the gallium film: the onset of continuous regular z-oscillations of the tip even at rest. This is an effect that we believe has not been previously reported in the literature. We have also demonstrated, for the first time, a new thickness determination method for the gallium film based on an STM image obtained during the solid-to-liquid phase transition.
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