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▼ [21a-E319-1] Evaluation of the thickness of mechanically exfoliated mica nanosheets affixed on Si substrates by scanning Auger electron spectroscopy.
Keywords:Thickness, Mica, atomic force microscopy and Auger electron spectroscopy
The field of two-dimensional (2D) materials with atomic or molecular thickness represents a broad spectrum of materials with exceptional physical and electronic properties. A fascinating 2D material of mica, one of the groups of sheet silicate (phyllosilicate) minerals, is an oxide with a band gap of 7eV, and has a nearly perfect basal cleavage plane of (001). Mica as 2D material has prominent characteristic applications in the electronic and electrical industries because of its optical transparency, uniform high dielectric constant and mechanical strength as well as its high resistance to heat, water, and chemical agents. The unique properties of mica nanosheets in the applications to electronic industries strongly depend on the thickness and interaction with the underlying substrate. With regard to the development of devices using 2D mica nanosheets, a conventional and reliable method to evaluate their thickness is of great importance when it comes to several atomic layers. In this work, we establish the basis to precisely evaluate the thickness of the few-layer mica nanosheets by Auger electron spectroscopy (AES) in regard to the change of peak-to-peak intensities of Auger electrons. The Auger spectra showed distinct characteristic shapes and intensities according to the change of the number of layers of mica nanosheets. It has been shown that AES analysis can be used as a standard to determine their thickness in the range of 1 to 5 layers of mica nanosheets, which has well coincided with the thickness measured by atomic force microscopy. The AES has a high chemical sensitivity as a surface analytical technique, based on the kinetic energy spectrum of electrons backscattered from the sample irradiated with an accelerated electron beam. We derived the values of inelastic mean free path (IMPF) in mica nanosheets as a function of electron energy of Auger electrons.