Microscopic Kinetics of Heat-Induced Oxidative Etching of Thick MoS2 Crystals

Abstract

We have studied the kinetics of microscopic heat-induced oxidative etching in the case of thick, mechanically exfoliated, geological MoS2 crystals in air. We have measured spatial dimensions of microscopically obtained triangular etch pits during a series of sample heating increments at a given temperature. The data has been collected for the samples heated at 320, 350, 370 and 390 °C. Using our data we have extracted an Arrhenius apparent activation energy, Ea = 1.15 ± 0.25 eV, as well as an Arrhenius kinetic constant, A= 10x s-1 with x = 9,09 ± 2,03. The obtained value of Ea compares extremely well with another study of oxidative etching, but done via in situ Raman spectroscopy on an collection of thin MoS2 flakes. We notice that apparent activation energy relates to a weighted average of microscopic Arrhenius-like processes. It might need a correction due to yet unknown fractions of removed MoOx species at the investigated temperatures. Based on the existing literature the most expected reaction is a s...