Measurements of the in-plane coefficient of thermal expansion of freestanding single-crystal natural graphite

Abstract

The in-plane coefficient of thermal expansion (CTE) of freestanding single-crystal natural graphite was directly determined using the thermal bulge method. The Scotch tape method was used to obtain 40-nm-thick graphite flakes by the micromechanical cleavage of high-quality graphite flakes. The naturally bulged shape of the samples enabled us to easily measure the CTE without any need for transfer or additional processes. The measured CTE was negative and gradually decreased in magnitude from 1.8×10−6/°C to 0.7×10−6/°C when the samples were heated from 25°C to 225°C.