Variation of thermal expansion coefficient of freestanding multilayer pristine graphene with temperature and number of layers

Abstract

The in-plane coefficient of thermal expansion (CTE) of freestanding multilayer pristine graphene was directly measured by the thermal bulge method using a white light interferometric microscope. Graphene ribbons with 3, 5, and 10 layers were prepared by exfoliation of high-quality graphite flakes and then transferred over 60-120 ism wide trenches in a Si substrate. A novel transfer procedure was developed to achieve the freestanding configuration. All the measured CTE values were negative in the temperature range of 25-150 degrees C, and their absolute values decreased with increasing temperature and number of layers. The CTE of monolayer graphene can be approximated to about -7 x 10(-6)/degrees C. It was speculated that a structure with more than 12 layers was graphite rather than graphene.