Removing graphite flakes for preparing mechanically exfoliated graphene sample

A study is presented into how to remove impurities generated in the graphene sample preparation process using mechanical exfoliation. Almost all of the impurities on an exfoliated graphene sample are graphite flakes or thick stacks of graphene. Large flakes of graphite are problematic sources in the measurement of graphene device properties, as they might cause an electrical short between electrodes on the graphene device. The heating was adapted followed by ultrasonic cleaning to remove graphite flakes among various cleaning methods. The major goal of the presented method is to remove graphite flakes, whereas single-layer graphenes should remain on the substrate not to be damaged. Using a statistical approach of cleaned particles, the efficiency of the cleaning method was analysed. As a result, the heating and sonication method was efficient to remove large and thick flakes on substrates. From Raman spectroscopy the sample was confirmed to be intact.