In-situ temperature measurements of Joule-heated graphene using near-infrared CCD imaging system

We report temperature distribution of graphene during Joule heating process using in-situ near-infrared (NIR) charge-coupled device (CCD) imaging system. Graphene layers were prepared using mechanical exfoliation of a pyrolytic graphite sheet (PGS), which is commercially available from an industrial materials company, and were then deposited on SiO₂/Si substrates with approximately 780 nm thermally grown oxide. Thickness of the graphene layers was optically determined to be 20-80 nm using Fresnel theory. In order to investigate the heating process of the graphene, the temperature of the graphene under current flow was estimated using NIR microscopy with a CCD detector. A hand-made, in-situ experimental setup consists of an IR microscope, a NIR CCD, and an image enhancer. The CCD detector is mounted on the IR microscope with objective 20×. Heating experiments were carried out in obscurity. Joule heating process controlled with applied bias voltages was performed for the graphene in vacuum/ambient air, and the temperature distribution of the graphene during NIR emission was successfully studied by in-situ NIR CCD imaging system. The temperature of Joule-heated graphene was detected to be approximately 800 K. These results imply that NIR CCD imaging system is a useful tool for the investigation of temperature distribution of graphene.