Contrast enhancement for quantitative image analysis of graphene oxide using optical microscopy for Si-based field effect transistors

Experimental considerations have been performed to obtain the high contrast optical microscopic images of graphene oxide sheets which are useful to probe their quality and morphological information such as a shape, a size, and a thickness. When graphene oxide is used as a semiconducting material in a silicon-based field effect transistor, it is necessary to identify the morphology of graphene oxide on the gate substrate. In this study, we investigated the contrast enhancement of optical microscope images of graphene oxide sheets after hydrazine vapor reduction on a silicon substrate coated with a 300 nm-thick silicon dioxide dielectric layer, which is a conventional gate material in field effect transistors. Also, a green-filtered light source gave higher contrast images comparing to optical images under standard white light. Furthermore, it was found that an image channel separation technique can be an alternative to simply identify the morphological information of graphene oxide, where red, green, and blue color values are separated at each pixels of the optical image. The approaches developed in this study can be helpful to set up a simple and easy protocol for the morphological identification of graphene oxide using a conventional optical microscope instead of a scanning electron microscopy or an atomic force microscopy, especially for silicon-based field effect transistors.