Fabrication of metal/oxide/fluorographene/oxide/silicon capacitors and their charge trapping properties

Graphene is well-known as a material with extremely high carrier mobility, although its electrical properties can be changed into those of a highly insulating thin film by a fluorination treatment (fluorographene). Taking advantage of this property, a flexible nonvolatile memory using fluorographene as a charge trapping layer has been proposed. However, the mechanism of charge trapping on fluorographene is not yet fully understood. In this paper, we fabricated fluorographene and analyzed it by X-ray photoelectron spectroscopy and Raman spectroscopy. Furthermore, metal-insulator-semiconductor (MIS) capacitors inserted with fluorographene were fabricated and evaluated electrically. As a result, a large flat-band voltage shift was observed even though the fluorine concentration (C-F bonding ratio) was saturated at around 14%. Furthermore, the charge centroid of the MIS capacitor with fluorographene coincides with the location of the fluorographene. These results indicate that fluorographene can capture injected charges and is a candidate for use in nonvolatile memory with two-dimensional materials.