Nanoscale Internal Fields in a Biased Graphene-Insulator-Semiconductor Structure

Measuring and understanding electric fields in multilayered materials at the nanoscale remains a challenging problem impeding the development of novel devices. At this scale, it is far from obvious that materials can be accurately described by their intrinsic bulk properties, and considerations of the interfaces between layered materials become unavoidable for a complete description of the system's electronic properties. Here, a general approach to the direct measurement of nanoscale internal fields is proposed. Small spot X-ray photoemission was performed on a biased graphene/SiO₂/Si structure in order to experimentally determine the potential profile across the system, including discontinuities at the interfaces. Core levels provide a measure of the local potential and are used to reconstruct the potential profile as a function of the depth through the stack. It is found that each interface plays a critical role in establishing the potential across the dielectric, and the origin of the potential discontinuities at each interface is discussed.