TY - JOUR TI - Photoemission studies of biased graphene-insulator-semiconductor structures DO - https://doi.org/doi:10.7282/T3VT1W99 PY - 2018 AB - Electrostatic potential changes across ultrathin film heterostructures are critical for the functioning of a large class of devices. In this research work, a general approach to the direct measurement of nanoscale internal fields has been developed. Small spot X-ray photoemission is performed on a biased graphene (Gr)/dielectric/Si structure in order to experimentally determine the potential profile across the system, including discontinuities at the interfaces. The energy of the core-levels of the different elements from the stack provide a measure of the local potential and are used to reconstruct the potential profile as a function of depth in the first 10nm of 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 can be determined, in addition to the potential drop across each layer. This unique experimental approach offers understanding of device function and leads to new possibilities for addressing problems that have until now prevented further scaling of devices and 2D material integration. Silicon oxide (SiO2), a well understood dielectric, is used as a proof of concept material in this structure to determine the potential profile using a refined biased-XPS method. A simple linear potential profile across the oxide along with offsets at each interface is able to describe the experimental data. The offset at the SiO2-Si interface results from band bending developed in the Si substrate under the different biasing conditions. Whereas, the Gr-SiO2 interface potential offset, in the studied bias range, is proposed to arise from trapped polar species at the interface. Finally a more complex Gr/HfO2/SiO2/Si heterostructure has also been studied under bias. Here, potential offsets at the Gr/HfO2 and SiO2/Si were measured as in the simple Gr/SiO2/Si case, but with an additional variable offset at the HfO2-SiO2 interface. Possible origins for this potential offset that varied in intensity and direction with applied bias are proposed. KW - Chemistry and Chemical Biology KW - Graphene LA - eng ER -