Development of Image Corrections for Photoemission Electron Microscopy (PEEM) and its Application to Graphene

The PEEM is a full-field electron microscope that utilizes the photoelectric effect to image a surface. Due to its resolution on the order of 10 nanometers and its ability to image both the morphology of a surface and its band structure it is a useful tool in understanding the properties of materials for use in electronic devices. To correct for random sample misalignment and experimental frame of reference in the spectroscopy mode of the PEEM, the 3D dataset must be rotated in both the momentum and energy axis which requires pixel calibration and energy alignment. I have created custom Python scripts to both automate this process and standardize the calibration and correction procedure to streamline data analysis for users of the PEEM. Graphene was utilized as an initial calibration material due to its distinct electronic band structure. The 6 Dirac cones of graphene were used as iso-energy points to align the frames on the energy axis and a series of matrix operations were utilized to rotate the image in the momentum axis to correct for sample misalignment. I used the corrected dataset to estimate the Fermi velocity and compare to other graphene samples measured in the PEEM. We are also looking to extend our experiments by investigating nitrogen dilute doped GaAs.