Optical profilometry was used to measure the quality of the crystal surface grown at the glass slide interface. Figure shows a contour plot of a 1×1 mm 2 area of the crystal surface. The surface roughness (root mean square height, Sq) of this area is ~3 nm, indicating that the crystal surface is optically smooth and free of major defects. It is presumed that any defects observed on the crystal surface are imparted from the glass surface that the crystal was grown on. The normalized X-ray diffraction patterns of our MAPbBr3 crystal match the simulated diffractogram produced from MAPbBr3 in the Pm3m space group in Figure . No impurity peaks are present in the measured diffractogram and the MAPbBr3 diffraction peaks are indexed to the (100) crystallographic plane and multiples of (100), showing strong preferred orientation of the top crystal surface in the 〈100〉 crystallographic direction. The MAPbBr3 surface XPS spectra depict typical surface chemistry characteristics of a sample exposed to ambient atmosphere with an oxygen concentration of about 10.4 at.% and adventitious carbon at about 66 at.%. Merged high-resolution XPS spectra of the MAPbBr3 sample surface, inset table of peak position, integrated peak area, and atomic percentage are shown in Figure . A survey XPS scan of all measured elements from the surface of the MAPbBr3 sample is provided in Figure . The decomposition of the Pb 4f spectra (Fig. ) is modeled by component peaks with binding energy in the range of a native Pb oxide (4f7/2 ≈ 138.4 and 4f5/2 ≈ 143.3 eV) and Pb 2+ binding energy of (4f7/2 ≈ 137.6 and 4f5/2 ≈ 142.6 eV). The O 1s core-level peak is modeled (residual STD = 0.582) with four synthetic component peaks (Figure ) with lowest energy component peak having a binding energy comporting with that of Pb oxide at ≈ 530.6 eV. EDS was also performed to investigate the chemical composition deeper into the bulk of the crystal (Figure ). The expected 1:3 ratio of Pb:Br was found from EDS (Table ) confirming that only a thin layer of the surface is oxidized while the bulk of the crystal is pure lead halide perovskite.