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(a) Schematic of corona charge surface voltage measurement process: First a layer of charged molecules from a corona ion source is deposited (left). To measure the resulting surface voltage, a Kelvin probe is scanned across the surface, monitoring its potential (right). (b) The energy band diagram of an oxidized -type semiconductor sample showing the corona ions deposited on the sample surface (⊕) and the charge sheet (−) created just below the oxide layer. denotes the Fermi energy level and and the energy at the bottom of the conduction band and the top of the valence band, respectively.
Cross section analysis of a contact potential map of the corona charged oxide on wafer B after the center part of has been scanned ten times in KPFM mode. The markers on the map (a) indicate the origin of the cross section data plotted in (b). The data reveal a change in the surface potential of about after repeated scanning in the -wide center area relative to the surrounding area. This is due to a partial discharge of the corona ions in the center area during the surface topography scan (not shown) when the AFM tip is in semi-contact with the surface.
Contact potential difference as measured by the KPFM vs measured in the same spot by the macroscopic SKP on wafers A and B, respectively. Also shown are the correlation coefficient and the standard deviation of the data from the linear fit. The axis intersects were determined to (A) and (B). They are likely related to the work function difference between the Pt and highly oriented pyrolytic graphite (HOPG) calibration surfaces used to calibrate the SKP and KPFM measurements.
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