Figure 1: Visualization of the virtual substrate method.
From: Virtual substrate method for nanomaterials characterization
(a) Schematic diagram of the virtual substrate method implemented in surface analysis. A combination of four interrelated spectra measured for two slightly different bare substrates (JS(A), JS(B)) and a target nanomaterial supported on these two substrates (JN(A), JN(B)) is used in the virtual substrate method. Different groups defined as ‘substrate’ and ‘nanomaterial’ (surrounded by black boxes) are classified from the spectra measured for the bare substrate or nanomaterial. A traditional two-point probe measurement is indicated by a red dashed box. (b) Visual representation of the virtual substrate method using a 3D coordinate system, where two spectra obtained using a traditional two-point probe measurement are plotted in pairs orthogonally along the x- and y-axes and share one electron energy axis (z-axis). Two spectra measured for bare substrates (blue and green dots) are plotted in the x-z plane (substrate plane), and the other two spectra measured for the nanomaterial supported on the substrates (blue and green dots) are plotted in the y–z plane (nanomaterial plane). According to the virtual substrate method, the covering nanomaterial information is included in the lines that pass through two points whose x and y coordinates are the intensities of the two spectra in the traditional two-point probe measurements for different substrates at a given energy. The intercept of these lines, RNJ0(E), is plotted in the y–z plane (nanomaterial plane) as red dots. One line (purple) at energies Ei is plotted together in the x–z and y–z planes (thin purple lines) along with the deviations in these shallow lines (thick cyan line). At Ei, two known points (JS(A), JN(A)) and (JS(B), JN(B)) obtained by traditional two-point probe measurements with different substrates and the intercept point (0, RNJ0) are presented as large black dots.
