. . "Other matrices of interest include oxides of the metal and metalloids, such as, but not limited to, Pt???PtO, Si???SiO, Au???AuO, TiO2 and Cu???CuO. Also compound semiconductors, such as lithium niobate, gallium arsenide and indium-phosphide, and nickel-coated mica surfaces, as used in preparation of molecules for observation in an atomic force microscope [see, e.g., III et al. (1993) Biophys J. 6" . .