Silicon surface transformations: From initial phases of pore formation to nanoscopic metal–insulator–semiconductor junctions

The functioning and fabrication of nanoemitter solar energy converting structures is described. Metal nanoisland formation on a nanoporous anodic oxide template is investigated in model systems where Pt is deposited onto H-terminated single crystal Si electrodes. The formation of an oxide layer, concurrent with the noble metal electrodeposition (Pt, Ir) is revealed by synchrotron radiation photoelectron spectroscopy (SRPES) and TEM. Scanning tunnelling spectroscopy (STS) on the metal islands and at the adjacent oxide covered surface shows rectifying behaviour at the nanoscopic silicon-oxide-metal contact. In the divalent dissolution regime in fluoride containing solution, initial pores form at re-entrant sites on the surface. Interestingly, the adsorption of enzymes such as the reverse transcriptase (RT) of the avian myeloblastosis virus (AMV) also occurs preferably at similar sites on a step-bunched Si surface. The results are discussed based on highly local nanoscopic electrical fields in the semiconductor and in the adjacent electrolytic double layer.