Schematic diagrams of some of the molecular layers fabricated. We also studied Ag and Pd metallizations without Au capping. A complete list is found in Table I.
Corresponding STM and BEEM images of diodes obtained for a tunneling current of , tip bias of , scan areas (a) no molecular layer, BEEM current scale (b) C8DT and (c) C16MT, BEEM scale of . For the C8DT molecular layer, the BEEM signal is very weak and almost submerged in the background noise.
Averaged BEEM spectra obtained with a constant tip current of for diodes as a function of molecular layer as indicated. Plot (a) is a larger scale showing the threshold region of plot (b). The thresholds are listed in Table I.
Auger spectra of exposed to air.
Results from current-voltage and BEEM measurements as a function of diode structure. Listed are the sample evaporation run number, metal layer thicknesses, GaAs -type doping where doped epitaxial layer on substrate, is a bulk wafer, and is a bulk wafer, ideality factor , barrier height , STM tunneling observed, BEEM threshold voltage, BEEM/TIP current ratio measured at a tip bias of .
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