Mechanical and Electrical Properties of ZnO-Nanowire/Si-Substrate Junctions Studied by Scanning Probe Microscopy

Scanning tunneling spectroscopy was used to check the tunneling IiV characteristics of junctions formed by n-ZnO nanowires deposited on Si substrates with n- and p-type electrical conductivity (i.e. n-ZnO nanowire/ n-Si and n-ZnO nanowire/p-Si junctions, respectively). Simultaneously, several phenomena which in∞uence the measured IiV spectra were studied by atomic force microscopy. These in∞uencing factors are: the deposition density of the nanowires, the possibility of surface modiflcation by tip movement (difierence in attraction forces between nanowires and the p-Si and n-Si) and the aging of the surface. ZnO nanowires (ZnO NWs) are expected to play an important role as functional units in future nanoscale devices. Di‐culty in reproducible p-type doping of ZnO (nominally undoped ZnO is of n-type) demands a method of electrical conductivity type veriflcation which is cost efiective and easy to perform. Scanning probe microscopy (SPM) has high spatial resolution and can probe local electronic properties of the material. Several interesting applications of SPM techniques on ZnO NWs were reported (conducting-atomic force microscopy (AFM) [1{3], NW bending [4], patterning growth locations [5]). In this work scanning tunneling spectroscopy (STS) is used for the identiflcation of pin junction behavior of ZnO NWs on Si substrate. For n-ZnO NWs deposited on Si substrate, we expect | depending on the Si electrical conductivity type | the presence (for p-Si substrate) or the absence (for n-Si) of the tunneling IiV curves of diode slope indicating