ZnO nanorods prepared through chemical vapor deposition technique are characterized by microscopic and X-ray photoelectron spectroscopy (XPS) techniques to correlate the effects of size on the binding energy of Zn 2p3/2 photoelectrons. A positive shift in Zn 2p3/2-binding energy as compared to that in bulk ZnO is assumed to be the effect of size of ZnO tips. The shift in binding energy has been explained in terms of relaxation energy in the photoemission process. Simultaneously, Auger parameter of the nanorods is evaluated for stoichiometric composition. The extra peak in O1s spectrum of nanorods is explained as adsorbed O-bearing species or surface contaminants. 1. Introduction One-dimensional (1-D) nanostructures of semiconducting materials have received much attention in recent years, with the expectation that they can be applied to short-wavelength optical devices and excitonic devices operating at room temperature. In particular, the exciton-binding energies in GaN and ZnO are reported so large that they can be applied to laser devices based on excitonic processes. In fact, exciton-related stimulated emission and optically pumped laser action in GaN and ZnO nanostructures have been observed at room temperature [1, 2]. Its high band gap energy of 3.37？eV at room temperature [3] and free-exciton binding energy (60？meV) [2] which is much larger than that of GaN (~25？meV) [1] along with its larger absorption coefficient compared to GaN make ZnO a potential candidate for optoelectronics applications. A detailed photoluminescence (PL) study at low temperature with assignments of excitonic peaks and associated longitudinal optical (LO) phonon replicas along with donor-pair-acceptor transitions has been reported for ZnO single crystalline sample [4]. Looking at the importance in the understanding of electronic properties for the ultimate optoelectronic applications, a study on the effect of size dispersion on electronic properties will be extremely important. We report here the photoelectron spectroscopic studies of stoichiometric ZnO nanorods (NRs), grown by catalyst-free chemical vapor deposition (CVD) technique, with sharp facets. Role of size in these nanostructure on the binding energy of photoelectrons is studied in the light of final state effects of the photoemission process. 2. Experimental Details ZnO NRs were grown on p++-Si (~0.001？Ohm-cm) substrate in the flow of N2/O2 (500？sccm) at 130–140°C by CVD technique using metalorganic precursor of zinc bisacetylacetonate hydrate [Zn(AA)2·xH2O; Zn(C5H7O2)2·xH2O] [5]. The morphology of the NRs was
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