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1253-K05-29

Synthesis and Sensing Properties of N-doped ZnO Nanorod Arrays on Quartz Boqian Yang1,2, Xiaoyan Peng1, Hongxin Zhang1, Peterxian Feng1*, Marc Achermann2* 1 Physics Department, University of Puerto Rico, San Juan, PR 00931, U.S.A 2 Physics Department, University of Massachusetts, Amherst, MA 01003, U.S.A * Electronic mail: [email protected]; [email protected].

ABSTRACT Using different pressures of nitrogen, N-doped ZnO nanorod arrays of various densities have been synthesized on quartz substrates by pulsed laser deposition techniques. The nanorods grow preferentially perpendicular to the quartz surface. X-ray diffraction patterns revealed some degradation of the crystal structure at elevated nitrogen pressures. High concentrations of nitrogen doping in ZnO nanorods were estimated by X-ray photoelectron spectroscopy. Raman scattering spectra confirmed the wurtzite structure of N-doped ZnO nanorods. A prototype sensor based on the N-doped ZnO nanorod arrays demonstrates a linear dependence of the conductivity with operating temperature and pressure of a test gas pollutant.

INTRODUCTION One-dimensional (1D) ZnO nanostructures have attracted significant attention due to their potential applications in light-emitters [1], field-effect transistors [2], and gas sensors [3]. Numerous reports demonstrated the fabrication of nanostructures with various shapes (nanowires, nanobelts, nanorings, nanotubes, nanodonuts, nanopropellers, etc.) grown by different techniques such as catalyst assisted thermal evaporation [4], non-catalytic thermal evaporation [5], wet chemical route [6] and solvothermal/hydrothermal route [7], etc. Different types of doping in ZnO also attracted considerable interests [8], due to potentials in sensing applications [9]. Dopants in ZnO can change the conductivity of ZnO [10, 11], which will affect the sensing behavior of prototype sensors based on the variation of electrical conductance [12]. In this paper, we report the preparation and structural characterization of nitrogen doped ZnO (ZnO/N) nanorod arrays on insulating quartz substrates by pulsed laser deposition (PLD) techniques under different pressures of nitrogen. Using these ZnO arrays we fabricated prototype sensors by sputtering Au electrodes with a shadow mask to form contacts to the nanorod arrays. These sensors turn out to be sentitive to changes in temperature and pressure of a gas pollutant. EXPERIMENT DETAIL ZnO/N nanorod arrays of various densities were grown on quartz substrates by PLD techniques under nitrogen pressures of 200 and 400 mTorr. The experimental condition is the same as in our previous work [13], except for the different pressure value of nitrogen fed into the chamber. During the ~ 30 minute deposition time the substrate temperature was maintained at 350 ºC . The morphology of ZnO/N nanorod arrays was characterized using SEM (Scanning

Electron Microscopy) and the phase structures were tested by XRD (X-ray diffraction) with Cu Kα radiation. The chemical bonds and nitrogen concentrations of ZnO/N