The pH Dependency of Group IB p-type doped ZnO Nanorods by Chemical Bath Deposition

Reference	Presenter	Authors (Institution)	Abstract
06-063	Maziar Montazerian	Rakhsha, A.H.(University of Tehran); Abdizadeh, H.(University of Tehran); Pourshaban, E.(University of Utah); Golobostanfard, M.(University of Tehran); Mastelaro, V.R.(Universidade de São Paulo); Montazerian, M.(Federal University of São Carlos (UFSCar));	A systematic investigation of the zinc oxide (ZnO) nanorod arrays (NRAs) growth in an aqueous media including various pHs can dramatically assist the incorporation of copper (Cu) and silver (Ag) into ZnO lattice for synthesizing p-type ZnO NRAs. Since the pH-solubility diagrams verify the pH role as a determining parameter in the solubility of Cu+ and Ag+ ions, optimization of pH value is vitally important to achieve a successful doping. For this purpose, the samples were prepared using a chemical bath deposition method in which seeded substrates were placed vertically in media with various pH containing zinc and dopant precursors (all were nitrate salts) and the system were stirred for 3 h in 90 °C. Herein, nitric acid and ammonium solution were used to change pH of the system. Field emission scanning electron microscopy revealed that the growth of NRAs strongly depends on the pH. No sign of NRAs was observed in acidic environments (pH<7) due to the lack of OH- which is crucial for the growth of ZnO NRAs. Furthermore, in pH values between 7.5 and 9.5, the rapid precipitation of ZnO in the bulk solution prevented the heterogeneous growth of the ZnO NRAs on the substrates. However, synthesizing in the pH value of 7 and 11 for 3 h resulted in 1.2 and 5 µm in length (70 and 160 nm in diameter) ZnO NRAs, respectively. These pHs were also appropriate for the doping processes of Cu (in pH value of 7) and Ag (in pH value of 11) since the solubility of their ions are higher than other pHs and this makes it suitable to incorporate them in ZnO lattice. Moreover, a slight shift of (002) peak in X-ray diffraction pattern together with the detecting of Ag and Cu peaks in X-ray photoelectron spectroscopy patterns in the doped samples compared to undoped one, are under investigation to determine efficient incorporation of dopant elements.
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