Authors: M. Asghar, A. Ali, M.-A. Hasan, M. Yasin Akhtar Raja
Affilation: Islamia University of Bahawalpur, Pakistan
Pages: 137 - 140
Keywords: MBE, ZnO nanorods, FTIR, SEM, XRD, Raman scattering
ZnO nanorods stand out as one of the most important candidates for next generation opto- and nano electronics. Synthesis of high quality and stable ZnO nanorods remains a challenge thus far. Similarly fabrication of thermally stable and rectifying metal/nanorod-ZnO and Ohmic contacts also pose uphill task. Various growth methods (metal organic vapor deposition, MOCVD, hydrothermal method and sputtering) are being attempted to grow quality ZnO nanorods but each of the method leaves defects in the form of vacancies and/or interstitial in the layer, however, molecular beam epitaxy (MBE) because of its kinematic mode promises a quality growth of the material. Accordingly this paper presents a useful study on the synthesis and characterization of ZnO nanorods using (MBE). ZnO layers of thickness ≤500nm were grown on p-type silicon wafer Si(100) under conditions: substrate temperature 300oC, temperature of the Zn-Knudsen cell ~286oC ± 05, pressure of the chamber ~4x10-4 ± 0.5x10-4 mbar and oxygen plasma was generated by RF power supply operated at 300W. The as-grown ZnO layer was characterized by means of Fourier transform infrared (FTIR), scanning electron microscopy (SEM), Raman scattering and x-ray diffraction (XRD). FTIR displays a clear Zn-O bond at 411cm-1 excitation, large area SEM image demonstrates well defined nonorods of length ~ 100 μm while energy dispersive spectrum (EDAX) reveals Zn-O at% as 55:45 that means the stiochiometric ratio is less than 1. Raman scattering exhibits nonpolar modes of Zn and O (sub-lattices) at 109 and 436 cm-1 respectively which clearly justifies the presence of nanocrystals/nanoparticles and in addition it also yields A1(LO) mode (polar) associated with ZnO. XRD pattern shows that the preferable direction of the growth of ZnO is along (0002) direction however additional peaks (week) are also present. From the existing literature, useful discussion has been carried out to justify the obtained results and henceforth interesting conclusion has been drawn for device quality material.