JOURNAL OF LASER APPLICATIONS
VOLUME 27, NUMBER 4
NOVEMBER 2015
Novel laser-assisted technique for rapid preparing ZnO:X nanoparticles Majid Ebrahimizadeh Abrishamia) Department of Physics, Ferdowsi University of Mashhad, Mashhad 9177948974, Iran
Mahboobeh Soleimani Varaki Physics Department, Shahid Beheshti University, Evin 19839 G.C, Tehran, Iran
(Received 13 July 2015; accepted for publication 17 August 2015; published 28 August 2015) Undoped, Ga and Al-doped ZnO nanoparticles (NPs) were prepared under a one-step procedure of continuous-wave infrared laser irradiation in gelatin media for the first time. Nanoparticles were characterized by x-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, and transmission electron microscopy (TEM). It was found that the sudden increase of the local temperature exceeding the evaporation temperature of the compound groups and solvents might enhance the nucleation and form the smaller nanoparticles. XRD and TEM results showed that all the nanopowders exhibited a single-phase wurtzite structure, the average particle size was about 25 nm and the morphology of nanoparticles depended on their size according to quantum size effect. FTIR spectra revealed that the doping agents affected the absorbance peak positions and the intensities corresponding to Zn-O bonds strength. In addition, the oxygen deficiencies of the samples obtained by laser irradiation have been enhanced, since the preparation process was performed only in seconds. The results showed that this laser-assisted technique could be used for mass production of C 2015 Laser Institute of America. NPs with narrow size distribution. V [http://dx.doi.org/10.2351/1.4929737] Key words: laser processing, ZnO, nanomaterials, precursors, organic: XRD analysis
I. INTRODUCTION
ZnO is an n-type semiconductor with a relatively large direct band gap of 3.3 eV at room temperature. The electron mobility of ZnO with the maximum value of 2000 cm2/(Vs) at 80 K strongly varies with temperature. The specific resistivity of ZnO is about 10ÿ1–10ÿ3 X cmÿ1 and highly dependent on its impurity level. ZnO based compositions have been used extensively in fabricating electronic and optoelectronic devices, due to their applicable electrical and optical properties.1–3 In addition, using different dopants, such as Al, Ga, Mn, and Cr, have been widely used to efficiently control the properties of ZnO bulk and thin film. In the previous works, manganese was used to induce room temperature ferromagnetism to ZnO thin film and improve electrical behavior of ZnO ceramics for varistor applications.4,5 Aluminum and gallium are the common dopants for enhancing ZnO electrical properties, decrease of the resistivity in particular. Muiva et al.6 showed that the electrical resistivity of 2 mol% Al-doped ZnO exhibited a minimum value of 2.8 10ÿ2 X cm. In addition, the conductivity greater than 2000 S/cm was obtained by doping ZnO films with gallium as reported by Gorrie et al.7 In recent years, growth of nanostructures has been attractive due to their atomlike behavior that makes their physical properties counterpoint to the bulk. In this case, several methods have been suggested to prepare undoped and doped ZnO nanopowders after the conventional calcining for a)
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several hours at high temperatures.8–10 Small size of particles and narrow size distribution of the final product enables us to control the morphology, and consequently, the properties of nanoparticles (NPs). This goal can be achieved by using suitable polymer agent in the wet chemistry techniques. Another parameter that plays the main effect in enlarging the particles is the heat treatments during the preparation process, temperature and time duration of calcining in particular. A slightly lower calcining temperature and shorter calcining time duration are expected to prevent the agglomerations, and consequently, lead to formation of smaller particles. The conventional calcining that lasts several hours gives rise to an exothermic reaction that begins at a temperature of the order of about 400 C. In this study, a new laser processing technique was developed to rapid prepare ZnONPs. Several techniques based on using laser light have been suggested for preparing thin films, coatings, and nanoparticles.11 In case of the laser ablation in solution, nanoparticles are produced during the condensation of a plasma plume formed by the laser ablation of a bulk metal plate dipped in a liquid solution. Laser ablation synthesis in solution is a commonly used method for obtaining colloidal solution of nanoparticles in a variety of solvents.12 Another approach is infrared laser irradiation of gaseous mixtures of volatile compounds.13 In addition, laser calcining was used for the synthesis of some superconducting compounds prepared by conventional mixed-oxide method.14 In this work, a simple one-step procedure of continuouswave (CW) infrared laser irradiation in gelatin media has been proposed for the first time to prepare Ga and Al-doped
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C 2015 Laser Institute of America V
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