Synthesis And Character Of ZnO Nanorod/Nanotube Arrays By Wet Chemistry Method

Owing to extreme mechanical strength, high emiting efficiency, low lasing emission threshhold, excellent chemical and thermal stability one-dimensional semiconductors nanostructures show great application potential in fabricating nanoelectrical and optoelectronic devices. As an important II-VI semiconductor, zinc oxide (ZnO) is of considerable interest due to its distinguished performance in electronics, optics, mechanics, and photonics. ZnO with a band gap of 3.37 eV and large exciton binding energy of 60 meV at room temperature is a key technological material. Recent research has demonstrated that the creation of ZnO nanostructures in highly oriented and ordered arrays is of crucial importance for the development of novel devices (e.g. short wave lase and Grartzel solar cells electrode). Especially, since the first report of ultraviolet lasing from ZnO nanowires (nanorods) at room temperature, substratial effort has been devoted to the development of novel synthetic methodologies for highly oriented and ordered ZnO nannowires (nanorods) arrays.Solution approaches are appealing because of their simple equipment, low cost and good potential for scale-up. Here, ZnO nanorods and nanotubes arrays with different seed films were synthesized by a simple solution method. The morphologies, phase structure, microscope structures and the photoluminescence properties of the prepared products were investigated by field emission scanning electron microscopy (FE-SEM), X-ray diffractometer (XRD), transmission electron microscope (TEM) and photoluminescence (PL) spectrum.The main contents of our work are as follows:1. Synthesis of oriented ZnO nanorod arrays using ZnO sol films as seeds.The well aligned ZnO nanorod arrays were synthesized on a Si subatrate that coated with ZnO sol seeds film in an aqueous solution of zinc nitrate hydrate (Zn(NO3)2·6H2O) and hexamethylenetetramine (HMT; (CH2)6N4). The results indicated that the nanorod were about 100 nm in diameter and more than 1μm in length, which possessed wurtzite structure with a c axis growth direction. The room-temperature photoluminescence measurement of the nanorod arrays with two typical emission peaks at ~380 nm and~ 580 nm were observed, which were assigned to UV emission and green-yellow emission, respectively, the UV emission with a peak at~ 380 nm has been attributed to the near band edge emission of ZnO, while the green-yellow emission originating from the recombination of the holes with the electrons occupying the singly ionized oxygen vacancy.2. Synthesis of oriented ZnO nanotube arrays by using ZnO seeds via thermally decomposing zinc acetateWell-aligned ZnO nanotube arrays were synthesized via a simple aqueous solution route with hexamethylenetetramine and zinc nitrate hexahydrate as inorganic precursors at ambient pressure and low temperature on the ZnO seed films. ZnO crystalline seed films were firstly coated on silicon substrates for epitaxial growth of nanotube via thermally decomposing zinc acetate. The results indicated that the nanotube were about 200 nm in diameter and more than 1μm in length, which possessed wurtzite structure with a c axis growth direction. The room-temperature photoluminescence measurement of the nanotube arrays showed strong ultraviolet emission ~380nm as well as a broad yellow-green emission ~580 nm.3. Synthesis of oriented ZnO nanorod arrays on Si substrate that coated with different seed films1) The oriented ZnO nanorod arrays have been synthesized on a silicon wafer that coated with TiO2 films by aqueous chemical method. The nanorod were about 250 nm in diameter and about 1μm in length. The room-temperature photoluminescence measurement of the nanorod arrays showed strong yellow-green emission as well as a low ultraviolet emission.2) The non-aligned ZnO nanorod arrays were synthesized on a Si subatrate with nano Ag film in an aqueous solution of zinc nitrate hydrate ((Zn(NO3)2·6H2O) and hexamethylenetetramine (HMT; (CH2)6N4). The results indicated that the surface of ZnO with a lot of smaller nanoparticles were very rough, and the orientation of the nanorod array was less aligned.3) The oriented ZnO nanorod arrays have been synthesized on a silicon wafer that coated with TiO2 films by sonochemistry method. The nanorod of with smooth surfaces were about 50 nm in diameter and about 300nm in length.