Ultrathin ZnO Nanowires On Cu Substrate: Growth And Optical Property

ZnO is a very important wide band-gap semiconductor, the direct energy band gap of ZnO is about 3.37 eV. ZnO has a large exciton binding energy(60 me V) at room temperature, thus it is able to provide large potential applications, especially in room-temperature ultraviolet photoelectronic devices Compared with nanostructures of large size, ultrathin nanostrctures has been one main theme in nanosciences and nanotechnologies for their large surface-to-volume ratio. Recently, synthesis of ultrathin material, including Ag, Au, ZnS, Si, CdSe and Fe3O4 has been intensively pursued, and the significant breakthroughs have recently been reviewed. In the area of nanomaterials, one-dimensional nanoscale semiconductors is expected to create wide-ranging application possibilities from electronics, photonics, sensors, photocatalysts, energy generation(such as solar cells), to field-emission devices. ZnO is one of the most intensively pursued nanomaterials. In general, ZnO nanowires as one-dimensional materials with diameters of less than 10 nm are expected to display novel and unique physical and chemical properties due to quantum confinement. So the preparation of the research in ultrafine ZnO nanowires and its corresponding physical and chemical properties are attracting the interest of many subject group. Photoluminescence spectra is a very effective way to detect the internal structure of materials. It does not directly contact with the material and does not damage materials. Thorough research in view of the relatively hot materials in the current field of nanometer materials is carried on in this paper, including the preparation of ultra small size of ZnO nanostructures and their photoluminescence(PL) properties.In this paper, we successfully synthesized ultrathin ZnO nanowires on copper foil(30 μm) substrate using Chemical Vapor Deposition method(CVD) and measured the PL properties of the synthesized nanowires. The morphology of the as-synthesized ZnO nanowires are characterized using scanning electron microscopy(SEM) and transmission electron microscopy(TEM). The diameter of the as-synthesized ZnO nanowires is 5 nm~8 nm. We develop a new approach to synthesize ultrathin nanostrctures without using any catalyst(CVD).325 nm He-Cd laser is used to explore PL properties of the ultrathin ZnO nanowires. At room temperature, the free exciton peak of ultrafine ZnO nanowires blue shift for 40 meV than ZnO powder, and the intensity of peak representing defects is very high, this is due to the small size effect of nanowires and the defect caused by their small size. By comparison of PL properties, at 15 K between the as-synthesized ZnO nanowires and the ZnO nanowires with diameter of 4.1 nm in reference, we confirm that small size effect of nanowires will lead to the peak of free exciton(FX) a blue shift and the smaller the diameter of the nanowires, the more obvious the peak of FX shift. For special verification of the nature of the peak located at 3.322 eV(labeled as “FX-LO”), the paper shows the changes of the photoluminescence spectra of sample as temperatures rise. The evolution of the luminescence spectra with increasing temperature is shown in this paper. France J-Y company production HR800 micro zone Raman system is used in this paper to measure the Raman spectrum of the sample. Small size of ZnO can also lead to frequency shift and asymmetric broadening of a peak in Raman spectrum. Due to the ultrafine one-dimensional nanostructures is prepared on Cu substrate, it is easier for people to study and apply the ultrafine one-dimensional nanostructures, compared with other semiconductors or dielectric substrate. The as-synthesized ZnO nanowires on Cu substrate will has great application value in electronics and optics.