Study On The Preparation And Optoeletronic Properties Of Doped And Intrinsic ZnO

As a luminescent material, ZnO has some advantages with the development of blue, blue-green light, UV light source as so on.Compared with GaN,the most successful wide-band semiconductor material at present, ZnO has many promising advantages. High-quality ZnO with very low defect densities can be synthesized at relatively low temperature. It possesses lower liminal power for photoluminescence and stimulated emission and take on higher efficiency of energy conversion. ZnO has large excitonic binding energy(60mev at RT),which promises strong UV stimulated emission from bound excitonic emissions at room temperature. Photoelectron devices with excellent quality, such as detectors, and light emitting diodes(LEDs),can be made using ZnO .In previous studies,no matter what kinds of preparation methods, preparation conditions, or selection of drugs are seemingly prefect. But people can never exhaust every condition and technology to prepare ZnO. Therefore,in our research works, for some seemingly repeated experimental conditions of preparations were adjusted or changed so as to occur some ZnO materials with special character.The concrete contents and results are as follows:â‘´Zinc oxide nanoparticles were prepared by using hydrothermal synthesis method.The effect of synthesis conditions on the properties of nanometer was studied. ZnO nonoparticles were obtained when using Zn(NO₃)₂, NaOH and H2O as properties and hydrothermalmedia. The X-ray diffraction(XRD), the electronic resistivity and the photoluminescence spectrum are applied to investigate the optical and electric properties of ZnO. The result indicated that the samples are zincite in structure and show sharp diffraction peak of ZnO at (101); The electronic resistivity decrease with increasing the time and temperature of synthesis. When time of the synthesis was 25h and temperature was 200℃,ZnO was purest and higher emission at 376nm ,500nm-600nm , the particle figure was rods ,and the even diameter of the nanometer-sized rods ZnO was about 30-40 nm and its length was about 300-400 nm analyzed by TEM. The reasons of the above-mentioned phenomena are deeply discussed. ⑵High-quality rod-like ZnO were prepared by the two-step method on the Si glass. The intrinsic samples are characterized by X-ray diffraction (XRD) and Spectrofluorophotometer. They characterized the samples'crystalline structure and optical properties.Intrinsic surface morphology of ZnO thin films were characterized by Atomic Force Microscope(AFM) and Scanning Electron Microscopy(SEM). The results showed:the intrinsic ZnO are hexagonal wurtzite structure. The films are straight and uniformly elongated along the C axis. The diameter of rod-like nano ZnO are 400-600nm. The length is 3.78μm. This article analysize the mechanism of results from lattice structure and defect levels.⑶Using zinc nitrate solution as the electrolyte to prepare pure nano-ZnO thin films by electronic deposition on the ITO conductive glass substrates. We have researched the reaction mechanism of ZnO thin films grown by electronic deposition. By testing samples with XRD, we knew the preferred growth face of pure ZnO thin films was along (002). Using the atomic force microscopy (AFM) and scanning electron microscopy (SEM) to observe the surface morphology of the samples, the result showed that ZnO thin film prepared by this experiment were nanoscale level, had smooth surfaces, small undulating and particles uniform. The last test was made by the sample photoluminescence (PL spectra) ,we found that, Sample launch in ultraviolet only.â‘·Zn_0.8Na_0.1Co_0.1O thin films were prepared by pulsed laser deposition on SiO2 substrates at different substrate temperatures (400℃,500℃,600℃) . Zn_1-x-yNa_xCo_yO thin films were prepared by pulsed laser deposition (PLD) on Si(111) substrates.The X-ray diffraction(XRD), atomic force microscopy(AFM), the Fluorescence spectrometer and the Four-probe tester were applied to investigate the structure, surface, optical and electric properties of ZnO respectively. Effect of substrate Temperature on the structure, Optical and Electric properties of Zn0.8Na0.1Co0.1O thin films was discussed. The result indicated that the films are zincite structure, and it has a strong ultraviolet(UV) emission and doping leads to the UV emission peak red-shift. The films exhibited low resistivity. When the substrate temperature is 600℃. Zn_1-x-yNa_xCo_yO has the best crystalline quality and UV emission is the strongest. When the substrate temperature is 400℃,the lowest resistivity,7.55×10^-1Ω·cm ,has been obtained. the films are zincite in structur and doping leads to the UV emission peak red-shift. When the doping concentration of Na,Co are 5% and 10% respectively, the film has a highest intensity with the most obvious red-shift(397 nm). When the doping concentration are 10% and 10% of Na and Go,the lowest resistivity, 8.34×10^-1Ω·cm ,in films. The reasons of the phenomena above-mentioned are deeply discussed.⑸ZnO nano-particles and films were prepared by sol-gel process on Si substrates.The ratio of In/(Zn+In) were 0%,5%,8%,10%respectively. Crystal phase structure and photoelectric properties of these film were characterized and these chromaticity coordinates of different samples were also calculated in CIE-XYZ color system. The results showed that: preferred growth direction of ZnO films changed from (002) plane to (001) plane and interplanar distance became shorter. When doping amount of In was 5%, Zn atoms was replaced by In atoms absolutely. Resistivity of the film decreased firstly and increased afterwards with the increase of the amoute of In. Ultraviolet emission peak of spectral appeared the phenomenon of redshift; A new peak emerged at 670nm with the increase of In. The sample of 5%(film),10%( nano-particles) emitted white-light.The mechanism of emitting white-light was discussed from the view of additional energy levels.⑹The Glass/ZnO ITO/NR/PMMA/PPV type device was design and preparation that is one-dimensional, organic/inorganic nanometer ZnO light-emitting device.The device's performance was test through the i-v curve testing, electroluminescent test. In room temperature positive bias dc voltage, driven by nearly all got ZnO ultraviolet radiation with edge glow. Also detected typical MEH - PPV excitons glow. In low voltage condition, the 600 nm MEH - PPV excitons shine is stronger, and nearly uv ZnO with luminous weaker side radiation. In high voltage condition, with nearly ZnO luminous intensity of ultraviolet radiation rapidly increasing edge of more than 600 nm, obvious excitons glow.