摘要
ZnO纳米材料的光致发光光谱一般由近紫外光谱和可见光谱组成，其发光特性与其结晶质量有着密切的联系。通常情况下，激光脉冲沉积方法制备的ZnO薄膜由于其结晶质量高而具有较强的紫外发射，而ZnO纳米棒由于其缺陷较多却表现出较强的可见光发射。ZnO纳米棒制备工艺流程简单、反应温度较低、无污染，作为白光LED的基础材料可广泛应用于照明及显示领域。为得到较强的可见发光，本文分别利用水热法和PLD方法制备了ZnO纳米棒和ZnO薄膜，研究了各种生长条件及后处理对ZnO纳米材料可见光发射的影响。
⑴本文用PLD方法联合水热法，首先研究了不同衬底对生长ZnO纳米棒的影响。结果表明，在有ZnO薄膜缓冲层的玻璃衬底制备的ZnO纳米棒的结晶较好，室温PL光谱显示其在可见光区的发光比ZnO薄膜的发光强。在此基础上，继续研究不同条件对ZnO纳米棒结构和发光的影响，以期获得在可见光区发光更强的ZnO纳米棒。
通过制备不同反应时间、不同反应浓度及不同反应温度的ZnO纳米棒，探究了ZnO纳米棒的生长机理，并研究了ZnO薄膜缓冲层在ZnO纳米棒生长过程中所起的作用。①在生长时间2-5h范围内，随着反应时间的增加，ZnO纳米棒的XRD衍射峰的相对强度值依次增大，半高宽依次减小，说明ZnO纳米棒的结晶质量变好；ZnO从分布不均间隔较大逐渐生长为排列致密均匀有序的纳米棒；室温光致发光光谱显示ZnO纳米棒的近带边发射依次降低而深能级发光依次升高。②溶液浓度在0.03mol/L-0.06mol/L范围内，随着浓度的增加，ZnO纳米棒的直径依次增大，ZnO纳米棒的间隔依次减小，均匀性依次变好；ZnO纳米棒的近带边发射先增大后减小，深能级发光呈现增大的趋势，二者发光强度的比值依次降低，说明相对的ZnO纳米棒在可见区的发光随溶液浓度的增大而增强。③反应温度在95℃-125℃范围内，随着温度的增加，ZnO纳米棒的直径逐渐增大，纳米棒的间隔逐渐减小，纳米棒的取向性逐渐变好；ZnO纳米棒的近带边发射先降低后升高，深能级发光逐渐增强。④ZnO薄膜缓冲层起到种子层及缓冲层的作用，既促使ZnO快速成核并生长，又抑制ZnO纳米棒沿其它相生长。
⑵应用PLD方法在400℃的衬底温度下，制备了不同氧环境的ZnO薄膜，研究了退火对ZnO薄膜结晶和发光的影响。①在制备过程中未充氧，经过500℃-900℃的退火，ZnO的衍射峰的半高宽依次减小，但在900℃突然变大；PL光谱显示，经过退火，ZnO薄膜在可见光区出现发光峰，在800℃退火时发光强度最大。②在制备过程中充氧，发光光谱中显示在绿光区出现了发光峰；经过500℃-900℃的退火，ZnO衍射峰的半高宽依次减小，在900℃时突变；在800℃退火时可见区的发光强度值最大。
Photoluminescence spectrum of ZnO nanomaterials include near UV spectrum andvisible spectrum generally. The luminescence properties have closely contact with thecrystalline quality of ZnO nanomaterials. ZnO prepared by PLD emits ultraviolet lightstronger than visible light generally. As so many defects, ZnO nanorods have a strong visibleemission. The preparation process of ZnO nanorods is simple, and it has low reactiontemperature, pollution-free, and so on. As the base material of white LED it can be widelyused in lighting and display field. For the purpose of obtained ZnO nanorods which havestrong visible emission. In this paper, ZnO nanorods are prepared by hydrothermal methodand ZnO thin films are by PLD, respectively. Effects of several of growing conditions andpost-processing on structure and photoluminescence properties of ZnO nanomaterials haveinvestigated.
⑴Effects of different substrates on growth ZnO nanorods which prepared by PLDcombine with hydrothermal method are studied. The crystallization of ZnO nanorods whichprepared on the glass substrate with ZnO film buffer layer is the better than others. It can beseen from room temperature photoluminescence spectra that visible light emission of ZnOnanorods stronger than ZnO film. On the basis of the fact, the influence of different growthconditions for ZnO nanorods structure and luminous are studied. ZnO nanorods which visiblelight emition much stronger are expected.
Through the preparation of ZnO nanorods with different reaction time, different solutionconcentration and different reaction temperature the growth mechanism of ZnO nanorods arestudied and the role of ZnO film buffer layer in the growth process of ZnO nanorods isexplored.①In the2-5hour range during the growth, as the reaction time increases, relativeintensity values of the diffraction peak of ZnO nanorods are increased, the FWHM aredecreased. It shows that the crystalline quality of ZnO nanorods is getting better. ZnOnanorods have uniform distribution, compacted arrangement from the state of unevendistribution and big gap. Room temperature PL spectra display the near band edge emission ofZnO nanorods is reduced while the deep level luminescence is increased.②In the reactionsolution concentration range of0.03mol/L-0.06mol/L, as the solution concentration increases,the diameter of ZnO nanorods are increase, the gap are decrease, and its uniformity is getting better. The near band edge emission of ZnO nanorods are increases first and then decreases,deep level luminescence shows an increasing to constant trend. The ratio of the light emittingintensity gets lower in turn. It shows that the deep level luminescence of ZnO nanorods isincrease with solution concentration increased.③In the reaction temperature range95℃-125℃, as the reaction temperature increases, the diameter of ZnO nanorods are increasegradually, the gap are decrease, the orientation of nanorods become better, the near band edgeemission of the ZnO nanorods first decrease and then increase and deep level luminescenceincrease gradually.④The ZnO film buffer layer plays the role of seed layer and buffer layer,which prompt rapid nucleation and growth of ZnO nanorods, and inhibit ZnO nanorodsgrowing along the other phases.
⑵At400℃substrate temperature, we prepared ZnO thin films with different oxygenenvironment by PLD. Effect of annealing on crystallization and luminescence of ZnO film arestudied.①Oxygen ionized did not appear in the preparation process. After annealing at500℃-900℃, FWHM of ZnO are reduced, but at900℃it increased suddenly, PL spectrashows that ZnO thin films appear luminescence peak in visible region after annealing, whilethe annealing temperature of800℃the luminescence intensity reached maximum.②Oxygenionized appear in the preparation process. PL spectra displayed luminescence peak appearedin the green light region. After annealing at500℃-900℃, FWHM of ZnO remained reduce, itbegan to increase at900℃; at800℃luminescence intensity value reached maximum invisible light region.
引文
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