【作者】 蒋平；

【导师】 吴雪梅； 诸葛兰剑；

【作者基本信息】 苏州大学 ， 凝聚态物理， 2009， 硕士

【摘要】 ZnO薄膜是一种直接宽带隙半导体材料,具有较高的激子束缚能（60eV）,即使在室温条件下激子也不会分解,具有多种用途,因此近年来对ZnO基半导体材料的研究越来越为人们所重视,为了研究沉积气压对磁控溅射制备Zno薄膜的结构与性能的影响,本文采用CS-400射频磁控溅射法在不同的沉积气压（0.5Pa-5Pa）下分别在Si（111）及石英基底上成功的制备了ZnO薄膜和25%N₂气氛下Zn_0.975Cu_0.025O薄膜,采用X射线衍射（XRD）、扫描电镜（SEM）、紫外-可见分光光度计等分析测试手段,研究了样品的表面形貌、晶体结构、光学学性能等。重点研究了不同的沉积气压对ZnO薄膜结构和光学性质的影响。结果如下:一.采用CS-400型射频磁控溅射仪在Si（111）和石英基底上成功的制备了ZnO薄膜,对不同沉积气压下的ZnO膜进行了结构和光学性质的研究。XRD和SEM测试结果显示了在合适的沉积气压（>2.0Pa）下,制备出结晶良好,具有良好c轴择优取向的ZnO膜,随着沉积气压的上升,晶粒尺寸先变大再变小,结晶质量先变好再变差,同时通过计算发现薄膜的晶格常数c也随之增大,薄膜的（002）峰位向小角方向偏移。在ZnO薄膜的透射谱研究中,发现在可见光区域的平均透过率超过80%,陡峭的吸收边在380nm左右,所对应的光学带隙约为3.23eV—3.27eV,随着沉积气压的上升变化很小。我们认为所有的光学性质都来源于物质电子的电磁辐射作用,所以不同沉积气压下ZnO薄膜的PL谱大致类似。然而通过纯Ar气氛下制备的ZnO薄膜和25%N₂气氛下ZnO薄膜的对比,由于25%N₂气氛下ZnO薄膜的结构和光学性质和纯Ar气氛下制备的ZnO薄膜的结构和光学性质并无很大区别,我们认为当采用N₂作为掺杂源时,N₂并没有被激发成为活性氮,难以形成稳定的有效浓度的N掺杂ZnO。二.对25%N₂气氛不同沉积气压条件下制备的Zn_0.975Cu_0.025O和ZnO薄膜进行了结构对比。不同沉积气压下Zn_0.975Cu_0.025O薄膜样品具有良好c轴择优取向,Cu的掺杂提高了薄膜的C轴的择优取向;Zn_0.975Cu_0.025O薄膜的XRD衍射的（002）衍射峰在沉积气压为4.0Pa时最强,半高宽最窄和晶粒尺寸最大,ZnO薄膜在2.0Pa时衍射峰最强,半高宽最窄和晶粒尺寸最大;Zn_0.975Cu_0.025O薄膜的c轴晶格常数比ZnO薄膜样品的c轴晶格常数大,使得垂直于C轴的压应力偏大;随着沉积气压的升高Zn_0.975Cu_0.025O薄膜片状颗粒逐渐减少而较小的球状颗粒逐渐增多;样品中Cu元素的掺入,薄膜沉积的则优取向更明显,颗粒尺寸减小以及球状颗粒的增多,薄膜的致密性增强,薄膜的厚度受到影响。实验中采用N₂作为掺杂源时,没有检测到N—Cu键的存在,所以难以形成稳定的有效浓度的N掺杂ZnO。更多还原

【Abstract】 ZnO films, a directly wide band gap semiconductor, has gained substantial interest because of its large exiton binding energy （60meV）, which could lead to lasing action based exiton recombination even above room temperature. It have been actively studied because of its potential applications. 1D nanostruture material of ZnO such as aligned nanowires, nanobelts, nanorings and nanohelixes are discovered one after another in recent years. Owing to their unique photic, electrical, and magnetic properties, they have greatly attracted material scientists attentions. 1D ZnO nanostruturesbased devices like nanogenerators, field effect transistors, sensors, solar cells are p redicted to be effective solutions to the problems of energy, environment, biology, electronics, photoelectricity, spaces and so on. Specially, the studies for ZnO semiconductors have now attracted much attention of many researchers. To research the effects of different deposition pressure on the structure and optical properties of ZnO films, in this paper, we prepared ZnO films with different deposition pressure（0.5Pa-5.0Pa） by radio frequency （RF） magnetron sputtering. Surface morphology, crystal structure, optical and magnetic properties of ZnO based films were investigated by XRD, SEM, ultraviolet-visible spectrum photometer et al.and studied the characteristics and optical properties.The results are the following:1. ZnO films were prepared by the radio frequency magnetron sputtering technique（RF）on Si（111） and quartz glass substrates. The effect of different deposition pressure on the structural and optical properties of ZnO films and ZnO films under 25%N₂ were discussed in details. X-ray diffraction （XRD） pattern and SEM indicates that the films are single phase and had wurtzite structure with c-axis orientation under an acceptable deposition pressure（>2.0Pa）. The SEM shows that the grain size of ZnO films increases with the increasing of deposition pressure and then decreases. The crystallation of samples were promoted with the increasing of deposition pressure and then become difference, With increasing of deposition pressure, lattice constant of ZnO films which calculated also increases and （002） diffraction peak position of ZnO films becomes smaller.In the study of transmittance spectra of the ZnO films, We find the transmittance spectra of the ZnO films are higher than 80% in the visible light range. The absorption edges are determined to be around 380nm, the corresponding optical band gaps increasing with the deposition pressure increasing, are about 3.23ev-3.27ev. There is no much differents between Transparency spectra and PL spectra of ZnO thin films with different deposition pressure because we think all optical properties are come from the effects of electromagnetic radiation in electrons. After compared with ZnO thin films and ZnO thin films under 25%N₂ ,There is no much difference in the structural and optical properties between them. So we think when we used N₂ as a doped source, N3+ didn’t doped into ZnO because it didn’t actived, so it’s very hard to form N doped ZnO thin films with effective concentration.2. The effect of different deposition pressure on the structural properties of Zn_0.975Cu_0.025O films under 25%N₂ were compared with ZnO thin films under 25%N₂ in details. Zn_0.975Cu_0.025O films under different deposition pressure grows with the c-axis（002） diffraction peak orientation. Cu doped enhanced the preferred orientation of c-axis of Zn_0.975Cu_0.025O films under 25%N₂. After compared with Zn_0.975Cu_0.025O thin films and ZnO thin films under 25%N₂., Zn_0.975Cu_0.025O films with 4.0Pa deposition pressure have the biggest diffraction peak, the biggest grain size and the smallest FWMH. But ZnO thin films under 25%N₂ with 2.0Pa deposition pressure have the biggest diffraction peak, the biggest grain size and the smallest FWMH. C-axis lattice constant of Zn_0.975Cu_0.025O films is bigger than ZnO thin films, so compress stress in Zn_0.975Cu_0.025O films perpendicular to the c-axis is bigger. With the increase of deposition pressure, sheet particles in Zn_0.975Cu_0.025O films under N₂ are decrease and spherical particles are increased at the same time. With Cu doped, The preferred orientation of c-axis of Zn_0.975Cu_0.025O films is more obvious,grain size decreased and spherical particles are increased. The density of films is increased and the thickness of Zn_0.975Cu_0.025O films are also influenced. When we used N₂ as doped sourced, there is N-Cu pairs in Zn_0.975Cu_0.025O films, so it’s hard to form N doped ZnO thin films with effective concentration.更多还原