【作者】 马全宝；

【导师】 叶志镇；

【作者基本信息】 浙江大学 ， 材料物理与化学， 2007， 博士

【摘要】 透明导电氧化物作为一种重要的光电子信息材料,在制造发光器件、薄膜太阳能电池、表面声波器件、传感器、平板液晶显示器和红外反射器等领域得到了广泛的应用。在这类材料中,氧化锌（ZnO）是一种宽禁带（3.3eV）的n型半导体材料,易产生缺陷和进行杂质掺杂,相对于铟锡氧化物（ITO）和SnO2而言,具有原材料资源丰富、价格低廉,沉积温度相对较低和在氢等离子体环境中稳定性好等优点,是一种最有希望替代ITO的材料。至今人们已经采用多种薄膜生长技术来制备ZnO基透明导电薄膜,相对于其它薄膜生长技术而言,直流反应磁控溅射因沉积系统相对简单、易操作,可实现大面积镀膜,更有利于实现今后的工业化生产。此外,掺杂ZnO透明导电薄膜在红外区具有优良的红外反射特性,在红外反射窗膜和热反射器等领域具有广阔的应用前景。因此,开展透明的高导电近红外反射掺杂ZnO薄膜的研究具有非常重要的意义。本文通过直流反应磁控溅射技术在玻璃衬底上制备出了透明的高导电近红外反射Ga掺ZnO（ZnO:Ga）薄膜,系统研究了Ga含量、衬底温度、溅射压强、氧分压、溅射功率和退火温度等工艺参数对薄膜性能的影响,并对红外反射机理做了详细的探讨。此外,我们也采用直流反应磁控溅射技术制备了Ga掺ZnMgO（ZnMgO:Ga）薄膜并研究了Mg含量对薄膜结构、电学和光学等特性的影响。通过研究得出以下主要结果:1.首次采用直流反应磁控溅射技术,以Zn-Ga合金为靶材,在玻璃衬底上制备出了高透明高导电近红外反射ZnO:Ga薄膜。所制备的ZnO:Ga薄膜为具有（002）面单一择优取向的六角多晶纤锌矿结构且c轴垂直于衬底,薄膜沿c轴的晶粒尺寸在17-32nm之间。2.衬底温度、沉积压强和溅射功率等因素对薄膜的表面形貌有很大的影响。衬底温度为300℃,溅射压强为1.0Pa,溅射功率为140w时沉积的ZnO:Ga薄膜表面相对平滑,晶粒堆垛致密均匀并且没有明显的晶粒间界。3.所有薄膜均为简并的n型半导体,在靶材Ga含量为2～4 at%、衬底温度为300℃、溅射压强为1.0～1.5Pa、氧分压为0.2～0.3Pa和溅射功率为140～160W时沉积的薄膜具有最低的电阻率～3.0×10^-4Ω·cm,载流子浓度可达2.5×10²¹cm^-3。薄膜中Zn、O和Ga的纵向分布很均匀,且Ga仅以单一化学结合态形式存在。4.研究了ZnO:Ga薄膜的红外反射特性。所制备的薄膜在可见光区的透过率均超过90%,在红外区均具有较低的透射率和较高的反射率,并且薄膜的红外反射率随着载流子浓度的升高而增大,红外透射截止边随着载流子浓度的升高而向短波方向移动。在靶材Ga含量为2～4at%、衬底温度为300℃、溅射压强为1.0～1.5Pa、氧分压为0.2～0.3Pa,溅射功率为140～160W时沉积的薄膜透射率在1500nm时低于10%,反射率在2500nm时可达72%,薄膜具有最大的光学禁带宽度～3.76eV,所沉积的薄膜具有优良的光学性能。5.研究了退火温度对ZnO:Ga薄膜性能的影响。薄膜随退火温度的升高,晶粒尺寸开始逐渐增大,薄膜经400℃退火后可获得最低电阻率为2.6×10^-4Ω·cm的导电薄膜。随着退火温度的进一步升高,薄膜的电阻率开始增大,在退火温度为550℃时薄膜的电阻率升高到4.39×10^-4Ω·cm。尽管经较高温度退火后薄膜的电导率有了较大的提高,但是经过退火处理后的薄膜红外反射特性降低。6.首次采用直流反应磁控溅射技术,在玻璃衬底上制备了ZnMgo:Ga薄膜,研究了Mg含量对ZnMgO:Ga薄膜的结构、电学和光学等特性的影响。所沉积的ZnMgO:Ga薄膜仅存在对应于（002）和（004）面的两个衍射峰;Zn、Mg、O、Ga元素在薄膜中分布均匀:所沉积薄膜的电阻率随着Mg含量的增加而增大,同时伴随有电子载流子浓度和迁移率的降低。更多还原

【Abstract】 Transparent conductive oxides are an important optoelectronic material for a variety of applications in the fabrication of various devices such as electro-optical devices,thin-film solar cell,surface acoustic wave devices,sensors,flat panel liquid crystal display devices,infrared（IR）reflector,etc.Among the different materials belonging to this category,zinc oxide（ZnO）is a n-type semiconductor material with a bandgap of 3.3 eV and a promising alternative to indium tin oxide（ITO）in TCO applications,due to its ease in doping,abundance in nature,low cost,and relatively low deposition temperature and stability in hydrogen plasma compared to ITO and SnO₂.By now many film growth techniques have been used to deposit transparent conductive doped-ZnO films.Among the different techniques used for the growth of ZnO films,DC reactive magnetron sputtering method is promising in preparing transparent conductive doped-ZnO thin films due to the simplicity of the growth process required and ease in operation.Compared to other film growth techniques, large-area films can be grown by this method,which will help to industrialized production and application in the future.Moreover,doped ZnO transparent conductive films with good IR reflective behavior will significantly contribute to the applications of near-IR reflecting mirrors and heat reflectors.Therefore,this work on highly transparent conductive and IR reflective doped-ZnO films is of great interests and potentials.In this paper highly transparent conductive and near-IR reflective ZnO:Ga thin films were grown on glass substrate by using DC reactive magnetron sputtering technique.The influence of Ga content,substrate temperature,deposition pressure, oxygen partial pressure,sputtering power,annealing temperature,etc on the film properties has been studied systemically.And the mechanisms of IR reflection are discussed detailedly.Besides,ZnMgO:Ga films with different Mg content have been prepared by DC reactive magnetron sputtering,and effects of Mg content on structural, electrical and optical properties of the films were also investigated in detail.The main results are obtained as follows:1.Highly transparent conductive and near-IR reflective ZnO:Ga thin films have been firstly prepared on glass substrate by DC reactive magnetron sputtering.All the ZnO:Ga films with the preferential orientation of（002）plane are polycrystalline and possess hexagonal wurtzite structure with their crystallographic c-axis perpendicular to the substrate.The grain size along the c-axis is found between 17 nm and 32 nm.2.Substrate temperature,deposition pressure and sputtering power have great influences on the film surface morphology.The surface of the films deposited at 300℃,1.0 Pa and 140 W is smooth and the grains are uniformly stacked up and entirely compact,so no grain boundaries are visibly found.3.All the films are degenerate doped n-type semiconductor.A lowest resistivity of 3.0×10^-4Ω·cm was obtained under the deposition conditions of the target with 2～4 at%Ga content,substrate temperature 300℃,deposition pressure1.0～1.5 Pa,oxygen partial pressure 0.2～0.3 Pa,sputtering power 140～160 W,and the electron carrier concentration reaches the value of 2.5×10²¹cm^-3.The contents of Zn,O as well as Ga uniformly distribute in the whole film,and only one chemical state of Ga is present in the ZnO:Ga films.4.The IR reflective behavior of ZnO:Ga films has been studied.The average optical transmittance in the visible range exceeds 90%for all the films.All the films have low transmittance and high reflectance in the near-IR region.The IR reflectance of the films shows an increase with increasing the electron concentration.The IR transmission cut-off wavelength of the films shifts toward the lower wavelength with the electron concentration increasing.The transmittance of the films deposited under the deposition conditions of the target with 2～3 at%Ga content,substrate temperature 300℃,deposition pressure1.0～1.5 Pa,oxygen partial pressure 0.2～0.3 Pa,sputtering power 140～160 W is below 10%when the wavelength is higher than 1500 nm and the reflectance reaches 72%at the wavelength of 2500 nm.And they have the largest band gap～3.76 eV and the best optical properties.5.The influence of post-annealing temperature on the properties of ZnO:Ga thin films has aslo been studied.The average crystallite dimension of the ZnO:Ga films becomes larger and larger with the increase of annealing temperature.A lowest resistivity of 2.6×10^-4Ω·cm was obtained at the annealing temperature of 400℃.As the annealing temperature further increases,the resistivity increases and reaches 4.39×10^-4Ω·cm at the annealing temperature of 550℃.However,Annealing is not useful to improve near-IR reflective behavior of ZnO:Ga films although the conductivity of the films can be increased after annealed at the higher temperature.6.The ZnMgO:Ga films were synthesized on glass substrate by DC reactive magnetron sputtering for the first time.A systematic study of structural,electrical,and optical properties of ZnMgO:Ga films deposited with different Mg content from 0 to 10 at%have been investigated.Only the peaks indexed to hexagonal（002）and（004） ZnO were observed.The distribution of Zn,Mg,O,and Ga is uniform in the whole film.The resistivity of these films obviously increases with the Mg concentration increasing,accompanied with a reduction in carrier concentration and Hall mobility.更多还原