射频溅射掺铝ZnO薄膜工艺及其光电性能研究

【作者】 李金丽；

【导师】 邓宏；

【作者基本信息】 电子科技大学 ， 材料物理与化学， 2007， 硕士

【摘要】 氧化锌（ZnO）是一种重要的宽禁带（Eg=3.37eV）半导体材料,其激子束缚能高达60meV,而掺Al的ZnO（AZO）薄膜在室温紫外光电器件方面有巨大的应用潜力。国外对AZO薄膜的研究从20世纪80年代就开始,但Al3+的掺杂浓度一般在10at%以下,其紫外敏感性能远远不能满足太阳盲区紫外探测器的要求。针对以上存在的问题,本论文主要从以下几个方面进行了初步的探索:1.采用射频溅射方法,探索了纯ZnO薄膜制备的最佳工艺。在此基础上,制备了不同浓度（2at%,5at%,10at%,15at%,20at%,30at%和40at%）掺Al的ZnO薄膜（AZO）。通过XRD、AFM、SEM和XPS等分析薄膜组织结构、表面形貌和化学成分,研究结果发现:2at%～15at%掺杂量的AZO薄膜均只有一个衍射峰（002）,表明制备出来的AZO薄膜具有纤锌矿结构且呈c轴择优取向;当掺杂浓度大于15at%时,（002）峰消失,15at%左右为掺杂的临界浓度;随着掺杂量增加到30at%,衍射谱中出现了Al3O2相。2.使用荧光分光光度计测试不同掺Al浓度的AZO薄膜室温下光致发光谱,不同掺Al浓度的AZO光致发光图谱中都存在很强的紫外发光峰和深能级缺陷发光峰。在Al离子浓度高达15at%时,出现了两个紫外深能级发光峰:3.53eV,3.96eV;而且随着Al离子浓度增加到30at%,这两个发光峰均向短波长方向移动（3.53eV→3.78eV,3.96eV→4.41eV）。3.紫外-可见分光光度计测试薄膜在紫外-可见光范围内的透过率,结果表明,薄膜在可见光范围内,平均透过率大于85%。随着Al掺杂浓度的增加,薄膜吸收边逐渐向紫外波长方向移动,光学禁带宽度也逐渐加宽。当Al浓度为30at%时,AZO薄膜的光学禁带宽度约为4.6eV。4.研究了掺Al浓度与薄膜电阻率之间的关系。当掺杂浓度为2at%左右时,薄膜电阻率最小,为3.4×10^-4Ω.cm;当掺杂浓度为30at%左右时,薄膜电阻率最大,为1.3×10⁷Ω.cm.更多还原

【Abstract】 Zinc oxide （ZnO） is an important wide band gap （Eg=3.37eV） semiconductor material, its exciton binding energy is 60meV. These characters make it expected to be applied in the ultraviolet optoelectronic devices which can be operated at room temperature. Although, AZO thin films also have been fabricated for conducting transmission application in the previous work, the Al3+ concentration was always below 10 atomic percent （at.%）, which put a strict limitation on the optical band-gap shift to deeper ultraviolet range as using in deeper UV LD and LED purpose. Therefore, further studies on heavy doped AZO thin films and relative phenomena are important! In order to study heavy-doped AZO thin film, we researched three topics in this paper mainly:1. ZnO thin films were prepared by RF sputtering method on the Si substrates in order to get the best process conditions. Then the Al-doped ZnO （AZO） thin films with different Al3+ concentration （2at%,5at%,10at%.15at%,20at%,30at% and 40at%） were prepared on Si and quart substrates. X-ray diffraction （XRD）, scanning electron microscope （SEM）, atomic force microscopy （AFM） and X-ray photoelectron spectroscope （XPS） were used to characterize the crystalline structure, orientation and surface morphology of the AZO thin film. It was revealed that wurtzite structure with （002） orientation AZO thin films were obtained at Al concentration below 15 atomic percent （at%）. As the Al concentration above 15at%, the thin films did not fully crystallize.2. Photoluminescence spectrum was acquired in a SHIMADZU fluorespectrometer at room temperature. The shape of all the spectra was featured by a strong emission near UV and a defect-related deep level emission in visible region. Two new emission peaks occurred at 351nm and 313nm when the Al doping above 15at% from the Photoluminescence spectrum, and the peaks shifted towards the shorter wavelengths with increasing the Al concentration.3. Ultraviolet-visible （UV-vis） spectrometer was used to measure the optical properties of the AZO thin film. It was found that their optical transmittance was over 85% in the visible region with a sharp fundamental absorption edge. Optical band-gap of the films is increased, depending on the Al doped concentration, from 3.34eV for un-doped ZnO film to 4.6eV for 30at% Al doping.4. The electrical properties of the AZO thin films were studied. A minimum resistivity of 3.4×10^-4Ω.cm was obtained at a doping concentration of 2at%; while the maximum 1.3×10⁷Ω.cm at a doping concentration of 30at%.更多还原