【作者】 白雪；

【导师】 王星明；

【作者基本信息】 北京有色金属研究总院 ， 有色金属冶金， 2011， 硕士

【摘要】 透明导电薄膜具有高可见光透过率和低电阻率,因此可以作为平面显示器和太阳能平面电极材料,也可用在节能方面,如建筑玻璃表面和汽车玻璃表面。AZO透明导电薄膜的禁带宽度达到3.4ev,本征吸收限为360nm,可减少P,N型掺杂区对光的吸收,提高光能量的利用率,是合适的窗口层材料。同时,AZO在等离子体中稳定性好,制备技术简单,原料便宜易得,无毒,在性能上与ITO可比拟,这些特点使其成为ITO的替代品。随着透明导电薄膜的应用发展,AZO溅射靶材及薄膜沉积技术成为研究热点。影响薄膜性能的主要因素包括靶材的使用性能和薄膜沉积工艺。目前,AZO薄膜的沉积技术较为成熟,但AZO靶材热压过程中孔隙率、气孔演化、显微结构变化及其对薄膜性能的影响研究很少。因此,研究AZO靶材的热压致密化过程,对AZO靶材的产业化发展和薄膜太阳能产业来说都具有重要的意义。首先,本文以ZnO和Al2O3粉体为原料,采用热压烧结制备AZO靶材,升温速率为20℃/min。通过阿基米德法、压汞仪、SEM、XRD、四探针电阻率测试仪分析AZO靶材的性能,研究热压工艺条件对AZO靶材致密化的影响。结果如下：AZO靶材的热压致密化过程随热压温度的上升可以分为两个阶段。850℃-1100℃,随着温度的升高,连通孔洞发生了合并收缩,孔径逐渐集中化分布,闭孔率在1050℃-1100℃具有最低值。特征是致密化速率快,孔洞大部分连通。当温度升至1100℃之后,随着传质的继续,气孔逐渐缩小和变形,直到全部转变成孤立的闭合气孔。特征是闭孔率迅速上升,致密化速率较慢。在保温时间对致密化过程的影响研究中发现：当温度为1150℃时,随着保温时间的延长,由于闭合气孔率的升高和连通孔洞的生长,靶材存在反致密化现象。在压力对致密化过程的影响研究中发现：较大的外加压力在促进烧结致密化的同时导致闭孔率的升高。通过在升温过程中施加压力能促进靶材的烧结致密化,降低靶材的连通孔隙率和闭合孔隙率。根据致密化过程分析结果,高密度靶材的制备工艺为1050℃保温60min,1150℃保温60min,制备所得AZO靶材相对密度大于98%。其次,本文在对原料成分,靶材的成分和结构分析测试中发现：Al2O3含量为2wt%的原料粉体系中,部分Al元素扩散进入了ZnO的晶格中,另一部分由于固溶度的限制而形成了ZnAl2O4尖晶石。在热压过程中由于ZnAl2O4化合物分布在ZnO晶界处,导致Al元素局域含量差异,造成靶材中成分分布不均匀的缺陷。最后,本文将所制备的靶材作为溅射源,进行射频磁控镀膜测试。采用台阶仪,紫外分光光度计,四探针电阻图谱仪,XRD等分析测试仪测试薄膜的性能。结果表明,在相同的溅射条件下,靶材孔隙率越低,沉积速率越快,所得薄膜电阻率越低,但溅射功率较高时薄膜透光率明显减小。平均孔径较小且孔径分布集中的靶材,溅射所得薄膜电阻率较低。在溅射功率密度为3.9W/cm2下,相对密度高于80%的AZO靶材,靶材寿命大于150 W·h。相对密度为94.79%的靶材在溅射功率30W下沉积20min得到薄膜的电阻率为3.14×10-4Ω·cm,平均透过率大于85%,具有(002)择优取向,满足薄膜太阳能对透明导电薄膜性能的要求。更多还原

【Abstract】 Transparent conductive film with high visible light transmittance and low resistivity can be used as flat panel displays and solar plane electrode materials. It can also be used in energy efficiency such as construction glass and automotive glass surfaces. The band gap of AZO transparent conductive film is 3.4 ev and its intrinsic absorption limit is 360 nm. It can reduce the absorption of light at P, N-type doping and improve the utilization of light energy. Therefore, AZO transparent conductive film is the appropriate window layer material. At the same time, AZO has lots of advantages such as good stability in plasma, simple preparation technology, easy to get, cheap raw materials, non-toxic which can be compared with ITO and make it a substitute for ITO.With the development of transparent conductive thin film, AZO sputtering target and the deposition technology of AZO film become a research hotspot. The main factors of film properties are target performance and film deposition process. Currently, AZO film deposition technology is more mature, but the porosity, pore evolution and microstructure in the hot pressing densification process and the impact on the film properties are rarely studied. Therefore, for the AZO target industrial development and thin-film solar industry, the study of hot pressing densification process of AZO target has an important significance.Firstly, AZO targets were prepared by hot-pressing using ZnO and Al2O3 mixture powder as raw materials with heating-rate of 20℃/min. Study about the influence of hot pressing process on target properties was carried on by method listed below:Archimedes method; Mercury intrusion porosimeter; SEM; XRD; Four-point probe meter. Results are as follows:Hot-pressing densification process of AZO target can be divided into two main stages with the rising of temperature.850℃-1100℃, with the rise of temperature, the distribution of pore size become concentrated as a result of merger and shrinkage of the channel pore volume and the content of the isolate volume has the lowest value at 1050℃-1100℃. The feature of this stage is that densification rate is fast and most holes are connected. When the temperature rise to 1100℃, with the continued mass transfer, pore volume is reduced and deformed gradually until all the pores become into isolation. The feature of this stage is that the content of isolate volume increased rapidly and densification rate is slower. According to the study about the influence of preserving time on hot pressing densification, we found that when the temperature is 1150℃, anti-densification phenomenon happens with extension of preserving time due to the increase of content of the isolate volume and the growth of the channel pore. According to the study about the influence of pressure on hot pressing densification, we found that larger pressure will promote the densification process at the same time lead to the increasing of content of the isolate volume.The densification process can be promoted by adding pressure in the heating process which can reduce the content volume of channel pore and isolate pore. According to the results of densification, AZO high-density target was prepared by process like this:1050℃, 60min and 1150℃,60min and its relative density is greater than 98%.Secondly, According to the study about composition of raw material, composition and structure of target, we found that some of Al element diffuses into the ZnO lattice, and the other part reacts to form ZnAl2O4 spinel because of limited solubility. During the hot pressing process, ZnAl2O4 compounds distributes at the ZnO grain boundary resulting in uneven distribution of composition effect of target due to the uneven distribution of Al elements.Finally, The RF magnetron coating test was carried on using the prepared targets as sputtering source. The thickness of the film was measured by Profiler. The transmittance was measured by UV spectrophotometer. The film resistivity was measured by Four-point probe meter and the phase structure was measured by X-ray diffraction. Coating test results are listed below:Under the same sputtering conditions, when the target porosity is lower, deposition rate can be faster and resistivity of film also is lower but the film transmittance was significantly reduced when the sputtering power is higher. The film has lower resistance when the target has smaller average pore size and concentrated pore size. When the power density is 3.9 W/cm2, the target life is less than 150 W·h when the relative density is lower than 80%.The film deposited for 20min under sputtering power 30W by the target which relative density is 94.79%has lower resistivity (3.14×10-4Ω·cm),greater transmittance (85%) and(002) preferred orientation,both which meets needs of transparent conductive oxide film for solar cell application.更多还原