通过磁控溅射ZnO:Al薄膜中的缺陷调控薄膜的光学和电学性能及相关物理机制的研究

发布时间：2018-05-03 14:12

本文选题：磁控溅射 + 氧化锌薄膜　；参考：《中国科学技术大学》2016年博士论文

【摘要】：ZnO基薄膜从被发现起便受到广泛关注。其宽带隙,高激子复合能,储量丰富以及价格低廉等特性令其有着广阔的应用前景。目前制约ZnO基薄膜应用的主要因素有:(1)如何控制缺陷以及(2)如何制备稳定的p型ZnO基薄膜。前者影响ZnO基薄膜的光学和电学性能,比如A1掺杂ZnO薄膜的载流子浓度和迁移率目前与ITO相比仍然有一定差距;而后者则影响着ZnO基同质结的制备,目前报道的结果都差强人意。突破这两个瓶颈势必会让ZnO基薄膜的应用领域迅速扩展。磁控溅射方法是适合工业化生产的先进薄膜制备技术。通过磁控溅射可以制备大面积的致密薄膜,且薄膜附着力高、可重复性好。但另一方面,磁控溅射方法在制备氧化物薄膜时,高能离子对薄膜的轰击会在薄膜中引入丰富的缺陷并影响薄膜的微结构。对于ZnO基半导体薄膜材料,薄膜的电学性质和光学性质与材料的缺陷和微结构密切相关。因此,调控ZnO基薄膜材料中的缺陷和微结构以获得高性能的ZnO基薄膜具有重要的科学研究意义和应用背景。本文的工作主要以透明导电膜和P型ZnO为背景,以Al掺杂和Al-N共掺杂ZnO为研究对象,以对ZnO薄膜中缺陷的调控为手段,研究了磁控溅射方法制备的ZnO基薄膜材料的光学和电学性质的关键影响因素及物理机制,主要取得了以下一些研究成果:1.系统研究了氢气退火对磁控溅射AZO薄膜中缺陷演化及光学和电学性能的影响。HRTEM测试结果显示在～300℃下退火后的薄膜晶格内部的部分位错与层错数量会明显增加,打乱薄膜(002)晶面的周期性而使其晶粒尺寸减小;在高于500℃的温度下退火可以有效移除部分位错和层错,但同时会导致大量的锌空位(VZn)缺陷的产生。AZO薄膜在～500℃下退火后其内部的与氧有关的缺陷(如氧填隙Oi,晶界吸附氧OGB等)被大幅移除,使其载流子浓度、迁移率以及可见光波段的透过率都明显上升。在高于550℃的温度下退火将会导致严重的氢气刻蚀效应,使得大量AlZn施主被VZn钝化。此外,我们还在对样品热分析结果中发现了一个反常的吸热过程,并在氢气气氛下实时电阻率测量中发现了电阻率随温度的反常上升现象。基于这两个现象,我们讨论了Oi与Al施主和部分位错在氢气退火时的相互作用机制。我们的结果表明,在～500℃下退火后的AZO薄膜电阻率低至4.48×10-4Ωcm,而可见光波段透过率超过90%,已经可以满足作为透明导电薄膜在某些领域的应用条件。2.发现了磁控溅射AZO薄膜中Oi诱导的有效掺杂效应。初始薄膜中的Oi浓度可以通过调节溅射时的氧分压有效控制。尽管Al施主会暂时被Oi钝化,借助后续的氢气退火可以将Oi移除从而重新激活AlZn施主。测试结果显示Oi浓度最高的初始薄膜在氢气退火后有着最高的载流子浓度。实验结果表明,基于Oi诱导的有效掺杂效应,Al的有效掺杂浓度提高了～10%。我们提出尽管初始薄膜中Oi会钝化Al施主,但同时它们也有利于原子Al在晶格中的分布,促进AlZn施主缺陷的形成,从而增加氢气退火后薄膜中Al的有效掺杂。这种Oi诱导的有效掺杂效应为提高半导体材料的载流子浓度提供了新的思路,理论上也适用于其他透明导电氧化物薄膜材料,比如ITO。3.研究了通过溅射过程中掺H削弱溅射时高能氧负离子轰击影响的可行性。结果证明,溅射过程中掺H可以有效抑制薄膜中与O相关缺陷(Oi,Vo,OGB)的产生,削弱不均匀分布的氧负离子轰击对于AZO薄膜的影响,改善薄膜的光学和电学性能的空间分布。4.开发了利用自由基辅助磁控溅射方法制备p型Al-N共掺杂ZnO薄膜的技术。通过独立的射频源将N2转化成活性更高的N自由基并精确地控制溅射参数,获得了迁移率高达3.11 cm2/Vs的p型Al-N共掺杂ZnO薄膜,且在大气状态下存放一个月后仍然能保持p型导电特性。这证明通过磁控溅射制备大面积的p型ZnO基薄膜是可行的。
[Abstract]:ZnO based films have attracted wide attention from their discovery. Their wide band gap, high exciton composite energy, rich reserves and low price have broad application prospects. The main factors restricting the application of ZnO based films are: (1) how to control defects and (2) how to prepare stable P ZnO based thin films. The former affects ZnO based films. Optical and electrical properties, such as the carrier concentration and mobility of A1 doped ZnO films, still have a certain gap compared with ITO, and the latter affects the preparation of ZnO based homogeneity. The results of the present report are poor. The breakthrough of these two bottlenecks will make the ZnO based films expand rapidly. The magnetron sputtering method is suitable. The advanced film preparation technology produced by industrial production can prepare large area dense thin films by magnetron sputtering, with high adhesion and reproducibility. On the other hand, when the oxide film is prepared by magnetron sputtering, the bombardment of high energy ions on the film will lead to a rich defect in the film and influence the microstructure of the thin film. For Z The electrical properties and optical properties of nO based semiconductor thin film are closely related to the defects and microstructures of the materials. Therefore, it is of great scientific significance and application background to control the defects and microstructures in the ZnO based thin film materials to obtain high performance ZnO based films. The main work of this paper is the transparent conductive film and the P ZnO as the back. The key influence factors and physical mechanism of the optical and electrical properties of ZnO based thin film materials prepared by magnetron sputtering are studied with Al doping and Al-N Co doped ZnO as the research object. The main influencing factors and physical mechanism of the optical and electrical properties of the ZnO based thin film materials prepared by magnetron sputtering are studied. The main results are as follows: 1. the hydrogen annealing of the magnetron sputtering AZO thin is studied systematically. The influence of the defect evolution and optical and electrical properties in the membrane.HRTEM test results show that the partial dislocation and the number of stacking faults in the thin film lattice annealed at 300 centigrade will obviously increase, disrupt the periodicity of the film (002) and reduce the grain size, and the partial dislocation and layer can be effectively removed at a temperature above 500 degrees C. It is wrong, but it also causes a large number of zinc vacancy (VZn) defects to produce.AZO films at 500 degrees centigrade, and the internal oxygen related defects (such as oxygen gap Oi, grain boundary adsorbed oxygen OGB, etc.) have been greatly removed, so that the carrier concentration, mobility and the penetration rate in the visible light band are obviously increased. The annealing will be annealed at a temperature above 550 degrees C. A large number of AlZn donors were passivated by VZn. In addition, we also found an anomalous endothermic process in the thermal analysis of the samples, and the anomalous rise of resistivity with temperature was found in the real time resistivity measurement under hydrogen atmosphere. Based on these two phenomena, we discussed the donor of Oi and Al. Our results show that the resistivity of AZO films annealed at 500 C is low to 4.48 x 10-4 Omega cm, and the transmittance of visible light bands is over 90%, which can satisfy the application of transparent conductive thin film in some fields by.2. discovery of Oi induced by magnetron sputtering AZO film. The effective doping effect. The Oi concentration in the initial film can be effectively controlled by adjusting the oxygen partial pressure at the sputtering. Although the Al donor is temporarily passivated by Oi, the Oi can be removed by subsequent hydrogen annealing to reactivate the AlZn donor. The test results show that the highest Oi concentration of the initial film has the highest carrier concentration after the annealing of hydrogen. The experimental results show that, based on the effective doping effect induced by Oi, the effective doping concentration of Al is increased to 10%.. We suggest that although Oi will passivate Al donor in the initial film, they also benefit the distribution of atomic Al in the lattice, promote the formation of AlZn donor defects, and increase the effective doping of Al in the thin film after hydrogen annealing. The effective doping effect induced by Oi provides a new idea to improve the carrier concentration of semiconductor materials. In theory, it is also suitable for other transparent conductive oxide film materials. For example, ITO.3. studies the feasibility of using H to weaken the impact of high energy oxygen ion bombardment during sputtering. The results show that the doping of H can be used in the sputtering process. The production of O related defects (Oi, Vo, OGB) in the film is effectively suppressed, and the effect of negative oxygen ion bombardment on the AZO film is weakened, and the spatial distribution of the optical and electrical properties of the film is improved. The technology for the preparation of P type Al-N Co doped ZnO thin films by free radical Assisted Magnetron sputtering is developed. A independent RF source is used for N2. It is converted into a higher active N radical and accurately controlling the sputtering parameters. The P Al-N Co doped ZnO film with a high mobility of 3.11 cm2/Vs is obtained, and the P type conductive property can still be maintained after a month in the atmosphere. It is proved that it is feasible to prepare a large area of P type ZnO based thin film by magnetron sputtering.

【学位授予单位】：中国科学技术大学
【学位级别】：博士
【学位授予年份】：2016
【分类号】：TB383.2

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