多孔阳极氧化铝的“逆向工程”—刻蚀研究

发布时间：2018-06-06 05:21

本文选题：多孔阳极氧化铝 + 刻蚀　；参考：《华南理工大学》2015年博士论文

【摘要】：阳极氧化是指利用电化学方法使金属表面钝化生成氧化膜的过程。铝的阳极氧化已有一百多年的研究历史,早期即在电解电容、金属防腐蚀和表面装饰等工业领域得到较广的应用。在最近二十年,多孔阳极氧化铝(Porous anodic alumina,PAA)显著的自组织行为的发现及其工艺简单、可控性高、成本低廉等优点使其逐渐成为一种极具潜力的纳米制备模板。目前,PAA在低维材料及相关器件制备方面已得到广泛的应用,在生物、新能源、传感器、信息储存等诸多新兴领域发挥着重要作用。而在基础研究方面,长期以来,关于PAA的生长机理至今仍存在不少疑问和分歧。刻蚀不仅是PAA模板制备过程中的一种常用工艺,同时也可以作为一种机理研究的有效手段。本论文主要利用湿化学法和离子束研磨的手段,分别从正面和背面对磷酸中生长的PAA进行刻蚀。通过电化学测试和扫描电镜观察系统分析PAA的刻蚀过程,并深入探讨所反映的PAA生长过程的重要信息。在研究PAA的正面刻蚀过程中,传统的填孔法存在明显的不足。脉冲阳极化测试采用脉冲式的测试信号,可以弥补填孔法的不足。与此同时,脉冲阳极化法还是研究阳极氧化的瞬态效应以及稳态的强场离子传导过程的有效手段。本实验利用脉冲阳极化测试、电容测试和扫描电镜表征的方法,获得了PAA在正面刻蚀过程中阳极化电压和阻挡层厚度随刻蚀时间的变化。根据结果进行估算,阳极氧化过程具有双层结构的阻挡层内电场分布大致均匀。对比通过水热处理生成的AlOOH/Al(OH)3以及特定电解液中在阻挡型膜表面形成的胶质层的电学性质,可以确认PAA的双层结构主要是通过固态过程形成的,而胶体化学过程并未如某些学者所认为的那样起到重要的作用。热处理使PAA内层和外层的化学刻蚀速率均降低;在强电场的作用下,经热处理的PAA阻挡层的化学刻蚀速率可以基本恢复到热处理以前的状态。这两种过程均可以用PAA微观结构的可逆变化来解释。在利用湿化学法和离子束研磨从背面对PAA阻挡层进行刻蚀的过程中,均发现了元胞内部圆周方向上显著的且相互对应的刻蚀各向异性。在元胞结点附近,刻蚀速率较高,从而形成凹陷;而在元胞边界中点附近,刻蚀速率较低,逐渐形成凸起的脊。在足够高的刻蚀衬比以及较大的孔径和较薄的阻挡层的条件下,阻挡层刚穿孔时可以清晰地观察到元胞中心附近的凹陷位置形成的对称小孔。小孔的扩大、合并以及中心残余圆顶的坍塌导致主要的规则圆孔的出现。这种新的开孔机制解释了先前研究在阻挡层刻蚀过程中初始穿孔不规则的实验现象,并首次揭示了阻挡层开孔直径与孔径的关系及其随刻蚀时间的变化规律。阻挡层背面刻蚀的各向异性难以用化学组成、表面曲率以及刻蚀液的扩散速率等因素的差异来解释,而更有可能是由残余应力的各向异性引起的。PAA元胞中心附近可能是压缩应力最大的区域,而在元胞边界区域,压缩应力的极小值和极大值分别出现在元胞结点和元胞边界中点附近。这种应力分布应该是具有特定几何结构的PAA元胞的内在属性,可以用生长过程中相邻元胞间的相互作用导致的应力叠加以及由于物质流动速率差异而引起的应力不均匀释放来解释。阻挡层背面刻蚀形成的图案揭示了应力分布与元胞排布的关系。正是在这种具有各向异性的应力的直接驱动下,元胞边界的运动导致PAA的自组织行为,而这种驱动力的大小与电流密度成正相关。基于PAA的可控刻蚀并结合生长条件控制、热处理等工艺,可以制备具有特定结构的PAA模板。在第二步阳极氧化进行合适的时间以后,通过较长时间的化学刻蚀扩孔,再进行较短时间的阳极氧化,可以制备上层较厚且孔径很大、而下层很薄且孔径很小的漏斗形PAA模板。这种漏斗形PAA有可能替代超薄PAA作为刻蚀和沉积掩模使用,从而在模板制备和应用过程中对操作的要求可以显著降低。二步阳极氧化后,在500°C下对PAA样品进行热处理,再重新阳极氧化使阻挡层的离子电导基本恢复,最后进行较长时间的化学刻蚀,可以制备孔道底部一段直径较大,而其余部分孔径较小的滴管形PAA模板。这种结构的PAA在药物控释方面有潜在的应用价值,并对PAA模板的阻挡层减薄以及从铝基上分离的工艺有参考意义。在滴管形PAA内部孔径突变结区域可以观察到显著的刻蚀各向异性。这种现象反映了阻挡层元胞内电场及空间电荷分布的各向异性以及在热处理和重新阳极氧化过程中的调整行为。利用热处理替代水热处理对通孔结构的PAA进行预晶化,再进行足够长时间的化学刻蚀扩孔,可以获得结构规则完整的内层六方骨架。这种改进方法简化了工艺流程,提高了工艺的稳定性和重复性,并扩大了适用范围。在利用刻蚀制备特殊结构的PAA的过程中,可以普遍采用电容法原位监测样品在各种条件下的刻蚀过程。这种方法简单易行,灵活有效,对缩短研究周期十分有利。
[Abstract]:Anodizing is the process of using electrochemical methods to passivate the metal surface to produce an oxide film. The anodic oxidation of aluminum has a history of more than 100 years, early in the industrial fields such as electrolytic capacitor, metal anticorrosion and surface decoration. In the last twenty years, the porous anodic alumina (Porous anodic alumina, PAA) The discovery of self-organized behavior and its simple process, high controllability and low cost make it a potential nanometer preparation template. At present, PAA has been widely used in the preparation of low dimensional materials and related devices, and plays an important role in many new fields, such as biology, new energy, sensor, information storage and so on. For a long time, there are still many questions and differences about the growth mechanism of PAA. Etching is not only a common process in the process of PAA template preparation, but also an effective means to study the mechanism. This paper mainly uses wet chemical method and ion beam grinding method, respectively from the front and the front. The PAA is etched on the back of phosphoric acid. The etching process of PAA is analyzed by electrochemistry and scanning electron microscopy, and the important information of the growth process of PAA is discussed. In the study of the positive etching process of PAA, the traditional hole filling method has obvious deficiency. Pulse positive test uses pulse test letter. At the same time, pulse anodization is an effective means to study the transient effect of anodic oxidation and the strong field ion conduction process in steady state. This experiment uses pulse positive polarization test, capacitance testing and scanning electron microscope characterization to obtain the polarization voltage and resistance of the PAA in the process of the frontal etching of Zhongyang. The thickness of the barrier thickness varies with the etching time. According to the results, the electric field distribution in the barrier layer of the double layer structure is roughly uniform according to the results. The electrical properties of the AlOOH/Al (OH) 3 generated by the hydrothermal treatment and the colloid layer formed on the surface of the barrier membrane in the specific electrolyte can confirm the main double layer structure of the PAA. It is formed by the solid process, and the colloidal chemical process does not play an important role as some scholars think. Heat treatment reduces the chemical etching rate of the inner and outer layers of PAA, and the chemical etching rate of the heat treated PAA barrier can be basically recovered to the state before heat treatment under the action of a strong electric field. Two All the processes can be explained by the reversible change in the microstructure of PAA. In the process of etching the PAA barrier layer from the back by the wet chemical method and the ion beam grinding, the significant and corresponding etching anisotropy in the circumferential circumferential direction of the cell is found, and the cell node is attached near, the etching rate is high, and the depression is formed. At the middle point of the cell boundary, the etching rate is low, and the ridge is gradually formed. Under the condition of enough high etching lining ratio and larger aperture and thinner barrier layer, the symmetrical small hole formed in the depression near the center of the cell can be clearly observed when the barrier layer has just perforated. The enlargement of the small holes, the merger and the central residual circle. The collapse of the top leads to the emergence of the main regular circular holes. This new opening mechanism explains the previous experimental phenomena of irregular initial perforation in the etching process of the barrier layer, and first revealed the relationship between the aperture diameter and the aperture of the barrier and its variation with the etching time. The anisotropy of the etching of the back layer is difficult to use. The difference in chemical composition, surface curvature and the diffusion rate of the etching solution is explained, and it is more likely that the.PAA cell center near the center of the residual stress may be the region with the largest compressive stress, while in the cell boundary region, the minimum and maximum of the compressive stress are present at the cellular node and the cell edge, respectively. The stress distribution should be the intrinsic property of the PAA cell with a specific geometric structure, which can be explained by the superposition of stress caused by intercellular interaction in the process of growth and the ununiform release of stress caused by the difference of material flow rate. The pattern formed by the etching on the back of the blocking layer reveals the need. It is the relationship between the force distribution and the cell arrangement. It is precisely under the direct drive of the anisotropic stress that the movement of the cellular boundary leads to the self organizing behavior of PAA, and the size of this driving force is positively related to the current density. Based on the controlled etching of the PAA and the control of the growth conditions, the heat treatment process can produce a specific junction. After second step anodization, after a suitable time of second step anodization, a long time chemical etching reaming and a shorter anodic oxidation can be used to prepare a funnel shaped PAA template with a thick upper layer and a very thin lower layer and a small aperture. This leaky bucket type PAA may replace ultra-thin PAA as etching and sinking. The requirements for operation in the preparation and application of the template can be significantly reduced. After two steps anodizing, the PAA sample is heat-treated at 500 C, and the ion conductance of the barrier layer is basically restored by anodizing, and a long time of chemical etching is carried out, and the diameter of the bottom section of the channel is larger. The other part of the smaller pore size PAA template. This structure has potential application value of PAA in drug controlled release. It has a reference significance to the thinning of the barrier layer of the PAA template and the separation process from the aluminum base. The significant etching anisotropy can be observed in the internal aperture mutation junction area of the burette shape PAA. This phenomenon is reflected in this phenomenon. The anisotropy of the electric field and space charge distribution in the barrier layer and the adjustment behavior in the process of heat treatment and anew anodic oxidation are used. The heat treatment is used to precrystallize the PAA of the porous structure by heat treatment instead of the hydrothermal treatment, and a long enough time of chemical etching reaming can be used to obtain the six square skeleton of the inner layer. The improved method simplifies the process flow, improves the stability and repeatability of the process, and expands the scope of application. In the process of using the etching to prepare the special structure of PAA, the capacitance method can be widely used to monitor the etching process in situ under various conditions. This method is simple, flexible and effective, and can shorten the study cycle very well. It's good.
【学位授予单位】：华南理工大学
【学位级别】：博士
【学位授予年份】：2015
【分类号】：TN305.7

【共引文献】