Aluminum Oxide Thin Films from Aqueous Solutions: Insights from Solid-State NMR and Dielectric Response
Aluminum Oxide Thin Films from Aqueous Solutions: Insights from Solid-State NMR and Dielectric Response
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DOI：
10.1021/acs.chemmater.7b05078
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发表时间：
2018-11-13
影响因子：
8.6
通讯作者：
Hayes, Sophia E.
中科院分区：
文献类型：
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作者：
Cui, Jinlei;Kast, Matthew G.;Hayes, Sophia E.
在这里，我们采用Al-27固态核磁共振（SSNMR）和传统的光谱和显微镜技术相结合，以调查的结构演变的水溶液铝前体的均匀和光滑的氧化铝膜。该路线不涉及有机配体，并且依赖于脱水、脱羟基和硝酸盐损失来缩合和形成三维氧化铝结构。当薄膜在200-1100摄氏度的温度范围内演变时，局部化学环境被跟踪。Al-27 SSNMR显示，在200至800 ℃之间退火的非晶薄膜中，Al中心主要是四配位和五配位，而在800 ℃以上形成的晶相中，Al中心主要是四配位和六配位。水沉积的氧化铝膜的Al配位进行比较，从SSNMR研究的气相沉积的氧化铝薄膜的数据。此外，氧化铝基电容器的介电常数的测量和相关的SSNMR结果。氧化铝是用于保护涂层、催化剂和微电子应用的重要材料。对于后者的应用，无定形材料是优选的，但缺乏长程有序使结构表征和结构-性质关系的确定复杂化。溶液沉积方法是传统气相沉积方法的有吸引力的替代方案，因为前体通常在空气中稳定，并且它们能够在普通半导体晶片以及大面积和柔性衬底上印刷和直接光刻图案化，这对于按比例放大到窗户和光伏器件中的应用是有用的。
Here, we employ a combination of Al-27 solidstate nuclear magnetic resonance (SSNMR) and conventional spectroscopic and microscopic techniques to investigate the structural evolution of aqueous aluminum precursors to a uniform and smooth aluminum oxide film. The route involves no organic ligands and relies on dehydration, dehydroxylation, and nitrate loss for condensation and formation of the threedimensional aluminum oxide structure. Local chemical environments are tracked as films evolve over the temperature range 200-1100 degrees C. Al-27 SSNMR reveals that Al centers are predominantly four- and five-coordinate in amorphous films annealed between 200 and 800 degrees C and four- and six-coordinate in crystalline phases that form above 800 degrees C. The Al coordination of the aqueous-deposited aluminum oxide films are compared to data from SSNMR studies on vapor-phase-deposited aluminum oxide thin films. Additionally, dielectric constants of aluminum oxide-based capacitors are measured and correlated with the SSNMR results. Aluminum oxide is an important material for protective coatings, catalysis, and microelectronic applications. For the latter application, amorphous materials are preferred, but a lack of long-range order complicates structural characterization and determination of structure-property relationships. Solution deposition approaches are attractive alternatives to traditional vapor-phase deposition methods because precursors are commonly stable in air, and they enable printing and direct lithographic patterning on common semiconductor.wafers as well as large-area and flexible substrates-useful for scale-up to applications in windows and photovoltaic devices.