Here, we employ a combination of ²⁷Al solid-state 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 three-dimensional aluminum oxide structure. Local chemical environments are tracked as films evolve over the temperature range 200–1100 °C. ²⁷Al SSNMR reveals that Al centers are predominantly four- and five-coordinate in amorphous films annealed between 200 and 800 °C and four- and six-coordinate in crystalline phases that form above 800 °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.

中文翻译：

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水溶液中的氧化铝薄膜：固态NMR和介电响应的见解

在这里，我们结合了²⁷ Al固态核磁共振（SSNMR）和常规的光谱和显微技术，研究了含水铝前驱物向均匀而光滑的氧化铝膜的结构演化。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°C的温度范围内演变时，会跟踪当地的化学环境。²⁷Al SSNMR揭示，在200至800°C之间退火的非晶膜中，Al中心主要为四坐标和五坐标，而在800°C以上形成的晶相中，Al中心为四坐标和六坐标。将水沉积氧化铝膜的Al配位与SSNMR研究的气相沉积氧化铝薄膜的数据进行比较。另外，测量基于氧化铝的电容器的介电常数并将其与SSNMR结果相关。氧化铝是用于保护涂层，催化和微电子应用的重要材料。对于后一种应用，首选非晶态材料，但缺乏长程有序则使结构表征和确定结构与特性之间的关系变得复杂。