Adsorption and Reaction at Ferroelectric Surfaces: Chemical Switches and Switchable Chemistry

铁电表面的吸附和反应：化学开关和可开关化学

• 批准号: 0809841
• 负责人: Eric Altman
• 金额: $ 38.77万
• 依托单位: Yale University
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2008
• 资助国家: 美国
• 起止时间: 2008-07-01 至 2012-06-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0809841&HistoricalAwards=false
• 关键词: Adsorption; Reaction; Ferroelectric; Surfaces; Chemical

In this research supported by the Analytical and Surface Chemistry Program, we will investigate the conditions under which ferroelectric materials in thin film form can be used as chemical sensors as well as more broadly elucidate the fundamental factors that govern chemistry at the surfaces of these materials. Ferroelectrics are materials that develop macroscopic electric fields that can be switched by applying an external field in analogy to ferromagnets. The electric fields create high surface energies that drive surface restructuring and adsorption of polar molecules; in recent work we have shown that the adsorption is sensitive to the direction of the ferroelectric poling. In this project, we seek to exploit this finding to instead switch the polarization of a thin ferroelectric film where the differences in adsorption energies are sufficient to drive a change in the polarization direction. Because the poling direction can be readily detected, it is anticipated that this effect can be exploited to form chemical sensors. In addition, we seek to further understand the roles of electrostatic, chemical, and structural effects in determining the magnitude of the effect of ferroelectric poling on surface chemistry. Based on the results, strategies will be employed to enhance the effect to not only influence adsorption but to also enable control of catalytic activity and selectivity by switching the ferroelectric polarization. These strategies include deposition of co-catalysts to impart complementary functionality to that found on at least one of the polar surfaces; and growth of reactive epitaxial oxide layers where structural differences on oppositely poled surfaces, would yield one side of the crystal unreactive.The project will have a broad impact through its contributions to education and training and emerging areas of science and technology. The students working on this project will get a unique opportunity to develop new strategies for chemical sensing and reversibly controlling surface chemistry. To meet these objectives the students will need to develop expertise in a number of fields including surface science, materials science, chemical kinetics and dynamics, and spectroscopy. Because of the large polarizations that develop in ferroelectrics, the results promise to broadly impact chemical sensing by making new types of chemical devices such as chemical switches where adsorption on the ferroelectric is sufficient to turn on a field effect transistor without requiring any gate voltage or even a gate electrode. Laying the groundwork for creating catalysts whose activity or selectivity can be altered by applying an electric field will impact catalysis by providing a new reversible lever to control reactions, which will particularly impact the emerging area of microreactors.

在这项由分析和表面化学计划支持的研究中，我们将研究薄膜形式的铁电材料可用作化学传感器的条件，并更广泛地阐明这些材料表面化学的基本因素。 铁电体是产生宏观电场的材料，该宏观电场可以通过施加类似于铁磁体的外部场来切换。 电场产生高的表面能，驱动表面重组和吸附的极性分子，在最近的工作中，我们已经表明，吸附是敏感的铁电极化的方向。 在这个项目中，我们试图利用这一发现，而不是切换的铁电薄膜的极化，吸附能的差异足以驱动极化方向的变化。 由于极化方向可以很容易地检测到，预计这种效果可以被利用来形成化学传感器。 此外，我们试图进一步了解静电，化学和结构的影响，在确定铁电极化的表面化学的影响的大小的作用。 基于这些结果，将采用策略来增强效果，不仅影响吸附，而且还能够通过切换铁电极化来控制催化活性和选择性。 这些战略包括沉积助催化剂，使至少一个极性表面上的功能得到补充;生长反应性外延氧化物层，使相反极性表面上的结构差异使晶体的一面不反应。从事该项目的学生将获得一个独特的机会，开发化学传感和可逆控制表面化学的新策略。 为了实现这些目标，学生将需要发展在许多领域的专业知识，包括表面科学，材料科学，化学动力学和动力学，以及光谱学。 由于铁电体中产生的大极化，这些结果有望通过制造新型化学器件（如化学开关）来广泛影响化学传感，其中铁电体上的吸附足以打开场效应晶体管，而不需要任何栅极电压甚至栅极电极。 为创造催化剂奠定基础，其活性或选择性可以通过施加电场来改变，这将通过提供一种新的可逆杠杆来控制反应来影响催化作用，这将特别影响微反应器的新兴领域。