NSF: Direct Imaging of Charge Distribution in Ceramic Materials

如果知道一种物质中所有电子的位置，就不需要寻找原子核的位置了。这是一个非常有力的说法，虽然它可能不是在所有可能的情况下都是正确的，但对于许多材料来说是正确的。虽然我们在以原子分辨率投影确定材料局部结构的能力方面取得了进展，但几乎所有这些都集中在确定原子位置上。更困难的问题——确定电子的位置——还没有得到很好的发展，但如果可能的话，将为材料研究提供一个新的信息维度。如果成功，这类数据的潜在应用范围非常广泛，包括催化研究；作为新的电介质、铁电器件和在某些情况下的磁性器件以及氧传输膜和燃料电池；它对于在原子水平上理解许多腐蚀问题也是至关重要的。这些研究还将提供丰富的实验数据，与之相对的理论模型可以以比目前可能的更高的精度进行比较和校准。因此，我们提出的研究提出了一个巨大的挑战，即在纳米尺度上实验确定陶瓷材料中的局部电荷分布，并特别参考单个缺陷的研究。为了了解电荷分布对材料性质的影响，我们打算开发直接成像电荷的方法。我们特别希望研究电荷在表面和缺陷处的再分配，这通常对材料性能和器件性能至关重要。为了实现这一目标，我们将开发使用扫描隧道显微镜（STM）和高分辨率透射电子显微镜（HRTEM）成像电荷的实验方法。我们还将比较这两种提供互补信息的技术的结果。该项目将跨越两个国际领先的机构，一个在英国，一个在美国，每个机构都可以为此目的使用独特的仪器和计算。提案的每一部分都将提供新的通用方法，我们将在涉及一系列技术重要材料的开创性实验中使用这些方法。该项目的资助将资助两名在各合作机构工作的博士后研究人员，并提供旅费，使两个研究小组的成员能够在合作实验室工作。

If one knew the positions of all the electrons in a material, there would be no need to find where the nuclei are . This is a very strong statement, and whilst it may not true in all possible cases, for many materials it is. Whilst there have been developments in our ability to determine the local structure of materials at atomic resolution in projection almost all of these have focused on locating the atom positions. The more difficult problem of determining the positions of the electrons is much less well developed but, if possible would provide a new dimension of information in materials research. If successful, the potential application of this type of data is very wide ranging and includes studies of catalysis; as new dielectric, ferroelectric and in some cases magnetic devices and in oxygen transport membranes and fuel-cells; it is also critical to the understanding at the atomic level of many corrosion problems. These studies will also provide a rich seam of experimental data against which theoretical models can be compared and calibrated at far higher precision than is currently possible. Our proposed research therefore poses a Grand Challenge , namely the experimental determination of local charge distribution in ceramic materials at the nanoscale with particular reference to studies of individual defects. To understand the effects of charge distribution on material properties we intend to develop methods for directly imaging charge . In particular we wish to examine the redistribution of charge at surfaces and defects which are often crucial to materials properties and device performance. To achieve this we will develop experimental methods for imaging charge using both Scanning Tunneling Microscopy (STM) and aberration corrected High Resolution Transmission Electron Microscopy (HRTEM). We will also compare results from these two techniques which provide complementary information. This project will span two internationally leading institutions, one in the UK and one in the USA each of which has access to unique instrumentation and computation for this purpose. Each part of the proposal will deliver new general methodologies and we will utilize these in pioneering experiments involving a range of technologically important materials. Funding for this project will support two post doctoral research fellows working at each of the collaborating institutions together with travel costs to enable members of both research teams to work in the collaborating laboratories.