Lauritsen Jeppe V, Foster Adam S, Olesen Georg H, Christensen Mona C, Kühnle Angelika, Helveg Stig, Rostrup-Nielsen Jens R, Clausen Bjerne S, Reichling Michael, Besenbacher Flemming
Interdisciplinary Nanoscience Center (iNANO) and Department of Physics and Astronomy, Aarhus University, 8000 Aarhus C, Denmark.
Nanotechnology. 2006 Jul 28;17(14):3436-41. doi: 10.1088/0957-4484/17/14/015. Epub 2006 Jun 20.
Atomic force microscopy in the non-contact mode (nc-AFM) can provide atom-resolved images of the surface of, in principle, any material independent of its conductivity. Due to the complex mechanisms involved in the contrast formation in nc-AFM imaging, it is, however, far from trivial to identify individual surface atoms or adsorbates from AFM images. In this work, we successfully demonstrate how to extract detailed information about defects and the chemical identity of adsorbates on a metal oxide surface from nc-AFM images. We make use of the observation that the apex of the AFM tip can be altered to expose either a positive or negative tip termination. The complementary set of images recorded with the two tip terminations unambiguously define the ionic sub-lattices and reveal the exact positions of oxygen vacancies and hydroxyl (OH) defects on a TiO(2) surface. Chemical specificity is extracted by comparing the characteristic contrast patterns of the defects with results from comprehensive AFM simulations. Our methodology of analysis is generally applicable and may be pivotal for uncovering surface defects and adsorbates on other transition metal oxides designed for heterogeneous catalysis, photo-electrolysis or biocompatibility.
非接触模式原子力显微镜（nc-AFM）原则上可以提供任何材料表面的原子分辨图像，而不受其导电性的影响。然而，由于nc-AFM成像中对比度形成涉及的复杂机制，从AFM图像中识别单个表面原子或吸附物绝非易事。在这项工作中，我们成功展示了如何从nc-AFM图像中提取有关金属氧化物表面缺陷和吸附物化学特性的详细信息。我们利用了这样一个观察结果，即AFM针尖的尖端可以被改变，以暴露正或负的尖端末端。用两种尖端末端记录的互补图像集明确地定义了离子亚晶格，并揭示了TiO(2)表面氧空位和羟基（OH）缺陷的确切位置。通过将缺陷的特征对比度模式与全面的AFM模拟结果进行比较，提取化学特异性。我们的分析方法普遍适用，对于揭示用于多相催化、光电分解或生物相容性的其他过渡金属氧化物上的表面缺陷和吸附物可能至关重要。
