V Bakul Institute for Superhard Materials of the National Academy of Sciences of Ukraine, 2, Avtozavodskaya Str., Kiev, 04074, Ukraine.
Nanotechnology. 2014 Jan 17;25(2):025706. doi: 10.1088/0957-4484/25/2/025706. Epub 2013 Dec 12.
The spatial resolution of a scanning tunneling microscope (STM) can be enhanced using light element-terminated probes with spatially localized electron orbitals at the apex atom. Conductive diamond probes can provide carbon atomic orbitals suitable for STM imaging with sub-Ångström lateral resolution and high apex stability crucial for the small tunneling gaps necessary for high-resolution experiments. Here we demonstrate that high spatial resolution can be achieved in STM experiments with single-crystal diamond tips, which are generally only considered for use as probes for atomic force microscopy. The results of STM experiments with a heavily boron-doped, diamond probe on a graphite surface; density functional theory calculations of the tip and surface electronic structure; and first-principles tunneling current calculations demonstrate that the highest spatial resolution can be achieved with diamond tips at tip-sample distances of 3-5 Å when frontier p-orbitals of the tip provide their maximum contribution to the tunneling current. At the same time, atomic resolution is feasible even at extremely small gaps with very high noise in the tunneling current.
扫描隧道显微镜（STM）的空间分辨率可以通过使用具有尖端原子处空间局域电子轨道的轻元素终止探针来提高。导电金刚石探针可以提供适合 STM 成像的碳原子轨道，具有亚埃横向分辨率和高尖端稳定性，这对于实现高分辨率实验所需的小隧道间隙至关重要。在这里，我们证明了具有单晶金刚石尖端的 STM 实验可以实现高空间分辨率，而金刚石尖端通常仅被认为是用于原子力显微镜探针的材料。在石墨表面上使用重掺杂硼的金刚石探针进行 STM 实验的结果；尖端和表面电子结构的密度泛函理论计算；以及第一性原理隧道电流计算表明，当尖端的前沿 p 轨道对隧道电流的贡献最大时，在尖端-样品距离为 3-5 Å 时可以实现最高的空间分辨率。同时，即使在隧道电流噪声非常大的极小间隙中，也可以实现原子分辨率。
