Chemical imaging of insulators by STM
Chemical imaging of insulators by STM
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通过 STM 对绝缘体进行化学成像
DOI：
10.1103/physrevb.59.10356
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发表时间：
1999
影响因子：
3.7
通讯作者：
F. Himpsel
中科院分区：
文献类型：
--
作者：
J. Viernow;D. Petrovykh;A. Kirakosian;J.;F. Men;M. Henzler;F. Himpsel
利用Si（111）上的${\mathrm{CaF}_{2}$和${\mathrm{CaF}}_{1}$纳米结构来演示绝缘体的化学成像方法。在扫描隧道显微镜中，通过在低于导带最小值的偏置电压下隧道电流的急剧下降来实现化学灵敏度。这种成像方法具有优于1 nm的空间分辨率，并区分不同的氧化态。在导带最小值处发现了$（dI/dV）/（I/V）$中的谐振，这使得能够准确地确定其位置。我们观察到的增强高达5倍，绝对值在20\char21{}50的范围内，相比之下，欧姆金属为1。一个最小的模型给出，解释的共振隧穿在一个薄的绝缘膜。这些方法应普遍适用于确定当地的肖特基势垒和纳米结构中的带偏移和绝缘体和宽禁带半导体的化学选择性成像。
Nanostructures of ${\mathrm{CaF}}_{2}$ and ${\mathrm{CaF}}_{1}$ on Si(111) are used to demonstrate a chemical imaging method for insulators. Chemical sensitivity is achieved in scanning tunneling microscopy via a sharp drop of the tunneling current for bias voltages below the conduction-band minimum. This imaging method has a spatial resolution of better than 1 nm and distinguishes different oxidation states. A resonance is found in $(dI/dV)/(I/V)$ at the conduction-band minimum that enables an accurate determination of its position. We observe enhancements by up to a factor of 5 and absolute values in the range of 20\char21{}50, compared to 1 for an Ohmic metal. A minimal model is given, explaining the resonance in terms of tunneling across a thin insulator film. These methods should be generally applicable for determining local Schottky barriers and band offsets in nanostructures and for chemically selective imaging of insulators and wide-gap semiconductors.