Shapir Errez, Yi Juyeon, Cohen Hezy, Kotlyar Alexander B, Cuniberti Gianaurelio, Porath Danny
J Phys Chem B. 2005 Aug 4;109(30):14270-4. doi: 10.1021/jp052738e.
DNA has been at the center of an imaging effort since the invention of the scanning tunneling microscope (STM). In some of the STM imaging reports the molecules appeared with negative contrast, i.e., "submerged" under the metal background and darker. We demonstrate the phenomenon of contrast inversion in DNA STM imaging by controlled and spontaneous contrast inversions and by the dependence of the DNA apparent height with respect to the surface on the imaging bias voltage. Using these characterizations, we formulate a model explaining the above phenomenon by resonant tunneling through virtual states in the vacuum between the STM tip and the DNA molecule.
自扫描隧道显微镜（STM）发明以来，DNA一直是成像研究的核心。在一些STM成像报告中，分子呈现负对比度，即在金属背景下“下沉”且颜色更暗。我们通过可控的和自发的对比度反转以及DNA表观高度相对于表面随成像偏置电压的变化，证明了DNA STM成像中的对比度反转现象。利用这些特征，我们构建了一个模型，通过STM针尖与DNA分子之间真空中的虚拟态的共振隧穿来解释上述现象。
