Tunneling Voltage Polarity Dependent Submolecular Contrast of Naphthalocyanine on Graphite. A STM Study of Close-Packed Monolayers under Ultrahigh-Vacuum Conditions
Tunneling Voltage Polarity Dependent Submolecular Contrast of Naphthalocyanine on Graphite. A STM Study of Close-Packed Monolayers under Ultrahigh-Vacuum Conditions
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DOI：
10.1021/jp036698v
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发表时间：
2004-01
影响因子：
3.3
通讯作者：
M. Lackinger;T. Müller;Thiruvancheril G. Gopakumar;F. Müller;and Michael Hietschold;G. Flynn
中科院分区：
文献类型：
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作者：
M. Lackinger;T. Müller;Thiruvancheril G. Gopakumar;F. Müller;and Michael Hietschold;G. Flynn
在类似的酞菁薄膜的背景下，研究了自由基萘菁自组装单分子膜，揭示了更广泛的π-电子体系对单层膜性能的影响。利用扫描隧道显微镜(STM)，在超高真空条件下，在石墨衬底上气相沉积了一种新型的金属间化合物，并对其进行了低温(50K)的原位研究。通过亚分子分辨STM图像确定了沉积薄膜的单层晶胞参数。此外，单分子膜中的空位使得能够准确地测量单分子方位角。在具有亚分子分辨率的STM形貌中，占据和未占据样本态对应的隧穿图像有明显的区别。通过考虑孤立分子的前线轨道，可以定性地理解STM图像所显示的分子内结构。此外，单点隧穿光谱还显示出明显的单点隧穿光谱特征。
Self-assembled monolayers of free-base naphthalocyanine are examined in the context of analogous phthalocyanine films, revealing the influence of the more extended π-electron system on monolayer properties. Naphthalocyanine was vapor-deposited on a graphite substrate in ultrahigh vacuum and investigated in situ at low temperature (50 K) using scanning tunneling microscopy (STM). The crystallographic monolayer parameters of the deposited films were determined by means of submolecularly resolved STM images. In addition, vacancies in the monolayer have allowed for an accurate measurement of single molecule azimuthal angles. In STM topographs with submolecular resolution, a clear difference is evident between tunneling images corresponding to occupied and unoccupied sample states. The intramolecular structure exhibited by the STM images can be understood qualitatively by considering frontier orbitals calculated for isolated molecules. Moreover, single point tunneling spectra show a distinct signature of the o...