SCANNING TUNNELING MICROSCOPY OF ETHANETHIOLATE AND NORMAL-OCTADECANETHIOLATE MONOLAYERS SPONTANEOUSLY ADSORBED AT GOLD SURFACES
SCANNING TUNNELING MICROSCOPY OF ETHANETHIOLATE AND NORMAL-OCTADECANETHIOLATE MONOLAYERS SPONTANEOUSLY ADSORBED AT GOLD SURFACES
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DOI：
10.1021/ja00008a001
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发表时间：
1991-04-10
影响因子：
15
通讯作者：
PORTER, MD
中科院分区：
文献类型：
--
作者：
WIDRIG, CA;ALVES, CA;PORTER, MD
利用扫描隧道显微镜（STM）研究了在云母表面外延生长的Au（111）薄膜上自发吸附的乙硫醇（ET）和正十八硫醇（OT）的单层膜。所得到的原子分辨图像是首次报道的金吸附的有机硫酸盐分子，并揭示了覆盖层的包装排列。隧穿假定发生在显微镜尖端和正烷硫酸盐头基团的金结合硫之间。对于ET和OT单层，所观察到的图像对应于六边形排列的吸附物阵列，其最近邻和次近邻间距分别为0.50 +/- 0.02和0.87 +/- 0.04 nm。这种填充与最近氦衍射和电子衍射研究中确定的Au（111）上的长链n-烷硫酸盐单分子层的（平方根3BAR X平方根3BAR） r30度结构非常吻合。此外，具有上述间距的图像在从几平方纳米到大约600纳米2的区域内表现出连续性，这表明STM在探测有机单层膜的短期和长期顺序方面具有潜在的实用性。这些图像的结构解释是在分子水平描述的背景下提出和检查的，这些描述是最近从这些单层的宏观表征研究中发展起来的。
Monolayer films from ethanethiol (ET) and n-octadecanethiol (OT) spontaneously adsorbed onto epitaxially grown Au(111) films on mica were examined by scanning tunneling microscopy (STM). The resulting atomically resolved images are the first reported for gold-adsorbed organothiolate molecules and reveal the packing arrangement of the overlayer. Tunneling is presumed to occur between the microscope tip and the gold-bound sulfur of the n-alkanethiolate head group. For both the ET and OT monolayers, an image that corresponds to a hexagonally packed array of adsorbates with respective nearest-neighbor and next-nearest-neighbor spacings of 0.50 +/- 0.02 and 0.87 +/- 0.04 nm was observed. This packing agrees well with the (square-root 3BAR X square-root 3BAR)R30-degrees structure determined for long-chain n-alkanethiolate monolayers on Au(111) in recent helium diffraction 1 and electron diffraction 2 studies. Furthermore, images with the above spacings were found to exhibit continuity over areas from a few square nanometers up to about 600 nm 2, indicating the potential utility of STM for probing both the short- and long-range order of organic monolayer films. Structural interpretations of these images are presented and examined within the context of molecular level descriptions that have been recently developed from macroscopic characterization studies of these monolayers.