Single molecule observations of the adsorption sites of methyl isocyanide on Pt(111) by low-temperature scanning tunneling microscopy
Single molecule observations of the adsorption sites of methyl isocyanide on Pt(111) by low-temperature scanning tunneling microscopy
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DOI：
10.1021/jp063283b
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发表时间：
2006-10-19
影响因子：
3.3
通讯作者：
Kawai, Maki
中科院分区：
文献类型：
--
作者：
Katano, Satoshi;Herceg, Eldad;Kawai, Maki
用扫描隧道显微镜(STM)直接研究了甲基异氰酸酯(CNCH3)在铂(111)面上的局域结构。在低覆盖度时，CNCH3优先吸附在顶部位置，这与早先基于振动光谱的推断一致。当在50K的低覆盖度下给药时，分子倾向于吸附在其他CNCH3分子附近，并具有较好的根3a和根7a的距离，其中a=2.78埃是铂的晶格常数。然而，将表面退火到120K，导致分子更均匀地分离。在较高的覆盖率下，观察到CNCH3分子既占据顶部又占据两个桥位。在扫描隧道显微镜图像分析的基础上，CNCH3在0.33ML处形成了(2×3)周期的有序层。通过密度泛函理论(DFT)计算提供了吸附在顶端和双重桥位置上的CNCH3结构的更多细节。在饱和第一层(0.33ML)的覆盖率下，CNCH3的顶部和两重桥键合的占有率为1：1，这与实验反射吸收红外光谱(RAIRS)数据和DFT计算相结合的结果是一致的。
Scanning tunneling microscopy (STM) has been used to directly investigate the local structure of methyl isocyanide (CNCH3) adsorbed on Pt(111). At low coverages, CNCH3 is preferentially adsorbed at on-top sites, in agreement with earlier deductions based on vibrational spectroscopy. When dosed at low coverages at 50 K, the molecules tend to adsorb near other CNCH3 molecules with preferred distances of root 3a and root 7a, where a = 2.78 angstrom is the lattice constant of Pt. Annealing the surface to 120 K, however, results in a more uniform separation of the molecules. At higher coverages, the CNCH3 molecules are observed to occupy both on- top and two-fold bridge sites. On the basis of STM image analysis, CNCH3 forms an ordered layer of (2 x 3) periodicity at 0.33 ML. Additional details on the structures of CNCH3 adsorbed at the on- top and two-fold bridge sites are provided by density functional theory (DFT) calculations. At a coverage that saturates the first layer (0.33 ML), the occupation ratio for the on- top and two-fold bridge bonded CNCH3 is 1:1, which is consistent with the results obtained from the combined use of experimental reflection absorption infrared spectroscopy (RAIRS) data and DFT calculations.