Rapid Self-Assembly of Alkanethiol Monolayers on Sputter-Grown Au(111)
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- 作者：Mitsuo Kawasaki ; Tomoo Sato ; Takumi Tanaka ; and Kazunori Takao
- 刊名：Langmuir
- 出版年：2000
- 出版时间：February 22, 2000
- 年：2000
- 卷：16
- 期：4
- 页码：1719 - 1728
- 全文大小：334K
- 年卷期：v.16,no.4(February 22, 2000)
- ISSN：1520-5827
文摘
Atomically flat, sputter-grown Au(111) films allowed well-ordered alkanethiol (exemplified by octanethiol)monolayers to be self-assembled from solution markedly faster and in larger domain sizes than previouslyreported. An X-ray photoelectron spectroscopy analysis showed that complete monolayer coverage wasreached by 0.2-60 min of incubation in 0.1-0.001 mM ethanolic solution at room temperature (~17 
C),with single-step (0.1 and 0.01 mM) or two-step (0.001 mM) adsorption kinetics. Increasing the temperatureto 35 C was enough to cause a single-step, diffusion-controlled adsorption also from the 0.001 mM solution,yielding the full monolayer coverage in approximately 10 min. Scanning tunneling microscopy (STM)imaging proved that well-ordered islands, with the (
3 × 3)R30 structure more-or-less strongly modulatedby the c(4 × 2) superlattice, begin to form at 0.6-0.7 monolayer coverage most likely by homogeneousnucleation and grow rapidly thereafter. This kinetics of ordering requiring the considerably high thresholdcoverage for the nucleation, but allowing the fast growth of the nuclei was independently confirmed bythe infrared reflection absorption spectroscopy. A typical c(4 × 2) domain size at the saturation coveragewas estimated to be no less than 10-15 nm, and the structural identity often seemed not to be disruptedeven across the etch pits. This superior structural order is reflected on the highest level of molecularresolution achieved by the in-air STM imaging. The expected registry of the (3 × 3)R30 or c(4 × 2)lattice with that of Au(111) was also confirmed. On Au films that were also sputter-grown but no longeratomically flat, we observed at least by 1 order of magnitude slower self-assembly.
C),with single-step (0.1 and 0.01 mM) or two-step (0.001 mM) adsorption kinetics. Increasing the temperatureto 35 C was enough to cause a single-step, diffusion-controlled adsorption also from the 0.001 mM solution,yielding the full monolayer coverage in approximately 10 min. Scanning tunneling microscopy (STM)imaging proved that well-ordered islands, with the (3 × 3)R30 structure more-or-less strongly modulatedby the c(4 × 2) superlattice, begin to form at 0.6-0.7 monolayer coverage most likely by homogeneousnucleation and grow rapidly thereafter. This kinetics of ordering requiring the considerably high thresholdcoverage for the nucleation, but allowing the fast growth of the nuclei was independently confirmed bythe infrared reflection absorption spectroscopy. A typical c(4 × 2) domain size at the saturation coveragewas estimated to be no less than 10-15 nm, and the structural identity often seemed not to be disruptedeven across the etch pits. This superior structural order is reflected on the highest level of molecularresolution achieved by the in-air STM imaging. The expected registry of the (3 × 3)R30 or c(4 × 2)lattice with that of Au(111) was also confirmed. On Au films that were also sputter-grown but no longeratomically flat, we observed at least by 1 order of magnitude slower self-assembly.