Comparative Study for Displacement of Cyclohexanethiolate and Cyclohaxaneselenolate Self-Assembled Monolayers on Au(111) by Octanethiols

Formation and Surface Structures of Highly Ordered Self-Assembled Monolayers of Alkyl Selenocyanates on Au(111) via Ambient-Pressure Vapor Deposition

“…This can be supported by previous work showing that the strength of metal–metal bond in the surface can be weakened by chemisorption of adsorbates, resulting in an increase in the mobility of surface metal atoms . It is well known that the Se–Au bond is stronger than the S–Au bond. ,− As a result, surface gold atoms are more mobile when Se-containing molecules adsorbed on the gold surface. Similar structural transitions were observed for biphenyl-based SAMs when the S headgroup is substituted by the Se headgroup. , …”

“…The height difference between the bright and dark terraces was observed to be ∼2.4 Å, which is corresponding to a monatomic step height of the underlying Au(111) substrate. Therefore, the dark regions can be considered as vacancy islands that were usually observed for chemisorbed monolayer derived from organic molecules containing sulfur and selenium headgroups. ,,,,− For this reason, it is also clear that the bright domains with a striped phase are not due to the existence of multilayer. Vacancy islands with large lateral dimensions larger than 40 nm (Figure a) were formed as a result of the thermal healing effect, which has been usually observed for thiol SAMs. ,,,,,, Interestingly, small ordered domains with tridirectional orientations were also clearly observed inside large vacancy islands (indicated by a white line).…”

“…Recently, SAMs on metals derived from organic selenols or diselenides containing a selenium (Se) headgroup (belonging to the same valence electron configuration as sulfur) have been studied. Their fundamental aspects such as surface structures, thermal and electrochemical stabilities, binding energies, and charge-transport behaviors were elucidated in more detail. ,− Scanning tunneling microscopy (STM) observations revealed that dodecaneselenolate SAMs on Au(111) derived from dodecyl diselenide have very unique surface characteristics containing two different domains: a densely packed and distorted hexagonal structure with a Moiré pattern and a linear missing-row structure . STM measurements also showed that the surface structure and growth behavior of selenolate SAMs on Au(111) from dialkyl diselenides or diphenyl diselenide were markedly different from those of the corresponding alkanethiol SAMs. − 1-Adamanetaneselenol (with a spherical adamantyl backbone) led to the formation of complex selenolate SAMs with randomly distributed high-conductance molecules, which are completely different from adamantanethiolate SAMs with a uniform and highly ordered structure .…”

“…STM measurements also showed that the surface structure and growth behavior of selenolate SAMs on Au(111) from dialkyl diselenides or diphenyl diselenide were markedly different from those of the corresponding alkanethiol SAMs. − 1-Adamanetaneselenol (with a spherical adamantyl backbone) led to the formation of complex selenolate SAMs with randomly distributed high-conductance molecules, which are completely different from adamantanethiolate SAMs with a uniform and highly ordered structure . Several experimental and theoretical studies revealed that the binding strength of Se–Au in SAMs is stronger than that of S–Au, which results in the large differences in surface and physical properties of selenolate and thiolate SAMs on metals. ,− …”