Formation and superlattice of long-range and highly ordered alicyclic selenolate monolayers on Au(1 1 1) studied by scanning tunneling microscopy

Thermally Driven Structural Order of Oligo(Ethylene Glycol)-Terminated Alkanethiol Monolayers on Au(111) Prepared by Vapor Deposition

“…The STM images of Figure 2 a,b show that EG2 SAMs vapor-deposited on Au(111) at 298 K for 24 h have a fully disordered phase with many vacancy islands (VIs, dark defects). Such VIs, with a monatomic height of the Au lattice, could be formed through chemisorption of organic molecules containing an active anchoring group, such as sulfur or selenium, onto the gold surface, as reported in many previous papers [ 1 , 2 , 3 , 4 , 5 , 7 , 38 , 39 , 40 , 41 , 42 , 43 , 44 , 45 , 46 , 47 , 48 , 49 , 50 , 51 , 52 ]. Therefore, the presence of VIs in EG2 SAMs on Au(111) implies that chemisorbed EG2 monolayers were formed by vapor deposition, as is also the case with EG2 SAMs formed by solution deposition [ 39 ].…”

“…It has been demonstrated that higher thermal energy can greatly increase the diffusion rate of adsorbates and/or adsorbate–metal complexes during SAM formation, resulting in the formation of organic SAMs with improved structural quality showing large ordered domains and few structural defects [ 1 , 4 , 7 , 42 , 43 , 44 , 45 ]. When the vapor deposition temperature increases from 298 to 323 K, the surface features of the EG2 SAMs on Au(111) remarkably changed from the disordered phase to a mixed phase of ordered and disordered phases with many small bright aggregates (the white circle) on the entire Au(111) surface, as shown in Figure 2 c,d.…”

“…Closely packed and highly ordered self-assembled monolayers (SAMs) can be prepared by the spontaneous adsorption on metals of organic molecules containing chemically active sulfur, selenium, carboxylic or alkyne anchoring groups [ 1 , 2 , 3 , 4 , 5 , 6 , 7 , 8 , 9 , 10 , 11 , 12 , 13 , 14 , 15 , 16 , 17 , 18 , 19 , 20 ]. As a result, SAMs provide a very useful route for the fabrication of multifunctional molecular thin films that can be applied to various practical applications in the fields of biotechnology and nanotechnology [ 21 , 22 , 23 , 24 , 25 , 26 , 27 , 28 , 29 ].…”

“…It has been demonstrated that the domain formation and structural order of organic SAMs on metals are considerably influenced by SAM preparation conditions, such as deposition time, deposition temperature, deposition method (solution vs. vapor), and solvent properties [ 4 , 7 , 24 , 39 , 40 , 41 , 42 , 43 , 44 , 45 , 46 , 47 , 48 , 49 ]. Molecular-scale STM studies have shown that well-ordered organic thiol or selenol SAMs on Au(111) with large ordered domains and few structural defects are formed at high deposition temperatures [ 4 , 7 , 42 , 43 , 44 , 45 ]. It has been suggested that the markedly improved structural quality of organic SAMs at high deposition temperature is due to a lowering of the diffusion barrier of adsorbates during adsorption [ 50 ].…”

“…This enhancement is due to eliminating possible negative effects that can be induced by solvent-adsorbate interactions during self-assembly in solution [ 7 , 46 , 51 , 52 ]. In spite of numerous studies regarding the effect of deposition temperature on the formation and structure of alkanethiol and alkaneselenol SAMs [ 1 , 4 , 7 , 42 , 43 , 44 , 45 ], there are no molecular-scale STM studies to date regarding temperature-dependent OEG SAM formation on Au(111) by ambient-pressure vapor deposition.…”