Self-assembled monolayers (SAMs) of alkanethiols and dialkanethiols on gold are key elements for building many systems and devices with applications in the wide field of nanotechnology. Despite the progress made in the knowledge of these fascinating two-dimensional molecular systems, there are still several “hot topics” that deserve special attention in order to understand and to control their physical and chemistry properties at the molecular level. This critical review focuses on some of these topics, including the nature of the molecule–gold interface, whose chemistry and structure remain elusive, the self-assembly process on planar and irregular surfaces, and on nanometre-sized objects, and the chemical reactivity and thermal stability of these systems in ambient and aqueous solutions, an issue which seriously limits their technological applications (375 references).

Self-assembled monolayers of thiols and dithiols on gold: new challenges for a well-known system

Carbene Ligands in Surface Chemistry: From Stabilization of Discrete Elemental Allotropes to Modification of Nanoscale and Bulk Substrates

Organic electronics have emerged as a viable competitor to amorphous silicon for the active layer in low-cost electronics. The critical performance of organic electronic materials is closely related to their morphology and molecular packing. Unlike their inorganic counterparts, polymers combine complex repeat unit structure and crystalline disorder. This combination prevents any single technique from being able to uniquely solve the packing arrangement of the molecules. Here, a general methodology for combining multiple, complementary techniques that provide accurate unit cell dimensions and molecular orientation is described. The combination of measurements results in a nearly complete picture of the organic film morphology.

Molecular characterization of organic electronic films.

Exploiting electron spectroscopies to probe the structure and organization of self-assembled monolayers: a review

In the last two decades surface science techniques have decisively contributed to our present knowledge of alkanethiol self-assembled monolayers (SAMs) on solid surfaces. These organic layers have been a challenge for surface scientists, in particular because of the soft nature of the organic material (which can be easily damaged by irradiation), the large number of atoms present in the molecules, and the complex physical chemistry involved in the self-assembly process. This challenge has been motivated by the appealing technological applications of SAMs that cover many fields of the emerging area of nanotechnology. Sulfur (S) is closely related to alkanethiols and can be used to understand basic aspects of the surface structure of SAMs. In this review we focus on the atomic/molecular structures of S-containing SAMs on Au(111). Particular emphasis is given to the substrate, adsorption sites, chemical state of the S–metal bond and also to the experimental and theoretical tools used to study these structures at the atomic or molecular levels.

https://iopscience.iop.org/article/10.1088/0953-8984/18/48/R01/pdf

Surface characterization of sulfur and alkanethiol self-assembled monolayers on Au(111)

The chemisorption of 1-decanethiol on the Au(111) single crystal has been studied with synchrotron-based, high-resolution photoemission spectroscopy with molecular film prepared from both gas-phase dosing and solution immersion to vary surface coverage over a wider range. The structure of the molecular film, determined separately via low-energy electron diffraction, includes a c(23 × √3) stripe phase and c(3 × 2√3) saturated phases. Careful curve fitting of the S 2p2/3 core level reveals that there is only one sulfur species at a binding energy of 162.1 eV in the film and the spectrum of the S 2p core level does not vary with the surface coverage and existence temperature of the decanethiolate. This finding is inconsistent with the sulfur-pairing model proposed based on X-ray scattering and standing wave studies. Up to two C 1s core levels at 284.0 and 285.0 eV can be observed, depending on the surface coverage. Angle-resolved X-ray photoelectron spectroscopy measurements are utilized to provide a direct ...

High-resolution XPS study of decanethiol on Au(111): Single sulfur-gold bonding interaction

Enhanced and anisotropic field-effect mobility of thin-film transistors based on pentacene was obtained on a substrate covered with a prerubbed, self-assembled monolayer (SAM) of n-alkyltrichlorosilane. The field-effect mobility along the rubbing direction increased by a factor of ∼15 on rubbed n-nonyltrichlorosilane-modified surface, whereas on n-octadecyltrichlorosilane-modified surface, an increase by a factor of 2–4 was observed. The structures of pentacene films deposited on the SAM/rubbed SAM were characterized by powder x-ray diffraction, atomic force microscopy, and carbon K-edge near edge x-ray fine structure spectroscopy. An in-plane alignment effect on the pentacene packing and film morphology is proposed.

Anisotropic field-effect mobility of pentacene thin-film transistor: Effect of rubbed self-assembled monolayer

We have achieved a growth of highly oriented crystalline pentacene thin films, with preferred a−b in-plane orientation with respect to the rubbing direction of a rubbed polymethylene surface. The polymethylene thin film, generated on a gold surface by gold-catalyzed decomposition of diazomethane, was annealed and gently rubbed in a fixed direction by a flannelette cloth to serve as an alignment layer during the deposition of pentacene molecules. Various surface analysis techniques, including reflection absorption IR spectroscopy (RAIRS), near-edge X-ray absorption fine structure (NEXAFS) spectroscopy, grazing incidence X-ray diffraction (GIXD), and atomic force microscopy were used to elucidate the structural details of the polymethylene and the pentacene thin films deposited on it. Two crystalline morphologies of pentacene thin film were observed:  the minor one of rod-like molecular crystals having their long axes of the crystals perpendicular to the rubbing direction, and the dominant one of platelet-l...

Liang-Jen Fan

Papers

High-resolution XPS study of decanethiol on Au(111): Single sulfur-gold bonding interaction

Anisotropic field-effect mobility of pentacene thin-film transistor: Effect of rubbed self-assembled monolayer

Oriented Growth of Crystalline Pentacene Films with Preferred a-b in-Plane Alignment on a Rubbed Crystalline Polymethylene Surface

Molecular orientation and bonding of terthiophene-thiol self-assembled on Au(111): A combined NEXAFS and XPS study.