Interplay of adsorbate-adsorbate and adsorbate-substrate interactions in self-assembled molecular surface nanostructures

Abstract

The adsorption of 2,6-naphthalenedicarboxylic acid (NDCA) molecules on the Ag(110), Cu(110), and Ag(111) surfaces at room temperature has been studied by means of scanning tunnelling microscopy (STM). Further supporting results were obtained using X-ray photoelectron spectroscopy (XPS) and soft X-ray absorption spectroscopy (XAS). On the Ag(110) support, which had an average terrace width of only 15 nm, the NDCA molecules form extended one-dimensional (1-D) assemblies, which are oriented perpendicular to the step edges and have lengths of several hundred nanometres. This shows that the assemblies have a large tolerance to monatomic surface steps on the Ag(110) surface. The observed behaviour is explained in terms of strong intermolecular hydrogen bonding and a strong surface-mediated directionality, assisted by a sufficient degree of molecular backbone flexibility. In contrast, the same kind of step-edge crossing is not observed when the molecules are adsorbed on the isotropic Ag(111) or more reactive Cu(110) surfaces. On Ag(111), similar 1-D assemblies are formed to those on Ag(110), but they are oriented along the step edges. On Cu(110), the carboxylic groups of NDCA are deprotonated and form covalent bonds to the surface, a situation which is also achieved on Ag(110) by annealing to 200 °C . These results show that the formation of particular self-assembled molecular nanostructures depends significantly on a subtle balance between the adsorbate-adsorbate and adsorbate-substrate interactions and that kinetic factors play an important role.

Self-assembly and ordering of C60 on the WO2/W(110) surface

“…The fabrication of complex organic molecular structures on technologically important substrates held together by weak and reversible van der Waals interactions, hydrogen bonds or electrostatic interactions has been a much investigated topic in the past ten years [1][2][3][4][5][6][7][8][9][10]. This controlled self-assembly of organic nanostructures offers a number of powerful approaches for the development of organic molecule-based devices, which possess functions such as rectifying, switching and sensing [1][2][3][4][5][6][7][8][11][12][13].…”

“…This controlled self-assembly of organic nanostructures offers a number of powerful approaches for the development of organic molecule-based devices, which possess functions such as rectifying, switching and sensing [1][2][3][4][5][6][7][8][11][12][13]. Fullerenes have attracted considerable attention in recent years due to their potential in surface chemistry and nanotemplating [13], non-linear optics [13,14], single-molecule transistors [11,15], and especially molecular electronics because of their tunable electronic properties, resulting in superconducting or semiconducting behaviour [11,16,17].…”

“…This information can be obtained by using a combination of scanning tunnelling microscopy and spectroscopy (STM and STS). STM is a highly local technique that has become a powerful tool for studying the adsorption geometry and the conformation and dynamics of single organic molecules and molecular assemblies on conducting substrates [1][2][3][4][5][6][7][8][9][10]. Over the last decade STM has been used intensively for the study of C 60 self-assembled layers on a variety of metal [21][22][23][24][25][26][27][28][29][30][31][32][33][34][35][36] and semiconductor [18,[37][38][39][40][41] surfaces.…”

Growth and ordering of Ni(II) diphenylporphyrin monolayers on Ag(111) and Ag/Si(111) studied by STM and LEED

“…The Ag/Si(111)-(√3 × √3)R30º surface was chosen since the porphyrin-substrate interaction is expected to be intermediate in strength between that of the clean Si surfaces and the Ag(111) (or hydrogen-passivated Si) [23,24,[27][28][29][30]. On the former surface the molecules form covalent bonds and are unable to diffuse and self-assemble into ordered structures at room temperature [30], while on the latter the molecules diffuse freely and may form islands [23,24,[27][28][29]. The results of this work yield important information on the conformational behaviour and structural properties of the NiDPP monolayers depending on the porphyrinsubstrate interaction.…”

Fe nanoclusters on the Ge(001) surface studied by scanning tunneling microscopy, density functional theory calculations and X-ray magnetic circular dichroism

“…The self-assembly of atoms or molecules into ordered surface-supported nanostructures is one of the key topics in solid state physics and surface science [1][2][3][4][5][6][7][8][9]. One major reason for this attention is the prospect of controlling atomic scale structures on surfaces, which can lead to mass fabrication of usable systems and novel devices.…”