A Density Functional Theory Investigation of Carboranethiol Self-Assembled Monolayer on Au(111)

Isolated and full monolayer adsorption of various carboranethiol (C$_2$B$_{10}$H$_{12}$S) isomers on gold (111) surface have been investigated using both the standard and van der Waals density functional theoretical calculations. The effect of differing molecular dipole moment orientations on the low energy adlayer geometries, the binding characteristics and the electronic properties of the self-assembled monolayers of these isomers have been studied. Specifically, the binding energy and work function changes associated with different molecules show a correlation with their dipole moments. The adsorption is favored for the isomers with dipole moments parallel to the surface. Of the two possible unit cell structures, the (5$\times$5) was found to be more stable than the ($\sqrt{19}\times\sqrt{19}$)R23.4$^o$ one.Comment: 22 pages, 6 figures and 3 table

Ag(111) ve Au(111) yüzeyleri üzerinde süpersonik moleküler ışın tekniğiyle üretilen pentacene ince filmlerin, kuvars kristal mikro terazi ve helyum atomu difraksiyonu teknikleri ile incelenmesi ve optimizasyonu

TÜBİTAK TBAG Proje01.01.201

Mixed carboranethiol self-assembled monolayers on gold surfaces

Carboranethiol self-assembled monolayers on metal surfaces have been shown to be very convenient systems for surface engineering. Here we have studied pure and mixed self-assembled monolayers (SAMs) of three different carboranethiol (CT) isomers on gold surfaces. The isomers were chosen with dipole moments pointing parallel to (m-1-carboranethiol, M1), out of (m-9-carboranethiol, M9) and into (1-carboranethiol, 01) the surface plane, in order to investigate the effect of dipole moment orientation on the film properties. In addition, influence of the substrate surface morphology on the film properties was also studied by using flame annealed (FA) and template stripped (TS) gold surfaces. Contact angle measurements indicate that in M1/M9 and M1/01 mixed SAMs, M1 is the dominant species on the surface even for low M1 ratio in the growth solution. Whereas for 01/M9 mixed SAMs no clear evidence could be observed indicating dominance of one of the species over the other one. Though contact angle values were lower and hysteresis values were higher for SAMs grown on TS gold surfaces, the trends in the behavior of the contact angles with changing mixing ratio were identical for SAMs grown on both substrates. Atomic force microscopy images of the SAMs on TS gold surfaces indicate that the films have similar morphological properties regardless of mixing ratio