| AVS 59th Annual International Symposium and Exhibition | |
| Surface Science | Wednesday Sessions |
| Session SS+EM-WeA |
| Session: | Semiconductor Surfaces |
| Presenter: | B. Shong, Stanford University |
| Authors: | B. Shong, Stanford University S.F. Bent, Stanford University |
| Correspondent: | Click to Email |
Direct chemical functionalization of semiconductor surfaces with organic molecules has been gaining attention, in part due to its potential applications based on forming organic-inorganic interfaces with tailorable properties. Attachment of bifunctional molecule is important because of the possibility for manipulating the chemical properties of the surface to allow for successive reaction, for example by molecular layer deposition (MLD). Whether dual or single reaction occurs during adsorption of a bifunctional molecule is of critical interest. It is known that more singly-tethered adsorbates typically form at higher coverages, but most previous studies focused only on a few discrete coverages.
In this study, we investigate coverage-dependent adsorption behavior of resorcinol (1,3-benzenediol) on the Ge(100)-2 × 1 surface. In situ X-ray photoelectron spectroscopy and Fourier transform infrared spectroscopy experiments along with density functional theory calculations are combined to determine the products and reaction pathways. First, the results support our previous conclusion that molecular geometry is an important factor in the reactivity and stereoselectivity of rigid bifunctional adsorbates.1 Resorcinol is found to dually and singly attach on Ge(100) through its two hydroxyl groups, and the dually reacted adsorbate assumes only one configuration due to geometrical restrictions. Moreover, a detailed study with respect to coverage shows that the product distribution is strongly dependent on coverage in a nonlinear fashion with two distinct adsorption regimes. In the low coverage regime, a constant fraction of singly-attached adsorbates is observed, independent of coverage. On the other hand, the fraction of singly-bound adsorbates increases with coverage in the high coverage regime. The increase in singly-bound species at higher coverages is explained by surface crowding, with existing adsorbates blocking reactive sites. This study provides fundamental knowledge about the reactivity of bifunctional molecules on semiconductor surfaces.
1B. Shong, K. T. Wong, and S. F. Bent, J. Phys. Chem. C 116, 4705 (2012).