Single versus Dual Attachment in the Adsorption of Diisocyanates at the Ge(100)-2 × 1 Surface

• Published in: Journal of physical chemistry. C 2012-06, Vol.116 (23), p.12670-12679
• Main Authors: Wong, Keith T, Chopra, Sonali N, Bent, Stacey F
• Format: Article
• Language: English
• ISSN: 1932-7447; 1932-7455
• DOI: 10.1021/jp302930g

Adsorption of bifunctional molecules on semiconductor surfaces must be understood in order to design systems that expose a free functional group on the surface for applications such as film growth by molecular layer deposition. In this study, we use Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, and density functional theory calculations to investigate the adsorption of three diisocyanate molecules, 1,4-diisocyanatobutane (1,4-DICB), 1,3-phenylene diisocyanate (1,3-PDIC), and 1,4-phenylene diisocyanate (1,4-PDIC), on the Ge(100)-2 × 1 surface. All three molecules undergo preferential [2 + 2] cycloaddition across the CN bond of the isocyanate, but they differ in the fraction that reacts with the surface through one or both isocyanate groups. All three adsorbates also form measurable quantities of side products involving less favorable [2 + 2] cycloaddition across the CO bond of the isocyanate. Our study shows that changing the backbone of a bifunctional molecule can have a large effect on the degree of dual attachment and that designing bifunctional molecules that react with the surface with high selectivity remains a challenge.