Covalent Functionalization of GaP(110) Surfaces via a Staudinger- Type Reaction with Perfluorophenyl Azide

Despite the markedly low chemical reactivity of the nonpolar (110) surfaces of III−V semiconductors, the covalent functionalization of GaP(110) surfaces with perfluorophenyl azide (PFPA) molecules by a Staudinger-type reaction occurs only slightly above room temperature (325 K). Scanning tunneling microscopy observations, combined with density functional theory calculations, support the formation of stable, covalent perfluorophenyl nitride (PFPN) molecule−surface bonds, which can be described as Lewis acidic Ga-stabilized phosphine imides. π−π stacking between aromatic, electron-deficient PFPN units results in compact, commensurate 2D molecular assembly at the surface. PFPA deposition on GaP(110) at room temperature with no additional annealing leads to an intermediate phase consistent with an alternating 1D array of physisorbed and chemisorbed molecular units. This work provides a new route for covalently bonding molecular linkages to the (110) surfaces of III−V semiconductors. C functionalization is widely used for tailoring the fundamental properties of semiconductor surfaces for a variety of applications. For example, controlled covalent attachment of molecular species onto III−V semiconducting surfaces is being pursued in areas that include sensing, electrooptical, and catalytic applications. For zinc-blende III− V semiconductors, the chemistry of the (100) and (111) surfaces is relatively well understood and a wealth of attachment strategies are known. However, these strategies do not apply to the (110) surface and covalent functionalization of this surface has been much less successful. The most promising approach so far has involved organothiol surface reactions, but the structure of the resulting molecule− surface bonds remains elusive. Poor stability and lack of long-range order at room temperature for the thiol-derived layers obtained in this way limit the utility of this functionalization strategy. The (110) surface is different from the more commonly studied crystal faces of zinc-blende III−V semiconductors in Received: October 24, 2016 Revised: October 27, 2016 Published: October 31, 2016 Article