Reactions of Etched, Single Crystal (111)B-Oriented InP To Produce Functionalized Surfaces with Low Electrical Defect Densities

Abstract

Synthetic routes have been developed that allow attachment of a variety of functional groups to etched, singlecrystal InP surfaces. Benzyl halides, alkyl halides, silyl halides, and esters reacted readily with InP to yield covalently attached overlayers on the semiconductor surface. High-resolution X-ray photoelectron spectroscopy (XPS) revealed that the functionalization chemistry was consistent with the reactivity of surficial hydroxyl groups. Analysis of the XP spectra of the (111)B-oriented (P-rich) face in ultrahigh vacuum revealed signals ascribable to a monolayer of oxidized P atoms on the etched (111)B InP surface. The lack of reactivity of the (111)A-oriented (In-rich) face with these same functionalization reagents is therefore attributed to the difference in the nucleophilicity and acidity of the In and P oxides that are present on the (111)A and (111)B faces, respectively. The coverage of benzylic groups obtained through functionalization of (111)B-oriented InP with benzyl halides was estimated to be 4 × 10 14 cm 2 . This coverage implies that the functionalization can only proceed at alternate surface P atom sites in this system, which is expected from molecular packing considerations of these particular functional groups. Photoluminescence decay measurements were performed to investigate the electrical properties of the etched and modified InP surfaces, and these data indicated that the surface recombination velocity of the functionalized InP surface was ≈10 2 cm s -1 . This low surface recombination velocity implies that <1 electrically active defect is present for every 10 5 atoms on the modified InP surface, indicating that high electrical quality can be maintained while introducing a variety of chemical functionalities onto the (111)B surface of InP.

Physicochemical and Electrochemical Properties of Etched GaP(111)A and GaP(111)B Surfaces

“…[31][32][33][34] For this study, we limit our focus to chemical etchants that do not rapidly and progressively dissolve bulk GaP through an electrochemical route ͓e.g., K 3 Fe͑CN͒ 6 in alkaline solution͔. 19 The short immersion times employed here limit etching to predominantly just the oxide ͑GaO x /PO x ͒ overlayers and near the surface GaP region ͓e.g., the etch rate for GaP in H 2 SO 4 ͑aq͒ is 0.01 nm s −1 , and that for HCl:HNO 3 is Ͻ17 nm s −1 ͔.…”

Wet Chemical Functionalization of GaP(111)B through a Williamson Ether-Type Reaction

“…14,25,32 The latter signal could be seen more definitively in the difference spectrum and was assigned to with P−OH surface moieties remaining on the surface after wet etching. 24, 25 Still, in the context of the present study, we further wished to establish whether the predominant surface reactivity was more oxide-like rather than phosphinelike (i.e., bonding through bare atop P atoms). Freshly etched GaP(111)B surfaces were exposed to boranes (BH 3 ·THF, BCl 3 , and BF 3 ·O(C 2 H 5 ) 2 ) in a dry glovebox in analogy to formation of phosphinoborane adducts.…”

Covalent Attachment and Characterization of Perylene Monolayers on Si(111) and TiO2 for Electron-Selective Carrier Transport

“…Quantification of the coverage of functionalized perylene molecules requires the utilization of a substrate overlayer model − as previously employed in our lab. , Detailed in the Supporting Information, the model contains distinct layers to account for photoelectron signals originating from the substrate, silane, perylene, and terminal ester or imide species. We confine such analyses to the interpretation of experimentally acquired N 1s-to-Si 2p ratios of 1a surfaces and to the acquired F 1s-to-Si 2p ratios of the 4a and 5a surfaces for the well-defined surface site spacing on chemically oxidized Si(111) as opposed to the highly textured TiO 2 surfaces.…”