Structure-building forces in biphenyl-substituted alkanethiolate self-assembled monolayers on GaAs(001)

• Verfasst von: Lu, Hao [VerfasserIn]
• Verfasst von: Zharnikov, Michael [VerfasserIn]
• Titel: Structure-building forces in biphenyl-substituted alkanethiolate self-assembled monolayers on GaAs(001)
• Titelzusatz: the effect of the bending potential
• Verf.angabe: Hao Lu and Michael Zharnikov
• E-Jahr: 2015
• Jahr: November 12, 2015
• Umfang: 9 S.
• Fussnoten: Gesehen am 03.06.2020
• Titel Quelle: Enthalten in: The journal of physical chemistry <Washington, DC> / C
• Ort Quelle: Washington, DC : Soc., 2007
• Jahr Quelle: 2015
• Band/Heft Quelle: 119(2015), 49, Seite 27401-27409
• ISSN Quelle: 1932-7455
• DOI: doi:10.1021/acs.jpcc.5b07067
• Datenträger: Online-Ressource
• Sprache: eng
• K10plus-PPN: 1699303223

Abstract

Molecular assembly on a technologically relevant GaAs substrate is an important and application-related issue. In this context, self-assembled monolayers (SAMs) formed from a series of ω-(4′-methylbiphenyl-4-yl)alkanethiols, CH3(C6H4)2(CH2)nSH (BPn, n = 1-6), were prepared on GaAs(001) and characterized in detail by high-resolution X-ray photoelectron spectroscopy and near-edge X-ray absorption fine structure spectroscopy. The resulting films exhibited pronounced, “odd-even” variation in molecular orientation and packing density with the number (n) of methylene groups in the alkyl linker; viz., smaller molecular inclination, associated with a higher packing density, was observed for an odd n, while the opposite was the case for an even n. Such an odd-even behavior confirms once again the existence of a bending potential for GaAs(001), which is equivalent to the analogous potential for the Au(111) substrate, where similar odd-even behavior has been observed. This potential plays an important role in the balance of the structure-building interactions, predefining the orientation of the alkyl linker, transferred in an odd-even fashion, depending on the parity of n, to the adjacent biphenyl spacer. The above effects were found to be superimposed onto pronounced dependence of the film quality on the length of the BPn precursor. This occurred due to proneness of the GaAs substrate to oxidation, hindering an efficient self-assembly, as well as due to a limited ability of the short-chain monolayers to protect this sensitive substrate from the postpreparation oxide regrowth. A proper selection of the parameters is, thus, very important for the design of functional monomolecular films on GaAs.