Abstract
High-resolution photoemission spectroscopy (HRPES) measurements were collected and density functional theory (DFT) calculations were performed to track the exposure-dependent variation of the adsorption structure of 2-thiophenecarboxaldehyde (C4H3SCHO: TPCA) on the Ge(100) 2 × 1 reconstructed surface at room temperature. In an effort to identify the most probable adsorption structures on the Ge(100)-2 × 1 reconstructed surface, we deposited TPCA molecules at low exposure and at high exposure and compared the differences between the electronic features measured using HRPES. The HRPES data suggested three possible adsorption structures of TPCA on the Ge(100)-2 × 1 reconstructed surface, and DFT calculations were used to determine the plausibility of these structures. HRPES analysis corroborated by DFT calculations, indicated that an S-dative bonded structure is the most probable adsorption structure at relatively low exposure levels, the [4 + 2] cycloadduct structure is the second most probable structure, and the [2 + 2]-C=O cycloadduct structure is the least probable structure on the Ge(100)-2 × 1 reconstructed surface at relatively high exposure levels.
Highlights
Many research groups have been studying structures of biomolecules adsorbed onto semiconductor surfaces in connection with the development of bio-related applications [1,2,3,4,5]
In terms of developing the other thiol detection applications, we have examined sulfur-containing compounds to understand how these molecules behave on the Ge(100)-2 × 1 reconstructed surface at room temperature. 2-Thiophenecarboxaldehyde (TPCA) is a good test molecule as a detector because its molecular structure is relatively simple and sensitive
The exposure-dependent electronic and adsorption structures were obtained from the High-resolution photoemission spectroscopy (HRPES) data
Summary
Many research groups have been studying structures of biomolecules adsorbed onto semiconductor surfaces in connection with the development of bio-related applications [1,2,3,4,5]. The zwitterionic dimers of the Ge(100)-2 × 1 reconstructed surface act as Lewis bases and acids, which facilitate the adsorption of molecules with multifunctional groups [8,9,10]. Recent studies have shown that thiol groups react with Ge(100)-2 × 1 reconstructed surface under photo-excitation with 510 nm light. This reaction is useful as a photo-induced thiol detector [11,12]. We sought to compare the adsorption structures of thiophene and TPCA on the Ge(100)-2 × 1 reconstructed surface using high-resolution photoemission spectroscopy (HRPES) and density functional theory (DFT) calculations
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