Reaction Behaviors of S‐, O‐, and N‐containing Aliphatic Molecules with a Propyl Moiety on Ge(100) Surface

Abstract

The reaction pathways of 1-propanethiol, 1-propanol, and propylamine molecules, containing a propyl moiety, on a Ge(100) surface were investigated using high-resolution photoemission spectroscopy (HRPES) experiments and density functional theory (DFT) calculations. Upon analysis of the HRPES data, the adsorption of 1-propanethiol and 1-propanol was found to occur through a dissociation reaction, whereas that of propylamine took place via N dative bonding at room temper-ature. On the basis of our DFT results, adsorption geometries and transition states for each of these molecules on the Ge(100) surface were confirmed. Systematic studies of S-, O-, and Ncontaining molecules, composed of an identical propyl moiety, on the Ge(100) surface provide insight into the adsorption mechanism of aliphatic molecules containing alkyl chains on the Ge(100) surface.

Coverage Dependent Structural Change in Tetrahydrothiophene Adsorbed on Ge(100) Surface

“…All of the S 2p spectra contain two distinct peaks at 162.1 and 164.3 eV (marked as S 1 and S 2 ), indicating the presence of two types of sulfur species of different chemical states. In earlier studies, S 2p 3/2 peaks observed in the range of 162.0–162.6 eV on the Ge(100) surface were ascribed to a neutral sulfur atom in the S–H dissociated species, whereas those observed in the range of 164.0–164.2 eV were attributed to a positively charged sulfur atom in an S dative-bonded structure. ,,− Accordingly, we assigned the peak at 164.3 eV in the S 2p core-level spectra to the molecularly adsorbed C 4 H 8 S–Ge structure, which has a positively charged sulfur atom, resulting from S dative bonding. In the case of previously reported adsorption of tetrahydrofuran on the Ge(100) surface, the O 1s peak related to an adsorption structure with an interdimer row Ge–(CH 2 ) 4 –O–Ge configuration, formed through a ring-opening reaction, appeared at the spectral position corresponding to the binding energy of a neutral oxygen atom .…”

“…According to previous studies, for the Ge−S−CH 2 −CH 3 and Ge−S−CH 2 −CH 2 −CH 3 configurations formed through the dissociation of ethyl disulfide and 1-propanethiol on a Ge(100) surface, the C 1s peak appeared as a single component at 284.4 and 284.6 eV, respectively. 11,14 The fact that the signals of all the carbon atoms in ethyl and propyl groups appeared at the same binding energy in earlier studies indicates that the binding energies of the first and second nearest carbon atoms next to the carbon atom directly bonded to the neutral sulfur atom should also be in the range of 284.4−284.6 eV. Thus, we infer that the C 1s peaks corresponding to C a and C β in Figure 2 are overlapped at 284.6 eV in the C 1s spectra.…”

“…The functionalization of group IV (100) semiconductor surfaces with organic molecules has attracted considerable attention because organic-functionalized semiconductors formed by surface chemical reactions can be applied in various devices, such as sensors and electronic devices. − To tailor the properties of (100) semiconductor surfaces through the covalent bonding of organic molecules, it is necessary to understand the adsorption reactions of organic molecules on semiconductor surfaces and their associated mechanisms. − Organic molecules with sulfur, oxygen, or nitrogen atoms are frequently used to functionalize semiconductor surfaces to achieve desired properties such as passivation, layer growth, and organic thin film growth. − In particular, sulfur-based molecules are known to be outstanding passivators on semiconductor surfaces. ,,− Tetrahydrothiophene is a five-membered heterocyclic molecule containing a sulfur atom that is commonly used as a catalyst in the hydrodesulfurization process. − Although several studies have investigated the adsorption behavior of tetrahydrothiophene on Au(111) and Pt(100) metal surfaces, , its adsorption on a semiconductor surface has not yet been reported. Because the adsorption of a molecule on a metal surface is generally different from that on a semiconductor surface, the adsorption of tetrahydrothiophene on (100) semiconductor surfaces should be investigated to understand its adsorption structure and the related reaction pathway.…”

Adsorption behavior of furan at Ge(100) surface

“…Since a dimer on the reconstructed (100) surface of a Group 14 semiconductor simultaneously exhibits π-bonding and zwitterion characteristics, it can react with organic molecules via cycloaddition and Lewis acid–base reactions 9 – 13 . Because a molecule containing two C=C bonds, such as butadiene, can act as a conjugated diene, a five-membered aromatic molecule containing a heteroatom and two C=C bonds in the ring system can also serve as a conjugated diene and initiate a [4 + 2] cycloaddition reaction with the surface dimer of Ge(100) or Si(100) while functioning as a dienophile 14 .…”