Adsorption and Thermal Stability of Ethylene on Ge(100)

Abstract

We have investigated the adsorption structures and thermal desorption behavior of C 2 H 4 on Ge(100) using scanning tunneling microscopy (STM) and temperature programmed desorption (TPD) under ultrahigh vacuum (UHV). Ethylene molecules adsorb in two distinct bonding geometries: (i) on top of a single Ge-Ge dimer (on-top) and (ii) in a paired end-bridge between two neighboring Ge dimers within the same dimer row (paired end-bridge). Real-time STM images taken during the exposure of C 2 H 4 to Ge(100) show that the on-top configuration dominates over the paired end-bridge confiugration. The TPD measurements show that chemisorbed C 2 H 4 desorbs from Ge(100) nondissociatively with two different desorption features, denoted as R (385 K) and (405 K). Desorption follows first-order kinetics for both states; the desorption energies of the R (385 K) and (405 K) states are 1.05 and 1.15 eV, respectively. These desorption energies are about 0.6 eV lower than those of ethylene on Si(100), indicating that the Ge-C bond is weaker than the Si-C bond. STM measurements carried out after annealing Ge surface at various temperatures indicate that the R and states correspond to the on-top and paired end-bridge configurations, respectively.

Reaction Pathways of Acetylene Adsorption on the Ge(001) Surface

“…This indicates the reaction rate to form the end-bridge and paired-end-bridge adsorptions should be larger than the rate to form the di-σ adsorptions, which is conflicting with Cho and Kleinmanʹs calculation results. On the other side, the experimental results on the two molecules are in contrast to each other: paired-end-bridge structure has been observed to be dominant over the di-σ structure in the present case of C2H2, 9 and the population of di-σ structure is larger than that of the paired-end-bridge structure in the case of C2H4, 5 which is indeed consistent with our calculation results on C2H4/Ge(001). 8 In the present work, we re-study the adsorption and desorption kinetics of C2H2/Ge(001) by employing our experience in using the first-principles method based on the density functional theory (DFT) to examine small molecules on Si and Ge systematically, to understand the discrepancy between the experiment observation and theoretical calculation, and to dig out the root cause to the difference between the adsorptions of C2H2 and C2H4 on Ge(001) surface.…”

“…In order to study the potential of the assemble hydrocarbon layer on Ge(001) surface in production of molecular microelectronic and optoelectronic devices fabrication and stability, the interaction of unsaturated hydrocarbon molecules with Ge(001) surface has received more attention recently. [5][6][7] Ge dimer is the reactive center on the Ge(001) surface, thus, both the intradimer and interdimer adsorptions are possible for C2H4/Ge(001). The intradimer di-σ model has the two C atoms of the C2H4 bonded to the two Ge atoms of a single surface dimer, and the interdimer end-bridge model has the two C atoms bonded to the two Ge atoms on one side of two adjacent dimers along the dimer axis.…”

“…The intradimer di-σ model has the two C atoms of the C2H4 bonded to the two Ge atoms of a single surface dimer, and the interdimer end-bridge model has the two C atoms bonded to the two Ge atoms on one side of two adjacent dimers along the dimer axis. Kim et al 5 observed two distinct desorption features by their temperature-programmed desorption (TPD) measurements. According to their observed scanning tunneling microscopy (STM) features, these respective features were assigned as the di-σ and paired-end-bridge configurations in which an additional C2H4 molecule adsorption makes the end-bridge structure to be paired.…”

Adsorption dynamics of ethylene on Si(001)

“…17 Finally, we note that a similar mobile precursor state of C 2 H 4 was proposed for Ge(001) based on STM adsorption experiments. 30,31 In contrast to C 2 H 4 /Si(001), a change from overall non-activated to activated adsorption at increased surface coverage was suggested for C 2 H 4 /Ge(001). 32 Thus, a comparative study of the dynamics of C 2 H 4 on Ge(001) and Si(001) could reveal some interesting aspects of the adsorption dynamics of organic molecules on semiconductor surfaces.…”

Surface‐enhanced resonance Raman and hyper‐Raman spectroscopy of water‐soluble substituted stilbene and distyrylbenzene chromophores

“…46,49 -52 In particular, 4-nitrothioanisole on Ag sol has been shown to undergo two sequential surface photoreactions, CH 3 -S bond scission followed by reduction of the nitro group to amino. 49 The resulting 4-aminobenzenethiolate has strong SERS peaks at about 1075, 1140, 1400, 1435, and 1580 cm 1 . Three of these wavenumbers are very close to the new wavenumbers we observe in our DAC spectra.…”