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The adsorption of formic acid (HCOOH) on the Si(100)c(4×2), Si(100)(2×1), Si(100)9° vicinal and Si(111)(7×7) surfaces has been studied by means of high resolution electron energy loss spectroscopy. Formic acid is partially dissociated to form the unidentate formate species (HCOO) and H adatoms on these surfaces at both 90 and 300 K. The formate species is bonded to the Si surface with a covalent bond formed between one of its oxygen atoms and the dangling bond of the surface Si atom. A condensed multilayer of molecular formic acid is formed after the Si surface is saturated with the formate species at 90–150 K. The thermal decomposition mechanism has been studied in detail. The decomposition temperatures of the formate species on Si(100) and Si(111) are ∼600 and 550 K, respectively. It appears that the surface steps do not play an important role in the Si–HCOOH interaction. As the formate‐covered surface is exposed to atomic hydrogen, methylendiolate (H2COO) is formed on the Si surface.

High‐resolution vibrational/electronic‐transition electron energy loss spectroscopy, low‐energy electron diffraction, and Auger electron spectroscopy have been used to study the oxidation of the Si(111) (7×7) surface at 300 K. From the initial stage (O2 exposure ∼1 L, fractional oxygen coverage θ∼0.2), an Si–Si bond breaking occurs, and atomic oxygen is adsorbed in the bridge site (between the first and second layers of Si substrate) as well as in the on‐top site. Some molecular species (superoxide‐like species) are also existent. With the increase in O2 exposure up to 100 L where θ∼1.5 is reached, the number of the Si–O–Si species in the selvedge region of Si substrate is greatly increased. By heating the surface pre‐exposed to 1–100 L O2 at 850 K, the superoxide‐like species are removed and the number of oxygen atoms in the on‐top sites is decreased. With the increase in O2 exposure (0→100 L) and by heating (300→850 K), the bond angle of the Si–O–Si species is increased towards that of the vitreous SiO2...

High‐resolution electron energy loss spectroscopy (EELS) has been applied to the study of the Si(111)(7×7)–H2O(D2O) system. At 300 K, H2O(D2O) is partially dissociated on the Si(111) surface to form the SiOH(SiOD) and SiH(SiD) species. Angle and primary‐electron‐energy dependences of the vibrational loss intensities were measured. Relative contributions to the vibrational excitations of the dipole, impact, and resonance mechanisms were estimated. The O–H(O–D) stretching and Si–O–H (Si–O–D) bending vibrations are partly excited by the resonance mechanism in the primary energy region of Ep ≂2–7 eV. EELS spectra of the Si(111) surface exposed to H2O(D2O) at 300 K and of the same surface heated to ∼700–900 K are presented, and surface reaction mechanisms are discussed.

The adsorbed state of ethylene on Pd(110) at 90 K and its thermal decomposition in the temperature region between 90 and 600 K have been studied by the use of high resolution electron energy loss spectroscopy (EELS), low‐energy electron diffraction (LEED), and thermal desorption spectroscopy (TDS). At 90 K, ethylene is π bonded to the Pd(110) surface and is adsorbed almost disorderedly. The c(2×2)‐C2H4 patches are formed near the saturation coverage (which corresponds to 0.58 C2H4 molecule per surface Pd atom). By heating the C2H4‐saturated Pd(110) surface to 260 K, some C2H4 admolecules are desorbed intact and the remaining admolecules rearrange their adsorbed sites to form the c(2×2)‐C2H4 structure. At above 300 K, almost all the C2H4 admolecules are dehydrogenated, and the ethynyl (CCH) species, H adatoms and unstable dehydrogenated species [possibly, vinyl (CHCH2) species] are formed; the C2H4 desorption occurs by the recombination of H adatoms and dehydrogenated species. The remaining H adatoms are d...

The adsorbed states of ethylene on the Si(100)c(4×2), Si(100)(2×1), and the Si(100) 9° vicinal surfaces have been studied using high resolution electron energy loss spectroscopy (EELS) and low‐energy electron diffraction (LEED). Ethylene is nondissociatively chemisorbed on the Si(100) surface in the wide temperature range between 77 and ∼600 K, and is rehybridized to have a near sp3 hybridization state. The adsorbed structure is proposed in which ethylene is di‐σ bonded to two adjacent Si atoms of the dimer at the Si(100) surface. The thermal decomposition of chemisorbed ethylene and the influence of steps on the adsorbed states of ethylene are discussed.

High resolution electron energy loss spectroscopy (vibrational and electronic excitations) and monochromatic low‐energy electron diffraction (LEED) have been applied to the study of atomic‐hydrogen adsorption on the Si(111) (7×7) surface at ∼300 K. Adsorbed states of hydrogen are differentiated by taking the vibrational loss spectra of the Si(111) surface exposed to various amounts of hydrogen and of the same surface subsequently heated to high temperatures. The existence of four adsorbed states is proposed. Hydrogen adsorption is considered to proceed as follows. In the very early stage (fractional hydrogen coverage θ≲0.3), the SiH species are produced by the covalent bond formation of hydrogen atoms with the dangling bonds of the Si(111) surface atoms. Then, the Si–Si bond breaking and the desorption of SiH4 and, possibly, SiH3 occur, and the corrosion‐induced SiH (with the bond axes parallel to and away from the surface‐normal direction), SiH2, and SiH3 species are also produced. The hydrogen coverage is saturated at θ∼1.5, where the amount of the SiH2 and SiH3 species formed is estimated to be