Y. Igari

XPS study of a SiC film produced on Si(100) by reaction with a C2H2 beam

A Si(100) surface reacted with a well-collimated C2H2 beam was studied by XPS after storing it in air for about one year. The SiC film formation was confirmed by the characteristic XPS peaks of Si2p (101.3 eV) and Cls (283.3 eV) for SiC. The chemical maps on the surface were obtained by imaging XPS. The ≈ 1 mm diameter SiC region was clearly identified on the Si substrate by the method. In the SiC and the non-reacted Si regions the Si2p XPS peak for SiO2 (103.6 eV) and the O 1s peak were also observed. The intensities of the O 1s and Si 2p (SiO2) peaks in the SiC region were smaller by a factor of 0.75 than in the surrounding Si region. This indicates that the carbide (SiC) film was less reactive to O2 than the Si surface. There was very little evidence of any SiOx (x < 2) products which may be transients in the formation of SiO2 or complexes like CSiO.

XPS study of nitridation of diamond and graphite with a nitrogen ion beam

Diamond (CVD) and graphite (HOPG) samples were nitrided at room temperature by irradiation with 300–700 eV N2+ ion beams. X-ray photoelectron spectra (XPS) were recorded in situ during the nitridation. The XPS spectra of C1s and N1s core levels are divided into three (A, B, C) and four (D, E, F, G) components, respectively. The A component at ∼284.8 eV is assigned to the non-damaged substrate below the ion penetration depth. The B component at ∼286.0 eV originates in the damaged phase and the sub-nitride phase (CNx: x<1). The C component at ∼287.3 eV is attributed to genuine nitrides such as C3N4. The broad N1s XPS peak at ∼400 eV splits clearly into the D (∼398.4 eV) and F (∼401.2 eV) components upon annealing at 600°C in vacuum. The splitting is caused by evaporation of the volatile E component (∼399.7 eV). The intensity of the D component was always comparable to that of the F component in both diamond and graphite cases. The origins of these components are discussed. The G component may be due to nitrogen trapped at defects.

SiC film formation on Si(001) by reaction with C2H2 beams

Abstract β-SiC films on Si(001) have been formed by direct reaction of Si crystal with C 2 H 2 molecular beams in ultra-high vacuum. Depth profiles of the C/Si composition ratio of the films have been measured by an Auger electron spectrometer combined with an Ar + ion sputtering gun. The structures and topographies of the films were observed by SEM and TEM. The growth rate of the film has been found to be proportional to the reaction time and the beam flux under low beam flux condition. However, the growth rate decreased at high temperatures. In this case, the surface under reaction was covered with a Si-rich layer and the epitaxial growth of SiC crystals was observed on the substrate. In the substrate pyramidally shaped corrosion along the (111) face was observed by TEM. In the etched parts SiC was also formed by reaction with C-containing reactants. Under high beam flux condition, the surface of the growing film was covered with a C-rich layer and the growth rate decreased. In this case, the grown film consisted of polycrystals and was covered with hillocks.

Observation of c(4 × 4) LEED pattern induced by reaction of Si(100) surface with C2H4

The initial stage of carbide layer formation on a Si(100) surface by reaction with C2H4 gas was studied by low energy electron diffraction (LEED) and Auger electron spectroscopy (AES). A c(4 × 4) LEED pattern was clearly observed after an exposure of C2H4 of 5 × 10−6 Torr for 5 min at a sample temperature of 600°C to the Si(100) surface. Some factors which induce the c(4 × 4) pattern are discussed.

Reaction of Si surfaces with a C2H4 beam

Abstract The reactions of Si(100) and (111) surfaces with a C 2 H 4 beam in ultrahigh vacuum were studied using high resolution X-ray photoelectron spectroscopy (XPS) at temperatures of 600–900°C. These reactions produce silicon carbide (SiC) layers on the silicon surfaces, the growth rates of which increase with surface temperature up to about 675°C, but decrease at higher temperatures. The observed behavior is explained by the balance between the carbon supply rate from the C 2 H 4 beam and the silicon out-diffusion rate from the substrate to the carbide surface. The carbon supply rate is limited by the surface residence time of chemisorbed C 2 H 4 and the beam flux. At the temperature of maximal growth the composition ratio of carbon to silicon in the carbide layer is close to unity, but decreases with increasing temperature. Below the optimal temperature the FWHM of the C 1s XPS peak is broader than that of the stoichiometric compound SiC, implying that the chemical bonding in the carbide layer is distributed. The SiC bulk plasmon-loss peaks accompanying the Si 2s and C 1s XPS peaks appear in carbide films thicker than about 13A.

Nitridation of a Si(100) surface by 100–1000 eV N+2 ion beams

The nitridation mechanism of silicon at room temperature under exposure to 100–1000 eV N+2 ion beams has been studied in situ in an ultrahigh vacuum apparatus using x‐ray photoelectron spectroscopy. The increase of the nitrogen content in a surface layer as a function of the ion dose was described by a simple formula which was derived by assuming random occupation of the reaction sites in the penetration zone of the nitrogen atoms. A change of the binding energy and the width of the N1s x‐ray photoelectron spectrum during the reaction was observed and discussed with the component ratio N/Sireacted. The Si2p x‐ray photoelectron spectra were deconvoluted into five components of Si(0), Si(1), Si(2), Si(3), and Si(4) by curve fitting, where Si(n) represents the component of Si bonded to n nitrogen atoms. Their populations were dependent on the ion dose and the ion energy. The nitride layers formed in the Si surface with low energy beams of 100–200 eV had near‐stoichiometric composition of Si3N4. With beams of...

Nitridation of Si(100) surface with NH3

The nitridation of a Si(100) surface with a NH3 beam at temperatures between 600 and 900°C was studied using X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM). Thicker film was formed at higher temperature. The composition ratio of the film was almost constant during the film growth at all temperature. Island growth of silicon nitride was observed at 900°C using SEM. The N1s XPS spectrum of the Si surface nitrided was deconvoluted into two Gaussian components.

Initial stage of SiC growth on Si(1 0 0) surface

Abstract The growth of SiC film by exposing Si(l 0 0) surface to C2H4 gas at sample temperature of 700°C was examined using reflection high-energy electron diffraction (RHEED), scanning electron microscopy (SEM), and X-ray photoelectron spectroscopy (XPS). From the dependence of the RHEED patterns on C2H4 exposure, a continuous shift of the lattice constant of SiC film during the growth was indicated. The width of the SiC(10) spot was very broad, which suggests that there is a dispersion of length between atoms in SiC islands. The surface morphology at the initial stage of the film growth was also observed by SEM.

XPS study of the reaction of the Si(100) surface with a C2H4 beam

Abstract The carbide layers produced by reaction of a Si(100) surface with a C 2 H 4 beam were analyzed by high resolution X-ray photoelectron spectroscopy (XPS). It was found that the reaction occurs above ∼ 600°C. The growth rate of the carbide layer at a beam flux of 2.7 × 10 15 molecules cm −2 s −1 increased with the surface temperature up to 675°C, and then decreased with increasing the temperature. This phenomenon is explained in terms of the surface residence time of the incident molecules and the diffusion rate of the Si atoms from the substrate to the surface.

Reaction of a Si(100) surface with a hot C2H4 beam

A clean Si(100) surface at 670°C in ultrahigh vacuum was irradiated with a C2H4 molecular beam produced from a nozzle at 900°C. The reaction products on the surface were investigated using X-ray photoelectron spectroscopy, reflection high-energy electron diffraction, and scanning electron microscopy. The central area of the surface irradiated with the beam was covered with a mixture of graphitic film and SiC grains. At the fringe of the central area, however, the SiC grains were the dominant products, which were epitaxially grown on the Si(100) surface. The density of the SiC grains decreased with the distance from the fringe. Compared with the results using the molecular beam produced from the nozzle at room temperature, it is concluded that the dissociation rate of the hot C2H4 molecules is higher than that of the cold molecules, resulting in a carbon film. The growth mechanisms of the graphitic and SiC products are discussed.