新しい昇温脱離ガス分析装置の開発とＶＬＳＩ材料及びプロセス評価への応用

The reaction of atomic hydrogen with the C2H2-covered Si surface was studied using high-resolution electron-energy-loss spectroscopy (HREELS), thermal-desorption mass spectrometry (TDMS), and low-energy electron diffraction. We found that atomic hydrogen broke up the carbon-carbon bond in C2H2 and the Si-Si dimers on the Si surface, which led to the formation of C-H and Si-H bonds, respectively. When the C2H2-covered Si(100) surface was exposed to a filament-activated H-2/CH4 mixture, HREELS showed that the C-H stretching signal grew at the expense of the Si-H stretching signal. This observation was consistent with the replacement of the Si-H bond by - CH3, possibly following hydrogen abstraction from the Si-H bond by atomic hydrogen. TDMS analysis showed significant desorption of atomic hydrogen at both 650 and 750 K and a little desorption of CH2 and CH3 only at 650 K, although HREELS remained unchanged with annealing temperature. This showed that part of the hydrocarbon species on the Si surface existed as a stable network of hydrocarbon, which possibly was the initial stage of diamond formation on Si.

ABSTRACTIsotopically-labeled oxygen enrichment and thermal desorption mass spectroscopy (TDMS) have been combined to study interstitial oxygen desorption from superconducting La2CuO4+δ(δ≤5 0.032). Single crystal samples of magnetic, insulating La2CuO4+δ were annealed at 860K under 1-3 kbar oxygen pressure for 12-100 hours to yield hole-doped, superconducting La2CuO4+δ samples with 35K <Tc <40K. Whereas no TDMS signals were observed for the insulator, rapid bursts (FWHM <0.5 sec) of molecular oxygen were observed above 350K while heating the superconductor at less than I K sec−1 in high vacuum. A kinetic model is proposed in which the interstitial oxygen diffuses to internal grain boundaries and defects during heating, thereby inducing stress in the lattice as it attempts to revert to the LaCuO4.00 crystal structure. This stress is relieved by lattice fracture at grain boundaries during the TDMS experiment, releasing the trapped oxygen from the sample as micro-cracks are formed. In addition, the facile oxygen exchange between interstitial and latticeoxygen sites has been discovered by TDMS and weight gain measurements from isotopically-enriched crystals, supporting thestructural model of Chaillout, et al. in which the interstitial oxygen atom dimerizes with a lattice oxygen ion.

The interactions of cyclopentane with clean and bismuth-covered Pt(111)

Electron energy loss spectroscopy (EELS) is a versatile and sensitive probe of electronic and vibrational excitations at surfaces. The technique is extensively used as a research and analytical tool in a broad range of surface science applications including research on intrinsic physical and chemical properties of surfaces, chemisorption phenomena, and chemical processes at surfaces. The spectroscopy is based on measuring the energy loss and momentum transfer of electrons in a highly collimated, monochromatic (narrow energy spread) beam after the electrons scatter from a surface. Vibrational excitations of atoms and molecules adsorbed on surfaces, collective excitations of ordered chemisorbed structures, the intrinsic collective excitations of surface atoms (surface phonons), and collective electronic excitations (surface plasmons) can be studied using the technique. Under favorable conditions, vibrational losses from surface adsorbate concentrations below 10−3monolayer (1012atoms cm−2) can be detected. EELS is a surface science probe, typically requiring an ultrahigh vacuum (UHV) environment, and is generally employed in conjunction with complementary surface analytical probes such as Auger electron spectroscopy (AES), low‐energy electron diffraction (LEED) and thermal desorption mass spectroscopy (TDS). EELS is an ideal tool for determining surface chemical composition, and provides vibrational loss spectra similar to infrared reflection absorption spectroscopy (IRAS), Raman spectroscopy, and helium atom scattering spectroscopy (HAS).

Reactive-ion-etching (RIE) induced surface modifications of SiO2 and phosphosilicate glass (PSG) were investigated using thermal desorption mass spectroscopy (TDS) and X-ray photoelectron spectroscopy (XPS), in order to study their reactivity variance in the highly polymerized fluorocarbon plasma. Ar+ induced reactions between the fluorocarbon adsorption layer and the underlying oxide substrates were also examined. At the C,F-film/substrate interface, the adsorption layer was found to be chemisorbed to the substrates. Both SiO2 and PSG were found to react in a very near surface region, chiefly with the adsorption layer, by reflecting the reactivity in SiOxFy reaction layer below the surface. The mechanisms of the reactivity variance were explained by the difference in density of active sites for unsaturated CFX chemisorption induced by ion bombardment, and the variance of Si-O bond breakability of the substrates. These effects are caused by the existence of P-O or P = 0 bonds in PSG. Fluorocarbon chemisorption layers were also observed to be thermally stimulated to react with the substrates in TDS apparatus with to activation energy of approximately 1.9eV. This observation indicates the possibility that chemical sputtering easily occurs in actual RIE through a thermally excited step, induced by ion bombardment.

Kinetics of hydrogen adsorption and desorption on thin platinum films

The coadsorption and reaction of diborane with ammonia and with hydrazine on Ru(0001) have been studied using X-ray photoelectron spectroscopy (XPS) and thermal desorption mass spectroscopy (TDS). Diborane is found to decompose to atomic boron and hydrogen upon adsorption at T>200K. Multilayers of diborane and ammonia, deposited at 90K on Ru(0001), react when annealed to 600K. The XPS results indicate that boron-nitrogen adlayers can be formed by this reaction. These boron-nitrogen films are boron-rich and.decompose at temperatures higher than 1100K. Our TDS studies reveal that hydrazine decomposes extensively to NH3, N2, N and H on Ru(0001). Due to its higher reactivity, boron-nitrogen films of B/N stoichiometric ratio near unity are obtained when hydrazine is used rather than ammonia. In our studies, these films were formed by either simultaneously dosing B2H6 and N2H4 at 450K or by coadsorption of the reactants at 90K and subsequent annealing to 450K. These studies have shown that diborane and hydrazine can be successfully used as molecular precursors in the low temperature deposition of boron nitride thin-films.

Industrialisation and the development of manufacturing process nowadays demand a more efficient and environmental friendly production. Microwave energy can be seen as the alternative heating application to meet the demands due to its ability to heat materials volumetrically. In this study, the usage of microwave energy to join thermoplastic is investigated. One of the key features of thermoplastic is the ability to shape when heated to their glass transition temperature and return to the moulded shape when it is cooled. Engineering thermoplastic Acrylonitrile-butadiene-styrene (ABS) was used as member while charcoal powder was used as susceptor material. The joining process was carried out with timing varying from 3 to 5 minutes, adhesive method and direct heating method. Upon the completion of joining, tensile test, 3 points test, hardness test and charpy impact test were conducted and compared to determine the strength of the joint.

Electron energy loss spectroscopy and thermal desorption mass spectroscopy have been used to correlate vibrational spectra of H2O on Ru(001) with ESDIAD patterns reported recently. We find that the ‘‘extended bilayer’’ is characterized by a sharp fundamental O–H vibration at 3500–3565 cm−1 which is assigned to nonhydrogen-bonded OH bonds of molecularly adsorbed water. Hydrogen bonds within the well-ordered bilayer give rise to features at ∼3290–3450 cm−1 which are of relatively weak intensity in electron scattering due to the orientations of these bonds. In addition, very small clusters exhibit a weak vibrational mode at ∼2935 cm−1 which possibly represents H2O molecules with one O–H bond pointing into the surface. Isolated H2O molecules at low temperature and low coverage exhibit a fundamental O–H vibration at 3600 cm−1. A reinterpretation of the thermal desorption spectra is suggested.

The adsorption of CO, CO2, and H2 O, the coadsorption of oxygen and H2 O, and the coadsorption of CO and surface hydroxyl (OHa) on clean and cesium-covered Cu(110) surfaces have been studied with thermal desorption mass spectroscopy, x-ray photoelectron spectroscopy, Auger electron spectroscopy, and work function measurements. We review here results which show that the presence of preadsorbed cesium dramatically affects the adsorption behavior and surface chemistry of CO, CO2, and H2 O on Cu(110). We also present new results which show that surface formate (HCOOa) is not produced in any observable amount upon heating coadsorbed COa and OHa on clean or Cs-dosed Cu(110). The implication of these results to Cs promotion of the catalytic water–gas shift and methanol synthesis reactions over Cu will be discussed.

The adsorbate formed during ethanol oxidation in acidic solutions is studied by Fourier transform infrared reflection‐absorption spectroscopy (FTIR) at constant potential, on‐line (DEMS) and thermal desorption mass spectroscopy (ECTDMS). – As in the case of methanol adsorbate COad was identified by FTIR and in addition COHad by ECTDMS. On‐line MS experiments showed the formation of methane during the cathodic sweep of the voltammogram. Main products of ethanol oxidation from the bulk are carbon dioxide and acetaldehyde.

Chemical and electronic properties of silver atoms supported on sulfur and molybdenum sulfide surfaces

Thermal desorption of N 2 from (N 2+O 2) coadsorbed on polycrystalline rhenium surfaces

The vapor deposition of Bi on Pt(111) at 110 and ∼600 K have been characterized by Auger electron spectroscopy (AES), thermal desorption mass spectroscopy (TDMS), low-energy electron diffraction (LEED), and changes in the work function (Δφ). At 110 K Bi growth follows a layer-by-layer mechanism. At ∼600 K Bi fills the first monolayer (θBi≂0.56) relatively uniformly, followed by 3D island growth. Bi desorption is characterized by a large, coverage-dependent desorption energy, Edes =(81−34.2 θBi ) kcal mol−1, in the first monolayer, and zero-order kinetics with constant activation energy (Edes =53–56 kcal mol−1) for the multilayer. Many LEED patterns are observed within the first monolayer for both cold and hot substrates. Structural models for these are proposed which are consistent with coverages obtained by AES. Annealed structures show continuous compression of hexagonal Bi overlayers with increasing coverage, subject to mild substrate constraints. At 110 K and θBi >0.33, uniaxial compression is instead seen, due to an unsurmounted energy barrier. Weakly repulsive lateral Bi–Bi interactions (due to dipole repulsions) dominate submonolayer growth. These results for the semimetal Bi are intermediate in behavior between alkali and transition metal overlayers on Pt(111). This is consistent with the relative strengths of the surface dipole of these adsorbed metals.

The chemisorption of N 2 on the (110) surface of iridium