Kazuhiro Kanda

In order to study the influences of residual Ar monomer ion (Ar+) on sp(2) content and hardness of diamond like carbon (DLC) films formed by Ar cluster ion beam assisted deposition, Ar cluster ion, Ar+ and their mixed ions (Ar cluster ion and Ar+) bombardments were performed during evaporation of C-60. From near edge X-ray absorption fine structure (NEXAFS) and Raman spectroscopy measurements, lower sp(2) content in the carbon films was obtained with Ar cluster ion bombardment than that with Ar+ and mixed ion. Furthermore higher hardness and smooth surface were shown with Ar cluster ion bombardments. Therefore it was important to reduce Ar+ in Ar cluster ion beams to obtain hard DLC films with flat surface. (C) 2003 Elsevier Science B.V. All rights reserved.

In the direct etching of spin-on-lass (SOG) films exposed using synchrotron radiation (SR) in the soft X-ray region at room temperature, etching depth increased with the SR dose. The etching rate of SOG films with organic content was much higher than that of SOG films without organic content. X-ray photoelectron spectroscopy (XPS) observation showed that the etching mechanism of SOG films without organic content was mainly SiO desorption and that of SOG film,, with organic content was mainly SiO and oxygen desorption. A 2 mum line and space etching pattern was transferred to SOG film with good fidelity by SR exposure.

The coordination of carbon atoms in diamond-like carbon (DLC) thin films formed by Ar gas cluster ion beam (GCIB) assisted deposition using fullerene as the carbon source was investigated by measuring near-edge X-ray absorption fine structure (NEXAFS) spectra of the carbon K-edge over the excitation energy range 275-320 eV, using synchrotron radiation. With attention to the peak corresponding to the transition of the excitation electron from a carbon Is orbital to a pi* orbital, relative sp(2) contents of various DLC films were estimated. The sp(2) contents of the DLC films formed by the GCIB-assisted deposition were observed to be lower than those of the DLC films formed by other methods. The hardness value measured with a nano-indentation technique was found to be strongly related to the sp(2) content of the DLC film.

The dissociative excitation of BrCN producing CN(B2Σ+) fragment by the collision of He*(23S) was investigated by the collision energy-resolved electron and emission spectroscopy using time-of-flight method with a high-intensity He* beam. The Penning electrons ejected from BrCN and the subsequent CN(B2Σ+-X2Σ+) emission were measured as a function of collision energy in the range of 90-180 meV. The formation of CN(B2Σ+) is concluded to proceed dominantly via the promotion of an electron from Π-character orbital, by comparison between the collision energy dependence of the partial Penning ionization cross-sections and the CN(B2Σ+-X2Σ+) emission cross-section. © 2001 Elsevier Science B.V.

The quantitative photofragment fluorescence spectroscopy, using the synchrotron radiation as an exciting light source, was applied to study the Rydberg and high-lying valence states of ClCN observed as congested structures in the vacuum ultraviolet region. The absolute cross-section and quantum yield for the CN(B (2)Sigma(+)-X(2)Sigma(+)) emission produced in the photodissociation process of ClCN were determined in the wavelength range 105-145 nm (69 000-95 200 cm(-1)). The quantum yield for the CN(B(2)Sigma(+)) production takes a maximum value of approximate to 0.13 at approximate to 84 000 cm(-1). The emission of CN(B (2)Sigma(+)-X(2)Sigma(+)) transition was found to be partially polarized with respect to the direction of the electric vector of the excitation synchrotron radiation. The polarization anisotropy of this emission, which depends on the symmetry of absorption transitions into the photodissociative states of ClCN was measured as a function of exciting wavelength. The relative cross-section for the production of CN(A (2)Pi(i)-X(2)Sigma(+)) emission was also determined. Based on the measured photochemical properties of the high-energy electronic states, the observed bands of the Rydberg and intravalence transitions are assigned. (C) 2000 Elsevier Science B.V. All rights reserved.

The photodissociation process to produce the electronically excited CN fragments from CH3CN, C2H5CN and n-C3H7CN has been studied by using synchrotron radiation. The cross-sections for the photoabsorption and the production of CN(B (2)Sigma(+)-X(2)Sigma(+)) and CN(A (2)Pi(i)-X(2)Sigma(+)) emission were determined over the excitation wavelength range 30-150 nm (67 000-333 000 cm(-1)). The photoabsorption peaks were interpreted in terms of excitations to valence excited states and the Rydberg states. The quantum yield for the production of the excited CN fragment takes a maximum just below the excitation energy corresponding to the first ionization potential of each nitrile. With the length of the alkyl chain, the quantum yield for the production of CN(B (2)Sigma(+)-X(2)Sigma(+)) emission decreases drastically. Based on these experimental results, the spectral assignments of the photoabsorption bands and the photodissociation mechanism of nitriles were discussed. (C) 1999 Elsevier Science B.V. All rights reserved.

Photodissociation of ICN was investigated by the measurement of the absolute cross section for the production of CN(B-2 Sigma(+)-X-2 Sigma(+)) emission in the wavelength range 107-175 nm (57000-94000 cm(-1)). The observed excitation function of the CN(B-2 Sigma(+)-X-2 Sigma(+)) emission displays congested structures, indicating a number of Rydberg and high-lying valence states correlating to the I + CN(B-2 Sigma(+)) dissociation channel. The relative cross section for the production of CN(A(2) Pi(i)) was also determined, The quantum yield for the CN(B-2 Sigma(+)) production was observed to increase with excitation energy up from approximate to 0.01 at 59000 cm(-1) up to approximate to 0.05 at 87000 cm(-1). The sudden decrease of the yield around 88000 cm(-1) corresponds to the opening of the ionization channel of ICN. The CN(B-2 Sigma(+)-X-2 Sigma(+)) emission was found to be partially polarized with reference to the direction of the electric vector of the excitation radiation. The polarization measurement was used to identify the types of absorption transitions relevant to the photodissociation. On the basis of these measurements, the spectral assignments of the absorption bands below the first ionization potential were reexamined.

Collisional reactions of CH3CN, C2H5CN, and n-C3H7CN with argon metastable atoms, Ar-m, were investigated by observing the CN violet emissions in a flowing afterglow under essentially collision-free conditions. Rovibrational distributions of CN(B-2 Sigma(+)) were determined by a simulation analysis of the main band of the CN(B-2 Sigma(+)-X(2) Sigma(+)) emission spectra. The obtained vibrational distribution was compared with that predicted by the statistical theory. The effective degree of freedom of vibration involved in the available energy disposal was found to increase with the length of the hydrocarbon chain of the target molecule. This increase supports that CN(B-2 Sigma(+)) is produced via energy transfer. The reaction cross sections for the dissociative excitations which produce CN(B-2 Sigma(+)) from CH3CN, C2H5CN, and n-C3H7CN with Ar-m were determined to be 1.0(1), 0.8(1), and 0.6(1) Angstrom(2), respectively, by using the reference reaction method. The decrease in the reaction cross section with respect to the length of the hydrocarbon chain is attributable to the steric hindrance of the molecular orbital from which the excitation leads to the effective production of the CN(B-2 Sigma(+)) by the inert hydrocarbon chain and/or the dissipation of available energy to the hydrocarbon chain.

The CN(B2SIGMA+-X2SIGMA+) emission spectrum produced in the reaction of Ar(3P2) with BrCN was observed by the use of a flowing afterglow method at argon pressures ranging from 9 mTorr to 2 Torr (1 Torr = 133.322 Pa). The pressure dependences of the intensity anomalies in the rotational lines due to the B2SIGMA+ approximately A2PI(i) and the B2SIGMA+ approximately 4SIGMA+ perturbations were measured by introducing collision-partner gases in the reaction region. These pressure dependences can be explained by the ''doorway'' model. On the other hand, the measured pressure dependence of the effective rotational temperature in the CN(B2SIGMA+) state can also be reproduced by the collision-induced rotational relaxation model. The cross section for the rotational relaxation in the A2PI(i) state was found to be smaller than those in the B2SIGMA+ and 4SIGMA+ states. This finding is interpreted by the use of the dipole-induced dipole interaction model for the collision-induced rotational relaxation.

The dynamics of dissociative excitation of BrCN or ICN producing CN(B-2 Sigma(+)) radicals by Ar(P-3(2)) or Kr-(P-3(2)) tvas investigated by using the flowing afterglow method. The observed vibrational distributions of CN(B) are consistent with the reported reaction mechanism for the CN(B) formation initiated by the transfer of the excitation energy of the metastable atom to the cyanide molecule.

The absolute cross sections for the production of CN(A 2PI(i)) and CN(B 2SIGMA+) from BrCN were measured over the excitation wavelength range 105-150 nm (67000-95000 cm-1), using synchrotron radiation. The quantum yields for the CN(A) and CN(B) productions were also determined. The yields were observed to increase with the excitation energy from almost-equal-to 0.02 at 145 nm to almost-equal-to 0.1 at 105 nm. The production of CN(X 2SIGMA+) is possibly the dominant photochemical channel of BrCN in the vacuum ultraviolet (VUV) region. The fragment CN (B 2SIGMA+-X 2SIGMA+) emission was found to be partially polarized with respect to the direction of the electric vector of the incident radiation. The polarization anisotropy of the emission depends on the type of transitions relevant to photodissociation; an examination of the polarization versus excitation energy curve has provided information on the symmetry of the upper electronic states. Based on these experimental results, the assignments of the Rydberg and/or intravalence transitions of BrCN in the VUV region are discussed in connection with the photochemical properties of the high-energy electronic states. The absorption spectrum of BrCN below 105 nm is also reported.

The CN(B2-SIGMA+-X2-SIGMA+) 14-14 emission band was observed in the reaction of Ar(3P0,2) with BrCN by the use of the flowing afterglow method. The intensity anomalies in the rotational lines at N' = 7 due to the B2-SIGMA+(nu = 14) approximately 4-PI(nu = 7) perturbation were measured as a function of the pressure of Ar or He introduced as a collision partner in the reaction region, the ambient pressure being varied from 9 to 2000 mTorr (1 Torr = 133.322 Pa). The intensities of the perturbed lines relative to that of the rotational band envelope increased with the ambient pressure in the low pressure region in the cases of both Ar and He. On the other hand, they decreased with pressure in the higher pressure region. The pressure dependence of the intensity anomaly for He followed that for Ar, although higher pressure of He was necessary to attain the same level of the intensity anomaly for Ar. These pressure dependences can be explained semiquantitatively by a model with collisional rotational relaxations in the quartet and doublet manifolds, the former being dominant at low ambient pressure and the latter at higher pressure.

The vibrational bands of upsilon' = 3-22 of the CN(A PI-1-X 2-SIGMA+) emission produced in the dissociative excitation of BrCN with Ar(3P0.2) were observed in the region 460-750 nm by a flowing-afterglow method under essentially collision-free conditions in order to investigate the formation dynamics of the CN(A 2-PI-i) fragment. The nascent vibrational distribution of the A 2-PI-i species was determined by a simulation analysis of the CN (A 2-PI-i-X 2-SIGMA+) emission. A surprisal analysis of the vibrational distribution shows that the dominant mechanism producing the CN (A 2-PI-i) radical is energy transfer, being in parallel with that of the reaction producing the CN (B 2-SIGMA+) radical.