T. Yano

Irradiation effect of low energy nitrogen-ion beam during pulsed laser deposition process on the structural and bonding properties of carbon–nitride thin films

Carbon–nitride thin films were deposited by pulsed laser ablation of graphite with assistance of low energy nitrogen-ion-beam irradiation. The nitrogen to carbon (N/C) atomic ratio, bonding state, microstructure, surface morphology, and electrical property of the deposited carbon–nitride films were characterized by x-ray photoelectron spectroscopy, Fourier transform infrared spectroscopy, micro-Raman spectroscopy, x-ray diffraction (XRD), atomic force microscopy, and four-probe resistance. The irradiation effect of low energy nitrogen-ion beam on the synthesis of carbon–nitride films was investigated. The N/C atomic ratio of the carbon–nitride films reached the maximum at the ion energy of ∼200 eV. The energy of ∼200 eV was proposed to promote the desired sp3-hybridized carbon and the C3N4 phase. Electrical resistivity of the deposited films was also influenced by the low energy nitrogen-ion-beam irradiation. However, the low energy irradiation had little effect on the surface morphology of the films. XRD...

Growth of nano-crystalline diamond by pulsed laser deposition in oxygen atmosphere

Abstract Growth of nano-crystalline diamond by pulsed laser deposition (PLD) in an oxygen atmosphere on a sapphire (0xa00xa00xa01) substrate is reported. The experiments were performed at a substrate temperature of ∼550°C and in an oxygen pressure of 0.11–0.15xa0Torr. Field-emission scanning electron microscope, X-ray diffraction and micro-Raman spectroscopy were used to characterize the products. Results indicated that hexagonal and cubic diamond crystals with an average size of ∼30xa0nm were formed. The crystal nucleation and growth were non-uniform and discontinuous. The possible diamond growth mechanism by PLD in an oxygen environment is discussed. Compared with diamond growth in a chemical-vapor-deposition process, the conditions for diamond nucleation and growth by PLD in an oxygen atmosphere are quite critical.

Diagnostics of KrF- and Nd:YAG-Laser Produced Carbon Plumes by Time- and Spatially-Resolved Spectroscopy

Graphite was ablated by three lasers and the resultant carbon plumes were investigated by time- and spatially-resolved spectroscopy. A KrF excimer laser (248 nm) and an Nd:YAG laser (1064 and 266 nm) were used. Near the target surface, C2 (Swan band) and ionic emissions from the plume produced by the 1064-nm laser at a fluence of 6 J/cm2 were stronger than those produced by the 248-nm and 266-nm lasers. The C emission lines (247.9 and 193.1 nm) produced by the KrF excimer laser were stronger than those produced by the other lasers. The most probable velocity of C+ was highly dependent upon the laser wavelength. The dependence of the most probable velocity on the fluence was small. The velocity of C+ ablated by the 248-nm laser was twice as fast as that ablated by the 1064-nm laser, when the fluence of the 1064-nm laser was six times as large as that of the 248-nm laser.

FATIGUE PROPERTIES OF TiN FILMS ON STEEL COATED BY DYNAMIC MIXING

ABSTRACT The eight kinds of TiN thin films were coated on steel by using dynamic mixing method. The structure of the coated thin films were analyzed by using X ray. It has been found that the thin films were TiN structure alone and the mixed structures of TiN and Ti2N. The fatigue life of thin film depends on an applied cyclic stress. When the cyclic stress is high level, the thin film scarcely improves the fatigue life. At low cyclic stress, the thin film markedly increases the fatigue life. Then, the fatigue life of thin film increases with increasing the hardness of thin film. The enlargement of fatigue life of thin film relates with the process of crack initiation from the coated TiN thin films.

Optical emission of plasmas in ultraviolet and infrared laser ablation of graphite by time-resolved spectroscopy

The optical emission spectra of the plasma produced by infrared and ultraviolet laser ablation of graphite in a vacuum were observed. The fundamental output of an Nd: YAG laser was used as the infrared laser. The fourth harmonic output of an Nd: YAG laser and a KrF excimer laser were used as the ultraviolet lasers. The emission intensity of the ionic carbon as well as C2 and C3 from the plasma produced by the infrared laser were stronger than that produced by the UV lasers at the same fluences. The C2 and C3 emission intensities decreased rapidly with increasing the distance from the target. The emission intensity of atomic carbon at 247.8 nm from the plasma produced by the KrF excimer laser was much stronger than that produced by the other lasers at the same laser fluence, due to the wavelenght of the KrF laser being so close to that of atomic carbons emission line as to raise its electrical state.

Influence of laser fluence on the synthesis of carbon nitride thin films by nitrogen-ion-assisted pulsed laser deposition

Carbon nitride films were deposited by pulsed Nd:YAG laser ablation of graphite with assistance of nitrogen ion beam bombardment. The nitrogen to carbon (N/C) atomic ratio, surface morphology and bonding state of the deposited carbon nitride films were characterized by X-ray photoelectron spectroscopy (XPS), Fourier transform infrared (FTIR) spectroscopy and atomic force microscopy (AFM). The influence of laser fluence on the synthesis of carbon nitride films was investigated. The N/C atomic ratio of the carbon nitride films can reach the maximum at the highest laser fluence. XPS and FTIR analyses indicated that the bonding state between the carbon and nitrogen in the deposited films was influenced by the laser fluence during deposition. The carbon-nitrogen bonding of C-N, C=N together with very few CequalsVN were found in the films. Results indicated that the laser fluence also had critical effect on the surface morphologies of the carbon nitride films.

Electrical and optical properties of ITO films deposited by excimer-laser-assisted EB method

In-situ excimer laser irradiation on growing films is expected to progress the surface reaction i.e. oxidation and surface migration of adatoms. This method therefore will be adequate for the low temperature formation of oxide semiconductor films showing a wide band energy gap. We studied the effect of in-situ excimer laser irradiation on the electron beam deposited Indium-Tin-Oxide (ITO) films and evaluated the electrical and optical properties. The ITO films deposited without laser irradiation at room temperature were opaque and had an amorphous structure, and its resistivity was higher than 0.04 (Omega) cm. On the other hand, the ITO films deposited with in-situ laser irradiation at room temperature showed good transparency and electric properties. The low resistivity, smaller than 9 X 10-4 (Omega) cm, and high transparency, more than 90 percent, were achieved simultaneously at room temperature. The films crystallized with in-situ laser irradiation had a cubic crystalline structure. The Hall mobility and carrier density of the ITO film were 12 cm2/Vs and 5.5 X 1022 cm-3, respectively. These result suggested that the in-situ excimer laser irradiation progressed the surface oxidation and eliminated the unstable adatoms on the surface of growing ITO films.

Effect of Laminated Layer on Fatigue Properties of Steel Modified by Dynamic Mixing Process

The aim of this work was to investigate the effect of lamination of TiN and Ti2N on the fatigue behavior. As the results, the fatigue life of mild steel in a low stress level was improved by laminating the films used dynamic mixing method. The fatigue crack nucleation was considerably delayed by the lamination at the interface between the films and the substrate.