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  • 1
    Electronic Resource
    Electronic Resource
    Absolute concentration and loss kinetics of hydrogen atom in methane and hydrogen plasmas (2001)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 90 (2001), S. 5497-5503 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A measurement technique of the absolute concentration of hydrogen (H) atoms in methane (CH4) and/or hydrogen molecule (H2) plasmas has been established. The H-atom concentration was evaluated by vacuum ultraviolet absorption spectroscopy (VUVAS) using a high-pressure H2 microdischarge hollow cathode lamp (H2-MHCL) as the Lyman α (Lα 121.6 nm) light emission source. A measurement technique of the background absorption caused by species other than H atoms at the Lα line was developed by using the VUVAS technique with the MHCL employing nitrogen molecules (N2-MHCL). The lines around Lα used for the background absorption measurements are 2p23s 4P5/2–2p3 4S3/20 at 119.955 nm, 2p23s 4P3/2–2p3 4S3/20 at 120.022 nm, and 2p23s 4P1/2–2p3 4S3/20 at 120.071 nm of the N atom. By using the VUVAS technique with the MHCLs and subtracting the background absorption from the absorption of H atoms at Lα, we have achieved the measurement of the H-atom concentration in an inductively coupled plasma operated in CH4 and/or H2. The H-atom concentration increased from 2×1011 to 3×1012 cm−3 when increasing the CH4 flow rate ratios from 0% to 50% in the CH4–H2 mixture and was almost constant in its range between 50% and 100% at a pressure of 1.33 Pa, a radio frequency power of 200 W, and a total flow rate of 100 sccm. The behavior of the H-atom concentration was compared with that of the Balmer α emission intensity. The decay of the H-atom concentration in the H2 plasma afterglow was investigated to clarify the loss kinetics of H atoms. The dependence of the decay time constant on the pressure showed that H atoms were dominantly lost through diffusion to the wall surface. The diffusion constant of H atoms in H2 plasmas was determined to be 3.0×105 cm2 Pa s−1 at 400 K. The surface loss probability of H atoms on the stainless-steel and the hydrocarbon walls were estimated to be 0.15 and 0.07, respectively. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1410327
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  • 2
    Electronic Resource
    Electronic Resource
    Behavior of hydrogen atoms in ultrahigh-frequency silane plasma (2001)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 89 (2001), S. 4727-4731 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We have investigated the behavior of the absolute density of hydrogen (H) atoms in ultrahigh-frequency (UHF), (500 MHz) silane (SiH4) plasma by using a vacuum ultraviolet absorption spectroscopy technique with a microdischarge hollow cathode lamp. In the UHF plasma using SiH4 highly diluted with hydrogen molecule (H2) at a pressure of 20 Pa, an UHF power of 1000 W, and a total flow rate of 200 sccm, the absolute density of H atoms slightly increased from 7.4×1011 to 7.9×1011 cm−3 with increasing the SiH4 flow rate ratios from 0% to 2.5% and then the H atom density decreased at the ratio of 5%. The decrease of the density is due to the increase of the reaction between the H atom and the SiH4 molecule. The behavior of the absolute density of H atoms was compared with that of the Balmer α(Hα) emission intensity. It was found that the behaviors of the absolute H atom density and the Hα emission intensity were quite different. Moreover, the kinetics of H atom density in SiH4 plasmas have been clarified on the basis of measured results. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1362414
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  • 3
    Electronic Resource
    Electronic Resource
    Dual-electrode biasing for controlling ion-to-adatom flux ratio during ion-assisted deposition of diamond (2001)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 89 (2001), S. 4714-4718 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A dual-bias method using a grid mesh inserted into the front of a substrate has been employed to control the ion-to-adatom flux ratio in an inductively coupled plasma for depositing crystalline materials preferring low-energy ion bombardment. The Langmuir probe measurements revealed that the ion flux toward the substrate decreased with increasing a positive substrate bias with the grid grounded, while it increased with increasing a positive grid bias with the substrate grounded. Ion energy analyses along the diffusing plasma stream by using a probe and a mass spectrometer revealed the contribution of a high-energy tail in the ion-energy distribution into the bombarding ion flux. The ion-assisted deposition of diamond at a pressure of 10 mTorr was performed at a bombarding ion energy as low as the drifting energy (∼several eV). The results indicate the need for optimizing the ion-to-adatom flux ratio for efficient migration and clustering of precursor adatoms yielding a high nucleation density over 109 cm−2. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1359159
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  • 4
    Electronic Resource
    Electronic Resource
    Ultrathin fluorinated silicon nitride gate dielectric films formed by remote plasma enhanced chemical vapor deposition employing NH3 and SiF4 (2001)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 90 (2001), S. 1955-1961 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Ultrathin fluorinated silicon nitride (SiNx) films of 4 nm in thickness were formed on a Si substrate at 350 °C in the downflow of electron cyclotron resonance plasma-enhanced chemical vapor deposition employing ammonia and tetrafluorosilane (NH3/SiF4) gases. Ultrathin fluorinated SiNx film was evaluated for use as a gate dielectric film. The observed properties indicated an extremely low leakage current, one order of magnitude lower than thermal SiO2 of identical equivalent oxide thickness, as well as an excellent hysteresis loop (20 mV) and interface trap density (Dit=4×1011 cm−2) in the capacitance–voltage characteristics. The film structures and the surface reactions for the fluorinated SiNx film formation were examined via in situ x-ray photoelectron spectroscopy. in situ Fourier-transform infrared reflection absorption spectroscopy, in situ atomic force microscopy, and thermal desorption mass spectroscopy. The control of the fluorine concentration in the SiNx films was found to be a key factor in the formation of fluorinated SiNx films of high quality at low temperatures. Fluorinated SiNx is the effective material for application in ultrathin gate dielectric film in ultralarge-scale integrated circuits. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1381556
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  • 5
    Electronic Resource
    Electronic Resource
    Spatial distribution of the absolute densities of CFx radicals in fluorocarbon plasmas determined from single-path infrared laser absorption and laser-induced fluorescence (2001)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 90 (2001), S. 580-586 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The spatial distribution of the absolute density of CFx (x=1–3) radicals and their translational temperatures in an electron cyclotron resonance (ECR) plasma generated from a tetrafluorocarbon (C4F8) gas were examined using infrared diode-laser absorption spectroscopy (IRLAS) without a multiple reflection cell, namely, single-path IRLAS. Furthermore, we have developed a method of measuring CF and CF2 radical densities using single-path IRLAS combined with laser-induced fluorescence (LIF) spectroscopy. This method enables us to measure the spatial distribution of absolute radical densities with high accuracy, because of the IRLAS infrared laser beam and the LIF ultraviolet laser beam having identical paths. Under all the conditions studied, a spatially hollow distribution of the CF2 radical density is formed; the CF2 radical density in the vicinity of the chamber wall is much higher than that in the plasma. However, the spatial distribution of the CF radical density differs greatly from that of the CF2 radical density. The translational temperatures of CF and CF2 radicals are evaluated to be ∼700 K. On the basis of the measured results, we clarify the mechanisms of the formation of the spatial distribution, and conclude that the hollow distribution of the CF2 radical density is not caused by radical generation from the chamber wall, rather, the dominant mechanism for the formation of this distribution is the electron-impact dissociation of C4F8 gas in the ECR region and diffusion from the upper part of the plasma chamber under the present plasma conditions where the flux of ions incident to the chamber wall is low. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1337090
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  • 6
    Electronic Resource
    Electronic Resource
    Effect of ions and radicals on formation of silicon nitride gate dielectric films using plasma chemical vapor deposition (2001)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 89 (2001), S. 5083-5087 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We have clarified effects of ions and radicals on the film property of ultrathin silicon nitride (SiNx) films of 5 nm in thickness formed on Si substrates at 300 °C in electron cyclotron resonance plasma-enhanced chemical vapor deposition (PECVD) employing ammonia and silane (NH3/SiH4), and nitrogen and silane (N2/SiH4) gases. In situ Fourier transform infrared reflection absorption spectroscopy and in situ x-ray photoelectron spectroscopy confirmed that in N2/SiH4 plasma, Si-N bonds in the film were increased by eliminating charged species, and thus, radicals promoted the formation of the SiNx film of high Si-N bond density. On the other hand, Si-N bonds in the film were decreased by eliminating charged species, and eventually, ions played an important role in forming the film of high Si-N bond density in NH3/SiH4 plasma. The excellent hysteresis of 0.04 V was successfully achieved with the NH3/SiH4 plasma. Furthermore, the quadrupole mass spectroscopy suggests that NH4+ charged species make a significant contribution to the formation of ultrathin SiNx films with high quality. These results provide insights into important species to be controlled in the PECVD for low temperature formation of the SiNx gate dielectric films in ultralarge scale integrated circuits. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1337939
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  • 7
    Electronic Resource
    Electronic Resource
    Comparison of attitudes towards school lunch by elementary school children in Japan, Korea and Thailand (2001)
    Oxford, UK : Blackwell Science Ltd
    International journal of consumer studies 25 (2001), S. 0 
    Details
    ISSN: 1470-6431
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Economics
    Notes: The attitudes of elementary school children towards school lunch among three Asian countries, namely Japan, Korea and Thailand, were compared. More school children in Japan felt that their teachers gave them advice during the school lunch programme. Japanese and Korean teachers advised their children to eat as much as possible of the lunch. Korean children may be a little more obedient with regard to heeding the advice. However, few teachers in Thailand gave the children advice over eating lunch, and the Thai children looked forward to and enjoyed the school lunch. The different responses between Thailand and other two countries may be attributed in part to the differences in the teachers' instruction in the programme. Elementary school teachers, especially in Thailand and Korea, have to take more classes in food and nutrition in universities or colleges, and positively take part in the school lunch programme.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1470-6431.2001.00139.x
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  • 8
    Electronic Resource
    Electronic Resource
    Temperature dependence of electroluminescence intensity of green and blue InGaN single-quantum-well light-emitting diodes (2001)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 79 (2001), S. 3723-3725 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Temperature dependence of electroluminescence (EL) spectral intensity of the super-bright green and blue InGaN single-quantum-well (SQW) light-emitting diodes has been studied over a wide temperature range (T=15–300 K) under a weak injection current of 0.1 mA. It is found that when T is slightly decreased to 140 K, the EL intensity efficiently increases, as usually seen due to the improved quantum efficiency. However, with further decrease of T down to 15 K, it drastically decreases due to reduced carrier capture by SQW and trapping by nonradiative recombination centers. This unusual temperature-dependent evolution of the EL intensity shows a striking difference between green and blue SQW diodes owing to the different potential depths of the InGaN well. The importance of efficient carrier capture processes by localized tail states within the SQW is thus pointed out for enhancement of radiative recombination of injected carriers in the presence of the high-density dislocations. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1421416
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  • 9
    Electronic Resource
    Electronic Resource
    Field emission from GaN surfaces roughened by hydrogen plasma treatment (2001)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 78 (2001), S. 3229-3231 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: GaN layers are grown on sapphire substrates with AlN buffer layers by the metalorganic chemical vapor deposition method. GaN layers are doped with Si. The electron density of the n-type GaN is 2×1017 cm−3. It is found that the GaN surface is etched with hydrogen (H2) plasma produced by supplying microwave power leading to the formation of the roughened surface of GaN. A variation in the surface morphology occurs due to microwave power and gas pressure. Field emission measurements are carried out for GaN with various surface morphologies. It is observed that the turn-on electric field decreases with increasing surface roughness of the GaN. A turn-on electric field of the electron emission is estimated to be as low as 12.4 V/μm. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1370979
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  • 10
    Electronic Resource
    Electronic Resource
    Field emission characteristics of BN/GaN structure (2001)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 79 (2001), S. 4533-4535 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: n-type gallium nitride (GaN) layers grown on sapphire substrates by metalorganic chemical vapor deposition are used to examine field emission characteristics. The electron concentration of the GaN is 2×1017 cm−3. In order to enhance the electric field, the GaN surface is roughened by hydrogen (H2) plasma treatment. Boron nitride (BN) films are grown on the roughened surface of the GaN by plasma-assisted chemical vapor deposition. The turn-on electric field between the anode and sample surface is estimated to be 12.4 and 8.8 V/μm from the field emission characteristics of the roughened GaN and the BN/GaN samples, respectively. It is demonstrated that BN coating is effective in improving the field emission characteristics.© 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1427755
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