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Infrared-visible sum frequency generation study of HCOOH on an MgO(001) surface
A254 Surface Science 283 (1993)457-461 North-Holland
Very high resolution photoelectron spectra of NEA-GaAs Y. Naoi a, K. Ito ~, Y. Uehara a, S. Ushioda ~ and Y. Murata b a Research Institute of Electrical Communication, Tohoku University, Sendai 980, Japan b Institute for Solid State Physics, The University of Tokyo, Roppongi, Minato-ku, Tokyo 106, Japan Received 21 April 1992; accepted for publication 31 August 1992 The energy distribution of photoelectrons emitted from N E A - G a A s has been measured with a very high energy resolution ( A E = 5 meV). The sample consists of epitaxially grown p-type GaAs (hole concentration 1 × 1019 cm 3) with a (100) surface. After cleaning the surface by heating in U H V (7 × t 0 - J l Torr), Cs and 0 2 were coadsorbed to obtain a N E A surface. A pulsed GaAIAs laser (a = 820 nm, pulse width = 60 ps) was used for the light source, and the photoelectron energy distribution was measured by a high resolution time-of-flight electron spectrometer. A series of peaks with an approximately regular energy interval of 50 meV was observed in the spectra. Theoretical considerations reveal that the origin of the regular structure are the two-dimensional subbands of electrons at the X-point in the band-bending region near the surface.
Surface Science 283 (1993)462-467 North-Holland
Theory of adsorbate-sensitive positronium formation and its application to ion desorption A. Ishii a and Y. Murata b " Department of Physics, Faculty of General Education, Tottori University, Koyama, Tottori 680, Japan h Institute for Solid State Physics, University of Tokyo, Roppongi, Minato-ku, Tokyo 106, Japan Received 20 April 1992; accepted for publication 10 August 1992 The sensitivity of the positronium formation probability to the position of the adsorbate atom on a surface is studied theoretically. A demonstrative calculation is performed for a hydrogen atom on a Si(100)2 x 1 surface. We found that the dependence of the probability on the incident positron energy is very sensitive to the position of the adatom adsorbed randomly on the surface. Application of this to determine the atomic position of the adsorbate is possible if ion desorption occurs by positronium formation.
Surface Science 283 (1993) 468-472 North-Holland
Infrared-visible sum frequency generation study of HCOOH on an MgO(001) surface Kazunari D o m e n *, Naotoshi Akamatsu, Hiroyoshi Yamamoto, Akihide Wada
and Chiaki Hirose Research Laboratory of Resources Utilization, Tokyo Institute of Technology, 4259 Nagatsuta, Midori-ku, Yokohama 227, Japan Received 21 April 1992; accepted for publication 30 July 1992
A255 Adsorption and decomposition of HCOOH on an MgO(001) single crystal surface were studied by means of infrared-visible sum frequency generation (SFG) spectroscopy and temperature programmed desorption (TPD) in UHV. In the SFG experiment, tunable ultrashort infrared pulses were produced by parametric oscillation/amplification in two pieces of LiNbO 3 single crystals and the tunable range was 2600-4000 cm - t . HCOOH was adsorbed on MgO(001) as formate (HCOO) species at room temperature. The TPD study revealed that HCOOH mainly decomposed into CO and H 2 0 at ~ 510 K. By SFG, the C - H stretching band was observed at 2870 c m - 1 with a shoulder at ~ 2850 cm- 1. The in situ measurement of the change of the SFG signal intensity (2870 cm-1) was carried out during the dosage of HCOOH.
Surface Science 283 (1993) 473-478 North-Holland
Dynamics of friction: superlubric state Kazumasa Shinjo A TR Optical and Radio Communications Research Laboratories, Seika-cho, Soraku-gun, Kyoto 619-02, Japan
and Motohisa Hirano Interdisciplinary Research Laboratories, Nippon Telegraph and Telephone Corporation, Musashino, Tokyo 180, Japan Received 22 April 1992; accepted for publication 30 July 1992 Dynamics in friction is studied from an atomistic point of view. Friction is formulated as a problem of whether or not a given kinetic energy for the translational motion dissipates into the kinetic energies for the internal motions during sliding. From the study of the Frenkel-Kontorova model with kinetic energy terms, it is found that two different regimes appear in the parameter space specifying the model: the superlubricity and the friction regimes. The friction exactly vanishes in the superlubric regime and appears in the friction regime. The conditions for the superlubricity to occur are described. It is emphasized that a high dimensionality in the friction system is a key to understanding the physics of superlubricity. For high dimensional systems, superlubricity is a generic phenomenon, appearing for a wide class of (strong or weak) adhesion such as the metallic bonding and the van der Waals interaction. The results are discussed in comparison with those obtained by assuming the case where the upper surface slides quasi-statically against the lower surface.
Very high resolution photoelectron spectra of NEA-GaAs Y. Naoi a, K. Ito ~, Y. Uehara a, S. Ushioda ~ and Y. Murata b a Research Institute of Electrical Communication, Tohoku University, Sendai 980, Japan b Institute for Solid State Physics, The University of Tokyo, Roppongi, Minato-ku, Tokyo 106, Japan Received 21 April 1992; accepted for publication 31 August 1992 The energy distribution of photoelectrons emitted from N E A - G a A s has been measured with a very high energy resolution ( A E = 5 meV). The sample consists of epitaxially grown p-type GaAs (hole concentration 1 × 1019 cm 3) with a (100) surface. After cleaning the surface by heating in U H V (7 × t 0 - J l Torr), Cs and 0 2 were coadsorbed to obtain a N E A surface. A pulsed GaAIAs laser (a = 820 nm, pulse width = 60 ps) was used for the light source, and the photoelectron energy distribution was measured by a high resolution time-of-flight electron spectrometer. A series of peaks with an approximately regular energy interval of 50 meV was observed in the spectra. Theoretical considerations reveal that the origin of the regular structure are the two-dimensional subbands of electrons at the X-point in the band-bending region near the surface.
Surface Science 283 (1993)462-467 North-Holland
Theory of adsorbate-sensitive positronium formation and its application to ion desorption A. Ishii a and Y. Murata b " Department of Physics, Faculty of General Education, Tottori University, Koyama, Tottori 680, Japan h Institute for Solid State Physics, University of Tokyo, Roppongi, Minato-ku, Tokyo 106, Japan Received 20 April 1992; accepted for publication 10 August 1992 The sensitivity of the positronium formation probability to the position of the adsorbate atom on a surface is studied theoretically. A demonstrative calculation is performed for a hydrogen atom on a Si(100)2 x 1 surface. We found that the dependence of the probability on the incident positron energy is very sensitive to the position of the adatom adsorbed randomly on the surface. Application of this to determine the atomic position of the adsorbate is possible if ion desorption occurs by positronium formation.
Surface Science 283 (1993) 468-472 North-Holland
Infrared-visible sum frequency generation study of HCOOH on an MgO(001) surface Kazunari D o m e n *, Naotoshi Akamatsu, Hiroyoshi Yamamoto, Akihide Wada
and Chiaki Hirose Research Laboratory of Resources Utilization, Tokyo Institute of Technology, 4259 Nagatsuta, Midori-ku, Yokohama 227, Japan Received 21 April 1992; accepted for publication 30 July 1992
A255 Adsorption and decomposition of HCOOH on an MgO(001) single crystal surface were studied by means of infrared-visible sum frequency generation (SFG) spectroscopy and temperature programmed desorption (TPD) in UHV. In the SFG experiment, tunable ultrashort infrared pulses were produced by parametric oscillation/amplification in two pieces of LiNbO 3 single crystals and the tunable range was 2600-4000 cm - t . HCOOH was adsorbed on MgO(001) as formate (HCOO) species at room temperature. The TPD study revealed that HCOOH mainly decomposed into CO and H 2 0 at ~ 510 K. By SFG, the C - H stretching band was observed at 2870 c m - 1 with a shoulder at ~ 2850 cm- 1. The in situ measurement of the change of the SFG signal intensity (2870 cm-1) was carried out during the dosage of HCOOH.
Surface Science 283 (1993) 473-478 North-Holland
Dynamics of friction: superlubric state Kazumasa Shinjo A TR Optical and Radio Communications Research Laboratories, Seika-cho, Soraku-gun, Kyoto 619-02, Japan
and Motohisa Hirano Interdisciplinary Research Laboratories, Nippon Telegraph and Telephone Corporation, Musashino, Tokyo 180, Japan Received 22 April 1992; accepted for publication 30 July 1992 Dynamics in friction is studied from an atomistic point of view. Friction is formulated as a problem of whether or not a given kinetic energy for the translational motion dissipates into the kinetic energies for the internal motions during sliding. From the study of the Frenkel-Kontorova model with kinetic energy terms, it is found that two different regimes appear in the parameter space specifying the model: the superlubricity and the friction regimes. The friction exactly vanishes in the superlubric regime and appears in the friction regime. The conditions for the superlubricity to occur are described. It is emphasized that a high dimensionality in the friction system is a key to understanding the physics of superlubricity. For high dimensional systems, superlubricity is a generic phenomenon, appearing for a wide class of (strong or weak) adhesion such as the metallic bonding and the van der Waals interaction. The results are discussed in comparison with those obtained by assuming the case where the upper surface slides quasi-statically against the lower surface.