LASER APPLICATIONS

photons. The available laser energies are in the zone-boundary region of the Brillouin zone of the graphite crystal. This gives the birth of a new structure investigating method, where the Raman scattering supplies information about the high momentum regions of the Brillouin zone as well, which was previously investigated by neutron scattering only.

Influence of nitrogen doping on photoluminescence properties of a-C:H layers was demonstrated by studying sample series with different N concentrations. Small N concentration quenches the light emission of a-C:H layers completely. By increasing the N concentration new light emission appears in different energy range. This band depends slightly on N concentration.

Spectral ellipsometry was applied to determine the optical constants of a-C:H layers in the photon energy range of 1.5-4.5 eV. The a-C:H layers were deposited onto silicon wafers by our decomposition method of methane in a radio frequency (rf) glow discharge process. Series of thin films were prepared by varying the negative self bias (US.b.) in the range of -600 V < US.b. < -200 V. The a-C:H samples in this series exhibit transition in electrical and optical properties with decreasing optical gap from 1.3 eV to 0.7 eV as the deposition voltage changes in the range of 200 - 600 V. The complex dielectric function [ε(ω) = ε1(ω) +iε2(ω)] and the complex refractive index [N(ω) = n(ω) + ikω)] were determined for the samples. The most pronounced changes in optical constants and in bonding structure occur near -500 V self bias. The ε2(ω)spectrum exhibits a broad maximum which shifts to lower energies by increasing deposition self bias. The optical properties were explained in terms of electronic band structure related to sp³ and sp² hybridised bonding states of carbon atoms and to intermediate range ordering of sp² bonded sites.

In a co-operation we started to investigate the a-C:H film surfaces with atomic force microscope (AFM). Beside the precisely flat surface of the film we have found some hemi-spherical structures, which seems to resist the intensive ion-implantation process of the film formation, and seems to have a stronger growth tendency, than the film itself. These are preliminary results, which will be continuing, but the strongly increasing interest towards the new carbon formations make it worth to investigate in more details.

Grants

OTKA 20202 Development of fundamental experiments with squeezed light (A. Czitrovszky, 1996-1999)

OTKA T025707 Investigation of nano structures of composit metal-ceramic structures appliing interferometric methods (P. Jani, 1998 – 1999)

OMFB 97-97-47-1593, Integrated optical sensor for the measurement of dynamic properties of aerosol particles (P. Jani, 1997-1999)

OMFB-Technoorg-SZFKI 97-97-47-1592, Investigation of nuclear aerosols (A. Czitrovszky, 1998-1999)

AKP 96/2-615 2.2 Development of high time resolution and high quantum efficiency photodetection system (A. Czitrovszky, 1997-1998) OTKA T-026073 Electronic states, charge carrier localization and their interaction

with the structure in amorphous carbon films (M. Koós, 1998-2000)

OTKA T-025540 STM/AFM investigations of atomic and mesoscopic structures of amorphous carbon (I. Pócsik, 1998-2000)

Publications

Articles

N.1. N. V. Baburin^*, Yu. V. Borozdov^*, Yu. K. Danileiko^*, B.I. Denker^*, A. D.

Ivanov^*, R. Ifflander^*, I. Kertész, N. Kroó, V. V. Osiko^*, S. E. Sverchkov^*, A.

V. Sidorin^*, R. Hack^*, V. A. Chikov^*: Q-switching of a high-power solid-state laser by a fast scanning Fabry-Perot interferometer. Quantum Electronics (RU) 25, 633-637 (1988)

N.2. A. Czitrovszky, P. Jani, L. Maróti^*, L. Matus^*, P. Windberg^*: Composition and concentration of aerosol particles released from simulant LWR fuel rods.

Journal of Aerosol Science 29S1, 471-472 (1998).

N.3. A. Czitrovszky, P. Jani, L. Maróti^*, L. Matus^*, A Pintér^*, P. Windberg^*: Dispersity and structure of aerosol particles released from simulant LWR fuel rods. Journal of Aerosol Science 29S1, 469-470 (1998)

N.4. P. Jani, A. Nagy, A. Czitrovszky: Single nanoparticle size measurement algorithm using photon correlation techniques. Journal of Aerosol Science 29S1, 419-420 (1998)

N.5. M. Koós, I. Pócsik, J. Erostyák^* and A. Buzádi^*: Amorphous Carbon Luminescence: Excitation and Emission in a Broad Energy Range. Journal of Non-Crystalline Solids 227-230, 579-582 (1998).

N.6. I. Pócsik, M. Hundhausen^*, M. Koós and L. Ley^*: Origin of the D peak in the Raman Spectrum of Microscystallline Graphite. Journal of Non-Crystalline Solids 227-230, 1083-1086 (1998).

N.7. S.H. Moustafa, M. Koós and I. Pócsik: DC Electric Properties of Amorphous Carbon with Different Bonding Hybridization. Journal of Non-Crystalline Solids 227-230, 1087-1091 (1998).

N.8. R. Blinc^*, D. Arcon^*, P. Cevc^*, I. Pócsik, M Koós, Z. Trontelj^* and Z. Jaglicic^*:

13C Magnetic Resonance and Electron Spin Resonance of Amorphous Hydrogenated Carbon. Journal of Physics; Condensed Matter 10, 6813-6824 (1998).

N.9. D. Arcon^*, J. Seliger^*, R. Blinc^*, I. Pócsik and M Koós: ¹³C and ¹H Spin-Lattice Relaxation in Amorphous Hydrogenated Carbon. Solid State Communication 107, 349-352 (1998).

Conference proceedings

N.10. M. Koós, T. Lohner^*, S.H. Moustafa and I. Pócsik: Optical Properties of Hydrogenated Amorphous Carbon Determined by Spectral Ellipsometry. In:

Proc. of "Optika '98" 5th Congress on Modern Optics, Budapest, 14-17 Sept.

1998, SPIE 3573, 1998, pp. 328-331.

N.11. B. I. Denker^*, B. I. Galagan^*, V. V. Osiko^*, S. E. Sverchkov^*, I. Kertész: UV luminescence in Y6³⁺-Tm³⁺-Gd³⁺ system excited by IR laser diode. In: Proc.

Conf. OSA TOPS 19. Advanced Solid State Lasers, eds. Rosemberg and Fejer, Opt. Soc. Am., 1998, pp. 450-453.

N.12. A.Czitrovszky, A. Nagy, T. Mosoni^*, P. Jani, K. Bodnár^*, Á. Illés: A new sizing method for liquid-borne particles with high dynamic range. In: Proc. of "Optika '98" 5th Congress on Modern Optics, Budapest, 14-17 Sept. 1998, SPIE 3573, 1998, pp. 225-229.

N.13. A.Czitrovszky, A. Sergieenko^*: Mesurement of qantum efficiency of avalanche photodetectors based on quantum two-photon field. In: Proc. of "Optika '98"

5th Congress on Modern Optics, Budapest, 14-17 Sept. 1998, SPIE 3573, 1998, pp. 332-334.

N.14. A.Czitrovszky, A. Nagy, P. Jani: Estimating of the shape factor of suspended particles in a liquid-borne particle counter. In: Proc. of Internat. Conf. on Applied Optical Metrology, Balatonfüred, Hungary 1998, Eds: P.K. Rastogi, F. Gyimesi, SPIE 3407, 1998, pp. 250-255.

N.15. P. Jani, A. Nagy, A. Czitrovszky: Size distribution of particles in LDA system using back scattering geometry. In: Proc. of Internat. Conf. on Applied Optical Metrology, Balatonfüred, Hungary 1998, Eds: P.K. Rastogi, F. Gyimesi, SPIE 3407, 1998, pp. 262-266.

N.16. I. Pócsik, M. Hundhausen^*, M. Koós, O. Berkesi^* and L. Ley^*: Resonance Raman phenomena in Raman spectroscopy of graphite. In: Proceedings of the Sixteenth International Conference on Raman Spectroscopy Edited by A.M.

Heyns, John Wiley and Sons, New York 1998. Suppl. Vol. pp.: 64-65.

N.17. I. Pócsik, M. Koós, O. Berkesi^* and M. Hundhausen^*: Advantage of infrared excitation in Raman spectroscopy of hydrogenated amorphous carbon films.

In: Proceedings of the Sixteenth International Conference on Raman Spectroscopy. Edited by A.M. Heyns, John Wiley and Sons, New York 1998.

Suppl. Vol. pp.: 66-67.

N.18. I. Pócsik, M. Hundhausen^*, M. Koós, O. Berkesi^* and L. Ley^*: Resonance Raman phenomena in Raman spectroscopy of graphite. In: Proceedings of the International Symposium on Carbon; Science and Technology for New Carbons. Carbon Society of Japan, Tokyo 1998. pp.: 652-653.

N.19. I. Pócsik and M. Koós: Cooling rate dependence on Tg, - caused by clustering.

In: APS Conference Proceedings (accepted for publication)

N.20. I. Kertész, B. Plósz, Yu. K. Danilejko^*, B. I. Denker^*: Q-switching of high average power Nd:YAG laser for material processing. In: Proc. Hungarian-South Korean Conference on Lasers, Budapest, 1998 (accepted for publication)

Book chapters

N.21. I. Pócsik, M. Koós, M. Hundhausen^* and L. Ley^*: Excitation energy dependent Raman and photoluminescence spectra of hydrogenated amorphous carbon. In:

Amorphous Carbon: State of Art, Ed. by S.R.S. Silva, J. Robertson, G.A.J.

Amaratunga and W. I. Milne, Word Scientific, Singapore 1998. pp. 224-233.

N.22. M. Koós and I. Pócsik: Luminescence properties of hydrogenated amorphous carbon. In: Actual problems in luminescence research, Eds. N. Marek and K.

Szabo, Pécs, 1998, pp. 281-304.