Petr Malý

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Group subject:

II-VI nad III-V semiconductor based nanostructures


Name and Curriculum vitae of contact person:

Petr Malý (Prof., RNDr. , DrSc)

Affiliation:

Charles University in Prague, Faculty of Mathematics and Physics

Position - Professor, Head of Division of Quantum Optics and Optoelectronics, Dept. of Chemical Physics and Optics

Fields of scientific activity:

• Femtosecond and picosecond laser spectroscopy

• Ultrafast processes in semiconductors

• Semiconductor nanocrystals (quantum dots) II-VI materials, silicon

• Chemical bath deposition of CdS, CdSe nanocrystalline films

• The supervisor of 18 successful diploma theses, 5 PhD theses.

Publications:

Author or co-author of more than 100 scientific publications (more than 50 were published in international journals) to which more than 186 references appeared in the literature. Amongst these there are joint papers with the University of Oxford, University of Yamaguchi, University of Lecce, University of Strasbourg.

Selected study stays abroad:

• In 1985-6 a 10 month's visit to Oxford University (Prof. J. F. Ryan, Clarendon Lab.)

• During 1990 – 2001 several visits on invitation and/or in the framework of mutual projects to Oxford University (Prof. J. F. Ryan, Clarendon Lab.), in total more than a year spent in the Clarendon Lab

• In 1997, 2000, and 2003 invited by Prof. T. Miyoshi as visiting Assoc. Prof. to Yamaguchi University, Japan , in total more than 5 months spent at Yamaguchi University
Selected solved projects:

• EC ERB CHRX CT 93 0133 (1994-7) Network: Ultrafast processes in semiconductors

• EC ERB FMRX CT 97 0134(1998-2001) Network: Ultrafast Quantum Optoelectronics

Selected related publications from last 5 years:

• P. Němec, P. Malý: Temperature study of trap-related photoluminescence decay in CdSSe nanocrystals in glass, J. Appl. Phys.87, 3342 (2000)

• P. Němec, P. Malý, M. Nikl, K. Nitsch: Auger recombination as a probe of the Mott transition in semiconductor nanocrystals, Appl. Phys. Lett.76, 2850 (2000)

• P. Malý, J. Kudrna, F. Trojánek, D. Mikeš, P. Němec, A.C. Maciel, J. F. Ryan: Dominant role of surface states in photoexcited carrier dynamics in CdSe nanocrystalline films prepared by chemical deposition, Appl. Phys. Lett. 77, 2352 (2000)

• F. Trojánek , R. Cingolani, D.Cannoletta, D. Mikeš, P. Němec , E. Uhlířová , J. Rohovec , P. Malý: Tailoring of nanocrystal sizes in CdSe films prepared by chemical deposition, J. Cryst. Growth 209, 695 (2000)

• J. Kudrna , F. Trojánek, P. Malý, I. Pelant: Carrier diffusion in microcrystalline silicon studied by the picosecond laser induced grating technique, Appl. Phys. Lett. 79, 626 (2001)

• P. Němec, I. Němec, P. Nahálková, F. Trojánek, and P. Malý: Ammonia free method for preparation of CdS nanocrystalline films by chemical solution deposition technique, J. of Cryst. Growth 240, 484 (2002).

Group members:

Roman Grill, Jan Franc, Pavel Höschl, Milan Zvára, Pavel Hlídek, Eduard Belas, Pavel Moravec, Milan Orlita, Petr Horodyský, Mykhaylo Shumylyak, Petr Malý, Ivan Pelant(IP-ASCR), Petr Němec, František Trojánek, Miroslav Šimurda, Petra Nahálková

Main Research Subjects:

●Dynamics of elementary excitations in semiconductor nanocrystals studied by techniques of femtosecond and picosecond spectroscopy. The research is focused on the question: How are the carrier and phonon dynamics affected by the effect of three dimensional quantum confinement, by the role of the nanocrystal surface, and by the inter-nanocrystal interactions.

●Preparation of CdS and CdSe nanocrystalline thin films by chemical bath deposition, tailoring of the optoelectronic and photonic properties (nanocrystals with 5 – 20 nm diameters, tailoring of the band-gap, photoluminescence efficiency, photoexcited carrer lifetimes, optical nonlinearities).

●Dynamics of spin polarized photoexcited carriers in nanocrystals studied by femtosecond spin-sensitive techniques. The aim of the research is to understand the microscopical mechanisms of spin relaxation and to find a way of tailoring the spin coherence time important e.g. in potential applications in spintronics and quantum computing.

●Optical and magnetooptical properties of quantum structures grown on GaAs/GaAlAs material. Experimental and theoretical research is focused on double quantum wells (spatially direct and indirect excitons, their condensation to a cold exciton gas at low temperatures). The quantum structures are grown by MBE in the Institute of Physics, AS CR and Institute of Technical Physics, University Erlangen, Germany. Some measurements are done in Grenoble High Magnetic Field Laboratory, France.

●Preparation of substrates on CdTe and (CdZn)Te for MBE. The principal task is the increase of the yield connected with the reduction of bulk defects and optimization of surface finish. The CdTe and Cd(ZnTe) substrates are prepared for fabrication of quantum structures in cooperation with the University of Chicago and University Würzburg.

Selected Specific Equipment:

Picosecond laser laboratory is based on Nd:YAG laser system followed by nonlinear transformation of wavelengths, which provides 35 ps pulses in the spectral interval 266 – 3000 nm. In the femtosecond laboratory, a Ti:sapphire laser system (Spectra Physics) provides 70 fs pulses tunable from 720 to 980 nm. Second harmonics and femtosecond continuum generation in a hollow fiber are further ways of spectral tuning. The experimental techniques of time-resolved laser spectroscopy available are: pump & probe for absorption/reflection measurements, degenerate/nondegenerate four wave mixing, photoluminescence streak camera and up-conversion measurements, femtosecond techniques for spin dynamics measurements. Measurements can be done in temperature range 10 –300 K.

The optical laboratory (Institute of Physics, Charles University in Prague) comprises basic equipment for optical spectroscopy. The fundamental part of the high resolution photoluminescence experiment is represented by a Fourier Transform Infrared Spectrometer, Model Bruker IFS 66/S (spectral range from 100 cm-1 to 15 000 cm-1 , the maximum spectral resolution 0.1 cm-1 ). The photoluminescence set-up is completed by excitation lasers (10 mW He-Ne laser Siemens and 100 mW argon laser (Spectra Physics)) and Leybold VSK-4 continuous flow helium optical cryostat for temperatures down to 4.2 K. The basic device for magneto-luminescence measurements is represented by Oxford Instruments SpectroMag SM4000 superconducting magnet in optical cryostat (maximum field 11.5T at 2.2K, both Faraday and Voigt configurations are possible, the temperature range 1.6K – 300 K).

Additional recent selected publications by group members:

●J.Soubusta, R.Grill, P.Hlídek, M.Zvára, L.Smrčka, S.Malzer, W.Geisselbrecht, and G.H.Döhler: Excitonic photoluminescence in symmetric coupled double quantum wells subject to an external electric field, Phys. Rev. B 60, 7740-7743 (1999).

●R.Grill, and G.H.Döhler: Effect of charged donor correlation and Wigner liquid formation on the transport properties of a two-dimensional electron gas in modulation δ-doped heterojunctions, Phys. Rev. B 59, 10769 - 10777. (1999).

● P.Hlídek, J.Bok, J.Franc, and R.Grill: Refractive index of CdTe: spectral and temperature dependence, J. Appl. Phys. 90, 1672-1674 (2001).

● J.Franc, R.Grill, P.Hlídek, E.Belas, L.Turjanska, P.Höschl, I.Turkevych, A.L.Toth, P.Moravec,and H.Sitter: The influence of growth conditions on the quality of CdZnTe single crystals, Semicond. Sci. Technol. 16, 514-520 (2001).

● R.Grill, C.Metzner, and G.H.Döhler: Unrestricted Hartree-Fock cluster calculation of electronic and optical properties of δ-doped n-i-p-i semiconductors, Phys. Rev. B 63, 235316 (2001).

● M.Zvára, R.Grill, P.Hlídek, M.Orlita, J.Soubusta: Photoluminescence of biased GaAs/Alx Ga1-x As double quantum wells - many-body effects, Physica E 12 335-339 (2002).
© 2005