Luminescence and THz wave emission from nanostructured materials based III-V semiconductor compounds
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StatusThe thesis was presented on the 23 September, 2011Approved by NCAA on the 11 November, 2011 Abstract – 2.51 Mb / in romanian |
Keywords
Luminescence, microcathodoluminescence, porous structures, random laser emedia, THz emission, optical rectification, field emissionSummary
III-V semiconductor compounds” thesis in physics and mathematics, Chisinau, 2011,
introduction, 3 chapters, conclusions and recommendations, bibliography of 234 titles, 114 pages
of text basic, 86 figures and 2 tables. The results are published in 33 scientific papers.
Keywords: Luminescence, microcathodoluminescence, porous structures, random laser
emedia, THz emission, optical rectification, field emission.
Field of study: Nanotechnologies and new multifunctional nanomaterials.
Aim of the work consists in development of nanoperforated membranes and porous
multilayer structures based on III-V semiconductor compounds, investigation of possibilities to
modify properties by changing morphology of porous structures and doping these structures with
rare earth elements, exploration of microcathodoluminescence, photoluminescence, THz
emission under optical excitation, field emission and surface plasmon resonance of metal dots
deposited in porous membranes.
Objectives: Development of multilayer porous structures by chemical etching and their
cathodoluminescence study for the identification of lattice defects. Development of luminescent
nanomaterials based on porous semiconductors doped with rare earth elements for applications
in random lasers. Frequency control of plasmon resonance of metal dots deposited in porous
structures. Implementation of THz spectroscopy for the characterization of nanoporous
membranes and exploration of THz emission from these membranes under optical excitation.
Investigation of field emission from nanostructured film.
Novelty and scientific originality. By using scanning electron microscopy, energy
dispersive X-ray analysis and CL spectroscopy it is demonstrated that an oxide layer is formed at
the surface of the porous GaP skeleton after the electrochemical etching, which is contributing to
the decrease of the density of surface energy states and, consequently, to the decrease of nonradiative
recombination rate and to the increase of the CL intensity. On the other hand, no oxide
layer is formed in porous InP during electrochemical etching. Therefore, the density of surface
states increases after electrochemical etching and the CL intensity considerable decreases. THz
emission from an optically excited nanoperforated InP membrane was observed for the first time,
and a considerable increase of the emission intensity was demonstrated by irradiating the porous
InP membrane with high energy Kr+23i Xe+15 ions. It was shown that the main contribution to
the generation of THz waves comes from optical rectification processes. The possibility to
control the surface plasmon resonance in Ag nanoparticles deposited electrochemically in porous
GaP templates was demonstrated. Technological conditions for preparation of highly textured
InAs layers with nanoneedle morphology have been developed, and their field emitter
applications have been demonstrated.
Scientific problem solved here is to obtain new materials with promising properties for use
in micro-lasers, THz emitters, vacuum electronics as well as to demonstrate the possibility of
controlling of surface plasmonic resonance by electrochemically deposited metal nanoparticles
in porous templates.
Theoretical significance and applied value. The spatial distribution of luminescence
intensity from porous InP and GaP layers has been studied by meals of
microcathodoluminescence. Porous GaP and GaAs templates prove to be suitable for the
incorporation and activation of rare earth ions, and for the preparation of active random laser
media. It was shown that plasmon resonance spectrum can be modified depending on the
density, size and shape of Ag nanoparticles deposited inside the porous GaP template. A
technology has been developed for the preparation of porous thin InP membranes cut from a
single substrate, which can be used as THz generators. It was shown for the first time that ion
irradiation of porous InP wafer with inert gases results in the production of a new nanomaterial
with considerable enhanced THz emission intensity under optical excitation. A new technology
has been developed to obtain highly textured InAs surfaces with specific nanoneedle
morphology for application as field emitters.
Oficial Reviewers
- Dmitrii Nedeoglo
doctor habilitat, professor, Moldova State University - Traian Dascalu
doctor, INFLPR, Măgurele, Romania
Council's Members
- Petru Gaşin, president
doctor habilitat, professor, Moldova State University - Dormidont Şerban, secretary
doctor habilitat, Institute of Applied Physics of the - Eugen Gheorghiţă, member
doctor habilitat, professor, Tiraspol State University - Valerian Dorogan, member
doctor habilitat, professor, Technical University of Moldova - Emil Rusu, member
doctor habilitat, associate professor (docent), Practical Scientific Institute of Horticulture and Food Technology - Mihail Caraman, member
doctor habilitat, professor, Moldova State University
Theses
