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Luminescence and THz wave emission from nanostructured materials based III-V semiconductor compounds


Author: Sîrbu Lilian
Degree:doctor of physics and mathematics
Speciality: 01.04.10 - Semiconductors physics and engineering
Year:2011
Scientific adviser: Ion Tighineanu
doctor habilitat, professor, Institute of Mathematics and Computer Science, Academy of Sciences of Moldova
Institution: Technical University of Moldova
Scientific council: DH 30-01.04.10-23.04.09
Moldova State University

Status

The thesis was presented on the 23 September, 2011
Approved by NCAA on the 11 November, 2011

Abstract

Adobe PDF document2.51 Mb / in romanian

Keywords

Luminescence, microcathodoluminescence, porous structures, random laser emedia, THz emission, optical rectification, field emission

Summary

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.