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Morphology and optical properties of semiconductor and dielectric matrices based nanocomposits from InP, Al2O3 and TiO2


Author: Enachi Mihail
Degree:doctor of physics and mathematics
Speciality: 01.04.10 - Semiconductors physics and engineering
Year:2015
Scientific adviser: Ion Tighineanu
doctor habilitat, professor, Institute of Mathematics and Computer Science of the ASM
Scientific consultant: Veaceslav Ursachi
doctor habilitat, professor, Institute of Applied Physics of the ASM
Institution: Technical University of Moldova

Status

Term of presenting of the thesis 3 June, 2015

Abstract

Adobe PDF document1.07 Mb / in romanian

Thesis

CZU 621.315.592

Adobe PDF document 7.71 Mb / in romanian
168 pages


Keywords

nanostructures, nanotubes, luminiscence, microcathodoluminiscence, random microlasers, negative refraction index lenses, metamaterials, nanosensors

Summary

The thesis was performed at UTM, Chişinău, in 2014. It is written in Romanian and consists of introduction, 4 chapters, general conclusions and recommendations, 217 title bibliography, 148 base text pages, 109 figures, 5 tables. The results are published in 24 scientific works.

Field of study: nanotechnology and novel functional nanomaterials.

Aim of the work: development of nanoporous and nanotubular matrices based on semiconducting and dielectric materials, identification of methods for controllable modification of morphology, luminiscence, microcathodoluminiscence, refraction index, sensitivity, plasmonic resonance as well as of persistent photoconductivity in nanotubular and nanoporous membranes.

Objectives: Development of nanotubular and nanoporous structures by means of electrochemical anodization. Development of their doping technology and modification of their crystaline structure. Development of luminiscent nanomaterials based on nanostructured as well as rare earth and transition metal doped oxides for random microlasers applications. Investigation of cathodoluminiscence emission and resonators formation in TiO2 clusters. Development of optical sensors and photocatalytic materials with improved properties by aplying the plasmonic resonance effect in nanostructured matrices. Determination of aplicability and methods to produce photonic lenses based on TiO2 nanotubular matrices. Development of the technology for controlled modification of nanostructured matrix crystalline structure. Development of nanosensors based on nanostructured materials.

Novelty and scientific originality. The possibility to control the morphology and geometric dimensions of TiO2 and Al2O3 nanotubular matrices by changing the Al and Ti foil electrochemical anodization temperature. The channels of radiative recombination in rare earth and transition metal ion doped InP and Al2O3 templates and TiO2 nanotube matrices were determined by means of luminiscence and microcathodoluminiscence. Stimulated emission and random laser effect in Al2O3 nanostructures were demonstrated as well as the formation of resonators supporting whispering gallery modes in a TiO2 nanotube cluster. The deposition of Ag and Au films on TiO2 nanotubes proved to enhance the luminiscence intensity in different spectral regions. In the case of InP membranes, the photoexcitation pulse changed the surface charge density. The possibility to controllably „write” the crystalline structure in TiO2 membranes by means of a laser beam was demonstrated.

The solved scientific problem consists in the development of technology for the production of nanocomposit materials based on InP and Al2O3 porous templates and TiO2 nanotube matrices for random laser, optoelectronic switch, plasmonic and photonic device applications.

Theoretical significance and practical value of the work. Micro-CL made the visualization and study of the spectral distribution of luminiscence from TiO2 singular nanotubes possible. InP, Al2O3 and TiO2 nanostructured templates proved to be useful for the incorporation of rare earth element and transition metal ions as well as for their activation for their application in random microlasers. Thin coatings of Au and Ag proved to influence the plasmonic resonance spectrum in TiO2 nanotubular structures. The process of quasi-photoinduced modification of conductivity proved to allow the quasi-permanent modification of the conductivity of InP porous membranes. A new technology for the production of optical waveguides based on the controlled modification of the crystalline structure of nanotubular matrices by focused laser beam irradiation was developed. TiO2 singular nanotubes proved to be useful as gas sensors.