Nd:Glass laser-induced damage to thin films, two-photon excited fluorescence and plasma studies

Laser-induced damage is the principal limiting constraint in the design and operation of high-power laser systems used in fusion and other high-energy laser applications. Therefore, an understanding of the mechanisms which cause the radiation damage to the components employed in building a laser and a knowledge of the damage threshold of these materials are of great importance in designing a laser system and to operate it without appreciable degradation in performance. This thesis, even though covers three distinct problems for investigations using a dye Q-switched multimode Nd:glass laser operating at 1062 nm and emitting 25 ns (FWHM) pulses, lays its main thrust on damage threshold studies on thin films. Using the same glass laser two-photon excited fluorescence in rhodamine 6G and generation and characterisation of a carbon plasma have also been carried out. The thesis is presented in seven chapters.

Evidence of extended orientational order in amorphous Fe/Sm thin films

Amorphous thin films of Fe/Sm, prepared by evaporation methods, have been magnetically characterized and the results were interpreted in terms of the random magnets theory. The samples behave as 2D and 3D random magnets depending on the total thickness of the film. From our data the existence of orientational order, which greatly influences the magnetic behavior of the films, is also clear.

Competing tunneling and capacitive paths in Co-ZrO2 granular thin films

The ac electrical response is studied in thin films composed of well-defined nanometric Co particles embedded in an insulating ZrO2 matrix which tends to coat them, preventing the formation of aggregates. In the dielectric regime, ac transport originates from the competition between interparticle capacitive Cp and tunneling Rt channels, the latter being thermally assisted. This competition yields an absorption phenomenon at a characteristic frequency 1/(RtCp), which is observed in the range 1010 000 Hz. In this way, the effective ac properties mimic the universal response of disordered dielectric materials. Temperature and frequency determine the complexity and nature of the ac electrical paths, which have been successfully modeled by an Rt-Cp network.

Growth and magnetic properties of multiferroic LaxBi1-xMnO3 thin films

A comparative study of LaxBi1-xMnO3 thin films grown on SrTiO3 substrates is reported. It is shown that these films grow epitaxially in a narrow pressure-temperature range. A detailed structural and compositional characterization of the films is performed within the growth window. The structure and the magnetization of this system are investigated. We find a clear correlation between the magnetization and the unit-cell volume that we ascribe to Bi deficiency and the resultant introduction of a mixed valence on the Mn ions. On these grounds, we show that the reduced magnetization of LaxBi1-xMnO3 thin films compared to the bulk can be explained quantitatively by a simple model, taking into account the deviation from nominal composition and the Goodenough-Kanamori-Anderson rules of magnetic interactions.

A study of the preparation and characterization of bismuth telluride and bismuth oxide thin films

This thesis deals with the preparation and properties of two compounds of V-II family, viz. bismuth telluride and bismuth oxide, in thin filmform. In the first chapter is given the resume of basic solid state physics relevant to the work reported here. In the second chapter the different methods of thin film preparationtia described. Third chapter deals with the experimental techniques used for preparation and characterization of the films. Fourth chapter deals with the preparation and propertiesof bismuth telluride films. In next four chapters, the preparation and properties of bismuth oxide films are discussed in detail. In the last chapter the use of Bi205 films in the fabrication of Heat mirrors is examined and discussed.