Radhakrishnan, M K; Dr.Joy, George(Cochin University of Science And Technology, February , 1981)
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Abstract:
The Thesis consist of the study of the electrical properties of antimony trisulphide films and the electrical behaviour of different metal contacts to antimony trisulphide films. Since the thermal evapouration of the compound antimony trisulphide as such mayresult in nonstoichiometric compound films , sb2s3 films in the present work were mostly prepared by the three temperature method ,keeping the substrate at different temperature ranging from 3031 to 4231 and evapourating antimony and sulphur simultaneously from separate sources.
Description:
Department of Physics, Cochin University of Science And Technology
Urmila, K. S; Dr. Pradeep, B.(Cochin University of Science and Technology, August 6, 2016)
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Abstract:
The use of energy in our day to day life has grown exponentially and
conserving energy to meet the world’s escalating energy demands is the need of
the hour. During the past decade there is a heightened awareness all over the
world that the production costs of energy from coal, oil and natural gas is
increasingly higher and at the same time the energy technologies involving their
use are contributing to a serious rise in the greenhouse gases in the environment
and a consequent global warming. As a result, more attention is focused on the
utilization of clean energy technologies, especially solar energy which has a
great potential to meet a large fraction of world’s energy demands using
photovoltaics (PV). The heart of the PV system that efficiently convert sunlight
directly into electricity through photovoltaic effect is the solar cell - originally
developed for space applications in the 1950s, are now used in consumer
products, mounted on roofs of houses or assembled into large power stations.
Joseph, K S; Dr.George, Joy(Cochin University of Science and Technology, 1983)
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Abstract:
In this thesis the preparation and properties of thin films of certain semiconducting sulphides (sulphides of tin, copper and indium) are reported. As single source evaporation does not yield satisfactory films of these compounds for a variety of reasons, reactive evaporation of the metal in a sulphur atmosphere has been used for film preparation. It was found that for each metal sulphide a stoichimetric interval of fluxes and substrate temperature exists for the formation of the compound in accordance with the analysis of Guenther. The first chapter of the thesis gives a resume of the basic principles of semiconductor physics relevant to the work reported here. In the second chapter is discussed in detail the reactive evaporation techniques like ordinary reactive evaporation, activated reactive evaporation and reactive ion plating. Third chapter deals with the experimental techniques used in this study for film preparation and characterization. In the next seven chapters is discussed the preparation and properties of the compound films studied. The last chapter gives a general theory of the formation of compound films in various deposition techniques in terms of the kinetic energy of the film forming particles. It must be mentioned here that this is of fundamental importance to thin film deposition and is virtually untouched in the literature
Description:
Department of Physics, Cochin University of Science and Technology
Benoy, M D; Dr.Pradeep, B(Cochin University of Science and Technology, May 7, 2001)
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Abstract:
The investigation of physical properties of matter has progressed so much
during the last hundred years. Today physics is divided in to a large distinct group
of special branches. These branches are distinguished by the particular area
studied, method of investigation and so on. An independent and important branch
that has developed is the physics ofthin films.Any object in solid or liquid form with one of its dimensions very much
smaller than that of the other two may be called a thin film. It is having only one
common property, namely, one of their dimensions is very small, though all their
physical properties may be different. Thin layers of oil, floating on the surface of
water, with their fascinating colours, have attracted men’s curiosity from time
immemorial. The earliest application of thin films was the protective coatings in
the form of paints. A thin layer of tin has been used from ancient times to protect
copper utensils from corrosion. Indium thin films are used in certain applications
on account of their good lubricating property. Relay contacts are coated with thin
films of rare earth metals in order to prevent burning due to arcing. Hard coatings
are also available using diamond like carbon (i-carbon). The basic properties of
thin films are of considerable interest because of their potential applications in
various fields of science and technology
Description:
Department of Physics, Cochin University of Science And
Technology
Sajimol Augustine, M; Dr.Jayalekshmi, S(Cochin University Of Science And Technology, December 20, 2012)
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Abstract:
Fluorescence is a powerful tool in biological research, the relevance of
which relies greatly on the availability of sensitive and selective fluorescent
probes. Nanometer sized fluorescent semiconductor materials have attracted considerable attention in recent years due to the high luminescence intensity, low
photobleaching, large Stokes’ shift and high photochemical stability. The optical
and spectroscopic features of nanoparticles make them very convincing
alternatives to traditional fluorophores in a range of applications. Efficient surface
capping agents make these nanocrystals bio-compatible. They can provide a novel
platform on which many biomolecules such as DNA, RNA and proteins can be
covalently linked. In the second phase of the present work, bio-compatible,
fluorescent, manganese doped ZnS (ZnS:Mn) nanocrystals suitable for bioimaging
applications have been developed and their cytocompatibility has been
assessed. Functionalization of ZnS:Mn nanocrystals by safe materials results in
considerable reduction of toxicity and allows conjugation with specific
biomolecules. The highly fluorescent, bio-compatible and water- dispersible
ZnS:Mn nanocrystals are found to be ideal fluorescent probes for biological
labeling
Description:
Department of Physics, Cochin University of Science and
Technology
Sabir, M; Dr.Babu, Joseph K(Cochin University of Science and Technology, 1978)
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Abstract:
The present thesis deals with the studies on certain aspects of pathological higher field theories .It brings to light some new abnormalities and new samples of abnormal theories and also puts forward a novel approach towards the construction of trouble free theories
Description:
Department of Science, Cochin University of Science and Technology
Gregorios, Mathew; Dr. Jacob, Philip(Cochin University of Science and Technology, December , 1998)
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Abstract:
In this thesis, we present the results of our investigations on the photoconducting
and electrical switching properties of selected chalcogenide glass systems. We have used
XRD and X-ray photoelectron spectroscopy (XPS) analysis for confinuing the amorphous
nature of these materials and for confirming their constituents respectively.Photoconductivity is the enhancement in electrical conductivity of materials
brought about by the motion of charge carriers excited by absorbed radiation. The
phenomenon involves absorption, photogeneration, recombination and transport processes
and it gives good insight into the density of states in the energy gap of solids due to the
presence of impurities and lattice defects. Photoconductivity measurements lead to the
determination of such important parameters as quantum efficiency, photosensiti\'ity,
spectral sensitivity and carrier lifetime. Extensive research work on photoconducting
properties of amorphous semiconductors has resulted in the development of a variety of
very sensitive photodetectors. Photoconductors are finding newer and newer uses eyery
day. CdS, CdSe. Sb2S3, Se, ZnO etc, are typical photoconducting materials which are used
in devices like vidicons, light amplifiers, xerography equipment etc.Electrical switching is another interesting and important property possessed by
several Te based chalcogenides. Switching is the rapid and reversible transition between a
highly resistive OFF state, driven by an external electric field and characterized by a
threshold voltage, and a low resistivity ON state, Switching can be either threshold type
or memory type. The phenomenon of switching could find applications in areas like
infonnation storage, electrical power control etc. Investigations on electrical switching in
chalcogenide glasses help in understanding the mechanism of switching which is
necessary to select and modify materials for specific switching applications.Analysis of XRD pattern gives no further infonuation about amorphous materials
than revealing their disordered structure whereas x-ray photoelectron spectroscopy,XPS)
provides information about the different constituents present in the material. Also it gives binding energies (b.e.) of an element in different compounds and hence b.e. shift from the
elemental form.Our investigations have been concentrated on the bulk glasses, Ge-In-Se, Ge-Bi-Se
and As-Sb-Se for photoconductivity measurements and In-Te for electrical switching. The
photoconducting properties of Ge-Sb-Se thin films prepared by sputtering technique have
also been studied. The bulk glasses for the present investigations are prepared by the melt
quenching technique and are annealed for half an hour at temperatures just below their
respective glass transition temperatures. The dependence of photoconducting propenies on
composition and temperature are investigated in each system. The electrical switching
characteristics of In-Te system are also studied with different compositions and by varying
the temperature.
Description:
Department of Instrumentation,
Cochin University of Science and Technology
Sreekanth, Varma J; Dr.Jayalekshmi, S(Cochin University of Science and Technology, September , 2012)
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Abstract:
Light emitting polymers (LEP) have drawn considerable attention because of their numerous potential applications in the field of optoelectronic devices. Till date, a large number of organic molecules and polymers have been designed and devices fabricated based on these materials. Optoelectronic devices like polymer light emitting diodes (PLED) have attracted wide-spread research attention owing to their superior properties like flexibility, lower operational power, colour tunability and possibility of obtaining large area coatings. PLEDs can be utilized for the fabrication of flat panel displays and as replacements for incandescent lamps. The internal efficiency of the LEDs mainly depends on the electroluminescent efficiency of the emissive polymer such as quantum efficiency, luminance-voltage profile of LED and the balanced injection of electrons and holes. Poly (p-phenylenevinylene) (PPV) and regio-regular polythiophenes are interesting electro-active polymers which exhibit good electrical conductivity, electroluminescent activity and high film-forming properties. A combination of Red, Green and Blue emitting polymers is necessary for the generation of white light which can replace the high energy consuming incandescent lamps. Most of these polymers show very low solubility, stability and poor mechanical properties. Many of these light emitting polymers are based on conjugated extended chains of alternating phenyl and vinyl units. The intra-chain or inter-chain interactions within these polymer chains can change the emitted colour. Therefore an effective way of synthesizing polymers with reduced π-stacking, high solubility, high thermal stability and high light-emitting efficiency is still a challenge for chemists. New copolymers have to be effectively designed so as to solve these issues. Hence, in the present work, the suitability of a few novel copolymers with very high thermal stability, excellent solubility, intense light emission (blue, cyan and green) and high glass transition temperatures have been investigated to be used as emissive layers for polymer light emitting diodes.
Description:
Division for Research in Advanced Materials
Department of Physics, Cochin University of Science and Technology