Valsala Kumari, C K; Dr.Joy, George(Cochin University of Science and Technology, 1984)
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Abstract:
During the past few decades, a wide spread interest in the structural, optical, electrical and other physical properties of the transition metal dichalcogenide
layer compounds has evolved. The members of this family of compounds can be regarded as stronglybonded two dimensional chalcogen-metal-chalcogen layers
which are loosely coupled to one another by the weak van der Waal's forces. Because of this type of bonding, the crystals are easily cleavable along the basal plane and show highly anisotropic properties. This thesis contains the growth and the study of the physical properties of certain tin dichalcogenide
crystals (SnS2 and Snsea). Tin disulphide and tin diselenide crystallize in the hexagonal CdI2 type crystalstructure. This structure consists of layers of tin
atoms sandwiched between two layers of chalcogen atoms. Aitin atom is surrounded by six chalcogen atoms octahedrally. In the layers the atoms are held together by covalent bonding and in between the layers there is
van der Waal's bonding.
Description:
Department of Physics, Cochin University of Science and Technology
Valsala Kumari, C K; Dr.Joy, George(Cochin University of Science and Technology, September 20, 1984)
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Abstract:
During the past few decades, a wide spread interest in the structural, optical, electrical and
other physical properties of the transition metal dichalcogenide layer compounds has evolved. The members of this family of compounds can be regarded as strongly bonded two dimensional chalcogen-metal~chalcogen layers which are loosely coupled to one another by the weak ven
der Waal's forces. Because of this type of bonding, the crystals are easily cleavable along the basal plane and show highly anisotropic properties. This thesis contains the growth and the study
of the physical properties of certain tin dichalcogenide crystals (SnS2 and SnSe2). Tin disulphide and tin diselenide crystallize in the hexagonal CdI2 type crystal structure. This structure consists of layers of tin atoms sandwiched between two layers of chalcogen atoms. A tin atom is surrounded by six chalcogen atoms octahedrally.In the layers the atoms are held together by
covalent bonding and in between the layers there is van der Waal's bonding.
Description:
Department of Physics, Cochin University of Science and Technology
George, Peter; Dr.Joy, George(Cochin University Of Science And Technology, July 11, 1986)
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Abstract:
Over the past years there has been considerable interest in the
growth of single crystals both from the point of view of basic research
and technological application. With the revolutionary emergence
of solid state electronics which is based on single crystal technolo8Ys
basic and applied studies on crystal growth and characterization
_have gained a-more significant role in material science. These studies
are being carried out for single crystals not only of semiconductor
and other electronic materials but also of metals and insulators.
Many organic crystals belonging to the orthorhombic class exhibit
ferroelectric, electrooptic, triboluminescent and piezoelectric properties.
Diammonium Hydrogen Citrate (DAHC) crystals are reported to
be piezoelectric and triboluminescent /1/. Koptsik et al. /2/ have
reported the piezoelectric nature of Citric Acid Monohydrate (CA)
crystals. And since not much work has been done on these crystals,
it has been thought useful to grow and characterize these crystals.
This thesis presents a study of the growth of these crystals
from solution and their defect structures. The results of the microindentation and thermal analysis are presented. Dielectric, fractographic, infrared (IR) and ultraviolet (UV) studies of DAHC crystals are also reported
Description:
Department of Physics, Cochin University
of Science and Technology
Kunjomana, A G; Dr.Elizabeth, Mathai(Cochin University Of Science And Technology, August 10, 1992)
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Abstract:
The physical properties of solid matter are
basically influenced by the existence of lattice defects;
as a result the study of crystal defects has assumed
a central position in solid state physics and materials
science. The study of dislocations ixa single crystals
can yield a great deal of information on the mechanical
properties of materials. In order to secure a full understanding
of the processes taking place in semiconducting
materials, it is important to investigate the microhardness
of these materials-—the most reliable method of
determining the fine structure of crystals, the revelation
of micro—inhomogenities in the distribution of impurities,
the effect of dislocation density on the mechanical
properties of crystals etc. Basically electrical conductivity
in single crystals is a defect controlled phenomenon
and hence detailed investigation of the electrical properties
of these materials is one of the best available
methods for the study of defects in them. In the present
thesis a series of detailed studies carried out in Te—Se
system, Bi2Te3 and In2Te3 crystals using surface topographical,
dislocation and microindentation analysis as well as
electrical measurements are presented
Description:
Department of
Physics, Cochin University of Science and Technology
Ajimsha, R S; Jayaraj, M K(Department of Physics, February , 2008)
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Abstract:
Transparent conducting oxides (TCO’s) have been known and used for technologically important applications for more than 50 years. The oxide materials such as In2O3, SnO2 and impurity doped SnO2: Sb, SnO2: F and In2O3: Sn (indium tin oxide) were primarily used as TCO’s. Indium based oxides had been widely used as TCO’s for the past few decades. But the current increase in the cost of indium and scarcity of this material created the difficulty in obtaining low cost TCO’s. Hence the search for alternative TCO material has been a topic of active research for the last few decades. This resulted in the development of various binary and ternary compounds. But the advantages of using binary oxides are the easiness to control the composition and deposition parameters. ZnO has been identified as the one of the promising candidate for transparent electronic applications owing to its exciting optoelectronic properties. Some optoelectronics applications of ZnO overlap with that of GaN, another wide band gap semiconductor which is widely used for the production of green, blue-violet and white light emitting devices. However ZnO has some advantages over GaN among which are the availability of fairly high quality ZnO bulk single crystals and large excitonic binding energy. ZnO also has much simpler crystal-growth technology, resulting in a potentially lower cost for ZnO based devices.
Most of the TCO’s are n-type semiconductors and are utilized as transparent electrodes in variety of commercial applications such as photovoltaics, electrochromic windows, flat panel displays. TCO’s provide a great potential for realizing diverse range of active functions, novel functions can be integrated into the materials according to the requirement. However the application of TCO’s has been restricted to transparent electrodes,
ii
notwithstanding the fact that TCO’s are n-type semiconductors. The basic reason is the lack of p-type TCO, many of the active functions in semiconductor originate from the nature of pn-junction. In 1997, H. Kawazoe et al reported the CuAlO2 as the first p-type TCO along with the chemical design concept for the exploration of other p-type TCO’s. This has led to the fabrication of all transparent diode and transistors.
Fabrication of nanostructures of TCO has been a focus of an ever-increasing number of researchers world wide, mainly due to their unique optical and electronic properties which makes them ideal for a wide spectrum of applications ranging from flexible displays, quantum well lasers to in vivo biological imaging and therapeutic agents. ZnO is a highly multifunctional material system with highly promising application potential for UV light emitting diodes, diode lasers, sensors, etc. ZnO nanocrystals and nanorods doped with transition metal impurities have also attracted great interest, recently, for their spin-electronic applications
This thesis summarizes the results on the growth and characterization of ZnO based diodes and nanostructures by pulsed laser ablation. Various ZnO based heterojunction diodes have been fabricated using pulsed laser deposition (PLD) and their electrical characteristics were interpreted using existing models. Pulsed laser ablation has been employed to fabricate ZnO quantum dots, ZnO nanorods and ZnMgO/ZnO multiple quantum well structures with the aim of studying the luminescent properties.
Sreeja, R; Dr.Jayaraj, M K(Cochin University Of Science And Technology, July 6, 2011)
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Abstract:
Nonlinear optics has been a rapidly growing field in recent decades since the
invention of lasers. The systematic progress in the laser technology increases our
efficiency in the generation and control of coherent optical radiations. Nonlinear
optics is based on the study ofeffects and phenomena related to the interaction of
intense coherent light radiation with matter. Compared to other light sources laser radiation can provide high directionality, high monochromaticiry, high brightness
and high photon degeneracy. At such a very intense incident beam, the matter
responds in a nonlinear manner to the incident radiation fields, which endows the
media :1 characteristic to change the refractive index or absorption coe fflcient of the
media or the wavelength, or the frequency of the incident electromagnetic waves.
This thesis encompasses the fabrication of nonlinear optical devices based on
semiconductor and metal nanostructures. The presented work focus on the
experimental and theoretical discussions on nonlinear optical effects especially
nonlinear absorption and refraction exhibitted by metal and semiconductor nanostructures
Description:
Optoelectronic Devices Laboratory
Department of Physics
Cochin University of Science and Technology
Vimalkumar, T V; Dr.Vijayakumar, K P(Cochin University of Science & Technology, August , 2011)
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Abstract:
In the present work we report the preparation details studies on ZnO thin films. ZnO
thin films are prepared using cost effective deposition technique viz., Chemical Spray
Pyrolysis (CSP). The method is very effective for large area preparation of the ZnO thin
film. A new post-deposition process could also be developed to avoid the adsorption of
oxygen that usually occurs after the spraying process i.e., while cooling. Studies were done
by changing the various deposition parameters for optimizing the properties of ZnO thin
film. Moreover, different methods of doping using various elements are also tried to
enhance the conductivity and transparency of the film to make these suitable for various
optoelectronic applications.
Description:
Department of Physics,
Cochin University of Science and Technology
Navya, Antony; Dr.Mohanan, P V(Cochin University of Science And Technology, March 25, 2014)
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Abstract:
Several natural and synthetic supports have been assessed for their efficiency
for enzyme immobilization. Synthetic polymer materials are prepared by chemical
polymerization using various monomers. As a kind of important carrier, synthetic
polymer materials exhibit the advantages of good mechanical rigidity, high specific
surface area, inertness to microbial attack, easy to change their surface characteristics,
and their potential for bringing specific functional group according to actual needs.
Hence, they have been widely investigated and used for enzyme immobilization.
When it comes to the natural polymer materials, much attention has been paid
to cellulose and other natural polymer materials owing to their wide range of sources,
easy modification, nontoxic, and pollution-free, with a possibility of introducing wide
variety of functional groups and good biocompatible properties.
In this work report the use of synthetic polymer, polypyrrole and its
derivatives and natural polymers coconut fiber and sugarcane bagasse as supports for
Diastase α- amylase immobilization. An attempt was also made to functionalize both
synthetic and natural polymers using Amino-propyl triethoxysilane. Supports and their
immobilized forms were characterized via FT-IR, TG, SEM, XRD, BET and EDS
techniques. Immobilization parameters were also optimized so as to prepare stable
immobilized biocatalyst for starch hydrolysis.
Description:
Department of Applied Chemistry
Cochin University of Science and Technology
Babu,S; Dr.Krishnamoorthy,A(Cochin University of Science and Technology, May , 2007)
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Abstract:
In this thesis we have studied a few models involving self-generation of priorities.
Priority queues have been extensively discussed in literature. However, these are situations involving priority assigned to
(or possessed by) customers at the time of their arrival. Nevertheless, customers
generating into priority is a common phenomena. Such situations especially arise
at a physicians clinic, aircrafts hovering over airport running out of fuel but waiting
for clearance to land and in several communication systems. Quantification of these
are very little seen in literature except for those cited in some of the work indicated
in the introduction. Our attempt is to quantify a few of such problems. In doing
so, we have also generalized the classical priority queues by introducing priority
generation ( going to higher priorities and during waiting). Systematically we have
proceeded from single server queue to multi server queue. We also introduced customers with repeated attempts (retrial) generating
priorities. All models that were analyzed in this thesis involve nonpreemptive
service. Since the models are not analytically tractable, a large number
of numerical illustrations were produced in each chapter to get a feel about the
working of the systems.
Description:
Department of Mathematics,
Cochin University of Science and Technology
Venu, Nair G; Dr.Mohan Kumar, K(Department of Atmospheric Science, 2006)
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Abstract:
The thesis gives a general introduction about the topic include India, the spatial and temporal variation of the surface meteorological parameters are dealt in detail. The general pattern of the winds over the region in different seasons and the generation and movements of the thermally and dynamically originated local wind systems of Western Ghats region has been studied. The modification of the prevailing winds over region by the Palghat Gap and its effect on the mouth regions pf the gap is analysed in great depth. The thesis gives the information of climatic elements of the mountain region such as energy budgets, rainfall studies, evaporation and condensation and the variation in the heat fluxes over the region. The impact of orography is studied in a different approach. The type of hypothetical study gives more insight into the control of mountain on the distribution of meteorological parameter over the study region and helps to quantify the impact of the mountain in varying the weather climate of region. The detailed study of the hydro-meteorological aspects of the main river basins of the region also should be included to the climatic studies for the total understanding of the weather and climate over the region.