Kunjomana, A G; Dr.Elizabeth, Mathai(Cochin University Of Science And Technology, August 10, 1992)
[+]
[-]
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)
[+]
[-]
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)
[+]
[-]
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)
[+]
[-]
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)
[+]
[-]
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)
[+]
[-]
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)
[+]
[-]
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.
Nelson, Rodrigues; Dr. Jacob, Philip(Cochin University of Science and Technology, March , 1997)
[+]
[-]
Abstract:
The dielectric and elastic properties are of considerable significance to the science and
technology of matter in the solid state. The study of these properties give information
about the magnitude of the forces and nature of the bonding between the atoms. Our
aim has been to investigate systematically the effect of doping of an appropriate element
on the elastic and dielectric properties of selected dielectric ceramics and oxide glasses.
These materials have got wide technological applications due to their interesting electrical, optical, thermal and elastic behaviour. Ultrasound propagation and capacitance
measurement techniques have been employed for the systematic investigation of the
elastic and dielectric properties of selected number of these materials. Details of the
work done and results obtained are presented in this thesis.
Description:
Department of Physics, Cochin
University of Science and Technology
Rachel, Reena Philip; Dr.Pradeep, B(Cochin University of Science And Technology, December , 2004)
[+]
[-]
Abstract:
Investigations on thin films that started decades back due to scientific curiosity in the
properties of a two-dimensional solid, has developed into a leading research field in
recent years due to the ever expanding applications of the thin films in the fann of a
variety of active and passive microminiaturized components and devices, solar cells,
radiation sowces and detectors, magnetic memory devices, interference filters,
refection and antireflection coatings etc. [1]. The recent environment and energy
resource concerns have aroused an enonnous interest in the study of materials in thin
film form suitable for renewable energy sources such as photovoltaic devices.
Recognition of the immense potential applications of the chalcopyrites that can fonn
homojunctions or heterojunctions for solar cell fabrication has attracted many
researchers to extensive and intense research on them.
In this thesis, we have started with studies performed on CuInSe, thin films, a
technologically well recognized compound belonging to the l•ill-VI family of
semiconductors and have riveted on investigations on the preparation and
characterization of compoWlds Culn3Se5. Culn5Seg and CuIn7Se12, an interesting group
of compounds related to CuInSe2 called Ordered Vacancy Compounds, having
promising applications in photovoltaic devices. A pioneering work attempted on
preparing and characterizing the compound Culn7Sel2 is detailed in the chapters on
OVC's. Investigation on valence band splitting in avc's have also been attempted for
the first time and included as the last chapter in the thesis. Some of the salient features
of the chalcopyrite c.ompounds are given in the next section .of this introductory
chapter.
Description:
Department of Physics, Cochin University of Science And Technology,