Photoacoustic investigation of the optical and thermal properties of selected amorphous chalcogenide semiconductors

This thesis work has mainly concentrated on the investigation of the ,optical and thermal properties of binary semiconducting chalcogenide glasses belonging to the AivB¥5x and AZBXEX families. The technique used for these studies is a relatively new one namely, the photoacoustic (PA) technique. This technique is based on the detection of acoustic signal produced in an enclosed volume when the sample is irradiated by an intensity modulated radiation. The signal produced depends upon the optical properties of the sample, and the thermal properties of the sample, backing material and the surrounding gas. For the present studies an efficient signal beam gas-microphone PA spectrometer, consisting of a high power Xenon lamp, monochromator, light beam chopper, PA cell with microphone and lock-in amplifier, has been set up. Two PA cells have been fabricated: one for room temperature measurements and another for measurements at high temperatures. With the high temperature PA cell measurements can be taken upto 250°C. Provisions are incorporated. in both the cells to change the volume and to use different backing materials for the sample. The cells have been calibrated by measuring the frequency response of the cells using carbon black as the sample

Studies On The Effect Of Laser Radiation And Other Mutagens On Plants

The effect of lasers of three wavelengths in the visible region - 476, 488 and 514 nm on mitotic and meiotic cell divisions, growth, yield and activity of specific enzymes were studied in two taxonomically diverse plant species — A/lium cepa L. and Vicia faba. The effect of laser exposures was compared with the effect of two physical mutagens (Gamma and Ultraviolet radiations) and two chemical mutagens (Ethyl Methane Sulphonate and Hydroxyl amine). The study indicated that lasers could be mutagenic causing aberration in the mitotic and meiotic cell divisions while also producing changes in the growth and yield of the plants. Lasers of higher wavelengths 488 and 514 nm caused aberrations in the early stages of mitotic cell division whereas lasers of lower wavelengths (476 nm) caused more aberrations in the later stages of mitotic cell division. Laser exposure of 488 nm wavelength at power density 400 mW induced higher mitotic and meiotic aberrations and also induced higher pollen sterility than lasers of 476 and 514 nm. The frequency of mitotic aberrations induced by lasers was lesser than that caused by y-irradiation but comparable to that induced by EMS and HA. Lasers cause mutations in higher frequencies than UV. Lasers had a stimulatory effect on growth and yield in both plant species. This stimulatory effect of lasers on germination could not however be correlated to the activity of amylase and protease, the key enzymes in seed gennination. Enzymes such as peroxidase and catalase, involved in scavenging of free oxygen radicals often produced by irradiation, did not show increased activity in laser irradiated samples. Further studies are required for elucidating the exact mechanisms by which lasers cause mutations

Mini-trawls for Estuarine Fishing Kasargod District

Mi ni -trawls are operated by the artisanal fishermen from small wooden non-motorised canoes. Shrimp, fish and crab trawls wi th head rope length rang ing from 3.5-8 m, made of Po lyethy lene mon ofila ment (PE) twisted and Polyamide mullifilament (PA) rigged to 6-7 kll fla t rectangular wooden otter boards are common in the lower reaches of Kariango de and Chandrag iri rive rs. Since the trawling speed is less, ca tch is do minated by crus taceans. Less scope ratio also may be affecting the catching efficiency of the gear. This pape r deals with the design, operation and economics of mini traw ling carried out by a group of fisherme n in the above rivers of Kasargod district Kerala state.

Swift heavy ion induced surface modification for tailoring coercivity in Fe–Ni based amorphous thin films

Fe–Ni based amorphous thin films were prepared by thermal evaporation. These films were irradiated by 108 MeV Ag8+ ions at room temperature with fluences ranging from 1 1012 to 3 1013 ions/cm2 using a 15 UD Pelletron accelerator. Glancing angle x-ray diffraction studies showed that the irradiated films retain their amorphous nature. The topographical evolution of the films under swift heavy ion SHI bombardment was probed using atomic force microscope and it was noticed that surface roughening was taking place with ion beam irradiation. Magnetic measurements using a vibrating sample magnetometer showed that the coercivity of the films increases with an increase in the ion fluence. The observed coercivity changes are correlated with topographical evolution of the films under SHI irradiation. The ability to modify the magnetic properties via SHI irradiation could be utilized for applications in thin film magnetism

Photoluminescence studies on RF plasma-polymerized thin films

Conjugated polymers in the form of thin films play an important role in the field of materials science due to their interesting properties. Polymer thin films find extensive applications in the fabrication of devices, such as light emitting devices, rechargeable batteries, super capacitors, and are used as intermetallic dielectrics and EMI shieldings. Polymer thin films prepared by plasma-polymerization are highly cross-linked, pinhole free, and their permittivity lie in the ultra low k-regime. Electronic and photonic applications of plasma-polymerized thin films attracted the attention of various researchers. Modification of polymer thin films by swift heavy ions is well established and ion irradiation of polymers can induce irreversible changes in their structural, electrical, and optical properties. Polyaniline and polyfurfural thin films prepared by RF plasmapolymerization were irradiated with 92MeV silicon ions for various fluences of 1×1011 ions cm−2, 1×1012 ions cm−2, and 1×1013 ions cm−2. FTIR have been recorded on the pristine and silicon ion irradiated polymer thin films for structural evaluation. Photoluminescence (PL) spectra were recorded for RF plasma-polymerized thin film samples before and after irradiation. In this paper the effect of swift heavy ions on the structural and photoluminescence spectra of plasma-polymerized thin films are investigated.

Swift heavy ion induced surface and microstructural evolution in metallic glass thin films

Swift heavy ion induced changes in microstructure and surface morphology of vapor deposited Fe–Ni based metallic glass thin films have been investigated by using atomic force microscopy, X-ray diffraction and transmission electron microscopy. Ion beam irradiation was carried out at room temperature with 103 MeV Au9+ beam with fluences ranging from 3 1011 to 3 1013 ions/cm2. The atomic force microscopy images were subjected to power spectral density analysis and roughness analysis using an image analysis software. Clusters were found in the image of as-deposited samples, which indicates that the film growth is dominated by the island growth mode. As-deposited films were amorphous as evidenced from X-ray diffraction; however, high resolution transmission electron microscopy measurements revealed a short range atomic order in the samples with crystallites of size around 3 nm embedded in an amorphous matrix. X-ray diffraction pattern of the as-deposited films after irradiation does not show any appreciable changes, indicating that the passage of swift heavy ions stabilizes the short range atomic ordering, or even creates further amorphization. The crystallinity of the as-deposited Fe–Ni based films was improved by thermal annealing, and diffraction results indicated that ion beam irradiation on annealed samples results in grain fragmentation. On bombarding annealed films, the surface roughness of the films decreased initially, then, at higher fluences it increased. The observed change in surface morphology of the irradiated films is attributed to the interplay between ion induced sputtering, volume diffusion and surface diffusion

Unusual surface and edge morphologies, sp2 to sp3 hybridized transformation and electronic damage after Ar+ ion irradiation of few-layer graphene surfaces

Roughness and defects induced on few-layer graphene (FLG) irradiated by Ar+ ions at different energies were investigated using X-ray photoemission spectroscopy (XPS) and atomic force microscopy techniques. The results provide direct experimental evidence of ripple formation, sp2 to sp3 hybridized carbon transformation, electronic damage, Ar+ implantation, unusual defects and edge reconstructions in FLG, which depend on the irradiation energy. In addition, shadowing effects similar to those found in oblique-angle growth of thin films were seen. Reliable quantification of the transition from the sp2-bonding to sp3-hybridized state as a result of Ar+ ion irradiation is achieved from the deconvolution of the XPS C (1s) peak. Although the ion irradiation effect is demonstrated through the shape of the derivative of the Auger transition C KVV spectra, we show that the D parameter values obtained from these spectra which are normally used in the literature fail to account for the sp2 to sp3 hybridization transition. In contrast to what is known, it is revealed that using ion irradiation at large FLG sample tilt angles can lead to edge reconstructions. Furthermore, FLG irradiation by low energy of 0.25 keV can be a plausible way of peeling graphene layers without the need of Joule heating reported previously

Magnetic and topographical modifications of amorphous Co–Fe thin films induced by high energy Ag7+ ion irradiation

We have investigated the effects of swift heavy ion irradiation on thermally evaporated 44 nm thick, amorphous Co77Fe23 thin films on silicon substrates using 100 MeV Ag7+ ions fluences of 1 1011 ions/ cm2, 1 1012 ions/cm2, 1 1013 ions/cm2, and 3 1013 ions/cm2. The structural modifications upon swift heavy irradiation were investigated using glancing angle X-ray diffraction. The surface morphological evolution of thin film with irradiation was studied using Atomic Force Microscopy. Power spectral density analysis was used to correlate the roughness variation with structural modifications investigated using X-ray diffraction. Magnetic measurements were carried out using vibrating sample magnetometry and the observed variation in coercivity of the irradiated films is explained on the basis of stress relaxation. Magnetic force microscopy images are subjected to analysis using the scanning probe image processor software. These results are in agreement with the results obtained using vibrating sample magnetometry. The magnetic and structural properties are correlated