G. B. V. S. Lakshmi

Synthesis, Electrical Conductivity, and Dielectric Behavior of Polyaniline/V2O5 Composites

Conducting polymer composites of polyaniline/vanadium pentaoxide PANI/V2O5 (with different initial weight percentage of V2O5) has been synthesized by in situ polymerization method. DC conductivity of compressed pellets has been analyzed in the temperature range 300–550 K and was found to increase with V2O5 doping. This increase in conductivity is mainly due to band conduction. It has also been observed that the dielectric constant and dielectric loss increase with the level of doping of V2O5 but remain independent of the frequency (50 KHz–1 MHz). X-ray diffraction pattern shows some order of crystallinity of composites due to interaction of polyaniline with V2O5. UV-visible spectroscopy shows an increase in the optical band gap with doping.

Development of a large area two-dimensional position sensitive ΔE−E detector telescope for material analysis

A large area two-dimensional position sensitive detector telescope has been designed and fabricated at NSC, New Delhi for performing ERDA based material characterization experiments. This gas ionization detector is working well with position resolution better than 2 mm and good z-separation in both high and low mass regions. Large solid angle is a pre-request to minimize the possible unwanted radiation damage during the measurement. The consequent kinematic broadening has been corrected by recording the position information. Two-dimensional position sensitivity has also been obtained. Possibility of controlled modification is shown in this work.

Electronic sputtering from HOPG: A study of angular dependence

The angular distribution of the sputtering yield from highly oriented pyrolytic graphite sample irradiated with a 130 MeV Ag beam is studied. The beam was incident perpendicular to the sample and the sputtered carbon was collected on Si catcher foils which were studied using a high resolution ERDA set up. An anisotropic distribution of sputtering is observed with a distribution C ¼ A cos 1:3 H þ B expð�ð H � 53Þ 2 =r 2 ) which shows that a peak lies at around 53� on a distribution which otherwise is a over-cosine function. The maximum sputtering yield is observed at 53� , falling rapidly to almost zero at 90� , with an average sputter yield of 5.5 · 10 5 atoms/ion. It is suggested that this

Ion beam studies in strained layer superlattices

Abstract The potential device application of semiconductor heterostructures and strained layer superlattices has been highlighted. Metal organic chemical vapour deposition grown In 0.53 Ga 0.47 As/InP lattice-matched structure has been irradiated by 130 MeV Ag 13+ and studied by RBS/Channelling using 3.5 MeV He 2+ ions. Ion irradiation seems to have induced a finite tensile strain in the InGaAs layer, indicating thereby that ion beam mixing occurs at this energy. Other complementary techniques like high resolution XRD and STM are needed to conclude the structural modifications in the sample.

Structural and optical modification in 4H-SiC following 30 keV silver ion irradiation

The market of high power, high frequency and high temperature based electronic devices is captured by SiC due to its superior properties like high thermal conductivity and high sublimation temperature and also due to the limitation of silicon based electronics in this area. There is a need to investigate effect of ion irradiation on SiC due to its application in outer space as outer space is surrounded both by low and high energy ion irradiations. In this work, effect of low energy ion irradiation on structural and optical property of 4H-SiC is investigated. ATR-FTIR is used to study structural modification and UV-Visible spectroscopy is used to study optical modifications in 4H-SiC following 30 keV Ag ion irradiation. FTIR showed decrease in bond density of SiC along the ion path (track) due to the creation of point defects. UV-Visible absorption spectra showed decrease in optical band gap from 3.26 eV to 2.9 eV. The study showed degradation of SiC crystallity and change in optical band gap following low energy ion irradiation and should be addressed while fabricationg devices based on SiC for outer space application. Additionally, this study provides a platform for introducing structural and optical modification in 4H-SiC using ion beam technology in a controlled manner.The market of high power, high frequency and high temperature based electronic devices is captured by SiC due to its superior properties like high thermal conductivity and high sublimation temperature and also due to the limitation of silicon based electronics in this area. There is a need to investigate effect of ion irradiation on SiC due to its application in outer space as outer space is surrounded both by low and high energy ion irradiations. In this work, effect of low energy ion irradiation on structural and optical property of 4H-SiC is investigated. ATR-FTIR is used to study structural modification and UV-Visible spectroscopy is used to study optical modifications in 4H-SiC following 30 keV Ag ion irradiation. FTIR showed decrease in bond density of SiC along the ion path (track) due to the creation of point defects. UV-Visible absorption spectra showed decrease in optical band gap from 3.26 eV to 2.9 eV. The study showed degradation of SiC crystallity and change in optical band gap following low...

Engineering the Optical Properties of insitu Polymerized poly (o-toluidine/V2O5) Composites

Conducting polymer composites of poly (o-toluidine)/vanadium pentoxide (POT/V2O5) were synthesized by polymerization of o-toluidine with V2O5 using (NH4)2 S2O8) as an oxidant. The optical properties as photoluminescence, UV–visible absorption, optical band gap, UV–visible reflection and refractive index are studied. The optical band gap of composites found to decrease with increase in the weight percent of V2O5 and the PL intensity has been found to increase with V2O5. From UV–visible absorption and reflection studies, the dielectric constant has been estimated and found to increase with V2O5. The PL emission intensity of all the polymer/V2O5 composites makes them suitable for various optoelectronic devices.

Automation of Channeling Experiment for Lattice Strain Measurements Using High Energy Ion Beams

40 MeV Si channeling studies have been performed on the strained In0.1Ga0.9As layer grown on GaAs substrate using Molecular Beam Epitaxy (MBE). Three samples with different layer thickness have been investigated in this study. Channeling experiment has been fully automated so as to minimize the radiation damage. Suitable software and hardware have been developed to control the precision goniometer using the CAMAC (Computer automation and control) based data acquisition system. In low energy He channeling, strain measurements are often misled by the beam steering effects caused due to broad critical angles if the strain is very low. Such effects can be minimized by increasing the probing beam energy as the channeling critical angle is inversely proportional to the square root of the incident energy. Hence small angular misalignments can also be resolved in the high energy channeling experiments. Heavy ions are chosen so as to have reasonably high scattering cross‐section and also to avoid the nuclear react...