arXiv subjects

Chhaya Ravi Kant

Publications and source records attributed to Chhaya Ravi Kant.

7 recordsLinked to original sources

arXiv2013

Contribution of Halides in CsX (X=Cl, Br and I) Thin Films on the formation of SPR peaks

This manuscript describes the evolution of grain structures in Cesium Halide films which results in appearance of Surface Plasmon Resonance (SPR) peaks in UV-visible absorption spectra. Thin films of Cesium Halide grown by thermal evaporation are polycrystalline in nature with large irregular tightly packed grains with sharp grain boundaries. With time these grain boundaries recede to become smaller and spherical in shape in order to minimize the free surface energy of the system. The process is also assisted by the presence of point defects/color centers in Cesium Halide films. These defects which appear due to the absence of massive halide atoms from the lattice results in residual tensile stress within the lattice which results in defect diffusion. The defects migrate outwards towards the grain surface giving rise to Cesium metal clusters. The lattice mismatch appearing between the lattices at the grain boundary and the bulk giving rise to Core-shell structure further contributes to grain division. Along with this volume diffusion, a surface diffusion of Cesium takes place towards sites of faceted grain boundaries resulting in a necking phenomenon, appearing like bridges between the daughter Cesium Halide grains (grains appearing due to division of a single grain). Breaking away of the daughter Cesium Halide grains results in nano-rods that contribute to the SPR peak seen.

cond-mat.mtrl-sci↗

arXiv2011

Metal Cluster's Effect on the Optical Properties of Cesium Bromide Thin Films

Cesium Bromide films grown of glass substrates by thermal evaporation showed interesting optical properties. The UV-visible absorption spectra showed peaks which showed red shift with time. Structural and morphological studies suggested decrease in grain size with time which was unusual. Theoretical simulation shows the optical behaviour to be due to surface plasmon resonance resulting from Cesium clyindrical rods embedded in the films.

cond-mat.mtrl-sci↗

arXiv2011

Film Thickness controlled photoluminescence Emission in ZnO:Si Nano-composites

As grown ZnO:Si nanocomposite films fabricated by thermal evaporation showed broad photoluiminescence (PL) spectra due to merging of four prominent peaks viz 370, 410, 470 and 520 nm. Investigations revealed the role of interface in contributing to the two blue peaks at 410 and 470 nm. While the 470 nm is found to vary with ZnO grain size and their density, the 410 nm peak is attributed to the volume of shell surrounding ZnO nanoparticles. This study shows the contribution of ZnO cluster size and their density, as influenced by film thickness, in the PL spectra of the samples.

cond-mat.mtrl-sci↗

arXiv2011

White-Light Emission from Annealed ZnO:Si Nanocomposite Thin Films

As grown ZnO:Si nanocomposites of different compositional ratios were fabricated by thermal evaporation techniques. These films were subjected to post deposition annealing under high vacuum at a temperature of $\rm 250C^o$ for 90min. The photoluminescence (PL) spectra of annealed samples have shown marked improvements both in terms of intensity and broadening. For the first time in ZnO:Si nanocomposite films we see huge UV, red and orange peaks at 310, 570 and 640nm. Structural and Raman analysis show formation of a Zn-Si-O shell around ZnO nano clusters wherein on heating $\rm Zn_2SiO_4$ compound forms. The new emissions are due to $\rm Zn_2SiO_4$ which completes white light spectrum.

cond-mat.mtrl-sci↗

arXiv2010

Size and Defect related Broadening of Photoluminescence Spectra in ZnO:Si Nanocomposite Films

Nanocomposite films of Zinc Oxide and Silicon were grown by thermal evaporation technique using varying ratios of ZnO:Si in the starting material. Analysis reveal the role of ZnO and amorphous silicon interface in contributing to relatively less common blue photoluminescence emissions (at $\sim$ 400 and 470nm). These blue peaks are observed along with the emissions resulting from band edge transition (370nm) and those related to defects (522nm) of ZnO. Careful analysis shows that along with the grain size of ZnO, a suitable compositional ratio (of ZnO to silicon) is critical for the coexistence of all the four peaks. Proper selection of conditions can give comparable photoluminescence peak intensities leading to broad-band emission.

cond-mat.mtrl-sci↗

arXiv2007

Characterization of ZnO:Si Nanocomposite Films Grown by Thermal Evaporation

Nanocomposite thin films of Zinc Oxide and Silicon were grown by co-evaporating powdered ZnO and Si. This resulted in nanocrystallites of ZnO being embedded in Silicon. The mismatch in crystal structures of constituent materials result in the ZnO nanocrystals to exist in a state of stress. This along with oxygen vacancies in the samples result in good Photoluminescence emission at 520nm. Also, Silicon background gave a photoluminescence emission at 620nm. The structure was found quite stable over time since the homgenously dispersed ZnO nanocrystals do not agglomerate. The nanocomposites promises to be a useful candidate for future optoelectronic devices.

cond-mat.mtrl-sci↗

arXiv2006

Modeling, Performance Analysis and Comparison of Two Level Single Chain Pointer Forwarding Strategy For Location Management in Wireless Mobile Communication

Global wireless networks enable mobile users to communicate regardless of their locations. Location management is an important part of the emerging wireless and mobile technology. A Personal Communication System (PCS) network must have an efficient way to keep track of the mobile users to deliver services effectively. Global System for Mobile Communication (GSM) is a commonly accepted standard for mobility management of mobile users. Location management involves location tracking, and location information storage. Location management requires mobile users to register at various registration areas whenever they are on the move. The registration process may cause excessive signaling traffic and long service delays. To improve the efficiency of location tracking and avoid call set up delays, several strategies such as local anchor scheme, per-user caching scheme and several pointer forwarding schemes have been proposed in the past. In this paper, we propose a new "Two Level Single Chain Pointer Forwarding (TLSCP) Strategy" in which a two level hierarchy of level-1 and level-2 forwarding pointers reduced to single chain length are used. Organizing the pointers in a two level hierarchy and further restricting the pointer chain lengths at both the levels to single chain localizes the network signaling traffic and reduces the call set up delays. To justify the effectiveness of our proposed strategy, we develop an analytical model to evaluate the signaling cost. Our performance analysis shows that the proposed dynamic TLSCP scheme can significantly reduce the network signaling traffic and cost for different categories of users under different network conditions.

physics.data-an↗