arXiv subjects

Sushant Gupta

Publications and source records attributed to Sushant Gupta.

12 recordsLinked to original sources

arXiv2017

Room temperature ferromagnetism in transparent and conducting Mn-doped $SnO_{2}$ thin films

The magnetization as a function of magnetic field showed hysteretic behavior at room temperature. According to the temperature dependence of the magnetization, the Curie temperature $(T_{C})$ is higher than 350 K. Ferromagnetic Mn-doped tin oxide thin films exhibited low electrical resistivity and high optical transmittance in the visible region (400-800 nm). The coexistence of ferromagnetism, high visible transparency and high electrical conductivity in the Mn-doped $SnO_{2}$ films is expected to be a desirable trait for spintronics devices.

cond-mat.mtrl-sci↗

arXiv2016

Swift Heavy Ion Irradiation Induced Modifications in Structural, Microstructural, Electrical and Magnetic Properties of Mn Doped $SnO_{2}$ Thin Films

In this paper, we have presented the impact of swift heavy ion beam irradiation on the structural, microstructural, electrical and magnetic properties of $Sn_{0.9}Mn_{0.1}O_{2}$ thin films. The structural and electrical results have been interpreted by using properties of native or point defects, whereas the magnetic and morphological variations have been explained in terms of conductivity of material. Efforts have been made to summarize the properties of all possible charged and neutral point defects ($V_{Sn}^{4-}$, $Sn_{i}^{4+}$, $V_{O}^{0}$, $O_{i}^{2-}$, $Sn_{O}^{4+}$, $O_{Sn}^{2-}$, $H_{O}^{+}$) and afterwards from the correlation between experimentally-observed and theoretically-calculated results various interesting conclusions have been drawn.

cond-mat.mtrl-sci↗

arXiv2016

Role of Carrier Concentration in Swift Heavy Ion Irradiation Induced Surface Modifications

Highly conducting $SnO_{2}$ thin films were prepared by chemical spray pyrolysis technique. One set of as-deposited films were annealed in air for 2 h at 850$^{o}$C. These as-deposited and annealed films were irradiated using $Au^{9+}$ ions with energy of 120 MeV at different fluences ranging from $1\times10^{11}$ to $3\times10^{13}$ $ions/cm^{2}$. Electrical measurement shows that as-deposited $SnO_{2}$ films are in conducting state with n = $3.164 \times 10^{20}$ $cm^{-3}$ and annealed $SnO_{2}$ films are in insulating state. The amorphized latent tracks are created only above a certain threshold value of $S_{e}$, which directly depends on the free electron concentration (n). The electronic energy loss ($S_{e}$) of 120 MeV $Au^{9+}$ ions in $SnO_{2}$ is greater than the threshold energy loss ($S_{eth}$) required for the latent track formation in annealed $SnO_{2}$ thin film, but is less than $S_{eth}$ required for as-deposited $SnO_{2}$ film. Therefore, the latent tracks are formed in the annealed $SnO_{2}$ film and not in the as-deposited $SnO_{2}$ film. Thermal spike model is used for the calculation of threshold energy loss and radius of melted zone. The possible mechanism of the structural changes and surface microstructure evolutions is briefly discussed in the light of ion's energy relaxation processes and target's conductivity. The atomic force microscopy (AFM) study of films shows that the morphologies of irradiated films are linked with carrier concentration of target materials.

cond-mat.mtrl-sci↗

arXiv2015

Refraction-Based Alternative Explanation for: Bending of Light Near a Star, Gravitational Red/Blue Shift and Black-Hole

In this research-paper, many of the general-relativity-tests such as bending of light near a star and gravitational red/blue shift are explained without general-relativity & even without Newtonian-approach. The authors first raise questions on the validity of both, the Newtonian and the relativistic approach; and then propose a novel alternative-explanation. The new alternative explanation is based on refraction-phenomenon of optics. Estimation of results with new approach are in agreement with known values. Though physics is different, but it is argued that general-relativity based gravitational-bending and refraction based bending have more in common than is generally realized. Also discussed are black-hole and gravitational-lensing in the new perspective of refraction. The new refraction-based theory makes a few new predictions and also suggests a few tests.

physics.gen-ph↗

arXiv2012

Structural/microstructural, optical and electrical investigations of Sb-SnO2 thin films deposited by spray pyrolysis

The structural, optical and electrical properties of spray deposited antimony (Sb) doped tin oxide (SnO2) thin films, prepared from SnCl4 precursor, have been studied as a function of antimony doping concentration. The doping concentration was varied from 0 to 1.5 wt.% of Sb. The analysis of x-ray diffraction patterns revealed that the as deposited doped and undoped tin oxide thin films are pure crystalline tetragonal rutile phase of tin oxide which belongs to the space group P42/mnm (number 136). The surface morphological examination with field emission scanning electron microscopy (FESEM) revealed the fact that the grains are closely packed and pores/voids between the grains are very few. The transmittance spectra for as-deposited films were recorded in the wavelength range of 200 to 1000 nm. The transmittance of the films was observed to increase from 57% to 68% (at 800 nm) on initial addition of Sb (up to [Sb]/[Sn] = 0.5 wt.%) and then it is decreased for higher level of antimony doping ([Sb]/[Sn] > 0.5 wt.%). The sheet resistance of tin oxide films was found to decrease from 48 Ω/sq for undoped films to 8 Ω/sq for antimony doped films.

cond-mat.mtrl-sci↗

arXiv2011

Synthesis and structural/microstructural characteristics of antimony doped tin oxide $(Sn_{1-x}Sb_{x}O_{2-δ})$

Bulk samples of $(Sn_{1-x}Sb_{x}O_{2-δ})$ with x = 0.00, 0.10, 0.20, 0.30 are synthesized by solid-state reaction route. Samples were characterized by X-ray powder diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and UV-Vis spectroscopy. The x-ray diffraction patterns indicate that the gross structure/phase of $(Sn_{1-x}$ $Sb_{x}O_{2-δ})$ do not change with the substitution of antimony (Sb) up to x = 0.30. The surface morphological examination with SEM revealed the fact that the grain size in the antimony doped sample is larger than that of undoped one and hence pores/voids between the grains increase with Sb concentration up to 0.30. TEM image of undoped sample indicates that the $SnO_{2}$ grains have diameters ranging from 25 to 120 nm and most grains are in cubic or spherical shape. As antimony content increases, the nanocubes/spheres are converted into microcubes/spheres. The reflectance of $Sn_{1-x}Sb_{x}O_{2-δ}$ samples increases whereas absorbance of these samples decreases with the increased concentration of antimony (Sb) for the wavelength range 360 - 800 nm. The energy bandgap of Sb doped - $SnO_{2}$ samples were obtained from optical absorption spectra by UV-Vis absorption spectroscopy. Upon increasing the Sb concentration the bandgap of the samples was found to increase from 3.367 eV to 3.558 eV.

cond-mat.mtrl-sci↗

arXiv2011

Flux Pinning by Nano Particles Embedded in Polycrystalline Y-123 Superconductors

Bulk superconductor samples of YBa2Cu3-xZnxO7-δ with x = 0, 0.01, 0.03 are synthesized by solid-state reaction route. The structural characterisation of all samples has been carried out by x-ray-diffraction (XRD) and transmission electron microscopy (TEM) techniques. The x-ray diffraction patterns indicate that the gross structure/phase of YBa2Cu3-xZnxO7-δ do not change with the substitution of Zn up to x=0.03. In TEM investigations of Zn-doped Y-based cuprates a number of ZnO nano-flower and nano-rod of Y-211 phase are found dispersed in regular YBa2Cu3-xZnxO7 matrix. These dispersed nano-flowers of ZnO and nano-rods of Y-211 phase may serve as flux-pinning centers. These pinning centers enhance critical current density (Jc) value of these HTSC samples.

cond-mat.supr-con↗

arXiv2011

Microstructural and Superconducting Properties of YBa_2Cu_{3-x}Co_xO_{7-δ} System

Bulk superconductor samples of YBa2Cu3-xCoxO7-δ with x = 0, 0.01, 0.03, 0.05 are synthesized by solid-state reaction route. Both x-ray diffraction and electron microscopy have been employed to study the phase identification, intergrowths, dislocations and the local structure of these samples. Transition temperature of the samples has been determined by four probe resistivity measurements. The x-ray diffraction patterns indicate that the gross structure/ phase of YBa2Cu3-xCoxO7-δ do not change with the substitution of Co up to x=0.05. The zero resistance critical transition temperature [Tc(R=0)] is found to decrease and critical current density (Jc) increases with the increased concentration of cobalt in the compound. The Jc enhancement for the cobalt doped samples may be resulting due to flux pinning from some defects such as planar defects, stacking faults and micro defects (twin, domains etc.) and the rapid suppression in Tc may be due to the cooper pair breaking and the hole filling in the CuO2 planes.

cond-mat.supr-con↗

arXiv2010

Redefining Heat and Work in the Right Perspective of Second-law-of-Thermodynamics

There are some misnomers and misconceptions about what is heat and what is work; the recognition of heat and work is even more difficult when it comes to categorize energy as heat or work. Since both heat and work are energy the name-confusion does not make much difference from engineering point of view, but re-defining `heat' and `work' in the right-perspective of second-law-of-thermodynamics \cite {ref1} is necessary to revise our understanding at fundamental level. It is concluded that `heat is the energy carried by mass-less \textit{photons} whereas work is energy carried by mass-ive material \textit{fermions}'. Revised understanding of heat and work in this way has far reaching consequences in Physics [2-4]. The present paper lays emphasis on re-defining heat and work, removing the prevailing misconception, talks about single photon interaction and heat property of photon. Also, interestingly, it is noted that different fields of study such as `Thermodynamics' and `Relativity' are interlinked.

physics.gen-ph↗

arXiv2010

A Novel Concept for Mass as Complex-Mass towards Wave-particle Duality

In the present paper a new concept is introduced that: `mass is a complex quantity'. The concept of complex-mass suggests that the total mass M of a moving body is complex sum of: (i) the real-part (grain or rest) mass $m_{g}$ establishing its particle behaviour and (ii) the imaginary-part mass $m_{p}$ governing its wave properties. Mathematically, the complex mass $M = m_{g} + im_{p}$; the magnitude $\mid M \mid = (m_{g}^{2} + m_{p}^{2})^{1/2}. The theory proposed here explains successfully several effects such as `Compton effect' and `refraction of light' which could not be explained otherwise by a single theory of wave or particle. Also explained are `Doppler effect for light', `photo-electric effect', `Uncertainty principle', `Relativity' and `supersymmetry'

physics.gen-ph↗

arXiv2009

`Zero-spin-photon hypothesis' finds another important application: Could possibly solve the `infinity-problem' of QED without the need of renormalization

`Zero-spin-photon hypothesis' as proposed in an earlier paper [1] states that: `due to inevitable consequence of the second-law of thermodynamics and spin-conservation, the `zero-spin-photon' is generated in pair-production process (of elementary particles), which decays into neutrino and antineutrino'. The zero-spin photon hypothesis explains [1] several riddles of physics and universe. In the present paper, it is shown that `the zero-spin photon hypothesis' when incorporated into the higer-order Feynman diagram (with a closed-loop) could possibly solve the half-a-century-old and famous `infinity-problem' of QED, and thus could avoid the need of the so called `re-normalization' procedure.

physics.gen-ph↗

arXiv2009

Zero-spin-photon hypothesis: `Zero-spin-photon generation in pair-production and its subsequent decay into neutrino and antineutrino' - solves many-riddles of physics and universe

`What is work and what is heat' is re-investigated from the perspective of second law of thermodynamics. It is shown that the inevitable consequence of second law of thermodynamics and spin conservation necessitates the possible generation of zero spin photon in pair production process, and its subsequent decay explains the birth of neutrino and antineutrino. The proposed neutrino-genesis, solves many riddles of physics and universe. The riddles considered and explained are about: (i) mysterious neutrino (and antineutrino) and its bizarre properties such as handed-ness and parity-violation, (ii) questionable asymmetry/ excess of matter over antimatter, (iii) possibility of existence of antimatter world and (iv) parity (P) violation and aspects of CP and CPT violation or restoration in the universe.

physics.gen-ph↗