Department of Physics

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Synthesis, Crystal Growth And Characterization Of Dmapnp Crystals For NLO Applications
(Department of Physics, NITS, 2022) Lenka, Chandan Kumar
Crystals are beautiful creation of nature that attract us human beings since ancient times. We always try to grow crystals artificially in laboratories. The foundation work on different crystallization techniques has already been deduced in 18th and 19th century but it gets a great stimulation after invention of laser and by we get a new field in optics known as non linear optics which can solve many problems in today’s world. Non-linear optics originates after witnessing the doubling of frequency by applying a laser for the first time. However, now, it has a very high demand for photonics. NLO materials have the properties to gain, preserve, process, and transfer data as semiconductors work. However, we use light here, which increases the transfer speed or other workings. For this reason, the demand for NLO materials increases in telecommunication, optical switching, optical computing, extensive data storing and many other things. This necessitates the search for new NLO materials with distinct properties to meet our requirements. The compound is classified as organic, inorganic, semi-organic, or organometallic in this search. We are primarily interested in the organic substance 4-dimethylamino pyridinium 4-nitrophenol (DMAPNP), which was generated using the slow cooling technique of crystal development. The formed crystal is next examined with powdered XRD to determine the lattice characteristics. The crystal is then subjected to FTIR and FT-Raman spectroscopy to determine the functional group present, as well as vibrational mode analysis. After that, we can see its transparency in the UV-Visible portion of the electromagnetic spectrum by utilizing the UV-Vis absorption spectrum. Finally, the efficiency of the produced material for SHG or its optical nonlinearity is determined by characterizing the crystal for SHG using the Kurtz-Perry powder technique.
Semileptonic B-meson decays in the Standard Model
(Department of Physics, NITS, 2022) Barman, Nayan Moni
Our current understanding of the laws of nature that govern the fundamental constituents of the Universe, the elementary particles and their interactions are well established within a model called the standard model of particle physics. The standard model of particle physics provides a systematic description of the known fundamental forces of nature and classifies all known elementary particles. The underlying frame work of the standard model assumes that the charged and neutral leptons are universal in weak interactions. In particular, the photon, the W± and Z boson couple in exactly the same manner to the three lepton generations. However, in recent years, several hints for the lepton flavor universality violation have been reported in various charged current b → cℓν and neutral-current b → sℓℓ quark level transitions. In particular, the experimental measurements of RD, RD∗, PD∗ τ , and FD∗ L in B→(D,D∗)ℓν decays and RJ/Ψ in Bc → J/Ψℓν decays proceeding via b → cℓν quark level transition deviate from standard model expectations at 1.4σ, 2.5σ, 1.6σ, 1.5σ, and 1.8σ, respectively. In this report, we perform a detailed standard model analysis of various semileptonic B-meson decays such as B → Dℓν, B → D∗ℓν, and Bc → J/Ψℓν proceeding via b → cℓν quark level transition. The primary concern of this work is to study the standard model flavor structure of semileptonic B-meson decays proceeding via charged-current b → cℓν quark level transition. In our analysis, we give predictions of several observables, such as the differential branching ratio DBR, the ratio of branching ratios R(P,V), the lepton side forward-backward asymmetry Aℓ FB, the longitudinal polarization fraction of the charged lepton Pℓ, and the longitudinal polarization fraction of the vector meson FV L in standard model using the effective field theory formalism.
Study of Rietveld refinement of a ferroelectric material
(Department of Physics, NITS, 2022) B. K, Keerthana
The main purpose of my project is to refine selected parameters to minimize the difference between an experimental pattern and a model based on the hypothesized crystal structure and instrumental parameters. It includes full-profile fitting (non-linear curve fitting), using crystallographic constraints consisting of lattice parameters and space group to constrain peak positions, crystal structure to constrain peak intensities. Goodness of fit is measured by χ2. Multiple data sets are used to get extra information about the sample. The main thing is to use constraints to handle come complex structures. P 21 21 2 is considered as our space group and ended with the least possible χ2 value I could get. The refinable parameters include scale factor, FWHM parameters, atomic positions, structural parameters, Occupancy parameters. It concludes with the perovskite structure of the sample.
Role of Iron (Fe) dopant concentration on titania phase transformation and photocatalytic performance
(Department of Physics, NITS, 2022) Nair, Gopika Rajeev
The technological and industrial progress achieved by the humankind has come at a cost of the environment. Uncontrolled expansion of industry is destroying the fragile ecology and polluting the environment. Among the different environmental pollutions, water pollution needs special attention since water is an indispensable part of human life. Water pollution not only lead to physiological issues in human body, but also affect the entire livelihood of the affected area. Among the different water pollutants, Emerging Contaminates deserves special attention. These organic pollutants are usually found in wastewater discharged from industries. These contaminants have far reaching consequences in the environment. There are many methods for treating the wastewater containing the pollutants. The conventional methods are expensive, less effective and may use energy source to carry out the process which will mostly non-renewable source of energy. A class of wastewater treatment method known as advanced oxidation process (AOP) shows to be promising. Although still at lab scale, this emerging method is considered to superior in many aspects while compared to the conventional method. AOP’s includes the formation hydroxyl species which then mineralize the organic pollutants by oxidising them. Thus, AOP does not produce any harmful by-products. Among the different AOP methods, photocatalysis is receiving wide attention. This is due to the its cost effective nature, non-lethal procedure and its ability to utilize the solar energy. The hydroxyl radicals are produced when solar light is irradiated on the photocatalytic surface causing charge carrier separation. Semiconductor metal oxides such as TiO2, ZnO, Fe2O3 etc are widely used photocatalysts. Among them TiO2(titania) is the most preferred photocatalyst due its non-toxic nature, high stability better electron transport. But the wide bandgap (3.2 eV for anatase) restricts performance of titania to UV region of solar spectra and also higher probability of charge carrier recombination further limits its performance. Various methods have been adopted to overcome the limitations of titania such doping, forming heterojunction, sensitizing it with noble metals etc. Among these doping with metals/non-metals is one of the widely used strategy. Doping with metal/nonmetals causes a shift in the conduction/valence band causing a decrease in the bandgap and facilitating the visible light absorption. Moreover, it is observed that existence of titania as a mixed phase(anatase-rutile) rather than single has shown better photocatalytic performance due to better charge carrier separation and transportation property. Considering this the present study aims to synthesis metal doped (Iron-Fe) mixed phase titania and test its photocatlytic performance. Sol-gel route was used as the synthesis method. X-ray diffraction, UV-Vis spectroscopy and photoluminescence spectroscopy studies of the samples were carried out to study the structural and optical properties. Incorporation of Fe initiates a phase transformation from rutile to anatase. Samples with different anatase-rutile(A/R) ratio were obtained by varying the Fe dopant concentration. It is further observed that the dopant concentration also affected the PL intensity. At higher dopant concentration low PL intensity was observed indicating interaction between the dopant ion causing non radiative recombination. Finally, solar photocatalytic activity test was carried out using methylene blue as the probe pollutant. Photocatalytic activity was found to decrease with increase in doping. Also, sample calcined at 4000C and having a dopant concentration of 0.1% of Fe showed highest performance. This can be attributed to the optimum level doping due to which trap centres were created which prevents charge carrier recombination. The superior performance can also be attributed to the optimum A/R ratio(A>R) which facilitates better charge carrier separation and charge transport.
Investigation on synthesis, growth and dielectric properties of dimethyle aminopyridinium 4-nitrophenolate 4-nitrophenol for non linear optical application
(Department of Physics, NITS, 2022) Saha, Debjani
For a pretty long time, man has appreciated crystals and cherished their beauty. Mother Earth's gifts of gems and crystals have long piqued human interest, and belief in the healing properties of jewels and minerals stretches back at least two thousand years. The use of stones as ornaments appears to have been practised from the dawn of time. Crystals are now the foundations of modern technology. There would be no electronics industry, no photonics industry, no fibre-optic communications, very little contemporary optical equipment, and some significant production engineering gaps without crystals. There has been a rising interest in crystal formation processes in recent decades, especially in light of the increasing demand for materials for technological applications. So it is very important for us to know about crystals and their application. Keeping it in my, in this paper, an overview of crystal growth, synthesis, and a brief description over some of the important characteristics of a single crystal named Dimethyl amino pyridinium 4-nitrophenolate 4-nitrophenol are given. While studying its characterization we will also encounter the importance of NLO in today’s world and possibilities for tomorrow. By doing second harmonic studies, it will be shown here that the sample single crystal shows nonlinear optical properties.
Fabrication and Characterization of Cu/RbPbI3/ITO/ Glass Heterostructure
(Department of Physics, NITS, 2022) Ota, Subhrakant
Due to versatility in thin-film deposition techniques, the exploitation of a deposition process is beneficial for designing a device for a suitable application. Thin-film deposition process by the method of sputtering helps in smooth deposition of thin films. Literature survey has shown the advantages of RF sputtering over DC sputtering in terms of film quality and ease of deposition of various kind of materials. In this project we sputtered ITO over glass using RF sputtering method and studied its optical and electrical properties. We know that with the advancement in technology, the aim for data security has also increased. The writing ability of modern memory devices has proved their incompetence in the permanent storage of confidential data. Halide perovskite-based memory devices have been actively researched for resistive switching memory applications because of their excellent electronic properties. As pure RbPbI3 is non-switchable, we looked for the WORM nature exhibited by this functional material after depositing over annealed sputtered ITO. We observed that due to the low resistance of ITO at 3000C the device showed its WORM nature having a decent OFF to ON ratio of 104. The device showed great prospects for data storage and provided scope for further investigations.
Structural, Electronic, And Optical Properties Of γ- Rbgei3 Through DFT Analysis For Photovoltaic Application
(Department of Physics, NITS, 2022) Das, Debasmita
In recent years, inorganic halide perovskites have come up as a great al ternative for hybrid organic-inorganic perovskites for photovoltaic applications. Methyl ammonium lead halide, although quite popular for its large power conversion efficiency and manufacturing ease, has certain draw backs owing to structural denaturation when exposed to UV rays, heat and moisture, and due to the toxicity of Pb element. An all inorganic halide perovskites like RbGeI3 can be an alternative, as the cations have similar configurations to the organic-inorganic counterpart, but they make up for the drawbacks the latter has. We studied the structural, electronic, and optical properties a particular phase- pn21a phase of RbGeI3to deter mine its suitability as a photoabsorber. We analyzed the material through DFT, which is a powerful approximation tool for many-electron systems like solids. Our compound shows a direct bandgap of 1.16 eV, and a wide absorption spectrum is observed in UV-Visible range, indicating this com pound can be a good photoabsorber.
Bipolar Nonvolatile Resistive Switching Memory Using Copper Ion Conductive Polymeric Film
(Department of Physics, NITS, 2022) Swain, Rosan
The resistance change memory is considered the basic building block for the new-age digital memory technology and can have applications in the areas like hardware implementation of neuromorphic computing and artificial intelligence. The resistance change memory is simple two-terminal metal-insulator-metal structures. Out of these two metal contacts, one is electrochemically active. For the development of the resistive switching memory, the switching or sandwiching layer is mostly explored for improved switching characteristics. The sandwiching layer could be oxides, semiconducting layers, or an ion-conducting material. Even organic or polymeric materials are also explored as the switching layer. The use of polymeric materials offers the advantage of developing flexible or wearable electronics. In the present study, we used copper-ion conductive polymer electrolyte as the switching layer where the top electrode used is copper. The device is a vertical two-terminal structure: ITO/Cu-polymer electrolyte/Cu. Initially, the copper-ion conductive solid polymer electrolyte (SPE) was synthesized and characterized. Then two-terminal structures of ITO/Cu-polymer electrolyte/Cu devices were fabricated and their switching properties were studied. Bipolar resistive switching is observed in simple Cu/CuSCN-PEO/ITO devices containing various concentrations of CuSCN complexes when the bias voltage is applied. By sweeping the voltage, the first SET process occurs at a higher voltage known as forming process. In the following switching cycles, SET occurs at ~0.7 V, and RESET occurs at -0.7 V. The switching behavior is highly influenced by Copper(I) thiocyanate concentration. We expect the observed switching is attributed to the production and dissolution of a copper metal filament inside the SPE film induced by electrochemical processes. The devices have OFF/ON resistance ratios up to 107. According to electrical measurements, 1% Copper(I) thiocyanate concentration is the most stable for switching applications. These findings suggest that SPE-based redox-type switching devices have the potential to explore further flexible electronic applications.
Growth Of ZnoNanotetrapods Via VLS Method
(Department of Physics, NITS, 2022) Panda, Bhupati
Hexagonal zinc-oxide nanotetrapod structures were synthesised on p-type Si(100). Without using any catalysts, ZnO nanostructures were deposited on Si substrates using a simple Vapour-Liquid-Solid (VLS) process. The crystal structure and surface morphology of these ZnO nanocrystals which are tetrapods in shape; were studied using SEM and XRD methods. The XRD result revealed that the structure of ZnO is wurtzite and the crystallite size is 21.96 nm. UV-Vis measurements were carried out and it has been found that the absorption peak is at 380 nm and its bandgap is found to be 3.25 eV. It appears that they are of similar properties with near band edge emission at 437 nm (nearly) wavelength or at 2.83 eV. The SEM analysis shows the nanostructure formed on the substrate are nano-tetrapods, and the junction is nearly Y-shaped.
AB-INITIO STUDY OF R3m-Rbgei3 For Photovoltaic Application
(Department of Physics, NITS, 2022) Banerjee, Palash
To fulfil the global energy demand and reduce dependence on fossil fuel, new energy source need to be explored. In this search solar energy has emerged as a clean and viable alternative but, large scale implementation is still a challenge due high cost of material and the complicated manufacturing process of absorber material like crystalline Si. In this regard halide perovskite material has came to focus as a cheaper alternative with comparable photovoltaic properties. But, presence of organic compound reduces its stability while Pb toxicity is also an hurdle. Hence the search for lead-free, inorganic perovskite for PV application is of prime interest. In this study we have explored one such material, all inorganic RbGeI3 within the scope of DFT with FP-(L)APW+lo method implemented by Wien2k. Structural properties like optimized atomic coordinates, lattice parameters, tolerance factor have been calculated indicating the structure’s stability. To get more profound knowledge for PV application, electronic properties like band structure, DOS, PDOS and optical properties like absorption(𝛼), real and imaginary part of dielectric constant (𝜀1,𝜀2), reflectivity(R) and refractive index(n) have been found including and excluding SOC effect. From band structure the compound was found to be a direct bandgap semiconductor. Bandgap using PBE was observed to be 0.958 eV while PBE + SOC was 0.823 eV. The absorption curve suggested that the material absorbs in visible and low UV range. Mechanical properties like elastic coefficients were also explored indicating it to be a stable material.
Effect of UV Ozone treatment on the photoconductivity of exfoliated MoS2 nanosheets
(Department of Physics, 2022-05-18) Biswal, Arijit
Due to some truly amazing properties of two-dimensional layered materials such as high surface volume ratio, quantum confinement of electrons in two dimensions, and advantage in band-gap designing due to the variable energy bandgap with layer thickness, they are very promising in the field of nanoelectronics. However, employing various exfoliation processes, it is also tough to accomplish monolayer or few-layer nanosheets (2-D) of such valuable material. Re-stacking of layers owing to Van der Waal's contact may reduce the stability of these kinds of two-dimensional nanosheets even after exfoliation. In this paper, we describe how to successfully exfoliate MoS2 into few-layer nanosheets using a probe sonication technique that is very persistent for months with no restacking. The yield of MoS2 nanosheets is 13.74 mg/ 10 ml DMF (the exfoliating medium). The production of 2-D MoS2 nanosheets is confirmed by SEM images. The XRD of exfoliated MoS2 sample provides information on the crystallite size and layer count. The crystallite size was calculated to be ~12 nm, and the nanosheet thickness is roughly 18-20 layers of Mos2. The increment of both UV-Visible absorbance peak (A, B, C, D) and PL intensity in the context of UV Ozone treatment gives an approximate notion of the incorporation of oxygen in the S-vacancy sites of MoS2. The I-V curve clearly illustrates the photoconductive essence of MoS2 nanosheets, whereas the increase in dark current and photocurrent of UV Ozone treated specimens confirmed that the embedded oxygen not only deactivates the S-vacancy sites of exfoliated MoS2 nanosheets but also acts as P-type dopants, generating P-type charge carriers. The results of this work show that UV Ozone treated exfoliated MoS2 thin films hold a lot of promises in the field of optoelectronics.
Application of Machine Learning and Deep Learning in High Energy Phenomenology
(Department of Physics, 2022-05-18) Chawla, Harshita
Artificial intelligence has vast applications in every field and it certainly has a lot of an application in the field of high-energy phenomenology. In this, we are going to explain how we can use machine learning and deep learning applications in computing important parameter regions and exploring the parameter space of new models. First, we will discuss deep learning models and machine learning algorithms in detail and then we will apply our knowledge to some basic models and then subsequently discuss their role in the high-energy phenomenology. We will also see how some of the applications that we can explore in physics and how can be applied.

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