Indian Journal of Pure & Applied Physics (IJPAP) https://or.niscpr.res.in/index.php/IJPAP <p style="text-align: justify;">Started in 1963, this journal publishes Original Research Contribution as full papers, notes and reviews on classical and quantum physics, relativity and gravitation; statistical physics and thermodynamics; specific instrumentation and techniques of general use in physics, elementary particles and fields, nuclear physics, atomic and molecular physics, fundamental area of phenomenology, optics, acoustics and fluid dynamics, plasmas and electric discharges, condensed matter-structural, mechanical and thermal properties, electronic, structure, electrical, magnetic and optical properties, cross-disciplinary physics and related areas of science and technology, geophysics, astrophysics and astronomy. It also includes latest findings in the subject under News Scan.</p> <p style="text-align: justify;"><strong><span class="style1"><span style="font-family: Verdana;">Impact Factor of IJPAP is 0.7 (JCR 2022).</span> </span></strong></p> en-US ijpap@niscpr.res.in (Dr. Kanika Malik) op@niscpr.res.in (Digital Information Resources Division (For tecnical support only)) Tue, 21 Jan 2025 12:30:35 +0530 OJS 3.3.0.13 http://blogs.law.harvard.edu/tech/rss 60 A New Threshold Voltage Model of Short Channel FD-SOI MOSFET by Green’s Function Approach to Analytically Solving 2-D Laplace/Poisson’s Equations in Multi-Zone Structure and Applying it to Study Post-Implant Annealing Effect https://or.niscpr.res.in/index.php/IJPAP/article/view/9124 <p class="Abstract"><span lang="EN-GB">This paper reports on new analytical models of front and back gate threshold voltages for short-channel fully depleted silicon-on-insulator (FD-SOI) MOSFETs, considering an annealed non-uniform impurity profile resulting from retrograde doping required for vertical channel engineering. For this purpose, the exact solutions of multi-zone 2-D Laplace/Poisson equations have been obtained by adopting a new Green’s function approach. Since the SOI MOSFET is a three-layer structure, we have established new multi-zone Green’s functions that incorporate the combined effects of all three layers joined together at the interfaces. This approach allows for a more nuanced analysis of potential distributions in the three-layer structure of SOI devices, taking into account the interactions between the different layers within the device. Considering the explicit potential relations thus derived, we formulate closed-form expressions of front and back gate threshold voltages, which include the front and back gate charge coupling effects, the profile annealing effect, and the effects of drain and gate voltages. This holistic perspective is crucial because it enables a more accurate understanding of how these variables interact and affect device operation, thereby enhancing the predictive capability of the models. In addition to the front and back gate threshold voltages, their biasing counterparts—the respective back and front gate voltages—have also been formulated, accounting for the aforementioned effects, in order to determine operational modes of the device under study. Finally, the results obtained from the new model have been rigorously validated by comparison with data generated by ATLAS software, revealing excellent alignment between the two. This validation not only supports the reliability of the proposed models but also enhances their applicability in practical semiconductor device simulation and design. </span></p> Krishna Meel, Ram Gopal, Chitra Gautam Copyright (c) 2025 Indian Journal of Pure & Applied Physics (IJPAP) https://creativecommons.org/licenses/by/4.0 https://or.niscpr.res.in/index.php/IJPAP/article/view/9124 Tue, 21 Jan 2025 00:00:00 +0530 Crystal Structure Analysis using Rietveld Refinement and Investigation of Electrical Properties of NaNbO3 Substituted CaTiO3 Ceramics https://or.niscpr.res.in/index.php/IJPAP/article/view/9803 <p>Polycrystalline samples (1-x)CaTiO<sub>3</sub>-xNaNbO<sub>3</sub> (x = 0, 0.10, 0.20, 0.30 and 0.40) were synthesized using solid state reaction method. Powder X-ray diffraction at room temperature showed that all of the samples' crystal structures were orthorhombic with Pbnm space group. Low χ<sup>2 </sup>values were obtained and there was good agreement between the computed and observed XRD patterns according to the Rietveld refinement. Impedance spectroscopy of the samples was investigated over a broad frequency and temperature range. Nyquist plots of the samples depicted a thermally activated non-Debye type relaxation mechanism. A decrease in dispersive nature of dielectric constant (ɛ¢) and tangent loss (tan d) at low frequencies is noticed in the NaNbO<sub>3 </sub>substituted samples rendering them a better stability. The samples became more resistive with NaNbO<sub>3</sub> substitution in CaTiO<sub>3</sub> lattice. Correlation between charge carriers and lattice has been established using modulus formalism. Imaginary impedance (Z¢¢) and imaginary modulus (M¢¢) have been employed to comprehend the conduction process in all the samples.</p> M. Sindhu, N Ahlawat, S. Sanghi, R. Kumari, Deepak Nandal, LALIT KUMAR, Nitin Mittal, Vikas Nandal, Vinay Shankar Pandey, A. Agarwal Copyright (c) 2025 Indian Journal of Pure & Applied Physics (IJPAP) https://creativecommons.org/licenses/by/4.0 https://or.niscpr.res.in/index.php/IJPAP/article/view/9803 Tue, 21 Jan 2025 00:00:00 +0530 Connection between Rainfall and Solar Activity Features during Solar Cycle 20 to 24 https://or.niscpr.res.in/index.php/IJPAP/article/view/9942 <p>This study examines the statistical relationship between all-India homogenous rainfall (RF) and different Solar Activity Features (SAF) - Sunspot Number (SN), Solar Active Prominence (SAP) and Solar Flare (SF) throughout five consecutive solar cycles (20 to 24) from 1964 to 2019. For all yearly and seasonal periods RF has a significant correlation coefficient with SAF (SN, SAP, SF). It shows a positive trend of RF from solar cycle 20 to 24. In various solar cycle phases, the RF exhibits distinct variability. We found two prominent periods of 2.5 year and 3.5 year for RF when studied the annual variation of RF over the period of 55 years (cycle 20-24) and other periods were ranging from 2 to 10 year. According to the RF normal probability distribution studied over 55 years, we found that 700-750 mm RF is most likely to occur. Our investigation concludes that RF variability is influenced by SAF incidence.</p> MAHESH CHANDRA MATHPAL, Raj Kumar kumar, Alankrita Joshi JOSHI, yogesh chandra, BIMAL PANDE PANDE, Seema Pande Pande Copyright (c) 2025 Indian Journal of Pure & Applied Physics (IJPAP) https://creativecommons.org/licenses/by/4.0 https://or.niscpr.res.in/index.php/IJPAP/article/view/9942 Tue, 21 Jan 2025 00:00:00 +0530 Coulomb Nuclear Interference in 31Cl Breakup Reaction https://or.niscpr.res.in/index.php/IJPAP/article/view/12813 <p>The effect of Coulomb nuclear interference on the magnitude of core fragment longitudinal momentum distribution (LMD) width and single proton breakup cross-section has been examined quantitatively for <sup>31</sup>Cl nucleus breakup reaction. The analysis is performed for <sup>12</sup>C, <sup>58</sup>Ni, and <sup>208</sup>Pb targets in a range of intermediate incident energies (40-100 AMeV), using a semiclassical method that treats the full Coulomb and nuclear interaction to all orders, including full multipole expansion of the Coulomb potential. We examined, in detail, the interference between Coulomb and nuclear diffraction reaction mechanisms and also between core-target and proton-target Coulomb potentials and quantitatively analyzed its effect on the breakup observables. The sensitivity of interference on the target size and incident energy is also examined. Our calculations show that due to the interference effect in light and heavy target cases, the absolute magnitude of a single proton breakup cross-section varies from 1% to 7%, while for medium target, it varies around 20%; on the other hand, the Full Width Half Maxima (FWHM) width of longitudinal momentum distribution varies approximately from 1% to 4% for all the target nuclei. Therefore, we believe that our work presented a bit deeper insight into the role of Coulomb nuclear interferences in <sup>31</sup>Cl breakup reaction, which is helpful for a better understanding of experimental data and planning future breakup reaction experiments.</p> Surender, Ravinder Kumar Copyright (c) 2025 Indian Journal of Pure & Applied Physics (IJPAP) https://creativecommons.org/licenses/by/4.0 https://or.niscpr.res.in/index.php/IJPAP/article/view/12813 Tue, 21 Jan 2025 00:00:00 +0530 Numerical Approach based Study of MHD Viscous and Viscoelastic Immiscible Fluids Flow through Porous Channel https://or.niscpr.res.in/index.php/IJPAP/article/view/12993 <p style="text-align: justify; text-indent: 1.0pc; margin: 0pc 2.0pc 11.0pt 2.0pc;"><span lang="EN-US" style="font-size: 9.0pt;">The study and application of multiphase magnetohydrodynamic (MHD) fluid flow in porous media extend to several fields including petroleum engineering, environmental engineering, polymer processing and manufacturing, and several others. In these industries, the flow of viscous and viscoelastic fluids prevails through various channels where the many flow issues exist and require extensive investigation. In the present study, the viscous and viscoelastic immiscible magnetohydrodynamic (MHD) fluid flow through a porous horizontal channel between two plates is examined. In the channel, the viscoelastic fluid flows in upper region and the viscous fluid flows in the lower region. The flow is considered to be through a constant pressure gradient. The porous media of the upper and lower regions have two different permeabilities. The governing equations and boundary conditions are derived as per the channel geometry for these flows. These differential equations are solved analytically. The roots of the cubic equation in the viscoelastic fluid governing equation are obtained for different values of the viscoelastic parameter and permeability coefficient. The boundary conditions are applied to these solutions and obtained equations are solved numerically to obtain the values of coefficients involved in the solution using a MATLAB program. Finally, the effect of various flow governing parameters is shown on velocity profiles through various graphs. The results show that on applying the magnetic field velocity decreases. It has been shown that the MHD field application causes a drop in shear stress at the lower plate while increasing in the upper plate. The magnetic field effect on volume flow rate is also analysed and found that it increases with increasing magnetic field values. The effect of other parameters is also shown on shear stress and flow rate and the results are discussed through various graphs and tables.</span></p> Neeraj Srivastava, Rajesh Johari Copyright (c) 2025 Indian Journal of Pure & Applied Physics (IJPAP) https://creativecommons.org/licenses/by/4.0 https://or.niscpr.res.in/index.php/IJPAP/article/view/12993 Tue, 21 Jan 2025 00:00:00 +0530 Numerical Simulation of Blood Flow of Casson Fluid with Brownian Motion and Thermophoresis Effect https://or.niscpr.res.in/index.php/IJPAP/article/view/13251 <p>This research presents a comprehensive numerical investigation into two-dimensional, unsteady blood flow, incorporating the combined effects of thermophoresis and Brownian motion. The study aims to explore how these phenomena influence the dynamics of blood flow under various conditions. To facilitate the analysis, a similarity transformation approach is employed to reduce the complex system of partial differential equations governing the flow into a system of ordinary differential equations. These simplified equations are then solved numerically using a finite difference scheme, with the bvp4c solver in MATLAB and shooting techniques, to obtain both graphical and numerical results. The study specifically examines the effects of several key physical factors on the primary variables of interest in blood flow, including velocity, temperature, and concentration. Through detailed analysis, the research highlights how changes in parameters such as thermophoretic force, Brownian motion, and other relevant factors influence the flow characteristics and behaviour of blood under unsteady conditions. The findings from this investigation have significant practical implications in biomedical applications, including enhancing the understanding of blood flow for blood cancer treatments and improving the effectiveness of magnetic therapies.</p> Laltesh Kumar, Atar Singh, Vimal Kumar Joshi, KUSHAL SHARMA Copyright (c) 2025 Indian Journal of Pure & Applied Physics (IJPAP) https://creativecommons.org/licenses/by/4.0 https://or.niscpr.res.in/index.php/IJPAP/article/view/13251 Tue, 21 Jan 2025 00:00:00 +0530 Investigations of Production Cross Sections and Induced Activity of 94,95,96,98Tc Produced in Mo Target by 30 MeV Proton Beam https://or.niscpr.res.in/index.php/IJPAP/article/view/13477 <p>Theoretical models often fill significant gap exists in measured data and radioisotopes produced may be used in research, medical and safely disposal of radioactive waste. The excitation functions of <sup>94</sup>Mo(p,n)<sup>94</sup>Tc, <sup>95</sup>Mo(p,n)<sup>95</sup>Tc, <sup>96</sup>Mo(p,n)<sup>96</sup>Tc and <sup>98</sup>Mo(p,n)<sup>98</sup>Tc reactions were investigated using nuclear reaction model codes TALYS-1.95 and EMPIRE-3.2.3 from reaction threshold to 30 MeV. These codes incorporate three major nuclear reaction mechanisms including direct, compound and pre-compound nuclear reactions. Theoretical results obtained from TALYS-1.95 and EMPIRE-3.2.3 codes were compared with existing literature data and found to be in reasonable agreement. Additionally, induced radioactivity estimation is also conducted for a thick Mo target due to the primary interaction of 1μA, 30 MeV proton beam.</p> Pawan Kumar, Sneh Lata Goyal Copyright (c) 2025 Indian Journal of Pure & Applied Physics (IJPAP) https://creativecommons.org/licenses/by/4.0 https://or.niscpr.res.in/index.php/IJPAP/article/view/13477 Tue, 21 Jan 2025 00:00:00 +0530 Improvement in Structural and Optical Properties of ZnFe2O3-δ in Nano Structured Materials with Fe2O3 Concentration https://or.niscpr.res.in/index.php/IJPAP/article/view/13592 <p>At present time, technologies of particles at nanoscale are a blazing field for today's researchers. The transition metal oxide (TMO) nanomaterials are used immensely because of their colourful properties caused by their valence d-orbital electrons. The ZnO and Fe<sub>2</sub>O<sub>3</sub> nano particulates have promised properties such as electrical, magnetic, antibacterial and photo-catalytical etc. In present work, researchers synthesized pure ZnO and Fe doped ZnO nano particulates by microwave irradiated chemical co-precipitation method. The as-synthesized samples were calcined at 600 ºC for 2 hrs. The various concentration (5, 10 &amp; 20 %) Fe doped samples were examined through XRD, FTIR, FESEM and HRTEM tools. The XRD results revealed that calcined samples were formed of hexagonal wurtzite structure of ZnO parental structure with crystallite size 26 nm (5%), 44 nm (10%) and 50 nm (20%) respectively. The presence of Fe<sup>3+</sup> ions produces a uniform strain in crystals. The significant IR peaks at position at 853 cm<sup>-1</sup> and 514 cm<sup>-1</sup> may be attributed by O-Fe-O &amp; O-Zn-O of Fe<sub>2</sub>O<sub>3</sub> and ZnO respectively. The morphology of nanoparticles was examined through electron microscopy <em>i.e</em>. FESEM and HRTEM. FESEM results showed that nanoparticles are irregular in size with stone-like polygon structure and porous in nature. HRTEM images revealed that particles are polycrystalline in shape, agglomerated in nature and nano in size. The average grain size measured by Image J software was 42.3nm and also supports the XRD results. The UV visible spectroscopic results of samples shows that newer materials are highly sensitive in the wavelength range of visible spectra and have ΔE – 1.8 eV respectively. So, newer materials may have recommended key material for fabrication of photo induced properties devices such as solar cell aided photovoltaic and photodiode. The PL spectra of the Fe doped ZnO nano particulates reveals that their excitation wavelength was 303 nm which is located in the strong UV emission region and has a solid emission peak at 665 nm which lies in the red region of white spectrum.</p> Tanuja Kumari, Anita Yadav, Rajesh Sharma Copyright (c) 2025 Indian Journal of Pure & Applied Physics (IJPAP) https://creativecommons.org/licenses/by/4.0 https://or.niscpr.res.in/index.php/IJPAP/article/view/13592 Tue, 21 Jan 2025 00:00:00 +0530 Self-protective Antibacterial and Hydrophobic ZnO Thin Film Coatings https://or.niscpr.res.in/index.php/IJPAP/article/view/14282 <p class="pb-2" style="text-align: justify; text-indent: 1.0pc; margin: 0pc 2.0pc 11.0pt 2.0pc;"><span class="issue-underline"><span lang="EN-US" style="font-size: 9.0pt;">The Sol-Gel dip-coating technique was used to fabricate nanostructured ZnO thin-film coatings on amorphous glass substrates. To assess the impact of annealing temperature, the coated substrates were annealed at 400, 450, and 500 °C substrate temperatures respectively. X-ray diffraction, scanning electron microscopy, and optical double-beam spectroscopy were used to evaluate the effect of annealing temperature on the structural, morphological, and optical properties of the produced thin films. The disc diffusion technique and contact angle measurements were used to examine the obtained films’ hydrophobic characteristics and antibacterial activity. The obtained diffraction data revealed that all films have the polycrystalline hexagonal wurtzite crystal structure. When the annealing temperature was raised, it was observed that crystal grain sizes increased from 22.69 nm to 29 nm, indicating an improvement in crystallinity. The electronic micrographs clearly showed that the nanograins were evenly spaced over the film surface. Additionally, it was observed that increasing the annealing temperature resulted in a blue shift in the optical bandgap from 3.19eV to 3.09eV. The fabricated films showed increased antibacterial activity and hydrophobicity.</span></span></p> M Narasimha Murthy, M Gopi Krishna , G Chandrakala Copyright (c) 2025 Indian Journal of Pure & Applied Physics (IJPAP) https://creativecommons.org/licenses/by/4.0 https://or.niscpr.res.in/index.php/IJPAP/article/view/14282 Tue, 21 Jan 2025 00:00:00 +0530 A Systematic Review of Machine Learning-based Small-Signal Modeling Approaches for Gallium Nitride High Electron Mobility Transistors: Performance Analysis and Algorithmic Insights https://or.niscpr.res.in/index.php/IJPAP/article/view/13938 <p class="Abstract"><span lang="EN-GB">Machine learning (ML)- based modeling is an evolving and thriving research field that must be kept up to date with technological advancements. This paper presents an in-depth analysis of Gallium Nitride High electron mobility transistor (GaN HEMT) behavioral modeling using ML techniques. Through a comparative analysis of ML-based approaches, we explore the development of HEMT models, encompassing scattering parameters, C-V and I-V characteristics, thermal profiles, and more. It also explores conventional techniques and their limitations, emphasizing the advantages of ML applications. This study systematically identifies, analyzes, summarizes, and reports the current state of utilization of ML in the modeling of GaN HEMT. The study critically assesses various ML techniques, including regression, optimization, Artificial Neural Network (ANN), Support Vector Regression (SVR), Decision Tree (DT), Particle Swarm Optimization (PSO), and genetic algorithms (GA), etc. considering precision, complexity, and computational efficiency. Intended for engineers and researchers in electronic and semiconductor devices, this paper serves as a crucial resource, fostering cross-disciplinary collaboration and aiding in the selection of appropriate modeling algorithms in this rapidly progressing field, thereby contributing significantly to the existing literature.</span></p> Neda Ahmad, Vandana Nath Copyright (c) 2025 Indian Journal of Pure & Applied Physics (IJPAP) https://creativecommons.org/licenses/by/4.0 https://or.niscpr.res.in/index.php/IJPAP/article/view/13938 Tue, 21 Jan 2025 00:00:00 +0530