Sohail Khan

Sohail Khan

PhD

About

43
Publications
18,651
Reads
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324
Citations
Citations since 2017
7 Research Items
196 Citations
201720182019202020212022202301020304050
201720182019202020212022202301020304050
201720182019202020212022202301020304050
201720182019202020212022202301020304050

Publications

Publications (43)
Preprint
Full-text available
A cost effective method is provided to obtain ultra-thin silicon wafers starting from the usual 300m wafers. The wafers are etched in a particular way and then polished. The polishing of the wafers resulted in a high degree of transmittance better than the purchased ones. The RMS of the etched portion is found to increase with etching time. Transm...
Preprint
Full-text available
Polishing of fibers to optical flatness is one of the primary requirements of various sensors. However the procedure of using epoxy limits the applicability since the fiber remains connected to the ferrule. A simpler procedure involving epoxy-free polishing gives a ferrule free fiber allowing first of its kind application that is to explore the opt...
Book
Full-text available
This book is meant for persons who have some prior knowledge of the subject. The standard of the book is that of a first year university student. A knowledge of calculus is important though some chapters can be read without the knowledge of calculus. It would be useful as a text book if the aim is cover the physics in a period of one year or two se...
Article
Projection operator techniques modified to handle orthogonal states and extension of potential in sudden approximation to non-identical nuclei are used to extract resonance parameters and resonant states. Application to 8Be, α-12C and α-16O systems show good agreement with experimental work.
Article
Full-text available
The surface plasmon effect in metallic photonic crystals has been investigated. Band structure graph is the only graph that can be used to explain the characteristics of photonic crystals. In this work, band structure graphs have been used to describe these characteristics, which include the surface plasmon effect of photonic crystals. Recently, ba...
Article
The quasimolecular potential in the sudden approximation is used both near and above the Coulomb barrier (CB) for the 12C+16Osystem. It is found that the resonances associated with the dinuclear configuration are well produced in energy above the CB. Near and below the CB where adiabatic potential is appropriate, it was found that the potential can...
Article
This paper presents the development of a physically based solar cell simulation using the Silvaco-TCAD simulator. Simulations were performed on a Si based solar cell with antireflection coating (ARC), without ARC and ARC with back surface field. Single layer SiO2 ARC was used and its effect on each solar cell was analysed. The effect of BSF and AR...
Article
This work investigates the radiation tolerance of c-Si solar cells under electron energy of 9 MeV with fluence of 5.09×1016 cm−2. The solar cells were fabricated and characterized before and after electron irradiation through current-voltage (I-V), capacitance-voltage (C-V), and frequency dependent conductance (Gp) measurements. The results...
Article
Nanocrystalline antireflective silicon nitride (Si3N4; 75 nm) film was deposited on a silicon P (1 1 1) substrate by a radio frequency sputtering system. The film was prepared in reactive nitrogen–argon (N2–Ar) atmospheres with substrate heating at 200 °C. The average crystallite size was 1.06 nm for the Si3N4 film. The RMS roughness was found to b...
Article
Silicon based solar cells have been fabricated for single layer SiO2 and double layer SiO2/TiO2 antireflective coatings (ARC) using rf sputtering technique. The results were obtained with non-texturized surface of p-type mono-crystalline silicon (100) substrate and compared with the as-grown Si solar cell. Effect of single layer (SLAR) and double l...
Article
Full-text available
Indium tin oxide (ITO) and titanium dioxide (TiO2) anti-reflective coatings (ARCs) were deposited on a (100) P type monocrystalline Si substrate by a radio-frequency (RF) magnetron sputtering. Polycrystalline ITO and anatase TiO2 films were obtained at room temperature (RT). The thickness of ITO (60 nm to 64 nm) and TiO2 (55 nm to 60 nm) films was...
Data
Back surface field (BSF) (n + –p–p +) silicon (Si) solar cells were fabricated with and without TiO 2 or SiO 2 single layer antireflection (SLAR) coatings. The two cell types were obtained with non-texturized surfaces and compared with each other, as well as with an as-grown Si solar cell. The effective aluminium–BSF was fabricated through a simple...
Article
Full-text available
Radon concentration, exhalation rate, radium activity and annual effective dose have been measured from baked and unbaked bricks and cement samples commonly used as construction material in the dwellings of Dera Ismail Khan City, Pakistan. CR-39 based NRPB radon dosimeters and RAD7 have been used as passive and active devises. The values of radon c...
Article
Full-text available
Abstract. The effect of time and temperature on the sheet resistance (RS) and carrier concentration (NA) of (100) P-type monocrystalline Si was investigated. Phosphorus-doped nþ-emitters were fabricated through solid-source doping in a quartz tube furnace. The process variable values for 13 runs were proposed by response surface methodology (RSM)....
Article
Full-text available
We report the gamma-ray (γ-ray) radiation-induced defects incurred by a monocrystalline Si solar cell. Capacitance–voltage (C–V) and dark current–voltage (I–V) characteristics were investigated from 1 kHz to 100 kHz at room temperature. The Co60 activity used for the γ-ray irradiation of a Si solar cell was 24864.37 atom Bq. The laboratory-made sol...
Conference Paper
Molecular dynamics simulation has been carried out to study the thermal-physical properties of strontium titanate and barium zirconate ceramic materials. Pairwise interactions, which consist of Coulombic interaction, short-range repulsion, Van der Waals attraction and Morse-type covalent bonding, have been adopted to represent the intricate inter...
Article
Full-text available
n this paper, a molecular dynamics (MD) simulation is carried out to study the microscopic atomic behavior and the macroscopic thermodynamic and thermal transport properties of a perovskite material. A new set of potential parameters is presented for barium zirconate. The radial distribution function is estimated to understand the atomic and struct...
Article
Full-text available
Diffusion process on different temperatures and related effects on ideality factor (η) and recombinations in solar cell have been investigated. Phosphorus-doped n+-emitters were fabricated by applying Spin-on doping (SOD). Dark current-voltage characterization has been used to investigate different recombinations and their relation with the idealit...
Article
a b s t r a c t A molecular dynamics simulation has been performed to investigate the thermal expansivity, isothermal compressibility, heat capacity and thermal conductivity of strontium titanate. The potential model cap-tures the ionic and covalent characteristics of strontium titanate well. The parameters of the model were derived by fitting agai...
Conference Paper
To fabricate a good solar cell, doping concentration play a role. As such, right doping concentration selection is necessary to produce high output value and then contribute to high efficiency. As starting material used are monocrystalline Cz p-type (100) silicon wafer with a resistivity of about 1 Ω.cm [1] and were polished on one side [2]. On the...
Article
Copper ferrites were prepared through co-precipitation technique. The aim of this effort was to present a novel and economical method of preparation of copper ferrites via co-precipitation technique. Structural properties were studied with the help of XRD technique while micro structural study of the samples was carried out by SEM. The particle siz...
Article
Full-text available
A modified potential of the sudden approximation, modified to include interactions among nuclei of different radii, is applied to explain the mass asymmetry of fission fragments in the thermal fission of Uranium-235. The results are encouraging in that the asymmetry feature in the fission yield is displayed. It appears that the mass asymmetry is a...
Article
Full-text available
Quasimolecular optical potentials used for identical nuclei have been modified for application to different interacting nuclei. This has been applied to the 28Si-16O system and compared to the Woods-Saxon potential that had been found to reproduce the experimental results. The result indicates that the modification is useful and provides informatio...
Article
Full-text available
By using plane wave expansion method, we calculated the photonic band structure of metal cylinders in adielectric medium. The photonic crystal is an identical, symmetrical structure with an infinite array of metallicrods. Arrangement of the metallic rods used is square lattice. The dielectric function of the metal from which thecylinders are formed...
Article
Full-text available
The projection operator method was applied to the recently produced superheavy elements ranging from Z = 106 to 118. Woods-Saxon potentials were used with conditions on the number of nodes in the alpha particle relative motion. The optical potential was required to have a sharp boundary. Spectroscopic factors, lifetimes, and reduced widths were ext...
Article
Full-text available
Generalized band structure equation for photonic crystals which containing dielectric rods in metals medium was derived by using the plane wave expansion method. From the band structure, we can study band gap of photonic crystals in both E and H polarizations. Since metals are frequency-dependant materials, modification needs to be done on the plan...
Article
Full-text available
By using the plane wave expansion method, we have calculated the band gap for a metallic slab with air rods in the transverse magnetic (TM) mode. The metallic structure of this system is an identical, symmetric structure and an infinite array of air rods. The arrangement of the air rods we used are a square lattice and a triangular lattice. The die...
Article
Full-text available
Methods used previously for quasibound states of not so heavy, heavy-ion nuclear systems are applied to obtain information on diatomic molecules at the atomic level. Such calculations agree with the results obtained by authors using other methods over the entire range from J = 4 to 38. In this process besides obtaining resonance energies and widths...
Conference Paper
The object of this paper is to calculate the band gap energy of the newly designed waveguide structure. The structure used was 2 layers of perfect conductor (PEC) sandwiched with an electromagnetic band gap (EBG) or photonic crystals (PC) in the center. The lattice arrangement of the EBG was square lattice. The cylinder rods is made of PEC also and...
Article
Full-text available
The object of this paper is to study the fundamental characteristic of the dimensional triangular lattice photonic crystals. The structure we studied consisted of a periodic array of dielectric rods in a dielectric slab. This structure has a certain forbidden gap which can be found by solving the Maxwell Equation. In this paper, we studied the freq...
Article
Full-text available
The quasimolecular optical potential with Incoming Wave Boundary Condition model is used to obtain the fusion and elastic scattering cross-section at the sub-Coulomb region and above. This has been done for the 16O+16O and 12C+12C systems. It is found that sudden potentials describe well the average trend in the fusion and elastic scattering cross-...
Article
Full-text available
An exact expression using the projection operator method to extract widths and spectroscopic factors is derived. It is applied to sub-Coulomb resonances as they occur in α-decay. A number of α-decaying nuclei are investigated. The widths and spectroscopic factors extracted using the proposed expression are found to be in excellent agreement with th...
Article
The Projection Operator Method as applied to the study of resonances is first briefly reviewed. Its shortcomings, in the context of reactions that involve forbidden states are mentioned. The forbidden states arise due to the requirement of antisymmetrization imposed by the Pauli exclusion principle, on the many body wave function. A modification th...
Article
Sub-Coulomb cross sections for 12C+12C--a+23Ne, 12C+ 12C--p+ 'Na, and 12C+ 12C--n +"Mg are calculated in a semistatistical framework that allows a comparison to experiment in terms of the general energy dependence and magnitude. Intermediate structure previously produced in the generalized doorway model via calculations of the structure factor is n...
Article
A nuclear projection model that produces generalized doorways in the sub-Coulomb region is used to calculate the modified structure factor S(E) in 12C+ 12C down to about 3 MeV c.m. The formation of a compound nucleus is enhanced at energies near those of the generalized doorways which are obtained by coupling the shape resonances to the single and...
Article
Full-text available
It is found that exact and perturbative treatments of the imaginary potential at sub-Coulomb energies in C12+C12 provide close agreement in calculations of both the real and imaginary phase shifts at energies away from resonance.
Article
A nuclear projection model is developed for heavy-ion reactions in the sub-Coulomb region. Generalized doorways are introduced as the set of resulting states obtained by coupling the shape resonances to the single and mutual excitation channels. The model is applied to the /sup 12/C+/sup 12/C reaction by treating the /sup 12/C nucleus as deformed,...
Article
Full-text available
A projection operator method is presented for the extraction of resonance energies, shifts, and widths of bound states embedded in the continuum for potentials that have a repulsive core. The procedure is applicable for heavy ion as well as nucleon-nucleus collisions. The original potential is modified beyond the radius where the repulsive core mer...
Article
The ('12)C+('12)C reaction is studied below the Coulomb barrier. After a brief review of the current status a model termed the "generalized doorway" model is proposed. Within the framework of this model each doorway is taken to consist of parts of the elastic channel, the single excitation channel and the mutual excitation channel. The excitations...
Article
Full-text available
Projection operator methods are used to obtain the elastic differential scattering cross section at 90° c.m. for 28Si+ 28Si in the region Elab=100–120 MeV. Good agreement with the energies and structures of resonances seen experimentally is obtained by introducing doorway states for l=34–38 constructed from a particle-vibration model that includes...
Article
We show under what conditions the transformations in the paraxial region from the object space to the image space by combination of lenses in air forms a continuous group. First the case of a single lens is treated. Here the concept of the middle point and its shift is introduced. Using this, the condition to form a group is obtained. Next, the cas...

Questions

Question (1)
Question
A system of ideal gas can always be made to obey classical statistical mechanics by varying the temperature and the density. Now a wave packet for each particle is known to expand with time. Therefore after sufficient time has elapsed the gas would become an assembly of interacting wavelets and hence its properties would change since now it would require a quantum mechanical rather than classical description. The fact that a transition in properties is taking place without outside interference may point to some flaw in quantum mechanics. Any comments on how to explain this.

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