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Effect of balanced and unbalanced magnetron sputtering processes on the properties of SnO2 thin films
No full textA comparative study has been carried on the role of balanced magnetron (BM) and unbalanced magnetron (UBM) sputtering processes on the properties of SnO2 thin films. The oxygen partial pressure, substrate temperature and deposition pressure were kept 20%, 700 degrees C and 30 mTorr, respectively and the applied RF power varied in the range of 150-250 W. It is observed that the UBM deposition causes significant effect on the structural, electrical and optical properties of SnO2 thin films than BM as evidenced by X-ray diffraction, C-V, Spectroscopic Ellipsometer and Photoluminescence measurements. The value of band gap (E-g) of the films deposited at 150 W in UBM is found as E-g = 3.83 eV which is much higher than the value of E-g = 3.69 eV as observed in BM sputtering indicating that UBM sputtering results in good crystalline quality. Further, the C-V measurements of SnO2 thin films deposited using UBM at high power 250 W show hysteresis with large flat band shift indicating that these thin films can be used for the fabrication of memory device. The observed results have been attributed to different mechanisms which exist simultaneously under unbalanced magnetron sputtering due to ion bombardment of growing SnO2 thin film by energetic Ar+ ions
Electrochemical performance of Sb2S3/CNT free-standing flexible anode for Li-ion batteries
No full textSb2S3/CNT composite has been synthesized through ethylene glycol-mediated solvothermal process, and binderless, free-standing, flexible anode is prepared from the composite through vacuum filtration technique. The 1-D rod-like structure of Sb2S3 prevents self-agglomeration and exhibits well-guided charge-discharge kinetics and high surface area enhancing their electrochemical performance in Li-ion batteries. The introduction of CNTs to the Sb2S3 facilitates the preparation of free-standing flexible anodes as well as buffers the volume changes that occur during repeated cycling, thereby improving the cycling stability. The Sb2S3/CNT free-standing anode exhibits a high initial discharge capacity of 930 mAhg(-1) at a current rate of 200 mAg(-1). The anode also exhibits excellent lifetime stability and rate capability by cycling at different current rates up to 1200 mAg(-1). Sb2S3/CNT anode gives a stable capacity of 443 mAhg(-1) after 100 cycles at a current density of 200 mAg(-1), while Sb2S3 rods deliver only 293 mAhg(-1) after 100 cycles at the same current rate. This free-standing flexible Sb2S3/CNT anode is highly promising in comparison with conventional graphite powder anode
Evolution of SPR in 120MeV silver ion irradiated Cu (18%) C-60 nanocomposites thin films
No full textCopper metal embedded fullerene C-60 thin films are deposited on various substrates via resistive heating co evaporation technique. Rutherford back scattering simulated spectrum confirms the thickness and composition of thin film to be 32nm and 18at%, respectively. The deposited thin films are irradiated by 120MeV Ag ion beam for different fluences within the range, from 1x10(12) to 3x10(13) ions/cm(2). UV-vis absorption spectroscopy study reveals the appearance of surface plasmon resonance (SPR) band in pristine thin film at 622nm; this phenomenon is ascribed to the presence of copper nanoparticles in C-60 matrix. The SPR band intensity increases with rising fluences, which is suggestive of the growth of Cu nanoparticles. Growth of Cu nanoparticles is further confirmed by transmission electron microscopic (TEM) and X-ray diffraction (XRD) study. Whereas the conversion of C-60 into amorphous carbon (a-C) is confirmed by Raman spectroscopy, XRD results of pristine Cu-C-60 thin film record the presence of Cu2O within the nanocomposite thin film. However, both X-ray photoelectron spectroscopy (XPS) and XRD studies on irradiated thin film samples authenticate the growth of Cu metal nanoparticles with concurrent removal of oxygen
Exploring Low Power Design Through Performance Analysis of FinFET for Fin Shape Variations
No full textWith concern of global warming, low power design is an important research domain for scientist and engineers. Focusing upon the energy saving trend, this paper compares the performance analysis of all possible fin shapes in a 16 nm Bulk FinFET device from low power design perspective. Performance metrics include transconductance, transconductance generation factor (TGF), on/off current ratio, Subthreshold swing (SS), Drain Induced Barrier Lowering (DIBL) and power consumption. Low power system design feasibility with the optimized round fin shape resulting from the comparative analysis is justified by implementing N and P FinFET devices with perfectly matched VI characteristics. Prospective usage to meet recent developments in system design and control engineering with power optimization and scalability success in round FinFET device is also reviewed through this work
Monte Carlo Simulation in Uncertainty Evaluation: Strategy, Implications and Future Prospects
No full textMonte Carlo simulation (MCS) is an approach based on the propagation of the full probability distributions. It was introduced by the Joint Committee for Guides in Metrology (JCGM) in the supplement I-JCGM 101:2008. It is used to resolve the problem of calculating measurement uncertainties of complex measurands through simulation of random variables. Further, supplement II on "Extension to any number of output quantities" was published in 2011 and supplement III on "Modelling" is under publication. These supplements cover broader range of measurement issues which are not handled using law of propagation of uncertainty (LPU) alone and provide an alternative method to the conventional LPU approach. The MCS method plays a vital role in cases, where the linearization of the model does not provide enough depiction, or the probability density function of the output quantity deviates considerably from the Gaussian distribution. The SWOT analysis describes the strengths, weaknesses, opportunities and threats associated with the use of MCS in the measurement uncertainty evaluation and is addressed in this paper. The paper also summarizes the implications and prospects associated with the use of MCS in uncertainty evaluation for wide usage in solving problems in physical, biological and engineering sciences
Atomic flux distribution from a low-divergent dark wall oven
No full textNearly collimated atomic beam is of interest for a variety of experiments. This article reports a simple way of modifying the atomic beam distribution using a dark wall oven and describes detailed study of outcoming atoms' spatial distribution. A simple design is obtained by employing the fact that inhomogeneous thermal distribution along a capillary results due to its partial resistive heating. Based on this phenomenon, we have designed a dark wall oven consisting of a reservoir, collimator, and cold absorber at the exit end of atoms, where all three are fabricated out of a single stainless steel capillary. The nearly collimated spatial distribution of the atoms resulting due to the absorber eliminating the atoms diverging above a certain angle is modeled and experimentally verified. A divergence as minimum as 1.2(1)degrees corresponding to a half angle theta(1/2) = 0.9(1)degrees is measured at an oven temperature of 250 degrees C that produces an atomic flux of about 8 x 10(9) atoms s(-1). Total flux as estimated using our measured spatial distribution of atoms matches well with the numerically simulated values of it for the dark wall oven
Coexistence of quasi-two dimensional electron and hole gas in a single tier Ca0.5TaO3/SrTiO3 oxide heterostructure
Get PDFQuasi-two-dimensional electron gas has been realized at the polar-nonpolar interface of several insulating oxide heterostructures. However, its hole counterpart remains elusive. In an attempt to find a novel system that exhibits quasi-two-dimensional hole gas (q-2DHG) at the heterointerface, we adopt to materials search, first based on phenomenology followed by a comprehensive set of calculations based on first-principles density functional theory. Our studies show the epitaxial growth of cubic Ca0.5TaO3 on TiO2 terminated substrate display (q-2DHG). The hole gas emanates from the O 2p orbitals of the TiO2 layers of the substrate. On the other hand, an electron gas is formed at the (001) TaO2 top surface, thereby representing the heterostructure as a coupled quantum well system. The partial filling of the Ta 5dt(2g) conduction band indicates electron reconstruction, in agreement with the polar catastrophe model. Besides, a critical thickness of three monolayers is deduced from the calculations for the formation of q-2DHG in the Ca0.5TaO3/SrTiO3 heterostructure, which is consistent with the model prediction based on the modern theory of polarization. With both cubic systems, Ca0.5TaO3 and SrTiO3, having a similar underlying symmetry and minimal lattice mismatch, epitaxial growth with an abrupt interface can be well anticipated. Such a single-tier oxide heterostructure composed of separated confined hole-electron subsystems is expected to provide a platform to unravel exciting physics and also for functional devices related to oxide electronics
2-Dimensional sub-atomic localization of Rb Rydberg atoms for SI traceable E-field metrology
Get PDFIn this work, Electromagnetically Induced Transparency (EIT) has been studied in a RF-driven four-level ladder 85 Rb atomic model. Rb atomic cell is simultaneously driven by three fields; two lasers, namely control and probe and one microwave. This spectroscopic technique of exposing atomic vapors to three energies may get established as a quantum primary standard for the RF electric-field amplitude metrology due to its dependency only on universal Plank's constant. It is observed that when right resonant frequency is achieved the absorption spectrum gives a transition to EIT by inducing a window in middle of the curve cancelling the absorption. In addition, two-dimensional localization of an atom is also studied in various field scenarios. The maxima of absorption spectrum can be modified by making slight modifications in the electromagnetic fields driving the system. Next step in the metrology would be of measuring vector E-field for which finding the position of an atom may play a crucial role. This may add one extra degree of freedom in the evaluation of SI traceable E-field
BIAS VARIATION BETWEEN TWO CO-LOCATED GNSS RECEIVERS
Get PDFTime and Frequency Metrology Section of CSIR-National Physical Laboratory, India has two dual frequency GNSS timing receivers. The receivers are being used for establishing primary traceability link to SI second for realizing local Universal Coordinated Time UTC(NPLI). The GNSS based navigation timing solution are based on pseudorange measurement made by correlating user receiver generated replica signals with the signals broadcast by the GNSS satellites. Biases arise in the receiver during the correlation process remain common and uniform across all receiver channels and eventually that common bias will cancelled out in the user navigation solution but will appear as fixed bias for timing solution. The timing bias includes the internal delays within the GNSS receiver and antenna hardware accounting the combined effect of the multi frequency and also the offset of the local timing reference i.e. UTC(NPLI). The reference 10MHz and 1PPS to these receivers is the steered output of Active Hydrogen Maser (AHM). Earlier the reference was high performance Cs-clock and the link was using two single frequency receivers. The study has done for long period and found that the bias variation between these dual frequency receivers exist with time. Although these receivers are placed in environment controlled room but outside environment is varying. The antenna and antenna cable are affected with the outside environment. The critical parameter of the environment are temperature and humidity which are varying 0° to 50°C and 0 to 100% respectively over the year. The peak to peak variation between these receivers is observed ~2 ns using P3 analysis. The receivers used in this analysis are PolaRx3eTR (make Septentrio) and TTS-4 (make PikTime)
Fog Computing Research: A Scientometric Assessment of Global Publications Output During 2012-18
Get PDFThe present study has examined fog computing global research output, as indexed in Scopus database during 2012-18 on a series of bibliometric measures, such as publications growth rate, global publications share, citation impact, the share of international collaborative papers, distribution of publications by broad subjects. In addition, the study discusses the citation profile of top organizations and authors in fog computing, and the preferred media for research communication and characteristics of highly cited papers. The study finds 1711 global research output registered (68.09%) annual growth rate. 81 countries participated in fog computing research, of which the top 10 countries accounted for 91.23% global publication share and more than 100% of global citation share during 2012-18. China and USA tops the list of top 10 most productive countries in fog computing research with 22.38% and 19.40% global publication share, followed by India (9.70%), Italy (7.36%), Australia (6.14%), etc. USA top the list (17.02% and 2.25%), followed by Australia (15.54% and 2.06%), UK (12.09% and 1.59%), Canada (11.03% and 1.46%), Spain
(9.95% and 1.32%), etc. in terms of citation impact per paper and relative citation index. 401 organizations and 457 authors participated in global fog computing research, of which the top 10 organizations and authors contributed (15.02% and 7.48%) global publication share and (42.17% and 12.81%) global citations share during 2012-18. The world contributed (59.75%) share of output in fog computing research in top 20 most productive journals, and 19 of its papers have been rated as highly cited papers each with 100 to 1657 citations per paper, averaging 209.79 citations per pape