88 research outputs found

    Dry Etching of GaAs to Fabricate Via-Hole Grounds in Monolithic Microwave Integrated Circuits

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    This study investigates the dry etching of 60 mm dia, 200 mm deep holes for fabrication of through substrate via holes for grounding monolithic microwave integrated circuits (MMICs), on 3-inch dia semiinsulating GaAs wafer using RIE and ICP processes with CFC and non-CFC gas chemistry, respectively. The effect of various process parameters on GaAs etch rate and resultant etch profile was investigated. Two kinds of masks, photoresist and Ni, were used to etch GaAs and performance was compared by investigating effect on etch rate, etch depth, etch profile, and surface morphology. The etch profile, etch depth, and surface morphology of as-etched samples were characterised by scanning electron microscopy. The desired 200 mm deep strawberry profile was obtained at 40 mTorr for both RIE and ICP processes with an etch rate of ~1.3 mm/min and ~4 mm/min respectively. Ni metal mask was used for RIE process due to poor photoresist selectivity, whereas ICP process utilised photoresist as mask. The vias were then metallised by depositing a thin seed layer of Ti/Au (1000 Å) using radio frequency sputtering and Au (~5 mm) electroplated to connect the frontside pad and back side ground plane. The typical parasitic inductance offered by these via for RIE and ICP processes was ~76 pH and 83 pH respectively, which is well within the acceptable limits. The developed process was finally integrated to in-house MMIC production line.Defence Science Journal, 2009, 59(4), pp.363-370, DOI:http://dx.doi.org/10.14429/dsj.59.153

    Physical property characterization of single step synthesized NdFeAsO0.80F0.20 bulk 50K superconductor

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    We report an easy single step synthesis route of title compound NdFeAsO0.80F0.20 superconductor having bulk superconductivity below 50 K. The title compound is synthesized via solid-state reaction route by encapsulation in an evacuated (10-3 Torr) quartz tube. Rietveld analysis of powder X-ray diffraction data shows that compound crystallized in tetragonal structure with space group P4/nmm. R(T)H measurements showed superconductivity with Tc (R=0) at 48 K and a very high upper critical field (Hc2) of up to 345 Tesla. Magnetic measurements exhibited bulk superconductivity in terms of diamagnetic onset below 50 K. The lower critical field (Hc1) is around 1000 Oe at 5 K. In normal state i.e., above 60 K, the compound exhibited purely paramagnetic behavior and thus ruling out the presence of any ordered FeOx impurity in the matrix. In specific heat measurements a jump is observed in the vicinity of superconducting transition (Tc) along with an upturn at below T=4 K due to the AFM ordering of Nd+3 ions in the system. The Thermo-electric power (TEP) is negative down to Tc, thus indicating dominant carriers to be of n-type in NdFeAsO0.80F0.20 superconductor. The granularity of the bulk superconducting NdFeAsO0.8F0.2 sample is investigated and the intra and inter grain contributions have been individuated by looking at various amplitude and frequencies of the applied AC drive magnetic field.Comment: 26pages text + Figures: comments/suggestions welcome ([email protected] & http://www.freewebs.com/vpsawana

    Measurement of the azimuthal anisotropy of Y(1S) and Y(2S) mesons in PbPb collisions at √S^{S}NN = 5.02 TeV

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    The second-order Fourier coefficients (υ2_{2}) characterizing the azimuthal distributions of ΄(1S) and ΄(2S) mesons produced in PbPb collisions at sNN\sqrt{s_{NN}} = 5.02 TeV are studied. The ΄mesons are reconstructed in their dimuon decay channel, as measured by the CMS detector. The collected data set corresponds to an integrated luminosity of 1.7 nb−1^{-1}. The scalar product method is used to extract the υ2_{2} coefficients of the azimuthal distributions. Results are reported for the rapidity range |y| < 2.4, in the transverse momentum interval 0 < pT_{T} < 50 GeV/c, and in three centrality ranges of 10–30%, 30–50% and 50–90%. In contrast to the J/ψ mesons, the measured υ2_{2} values for the ΄ mesons are found to be consistent with zero

    Measurement of prompt D0^{0} and D‟\overline{D}0^{0} meson azimuthal anisotropy and search for strong electric fields in PbPb collisions at root SNN\sqrt{S_{NN}} = 5.02 TeV

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    The strong Coulomb field created in ultrarelativistic heavy ion collisions is expected to produce a rapiditydependent difference (Av2) in the second Fourier coefficient of the azimuthal distribution (elliptic flow, v2) between D0 (uc) and D0 (uc) mesons. Motivated by the search for evidence of this field, the CMS detector at the LHC is used to perform the first measurement of Av2. The rapidity-averaged value is found to be (Av2) = 0.001 ? 0.001 (stat)? 0.003 (syst) in PbPb collisions at ?sNN = 5.02 TeV. In addition, the influence of the collision geometry is explored by measuring the D0 and D0mesons v2 and triangular flow coefficient (v3) as functions of rapidity, transverse momentum (pT), and event centrality (a measure of the overlap of the two Pb nuclei). A clear centrality dependence of prompt D0 meson v2 values is observed, while the v3 is largely independent of centrality. These trends are consistent with expectations of flow driven by the initial-state geometry. ? 2021 The Author. Published by Elsevier B.V. This is an open access article under the CC BY licens

    Measurement of the Y(1S) pair production cross section and search for resonances decaying to Y(1S)ÎŒâșΌ⁻ in proton-proton collisions at √s = 13 TeV

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    The fiducial cross section for Y(1S)pair production in proton-proton collisions at a center-of-mass energy of 13TeVin the region where both Y(1S)mesons have an absolute rapidity below 2.0 is measured to be 79 ± 11 (stat) ±6 (syst) ±3 (B)pbassuming the mesons are produced unpolarized. The last uncertainty corresponds to the uncertainty in the Y(1S)meson dimuon branching fraction. The measurement is performed in the final state with four muons using proton-proton collision data collected in 2016 by the CMS experiment at the LHC, corresponding to an integrated luminosity of 35.9fb−1^{-1}. This process serves as a standard model reference in a search for narrow resonances decaying to Y(1S)ÎŒ+^{+}Ό−^{-} in the same final state. Such a resonance could indicate the existence of a tetraquark that is a bound state of two bquarks and two b̅ antiquarks. The tetraquark search is performed for masses in the vicinity of four times the bottom quark mass, between 17.5 and 19.5GeV, while a generic search for other resonances is performed for masses between 16.5 and 27GeV. No significant excess of events compatible with a narrow resonance is observed in the data. Limits on the production cross section times branching fraction to four muons via an intermediate Y(1S)resonance are set as a function of the resonance mass

    Studies of charm and beauty hadron long-range correlations in pp and pPb collisions at LHC energies

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    Measurement of the CP-violating phase ϕs_{s} in the B0^{0}s_{s}→J/ψ φ(1020) →ΌâșΌ⁻KâșK⁻ channel in proton-proton collisions at √s = 13 TeV

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    Observation of electroweak production of Wγ with two jets in proton-proton collisions at √s = 13 TeV

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    A first observation is presented for the electroweak production of a W boson, a photon, and two jets in proton-proton collisions. The W boson decays are selected by requiring one identified electron or muon and an imbalance in transverse momentum. The two jets are required to have a high dijet mass and a large separation in pseudorapidity. The measurement is based on data collected with the CMS detector at a center-of-mass energy of 13 TeV, corresponding to an integrated luminosity of 35.9 fb−1^{-1}. The observed (expected) significance for this process is 4.9 (4.6) standard deviations. After combining with previously reported CMS results at 8 TeV, the observed (expected) significance is 5.3 (4.8) standard deviations. The cross section for the electroweak Wγjj_{γjj} production in a restricted fiducial region is measured as 20.4 +/- 4.5 fb and the total cross section for Wγ_{γ} production in association with 2 jets in the same fiducial region is 108 +/- 16 fb. All results are in good agreement with recent theoretical predictions. Constraints are placed on anomalous quartic gauge couplings in terms of dimension-8 effective field theory operators

    Search for Higgs and Z boson decays to J/ψ or Y pairs in the four-muon final state in proton-proton collisions at √s = 13 TeV

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    A measurement of the Higgs boson mass in the diphoton decay channel

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    A measurement of the mass of the Higgs boson in the diphoton decay channel is presented. This analysis is based on 35.9fb−1^{-1} of proton-proton collision data collected during the 2016 LHC running period, with the CMS detector at a centre-of-mass energy of 13TeV. A refined detector calibration and new analysis techniques have been used to improve the precision of this measurement. The Higgs boson mass is measured to be mH_{H}=125.78 ±0.26 GeV. This is combined with a measurement of mHalready performed in the H→ZZ→4l{l} decay channel using the same data set, giving mH_{H}=125.46 ±0.16 GeV. This result, when further combined with an earlier measurement of mHusing data collected in 2011 and 2012 with the CMS detector, gives a value for the Higgs boson mass of mH_{H}=125.38 ±0.14 GeV. This is currently the most precise measurement of the mass of the Higgs boson
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