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Wyszukujesz frazę "Wu, M." wg kryterium: Wszystkie pola


Wyświetlanie 1-10 z 10
Tytuł:
Signature of Hot Phonons in Reliability of Nitride Transistors and Signal Delay
Autorzy:
Matulionis, A.
Liberis, J.
Matulionienė, I.
Šermukšnis, E.
Leach, J.
Wu, M.
Ni, X.
Morkoç, H.
Powiązania:
https://bibliotekanauki.pl/articles/1506173.pdf
Data publikacji:
2011-02
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
72.70.+m
73.50.Fq
73.61.Ey
Opis:
Lifetime of non-equilibrium (hot) phonons in biased GaN heterostructures with two-dimensional electron gas channels was estimated from hot-electron fluctuations. Dependence of the lifetime on the electron density is not monotonous - the resonance-type fastest decay serves as a signature of hot phonons. The signature is resolved in nitride heterostructure field effect transistors when the gate voltage is used to change the channel electron density. The transistor cut-off frequency decreases on both sides of the resonance in agreement with the enhanced electron scattering caused by longer hot-phonon lifetimes. The signature is also noted in device reliability experiment: the enhanced temperature of hot phonons, possibly, triggers formation of new defects and accelerates device degradation.
Źródło:
Acta Physica Polonica A; 2011, 119, 2; 225-227
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Ultrafast Phenomena in Freestanding LT-GaAs Devices
Autorzy:
Marso, M.
Mikulics, M.
Adam, R.
Wu, S. Wu.
Zheng, X.
Camara, I.
Siebe, F.
Förster, A.
Güsten, R.
Kordoš, P.
Sobolewski, R.
Powiązania:
https://bibliotekanauki.pl/articles/2041640.pdf
Data publikacji:
2005-01
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
72.20.Jv
72.40.+w
78.30.Fs
85.60.-q
85.60.Gz
Opis:
We report on the fabrication and high-frequency performance of our photodetectors and photomixers based on freestanding low-temperature-grown GaAs. The MBE-grown low-temperature GaAs layers are lifted from the native GaAs substrate and transferred on top of variety of host substrates. The freestanding devices exhibit breakdown electrical fields above 200 kV/cm and dark currents below 3×10$\text{}^{-7}$ A at 100 V bias. Device photoresponse shows 0.55 ps wide electrical transients with voltage amplitudes up to 1.3 V, measured using an electro-optical sampling technique with 100 fs wide laser pulses. Photomixing experiments at 460 GHz yield a 9 times higher output power for the freestanding device on Si/SiO$\text{}_{2}$ host substrate compared to the native substrate.
Źródło:
Acta Physica Polonica A; 2005, 107, 1; 109-117
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Microstructure of the Pulsed Laser Deposited LaSrCuO Films
Autorzy:
Cieplak, M. Z.
Abal'oshev, A.
Zaytseva, I.
Berkowski, M.
Guha, S.
Wu, Q.
Powiązania:
https://bibliotekanauki.pl/articles/2046751.pdf
Data publikacji:
2006-04
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
68.55.-a
68.55.Jk
68.37.Ps
Opis:
The X-ray diffraction and atomic force microscopy are used to examine the microstructure of La$\text{}_{1.85}$Sr$\text{}_{0.15}$CuO$\text{}_{4}$ films grown by pulsed laser deposition on LaSrAlO$\text{}_{4}$ substrates. The films grow with different degrees of built-in strain, ranging from a large compressive to a large tensile in-plain strain. The tensile strain cannot be attributed to a substrate-related strain. The possible origins of the tensile strain are discussed.
Źródło:
Acta Physica Polonica A; 2006, 109, 4-5; 573-576
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Investigations on the EPR Parameters of $KMgF_3$:$Cr^{+}$
Autorzy:
Kuang, M.
Wu, S.
Hu, X.
Li, G.
Zu, H.
Powiązania:
https://bibliotekanauki.pl/articles/1365348.pdf
Data publikacji:
2014-05
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
75.10.Dg
76.30.Fc
Opis:
The electron paramagnetic resonance parameters (i.e., g factor, hyperfine structure constant and superhyperfine parameters) of $KMgF_3$:$Cr^{+}$ are theoretically investigated from the perturbation formulae of these parameters for an octahedral $3 d^5$ cluster. As for the calculations of g factor and hyperfine structure constant, both the contributions from the crystal-field and charge transfer mechanisms are included based on the cluster approach. The metal to ligand charge transfer contribution to the g-shift Δg ( ≈ g-2.0023) is the same (negative) in sign and much larger in magnitude as compared to the crystal-field one. The conventional argument that the charge transfer contributions to zero-field splittings are negligible for $3 d^5$ ions in fluorides is no longer suitable for Δg analysis of $KMgF_3$:$Cr^{+}$ due to the dominant second-order charge transfer perturbation term. The charge transfer contribution to hyperfine structure constant exhibits the same sign and about 4% of the crystal-field one. The unpaired spin densities of the fluorine 2s, 2pσ and 2pπ orbitals are quantitatively acquired from the relationships with the relevant molecular orbital coefficients using the uniform model. The present treatments are superior to the previous calculations of directly fitting the experimental superhyperfine parameters.
Źródło:
Acta Physica Polonica A; 2014, 125, 5; 1224-1228
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Raman Spectroscopy of $LiFePO_4$ and $Li_3V_2(PO_4)_3$ Prepared as Cathode Materials
Autorzy:
Ziółkowska, D.
Korona, K.
Kamińska, M.
Grzanka, E.
Andrzejczuk, M.
Wu, S.
Chen, M.
Powiązania:
https://bibliotekanauki.pl/articles/1493017.pdf
Data publikacji:
2011-11
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
78.30.Hv
82.80.Gk
82.47.Aa
Opis:
Structure of samples of lithium iron vanadium phosphates of different compositions were investigated by X-rays, electron microscopy and Raman spectroscopy. The investigated salts were mainly of olivine-like and NASICON-like structures. The X-ray diffraction and the Raman scattering show different crystalline structures, which is probably caused by difference between cores of the crystallites (probed by X-rays) and their shells (probed by the Raman scattering). Most of the Raman spectra were identified with previously published data, however in the samples with high vanadium concentration we have observed new, not reported earlier modes at 835 $cm^{-1}$ and 877 $cm^{-1}$, that we identified as oscillations related to $V_2O_7^{4-}$ or $VO_4^{3-}$ anions.
Źródło:
Acta Physica Polonica A; 2011, 120, 5; 973-975
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Rheological and Thermal Transport Characteristics of a Transformer Oil Based Ferrofluid
Autorzy:
Paulovičová, K.
Tóthová, J.
Rajňák, M.
Wu, Z.
Sundén, B.
Wadsö, L.
Tobiáš, T.
Kopčanský, P.
Timko, M.
Lisý, V.
Powiązania:
https://bibliotekanauki.pl/articles/1030831.pdf
Data publikacji:
2018-03
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
47.65.Cb
83.80.Gv
66.20.Ej
44.35.+c
Opis:
Ferrofluids based on insulating liquids are intensively studied as a potential substitute of liquid dielectric in high voltage technologies. In this work we focus on the experimental investigation of flow and thermal transport characteristics of a ferrofluid based on transformer oil (Mogul) and iron oxide nanoparticles. The magneto-rheological behavior of the ferrofluid was studied by a rotational rheometer in the shear rate range from 1 to 1000 s¯¹ and magnetic field up to 1 T. By means of a thermal constants analyzer and a transient plane source method we obtained the thermal conductivity, specific heat and thermal diffusivity values for the studied oil and the ferrofluid. It is shown that the Newtonian character of the ferrofluid changes to a non-Newtonian with application of the magnetic field. The notable magneto-viscous effect has been observed especially at low shear rates. We found that the doping of the transformer oil by 3 wt% of the nanoparticles results in a thermal conductivity enhancement by about 3.2%.
Źródło:
Acta Physica Polonica A; 2018, 133, 3; 564-566
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
High-Coercivity FePt Nanoparticle Assemblies Embedded in Oxide-Matrix by Atomic Layer Deposition
Autorzy:
Kong, J.
Li, A.
Gao, M.
Yan, Q.
Wu, D.
Powiązania:
https://bibliotekanauki.pl/articles/1399662.pdf
Data publikacji:
2013-02
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
75.50.Vv
75.75.Cd
75.50.Bb
75.50.Ss
Opis:
Self-assembled face-centered cubic FePt nanoparticles were embedded into the oxide capping layer using the atomic layer deposition technology. The effect of the oxide-matrix layer on the structure, mono-dispersibility, and magnetic properties of the FePt/oxide composite thin films was investigated. Experimental results suggest that the protection of the oxide-matrix capping layer can effectively inhibit the grain growth and particle aggregation, and preserve the ordered domains of the FePt nanoparticles during the L 1_0 ordering transition through annealing. The combination of the atomic layer deposition capping layer and self-assembled FePt nanoparticles provides a new potential approach to fabricate the ultrahigh-density magnetic recording media.
Źródło:
Acta Physica Polonica A; 2013, 123, 2; 173-176
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Development of a 20 kJ Sparker for High Resolution Ocean Seismic Survey
Autorzy:
Sun, Y.
Gao, Y.
Yan, P.
Wang, J.
Yuan, W.
Wu, H.
Wang, Y.
Wan, P.
Zhao, G.
Powiązania:
https://bibliotekanauki.pl/articles/1807914.pdf
Data publikacji:
2009-06
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
52.80.Wq
43.30.+m
Opis:
An ocean sparker with a stored energy of 20 kJ was developed for high resolution ocean seismic survey. The sparker is mainly composed of a high voltage high frequency charging supply, energy storage capacitors, a discharging switch and discharging electrodes. The H-bridge inverter and series resonant mode were adopted in the charging supply, and a dry high voltage transformer was used to improve the safety and maintenance, the average charging rate exceeded 4 kJ/s. An optical fiber connected between the high voltage system and the control system was used to isolate high voltage and transmit the high voltage signal. The high voltage electrodes of the discharging electrodes consisted of several hundreds of electrodes. The experimental results show that the sparker can be operated at repetition rates of 12 shots/min, and can meet the expected design requirements. Further field tests will be done in the near future.
Źródło:
Acta Physica Polonica A; 2009, 115, 6; 1059-1061
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Advanced Characterization of Material Properties on the Nanometer Scale Using Atomic Force Microscopy
Autorzy:
Fenner, M.
Wu, S.
Yu, J.
Huber, H.
Kienberger, F.
Powiązania:
https://bibliotekanauki.pl/articles/1490089.pdf
Data publikacji:
2012-02
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
77.55.-g
07.79.-v
68.37.Ps
68.37.Uv
07.57.Pt
Opis:
We report recent advances in material characterization on the nanometer scale using scanning microwave microscopy. This combines atomic force microscopy and a vector network analyzer using microwave tip sample interaction to characterize dielectric and electronic material properties on the nanometer scale. We present the methods for calibration as well as applications. Scanning microwave microscopy features calibrated measurements of: (1) capacitance with attofarad sensitivity. For calibration a well characterized array of capacitors (0.1 fF to 10 fF) is used. The method is applied to determine the dielectric properties of thin organic films, (2) Semiconductor dopant density. Calibration is performed by imaging the cross-section of a standard sample with differently doped layers (dopant stair case) from $10^{16}$ atoms/$cm^3$ to $10^{20}$ atoms/$cm^3$.
Źródło:
Acta Physica Polonica A; 2012, 121, 2; 416-419
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Investigations on the Anisotropic g Factors of the $Ni^{3+}$ Site in $La_2Ni_{0.5}Li_{0.5}O_4$
Autorzy:
Kuang, M.
Wu, S.
Zhang, Z.
Song, B.
Powiązania:
https://bibliotekanauki.pl/articles/1400149.pdf
Data publikacji:
2013-04
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
76.30.Fc
71.70.Ch
75.10.Dg
Opis:
The anisotropic g factors $g_{∥}$ and $g_{⊥}$ of $La_2Ni_{0.5}Li_{0.5}O_4$ are theoretically investigated using the perturbation formulae of the g factors for a low spin $(S=1//2) 3d^7$ ion in tetragonally elongated octahedra. The studied $Ni^{3+} (3d^7)$ center arises from the original $Ni^{2+}$ capturing one hole by $Li^{+}$ doping. The positive anisotropy $\Delta g (= g_{⊥}-g_{∥})$ can be ascribed to the lowest $\text{}^2 A_{1g}$ state due to the obvious (about 0.14 Å) tetragonal elongation of the oxygen octahedron around the $Ni^{3+}$ site via the Jahn-Teller effect, and the effective magnetic moment is also interpreted in a uniform way. The calculated results show good agreement with the experimental data, and the imperfection of the previous studies based on various adjusted tetragonal energy splittings without correlating to the local structure of the magnetic center is thus overcome in this work.
Źródło:
Acta Physica Polonica A; 2013, 123, 4; 734-736
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
    Wyświetlanie 1-10 z 10

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