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Träfflista för sökning "LAR1:liu ;pers:(Syväjärvi Mikael);srt2:(2000-2004)"

Sökning: LAR1:liu > Syväjärvi Mikael > (2000-2004)

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1.
  • Bikbajevas, V, et al. (författare)
  • Impact of phonon drag effect on Seebeck coefficient in p-6H-SiC : Experiment and simulation
  • 2003
  • Ingår i: Materials Science Forum, Vols. 433-436. ; , s. 407-410
  • Konferensbidrag (refereegranskat)abstract
    • The temperature dependence of Seebeck coefficient (S) for p-6H-SiC has been obtained. It increases from 2 up to 5.2 mV/K when temperature decreases from 400 down to 240 K. It is shown that phonon drag effect makes critical contribution to the S value. Improved theoretical model involving 4-phonon scattering process has been proposed for the simulation of Seebeck coefficient phonon pail.
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2.
  • Ciechonski, Rafal, et al. (författare)
  • Effect of Ambient on 4H-SiC Bulk Crystals grown by Sublimation
  • 2003
  • Ingår i: Materials Science Forum, Vols. 433-436. ; , s. 75-78
  • Konferensbidrag (refereegranskat)abstract
    • Sublimation bulk growth in vacuum using graphite crucibles and such with tantalum shielding of the crucible walls has been studied. Residual nitrogen, aluminum and boron doping in the material grown in vacuum is presented. Activation energies of growth rate in respect to growth temperature in vacuum are deduced. The estimated values are 21 kcallmole for growth temperatures below 2075°C and 128 kcal/mole in the range of growth temperatures between 2075°C and 2275°C. Cathodoluminescence spectra taken from samples grown in the graphite crucible in absence of tantalum under different pressures show nitrogen-alurninum DAP transition and strong luminescence from deep boron. This is not the case for samples grown in the tantalum environment.
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3.
  • Ciechonski, Rafal, et al. (författare)
  • Effect of boron on the resistivity of compensated 4H-SiC
  • 2003
  • Ingår i: Journal of electronic materials. - : Springer Science and Business Media LLC. - 0361-5235 .- 1543-186X. ; 32:5, s. 452-457
  • Tidskriftsartikel (refereegranskat)abstract
    • High-resistivity 4H-SiC samples grown by sublimation with a high growth rate are studied. The measurements show resistivity values up to a high of 104 Ωcm. The secondary ion mass spectroscopy (SIMS) results revealed a presence of only common trace impurities such as nitrogen, aluminum, and boron. To understand the compensation mechanism in these samples, capacitance deep-level transient spectroscopy (DLTS) on the p-type epilayers has been performed. By correlation between the growth conditions and SIMS results, we apply a model in which it is proposed that an isolated carbon vacancy donorlike level is a possible candidate responsible for compensation of the shallow acceptors in p-type 4H-SiC. A relation between cathodoluminescence (CL) and DLTS data is taken into account to support the model.
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4.
  • Dannefaer, S, et al. (författare)
  • Vacancies in As-grown and electron-irradiated 4H-SiC epilayers investigated by positron annihilation
  • 2003
  • Ingår i: Materials Science Forum, Vols. 433-436. ; , s. 173-176
  • Konferensbidrag (refereegranskat)abstract
    • Epilayers of 4H-SiC were investigated by positron annihilation spectroscopies: four epilayers and their substrates were investigated. The epilayers (47 to 220 mum thick) contained significantly lower grown-in vacancy concentration than did their substrates, and there was no dependency on layer thickness. Upon electron irradiation silicon vacancies were introduced at the same rate in epilayer and in substrate.
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5.
  • Davydov, SY, et al. (författare)
  • Simple model for calculation of SiC epitaxial layers growth rate in vacuum.
  • 2004
  • Ingår i: Materials Science Forum, Vols. 457-460. ; , s. 249-252
  • Konferensbidrag (refereegranskat)abstract
    • Within the frame of a simple model, based on Hertz-Knudsen equation with account of temperature dependant sticking coefficient, temperature dependence of silicon carbide epitaxial layers growth rate in vacuum has been calculated. Calculation results are in a good agreement with the experimental data.
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6.
  • Davydov, S.Yu., et al. (författare)
  • A Simple Model for Calculating the Growth Rate of Epitaxial Layers of Silicon Carbide in Vacuum
  • 2004
  • Ingår i: Semiconductors (Woodbury, N.Y.). - : American Institute of Physics (AIP). - 1063-7826 .- 1090-6479. ; 38:2, s. 150-152
  • Tidskriftsartikel (refereegranskat)abstract
    • The temperature dependence of the growth rate of epitaxial layers of silicon carbide in vacuum was calculated within the simple model based on the Hertz-Knudsen equation, taking into account the temperature-dependent sticking coefficient. The calculation results fit the experimental data well. © 2004 MAIK "Nauka/Interperiodica".
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7.
  • Glans, P.-A., et al. (författare)
  • Core level and valence band photoemission study of the (1 1 1) and (1¯ 1¯ 1¯) surfaces of 3C-SiC
  • 2001
  • Ingår i: Surface Science. - 0039-6028 .- 1879-2758. ; 470:3, s. 284-292
  • Tidskriftsartikel (refereegranskat)abstract
    • A core level and valence band photoemission study of thick 3C-SiC(1 1 1) and 3C-SiC(1¯ 1¯ 1¯) epilayers grown by sublimation epitaxy is reported. The as introduced samples show threefold 1×1 low-energy electron diffraction patterns. For the Si face v3 and 6v3 reconstructed surfaces develop after in situ heating to 1100 °C and 1300 °C, respectively. For the C face a 3×3 reconstruction form after heating to 980 °C. A semiconducting behavior is observed for the v3 and 3×3 reconstructed surfaces while the 6v3 reconstruction show a Fermi edge and thus a metallic-like behavior. The surface state on the v3 surface is investigated and found to have ?1 symmetry and a total band width of 0.10 eV within the first surface Brillouin zone. For the Si2p and C 1s core levels binding energies and surface shifted components are extracted and compared to earlier reported results for 6H- and 4H-SiC.
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8.
  • Grivickas, P., et al. (författare)
  • Carrier lifetime investigation in 4H-SiC grown by CVD and sublimation epitaxy
  • 2001
  • Ingår i: Materials Science in Semiconductor Processing. - 1369-8001 .- 1873-4081. ; 4:03-jan, s. 191-194, s. 191-194
  • Tidskriftsartikel (refereegranskat)abstract
    • Depth-resolved carrier lifetime measurements were performed in low-doped epitaxial layers of 4H silicon carbide samples. The technique used was a pump-and-probe technique where carriers are excited by an above-bandgap laser pulse and probed by free carrier absorption. Results from chemical vapour deposition samples show that lifetimes as high as 2 mus may be observed in the mid-region of 40 mum thick epilayers. For epilayers grown by the sublimation method decay transients were characterised by a fast (few nanoseconds) initial recombination, tentatively assigned to the 'true' lifetime, whereas a slow tail of several hundred microsecond decay time was assigned to trapping centres. From the saturation of this level at increased pumping we could derive the trapping concentration and their depth distribution peaking at the epilayer/substrate interface.
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9.
  • Grivickas, V, et al. (författare)
  • Thermopower measurements in 4H-SiC and theoretical calculations considering the phonon drag effect
  • 2001
  • Ingår i: Materials Science Forum, Vols. 353-356. ; , s. 491-494
  • Konferensbidrag (refereegranskat)abstract
    • The Seebeck coefficient study in a heavily nitrogen-doped n-type 4H-SiC epilayer in the direction perpendicular to c-axis is presented. The Seebeck coefficient steeply increases from 0.56 mV/K to 1.7 mV/K with decreasing temperature in the range 400-80 R. This behavior is explained by the phonon drag effect. An approach to the theoretical modeling of the phonon drag effect is discussed and simulation of the Seebeck coefficient temperature-dependence is displayed.
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10.
  • Henry, Anne, et al. (författare)
  • Presence of hydrogen in SiC
  • 2001
  • Ingår i: Materials Science Forum, Vols. 353-356. ; , s. 373-376, s. 373-376
  • Konferensbidrag (refereegranskat)abstract
    • An unexpected presence of hydrogen in 4H-SiC was revealed by the observation of hydrogen related lines in the low-temperature photoluminescence (LTPL) spectrum after secondary ion mass spectrometry (SIMS) measurements. The lines were not observed before SIMS. The high-energy ions during SIMS are proposed to break the boron-hydrogen bonds. This phenomenon is observable only for a certain impurity concentration in the material due to the competition of various recombination channels during the LTPL experiment.
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