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1.
A series of (Ca1−x−y
Sr
x
)Si2O2N2:yEu2+ (x=0.0–0.97, y=0.03) phosphors were synthesized by high-temperature solid-state reaction. The XRD patterns confirm the formation of a solid
solution of (Ca1−x−y
Sr
x
)Si2O2N2:yEu2+. An intense tunable green light is observed with the increasing ratio of Sr/Ca. With an increase in x, the excitation and emission spectra show a redshift and blueshift, respectively, due to large centroid shift and small Stokes
shift. The temperature dependent luminescence is also investigated in the temperature range of 77–450 K. The Huang–Rhys factor
and the thermal-quenching temperature are determined. Intense green LEDs were successfully fabricated based on the (Ca1−x−y
Sr
x
)Si2O2N2:yEu2+ phosphor and near-ultraviolet (∼395 nm) GaN/blue (460 nm) InGaN chips. All the results indicate that the solid solution (Ca1−x−y
Sr
x
)Si2O2N2:yEu2+ is a promising phosphor applicable to near-UV and blue LEDs for solid-state lighting. 相似文献
2.
H. Kim A. Cepler C. Cetina D. Knies M. S. Osofsky R. C. Y. Auyeung A. Piqué 《Applied Physics A: Materials Science & Processing》2008,93(3):593-598
Present p-type ZnO films tend to exhibit high resistivity and low carrier concentration, and they revert to their natural n-type state
within days after deposition. One approach to grow higher quality p-type ZnO is by codoping the ZnO during growth. This article describes recent results from the growth and characterization
of Zr–N codoped p-type ZnO thin films by pulsed laser deposition (PLD) on (0001) sapphire substrates. For this work, both N-doped and Zr–N
codoped p-type ZnO films were grown for comparison purposes at substrate temperatures ranging between 400 to 700 °C and N2O background pressures between 10−5 to 10−2 Torr. The carrier type and conduction were found to be very sensitive to substrate temperature and N2O deposition pressure. P-type conduction was observed for films grown at pressures between 10−3 to 10−2 Torr. The Zr–N codoped ZnO films grown at 550 °C in 1×10−3 Torr of N2O show p-type conduction behavior with a very low resistivity of 0.89 Ω-cm, a carrier concentration of 5.0×1018 cm−3, and a Hall mobility of 1.4 cm2 V−1 s−1. The structure, morphology and optical properties were also evaluated for both N-doped and Zr–N codoped ZnO films. 相似文献
3.
4.
Wanwimon Banlue Naratip Vittayakorn 《Applied Physics A: Materials Science & Processing》2008,93(2):565-569
The solid solution between the antiferroelectric PbZrO3 (PZ) and relaxor ferroelectric Pb(Co1/3Nb2/3)O3 (PCoN) was synthesized by the columbite method. The phase structure and thermal properties of (1−x)PZ–xPCoN, where x=0.0–0.3, were investigated. With these data, the ferroelectric phase diagram between PZ and PCoN has been established. The
crystal structure data obtained from XRD indicates that the solid solution PZ–PCoN, where x=0.0–0.3, successively transforms from orthorhombic to rhombohedral symmetry with an increase in PCoN concentration. The AFE→FE
phase transition was found in the compositions of 0.0≤x≤0.10. The AFE→FE phase transition shift to lower temperatures with higher compositions of x. The width of the temperature range of FE phase was increased with increasing amount of PCoN. It is apparent that the replacement
of the Zr4+ ion by (Co1/3Nb2/3)4+ ions would decrease the driving force for antiparallel shift of Pb2+ ions, because they interrupt the translational symmetry. This interruption caused the appearance of a rhombohedral ferroelectric
phase when the amount of PCoN was more than 10 mol%. 相似文献
5.
Roland Schmidt Erik McNellis Wolfgang Freyer Daniel Brete Tanja Gießel Cornelius Gahl Karsten Reuter Martin Weinelt 《Applied Physics A: Materials Science & Processing》2008,93(2):267-275
Self-assembled monolayers (SAMs) of 4-trifluoromethyl-azobenzene-4′-methyleneoxy-alkanethiols (CF3– C6H4–N=N–C6H4–O–(CH2)
n
–SH on (111)-oriented poly-crystalline gold films on mica were examined by X-ray photoelectron spectroscopy (XPS) and X-ray
absorption spectroscopy (XAS). The spectra are analyzed with the help of density-functional-theory calculations of the isolated
molecule. Only one doublet is detected in the sulphur 2p spectra of the investigated SAMs, consistent with a thiolate bond of the molecule to the gold surface. The C 1s XP spectra and the corresponding XAS π
* resonance exhibit a rich structure which is assigned to the carbon atoms in the different chemical surroundings. Comparing
XPS binding energies of the azobenzene moiety and calculated initial-state shifts reveals comparable screening of all C 1s core holes. While the carbon 1s XPS binding energy lies below the π
*-resonance excitation-energy, the reversed order is found comparing core ionization and neutral core excitation of the nitrogen 1s core-hole of the azo group. This surprising difference in core-hole binding energies is interpreted as site-dependent polarization
screening and charge transfer among the densely packed aromatic moieties. We propose that a quenching of the optical excitation
within the molecular layer is thus one major reason for the low trans to cis photo-isomerization rate of azobenzene in aromatic-aliphatic
SAMs. 相似文献
6.
A series of stoichiometric and nonstoichiometric copper–chalcogenide nanocrystallines with different morphologies, e.g., extremely
high aspect ratio nanofibers (Cu9S8), tubular structure (Cu
x
S (x=∼1.86–1.96), nanorods (CuS, Cu31S16), platelets (β-CuSe, Cu3Se2), rope-like Cu3Se2, as well as spherical nanoparticles (Cu7Se4, Cu2−x
Se), have been successfully synthesized in 20 vol% water and 80 vol% organic solvents mixture under mild conditions. The products
were characterized by various techniques, including X-ray powder diffraction (XRD), scanning electron microscopy (SEM), transmission
electron microscopy (TEM), electronic diffraction (ED), and high-resolution transmission electron microscopy (HRTEM). The
studies of the optical properties revealed that the copper chalcogenides have a wide absorption in the range of about 400–700 nm,
with accessional IR band. Systematic studies showed that the mixture of 20 vol% water and 80 vol% organic solvents played
a key role in controlling the copper chalcogenides with different morphologies and phases. 相似文献
7.
M. Bryushinin V. Golubev Y. Kumzerov D. Kurdyukov I. Sokolov 《Applied physics. B, Lasers and optics》2009,95(3):489-495
We report an experimental investigation of the non-steady-state photoelectromotive force in nanostructured GaN within porous
glass and polypyrrole within chrysotile asbestos. The samples are illuminated by an oscillating interference pattern created
by two coherent light beams and the alternating current is detected as a response of the material. Dependences of the signal
amplitude versus temporal and spatial frequencies, light intensity, and temperature are studied for two wavelengths λ=442 and 532 nm. The conductivity of the GaN composite is measured: σ=(1.1–1.6)×10−10 Ω−1 cm−1 (λ=442 nm, I
0=0.045–0.19 W/cm2, T=293 K) and σ=(3.5–4.6)×10−10 Ω−1 cm−1 (λ=532 nm, I
0=2.3 W/cm2, T=249–388 K). The diffusion length of photocarriers in polypyrrole nanowires is also estimated: L
D=0.18 μm. 相似文献
8.
Hao Wang Y. Wang J. Feng C. Ye B. Y. Wang H. B. Wang Q. Li Y. Jiang A. P. Huang Z. S. Xiao 《Applied Physics A: Materials Science & Processing》2008,93(3):681-684
High-k gate dielectric hafnium dioxide films were grown on Si (100) substrate by pulsed laser deposition at room temperature. The
as-deposited films were amorphous and that were monoclinic and orthorhombic after annealed at 500°C in air and N2 atmosphere, respectively. After annealed, the accumulation capacitance values increase rapidly and the flat-band voltage
shifts from −1.34 V to 0.449 V due to the generation of negative charges via post-annealing. The dielectric constant is in
the range of 8–40 depending on the microstructure. The I–V curve indicates that the films possess of a promising low leakage
current density of 4.2×10−8 A/cm2 at the applied voltage of −1.5 V. 相似文献
9.
Tunable diode-laser absorption of CO2 near 2.7 μm incorporating wavelength modulation spectroscopy with second-harmonic detection (WMS-2f) is used to provide a
new sensor for sensitive and accurate measurement of the temperature behind reflected shock waves in a shock-tube. The temperature
is inferred from the ratio of 2f signals for two selected absorption transitions, at 3633.08 and 3645.56 cm−1, belonging to the ν
1+ν
3 combination vibrational band of CO2 near 2.7 μm. The modulation depths of 0.078 and 0.063 cm−1 are optimized for the target conditions of the shock-heated gases (P∼1–2 atm, T∼800–1600 K). The sensor is designed to achieve a high sensitivity to the temperature and a low sensitivity to cold boundary-layer
effects and any changes in gas pressure or composition. The fixed-wavelength WMS-2f sensor is tested for temperature and CO2 concentration measurements in a heated static cell (600–1200 K) and in non-reactive shock-tube experiments (900–1700 K) using
CO2–Ar mixtures. The relatively large CO2 absorption strength near 2.7 μm and the use of a WMS-2f strategy minimizes noise and enables measurements with lower concentration,
higher accuracy, better sensitivity and improved signal-to-noise ratio (SNR) relative to earlier work, using transitions in
the 1.5 and 2.0 μm CO2 combination bands. The standard deviation of the measured temperature histories behind reflected shock waves is less than 0.5%.
The temperature sensor is also demonstrated in reactive shock-tube experiments of n-heptane oxidation. Seeding of relatively
inert CO2 in the initial fuel-oxidizer mixture is utilized to enable measurements of the pre-ignition temperature profiles. To our
knowledge, this work represents the first application of wavelength modulation spectroscopy to this new class of diode lasers
near 2.7 μm. 相似文献
10.
Samuel R. Schroeder Carl W. White Tara N. Jones Tara B. Hendry-Hofer Brian J. Day Sandra S. Eaton 《Applied magnetic resonance》2011,40(1):125-134
The superoxide dismutase (SOD)-mimetic effectiveness of [meso-tetrakis(R)porphyrinato]manganese with R = 1,3-di-N-ethylimidazolium-2-yl (Mn-TDEIP), 1,3-di-N-methylimidazolium-2-yl (Mn-TDMIP), 1,3-di-N-propylimidazolium-2-yl (Mn-TDPIP), N-ethyl-2-pyridyl (Mn-T2EPyP), 4-sulphonatophenyl (Mn-TSP), 1-methyl-4-pyridyl (Mn-T4PyP), 4-carboxyphenyl (Mn-TBAP), and β-octabromo-meso-tetrakis(4-carboxyphenyl
porphyrinato)manganese (MnBr8TBAP) was compared with Cu, Zn SOD. Superoxide generated by reaction of xanthine oxidase with hypoxanthine was trapped with
5-tert-butoxycarbonyl-5-methyl-1-pyrroline N-oxide (BMPO), forming BMPO–OOH, which was monitored by electron paramagnetic resonance. Manganoporphyrins with redox potentials
ranging from −0.190 to 0.346 V relative to the standard hydrogen electrode were selected for this study. With 0.1 μM manganoporphyrins
and 20 mM BMPO, the effectiveness of the manganoporphyrins in inhibiting formation of BMPO–OOH increases in the order Mn-TSP < Mn-TBAP < MnBr8TBAP < Mn-T4PyP < Mn-T2EPyP < Mn-TDEIP ~ Mn-TDMIP ~ Mn-TDPIP ~ Cu, Zn SOD. However, at higher concentrations of manganoporphyrin
and BMPO, a BMPO–OH signal was observed. The formation of BMPO–OH was not inhibited by catalase or dimethylsulfoxide, which
demonstrated that it was not produced from hydroxyl radical. The artifactual formation of BMPO–OH is attributed to oxidation
of the water adduct of BMPO by the manganoporphyrins or decomposition of BMPO–OOH. Although spin trapping is an effective
method for evaluating SOD-mimetic efficacy, caution must be exercised to ensure that artifact signals are not interpreted
improperly. 相似文献
11.
Cubic ZnSe nanowires with periodically alternating twins along the wire growth direction are synthesized in the ZnCl2–Na2SeO3–AgNO3–ethylenediamine (EN)-ethylene glycol (EG)-polyvinyl–pyrrolidone (PVP) solvothermal system at 180°C for 12 h. The twinned
ZnSe nanowires have diameters of 75±10 nm and lengths of >10 micrometers, and grow along 〈111〉 direction. The role of AgNO3 in the formation of ZnSe nanowires was investigated, and an Ag+ induced solution–liquid–solid growth mechanism is also proposed to account for the conversion of microspheres assembled from
ZnSe nanocrystallites into ZnSe nanowires. Compared with ZnSe microspheres, the as-prepared twinned ZnSe nanowires exhibit
stronger band edge emissions of the wurtzite- and zinc-blende-structured ZnSe and lower deep defect related emission, and
their photocatalytic ability is weaker than that of ZnSe microspheres. The results suggest that this simple, mild, one-step
solution approach to fabricate ZnSe nanowires may be employed for the synthesis of other selenium compounds with one dimensional
nanostructures, and provides opportunities for both fundamental research and technological applications. 相似文献
12.
L. A. Gómez C. B. de Araújo R. Putvinskis S. H. Messaddeq Y. Ledemi Y. Messaddeq 《Applied physics. B, Lasers and optics》2009,94(3):499-502
Nonlinear (NL) optical properties of antimony–germanium–sulfur (Sb–Ge–S) glasses were investigated using laser pulses of 65 fs
at 1560 nm. Samples having concentration ratio [S]/[Ge]=2.69 with different antimony concentrations were studied. Glasses
with different oxidation states of Sb were investigated using the thermally
managed
Z
-scan technique. The influence of the Sb oxidation state on the NL properties was evaluated. NL refraction indices of electronic origin,
n
2≈10−13 cm2/W, two-orders of magnitude larger than for fused silica and NL absorption coefficients smaller than 0.55 cm/GW were measured.
Appropriate figures-of-merit for photonic applications were determined. 相似文献
13.
Preparation and characterization of graphitic carbon nitride through pyrolysis of melamine 总被引:1,自引:0,他引:1
Xuefei Li Jian Zhang Longhai Shen Yanmei Ma Weiwei Lei Qiliang Cui Guangtian Zou 《Applied Physics A: Materials Science & Processing》2009,94(2):387-392
Graphitic carbon nitride (g-C3N4) has been synthesized via a two-step pyrolysis of melamine (C3H6N6) at 800°C for 2 h under vacuum conditions. X-ray diffraction (XRD) patterns strongly indicate that the synthesized sample
is g-C3N4. Transmission electron microscopy (TEM) and scanning electron microscopy (SEM) morphologies indicate that the product is
mainly composed of graphitic carbon nitride. The stoichiometric ratio of C:N is determined to be 0.72 by elemental analysis
(EA). Chemical bonding of the sample has been investigated by X-ray photoelectron spectroscopy (XPS) and Fourier transform
infrared spectroscopy (FTIR). Electron energy loss spectroscopy (EELS) verifies the bonding state between carbon and nitrogen
atoms. Optical properties of the g-C3N4 were investigated by PL (photoluminescence) measurements and UV–Vis (ultraviolet–visible) absorption spectra. We suppose
its luminescent properties may have potential application as component of optical nanoscale devices. Thermogravimetric analysis
(TGA) and differential thermal analysis (DTA) were also performed. 相似文献
14.
Properties of reactively sputtered W–B–N thin film as a diffusion barrier for Cu metallization on Si
L. C. Leu D. P. Norton L. McElwee-White T. J. Anderson 《Applied Physics A: Materials Science & Processing》2009,94(3):691-695
Thin films of W–B–N (10 nm) have been evaluated as diffusion barriers for Cu interconnects. The amorphous W–B–N thin films
were prepared at room temperature via reactive magnetron sputtering using a W2B target at various N2/(Ar + N2) flow ratios. Cu diffusion tests were performed after in-situ deposition of 200 nm Cu. Thermal annealing of the barrier stacks
was carried out in vacuum at elevated temperatures for one hour. X-ray diffraction patterns, sheet resistance measurement,
cross-section transmission electron microscopy images, and energy-dispersive spectrometer scans on the samples annealed at
500°C revealed no Cu diffusion through the barrier. The results indicate that amorphous W–B–N is a promising low resistivity
diffusion barrier material for copper interconnects. 相似文献
15.
Y. J. Wang C. M. Leung S. W. Or X. Y. Zhao H. S. Luo X. K. Lv Z. D. Zhang 《Applied Physics A: Materials Science & Processing》2009,97(1):201-204
We report an extrinsic magnetoelectric effect in composite laminates made by sandwiching one thickness-polarized 0.7Pb(Mg1/3Nb2/3)O3–0.3PbTiO3 (PMN–PT) piezoelectric single crystal plate between two length-magnetized, polymer-based pseudo-1–3 (Tb0.3Dy0.7)0.5Pr0.5Fe1.55 magnetostrictive composite plates. The laminates exhibit large magnetoelectric voltage coefficients (α
V
) of ∼0.17 V/Oe with a flat response for frequencies in excess of 40 kHz and of ∼2.97 V/Oe at the natural resonance frequency
of ∼65 kHz. The distinct advantages of the laminates include high magnetic field sensitivity, low Joule heating loss, wide
operating bandwidth, and low cost. 相似文献
16.
Y. P. Han J. L. Sun H. A. Ye W. Z. Wu G. Shi 《Applied physics. B, Lasers and optics》2009,94(2):233-237
In order to investigate the effect of pulse width and solvent on the nonlinear properties of metal nanostructures, silver
nanowires were fabricated in a direct current electric field (DCEF) using a solid-state ionic method and characterized by
transmission electron microscopy (TEM) and X-ray diffraction (XRD). The nonlinear refractive index (γ) of silver nanowires suspended in ethanol was measured using the Z-scan technique and laser radiation of various (femto-,
pico-, and nanosecond) pulse durations. Experimental results indicated that silver nanowires have obvious positive refractive
nonlinearities and γ (the Kerr-induced self-focusing) increases as the pulse duration increases from 7.4×10−8 cm2/GW at 110 fs to 1.6×10−4 cm2/GW at 8 ns, due to the additional influence of the atomic reorientational Kerr effect in the case of longer pulses. Due to
the solvent dependence of the nonlinear behavior of the silver nanowires, the nonlinear absorption and refraction of silver
nanowires suspended in de-ionized water are smaller than those of silver samples suspended in ethanol. The thermal nonlinearities
are insignificant in our experimental conditions. 相似文献
17.
Huanfu Zhou Hong Wang Minghui Zhang Xi Yao 《Applied Physics A: Materials Science & Processing》2009,95(2):513-516
A new Li2O–Nb2O5–TiO2 (LNT) ceramic with the Li2O:Nb2O5:TiO2 mole ratio of 5.5:1:7 was prepared by solid state reaction route. The phase and structure of the ceramic were characterized
by X-ray diffraction and scanning electron microscopy (SEM). The microwave dielectric properties of the ceramics were studied
using a network analyzer. The microwave dielectric ceramic has low sintering temperature (∼1075°C) and good microwave dielectric
properties of ε
r=42, Q×f=16900 GHz (5.75 GHz), and τ
f
=63.7 ppm/°C. The addition of B2O3 can effectively lower the sintering temperature from 1075 to 875°C and does not induce degradation of the microwave dielectric
properties. Obviously, the LNT ceramics can be applied to microwave low temperature-cofired ceramics (LTCC) devices. 相似文献
18.
Arvind Nautiyal K. C. Sekhar N. P. Pathak R. Nath 《Applied Physics A: Materials Science & Processing》2009,97(1):205-210
The composite films of cesium nitrate (CsNO3) and poly(vinyl alcohol) (PVA) with varying composition were prepared using the solvent cast method. The hysteresis loop
characteristics show optimum remnant polarization (P
r
) of 2.75 μC/cm2 at 50 wt.% composition. The field emission scanning electron microscope images show a nearly homogeneous distribution of
CsNO3 grains in the 50 wt.% composite film. The temperature dependence of the remnant polarization shows a diffused transition
temperature range from the ferroelectric to the paraelectric phase and this has been attributed to the reduced enthalpy. The
butterfly features of the dielectric constant–voltage (ε–V) characteristics have been attributed to polarization switching. 相似文献
19.
J. P. Xu X. Zou C. X. Li P. T. Lai C. L. Chan 《Applied Physics A: Materials Science & Processing》2009,94(2):419-422
Reactive cosputtering is employed to prepare high-permittivity HfTiO gate dielectric on n-Ge substrate. Effects of Ge-surface
pretreatment on the interface and gate leakage properties of the dielectric are investigated. Excellent performances of Al/HfTiO/GeO
x
N
y
/n-Ge MOS capacitor with wet–NO surface pretreatment have been achieved with a interface-state density of 2.1×1011 eV−1 cm−2, equivalent oxide charge of −7.67×1011 cm−2 and gate leakage current density of 4.97×10−5 A/cm2 at V
g
=1 V. 相似文献
20.
A. Povolotskiy T. Ivanova A. Manshina Y. Tver’yanovich Shien-Kuei Liaw Chu-Lin Chang 《Applied Physics A: Materials Science & Processing》2009,96(4):887-891
Er3+ clustering phenomenon in Ga–Ge–S chalcogenide system is studied using Raman spectroscopy. The Raman spectra from 10 to 500
cm−1 for glasses (100−y)[15Ga2S3–85GeS2]–yEr2S3 (y=0.08−5.00 mol. %) have been analyzed. To reveal the influence of the chemical composition on the glass structure the intensity
of the peak corresponding to Ge–Ge (Ga–Ga) homopolar bonds has been examined. The peak intensity increase with Er2S3 concentration change in the region 0<C(Er2S3)<2 mol. % has been interpreted in terms of the sulphur deficiency in the glass resulting in the formation of S3Ge–GeS3 (S3Ga-GaS3) structural units. The further increase in concentration beyond 2 mol. % reduces the sulphur deficiency, which can be attributed
to the formation of the ternary compound Er3GaS6. The structural units Er3GaS6 contain a large mol. fraction of Er3+ or, in other words, Er3+ clusters. The data obtained from the low-frequency Raman spectra (boson band) indicate strong variations of the medium-range
order (MRO) in the glasses induced by Er3+. The observed behavior of the MRO size (the correlation length) with increasing of Er2S3 concentration provides for additional evidence of the Er3+ clustering. 相似文献