共查询到20条相似文献,搜索用时 31 毫秒
1.
D. A. Romanov E. A. Budovskikh V. E. Gromov 《Journal of Surface Investigation: X-ray, Synchrotron and Neutron Techniques》2011,5(6):1112-1117
The surface topography and structure of copper layers exposed to multiphase plasma jets of products of electrical explosion
of molybdenum and copper foils are studied using profilometry and scanning electron and light microscopy. Such treatment allows
deposition of either layered coatings or alloyed composite layers. It is found that the surface layer roughness parameter
is R
a
= 3.2−4.0 μm. The thickness of some copper and molybdenum layers of coatings is 15–20 μm. Electroexplosive alloying produces
layers 25 μm thick. Sizes of copper inclusions in the molybdenum matrix near the surface of such layers vary from 30 nm to
1–2 μm. 相似文献
2.
Layered thick-film composites containing one lead zirconate titanate (PZT) layer, one nickel zinc ferrite (NZF) layer, two
PZT-NZF layers, or three PZT-NZF-PZT layers each 40–50 μm thick are prepared. The layers are applied by screen printing on
a ceramic aluminum oxide substrate with a preformed contact (conducting) layer. The dielectric properties of the composites
are studied in the temperature interval 80–900 K and the frequency interval 25 Hz-1 MHz. Polarized samples exhibit piezoelectric,
pyroelectric, and magnetoelectric effects. In tangentially magnetized two- and three-layer composites, the magnetoelectric
conversion factor equals 57 kV/(m T) at low frequencies and reaches 2000 kV/(m T) at the mechanical resonance frequency. 相似文献
3.
V. P. Rotshtein Yu. F. Ivanov A. B. Markov D. I. Proskurovskii K. V. Oskomov V. V. Uglov S. N. Dub Y. Pauleau I. A. Shulepov 《Russian Physics Journal》2005,48(12):1221-1228
The surface topography, chemical composition, microstructure, nanohardness, and tribological characteristics of a Cu (film,
512 nm)-stainless steel 316 (substrate) system subjected to pulsed melting by a low-energy (20–30 keV), high-current electron
beam (2–3 μs, 2–10 J/cm2) were investigated. The film was deposited by sputtering a Cu target in the plasma of a microwave discharge in argon. To
prevent local exfoliation of the film due to cratering, the substrate was multiply pre-irradiated with 8–10 J/cm2. On single irradiation, the bulk of the film survived, and a diffusion layer containing the film and substrate components
was formed at the interface. The thickness of this layer was 120–170 nm irrespective of the energy density. The diffusion
layer consisted of subgrains of γ-Fe solid solution and nanosized particles of copper. In the surface layer of thickness 0.5–1 μm, which included the copper
film quenched from melt and the diffusion layer, the nanohardness and the wear resistance nonmonotonicly varied with energy
density, reaching, respectively, a maximum and a minimum in the range 4.3–6.3 J/cm2. As the number of pulsed melting cycles was increased to five in the same energy density range, there occurred mixing of
the film-substrate system and a surface layer of thickness ∼2 μm was formed which contained ∼20 at. % copper. Displacement
of the excess copper during crystallization resulted in the formation of two-phase nanocrystal interlayers separating the
γ-phase grains.
__________
Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 12, pp. 6–13, December, 2005. 相似文献
4.
We have theoretically investigated the thermal characteristics of double-channel ridge–waveguide InGaAs/InAlAs/InP quantum
cascade lasers (QCLs) using a two-dimensional heat dissipation model. The temperature distribution, heat flow, and thermal
conductance (G
th) of QCLs were obtained through the thermal simulation. A thick electroplated Au around the laser ridges helps to improve
the heat dissipation from devices, being good enough to substitute the buried heterostructure (BH) by InP regrowth for epilayer-up
bonded lasers. The effects of the device geometry (i.e., ridge width and cavity length) on the G
th of QCLs were investigated. With 5 μm thick electroplated Au, the G
th is increased with the decrease of ridge width, indicating an improvement from G
th=177 W/K⋅cm2 at W=40 μm to G
th=301 W/K⋅cm2 at W=9 μm for 2 mm long lasers. For the 9 μm×2 mm epilayer-down bonded laser with 5 μm thick electroplated Au, the use of InP
contact layer leads to a further improvement of 13% in G
th, and it was totally raised by 45% corresponding to 436 W/K⋅cm2 compared to the epilayer-up bonded laser with InGaAs contact layer. It is found that the epilayer-down bonded 9 μm wide BH
laser with InP contact layer leads to the highest G
th=449 W/K⋅cm2. The theoretical results were also compared with available obtained experimentally data. 相似文献
5.
N. K. Vdovicheva M. A. Galin A. N. Reznik I. A. Shereshevsky 《Bulletin of the Russian Academy of Sciences: Physics》2012,76(2):145-148
A technique for the profiling of free carrier concentration N(z) in semiconductors, based on the near-field measurements in microwave frequency range, is proposed. A high accuracy in retrieving
the N(z) function with characteristic spatial scales of 10–100 nm using 2–3 probes with apertures of 3–15 μm is demonstrated. 相似文献
6.
High-resolution photorefractive gratings in nematic liquid crystals sandwiched with photoconductive polymer film 总被引:1,自引:1,他引:0
F. Yao Y. Pei Yu Zhang J. Zhang C. Hou X. Sun 《Applied physics. B, Lasers and optics》2008,92(4):573-576
Photorefractive gratings with high grating resolution were observed in the 20 μm thick low-molar-mass nematic liquid crystal
(NLC) cell with a separate photoconductive (PC) poly(N-vinylcarbazole) layer. An orientational grating with a grating spacing of 1.9 μm was produced. It is believed that a space–charge
field with small fringe spacing forms in the PC layer and its evanescent component penetrates into the NLC layer. The penetrated
evanescent field drives the NLC to reorient, and consequently the orientational grating forms. The model indicates that the
modulated field exists in several hundred nanometers near the surface, and thus the orientational grating is not full of the
NLC film, which is consistent with the observed phenomena of the multiple diffractions. Besides, asymmetric two-beam coupling
of 11.2% was achieved for the grating with a grating spacing of 1.9 μm, and a net gain coefficient of larger than 62 cm−1 was obtained. 相似文献
7.
D.C. Meyer A. Klingner Th. Holz P. Paufler 《Applied Physics A: Materials Science & Processing》1999,69(6):657-659
After aging at room temperature for several months W/C multilayers (20 periods, single layer thicknesses in the nanometer
range) grown on Si-(111) substrates by pulsed laser deposition (PLD) developed homogeneously wrinkled surfaces. Their structures
were studied by optical microscopy, atomic force microscopy and X-ray diffractometry. Typical dimensions of debonded areas
are some 100 μm in length, about 40 μm in width and 2–3 μm in height. The formation of wrinkles is accompanied by an increase
in the free surface by 1–2%. Stress relaxation is considered the driving force of this phenomenon.
Received: 26 July 1999 / Accepted: 29 July 1999 / Published online: 16 September 1999 相似文献
8.
Recombination zone and efficiency in bipolar single layer light-emitting devices: a numerical study 总被引:1,自引:0,他引:1
Ying-Quan Peng Qing-Sen Yang Hong-Wei Xing Xun-Shuan Li Jian-Ting Yuan Chao-Zhu Ma Run-Sheng Wang 《Applied Physics A: Materials Science & Processing》2008,93(2):559-564
The efficiency of organic light-emitting devices (OLEDs) is closely related to the position and width of recombination zone
(RCZ) in the emission layer. Based on the drift–diffusion theory of carrier motion in semiconductors, we developed a numerical
model for the position and width of the RCZ in bipolar single layer OLEDs. The calculation results show that for a given operation
voltage, the position and width of the RCZ are determined by the mobility difference of electrons and holes, and the energy
barrier at the two contacts. When the anode and cathode contact are both ohmic, then RCZ will be near the electrode, from
which the low-mobility carriers are injected, and the smaller the mobility difference, the wider the RCZ, and the width of
RCZ will be maximal when the mobility of holes and electrons are equal. When the anode contact is Schottky, while the cathode
contact is ohmic, then the position and width of RCZ will be determined by both the mobility difference and hole–injection
energy barrier. When μ
p<μ
n, the RCZ will be at the anode side. When μ
p>μ
n, then RCZ will move away from the anode and become wider, with the increase of the hole injection barrier. For a given hole–injection
barrier and mobility of holes and electrons, the position and width of RCZ change with the applied voltage. 相似文献
9.
The present work is devoted to the development of the method of laser photothermal radiometry with a view to increasing its
spatial resolution over the depth of the specimen when surface layers of the substance of thickness about 1 μm or less are
to be investigated. As an example, results of an investigation of radiation absorption in the surface layer of a lithium niobate
crystal are presented. The absorption index measured at a wavelength of 1.08 μm was ∼0.6 cm−1.
“Polyus” Research Institute, 3, Vernadskii Ave., Moscow, 117342, Russia. Translated from Zhurnal Prikladnoi Spektroskopii,
Vol. 64, No. 1, pp. 82–84, January–February, 1997. 相似文献
10.
R. R. Vardanyan V. K. Dallakyan U. Kerst C. Boit 《Journal of Contemporary Physics (Armenian Academy of Sciences)》2012,47(2):73-79
The different empirical models of light absorption in silicon by free charge carriers in near-infrared and infrared regions
are analyzed. An improved empirical model for free carrier absorption in silicon is developed. Results are obtained over the
wavelength range from 0.9 μm to 6 μm for n-type, and from 0.9 μm to 8 μm for p-type silicon. The new model is assessed ed by R
2 parameter and the sufficient fitting of the experimental data is presented. 相似文献
11.
Manuj Nahar Ignacio F. Gallardo Kristofer L. Gleason Michael F. Becker John W. Keto Desiderio Kovar 《Journal of nanoparticle research》2011,13(8):3455-3464
A continuous aerosol process has been studied for producing nanoparticles of oxides that were decorated with smaller metallic
nanoparticles and are free of organic stabilizers. To produce the oxide carrier nanoparticles, an aerosol of 3–6 μm oxide
particles was ablated using a pulsed excimer laser. The resulting oxide nanoparticle aerosol was then mixed with 1.5–2.0 μm
metallic particles and this mixed aerosol was exposed to the laser for a second time. The metallic micron-sized particles
were ablated during this second exposure, and the resulting nanoparticles deposited on the surface of the oxide nanoparticles
producing an aerosol of 10–60 nm oxide nanoparticles that were decorated with smaller 1–5 nm metallic nanoparticles. The metal
and oxide nanoparticle sizes were varied by changing the laser fluence and gas type in the aerosol. The flexibility of this
approach was demonstrated by producing metal-decorated oxide nanoparticles using two oxides, SiO2 and TiO2, and two metals, Au and Ag. 相似文献
12.
A near-field scanning optical microscope (NSOM), which we built, is used to investigate 1–5-μm wide stripes with a 10-nm thick
layer—a quantum well — on a GaAs surface. A map of the photoluminescence intensity is obtained synchronously with the topographic
profile of the structures. The measured spatial distribution of the photoluminescence intensity is described satisfactorily
in a model that takes into account carrier diffusion in the layer and the existence of a region with a short carrier lifetime
near the side boundaries of the layer.
Pis’ma Zh. éksp. Teor. Fiz. 63, No. 7, 523–527 (10 April 1996) 相似文献
13.
T. A. Alekhova V. Ya. Shklover N. A. Zagustina N. V. Shvyndina A. D. Plotnikov A. L. Vasil’ev 《Journal of Surface Investigation: X-ray, Synchrotron and Neutron Techniques》2010,4(5):747-753
The surfaces of AMg6 (aluminum-magnesium) alloy samples that have passed accelerated biocorrosion tests have been investigated
in a Quanta-3D scanning electron microscope. The alloy samples have been treated with the Ulocladium botrytis Preuss fungus, which is an active destructive fungus and was previously extracted on surfaces of the International Space Station.
Biocorrosion pits 2–10 μm in diameter, cavities the depths of which can reach 70–250 μm depth, and spots of modified color
are found to be the most typical defects. The surfaces of large cavities consist of faceted cubic particles that are formed
when the acid products of fungus metabolism interact with the alloy surface. The particles have an average size of 30 μm,
which is close to the size of alloy grains. The microstructure of a biocorrosion layer has been investigated in a Quanta-3D
microscope with the use of a focused Ga+ ion beam. The samples of 12-μm-wide transverse slices are obtained near large cavities and investigated in a Tecnai G230ST transmission electron microscope. The X-ray microanalysis of the defective layer has revealed the high concentration of
oxygen in this layer. Obtained images indicate that the corrosion cavity surface has a complex porous structure. 相似文献
14.
Precision structural studies of layering of perfect crystals Bi
2
Sr
2−x
La
x
CuO
6+δ
(BSLCO) ∼ 10 μm thick, grown by free growth within crystallized melt cavities, detect a macrolayer structure with each layer up to 0.1 μm thick. In the lanthanum concentration range x = 0.6−0.8, only modulation layering is observed. In the concentration range
x = 0.3−0.5, either layers with two different lanthanum concentrations, but with the same modulated superlattice type, or
layers with the same lanthanum concentration, but with two different modulated superlattice types are observed. At low lanthanum
concentrations (0 < x < 0.26), layering into two or even three layer types with different lanthanum concentrations are almost always observed.
Modulation suppression when lead is added to a mixture leads to the same layered structure of samples, but with appreciable
variations in lattice parameters in the ab plane of individual layers and a and b axis rotation by several degrees with respect to each other in these layers. Thus, the superlattice in BSLCO single crystals
stabilizes their composition in the ab plane, and inevitable variations in growth conditions lead to the layered structure of such crystals.
Original Russian Text ? V.P. Martovitsky, A. Krapf, 2008, published in Kratkie Soobshcheniya po Fizike, 2008, Vol. 35, No.
3, pp. 29–38. 相似文献
15.
S. A. Dyakov E. V. Astrova T. S. Perova S. G. Tikhodeev N. A. Gippius V. Yu. Timoshenko 《Journal of Experimental and Theoretical Physics》2011,113(1):80-85
The reflection spectra of grooved silicon structures consisting of alternating silicon walls and grooves (air channels) with
a period of a = 4–6 μm are studied experimentally and theoretically in the mid-IR spectral range (2–25 μm) upon irradiation of samples
by normally incident light polarized along and perpendicular to silicon layers. The calculation is performed by the scattering
matrix method taking into account Rayleigh scattering losses in a grooved layer by adding imaginary parts to the refractive
indices of silicon and air in grooved regions. The experimental and calculated reflection spectra are in good agreement in
the entire spectral range studied. The analysis of experimental and calculated spectra gave close values of the effective
refractive indices and birefringence of the studied structures in the long-wavelength spectral region. The values calculated
in the effective medium model in the long-wavelength approximation (λ ≫ a) gave considerably understated values. The obtained results confirm the efficiency of the scattering matrix method for describing
the optical properties of silicon microstructures. 相似文献
16.
Experimental performance parameters of Hg implanted Hg1−x
Cd
x
Te photovoltaic detectors are analyzed. At 77K, for 8–14 μm band, a comparison is made between performances and theoretical
ultimate diffusion limits in low frequency direct detection. Experimental features are well-explained by a model based on
the Auger band-to-band process for carrier recombination. Peak detectivities exceeding 1011 cm Hz1/2W−1, external quantum efficiencies as high as 90%, and zero-bias resistance-area products better than 1 Ω·cm2 have been achieved in devices with 12 μm cutoff wavelengths. In the 3–5 μm band performances are far from the diffusion limit.
Notwithstanding, at 77K zero-bias resistance-area products are better than 104Ω·cm2 and detectivities of the order of 1012 cm Hz1/2W−1 were observed at 5 μm.
Predominant generation-recombination contribution are present at room temperature in 1–1.3 μm photodiodes whose detectivities,
primarily limited by the Johnson noise, at 1.3 μm are higher than 1011 cm Hz1/2W−1 at 300 K.
The high frequency response of the photodiodes is also discussed. Response times as low as 0.5 ns are reached despite some
limitations arising from the implanted layer sheet resistance.
Work supported by CNR-CISE contract No. 73.01435. 相似文献
17.
A. G. Rousskikh A. V. Shishlov A. S. Zhigalin V. I. Oreshkin S. A. Chaikovsky R. B. Baksht 《Technical Physics》2010,55(11):1619-1627
The results of the experiments on the formation of a plasma emitter with small spatial dimensions for pulsed radiography in
the soft X-ray spectral range are presented. Emitting hot plasma was formed as a result of compression of the plasma jet by
a current pulse with amplitude I
m
= 215 kA and rise time T
fr = 200 ns. For the jet formation, we used a plasma gun based on the arc discharge (I
m
= 8.5 kA and T
fr = 6 μs) initiated by breakdown over the surface of a dielectric in vacuum. The experiments were carried out with aluminum,
tin, copper, and iron plasma jets. A single emitter, i.e., point Z-pinch (PZ-pinch), was formed when an interelectrode gap of a high current generator of 1.3–1.5 mm was used. The smallest spatial dimensions
of the emitting region were obtained with the use of aluminum and tin. For a tin jet, the diameter of the emitting region
was 7 ± 2 μm and its height was 17 ± 2 μm. The emission pulse duration at half-height was 2–3 ns. The total emission yield
per pulse in the spectral range 1.56–1.90 keV was 30–50 mJ for the aluminum pinch and 10–30 mJ for the tin pinch. The developed
method makes it possible to carry out radiographic examination of microobjects (including biological ones) 1–1000 μm in thickness,
with spatial (10–20 μm) and time (2–3 ns) resolution. 相似文献
18.
K. V. Kalinina S. S. Molchanov N. D. Stoyanov A. P. Astakhova Kh. M. Salikhov Yu. P. Yakovlev 《Technical Physics》2010,55(2):258-263
An optical method for measuring the water and oil content using mid-IR (1.6–2.4 μm) LEDs and a wideband photodiode is suggested
for the first time. This method is developed based on the absorption spectra of pure water, dewatered oil, and water—oil emulsions
(cut oil) with different content of water and uses 10 types of LEDs in the spectral range 1.6–2.4 μm. It is shown that pure
water heavily absorbs the LED radiation in the spectral range 1.85–2.05 μm, oil absorbs in the range 1.67–1.87 μm, and the
LED radiation with a maximum at 2.20 μm is equally weakly absorbed by water and oil. An optical cell of the water-and-oil
analyzer is designed on the basis of a three-element diode array with radiation maxima at 1.65 (detection of oil), 1.94 (detection
of water), and 2.2 μm (reference signal) wideband photodiode covering the spectral range 1.3–2.4 μm. A calibration curve is
derived that represents the dependence of the water concentration in oil on the amplitude of the reduced signal obtained by
processing three signals from the LEDs. This optical method of measuring the water content in oil underlies a portable analyzer
making possible online measurements directly in an oil well. 相似文献
19.
The viscose flow and microstructure formation of Fe-Cu peritectic alloy melts are investigated by analyzing the velocity and
temperature fields during rapid solidification, which is verified by rapid quenching experiments. It is found that a large
temperature gradient exists along the vertical direction of melt puddle, whereas there is no obvious temperature variation
in the tangent direction of roller surface. After being sprayed from a nozzle, the alloy melt changes the magnitude and direction
of its flow and velocity rapidly at a height of about 180 μm. The horizontal flow velocity increases rapidly, but the vertical
flow velocity decreases sharply. A thermal boundary layer with 160–300 μm in height and a momentum boundary layer with 160–240
μm in thickness are formed at the bottom of melt puddle, and the Reynolds number Re is in the range of 870 to 1070 in the
boundary layer. With the increase of Re number, the cooling rate increases linearly and the thickness of thermal boundary
layer increases monotonically. The thickness of momentum boundary layer decreases slowly at first, then rises slightly and
decreases sharply. If Re < 1024, the liquid flow has remarkable effects on the microstructure formation due to dominant momentum
transfer. The separated liquid phase is likely to form a fiber-like microstructure. If Re>1024, the heat transfer becomes
dominating and the liquid phase flow is suppressed, which results in the formation of fine and uniform equiaxed microstructures.
Supported by the National Natural Science Foundation of China (Grant Nos. 50121101 and 50395105) 相似文献
20.
Yoshiteru Amemiya Tomohiro Tokunaga Yuichiro Tanushi Shin Yokoyama 《Optical Review》2009,16(3):247-251
Electric-field drive optical modulators using a Si ring resonator were fabricated on silicon-on-insulator (SOI) wafers. The
fabricated resonators consisted of Si waveguides with width and thickness of 1.0 and 0.3 μm, respectively. In order to induce
the linear electro-optic (EO) effect in the Si core layer, the strain was applied by covering the layer with Si3N4 film (0.26 μm thick) deposited by low pressure chemical vapor deposition (LPCVD) at 750 °C. The vertical electric-field was
applied to the Si waveguide through the top and bottom cladding layers, and the optical output from the drop port at the resonance
wavelength was measured. At a wavelength of 1501.6 nm, the optical modulation of 33% was obtained at 200V (electric-field
at the silicon surface ∼3 × 105 V/cm, nearly the breakdown field). The resonance wavelength was shifted toward the short wavelength side by applying both
positive and negative voltages, this shift was explained by carrier concentration modulation. The linear EO effect in the
Si core layer was not observed, presumably because the strain in the Si core layer was too small. 相似文献