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1.
Michal Novotn?? P??emysl Fitl Anna Krasilnikova Sytchkova Ji???- Bul?-?? Jan Lanaok Petr Pokorna David Najdek Jia Boan 《Central European Journal of Physics》2009,7(2):327-331
The effect of pulsed laser treatment of metal, and metal blacks, was studied. Gold and black gold thin films were fabricated
by thermal evaporation of gold in a vacuum and nitrogen atmosphere respectively. Black gold films were grown in a nitrogen
atmosphere at pressures of 200 Pa and 300 Pa. UV pulsed laser radiation (λ = 266 nm, τ = 4 ns), with fluence ranging from 1 mJ·cm−2 to 250 mJ·cm−2 was used for the film treatment in a vacuum and nitrogen atmosphere. The nitrogen pressure was varied up to 100 kPa. Surface
structure modifications were analyzed by optical microscopy, atomic force microscopy (AFM) and scanning electron microscopy
(SEM). Energy dispersive X-ray spectroscopy (EDX) was used for chemical characterization of the samples. A significant dependence
of the film optical and structural properties on laser treatment conditions (laser fluence, ambient pressure and number of
applied pulses) was found. The threshold for observable damage and initiation of changes of morphology for gold and black
gold surfaces was determined. Distinct modifications were observed for fluences greater than 106 mJ·cm−2 and 3.5 mJ·cm−2 for the gold and black gold films respectively. Absorbtivity of the black gold film is found to decrease with an increase
in the number of laser pulses. Microstructural and nanostructural modifications after laser treatment of the black gold film
were observed. EDX analysis revealed that no impurities were introduced into the samples during both the deposition and laser
treatment.
相似文献
2.
An investigation was made of the formation of beams of fast electrons in different gases at pressures of from 0.01 to 100 kPa. Plots were made of the dependences of the electron beam currents Ie on the gas pressure p for different electric field strengths E. The dependences Ie=f(p) for air were found to intersect the similar dependences for other gases (helium, nitrogen, neon, and argon) at a pressure of p=10.6 kPa and for E=2.3·105 V·cm–1. This fact is explained by the influence of the oxygen ions and atoms on the electron beam formation process. Another experimental result, the appearance of a minimum in the dependences Ie=f(p) for all gases, is explained by defocusing of the electron beam, the appearance of a reverse current, and magnetic neutralization of the beam. Electron beams were obtained having a pulse duration of 15–20 nsec and a current of 105-106 A/m2 per unit cathode area.Institute of Atmospheric Optics, Siberian Branch, Russian Academy of Sciences. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 6, pp. 67–70, June, 1993. 相似文献
3.
We fabricate a transparent glass ceramic contains magnesium-aluminum spinel nanocrystallites doped with Co2+ ions. The ground-state and excited-state absorption cross section of this glass ceramic at 1.54 μm are estimated to be (2.8
± 0.3) × 10−19 cm2 and (4.8 ± 0.5) × 10−20 cm2, respectively. For the first time, the passively Q-swithched operation of LD pumped 1.54 μm microchip Yb3+/Er3+ glass laser is realized with transparent glass ceramic as saturable absorber. The Q-switched pulses of 3.846 kHz in repetition
rate, 6.2 ns in duration and 6.3 μJ in energy are obtained. At last, the dependences of pulse width and repetition rate on
pump power are also investigated. 相似文献
4.
The mechanism of generation of terahertz radiation upon irradiation of a target by short (∼ 0.1 ns) high-intensity laser pulses
(I ∼ 1018−1019 W cm−2) is investigated by numerical simulation using the relativistic electromagnetic PIC code. The interaction of such a pulse
with the target, a plasma is formed on it. Electrons emitted from the plasma form a virtual cathode whose oscillations are
determined not only by their self-field, but also by the field of ions of the plasma. Generation occurs in the terahertz frequency
range with the efficiency thrice as high as in the absence of ions (i.e., with traditional reditron generation mechanism).
The explanation for this effect is also given. 相似文献
5.
M. Ghoranneviss A. Shokouhy M. M. Larijani S. H. Haji Hosseini M. Yari A. Anvari M. Gholipur Shahraki A. H. Sari M. R. Hantehzadeh 《Pramana》2007,68(1):135-140
This work presents the results of a low-energy nitrogen ion implantation of AISI 304 type stainless steel (SS) at a moderate
temperature of about 500°C. The nitrogen ions are extracted from a Kauffman-type ion source at an energy of 30 keV, and ion
current density of 100 μA cm−2. Nitrogen ion concentration of 6 × 1017, 8 × 1017 and 1018 ions cm−2, were selected for our study. The X-ray diffraction results show the formation of CrN polycrystalline phase after nitrogen
bombardment and a change of crystallinity due to the change in nitrogen ion concentration. The secondary ion mass spectrometry
(SIMS) results show the formation of CrN phases too. Corrosion test has shown that corrosion resistance is enhanced by increasing
nitrogen ion concentration.
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6.
This paper reports on a study of the electron-stimulated desorption of negative oxygen ions from the O/Ru surface, which represents
an additional factor responsible for the destruction of the protective oxide layer of the mirrors used in ultraviolet lithography.
The cross section of degradation of the O/Ru layer due to the electron-stimulated desorption of the O+ and O− ions and the O atoms has been found to be 1.6 × 10−19 cm2. A comparison of the dependences of the electron-stimulated desorption yield of O+ and O− ions on the incident electron energy E with the ionization cross section of the adsorbate core level σ
O2s
(E) has revealed that the ionization of the O 2s level is the main channel of the electron-stimulated desorption of O− ions. 相似文献
7.
L. Kovács M. Mazzera E. Beregi R. Capelletti 《Applied physics. B, Lasers and optics》2009,94(2):273-277
Several weak absorption bands have been observed in the optical absorption spectra of pure and rare-earth-doped YAl3(BO3)4 single crystals in the 3350– 3650 cm−1 wave number region. Two of them, peaking at about 3377 cm−1 and 3580 cm−1 in the 8 K spectra, appear in most of the samples. They are tentatively attributed to the stretching mode of OH− ions incorporated in the crystal during the growth. An additional absorption band at about 5250 cm−1 at 8 K has also been detected in almost all samples. The temperature and polarization dependences of these bands, and their
possible origin, are discussed. 相似文献
8.
A. S. Shcheulin T. S. Semenova L. F. Koryakina M. A. Petrova A. E. Angervaks A. I. Ryskin 《Optics and Spectroscopy》2011,110(4):617-623
The mechanism of the additive coloring of calcium fluoride crystals, both pure and doped with I- and III-group elements, has
been investigated. The coloring rate and intensity and the dependences of these parameters on the experimental conditions,
vapor mixture pressure, and temperature have been experimentally determined. It is shown that the concentration of anion vacancies/electrons
that can be introduced into crystals is in the range of 1017–1018 cm−3; in crystals with a high concentration of rare earth ions, the limiting concentration can be an order of magnitude higher. 相似文献
9.
We study the optical-gain characteristics of a Si-based MQW laser, in which the active region has 20 Si0.15Ge0.621Sn0.229 quantum wells separated by 20 Si0.637Ge0.018Sn0.345 barriers. We reach a maximum optical gain of 2300 cm?1 with an estimated carrier concentration of 5·1018 cm?3, which is equivalent to the transparent current density equal to 0.5 kA/cm2. Furthermore, we discuss the optical confinement factor and modal gain. The modal gain depends sensitively on the number of the quantum wells (QWs), and this fact restricts the optical confinement factor. The modal gain of the model we proposed can reach 1500 cm?1 at the injection current density equal to 3 kA/cm2. We hope that our results show the possibility to obtain a Si-based near-infrared laser. 相似文献
10.
The method of nitriding of metals in an electron beam plasma is used to change the current density and energy of nitrogen
ions by varying the electron beam parameters (5–20 A, 60–500 eV). An electron beam is generated by an electron source based
on a self-heated hollow cathode discharge. Stainless steel 12Kh18N10T is saturated by nitrogen at 500°C for 1 h. The microhardness
is measured on transverse polished sections to obtain the dependences of the nitrided layer thickness on the ion current density
(1.6–6.2 mA/cm2), the ion energy (100–300 eV), and the nitrogen-argon mixture pressure (1–10 Pa). The layer thickness decreases by 4–5 μm
when the ion energy increases by 100 V and increases from 19 to 33 μm when the ion current density increases. The pressure
dependence of the layer thickness has a maximum. These results are in conflict with the conclusions of the theory of the limitation
of the layer thickness by ion sputtering, and the effective diffusion coefficient significantly exceeds the well-known reported
data. 相似文献
11.
Minority carrier lifetimes in nitrogen implanted GaAs1-x
P
x
(x=0.4; 0.65) were measured at 77K by an optical phase shift method as a function of nitrogen dose and annealing temperature
in order to investigate the dependence of the lifetime on the concentration of nitrogen isoelectronic traps. A large increase
in the lifetime was observed after nitrogen implantation followed by annealing at and above 800°C. The maximum lifetimes were
22ns for GaAs0.35P0.65 and 6.7 ns for GaAs0.6P0.4. They were obtained by implantation to a dose of 5×1013 cm−2 in GaAs0.35P0.65 and 1013 cm−2 in GaAs0.6P0.4. The lifetime after nitrogen implantation followed by annealing was longer by a factor of 6–7 than that of the unimplanted
sample. 相似文献
12.
The demonstration of a 69.8?nm laser on 3p 3P2 - 3s 1P1 (J=2-1) transition of Ne-like Ar pumped by capillary discharge is reported in this Letter. A main current of 12?kA with rise time of 43?ns was chosen to generate the plasma in a 35?cm long capillary filling with pressure of Ar as low as 11?Pa, resulting in a gain coefficient of 0.34?cm(-1) and gain-length product of 11 at 69.8?nm. Also observed is a weak laser on 3p 3D2 - 3s 3P1 (J=2-1) transition of Ne-like Ar at 72.6?nm in the same condition. In addition, multiwavelength lasing at 46.9, 69.8, and 72.6?nm was simultaneously realized in a capillary discharge plasma column, conditioning the pressure of Ar to 13?Pa. 相似文献
13.
Characteristics of a Ne-like Ar 46.9-nm soft X-ray laser in capillary discharge at a low Ar pressure
A capillary discharge-pumped Ne-like Ar 46.9-nm soft X-ray laser at a low Ar pressure (28–46 Pa) is proven. To our knowledge, this is the first time an XRD laser output in the condition of the low threshold of a main-current pulse spike (20–21 kA) is demonstrated. The Al2O3 ceramic capillary tube is 20 cm in length (Mo electrode is 4 cm in length) and 3 mm in diameter. The maximum laser energy of the precalibrated XRD is 3.5 μJ. The maximum gain coefficient g = 0.46 cm?1, the maximum gain-length product is 8.28, the beam divergence is 5.4 mrad, and the laser pulse width is 1.65 ns. In addition, the results show that the laser plasma column became difficult to Z-pinch with a increasing Ar pressure, its Z-pinching state of a higher Ar pressure fluctuates more intensely than that of a lower pressure by analyzing the scattering of the delay time between the pre-and main-current pulse. 相似文献
14.
建立了计算69.8nm激光增益系数的理论模型,根据实验参数,计算了在主脉冲电流为12 kA时,69.8nm激光增益系数最大值为0.32 cm~(-1).理论模拟了不同初始气压下增益系数在毛细管径向上的分布情况.对理论结果的分析表明,最佳的初始气压在12—14 Pa范围内,此时69.8nm激光增益系数的极值最大.实验上,利用毛细管放电装置和罗兰光谱仪,测量了不同气压下的69.8nm激光强度,实验确定的最佳气压为16 Pa,与理论结果相近.此外,实验测量的增益系数(0.4 cm~(-1))略高于理论计算的增益系数(0.32 cm~(-1)). 相似文献
15.
P. Vrba M. Vrbova N. A. Bobrova P. V. Sasorov 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2009,54(2):481-486
Pinching discharge in non-ablative and ablative capillaries filled by boron vapors is studied. The aim is to find out conditions
for lasing at Balmer alpha transition of hydrogen-like boron ions B4+ (λ= 26.23 nm). The primary pumping process under consideration is a three-body collisional recombination, which takes place
in non-stationary underheated plasma during the pinch expansion stage. The results of Z-pinch computer modeling including
the plasma kinetics and gain evaluation are compared for two different quarter periods of electrical current passing through
the capillary. 相似文献
16.
V. V. Borovkov K. I. Almazova E. P. Volkov V. G. Kornilov C. Yu. Kornilov V. D. Selemir D. A. Tolshmyakov A. A. Khizhnyakov V. I. Chelpanov 《Technical Physics》2003,48(4):415-420
A plasma injector with pulsed gas filling is investigated experimentally. Interferometric measurements of the formation dynamics
of the plasma channel are carried out. Under optimal operating conditions, the injector is capable of producing a plasma channel
4 cm in diameter with an electron density of ∼1017 cm−3. The effect of the cathode diameter of the plasma opening switch on the conductivity of the plasma channel is studied. It
is shown that the current flowing through the plasma channel of a single injector attains 400 kA. 相似文献
17.
The results of experimental investigations and an analysis of the temperature dependences of the thermally stimulated depolarization
current are presented for zinc-oxide ceramics suitable for use in high-voltage varistors. A model for the depolarization phenomena
is proposed that takes into account charge exchange on localized electronic states on both sides of the intercrystallite potential
barrier. The model is used to obtain estimates of the ionization energy and density of shallow (∼0.07 eV, 1×1017 cm−3) and deeper (∼0.2 eV, 1×1018 cm−3) bulk levels and surface-localized levels (∼0.1 eV, 1×1013 cm−2).
Zh. Tekh. Fiz. 67, 60–63 (October 1997) 相似文献
18.
We report here an experimental study of the ionic keV X-ray line emission from magnesium plasma produced by laser pulses of
three widely different pulse durations (FWHM) of 45 fs, 25 ps and 3 ns, at a constant laser fluence of ∼1.5 × 104 J cm − 2. It is observed that the X-ray yield of the resonance lines from the higher ionization states such as H- and He-like ions
decreases on decreasing the laser pulse duration, even though the peak laser intensities of 3.5 × 1017 W cm − 2 for the 45 fs pulses and 6.2 × 1014 W cm − 2 for the 25 ps pulses are much higher than 5 × 1012 W cm − 2 for the 3 ns laser pulse. The results were explained in terms of the ionization equilibrium time for different ionization
states in the heated plasma. The study can be useful to make optimum choice of the laser pulse duration to produce short pulse
intense X-ray line emission from the plasma and to get the knowledge of the degree of ionization in the plasma. 相似文献
19.
A capillary discharge 46.9 nm Ne-like Ar laser is achieved with peak current of 20–23 kA. The variation of laser pulse duration
with initial Ar pressure and rise-time of main current is reported. Measurements show that the laser pulse durations slightly
increase with the increased pressure and increased rise-time of current. A comparison of the experimental results with the
calculation of snow-plow model indicates that the increase of laser pulse duration is the result of decreased Z-pinch velocity
at the pinch time when the radius of plasma is minimal. 相似文献
20.
Ramesh Narayan 《Pramana》1979,13(5):559-570
Ionic radii and compressibilities have been calculated for a number of monovalent and divalent ions and radicals on the basis
of the compressible ion theory. In this theory, the compression energy of an ion is given as a two-parameter function of its
radius,A exp (−r/p), the radius and compressibility of the ion being monotonically decreasing functions of the compressing force acting on it.
Choosing a standard force reflecting the average environment in the alkali halides, univalent radii and compressibilities
have been calculated. This is the first theory to estimate ionic compressibilities. The values show systematic trends among
groups of related ions. Anions are found to be significantly more compressible than cations (e.g., the compressibilities of
Ca++, K+, Cl− and S− − are respectively 0.8530, 1.342, 2.952 and 5.150 × 10−12 cm2/ dyne). Multivalent or ‘crystal’ radii and compressibilities have also been calculated by scaling the standard force by the
square of the ionic charge. The calculated ionic radii are closer to experimental values than the classical empirical radii. 相似文献