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1.
The electromagnetic and geometric characteristics of electron beams generated by molybdenum cathodes illuminated by an excimer
laser are reported. To determine the electromagnetic characteristics, a fast Rogowski coil was utilized, while the geometric
characteristics were performed by a suitable slit–slit meter system. During the experiment the laser spot on the cathode was
fixed to 4 mm2. The maximum output current (370 mA) was reached with 0.5 mJ laser energy and 50 kV accelerating voltage. In these conditions
the electron beam normalized emittance was 6 (π mm mrad) calculated at 80% level current density. The laser used in this experiment
was a singular excimer laser (KrCl) operating in the NUV range.
Received: 22 March 2000 / Revised version: 11 July 2000 / Published online: 5 October 2000 相似文献
2.
The laser-produced ion stream may be attractive for direct ultra-low-energy ion implantation in thin layer of semiconductor for modification of electrical and optical properties of semiconductor devices. Application of electrostatic fields for acceleration and formation of laser-generated ion stream enables to control the ion stream parameters in broad energy and current density ranges. It also permits to remove the useless laser-produced ions from the ion stream designed for implantation.For acceleration of ions produced with the use of a low fluence repetitive laser system (Nd:glass: 2 Hz, pulse duration: 3.5 ns, pulse energy:∼0.5 J, power density: 1010 W/cm2) in IPPLM the special electrostatic system has been prepared. The laser-produced ions passing through the diaphragm (a ring-shaped slit in the HV box) have been accelerated in the system of electrodes. The accelerating voltage up to 40 kV, the distance of the diaphragm from the target, the diaphragm diameter and the gap width were changed for choosing the desired parameters (namely the energy band of the implanted ions) of the ion stream. The characteristics of laser-produced Ge ion streams were determined with the use of precise ion diagnostic methods, namely: electrostatic ion energy analyser and various ion collectors. The laser-produced and post-accelerated Ge ions have been used for implantation into semiconductor materials for nanocrystal fabrication. The characteristics of implanted samples were measured using AES. 相似文献
3.
S. Bagchi P. Prem Kiran M.K. Bhuyan S. Bose P. Ayyub M. Krishnamurthy G.R. Kumar 《Applied physics. B, Lasers and optics》2007,88(2):167-173
We present results on hot electron and energetic ion (keV–MeV) generation from polished and nanostructured metallic surfaces
excited by p-polarized, femtosecond laser pulses in the intensity range of 1×1015–1.5×1017 W cm-2. A clear enhancement in the hard X-ray spectrum from nanoparticle-coated surfaces is observed, indicating ‘hotter’ electron
production in nanoparticle-produced plasma until the intensity of 2×1016 W cm-2 is reached. Contrary to the existing perception, we find that the hotter electrons do not lead to hotter ion emission. The
total ion flux and the ion energy integrated over the 4–1400 keV energy range are found to be enhanced by 50% and 16%, respectively,
for nanostructured targets in comparison to those from polished targets. 55% enhancement in yield is observed for ions at
the lower end of the energy range, while hotter ions are actually found to be suppressed by ∼40%. The surface modulations
present on the nanoparticle-coated targets are observed to reduce the maximum energy of the ions and showed an intensity-dependent
increase in the divergence of the ion beam.
PACS 79.20.Ds; 68.47.De; 61.80.Ba; 61.82.Bg; 42.65.Re 相似文献
4.
F. Belloni G. Caretto A. Lorusso V. Nassisi A. Perrone M. V. Siciliano 《辐射效应与固体损伤》2013,168(10-12):587-594
In this paper, we report investigations of the electron emission from pure Zn cathodes irradiated by UV laser pulses of 23 ns (full-width at half-maximum) at a wavelength of 248 nm (5 eV). The metal cathodes were tested in a vacuum photodiode chamber at 10?5 Pa. They were irradiated at normal incidence and the anode–cathode distance was set at 3 mm. The maximum applied accelerating voltage was 18 kV, limited by the electrical breakdown of the photodiode gap. Under the above experimental conditions, a maximum applied electric field of 6 MV/m resulted. In the saturation regime, the measured quantum efficiency value increased with the accelerating voltage due to the plasma formation. The highest output current was achieved with 14 mJ laser energy, 18 kV accelerating voltage and its value was 12 A, corresponding to a global quantum efficiency (GQE) approximately of 1×10?4. The temporal quantum efficiency was 1.0×10?4 at the laser pulse onset time and 1.4×10?4 at the pulse tail. We calculated the target temperature at the maximum laser energy. Its value allowed us to obtain output pulses of the same laser temporal profile. Tests performed with a lower laser photon energy (4.02 eV) demonstrated a GQE of two orders of magnitude lower. 相似文献
5.
E. Hantzsche 《等离子体物理论文集》1969,9(6):439-450
By integration of energy distribution functions for the cathode fall of H2 glow discharges we may show:
- 1) Space charge is almost constant within a large part of the dark space, therefore the field strength is a nearly linearly decreasing function of distance from cathode. Deviations from linearity are quantitatively discussed.
- 2) Composition of space charge: The contribution of atomic ions to the space charge may range from 5 to 10%. and the contribution of electrons from 0,1 to 10%, increasing with growing voltage.
- 3) Relative ion and neutral current densities at the cathode (ion current from the glow edge = 1) are decreasing with growing voltage. Molecular neutral current density equals 3 to 10 times molecular ion current density, in case of atomic particles the relation is from 1 to 5.
- 4) Total current density is increasing from 2.0 · 10?4 A/cm2 torr2 at the voltage U0 = 0,19 kV to 3,7 A/cm2 torr2 at U0 = 10 kV; cathode field strength is increasing from 0,53 kV/cm torr to 97 kV/cm torr.
- 5) The mean energy of neutrals is smaller than the mean ion energy by a factor of about 0.45…0.85, and the mean energy of molecules is smaller than the energy of atoms by a about 0.2…0.8. The dependence of the mean energies from voltage is discussed.
- 6) The energy gain of electrons is growing from 15% of total dark space energy at 0.19 kV to 70% at 10 kV; the energy gain of neutrals is decreasing at the same time.
6.
H. Daido S. Yamagami M. Suzuki H. Azuma I.W. Choi H. Fiedorowicz 《Applied physics. B, Lasers and optics》2001,72(3):385-387
We have measured low-energy ion emission from a gas-puff laser-plasma X-ray source. The ions may cause the degradation of
the condenser mirror of the extreme ultra-violet projection lithography system. A 0.7 J in 8 ns Nd:YAG laser at 1.06 μm was
focused onto the xenon gas-puff target with an intensity of ∼1012 W/cm2. The silicon (111) plates, placed at a distance of 32 mm from the laser-interaction region, were exposed with the xenon ions.
The average ion energy was measured to be less than 50 eV with a Faraday-cup detector placed close to the silicon plates.
The xenon deposition occurred in the silicon plates with a depth of less than 40 nm. The deposition density was measured with
a quadrupole secondary ion mass spectrometer to be 1021 /cm3 after 1500 laser shots. The energy-conversion efficiency from the laser energy into the ions is ∼0.1%/4 π sr/shot. For the
lithography system, if we can remove such ion bombardment completely using novel techniques such as electro-magnetic devices
or gas flow curtain techniques, the lifetime of the condenser mirror will be extended significantly.
Received: 20 November 2000 / Published online: 9 February 2001 相似文献
7.
A gold target has been irradiated with a Q-switched Nd:Yag laser having 1064?nm wavelength, 9?ns pulse width, 900?mJ maximum pulse energy and a maximum power density of the order of 1010?W/cm2. The laser–target interaction produces a strong gold etching with production of a plasma in front of the target. The plasma contains neutrals and ions having a high charge state. Time-of-flight (TOF) measurements are presented for the analysis of the ion production and ion velocity. A cylindrical electrostatic deflection ion analyzer permits measurement of the yield of the emitted ions, their charge state and their ion energy distribution. Measurements indicate that the ion charge state reaches 6+ and 10+ at a laser fluence of 100?J/cm2 and 160?J/cm2, respectively. The maximum ion energy reaches about 2?keV and 8?keV at these low and high laser fluences, respectively. Experimental ion energy distributions are given as a function of the ion charge state. Obtained results indicate that electrical fields, produced in the plume, along the normal to the plane of the target surface, exist in the unstable plasma. The electrical fields induce ion acceleration away from the target with a final velocity dependent on the ion charge state. The ion velocity distributions follow a “shifted Maxwellian distribution”, which the authors have corrected for the Coulomb interactions occurring inside the plasma. 相似文献
8.
Effect of plasticizers on electrical and photovoltaic properties of safranine-T-dye-based solid-state photo electrochemical
cell (PEC) is studied. Ethylene carbonate (EC) and propylene carbonate (PC) are used as plasticizers. Dark current–voltage
characteristic and different photovoltaic parameters such as open-circuit voltage, short-circuit current, and power conversion
efficiency are measured. To understand the effect of plasticizers on charge transport process, we analyze the dark current–voltage
characteristics to estimate the trap energy. From detail analysis of dark I–V, it has been observed that there is a crossover
voltage called transition voltage where the conduction mechanism changes. Above this voltage, the dark current is a space charge limited current (SCLC) in
the presence of exponentially distributed traps. Below transition voltage, current is ohmic for the cell without plasticizers
and dark current is an SCLC in presence of discrete traps for the cell with plasticizers. From our analysis, it is shown that
the transition voltage reduces due to the presence of plasticizers but the characteristic trap energy (ET) is not changed significantly. From photovoltaic measurements, it is observed that in presence of EC and PC power conversion
efficiency of the device increase from 7.319 × 10−4% to 14.64 × 10−4% under illumination with polychromatic light of 100 mW/cm2. It is expected that the power conversion efficiency depend on transition voltage. Due to the presence of plasticizers, the
barrier potentials of the devices reduce which results lowering of transition voltage. Lowering of it assists the migration
of charge carriers and as a result power conversion efficiency enhances. 相似文献
9.
Deok Kyu Kim Kyeong Min Kim Choon Bae Park 《Applied Physics A: Materials Science & Processing》2010,98(4):913-917
A p-type ZnO thin film was prepared using arsenic diffusion via the ampoule-tube method. This was followed by fabrication
of a ZnO p–n homojunction using n-type ZnO and characterization of the device properties. The ZnO thin film exhibited p-type
characteristics, with a resistivity of 2.19×10−3 Ω cm, a carrier concentration of 1.73×1020/cm3, and a mobility of 26.7 cm2/V s. Secondary ion mass spectrometer analysis confirmed that in- and out-diffusion occurred simultaneously from the external
As source and the GaAs substrate. The device exhibited the rectification characteristics of a typical p–n junction; the forward
voltage at 20 mA was approximately 5.5 V. The reverse-bias leakage current was very low—0.1 mA for −10 V; the breakdown voltage
was −11 V. The ampoule-tube method for fabricating p-type ZnO thin films may be useful in producing ultraviolet ZnO LEDs and
other ZnO-based devices. 相似文献
10.
2 and Si lattices at 380 °C, which was defined as zero-mismatch temperature. The implantation was conducted with a metal vapor
vacuum arc (MEVVA) ion implanter at an extraction voltage of 45 kV. Based on a thermal conduction estimation, a temperature
rise of 380 °C required the Ni-ion current density to be 35 μA/cm2. For the Si(111) wafers, the high conducting NiSi2 layers were indeed directly formed after Ni-ion implantation with this specific current density to a normal dose of 2×1017 ions/cm2 and the resistivity was as low as 9 μΩ cm. For the Si(111) wafers pre-covered with a 10-nm Ni overlayer, the resistivity
of the NiSi2 layers obtained under the same conditions decreased down to about 6 μΩ cm. The superior electrical property of the NiSi2 was thought to be related to its formation temperature, i.e. at a zero-mismatch temperature of 380 °C, which resulted in
minimizing the stress and stress-induced defects involved in its formation as well as cooling process.
Received: 27 April 1998 / Accepted: 26 October 1998 相似文献
11.
Enhanced field emission from pulsed laser deposited nanocrystalline ZnO thin films on Re and W 总被引:1,自引:0,他引:1
Dattatray J. Late Pankaj Misra B. N. Singh Lalit M. Kukreja Dilip S. Joag Mahendra A. More 《Applied Physics A: Materials Science & Processing》2009,95(2):613-620
Nanocrystalline ZnO thin films have been deposited on rhenium and tungsten pointed and flat substrates by pulsed laser deposition
method. An emission current of 1 nA with an onset voltage of 120 V was observed repeatedly and maximum current density ∼1.3 A/cm2 and 9.3 mA/cm2 has been drawn from ZnO/Re and ZnO/W pointed emitters at an applied voltage of 12.8 and 14 kV, respectively. In case of planar
emitters (ZnO deposited on flat substrates), the onset field required to draw 1 nA emission current is observed to be 0.87
and 1.2 V/μm for ZnO/Re and ZnO/W planar emitters, respectively. The Fowler–Nordheim plots of both the emitters show nonlinear
behaviour, typical for a semiconducting field emitter. The field enhancement factor β is estimated to be ∼2.15×105 cm−1 and 2.16×105 cm−1 for pointed and 3.2×104 and 1.74×104 for planar ZnO/Re and ZnO/W emitters, respectively. The high value of β factor suggests that the emission is from the nanometric features of the emitter surface. The emission current–time plots
exhibit good stability of emission current over a period of more than three hours. The post field emission surface morphology
studies show no significant deterioration of the emitter surface indicating that the ZnO thin film has a very strong adherence
to both the substrates and exhibits a remarkable structural stability against high-field-induced mechanical stresses and ion
bombardment. The results reveal that PLD offers unprecedented advantages in fabricating the ZnO field emitters for practical
applications in field-emission-based electron sources. 相似文献
12.
A Novel exploding wire type ion source device is proposed as a metallic ion source of intense pulsed heavy ion beam (PHIB) accelerator. In the device, multiple shot operations are realized without breaking the vacuum. The basic characteristics of the device are evaluated experimentally with an aluminum wire of diameter 0.2 mm and length 25 mm. A capacitor bank of capacitance 3 μF and a charging voltage of 30 kV was used, and the wire was successfully exploded by a discharge current of 15 kA with a rise time of 5.3 μs. Plasma flux of ion current density around 70 A/cm2 was obtained at 150 mm downstream from the device. The drift velocity of ions evaluated by a time-of-flight method was 2.7×104 m/ s, which corresponds to the kinetic energy of 100 eV for aluminum ions. From the measurement of the ion current density distribution, the ion flow is found to be concentrated toward the direction where the ion acceleration gap is placed. From the experiment, the device is found to be acceptable for applying the PHIB accelerator. 相似文献
13.
L. Torrisi A.M. Mezzasalma J. Badziak J. Wolowski G. Franco 《Applied Surface Science》2006,252(24):8533-8538
High energy laser plasma-produced Cu ions have been implanted in silicon substrates placed at different distances and angles with respect to the normal to the surface of the ablated target. The implanted samples have been produced using the iodine high power Prague Asterix Laser System (PALS) using 438 nm wavelength irradiating in vacuum a Cu target. The high laser pulse energy (up to 230 J) and the short pulse duration (400 ps) produced a non-equilibrium plasma expanding mainly along the normal to the Cu target surface. Time-of-flight (TOF) technique was employed, through an electrostatic ion energy analyzer (IEA) placed along the target normal, in order to measure the ion energy, the ion charge state, the energy distribution and the charge state distribution. Ions had a Boltzmann energy distributions with an energy increasing with the charge state. At a laser fluence of the order of 6 × 106 J/cm2, the maximum ion energy was about 600 keV and the maximum charge state was about 27+.In order to investigate the implantation processes, Cu depth profiles have been performed with Rutherford backscattering spectrometry (RBS) of 1.5 MeV helium ions, Auger electron spectroscopy (AES) with 3 keV electron beam and 1 keV Ar sputtering ions in combination with scanning electron microscopy (SEM). Surface analysis results indicate that Cu ions are implanted within the first surface layers and that the ion penetration ranges are in agreement with the ion energy measured with IEA analysis. 相似文献
14.
G. S. Sarkisov V. Yu. Bychenkov V. T. Tikhonchuk A. Maksimchuk S. Y. Chen R. Wagner G. Mourou D. Umstadter 《JETP Letters》1997,66(12):828-834
We report the first interferometric observations of the dynamics of electron-ion cavitation of relativistically self-focused
intense 4 TW, 400 fs laser pulse in a He gas jet. The electron density in a channel 1 mm long and 30 μm in diameter drops
by a factor of approximately 10 from the maximum value of ∼8×1019 cm−3. A high radial velocity of the plasma expansion, ∼3.8×108 cm/s, corresponding to an ion energy of about 300 keV, is observed. The total energy of fast ions is estimated to be 6% of
the laser pulse energy. The high-velocity radial plasma expulsion is explained by a charge separation due to the strong ponderomotive
force. This experiment demonstrates a new possibility for direct transmission of a significant portion of the energy of a
laser pulse to ions.
Pis’ma Zh. éksp. Teor. Fiz. 66, No. 12, 787–792 (25 December 1997)
Published in English in the original Russian journal. Edited by Steve Torstveit. 相似文献
15.
L. Torrisi 《辐射效应与固体损伤》2013,168(10):689-703
Energetic ions have been obtained irradiating a tungsten target with a Q-switched Nd:Yag laser, 1064?nm wavelength, 9?ns pulse width, 900?mJ maximum pulse energy and power density of the order of 1010?W/cm2. The laser-target interaction induces a strong metal etching with production of plasma in front of the target. The plasma contains neutrals and ions with high charge state. Time-of-flight measurements are presented for qualitative analysis of the ion production. A cylindrical electrostatic ion analyzer permits measuring of the yield of emitted ions, the charge state of detected ions and the ion energy distribution. Measurements indicate that, at a laser fluence of the order of 100?J/cm2, the charge state may reach 9+ and the ion energy reaches about 5?keV. The ion energy distribution is given as a function of the charge state. Experimental results indicate that an electrical field is developed along the normal to the plane of the target surface, which accelerates the ions up to high velocity. The ion velocity distributions follow a “shifted Maxwellian distribution”, which the author has corrected for the Coulomb interactions occurring inside the plasma. 相似文献
16.
A sequential three-dimensional (3D) particle-in-cell simulation code PICPSI-3D with a user friendly graphical user interface
(GUI) has been developed and used to study the interaction of plasma with ultrahigh intensity laser radiation. A case study
of laser–plasma-based electron acceleration has been carried out to assess the performance of this code. Simulations have
been performed for a Gaussian laser beam of peak intensity 5 × 1019 W/cm2 propagating through an underdense plasma of uniform density 1 × 1019 cm − 3, and for a Gaussian laser beam of peak intensity 1.5 × 1019 W/cm2 propagating through an underdense plasma of uniform density 3.5 × 1019 cm − 3. The electron energy spectrum has been evaluated at different time-steps during the propagation of the laser beam. When the
plasma density is 1 × 1019 cm − 3, simulations show that the electron energy spectrum forms a monoenergetic peak at ~14 MeV, with an energy spread of ±7 MeV.
On the other hand, when the plasma density is 3.5 × 1019 cm − 3, simulations show that the electron energy spectrum forms a monoenergetic peak at ~23 MeV, with an energy spread of ±7.5 MeV. 相似文献
17.
The generation of a 250-μs-wide electron beam in a plasma-emitter diode is studied experimentally. A plasma was produced by a pulsed arc discharge in hydrogen. The electron beam is extracted from a circular emission hole 3.8 mm in diameter under open plasma boundary conditions. The beam accelerated in the diode gap enters into a drift space in the absence of an external magnetic field through a hole 4.1 mm in diameter made in the anode. The influence of electron current deposition at the edge of the anode hole on the beam’s maximum attainable current, above which the diode gap breaks down, is studied for different accelerating voltages and diode gaps. The role of processes occurring on the surface of the electrodes is shown. For an accelerating voltage of 32 kV, a mean emission current density of 130 A/cm2 is achieved. The respective mean strength of the electric field in the acceleration gap is 140 kV/cm. Using the POISSON-2 software package, the numerical simulation of the diode performance is carried out and the shape of steady plasma emission boundaries in the cathode and anode holes is calculated. The influence of the density of the ion current from the anode plasma surface on the maximum attainable current of the electron beam is demonstrated. 相似文献
18.
M. F. Artamonov V. I. Krasov V. L. Paperny 《Journal of Experimental and Theoretical Physics》2001,93(6):1216-1221
The parameters of Cun+ and Tan+ ions from the plasma of a vacuum spark with a voltage up to 2.5 kV and a current rise rate up to 2 × 1010 A/s are studied using the time-of-flight method. At the initial stage of the discharge, bursts of beams of accelerated multiply charged ions from the cathode flame have been detected. It is established that the charge state distribution and energy of a beam are controlled by the initial voltage U 0 of the capacitor. Upon an increase in this voltage, the average charge of copper ions attains the value +9, and the average charge of tantalum ions can be as high as +20, while the energy attains values of 150 and 350 keV, respectively. It is found that the average energy of ions with charge Z increases in proportion to the charge and is close to the energy eZU 0 which would have been acquired by ions accelerated in the electric field of the discharge gap. 相似文献
19.
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
20.
Enrique Camps L. Escobar-Alarcón V. H. Castrejón-Sánchez P. Tolentino-Eslava 《Applied Physics A: Materials Science & Processing》2008,93(3):759-763
Amorphous carbon thin films were deposited by laser ablation of a graphite target, using the fundamental line of a 5 ns Nd:YAG
laser. Deposition was carried out as a function of the plasma parameters (mean kinetic ion energy and plasma density), determined
by means of a planar probe. In the selected working regimes the optical emission from the plasma is mainly due to atomic species,
namely C+ (426.5 nm); however, there is also emission from other atomic species and molecular carbon. The hardness and resistivity
could be varied in the range between 10 and 25 GPa, and 108 and 1011 Ω cm, respectively. The maximum values were obtained at a 200 eV ion energy and 6×1013 cm−3 plasma density, where the maximum quantity of C–C sp3 bonds was formed, as confirmed by Raman spectroscopy. 相似文献