共查询到20条相似文献,搜索用时 15 毫秒
1.
C.E. Gonzalez S.C. Sharma N. Hozhabri D.Z. Chi S. Ashok 《Applied Physics A: Materials Science & Processing》1999,68(6):643-645
Near-surface vacancy-type defects have been studied by positron beam spectroscopy in three boron-doped Si wafers; a control
sample, second sample exposed to atomic hydrogen in electron cyclotron resonance (ECR) plasma, and a third sample annealed
at 500 °C following plasma treatment. From the analysis of the Doppler broadening spectra, measured as a function of positron
implantation depth, we obtain positron diffusion lengths of about 100 and 250 nm for the damaged layer and bulk of the wafer,
respectively. For the plasma-treated wafer, our measurements provide a defect density of about 5×1017 cm-3.
Received: 4 September 1998 / Accepted: 5 January 1999 / Published online: 28 April 1999 相似文献
2.
It is shown that dipole structures placed in a thin (less than 1 nm) near-surface layer of a high-resistivity field emitter
produce small domains on the emitting surface in which the electric field may exceed 108 V/cm. In these domains, the emitter surface potential is positive, providing effective electron transport from inside the
emitter to the emission boundary. Optimal dipole orientations ensuring maximal electric fields at the surface are found. When
the surface density of dipoles localized in the near-surface layer is on the order of 106 cm−2, one can expect an emitter-averaged emission current density of higher than 1 A/cm2. The dipole structures in the near-surface layer may persist owing to incorporated impurity molecules having a dipole moment
or result from a random combination of positively charged ionized impurities and electrons captured by deep traps. Trap charging/discharging
asymmetry accounts for the hysteresis of the emission I–V characteristics. 相似文献
3.
The results of the investigation of the surface of strontium titanate single crystals after treatment with high-energy plasma
are presented. The surface morphology of the strontium titanate single crystals and the change in its characteristics after
plasma treatment have been studied using electron scanning and atomicforce microscopy. A change in the electronic state of
a part of the titanium ions and a change in the stoichiometry in the modified near-surface layer have been found by the method
of valence shift of X-ray lines. A preliminary analysis has been made of the conditions providing the formation of single-
and two-level systems of ordered crystallites with sizes of 10−7–10−10 m on the surface of single-crystal strontium titanate with impurities of ions of the iron and lanthanum groups. 相似文献
4.
Experimental results on interaction of a rotating relativistic electron beam with plasma and neutral gas are presented. The
rotating relativistic electron beam has been propagated up to a distance of 150 cm in a plasma. The response of the plasma
to the rotating electron beam is found to be of magnetic diffusion type over a plasma density range 1011–1013 cm−3. Excitation of the axial and azimuthal return currents by the rotating beam and subsequent trapping of the azimuthal return
current layer by the magnetic mirror field are observed. A field-reversed configuration has been formed by the rotating relativistic
electron beam when injected into neutral hydrogen gas. We have observed field reversal up to three times the initial field
in an axial length of 100 cm. 相似文献
5.
A. V. Voitsekhovskii V. S. Volkov D. V. Grigor’ev I. I. Izhnin A. G. Korotaev A. P. Kokhanenko M. Posyatsk V. G. Sredin N. Kh. Talipov 《Russian Physics Journal》2008,51(9):936-942
The results of investigations into spatial distribution of donors in p-HgCdTe graded band-gap layers with various composition profiles in the near-surface layer upon ion-beam etching are reported. It
is found that the depth of the resulting n+-layer is weakly dependent on the conditions of ion-beam etching and composition of material of the surface and is about 0.5–1
μm. The electron density in the n+-layer on the surface is observed to increase with time of beam etching. It is shown that the conditions of ion-beam etching
and the composition of the near-surface region significantly affect only the depth of the foregoing layer with low electron
density. Analysis of experimental data shows that the process of ion-bean etching in p-HgCdTe heteroepitaxial structures with a composition gradient in the near-surface region is different from etching in HgCdTe homogeneous epitaxial structures and crystals.
Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 9, pp. 51–56, September, 2008. 相似文献
6.
The results of a study of degradation of the surface of gallium arsenide resulting from irradiation with a power excimer laser at power densities ranging from the threshold power to the power level causing local melting of the surface are presented. Two degradation mechanisms have been identified, one of which causes the formation of a thin near-surface layer of modified nonstoichimetric gallium arsenide at a power level higher than 1×107 W/cm2 and the other of which causes the formation of a separate gallium phase. The formation of the separate gallium phase can be produced either by a single pulse of laser radiation with a power density exceeding 2.7×1011 W/cm2 or by a few less powerful pulses. An empirical relationship has been established between the power density and the number of pulses causing the formation of the separate gallium phase. It has also been established that as a result of laser irradiation at the boundary of “cold” and “hot” gallium arsenide, periodically ordered defects in the form of blocks aligned along the [100] directions emerge. 相似文献
7.
An intense slow positron beam using a 15 MeV LINAC (average current 1.25 × 1015 e−/s) at the Radiation and Photochemistry Group, Chemistry Division of Argonne National Laboratory (ANL) has been proposed and studied. Computer simulated results optimizing the positron yield and distribution of energy and angle show that a slow positron production at 1010 e+/s is possible. A proposed design of an intense slow positron beam with optimal conditions of incident electron, converter/moderator configurations, and extraction/transportation is presented. 相似文献
8.
D. I. Vaisburd S. I. Tverdokhlebov T. A. Tukhfatullin 《Russian Physics Journal》1997,40(11):1064-1082
A dense pulsed electron beam and nanosecond pulse length has been used to inject negative electric charge into various dielectric
materials (single crystals, glasses, composites, plastics) for initiation of electron field emission from the dielectric into
a vacuum. It has been shown that upon reaching a critical electric field in the bulk and at the dielectric surface there is
intense critical electron emission. The local current density from the emission centers reaches a record value (for dielectrics)
of the order of 106 A/cm2. The emission occurs in the form of a single gigantic pulse. The measured amplitude of the emission current averaged over
the emitting surface is the same order of magnitude as the injected electron current: 10–1000 A. the emission current pulse
lages behind the current pulse of the primary electron beam injected into the sample. The delay time is in the range 1–20
nsec and decreases with increasing current density of the injected beam. Direct experimental evidence is found for intense
generation of carriers (band or quasifree electrons) in the near-surface layer of the dielectric in a strong electric field
due to the Frenkel-Poole effect and collisional ionization of traps, usually various donor levels. This process greatly strengthens
the field emission from the dielectric. It has been shown experimentally that the emission is nonuniform and is accompanied
by “point bursts” at the surface of the dielectric and ionized plasma spikes in the vacuum interval. These spikes are the
main reason that the transition of the field emission into “bursts” is critical, similar to the current which has been previously
observed in metals and semiconductors. However there are a number of substantial differences. For example the critical field
emission current density needed for the transition into “bursts” is three orders of magnitude less than for metals. If we
provide sufficient electron current at the surface or from the bulk of the dielectric to the emission centers, then the critical
emission is always accompanied by a vacuum discharge between the surface of the dielectric and a metallic collector. A detailed
computer model of the processes in the dielectric during injection of a high-density electron beam has been developed which
allows one to understand the complex physical pattern of the phenomenon.
Tomsk Polytechnic University. Institute of High-Current Electronics, Siberian Section, Russian Academy of Sciences. Translated
from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 11, pp. 45–67, November, 1997. 相似文献
9.
A. D. Pogrebnjak A. A. Dem’yanenko V. M. Beresnev O. V. Sobol’ O. M. Ivasishin K. Oyoshi Y. Takeda H. Amekura A. I. Kupchishin 《Physics of the Solid State》2016,58(7):1453-1457
The recrystallization of the structure of an X-ray amorphous AlN–TiB2–TiSi2 coating containing short-range order regions with characteristic sizes of 0.8–1.0 nm has been performed using a negative gold ion (Au–) beam and high-temperature annealing. Direct measurements using methods of high-resolution transmission electron microscopy (HRTEM) and energy-dispersive X-ray spectral (EDXS) microanalysis have demonstrated that thermal annealing at a temperature of 1300°C in air results in the formation of nanoscale (10–15 nm) phases AlN, AlB2, Al3O3, and TiO2, whereas the ion implantation of negative ions Au– leads to a fragmentation (decrease in the size) of nanograins to 2–5 nm with the formation of spheroidal gold nanocrystallites a few nanometers in size, as well as to the formation of an amorphous oxide film in the depth (near-surface layer) of the coating due to ballistic ion mixing and collision cascades. 相似文献
10.
The results of studies of the physical nature of emissions produced in polymethyl methacrylate excited by electron beams of a subnanosecond or a nanosecond duration are presented. The spatial, amplitude, and spectral-kinetic properties of emissions have been examined under an electron beam energy density varying from 10–4 to 4 × 10–1 J/cm2. It has been found that cathodoluminescence is the primary type of emission under low energy densities of the electron beam. When the energy density of a nanosecond electron beam and/or the number of pulses of excitation by a subnanosecond electron beam were increased, an electrical breakdown of polymethyl methacrylate occurred in the irradiated region. This process was accompanied by a burst of emission of dense, low-temperature plasma. 相似文献
11.
T. Redel J. Eberlein R. Tkotz W. Hartmann M. Stetter R. Stark K. Frank J. Christiansen 《Applied Physics A: Materials Science & Processing》1992,54(6):520-522
The investigation of the interaction of pulsed electron beams with PMMA (polymethylmethacrylate) targets is reported. The electron beam of some 10–8 s in duration is produced in a pulsed low-pressure gas discharge. The beam power density of up to 108 W/cm2 leads to a surface plasma formation similar to that of the pulsed laser ablation process. The propagation of the ablated material and the shock wave inside the PMMA target are observed by means of Schlieren diagnostics. An electron density gradient of over 3×1019 cm–4 has been observed in the expanding plasma up to 1.5 s after the plasma formation. During the early stage of expansion, the expansion velocity of the plasma plume as determined by the steep electron density gradient is around 105 cm/s. The pressure behind the shock front inside the PMMA target as determined from the shock velocity exceeds 0.3 Gpa. 相似文献
12.
Research has been done on major physical processes governing the scope for generating magnetized low-energy high-current electron beams in a plasma-filled system. Conditions are considered for efficient excitation of the explosive electron emission at a large-area cathode at low accelerating voltages, together with the trends in beam formation in the nonstationary double layer formed between the cathode and anode plasmas, as well as the beam transport to the collector in the inhomogeneous guiding plasma. It is found that a gun having a plasma anode enables one to generate wide-aperture electron beams of microsecond duration having a mean electron energy of 10–20 keV and an energy density of up to 20 J/cm2 or more, which goes with homogeneity sufficient for technological purposes.High-Current Electronics Institute, Siberian Branch, Russian Academy of Sciences. Translated from Izvestiya Vysshikh, Fizika, No. 3, pp. 100–114, March, 1994. 相似文献
13.
A. M. Zhukeshov A. T. Gabdullina A. U. Amrenova G. A. Abdraimova M. Mukhamedryskyzy 《Technical Physics》2017,62(12):1817-1821
The temperature gradient and melting depth of the surface of iron-based alloys under the action of high-temperature pulsed plasma beams have been estimated and compared with the experimental data. It has been shown that the steel surface melts under the action of a pulsed plasma flow at an energy density of 15–20 J/cm2; the heat front propagates to a depth of up to 20 μm, the thickness of the molten layer being less than 10 μm. The characteristic size of the microstructure formed as a result of thermal perturbation is estimated at 17 nm. The formation of new phases with crystallite sizes that vary in the range of 16–270 nm is demonstrated experimentally. It has been shown that the formation of nanosize crystalline structure and modified near-surface region are the main factors responsible for strengthening steels. 相似文献
14.
Yu. B. Bolkhovityanov A. P. Vasilenko A. K. Gutakovskii A. S. Deryabin M. A. Putyato L. V. Sokolov 《Physics of the Solid State》2011,53(10):2005-2011
Heterostructures of the “strained Ge film/artificial InGaAs layer/GaAs substrate” type have been grown by molecular beam epitaxy.
A specific feature of these structures is that the plastically relaxed (buffer) InGaAs layer has the density of threading
dislocations on a level of 105–106 cm−2. These dislocations penetrate into the strained Ge layer to become sources of both 60° and 90° (edge) misfit dislocations
(MDs). Using the transmission electron microscopy, both MD types have been found at the Ge/InGaAs interface. It has been shown
that the presence of threading dislocations inherited from the buffer layer in a tensile-strained Ge film favors the formation
of edge dislocations at the Ge/InGaAs interface even in the case of small elastic deformations in the strained film. Possible
mechanisms of the formation of edge MDs have been considered, including (i) accidental collision of complementary parallel
60° MDs propagating in the mirror-tilted {111} planes, (ii) induced nucleation of a second 60° MD and its interaction with
the primary 60° MD, and (iii) interaction of two complementary MDs after a cross-slip of one of them. Calculations have demonstrated
that a critical layer thickness (h
c
) for the appearance of edge MDs is considerably smaller than h
c
for 60° MDs. 相似文献
15.
C. Hugenschmidt K. Schreckenbach D. Habs P. G. Thirolf 《Applied physics. B, Lasers and optics》2012,106(1):241-249
Presently, large efforts are conducted toward the development of highly brilliant γ beams via Compton back scattering of photons from a high-brilliance electron beam, either on the basis of a normal-conducting
electron linac or a (super-conducting) Energy Recovery Linac (ERL). Particularly, ERLs provide an extremely brilliant electron
beam, thus enabling the generation of highest-quality γ beams. A 2.5 MeV γ beam with an envisaged intensity of 1015 photons s−1, as ultimately envisaged for an ERL-based γ-beam facility, narrow band width (10−3), and extremely low emittance (10−4 mm2 mrad2) offers the possibility to produce a high-intensity bright polarized positron beam. Pair production in a face-on irradiated
W converter foil (200 μm thick, 10 mm long) would lead to the emission of 2×1013 (fast) positrons per second, which is four orders of magnitude higher compared to strong radioactive 22Na sources conventionally used in the laboratory. Using a stack of converter foils and subsequent positron moderation, a high-intensity
low-energy beam of moderated positrons can be produced. Two different source setups are presented: a high-brightness positron
beam with a diameter as low as 0.2 mm, and a high-intensity beam of 3×1011 moderated positrons per second. Hence, profiting from an improved moderation efficiency, the envisaged positron intensity
would exceed that of present high-intensity positron sources by a factor of 100. 相似文献
16.
V. I. Bachurin S. A. Krivelevich 《Journal of Surface Investigation: X-ray, Synchrotron and Neutron Techniques》2009,3(2):313-316
The formation of Ni x Al y intermetallic compounds in two-layer (Ni/Al) structures (nickel films deposited on aluminum substrates in vacuum) under bombardment by Ar+ ions has been studied experimentally. The method based on Rutherford backscattering of He+ ions is used to demonstrate that argon ion bombardment causes the formation of intermetallic compounds in the near-surface layer. The thickness of the intermetallic layer formed in the near-surface region substantially exceeds the projective ion path. The composition and thickness of the intermetallic layer depend mainly on the implantation dose and the substrate temperature, rather than on the ion current density. In the intermetallic layer, the content of nickel increases with increasing temperature. It has been established that, in the absence of bombardment, intermetallic phases are not observed at temperatures lower than T = 400°C and that, in the presence of bombardment, the Ni3Al intermetallic layer arises at a temperature of 320°C. 相似文献
17.
H. Gao S. Asp C. Biedermann D. R. DeWitt R. Schuch W. Zong H. Danared 《Hyperfine Interactions》1996,99(1):301-308
The electron-ion recombination rates of Ne10+ and D+ have been measured as a function of relative energy and electron density. We found a strong enhancement of e-Ne10+ recombination over expected radiative recombination rates below 1 meV relative energies, reaching a factor of 4 close to zero relative energy. Remarkably, the measured rate coefficients decrease as a function of electron density for both systems. Studies of recombination of D+ indicate that this density dependence may be due to temperature variations of the electron beam with the electron density. 相似文献
18.
T. Akahane T. Chiba N. Shiotani S. Tanigawa T. Mikado R. Suzuki M. Chiwaki T. Yamazaki T. Tomimasu 《Applied Physics A: Materials Science & Processing》1990,51(2):146-150
A facility for generating a high intensity slow positron beam using an electron linear accelerator has been constructed. A conversion efficiency of 6×10–7 slow positrons per incident electron has been obtained for 75 MeV electrons. Storage and stretching of pulsed slow positrons have been successfully carried out with a Penning trap. 相似文献
19.
V. V. Privezentsev N. Yu. Tabachkova K. B. Eidelman S. V. Ksenich 《Bulletin of the Russian Academy of Sciences: Physics》2016,80(12):1421-1426
The formation of nanoparticles in СZn-Si(100) implanted with 64Zn+ ions using a dose of 5 × 1016 cm–2 and an energy of 50 keV at room temperature with subsequent thermal processing in oxygen at temperatures ranging from 400 to 900°C is studied. The surface topology is investigated with scanning electron (in the secondary emission mode) and atomic force microscopes. The structure and composition of the near-surface silicon layer are examined using a high-resolution transmission electronic microscope fitted with a device for energy dispersive microanalysis. An amorphized near-surface Si layer up to 130 nm thick forms when zinc is implanted. Amorphous zinc nanoparticles with an average size of 4 nm are observed in this layer. A damaged silicon layer 50 nm thick also forms due to radiation defects. The metallic zinc phase is found in the sample after low-temperature annealing in the range of 400–600°C. When the annealing temperature is raised to 700°C, zinc oxide ZnO phase can form in the near-surface layer. The complex ZnO · Zn2SiO4 phase presumably emerges at temperatures of 800°C or higher, and zinc-containing nanoparticles with lateral sizes of 20–50 nm form on the sample’s surface. 相似文献
20.
The effect of low energy noble gas ion bombardment on the electrical and optical properties of Si(211) surfaces has been investigated by surface conductivity and field effect measurements, ellipsometry and AES. With this combination of techniques, information is obtained concerning the electrical properties, the chemical composition and the damage of the surface layer. Upon ion bombardment in the energy range of 500–2000 eV, ellipsometry shows the formation of a damaged surface layer with optical properties close to those of an evaporated amorphous silicon film. In order to measure the conductivity changes as sensitive as possible, nearly intrinsic silicon crystals were used. For the clean, 5200 Ω cm Si(211) surface, bombarded only with a mass-analyzed argon ion beam, a small increase in conductivity is found to occur after a small ion dose (saturation after 5 × 1014 ions cm?2 while after 5 × 1013 ions cm?2 already half of the increase has occurred). The effect was found to be independent of ion energy between 500 and 2000 eV. As the field effect signal did not change after this treatment, it is concluded that the surface state density in the neighbourhood of the Fermi level shows a slight decrease. 相似文献