Showing papers on "Fluence published in 1982"
TL;DR: In this paper, the authors studied the long-range mixing by 500-keV xenon ions in targets consisting of 2000-A films of aluminium on polycrystalline aluminium substrate, onto which has been evaporated a 500-A overlayer of copper.
Abstract: Ion-beam mixing by 500-keV xenon ions has been studied in targets consisting of 2000-A films of aluminium on a polycrystalline aluminium substrate, onto which has been evaporated a 500-A overlayer of copper. Both long- and short-range-mixing processes have been identified, by RBS analysis of the irradiated targets, as a deep copper tail in the aluminium and interfacial broadening, respectively. The long-range component varies linearly with xenon fluence, is temperature-independent in the interval 40–500 K, and is not influenced by the presence of an interfacial oxide layer between the copper and aluminium layers. The number of long-range-mixed atoms is in agreement with theoretical estimates of the recoil mixing. The short-range mixing, which is the dominating process, has a squareroot dependence on xenon fluence and is independent of temperature between 40 and 300 K, increasing rapidly at higher temperatures. The broadening attributed to the short-range mixing is explained by interstitial diffusion within the cascade. For small xenon fluences, interfacial oxide layers inhibited both short-range mixing and thermal diffusion. Higher xenon fiuences subdued the inhibition.
75 citations
TL;DR: In this article, the changes in reflectivity of a silicon surface, irradiated by a green picosecond pulse, are probed during and following that pulse with a spatial resolution of 10 μm.
Abstract: The changes in reflectivity of a silicon surface, irradiated by a green picosecond pulse, are probed during and following that pulse with a spatial resolution of 10 μm. The data indicate the development of a liquid phase, and a resolidification either into a single crystal or an amorphous phase. The latter has a characteristic ring-type pattern, and occurs only at locations where the incident picosecond laser fluence lies between 0.2 and 0.26 J/cm2. The reflectivity data appear to be in good quantitative agreement with a “simple heating” model, in which the electrons and phonons maintain a local thermodynamic equilibrium on a picosecond time scale.
56 citations
TL;DR: In this article, the effect of buffer gas pressure on specific dissociation rates and the isotopic selectivity was investigated and the intrinsic relation between the fractional conversion per pulse and the fluence by means of deconvolution technique.
Abstract: Multiphoton dissociation of ppm level CTF3 in CHF3 is reported. The effect of buffer gas pressure on the specific dissociation rates and the isotopic selectivity is investigated. Pulse energy dependence of the dissociation rates is converted to the intrinsic relation between the fractional conversion per pulse and the fluence by means of the new deconvolution technique. By addition of 100 Torr argon, the critical fluence of CTF3 was decreased from 136 to 34 J/cm2, while the intrinsic selectivity was increased from 34 to 580. In the absence of buffer gas argon, the fractional conversion per pulse exhibits two different pressure dependences. Unlike in the case below 15 Torr, the system shows strong pressure dependence and loss of the isotopic selectivity above 15 Torr. Possible application to the tritium removal process is also discussed.
53 citations
TL;DR: In this article, the first investigation of laser-processed (100)InP surfaces is reported, under irradiation by a pulsed (3 ns) green laser, above a threshold fluence of 0.2 J/cm2, both stoichiometry and structure of the surface are altered: Matter departure from the surface takes place, together with a transition towards a (1×1) LEED pattern which is attributed to a surface formed by terraces and a random array of steps.
Abstract: The first investigation of laser‐processed (100)InP surfaces is reported. Under irradiation by a pulsed (3 ns) green laser, above a threshold fluence of 0.2 J/cm2, both stoichiometry and structure of the surface are altered: Matter departure from the surface takes place, together with a transition towards a (1×1) LEED pattern which is attributed to a surface formed by (1×1) terraces and a random array of steps. At higher fluences, desorption increases and a fully disordered surface is obtained. A comparison with the results obtained on other semiconductors and implications for future studies are outlined.
51 citations
TL;DR: In this article, measurements have been made of the amount of deuterium gas re-emitted from Papyex carbon during deuteron bombardment with an energy range of 100 eV to 1000 eV.
37 citations
TL;DR: In this article, the saturation of gain at 1053 nm was studied in seven Nd:doped phosphate glasses and the product of saturation fluence and gain cross section was constant to within ±6 percent.
Abstract: Saturation of gain at 1053 nm was studied in seven Nd:doped phosphate glasses. Values of saturation fluence measured with 1.4-ns pulses were slightly less than those measured with 20-ns pulses. At both pulse lengths, saturation fluence increased with output fluence. For the seven glasses, the product of saturation fluence and gain cross section was constant to within ±6 percent.
32 citations
TL;DR: The theorem establishes a one-to-one correspondence between points in the two scattering media where the spectra of primary and scattered photons have the same distribution in energy and angle, and where the fluence ratio equals the square of the electron density ratio.
Abstract: This paper concerns a method of scaling photon fluence from one scattering material to another when the photon energies are such that the dominant mode of interaction is Compton scattering The theorem establishes a one-to-one correspondence between points in the two scattering media where the spectra of primary and scattered photons have the same distribution in energy and angle, and where the fluence ratio equals the square of the electron density ratio Experimental tests were made with cobalt-60 gamma radiation using ionization-chamber measurements in graphite, acrylic plastic, polystyrene, and water phantoms The experimental results are consistent with the equality of photon spectral shapes and angular distributions at corresponding points The fluence ratios may differ by a few percent from the predicted values, depending on distance from the source
27 citations
TL;DR: In this article, the fluence dependence of the sputtering yield has been studied on amorphous silicon under normal conditions with 0.5 to 5keV Ar+ using the KARMA technique (Kombinierte Auger/Rontgen Mikro-Analyse).
Abstract: The fluence dependence of the sputtering yield has been studied on amorphous silicon under uhv conditions with 0.5 to 5keV Ar+ using the KARMA technique (Kombinierte Auger/Rontgen Mikro-Analyse). It allows to measure simultaneously the surface composition, the differential sputtering yield, and the total amount of implanted gas. For all energies, the yield increases initially and reaches saturation after the removal of a layer the thickness of which is closely correlated to the ion range. Gas implantation as a cause for these fluence effects can be ruled out by quantitative analysis. The relative yield increase is found to be larger for low energies than for higher ones. Both these findings can be qualitatively explained by a simple damage collection model.
18 citations
TL;DR: In this paper, the authors used CO2 laser pulses for which the intensity vs time profile is rectangular (10 or 50 ns duration) in the multiphoton excitation of CF2HCl and CF2CFCl dilute in high pressure (400 Torr) argon.
Abstract: CO2 laser pulses for which the intensity vs time profile is rectangular (10 or 50 ns duration) were used in the multiphoton excitation of CF2HCl and CF2CFCl dilute in high pressure (400 Torr) argon. Energy deposition was measured by optoacoustic detection and CF2 product yield by laser‐excited fluorescence. Even at low yield (e.g., 10−3) more than 100 photons were absorbed per CF2CFCl molecule, while for an identical yield, CF2HCl absorbed 200 times less energy. For the same laser fluence, the higher intensity 10 ns pulses gave more yield from CF2CFCl (factors up to 500 were observed) than the less intense 50 ns pulses; for CF2HCl, the two intensities give the same yield. For both molecules, the two intensities gave the same optoacoustic signal for a given fluence. These results are related to the dependence on reactant energy of the competing ratio of collisional deactivation to laser excitation.
18 citations
TL;DR: In this paper, the thermal conductivity of vitreous silica has been measured after exposure to various neutron fluences and it has been observed that the increase in Λ(T) saturates for approximately the same fluence for which the change in mass density ϱ saturates.
12 citations
TL;DR: In this paper, high resolution Rutherford backscattering in combination with channeling and transmission electron microscopy were used to study the fluence dependence of initial damage and residual defects of high-temperature (900 °C) Se+•implanted GaAs.
Abstract: High resolution Rutherford Backscattering in combination with channeling and Transmission Electron Microscopy were used to study the fluence dependence of initial damage and residual defects of high‐temperature (900 °C) Se+‐implanted GaAs It is found that the number of displaced atoms increases linearly as a function of dose, until the layer becomes amorphous The damage profile extracted by using a single scattering theory is in good agreement with a Monte Carlo computer simulation when the ion dose is below that required to amorphize the layer After annealing at 900 °C for 15 min, complete recovery of the damage has been observed for samples with 5×1012 cm−2 and 1×1013 cm−2 The samples with higher doses show some residual disorder which has been identified as dislocation loops and small precipitates Electrical measurements reveal that highest activation efficiency is obtained for 1×1013 cm−2, which reduces drastically at higher doses However, the activation efficiency for all doses increases with a
TL;DR: In this paper, the rotational and vibrational state distributions of the nascent CN(X 2 Σ+) rovibronic state distributions following the unimolecular reaction CF3CN→CF3+CN are measured using IR multiple photon excitation using the focused output from a CO2 TEA laser at fluences 3-150 J cm−2.
Abstract: Measurements of nascent CN(X 2Σ+) rovibronic state distributions following the unimolecular reaction CF3CN‡→CF3+CN are reported. Excitation under collision free conditions is provided by IR multiple photon excitation using the focused output from a CO2 TEA laser at fluences 3–150 J cm−2. At fluences 3–20 J cm−2, the CN(X 2Σ+,v′′ = 0) rotational temperature increases monotonically from 500 to 1200 K with increasing fluence, while at fluences 30–150 J cm−2, the rotational and vibrational temperatures do not change and are TR = 1200±100 K and TV = 2400±150 K. At low fluences, the increase in V, R, T excitations with increasing fluence reflects an increase in the vibrational excitation of the dissociating parent molecules. The ultimate level of excitation that the parent molecules attain depends both on the fluence and the intensity of the laser, and the appearance time of the CN fragments decreases with increasing fluence, since molecules excited significantly above dissociation threshold decompose more rapi...
TL;DR: In this paper, the fluence dependence of development of microscopic surface features, particularly etch pits, during 9 keV Ar + ion bombardment of (11, 3, 1) oriented Cu single crystals has been studied employing quasi-dynamic irradiation and observation techniques in a scanning electron microscope-accelerator system.
TL;DR: In this article, the authors investigated the multiple infrared photon decomposition of chloroethane with radiation of wavelength ∼ 10 μm, which is absorbed by the C-C stretching mode of the molecule.
Abstract: The results are presented of an investigation of the multiple infrared photon decomposition of chloroethane with radiation of wavelength ∼ 10 μm, which is absorbed by the C-C stretching mode of the molecule. The study employed a focussed beam of maximum fluence 190 J/cm 2. The fluence dependence of the fractional decomposition with ṽ = 966 cm -1 radiation under nearly collision-free conditions (0.035 torr) was quantitatively interpreted by solution of the appropriate master equation (taking postpulse collisions into account) to obtain the energy-dependent absorption cross section, σ(E). It was found that decomposition at high fluence (arising from energies in the range 19000-28000 cm -1) and energy absorption at low fluence (mean absorbed energy ∼ 150-1000 cm -1) could be simultaneously fitted with σ(E)/cm 2 = 2.5 × 10 -19 exp[-3.45(E/hv) 0.14]. Comparison of this dependence with that found from data obtained with ṽ ∼ 2700 cm -1 suggests that the oscillator strength is strongly dependent on the mode being excited, even when the energy is thoroughly randomized within the molecule.
TL;DR: In this article, a re-examination of the decomposition of cyclobutanone vapor by a pulsed CO2 laser over a range of pressure and fluence has shown that the apparent disagreement in previous measurements of the pressure dependence of the C3H6/C2H4 product ratio can be explained by differences in absorbed energy density.
Abstract: A re-examination of the decomposition of cyclobutanone vapor by a pulsed CO2 laser over a range of pressure and fluence has shown that the apparent disagreement in previous measurements of the pressure dependence of the C3H6/C2H4 product ratio can be explained by differences in absorbed energy density. At low pressures of cyclobutanone, the energy of the decomposing molecules is apparently higher at low fluence than at high fluence, and an explanation is suggested in terms of a variation in the relative proportions of "collision-modified" and "collision-free" reactions with changing pressure and absorbed energy density.
TL;DR: In this article, the electron and positive ion emissions observed in the work cited are noted to be inconsistent with the Saha-Langmuir equation and the observed exponential dependence of ion yield on incident laser energy is shown to be consistent with thermal evaporation in either the low or the high fluence regime.
Abstract: The electron and positive ion emissions observed in the work cited are noted to be inconsistent with the Saha‐Langmuir equation. Moreover, the observed exponential dependence of ion yield on incident laser energy is shown to be inconsistent with thermal evaporation in either the low or the high fluence regime. It is suggested that the most likely cause of this ion emission is multiple‐photo‐ion emission.
TL;DR: In this article, the authors show how channeling profiles in the direction of GaAs vary with energy and fluence for room temperature channeling, and what maximum density can be achieved at depths of about 1 to 3 µm for energies from 75 to 300 keV.
Abstract: Be and Si are commonly employed p- and n-type respectively dopants, implanted in GaAs. Channeled implantation produces deeper and sharper profiles than standard random implants. To employ channeling, we need to know how the profile shape, depth, and doping density vary with implantation energy and fluence, and what maximum density can be achieved. This work shows how channeling profiles in the direction of GaAs vary with energy and fluence for room temperature channeling. Data are shown for fluences of 3 × 1012, 3 × 1013, and 3 × 1014cm-2and energies of 40, 75, 150, and 300 keV. The deep channeling profile saturates for 150 keV Be just below a fluence of 3 × 1014cm-2and a density of about 4 × 1017cm-3can be achieved at depths of about 1 to 3 µm for energies from 75 to 300 keV. The maximum density for 150 keV Si for room temperature channeling is about 4 × 1016cm-3and occurs at depths from 1 to 4 µm in the energy range from 40 to 300 keV.
TL;DR: In this article, annealing time in the 50 microsecond to 100 millisecond range can be used by supplying the necessary energy by a series of multiple scans of an electron beam or incoherent light flash.
Abstract: High fluence energy pulses in the nanosecond-microsecond time range involving the melting of a surface layer have been demonstrated as a very successful tool in annealing ion-implanted semiconductors. As an alternative method, longer annealing time in the 50 microsecond to 100 millisecond range can be used by supplying the necessary energy by a series of multiple scans of an electron beam or incoherent light flash. In, this case the annealing can take place via solid phase epitaxial regrowth of the damaged layer. Apparatus description, surface temperature measurements and experimental results obtained with such annealing methods are presented on ion-implanted silicon samples, showing the possibility of regrowing high quality implanted layers over large area specimens, without affecting carrier mobility, diffusion length and transport parameters and giving rise to good efficiency solar cells.
TL;DR: Ion implanted profiles of 40 keV Ge + into Si at fluences ranging from ∼10 15 ions/cm 2 up to saturation have been measured using the RBS technique as mentioned in this paper.
TL;DR: In this article, an analytical formulation is given which allows related coefficients to be extracted from the experimental data, among the most predominant parameters are the vacuum quality (partial pressure of hydrogenated species), the chemical state of the pre-adsorbed species and the ion beam characteristics: electronic stopping and fluence.
Abstract: When resonant nuclear reactions are used for hydrogen analysis of solid materials, under beam impact a systematic variation of surface hydrogen content is observed as a function of the ion fluence, leading to a dynamic equilibrium value. This phenomenon has been investigated with 15N ions of energy close to 6.4 MeV and interpreted in the framework of chemical effects like adsorption, radiolysis and desorption. An analytical formulation is given which allows related coefficients to be extracted from the experimental data. Among the most predominant parameters are the vacuum quality (partial pressure of hydrogenated species), the chemical state of the pre-adsorbed species and the ion beam characteristics: electronic stopping and fluence.
TL;DR: In this paper, two distinct hardening stages were observed in niobium irradiated at 25/sup 0/C to 10/sup 18/cm/sup -2/ with Be(d,n) neutrons and 16 MeV protons.
TL;DR: In this paper, the postannealed materials state has been examined using Rutherford backscattering spectrometry, proton-induced x-ray excitation, channeling, and transmission electron microscopy.
Abstract: Chromium‐implanted GaAs has been studied using 120 keV implants to fluence levels from 1×1014 to 5×1016 cm−2. The postannealed materials state has been examined using Rutherford backscattering spectrometry, proton‐induced x‐ray excitation, channeling, and transmission electron microscopy. Annealing was performed in flowing H2 at 900 C for 15 min under 85‐nm thick Si3N4 dielectric caps. Various stages of precipitation were observed having structure and composition that depended on total implanted fluence. For the highest fluence, coarse nonuniform second‐phase precipitates were present with dimensions on the order of 50 to 100 nm. At lower fluences small defect cluster precipitates, with average diameters of 6 nm, were identified through black‐white contrast analysis. The relative fraction of precipitated Cr was 40% at 1×1015 cm−2 and decreased to 9% at 5×1014 cm−2. The volume concentration of implanted Cr that is retained in solid solution after annealing is estimated at 2×1018 cm−3. Channeling analysis s...
TL;DR: In this paper, the authors measured ion profiles of 40 keV Ge into Si at increasing fluence using the RBS technique, and compared the results with the predictions of an analytical model encompassing sputter erosion plus atomic relocation.
Journal Article•
TL;DR: In this article, a simple model for particulate radiation damage in shallow-junction heteroface GaAs solar cells is used to evaluate the equivalent electron fluence concept especially in the sense of additivity of electron and proton exposure.
Abstract: A simple model for particulate radiation damage in shallow-junction heteroface GaAs solar cells is used to evaluate the equivalent electron fluence concept especially in the sense of additivity of electron and proton exposure. It is found that spatial dependent factors for low-energy proton exposure results in a dose dependent equivalent fluence ratio so that additivity within the equivalent fluence concept is generally not possible.
TL;DR: In this article, the behavior of the superconducting temperature and the lattice parameter of polycrystalline Nb3Si and Nb7Si thin films as a function of 300-kV α-particle fluence was investigated.
Abstract: The behavior of the superconducting temperatureT
c and the lattice parametera
0 of polycrystalline Nb3Si and Nb7Si thin films as a function of 300-kV α-particle fluence was investigated. It was found that theT
c depression of A15 Nb3Si is of the same size and nature as for other A15 materials. In contrast, the initialT
c degradation of Nb7Si is a factor of three larger. The observed minimum in theT
c vs fluence dependence of Nb3Si is discussed and a simple qualitative model is presented.
TL;DR: In this article, the influence of pulsed laser processing on the structure and composition of Si, GaAs, InP and Au surfaces has been investigated as a function of the laser fluence.
Abstract: The influence of pulsed laser processing (PLP) on the structure and composition of Si, GaAs, InP and Au surfaces has been investigated as a function of the laser fluence. Above a threshold fluence, all initial structures turn into a (1×1) structure and the V-element content of the compound surfaces is decreased. The structure change is shown to be related to the existence of a number of atomic steps on the PLP surface (up to 1014/cm2 equivalent broken bonds). These defects can be eliminated by further annealings. On the other hand, the stoechiometry defects, which are less numerous (1012–1013/cm2) cannot be eliminated. A model for the mechanisms of defect creation and annihilation during PLP is outlined. The incidence of PLP-induced defects on device technology is evaluated.
01 Sep 1982
TL;DR: In this paper, a simple model for particulate radiation damage in shallow-junction heteroface GaAs solar cells is used to evaluate the equivalent electron fluence concept especially in the sense of additivity of electron and proton exposure.
Abstract: A simple model for particulate radiation damage in shallow-junction heteroface GaAs solar cells is used to evaluate the equivalent electron fluence concept especially in the sense of additivity of electron and proton exposure. It is found that spatial dependent factors for low-energy proton exposure results in a dose dependent equivalent fluence ratio so that additivity within the equivalent fluence concept is generally not possible.
01 Jan 1982
TL;DR: In this paper, the equivalent fluence concept is defined and its use and potential problems are noted, and a comparison of silicon and GaAs solar cells in a radiation environment is presented.
Abstract: The equivalent fluence concept is defined, and its use and potential problems are noted. Silicon and GaAs solar cells are compared in a radiation environment. The analysis indicates that valid equivalent fluence values may be easier to obtain in GaAs than in silicon.
TL;DR: The dependence on the neutron energy, the angle of incidence and the fluence of organic solid state nuclear track detectors without external radiator for evaluating the etched detector foils by light transmission measurement was calculated in this paper.
TL;DR: In this article, a Pulsed Electron Beam Annealing (PEBA) was used to activate the N+ layer in the case of (100) and (111) silicon (140 keV-1012 cm−2).
Abstract: In this work Pulsed Electron Beam Annealing has been used to.activate As implanted in (100) and (111) silicon (140 keV-1012 cm−2). With a selected electron beam energy deposition profile excellent regrowth layer Quality and As activation has been obtained in the 1.2–1.4 J/cm fluence range. As redistribution is consistent with the melting model assuming a diffusivity of 10−4 cm2/s in liquid silicon. As losses might slightly reduce the carrier concentration near the surface in the case of (100) silicon. However a shallow and highly active N+ layer have been achieved with optimized PEBA conditions.