Showing papers on "Fluence published in 1981"

Electrical properties of laser chemically doped silicon

Abstract: The electrical properties of single‐crystal and amorphous Si, doped using a pulsed UV laser, have been studied as a function of laser wavelength and fluence and of UV dose BCl3 or PCl3 parent gases were used to provide B or P dopant atoms Dissociation of molecules adsorbed on the Si surface can supplement photolysis of gas‐phase molecules as a source of doping atoms

Measurements of deep penetration of low‐energy electrons into metal‐oxide‐semiconductor structure

Abstract: A polycrystalline Si‐SiO2‐Si metal‐oxide‐semiconductor (MOS) transistor covered with thick insulation and passivation layers of SiO2 was examined to measure the threshold voltage shifts as a function of electron energy over the range of from 5 to 18 keV. The electron‐beam fluence was varied over six orders of magnitude from 2×10−9 to 2×10−3 C/cm2. From the experimental data, the fraction of the incident electron energy deposited in the gate oxide was determined. The result shows a deep penetration of low‐energy electrons beyond the electron range.

The origin of the infrared multiphoton induced luminescence of chromyl chloride

Abstract: We have studied systematically the luminescence induced when CrO2Cl2 is infrared multiphoton excited by a moderate fluence (0–15 J/cm2) CO2 laser. This includes the dependence of the full luminescence spectrum on CO2 laser fluence, and for various spectral regions of the luminescence their dependence on CO2 laser wavelength and fluence, their intramolecular decay rates, and using a time‐of‐flight technique the translational temperatures associated with their sources. These measurements show that two species contribute to the luminescence. In addition, a chemical identification of these species is made by preceding the IR laser pulse with a UV laser pulse to photochemically prepare the CrO2Cl fragment, and isolate its contribution to the luminescence. Strong evidence is obtained in support of both CrO2Cl fragment and CrO2Cl2 parent contributions to the luminescence. The relative contributions of the two to the luminescence and an absolute yield for the IR multiphoton induced dissociation of CrO2Cl2 into Cr...

Infrared multiphoton energy deposition in CF2HCl

Abstract: Energy absorption by CF2HCl from an intense CO2 laser pulse is measured as a function of the laser energy fluence, the temperature, the pressure of CF2HCl, and the pressure of Ar bath gas. For collision free multiphoton absorption the average number of photons absorbed per molecule increases from two to neary 12 when the fluence is increased from 1.6 to 10.9 J cm−2 at 298 K. Comparison of absorption and dissociation data measured under identical conditions indicates relatively wide internal energy distributions produced by the multiphoton excitation. At 3 J cm−2 the average number of photons absorbed per molecule increases with increasing temperature betwen 300 and 450 K, whereas in the same temperature range at 10.7 J cm−2 a pronounced maximum is found in the absorption near 370 K. In the presence of 1 atm of added argon, an average of as many as 100 photons per molecule of CF2HCl can be absorbed as compared to the 18 photons necessary for collisionless dissociation.

As‐implanted and redistributed annealed depth distributions, range‐energy data, and shape factors for Cr implanted into crystalline GaAs and Si

Abstract: Depth distributions, range‐energy curves, and the Pearson IV moments are given for Cr implantation into crystalline GaAs and Si as a function of ion energy from 40 to 600 keV at 4×1013 cm−2 fluence, and as a function of ion fluence from 4×1012 to 2×1016 cm−2 at 300‐keV ion energy. The nature of the redistribution of these Cr profiles upon annealing at 840 °C for 20 min in both GaAs and in Si are shown and agree qualitatively in the two materials. Two general types of redistribution occur for 4×1013 cm−2 fluence, one for ion energies below and one for energies above about 100 keV.

Irradiation Effects in the Amorphous Alloy Fe40Ni40P14B6

Abstract: The effects of helium ion irradiation on the amorphous alloy Fe40Ni40P14B6 have been studied. Surface blistering is observed after irradiation at 40 keV with a total fluence of 1018 ions/cm2. A conversion electron Mossbauer spectrum of the irradiated alloy shows eminent paramagnetic peaks in the damaged region and reveals no peak corresponding to the ferromagnetic phases which are observed in the heat-treated specimen. The irradiation results in a different crystalline phase from that obtained by heat-treatment.

Dielectric Conductivity Effects at High Fluence in Filled Cables with Small Residual Gaps

Abstract: For high fluence applications system designers consider using hardened cables wherein the large (several mil) gaps between the braided shield and wire dielectrics are filled with a low atomic number dielectric. However, experiments indicate that the filling process is imperfect and small gaps on the order of several microns remain. These residual gaps can significantly enhance the x-ray response of the cable. In this paper we consider the high fluence (1 to 20 cal/cm2) common mode x-ray response of such an imperfectly-filled cable, accounting for induced dielectric conductivity effects.

Electrical Activation and Impurity Redistribution During Pulsed Laser Annealing of BF 2 + Implanted Amorphized Silicon

Abstract: Results of experiments studying the electrical activation and impurity redistribution during annealing of BF 2 +implanted amorphized silicon with a Q-switched Nd:glass laser ( \lambda , = 1.06 µm) of 27.5 nm full-width half-maximum (FWHM) are presented. The experimental results are explained on the basis of a thermal melting model. The laser fluence necessary to initiate melting of the front surface was determined using time-resolved reflectivity measurements. The samples irradiated with laser fluences just below the melting threshold and with higher fluences producing melting to successively deeper regions inside the material were specifically investigated. It was found that for full electrical activation, the laser fluence should be large enough to melt past the original amorphouscrystalline interface and the underlying damaged layer, leading to liquid phase epitaxial regrowth and ~100 percent electrical activation.

A Microstructural Interpretation of the Fluence and Temperature Dependence of the Mechanical Properties of Irradiated AISI 316

Abstract: The effects of neutron irradiation on the mechanical properties of annealed and 20 percent cold-worked AISI 316 irradiated in the experimental breeder reactor II were determined for the temperature regime of 370 to 760°C for fluences up to 8.4 × 10 2 2 neutrons (n)/cm 2 (E > 0.1 MeV). At irradiation temperatures below about 500°C, both annealed and cold-worked material exhibit a substantial increase in the flow stress with increasing fluence. Furthermore, both materials eventually exhibit the same flow stress, which is independent of fluence. At temperatures in the range of 538 to 650°C, the cold-worked material exhibits a softening with eventual saturation of the flow stress with increasing fluence. Annealed AISI 316 in this temperature regime exhibits hardening and, at a fluence of 2 to 3 × 10 2 2 n/cm 2 (E > 0.1 MeV), reaches the same value of flow stress as the cold-worked material. These observations are explained in terms of the fluence and temperature dependence of the irradiation-induced microstructure. It has been shown that AISI 316 proceeds toward an equilibrium dislocation and Frank-loop microstructure that is independent of the initial microstructure. There is a significant hardening that arises from the precipitation of small γ' and G-phase particles, both of which are formed only during irradiation and develop at temperatures less than about 550°C. Voids and Frank loops also produce hardening and exhibit a strong temperature dependence. Very good agreement between the observed data and calculated strengths was obtained for both solution-annealed and cold-worked AISI 316 through the use of simple hardening expressions for each type of microstructural defect. Extrapolation of these results to other reactor systems will lead to slightly different results because of flux and spectral effects on microstructural development.

Characterization Of Thermal Annealing Of Implanted GaAs Using Raman Scattering

Abstract: Raman spectra were recorded in backscattering from (100) oriented, Cr-doped, semi-insulating crystalline wafers of GaAs to characterize the changes introduced by implan-tation and by encapsulation and thermal anneal15ing. The studies were carried out at 300 and 100K. Implant fluences of lx1012 to 1x1015 S-ions/cm2 at 120 keV were used. Annealing temperatures ranged from 750 to 950°C for 15 minutes. The encapsulation was by means of rf-plasma-deposited Si3N4 films. The characteristics of a fixed annealing pro-cedure as a function of fluence and a fixed fluence at different annealing temperatures were determined. Unprocessed samples and a laser-annealed sample were studied. A pulsed, doubled YAG laser at 532 nm was used with about 16 mW of incident power in a 0.12-mm-diameter spot. A "triple" spectrometer, gated photon counting and computer pro-cessing of data were used. Following are the results: (1) the intensity of the LO pho-non line strongly varied with both implant dosage and annealing including a five-fold enhancement at 1012 S-ions/cm2 fluence, (2) the LO mode "softened" apparently due to implant-induced bond weakening, (3) polycrystalline and amorphous conditions of the implanted layer were identified, (4) thermal annealing itself was found to introduce disorder in the surface, at least for temperatures above 850°C, and (5) removal of amor-phous regions by laser annealing was observed.© (1981) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

Effects of Low Temperature Periodic Annealing on the Deep-Level Defects in 200 KeV Proton Irradiated AlGaAs-GaAs Solar Cells

Abstract: Low temperature thermal annealing (200 to 400 °C) has been shown to be effective in reducing densities of deep-level defects induced by proton irradiation in AlGaAs-GaAs solar cells. The purpose of this paper is to report our study of the effect of periodic thermal annealing on the deep level defects induced by the 200 keV proton irradiation. The AlGaAs-GaAs mesa diodes were initially irradiated at room temperature by 200 keV protons to a fluence of 1011 P/cm2, and were annealed at 200 °C, 300 °C, and 400 °C, respectively. The samples were repeatedly irradiated by the same proton fluence and then annealed at 200, 300, and 400 °C up to four irradiation and annealing cycles. The DLTS, C-V, and I-V measurements were made on these samples to determine the defect and recombination parameters as functions of proton fluence (1011 to 4×1011 P/cm2) and annealing temperature (200 to 400 °C). The results showed that densities of both electron and hole traps as well as recombination current decrease with increasing annealing temperature. For comparison, some samples were also irradiated once at a fluence of 1011, 2×1011, 3×1011, and 4×1011 P/cm2, and annealed at 200, 300, and 400 °C for six hours, respectively. No significant difference was found in defect density between the periodic and non-periodic annealed samples. The observed main electron trap was due to Ec-0.71 eV while the main hole trap was due to Ev+0.18 eV, for the 200 keV proton irradiated GaAs solar cells.

Helium breakdown by DF laser radiation

Abstract: Thresholds have been measured for the breakdown of helium by laser radiation near 38 μm in wavelength Four‐μsec chemical laser pulses were focused to a well‐defined spot 100 μm in diameter Values of the instantaneous irradiance qt and the accumulated fluence et occurring at time of breakdown were observed as a function of helium pressure in the range 012–099 atm The measured qt was 23 ×1010 W/cm2 at 1 atm, in good agreement with results scaled from other wavelengths

Performance of high resistivity n+pp+ silicon solar cells under 1 MeV electron irradiation

Abstract: High resistivity (1250 and 84 ohm-cm) n(+)pp(+) silicon solar cells were irradiated and their performance evaluated as a function of fluence. The greatest degradation in power occurred for the higher resistivity cell. The data were analyzed under open circuit conditions, and the components of V sub oc determined as a function of fluence. It was found that the voltage contributions from the front and back junctions decreased while the base component (V sub B) increased with fluence. The anomalous behavior of V sub B was attributed to an increase in the base minority carrier gradient with fluence. An argument that the increased power degradation in the 1250 ohm-cm cells was attributable to an increased voltage drop in the base is presented. Diffusion lengths calculated under high injection conditions were significantly greater than those determined under low injection. This was attributed to a saturation of recombination centers under high injection conditions.

Damage and coefficients and thermal annealing of irradiated silicon and GaAs solar cells

Abstract: Electron and proton damage coefficients have been measured for several types of silicon cells of recent manufacture using 1 MeV electrons and protons with energies of 8.3, 17.5 and 40 MeV. LPE (AlGa)As-GaAs cells were also irradiated and pseudodamage coefficients derived under the assumption that the irradiation changes the diffusion length in only one of the n- or p-type layers. After irradiation the cells were annealed isochronally up to 450 C. The damage coefficient and annealing data for silicon cells are in substantial agreement with previous work. The GaAs cells have pseudo-damage coefficients which are dependent on fluence, and have about the same energy dependence as Si damage coefficients.

Pulsed Electron Beam Annealing Ion Implanted Materials: Equipment and Results

Abstract: A series of pulsed electron beam accelerators has been developed for the modification of material surfaces. Each facility produces an electron beam with an average particle energy of 10-100 keV, a fluence of 0.5 to 10 J/cm2 on the sample, and a pulse width of 20-200 nsec. The total energy stored (per pulse) varies between the different models from 15 to 1500J with a maximum repetition rate of 0.5 Hz. The uniform beam has a diameter of 1-10 cm. These accelerators are used for annealing ion implants. After processing, the surface exhibits perfect, dislocation-free crystal regrowth for single crystal materials. A variety of discrete electronic devices have been fabricated with characteristics comparable to those observed with optimum thermal (furnace) annealing procedures. The first production application of pulsed electron beam annealing will be for solar cell junction fabrication, where the high speed (1800 four-inch-diameter wafers per hour) and low power consumption give a strong cost advantage over competing furnace or pulsed laser equipment.

Radiant energy conversion

Abstract: A radiant energy conversion system capable of receiving input energy (20) in thermal or radiant form at a variable rate, and releasing energy in thermal, radiant or electrical form independent of rate has a thermal energy storage of a material (23) that has three criteria, a melting temperature of not less than 960°C and preferably about 1027°C, a thermal conductivity greater than 0.4184 watts per metre Kelvin (0.1 calories per square centimetre per centimetre per degree per second) and a latent heat of fusion of more than 4.184 kilojoules (1 kilocalorie) per mole. The converter can absorb energy of multiple types, store it and then release it in a form compatible with the prospective use. Sunlight of daylight duration and varying intensity can be converted to steady 24 hour a day electrical output (30).