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At least 19 records
All sourcesNASA NTRSDOE OSTI
NASA NTRS1978

Density sensitivity of the solar EUV emission from boron-like ions

The paper investigated the level populations and the line emission arising from ions of the boron isoelectronic sequence from C II to Ca XVI. It is found that, under conditions present in the solar corona, some of these ions have pairs of emission lines having intensity ratios which are density-sensitive. The boron-like lines observed in the solar spectrum between 300 and 1350 A are analyzed, and densities for quiet and active regions, coronal holes, sunspots, and flares are derived. Some aspects of the differences in the behavior of the emission from the lithium and boron sequences are also discussed.

Vernazza, J. E.↗
NASA NTRS1988

Photoreflectance Study of Boron Ion-Implanted (100) Cadmium Telluride

Ion implanted (100) cadmium telluride was studied using the contactless technique of photoreflectance. The implantations were performed using 50- to 400-keV boron ions to a maximum dosage of 1.5 x 10(16)/sq cm, and the annealing was accomplished at 500 C under vacuum. The spectral measurements were made at 77 K near the E(0) and E(1) critical points; all the spectra were computer-fitted to Aspnes' theory. The spectral line shapes from the ion damaged, partially recovered and undamaged, or fully recovered regions could be identified, and the respective volume fraction of each phase was estimated.

Amirtharaj, P. M.↗
NASA NTRS1994

Atomic data from the iron project. 3: Rate coefficients for electron impact excitation of boron-like ions: Ne VI, Mg VIII, Al IX, Si X, S XII, Ar XIV, Ca XVI and Fe XXII

Collison strengths and maxwellian averaged rate coefficients have been calculated for the 105 transitions among all 15 fine structure levels of the 8 LS terms 2s(sup 2) 2 P(P-2(sup 0 sub 1/, 3/2)), 2s2p(sup 2)(P-4(sub 1/2,3/2,5/2), D-2(sub 3/2, 5/2), S-2(sub 1/2), P-2(sub 1/2, 3/2)), 2p(sup 3)(S-4(sup 0)(sub 3/2), D-2(sup 0 sub 3/2, 5/2), P-2(sup 0 sub 1/2, 3/2)) in highly- charged B-like Ne, Mg, Al, Si, S, Ar, Ca and Fe. Rate coefficients have been tabulated at a wide range of temperatures, depending on the ion charge and abundance in plasma sources. Earlier work for O IV has also been extended to include the high temperature range. A brief discussion of the calculations, sample results, and comparison with earlier works is also given. While much of the new data should be applicable to UV spectral diagnostics, the new rates for the important ground state fine structure transition P-2(sup 0 sub 1/2)-P-2(sup 0 sub 3/2) should result in significant revision of the IR cooling rates in plasmas where B-like ions are prominent constituents, since the new rate coefficients are generally higher by several factors compared with the older data.

Zhang, Hong Lin↗
NASA NTRS1999

Low-Energy Sputtering Studies of Boron Nitride with Xenon Ions

Sputtering of boron nitride with xenon ions was investigated using secondary ion (SIMS) and secondary neutral (SNMS) mass spectrometry. The ions generated from the ion gun were incident on the target at an angle of 50' with respect to the surface'normal. The energy of ions ranged from 100 eV to 3 keV. A flood electron gun was used to neutralize the positive charge build-up on the target surface. The intensities of sputtered neutral and charged particles, including single atoms, molecules, and clusters, were measured as a function of ion energy. Positive SIMS spectra were dominated by the two boron isotopes whereas BN- and B- were the two major constituents of the negative SIMS spectra. Nitrogen could be detected only in the SNMS spectra. The intensity-energy curves of the sputtered particles were similar in shape. The knees in P-SIMS and SNMS intensity-energy curves appear at around I keV which is significantly higher that 100 to 200 eV energy range at which knees appear in the sputtering of medium and heavy elements by ions of argon and xenon. This difference in the position of the sputter yield knee between boron nitride and heavier targets is due to the reduced ion energy differences. The isotopic composition of secondary ions of boron were measured by bombarding boron nitride with xenon ions at energies ranging from 100 eV to 1.5 keV using a quadrupole mass spectrometer. An ion gun was used to generate the ion beam. A flood electron gun was used to neutralize the positive charge buildup on the target surface. The secondary ion flux was found to be enriched in heavy isotopes at lower incident ion energies. The heavy isotope enrichment was observed to decrease with increasing primary ion energy. Beyond 350 eV, light isotopes were sputtered preferentially with the enrichment increasing to an asymptotic value of 1.27 at 1.5 keV. The trend is similar to that of the isotopic enrichment observed earlier when copper was sputtered with xenon ions in the same energy range.

Ray, P. K.↗
NASA NTRS1991

Ion-implanted extrinsic Ge photodetectors with extended cutoff wavelength

Far-IR Ge detectors fabricated using boron ion implantation are shown to exhibit operating characteristics compatible with requirements for low background applications. Device parameters such as low dark currents, reasonably good sensitivity, and extended wavelength threshold demonstrate that ion-implanted Ge far-IR detectors offer promise for use in astrophysics instrumentation.

Wu, I. C.↗
NASA NTRS1989

Fundamental tribological properties of ion-beam-deposited boron nitride films

The adhesion, friction, and micromechanical properties of ion-beam-deposited boron nitride (BN) films are reviewed. The BN films are examined in contact with BN metals and other harder materials. For simplicity of discussion, the tribological properties of concern in the processes are separated into two parts. First, the pull-off force (adhesion) and the shear force required to break the interfacial junctions between contacting surfaces are discussed. The effects of surface films, hardness of metals, and temperature on tribological response with respect to adhesion and friction are considered. The second part deals with the abrasion of the BN films. Elastic, plastic, and fracture behavior of the BN films in solid-state contact are discussed. The scratch technique of determining the critical load needed to fracture interfacial adhesive bonds of BN films deposited on substrates is also addressed.

Miyoshi, Kazuhisa↗
NASA NTRS1990

Fundamental tribological properties of ion-beam-deposited boron nitride films

The adhesion, friction, and micromechanical properties of ion-beam-deposited boron nitride (BN) films are reviewed. The BN films are examined in contact with BN metals and other harder materials. For simplicity of discussion, the tribological properties of concern in the processes are separated into two parts. First, the pull-off force (adhesion) and the shear force required to break the interfacial junctions between contacting surfaces are discussed. The effects of surface films, hardness of metals, and temperature on tribological response with respect to adhesion and friction are considered. The second part deals with the abrasion of the BN films. Elastic, plastic, and fracture behavior of the BN films in solid-state contact are discussed. The scratch technique of determining the critical load needed to fracture interfacial adhesive bonds of BN films deposited on substrates is also addressed.

Miyoshi, K.↗
NASA NTRS1979

Development of pulsed processes for the manufacture of solar cells

Low-energy ion implantation processes for the automated production of silicon solar cells were investigated. Phosphorus ions at an energy of 10 keV and dose of 2 x 10 to the 15th power/sq cm were implanted in silicon solar cells to produce junctions, while boron ions at 25 keV and 5 x 10 to the 15th power were implanted in the cells to produce effective back surface fields. An ion implantation facility with a beam current up to 4 mA and a production throughput of 300 wafers per hour was designed and installed. A design was prepared for a 100 mA, automated implanter with a production capacity of 100 MW sub e/sq cm per year. Two process sequences were developed which employ ion implantation and furnace or pulse annealing. A computer program was used to determine costs for junction formation by ion implantation and various furnace annealing cycles to demonstrate cost effectiveness of these methods.

Minnucci, J. A.↗
NASA NTRS1987

Mechanical strength and tribological behavior of ion-beam deposited boron nitride films on non-metallic substrates

An investigation was conducted to examine the mechanical strength and tribological properties of boron nitride (BN) films ion-beam deposited on silicon (Si), fused silica (SiO2), gallium arsenide (GaAs), and indium phosphide (InP) substrates in sliding contact with a diamond pin under a load. The results of the investigation indicate that BN films on nonmetallic substrates, like metal films on metallic substrates, deform elastically and plastically in the interfacial region when in contact with a diamond pin. However, unlike metal films and substrates, BN films on nonmetallic substrates can fracture when they are critically loaded. Not only does the yield pressure (hardness) of Si and SiO2 substrates increase by a factor of 2 in the presence of a BN film, but the critical load needed to fracture increases as well. The presence of films on the brittle substrates can arrest crack formation. The BN film reduces adhesion and friction in the sliding contact. BN adheres to Si and SiO2 and forms a good quality film, while it adheres poorly to GaAs and InP. The interfacial adhesive strengths were 1 GPa for a BN film on Si and appreciably higher than 1 GPa for a BN film on SiO2.

Miyoshi, Kazuhisa↗
NASA NTRS1987

Mechanical strength and tribological behavior of ion-beam-deposited boron nitride films on non-metallic substrates

An investigation was conducted to examine the mechanical strength and tribological properties of boron nitride (BN) films ion-beam deposited on silicon (Si), fused silica (SiO2), gallium arsenide (GaAs), and indium phosphide (InP) substrates in sliding contact with a diamond pin under a load. The results of the investigation indicate that BN films on nonmetallic substrates, like metal films on metallic substrates, deform elastically and plastically in the interfacial region when in contact with a diamond pin. However, unlike metal films and substrates, BN films on nonmetallic substrates can fracture when they are critically loaded. Not only does the yield pressure (hardness) of Si and SiO2 substrates increase by a factor of 2 in the presence of a BN film, but the critical load needed to fracture increases as well. The presence of films on the brittle substrates can arrest crack formation. The BN film reduces adhesion and friction in the sliding contact. BN adheres to Si and SiO2 and forms a good quality film, while it adheres poorly to GaAs and InP. The interfacial adhesive strengths were 1 GPa for a BN film on Si and appreciably higher than 1 GPa for a BN film on SiO2.

Miyoshi, Kazuhisa↗
NASA NTRS1981

Diagnostic study of BSF silicon solar cells

Solar cells equipped with back surface fields (BSF) were fabricated by means of an aluminum alloy, boron diffusion, and boron ion implantation. The importance of initial thickness, resistivity, orientation, and the crystal growth method were examined. Aluminum in paste form was screen printed on the cell, followed by alloy formation at 800 C for a minute. Application of the BSFs resulted in open circuit voltage improvements dependent on the substrate resistivity, ranging from 10 mV at 0.3 ohm-cm to 50 mV at 15 ohm-cm. The gains in performance were attributed to a longer penetration depth, a heightened concentration profile at the interface, and higher concentrations in the p+ layer.

Yoo, H.↗
NASA NTRS1998

Isotopic Enrichment of Boron in the Sputtering of Boron Nitride with Xenon Ions

An experimental study is described to measure the isotopic enrichment of boron. Xenon ions from 100 eV to 1.5 keV were used to sputter a boron nitride target. An ion gun was used to generate the ion beam. The ion current density at the target surface was approximately 30 microA/sq cm. Xenon ions impinged on the target surface at 50 deg angle to the surface normal. Since boron nitride is an insulator, a flood electron gun was used in our experiments to neutralize the positive charge buildup on the target surface. The sputtered secondary ions of boron were detected by a quadrupole mass spectrometer. The spectrometer entrance aperture was located perpendicular to the ion beam direction and 10 mm away from the target surface. The secondary ion flux was observed to be enriched in the heavy isotopes at lower ion energies. The proportion of heavy isotopes in the sputtered secondary ion flux was found to decrease with increasing primary ion energy from 100 to 350 eV. Beyond 350 eV, light isotopes were sputtered preferentially. The light isotope enrichment factor was observed to reach an asymptotic value of 1.27 at 1.5 keV. This trend is similar to that of the isotopic enrichment observed earlier when copper was sputtered with xenon ions in the same energy range.

Ray, P. K.↗
NASA NTRS1987

Adhesion, friction, and deformation of ion-beam-deposited boron nitride films

The tribological properties and mechanical strength of boron nitride films were investigated. The BN films were predominantly amorphous and nonstoichiometric and contained small amounts of oxides and carbides. It was found that the yield pressure at full plasticity, the critical load to fracture, and the shear strength of interfacial adhesive bonds (considered as adhesion) depended on the type of metallic substrate on which the BN was deposited. The harder the substrate, the greater the critical load and the adhesion. The yield pressures of the BN film were 12 GPa for the 440C stainless steel substrate, 4.1 GPa for the 304 stainless steel substrate, and 3.3 GPa for the titanium substrate.

Miyoshi, Kazuhisa↗
NASA NTRS1987

Adhesion, friction and deformation of ion-beam-deposited boron nitride films

The tribological properties and mechanical strength of boron nitride films were investigated. The BN films were predominantly amorphous and nonstoichiometric and contained small amounts of oxides and carbides. It was found that the yield pressure at full plasticity, the critical load to fracture, and the shear strength of interfacial adhesive bonds (considered as adhesion) depended on the type of metallic substrate on which the BN was deposited. The harder the substrate, the greater the critical load and the adhesion. The yield pressures of the BN film were 12 GPa for the 440C stainless steel substrate, 4.1 GPa for the 304 stainless steel substrate, and 3.3 GPa for the titanium substrate.

Miyoshi, K.↗
NASA NTRS1985

Tribological properties of boron nitride synthesized by ion beam deposition

The adhesion and friction behavior of boron nitride films on 440 C bearing stainless steel substrates was examined. The thin films containing the boron nitride were synthesized using an ion beam extracted from a borazine plasma. Sliding friction experiments were conducted with BN in sliding contact with itself and various transition metals. It is indicated that the surfaces of atomically cleaned BN coating film contain a small amount of oxides and carbides, in addition to boron nitride. The coefficients of friction for the BN in contact with metals are related to the relative chemical activity of the metals. The more active the metal, the higher is the coefficient of friction. The adsorption of oxygen on clean metal and BN increases the shear strength of the metal - BN contact and increases the friction. The friction for BN-BN contact is a function of the shear strength of the elastic contacts. Clean BN surfaces exhibit relatively strong interfacial adhesion and high friction. The presence of adsorbates such as adventitious carbon contaminants on the BN surfaces reduces the shear strength of the contact area. In contrast, chemically adsorbed oxygen enhances the shear strength of the BN-BN contact and increases the friction.

Miyoshi, K.↗
NASA NTRS1985

Tribological properties of boron nitride synthesized by ion beam deposition

The adhesion and friction behavior of boron nitride films on 440 C bearing stainless steel substrates was examined. The thin films containing the boron nitride were synthesized using an ion beam extracted from a borazine plasma. Sliding friction experiments were conducted with BN in sliding contact with itself and various transition metals. It is indicated that the surfaces of atomically cleaned BN coating film contain a small amount of oxides and carbides, in addition to boron nitride. The coefficients of friction for the BN in contact with metals are related to the relative chemical activity of the metals. The more active the metal, the higher is the coefficient of friction. The adsorption of oxygen on clean metal and BN increases the shear strength of the metal - BN contact and increases the friction. The friction for BN-BN contact is a function of the shear strength of the elastic contacts. Clean BN surfaces exhibit relatively strong interfacial adhesion and high friction. The presence of adsorbates such as adventitious carbon contaminants on the BN surfaces reduces the shear strength of the contact area. In contrast, chemically adsorbed oxygen enhances the shear strength of the BN-BN contact and increases the friction.

Miyoshi, K.↗
NASA NTRS1980

Improved process control for VMOS FET's

Method is applied in middle of fabrication process: (a) after mask region is formed, diffused-boron region is etched; (b) etching is left incomplete for ion implantation; (c) boron ions are implanted into region to define accurately crucial geometry of V-groove; (d) groove is etched to completion, forming two well-defined diffusion regions that serve as source and drain of transistor. Remaining process is conventional.

Jhabvala, M. D.↗
NASA NTRS1986

Use of low-energy hydrogen ion implants in high-efficiency crystalline-silicon solar cells

The use of low-energy hydrogen implants in the fabrication of high-efficiency crystalline silicon solar cells was investigated. Low-energy hydrogen implants result in hydrogen-caused effects in all three regions of a solar cell: emitter, space charge region, and base. In web, Czochralski (Cz), and floating zone (Fz) material, low-energy hydrogen implants reduced surface recombination velocity. In all three, the implants passivated the space charge region recombination centers. It was established that hydrogen implants can alter the diffusion properties of ion-implanted boron in silicon, but not ion-implated arsenic.

Fonash, S. J.↗