SEARCH · Engineering Papers
Results for “silicon processing”
Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.
Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.
Design and Characterization of a MEMS Probe Scanner for On-chip Atomic Force Microscopy
This paper presents the design and characterization of a microelectromechanical systems (MEMS)-based probe scanner proposed to function as an on-chip atomic force microscope (AFM). The device comprises an in-plane stage with electrostatic actuators and electrothermal displacement sensors. The stage is able to precisely position an AFM probe over a sample to perform tapping-mode AFM imaging. For implementation, a standard silicon-on-insulator (SOI) microfabrication process is used. In a previously reported design, the embedded AFM probe featured only one piezoelectric transducer for simultaneous actuation and sensing, making its use in imaging problematic. To address this issue, the new design features separate actuation and sensing AlN piezoelectric transducers. An extra electrode is also incorporated on the probe that enables canceling the electrical feedthrough from the actuation to sensing. To accommodate the extra signal routing paths, mechanical design of the probe scanner is modified. Device characterization reveals an in-plane displacement range of 8 µm×7 µm with a bandwidth of up to 2.7 kHz. The frequencydomain behavior of the AFM probe is also studied and feedthrough cancellation is performed at the resonant frequency of 127.35 kHz.
Coupled Thermo-Mechanical and Photo-Chemical Degradation Mechanisms that determine the Reliability and Operational Lifetimes for CPV Technologies
This project sought to identify and characterize the coupled intrinsic photo-chemo-mechanical degradation mechanisms that determine the reliability and operational lifetimes for CPV technologies. Over a three year period, we have completed a highly successful program which has developed quantitative metrologies and detailed physics-based degradation models, providing new insight into the fundamental reliability physics necessary for improving materials, creating accelerated testing protocols, and producing more accurate lifetime predictions. The tasks for the program were separated into two focus areas shown in the figure below. Focus Area 1, led by Reinhold Dauskardt and Warren Cai with a primary collaboration with David Miller of NREL, studied the degradation mechanisms present in encapsulant materials. Focus Area 2, led by Reinhold Dauskardt and Ryan Brock with a primary collaboration with James Ermer and Peter Hebert of Spectrolab, studied stress development and degradation within internal CPV device interfaces. Each focus area was productive, leading to several publications, including findings on the degradation of silicone encapsulant under terrestrial UV, a model for photodegradation of silicone encapsulant adhesion, quantification and process tuning of antireflective layers on CPV, and discovery of a thermal cycling degradation mechanism present in metal gridline structures.
Analyzing the Energy Performance, Wind Loading, and Costs of Photovoltaic Slat Modules on Commercial Rooftops
NREL studied a new type of photovoltaic (PV) module configuration wherein multiple narrow, tilted slats are mounted in a single frame. Each slat of the PV slat module contains a single row of cells and is made using ordinary crystalline silicon PV module materials and processes, including a glass front sheet and weatherproof polymer encapsulation. Compared to a conventional ballasted system, a system using slat modules offer higher energy production and lower weight at lower LCOE. The key benefits of slat modules are reduced wind loading, improved capacity factor and reduced installation cost. First, the individual slats allow air to flow through, which reduce wind loading. Using PV performance modeling software, we compared the performance of an optimized installation of slats modules to a typical installation of conventional modules in a ballasted rack mounting system. Based on the results of the performance modeling two different row tilt and spacing were tested in a wind tunnel. Scaled models of the PV Slat modules were wind tunnel tested to quantify the wind loading of a slat module system on a commercial rooftop, comparing the results to conventional ballasted rack mounted PV modules. Some commercial roofs do not have sufficient reserve dead load capacity to accommodate a ballasted system. A reduced ballast system design could make PV system installation on these roofs feasible for the first time without accepting the disadvantages of penetrating mounts. Finally, technoeconomic analysis was conducted to enable an economic comparison between a conventional commercial rooftop system and a reduced-ballast slat module installation.
Exotic armalcolite and the origin of Apollo 11 ilmenite basalts
Armalcolite and ilmenite basalt in Apollo 11 lunar samples, discussing formation process of titanium, potassium and silicon oxides
A reliable all-silver front contact for silicon solar cells.
Methods have been found to apply an adherent and humidity resistant silver-only front contact to n on p silicon solar cells. The critical processing step was the removal of the diffused oxide layer. Humidity resistance is superior to present day commercial titanium-silver contacts and the electrical characteristics of the cells are excellent. Titanium, which is degraded by humidity and which is a source of heavy metal poisoning, has been eliminated from the contact.
Improving the toughness of refractory compounds
Composition and processing studies were conducted on silicon nitride and silicon carbide materials. Charpy mode impact testing to 2415 F established the effectiveness of higher purity silicon nitride powder sources in reducing the scatter of measurements and in improving short time bend strengths as well as bend stress rupture properties. Stabilized zirconia additions in particular were observed to dramatically enhance low and high temperature bend strengths and stress rupture properties for all grades of silicon nitride powder. Silicon carbide samples showed relatively poor impact resistance, although the maxima in stress rupture behavior was exhibited by this material.
Proximity sensor technology for manipulator end effectors
Optical proximity sensing devices suitable for hand mounting on a manipulator are described, which use near IR LED light sources operating at 0.94 micron and silicon detectors, with appropriate signal processing so that the data are unaffected by ambient light. Laboratory tests with simple proximity sensors are described. Extension of the same techniques to yield multipoint or digital sensors is also discussed. A cooperative proximity sensor concept is described, which employs a composite mirror attached to the work piece to generate an unambiguous set of position and orientation signals. A very rudimentary experiment in local control of a manipulator with a pair of hand mounted proximity sensors is also described.
The effect of secondary impurities on solar cell performance
Czochralski and float zone sigle crystals of silicon were doped with the primary impurities B or P so that a resistivity of 0.5 ohm cm resulted, and in addition doped with certain secondary impurities including Al, C, Cr, Cu, Fe, Mg, Mn, Na, Ni, O, Ti, V, and Zr. The actual presence of these impurities was confirmed by analysis of the crystals. Solar cell performance was evaluated and found to be degraded most significantly by Ti, V, and Zr and to some extent by most of the secondary impurities considered. These results are of significance to the low cost silicon program, since any such process would have to yield at least tolerable levels of these impurities.
Low-cost solar array project and Proceedings of the 15th Project Integration Meeting
Progress made by the Low-Cost Solar Array Project during the period December 1979 to April 1980 is described. Project analysis and integration, technology development in silicon material, large area silicon sheet and encapsulation, production process and equipment development, engineering, and operation are included.
The applicability of DOE solar cell and array technology to space power
Current trends in terrestrial photovoltaics that might benefit future space power needs are reviewed. Emphasis is placed on the Low-Cost Solar Array Project with attention given to the materials task, the silicon sheet task, the production processes and equipment task, and encapsulation. The Photovoltaic Concentrator Technology Development Project is also discussed. It is concluded that terrestrial photovoltaic technology that has either been developed to date or is currently under development will not have any significant effect on the performance or cost of solar cells and panels for space over the near term (1980-1990).
The 17th Project Integration Meeting
Progress made by the Low-Cost Solar Array Project during the period September 1980 to February 1981 is described. Included are reports on project analysis and integration; technology development in silicon material, large-area silicon sheet and encapsulation; production process and equipment development; engineering, and operations. A report on and copies of visual presentations made at the Project Integration Meeting held at Pasadena, California on February 4 and 5, 1981 are also included.
Separating Silicon and Sodium Fluoride by Melting
Silion is withdrawn from bottom of crucible, once two immiscible liquid stages form, in quasi-continuous method of separating silicon from other reaction products. Process is periodically halted to remove accumulated buildup of salts.
Progress Report 18 for the Period February to July 1981 and Proceeidngs of the 18th Project Integration Meeting
Progress in the low cost solar array project during the period February to July 1981 is reported. Included are: (1) project analysis and integration; (2) technology development in silicon material, large area silicon sheer and encapsulation; (3) process development; (4) engineering, and operations.
Ceramic technology for solar thermal receivers
The high-temperature capability, resistance to corrosive environments and non-strategic nature of ceramics have prompted applications in the solar thermal field whose advantages over metallic devices of comparable performance may begin to be assessed. It is shown by a survey of point-focusing receiver designs employing a variety of ceramic compositions and fabrication methods that the state-of-the-art in structural ceramics is not sufficiently advanced to fully realize the promised benefits of higher temperature capabilities at lower cost than metallic alternatives. The ceramics considered include alumina, berylia, magnesia, stabilized zirconia, fused silica, silicon nitride, silicon carbide, mullite and cordierite, processed by such methods as isostatic pressing, dry pressing, slip casting, extrusion, calendaring and injection molding.
Polycarbosilazane-Resin Polymerization Process
Process suitable for production of silicon nitride/silicon carbide fibers. High-tensile-strength silicon carbide/silicon nitride fibers prepared by pyrolyzing fibers drawn from melt of polycarbosilazane resin. Such fibers show promise as replacements for carbon fibers in high-strength composites for automotive, aerospace, and other applications where high electrical conductivity of carbon fibers makes them unsuitable.
The XPS depth profiling and tribological characterization of ion-plated gold on various metals
Friction properties were measured with a gold film; the graded interface between gold and nickel substrate; and the nickel substrate. All sliding was conducted against hard silicon carbide pins in two processes. In the adhesive process, friction arises primarily from adhesion between sliding surfaces. In the abrasion process, friction occurs as a result of the hard pin sliding against the film, indenting into it, and plowing a series of grooves. Copper and 440 C stainless steel substrates were also used. Results indicate that the friction related to both adhesion and abrasion is influenced by coating depth. The trends in friction behavior as a function of film depth are, however, just the opposite. The graded interface exhibited the highest adhesion and friction, while the graded interface resulted in the lowest abrasion and friction. The coefficient of friction due to abrasion is inversely related to the hardness. The greater the hardness of the surface, the lower is the abrasion and friction. The microhardness in the graded interface exhibited the highest hardness due to an alloy hardening effect. Almost no graded interface between the vapor-deposited gold film and the substrates was detected.
High-voltage solar-cell chip
Integrated circuit technology has been successfully applied to the design and fabrication of 0.5 x 0.5-cm planar multijunction solar-cell chips. Each of these solar cells consisted of six voltage-generating unit cells monolithically connected in series and fabricated on a 75-micron-thick, p-type, single crystal, silicon substrate. A contact photolithic process employing five photomask levels together with a standard microelectronics batch-processing technique were used to construct the solar-cell chip. The open-circuit voltage increased rapidly with increasing illumination up to 5 AM1 suns where it began to saturate at the sum of the individual unit-cell voltages at a maximum of 3.0 V. A short-circuit current density per unit cell of 240 mA/sq cm was observed at 10 AM1 suns.