Adsorbate analysis using optically stimulated electron emission
Inventors
Yost, William T. • Perey, Daniel F. • Petzar, Paul • Connell, John W. • Palmieri, Frank L. • Ledesma, Rodolfo I. • Brown, Joshua L.
Assignees
National Aeronautics and Space Administration NASA • Analytical Mechanics Associates Inc
Publication Number
US-12209980-B2
Publication Date
2025-01-28
Expiration Date
2039-05-03
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Abstract
A probe for collecting optically stimulated electron emission to inspect chemical reactions of a surface includes a light source to emit light on the surface, a collector, and a controller. The light source emits light on the surface. The collector is configured to detect photoelectrons emitted from the surface in response to the light from the light source impinging on the surface. The collector is further configured to provide a photocurrent based on the detected photoelectrons. The controller includes at least one processor and is operably coupled to the light source and the collector. The controller is configured to cause the light source to emit light on the surface, receive the photocurrent from the collector, and determine at least one chemical reaction of the surface based on the received photocurrent.
Core Innovation
The invention is a probe, system, and method for collecting optically stimulated electron emission (OSEE) to inspect chemical reactions of a surface by emitting light on the surface and detecting photoelectrons emitted in response. The probe includes a light source, a collector for photoelectrons, and a controller with at least one processor to emit light, receive photocurrent, and determine chemical reactions based on the photocurrent.
The technology addresses the need for improved analysis of photo-induced chemical reactions on surfaces, including those affected by electromagnetic radiation and involving metastable excited states that alter a substrate's work function and photo-emitting properties. It overcomes challenges of locating and measuring contaminants and understanding time-dependent complex kinetics of molecular and surface states that affect photoelectron emission.
The disclosure introduces a framework to measure kinetic constants on specific substrates to separate and specify reaction sequences, thus identifying steps in transformations via photocurrent time variation. The technology is capable of analyzing a variety of materials and complex surface chemistries, including catalysis, biological systems, and contaminants, by utilizing current-time relationships and spectral exposure to excited states causing changes in photo-electric emissions from substrate surfaces.
Claims Coverage
The patent includes multiple independent claims covering probes and systems for optically stimulated electron emission analysis of surfaces. The main inventive features focus on inducing photo-induced metastable states, detecting photocurrents, and analyzing decay constants to identify chemical reactions and surface properties.
Inducing and detecting surface-based photo-induced metastable states
A probe with a light source (ultraviolet light) to induce a sequence of surface-based photo-induced metastable states on a specimen, a collector to detect photoelectrons and provide photocurrent, and a controller to receive photocurrent and identify sequences of decay constants and metastable states based on the photocurrent.
Determining molecular patterns and surface compositions based on photocurrent analysis
Controller configured to determine molecular patterns, amounts of catalysts, and chemical compositions of the surface by analyzing identified sequences of surface-based photo-induced metastable states.
System with multiple OSEE pods for simultaneous surface analysis
A system comprising one or more OSEE pods each with ultraviolet light sources and collectors to induce metastable states, receive photocurrents, and identify sequences of decay constants and metastable states on different surface areas, allowing comparison across those areas.
Incorporation of reference pods for differential measurements
System including reference OSEE pods with light sources and collectors to measure reference surfaces, allowing identification of reference decay constants and comparing them to those of specimen surfaces to improve identification of reactions.
Analyzing full width at half maximum (FWHM) to characterize metastable states
Probe where the controller identifies FWHM associated with surface-based photo-induced metastable states via photocurrent measurements, where FWHM directly correlates with decay constants of the metastable states, providing additional identification capability.
The claims cover inventive features including inducing and detecting sequences of surface photo-induced metastable states via optically stimulated electron emission, analyzing photocurrent decay characteristics to identify reaction kinetics, determining surface molecular and catalyst compositions, utilizing multiple pods including reference pods for comprehensive analysis, and employing FWHM analysis for metastable state identification.
Stated Advantages
Improves reliability of bonding and provides various applications in chemical and biological laboratories.
Enables measurement of low levels of constituents on surfaces with various shapes to locate and measure contaminants.
Separates reactions by their kinetics constants through photocurrent time dependence, facilitating analysis of complex surface chemistries.
Sensitive to different molecular arrangements on surfaces, allowing identification of photo-induced reaction sequences and species.
Allows simultaneous multiple surface area measurements and compensates for environmental and surface contour variations.
Supports multiple light wavelengths and coherent radiation to selectively excite and analyze photo-induced reactions.
Provides new modeling and analytical methods for sequential evolution of adsorbates on surfaces, improving photo-chemical and photo-physical analyses.
Minimizes exposure to UV radiation while delivering dependable results and predictions of surface chemical effects.
Documented Applications
Analysis of adsorbates on substrates, including contaminants and residues from preparation, crop spraying, or cleaning.
Catalysis studies involving identification and monitoring of chemical and biological reactions on surfaces.
Inspection and mapping of aircraft fuselage surfaces, composite materials, and parts with varying geometries.
Differential comparison of surface reactivity and concentration gradients across different surface areas or reference surfaces.
Applications involving nanostructures, carbon composites, metals, semiconductors, and other conducting or photo-electron emitting substrates.
Measurement of surface states, including intermediate and metastable surface reactants in photo-induced chemical and physical processes.
Use in chemical, biological, and photo-physical laboratory environments for studying reactions involving light-induced excited states.
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