Alkali semi-metal films and method and apparatus for fabricating them
Inventors
BHANDARI, Harish B. • Nagarkar, Vivek V. • Ovechkina, Olena E. • Frisch, Henry J. • Attenkofer, Klaus • Smedley, John M.
Assignees
University of Chicago • Radiation Monitoring Devices Inc • Brookhaven Science Associates LLC
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Publication Number
US-9916958-B1
Publication Date
2018-03-13
Expiration Date
Abstract
Methods and systems for fabricating a film, such as, for example, a photocathode, having a tailored band structure and thin-film components that can be tailored for specific applications, such as, for example photocathode having a high quantum efficiency, and simple components fabricated by those methods.
Core Innovation
The document describes a method for synthesizing an alkali semi-metal compound in which the semi-metal is a semi-metal in Group 15 and the alkali semi-metal compound is a crystal compound. The method comprises mixing at a temperature from about 15° C. to about 30° C. and at an ambient pressure from about 750 torr to about 800 torr at least two alkali materials to form an alloy composition, and mixing the alloy composition with a solid semi-metal material to form the alkali semi-metal compound. The alloy composition comprises a liquid alloy composition, and the at least two alkali materials comprise a first alkali material and a second alkali material.
The document also describes fabricating a thin film component by providing pre-synthesized semi-metal compound material that comprises one or more alkali materials and a semi-metal material, wherein the alkali semi-metal compound is a crystal compound. A thin film of the semi-metal compound material is deposited on a substrate to form the thin film component. Pre-synthesizing the semi-metal compound material includes mixing at the specified temperature and ambient pressure ranges to form the alloy composition and then mixing the solid semi-metal material and the alloy composition to form the alkali semi-metal compound.
Further, the document describes tailoring the deposited thin film component by co-evaporating, during deposition, at least one alkali material to alter alkali concentration along a direction perpendicular to the substrate, and activating a portion of the at least one alkali material by collisions in a sputter plasma. The method also includes applying a bias voltage on the substrate to preselect activated alkali implementation and keeping the substrate at a predetermined temperature during deposition to prevent migration and preserve a doping profile. The method further includes annealing the thin film component by heating at a predetermined temperature for a predetermined time, and preparing a substrate to obtain a predetermined crystallographic surface orientation.
In addition, the document describes fabricating a target for depositing an alkali semi-metal compound by loading the alkali semi-metal compound onto a target holder, where the semi-metal is a semi-metal in Group 15 and the alkali semi-metal compound is synthesized by forming an alkali alloy composition from at least two alkali materials and mixing that liquid alloy composition with a solid semi-metal material to form the crystal compound. A film is formed from the alkali semi-metal compound by pressing and packing, and a layer of a passivating material is deposited on a top surface of the film.
Claims Coverage
The partial content includes four independent claims. Across these claims, the inventive subject matter is organized around synthesizing a Group 15 alkali semi-metal crystal compound from an alkali alloy composition plus a solid semi-metal at specified temperature and pressure ranges, using pre-synthesized compound material to deposit thin film components on substrates, controlling deposition and annealing to alter alkali concentration and preserve a doping profile, and fabricating a target with a passivating layer.
Alloy-then-crystal synthesis of Group 15 alkali semi-metal crystal compounds
Mixing at a temperature from about 15° C. to about 30° C. and at an ambient pressure from about 750 torr to about 800 torr at least two alkali materials to form an alloy composition; and mixing at the same temperature and ambient pressure ranges a solid semi-metal material and the alloy composition to form the alkali semi-metal compound, wherein the semi-metal is a semi-metal in Group 15, wherein the at least two alkali materials comprise a first alkali material and a second alkali material, and wherein the alkali semi-metal compound is a crystal compound.
Pre-synthesized compound deposition to form a thin film component
Providing pre-synthesized semi-metal compound material comprising one or more alkali materials and a semi-metal material, wherein the alkali semi-metal compound is a crystal compound; pre-synthesizing the semi-metal compound material comprises mixing at a temperature from about 15° C. to about 30° C. and at an ambient pressure from about 750 torr to about 800 torr at least two alkali materials to form an alloy composition and mixing the solid semi-metal material and the alloy composition to form the alkali semi-metal compound; and depositing a thin film of the semi-metal compound material on a substrate to form the thin film component.
Thin film deposition with perpendicular alkali concentration control, plasma activation, and doping-profile preservation
Providing pre-synthesized semi-metal compound material comprising one or more alkali materials and a semi-metal material; depositing a thin film of the semi-metal compound material on a substrate to form the thin film component; co-evaporating, during deposition, at least one alkali material from the one or more alkali materials in order to alter alkali concentration along a direction perpendicular to the substrate; activating a portion of the at least one alkali material by collisions in a sputter plasma; applying a bias voltage on the substrate in order to preselect activated alkali implementation; keeping the substrate at a predetermined temperature during deposition in order to prevent migration and to preserve a doping profile; and annealing the thin film component by heating at a predetermined temperature for a predetermined time.
Target fabrication for depositing an alkali semi-metal compound using a passivated pressed-and-packed film
Loading the alkali semi-metal compound onto a target holder, wherein a semi-metal is a semi-metal in Group 15 synthesized by mixing at least two alkali materials to form an alloy composition and mixing a solid semi-metal material and the alloy composition to form the alkali semi-metal compound, wherein the alloy composition is a liquid alloy composition, wherein the one or more alkali materials comprise a first alkali material and a second alkali material, and wherein the alkali semi-metal compound is a crystal compound; forming a film from the alkali semi-metal compound by pressing and packing; and depositing a layer of a passivating material on a top surface of the film.
Across the independent claims, the document covers forming a Group 15 alkali semi-metal crystal compound by an alkali alloy formation step followed by mixing with a solid semi-metal at defined temperature and ambient pressure ranges, fabricating thin film components by depositing pre-synthesized alkali semi-metal crystal compound material onto a substrate, controlling deposition and annealing to alter alkali concentration and preserve a doping profile, and fabricating a passivated target using pressed-and-packed films of the alkali semi-metal compound.
Stated Advantages
Documented Applications
No documented applications found
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