To reach high efficiencies, thermophotovoltaic cells must utilize the broad spectrum of a radiative thermal source. One promising approach to overcome this challenge is to have low-energy photons reflected and reabsorbed by the thermal emitter, where their energy can have another chance at contributing toward photogeneration in the cell. However, current methods for photon recuperation are limited by insufficient bandwidth or parasitic absorption, resulting in large efficiency losses relative to theoretical limits. This work demonstrates nearly perfect reflection of low-energy photons (99%) by embedding an air layer within the TPV cell. This result represents a four-fold reduction in parasitic absorption relative to existing TPV cells. As out-of-band reflectance approaches unity, TPV efficiency becomes nearly insensitive to cell bandgap and emitter temperature. Accessing this regime unlocks a range of possible materials and heat sources that were previously inaccessible to TPV energy conversion.

To reach high efficiencies, thermophotovoltaic cells must utilize the broad spectrum of a radiative thermal source. One promising approach to overcome this challenge is to have low-energy photons reflected and reabsorbed by the thermal emitter, where their energy can have another chance at contributing toward photogeneration in the cell. However, current methods for photon recuperation are limited by insufficient bandwidth or parasitic absorption, resulting in large efficiency losses relative to theoretical limits. This work demonstrates nearly perfect reflection of low-energy photons (99%) by embedding an air layer within the TPV cell. This result represents a four-fold reduction in parasitic absorption relative to existing TPV cells. As out-of-band reflectance approaches unity, TPV efficiency becomes nearly insensitive to cell bandgap and emitter temperature. Accessing this regime unlocks a range of possible materials and heat sources that were previously inaccessible to TPV energy conversion.

Methods are provided for generating a crystalline material. The methods comprise depositing a textured thin film in a growth seed area, wherein the textured thin film has a preferential crystallographic axis; providing a growth channel extending from the growth seed area, the growth channel permitting guided lateral growth; and growing a crystalline material in the growth channel along a direction that is substantially perpendicular to the preferential crystallographic axis of the textured thin film. A preferred crystalline material is gallium nitride, and preferred textured thin films are aluminum nitride and titanium nitride.

Methods are provided for generating a crystalline material. The methods comprise depositing a textured thin film in a growth seed area, wherein the textured thin film has a preferential crystallographic axis; providing a growth channel extending from the growth seed area, the growth channel permitting guided lateral growth; and growing a crystalline material in the growth channel along a direction that is substantially perpendicular to the preferential crystallographic axis of the textured thin film. A preferred crystalline material is gallium nitride, and preferred textured thin films are aluminum nitride and titanium nitride.

Disclosed are an alpha gallium oxide thin-film structure having high conductivity obtained using selective area growth in a HVPE growth manner, and a method for manufacturing the same, in which a nitride-based nitride film pattern is formed on an alpha gallium oxide thin-film so as to expose only a selected area thereof, and re-growth is performed only on the partially exposed area thereof, thereby forming a high-quality patterned alpha gallium oxide re-growth pattern.

Disclosed are an alpha gallium oxide thin-film structure having high conductivity obtained using selective area growth in a HVPE growth manner, and a method for manufacturing the same, in which a nitride-based nitride film pattern is formed on an alpha gallium oxide thin-film so as to expose only a selected area thereof, and re-growth is performed only on the partially exposed area thereof, thereby forming a high-quality patterned alpha gallium oxide re-growth pattern.

A method for preparing a large-scale two-dimensional single crystal material stack which has an interlayer rotation angle. Single crystal substrates are stacked and rotated at a specific angle, a two-dimensional single crystal material is epitaxial on the surface thereof, and then an upper layer and a lower layer of the two-dimensional single crystal material are attached, and a layer of the single crystal substrates on the surface is removed so as to obtain a two-dimensional single crystal stack which has a specific rotation angle. A large-scale two-dimensional single crystal material stack which has an interlayer rotation angle prepared by the described method.

A method for preparing a large-scale two-dimensional single crystal material stack which has an interlayer rotation angle. Single crystal substrates are stacked and rotated at a specific angle, a two-dimensional single crystal material is epitaxial on the surface thereof, and then an upper layer and a lower layer of the two-dimensional single crystal material are attached, and a layer of the single crystal substrates on the surface is removed so as to obtain a two-dimensional single crystal stack which has a specific rotation angle. A large-scale two-dimensional single crystal material stack which has an interlayer rotation angle prepared by the described method.

A method for substrate processing includes flowing one or more process reactive gases into an upper volume of a processing chamber, flowing cleaning gas into a lower volume of the processing chamber, measuring temperature of an inner surface of the lower volume of the processing chamber, and adjusting temperature of the inner surface of the lower volume of the processing chamber, based on the measured temperature.

A method for substrate processing includes flowing one or more process reactive gases into an upper volume of a processing chamber, flowing cleaning gas into a lower volume of the processing chamber, measuring temperature of an inner surface of the lower volume of the processing chamber, and adjusting temperature of the inner surface of the lower volume of the processing chamber, based on the measured temperature.