1) Field of the Disclosure
The disclosure relates to infrared-reflecting films. In particular, the disclosure relates to single layer infrared-reflecting films and a method of making the same wherein the films provide enhanced reflectivity in an 800 nanometer to 2500 nanometer infrared waveband.
2) Description of Related Art
Nearly 50% of incident solar power falls in the infrared (IR) waveband from 800 nanometers (nm) to 2500 nanometers (nm) in wavelength. It is therefore desirable to use infrared-reflecting films to enhance reflectivity in the IR waveband. Known infrared-reflecting films and methods for making the same exist. Such known infrared-reflecting films are typically manufactured using multilayers of two or more components with well-defined optical properties. The working principle is based on either optical interference or additive properties of individual components. Such multilayer films are typically synthesized by known techniques such as physical vapor deposition, chemical vapor deposition, or a sol-gel method. However, the manufacture of multiple layers can result in increased expense, complexity, and time to manufacture. Such multilayer films may not be suitable for industrial-scale processes due to higher costs. In addition, in the case of known interference films, interference between different layers may cause a colored appearance that is undesirable in certain applications.
Accordingly, there is a need for infrared-reflecting films and a method of making the same that provide advantages over known films and methods.
This need for improved infrared-reflecting films and a method of making the same is satisfied. None of the known films and methods provide all of the numerous advantages discussed herein. Unlike known films and methods, embodiments of the films and method of the disclosure may provide one or more of the following advantages: provides for single layer infrared-reflecting films and method for making the same that are simple, less expensive and time-consuming to make, and are suitable for industrial-scale manufacturing; provides for single layer infrared-reflecting films and method for making the same that use uniquely doped materials to reflect infrared radiation, transmit visible light, and absorb ultraviolet light to minimize degradation of materials; and provides for single layer infrared-reflecting films and method for making the same that enhance reflectivity in the 800 nm to 2500 nm IR waveband and reflect over a wide range of wavelengths and do not cause a colored appearance.
In one of the embodiments of the disclosure, there is provided a method for making a single layer infrared-reflecting film comprising the steps of: providing a substrate; depositing onto the substrate a mixture of an oxide matrix material and a conductive metal dopant; and, producing the infrared-reflecting film. The oxide matrix material may comprise titanium dioxide, zinc oxide, tin oxide, or another suitable oxide matrix material. The conductive metal dopant may comprise gold, silver, copper, or another suitable conductive metal dopant.
In another embodiment of the disclosure, there is provided a method for making a single layer infrared-reflecting film comprising the steps of: providing a substrate; depositing onto the substrate a mixture of an oxide matrix material and a higher valence cation; and, producing an infrared-reflecting film. The oxide matrix material may comprise titanium dioxide, zinc oxide, tin oxide, or another suitable oxide matrix material. The higher valence cation may comprise niobium, vanadium, tantalum, tungsten, chromium, or another suitable higher valence cation.
In another embodiment of the disclosure, there is provided a single layer infrared-reflecting film with enhanced reflectivity in an 800 nanometer to 2500 nanometer infrared waveband, the film comprising a mixture of an oxide matrix material and a conductive metal dopant over a substrate. The oxide matrix material may comprise titanium dioxide, zinc oxide, tin oxide, or another suitable oxide matrix material. The conductive metal dopant may comprise gold, silver, copper, or another suitable conductive metal dopant.
In another embodiment of the disclosure, there is provided a single layer infrared-reflecting film with enhanced reflectivity in an 800 nanometer to 2500 nanometer infrared waveband, the film comprising a mixture of an oxide matrix material and a higher valence cation over a substrate. The oxide matrix material may comprise titanium dioxide, zinc oxide, tin oxide, or another suitable oxide matrix material. The higher valence cation may comprise niobium, vanadium, tantalum, tungsten, chromium, or another suitable higher valence cation.
The features, functions, and advantages that have been discussed can be achieved independently in various embodiments of the present disclosure or may be combined in yet other embodiments further details of which can be seen with reference to the following description and drawings.
The disclosure can be better understood with reference to the following detailed description taken in conjunction with the accompanying drawings which illustrate preferred and exemplary embodiments, but which are not necessarily drawn to scale, wherein:
Disclosed embodiments will now be described more fully hereinafter with reference to the accompanying drawings, in which some, but not all of the disclosed embodiments are shown. Indeed, several different embodiments may be provided and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete and will fully convey the scope of the disclosure to those skilled in the art.
The infrared-reflecting films and method of the disclosed embodiments may be used in connection with enhancement of reflectivity in the 800 nm to 2500 nm infrared (IR) waveband. Accordingly, one of ordinary skill in the art will recognize and appreciate that the infrared-reflecting films and method of making the same of the disclosure can be used in any number of applications where enhancement of reflectivity in the 800 nm to 2500 nm IR waveband is desired.
The invention uses the principles of bulk and interface plasma resonance to create film materials that reflect IR radiation. When charged particles such as electrons are illuminated with electromagnetic (EM) radiation with a frequency less than a certain critical value, they are driven into acceleration and deceleration by the electric field of the incident EM waves at the same frequency. This, in turn, results in the emission of EM radiation at the same frequency. This is the origin of enhanced reflection of EM radiation by the medium of charged particles. The critical frequency is directly related to the dielectric properties of the medium. The single layer films disclosed are transparent to visible light and reflect IR radiation. The films demonstrate a 25-30% reflectivity of incident solar energy, which can result in a significant reduction in energy transmission through the films.
In one of the embodiments of the disclosure there is provided a method for making a single layer infrared-reflecting film. Preferably, the film is transparent.
The method further comprises step 44 (
Depositing of the oxide matrix material and conductive metal dopant may be carried out with a conventional deposition method and apparatus. Such deposition methods and apparatuses that may be used may comprise physical vapor deposition, such as sputter deposition, pulsed laser deposition, electron beam physical vapor deposition, evaporative deposition, and cathodic arc deposition, or chemical vapor deposition, or sol-gels, or another suitable deposition method and apparatus.
The method further comprises step 46 (
In another one of the embodiments of the disclosure, there is provided a method for making a single layer infrared-reflecting film. Preferably, the film is transparent.
The method further comprises step 54 (
Depositing of the oxide matrix material and the higher valence cation may be carried out with a conventional deposition method and apparatus, such as discussed above. Such deposition methods and apparatuses that may be used may comprise physical vapor deposition such as sputter deposition (see
The method further comprises step 56 (
In another embodiment of the disclosure there is provided a single layer infrared-reflecting film with enhanced reflectivity in an 800 nanometer to 2500 nanometer infrared waveband. The film comprises a mixture of an oxide matrix material and a conductive metal dopant over a substrate. The oxide matrix material may comprise titanium dioxide, zinc oxide, tin oxide, or another suitable oxide matrix material that is transparent in the visible region. The conductive metal dopant preferably comprises gold, silver, copper, or another suitable conductive metal dopant that has limited solubility or is insoluble in the oxide matrix material. More preferably, the conductive metal dopant comprises gold. The gold may be in the form of discrete gold nanoparticles insoluble within the oxide matrix material, such as TiO2. The single layer infrared-reflecting film is produced as discussed above in relation to the method regarding the titanium dioxide matrix/gold embodiment.
In another embodiment of the disclosure there is provided a single layer infrared-reflecting film with enhanced reflectivity in an 800 nanometer to 2500 nanometer infrared waveband. The film comprises a mixture of an oxide matrix material and a higher valence cation over a substrate. The oxide matrix material may comprise titanium dioxide, zinc oxide, tin oxide, or another suitable oxide matrix material that is transparent in the visible region. The higher valence cation may comprise niobium, vanadium, tantalum, tungsten, chromium, or another suitable higher valence cation. The preferred higher valence cation is niobium. The substrate is as discussed above. The single layer infrared-reflecting film is produced as discussed above in relation to the method regarding the titanium dioxide matrix/niobium embodiment.
TiO2 film with gold (Au) was synthesized by magnetron sputtering onto a silicon substrate and glass cover slip. The substrate was ultrasonically cleaned in acetone for 15 minutes followed by cleaning in methanol for 15 minutes. The substrate was then placed in a vacuum chamber, with a base pressure of less than 5.0×10−8 Torr. The substrate was sputter-cleaned at a voltage of −150 Volts (V) in an argon atmosphere of 50 mTorr for 5 minutes. Then the deposition was carried out at 175 Watts (W) of power on a 2-inch diameter titanium target with inserted Au wires, pulsing at 250 kiloHertz (kHz). The substrate bias during deposition was −150 V, pulsing at 150 kHz. The sputtering atmosphere was 75% argon and 25% oxygen, with a total pressure of 5 mTorr. Final film thickness was around 300 nm (0.3 micron) to 500 nm (0.5 micron). Because of problems associated with oxygen flow control in some experiments, the TiO2 films were often substoichiometric. This problem was solved by annealing in air at 450° C. for 2 hours. This annealing step was not required for stoichiometric films. The resulting film was analyzed for composition, structure, and optical properties.
According to energy-dispersive x-ray spectrometry (EDS), gold doping varied from 0.7-1.3 at. % (atomic percent) in doped films when four gold wires were used. Gold doping varied from 1.8-2.0 at. % in doped films when six gold wires were used (see
TiO2 film with niobium (Nb) was synthesized by magnetron sputtering onto a silicon substrate and glass cover slip. The substrate was ultrasonically cleaned in acetone for 15 minutes followed by cleaning in methanol for 15 minutes. The substrate was then placed in a vacuum chamber, with a base pressure of less than 5.0×10−8 Torr. The substrate was sputter-cleaned at a voltage of −150 Volts (V) in an argon atmosphere of 50 mTorr for 5 minutes. Then the deposition was carried out at 175 Watts (W) of power on a 2-inch diameter titanium target with inserted Nb wires, pulsing at 250 kiloHertz (kHz). The substrate bias during deposition was −150V, pulsing at 150 kHz. The sputtering atmosphere was 75% argon and 25% oxygen, with a total pressure of 5 mTorr. Final film thickness was around 300 nm (0.3 micron) to 500 nm (0.5 micron). Because of problems associated with oxygen flow control in some experiments, the TiO2 films were often substoichiometric. This problem was solved by annealing in air at 450° C. for 2 hours. This annealing step was not required for stoichiometric films. The resulting film was analyzed for composition, structure, and optical properties.
EDS confirmed the presence of Nb. An AFM (atomic force microscope) 10 micron scan showed a smooth film and an RMS (root mean square) roughness of 2.6 nanometers (nm). A mixture of rutile/anatase TiO2 films doped with Nb was deposited. The extinction coefficient of films was near zero in visible and 800 nm to 2500 nm IR waveband. A 33% reflection of spectral radiation in the 800 nm to 2500 nm IR waveband was observed.
Many modifications and other embodiments of the disclosure will come to mind to one skilled in the art to which this disclosure pertains having the benefit of the teachings presented in the foregoing descriptions and the associated drawings. The embodiments described herein are meant to be illustrative and are not intended to be limiting. Although specific terms are employed herein, they are used in a generic and descriptive sense only and not for purposes of limitation.