CN210270237U - Silver-based thin film structure capable of efficiently reflecting ultraviolet, visible and infrared rays - Google Patents
Silver-based thin film structure capable of efficiently reflecting ultraviolet, visible and infrared rays Download PDFInfo
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- CN210270237U CN210270237U CN201921071037.8U CN201921071037U CN210270237U CN 210270237 U CN210270237 U CN 210270237U CN 201921071037 U CN201921071037 U CN 201921071037U CN 210270237 U CN210270237 U CN 210270237U
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Abstract
The patent discloses a silver-based film structure of high-efficient reflection of ultraviolet visible infrared. The silver-based thin film structure adopts a silver reflecting film and a long-wave-pass dielectric reflecting film to form a film system main body, the silver film efficiently reflects visible infrared wave bands in functional design, and the long-wave-pass dielectric reflecting film reflects ultraviolet wave bands and is used as a silver film protective layer. The coating method adopts the combination of the normal-temperature evaporation technology and the atomic layer deposition technology, the normal-temperature evaporation technology keeps the optical performance of the silver film, and the atomic layer deposition technology plates the pinhole-free compact film to effectively protect the silver film. The advantage of this patent is in having realized that the high-efficient reflection of ultraviolet visible infrared has improved the resistant environmental characteristic of silver-colored membrane, can effectively keep mirror surface shape and smooth finish, is applicable to the high-end optical instrument and the high-efficient transmission of multiband of the optical system of remote sensing load.
Description
Technical Field
This patent belongs to optical film's technical field, concretely relates to silver-based film structure of high-efficient reflection of ultraviolet visible infrared.
Background
In order to eliminate the chromatic aberration influence in the optical instrument, the optical instrument often adopts a reflective optical path structure, wherein the related optical elements need to be plated with a reflective film. In the coating of the multiband general-purpose reflector, a metal reflective film is the most common, wherein the most common metal is aluminum, silver or gold. It is known that a gold film can only efficiently reflect light in an infrared band, and an aluminum film can reflect light in ultraviolet to infrared bands, but the average reflectivity is only about 0.9, which is not preferable in an optical system seeking extreme energy efficiency, thus greatly limiting the application of the gold film in high-end optical instruments. The silver film is selected as the coating film of the reflector, has a reflectivity of more than 0.97 in the visible to infrared band, and is an ideal metal reflector coating film selection in the visible and infrared band.
The reflectivity of the bare silver film without the protective film in the near ultraviolet 350-400 nm wave band is more than 0.9. However, in practical applications, the silver film reflector needs to be plated with a dielectric protection film to prevent the silver film from physical and chemical damages such as scratches, corrosion, oxidation and vulcanization, and the interface between the silver film and the dielectric protection film has strong surface plasma absorption in the wavelength band of 350-400 nm, which results in that the actually applied silver film reflector has a reflectivity of less than 0.8 in the wavelength band region, and the reflectivity of the silver film itself in the wavelength band of less than 350nm is extremely low, so that the conventional silver reflector can hardly be used as a reflector in ultraviolet. The coating of the reflective element for the ultraviolet band can only be generally an aluminum reflective film, which leads to low energy efficiency of the optical system in the visible near infrared.
With the intensive pursuit of advanced optical instruments for ultraviolet, visible and infrared full-band detection and improvement of optical energy efficiency, aluminum reflectors have gradually failed to meet the requirements for development of advanced optical instruments, and the search for new reflector film system structures and film coating methods to meet the requirements for efficient transmission of optical full-band energy of optical instruments has become one of the development directions of reflector film coating in the future.
Disclosure of Invention
The purpose of this patent is to overcome the not enough of can not realizing the high-efficient reflection of ultraviolet visible infrared full wave band in current metal reflector membrane system structure and the coating film technique, provides a silver-based thin film structure of high-efficient reflection of ultraviolet visible infrared.
The technical scheme that this patent provided is:
the film system main body is formed by a silver reflecting film and a long-wave-pass dielectric reflecting film, and in terms of functional design, the silver film efficiently reflects visible infrared bands, and the long-wave-pass dielectric reflecting film reflects ultraviolet bands and serves as a silver film protective layer;
the membrane system structure is designed as follows: a first bonding layer 2, a silver film 3, a second bonding layer 4, a first matching layer film stack 5, a dielectric reflecting film stack 6 and a second matching layer film stack 7 are sequentially plated on the reflector body 1;
the reflector body 1 is a glass, fused quartz, aluminum, titanium, surface modified silicon carbide or beryllium mirror;
the bonding layer I2 is Al2O3The single film layer or the multilayer composite film of Ni, Cr, NiCr alloy and NiCrN alloy, the thickness of the film layer is 10-50 nm;
the thickness of the silver film 3 is 100-300 nm;
the second bonding layer 4 is Al2O3The thickness is 5-30 nm;
the matching layer film stack I5 is a low-refractive-index film SiO2And a high refractive index film HfO2Preferably a 2-layer structure LH or a 4-layer structure LHLH, L being SiO2H is HfO2；
The dielectric reflecting film stack 6 is a low refractive index film SiO2And a high refractive index film HfO2The dielectric reflective film stack with the wave band of 200-400 nm is formed, and the film structure is a (LH)x、a(LH)xb(LH)yOr a (LH)xb(LH)yc(LH)zWherein a, b and c represent the central wavelength coefficient values of the reflecting film stack, and satisfy a>b>c, x, y and z represent the number of lamination cycles, and the number of lamination cycles is preferably 2-5, 6-8 and 6-8 respectively;
the second matching layer film stack 7 is a low-refractive-index film SiO2And a high refractive index film HfO2The stack of layers is preferably a single-layer structure L or a three-layer structure LHL.
The coating film technical scheme that this patent adopted does:
two vacuum coating technologies are adopted and used together, namely a normal-temperature evaporation technology and an atomic layer deposition technology, and are respectively carried out according to different stages of film system deposition;
the coating mode of the first bonding layer 2, the silver film 3 and the second bonding layer 4 adopts a normal-temperature evaporation mode, and the first matching layer film stack 5, the medium reflecting film stack 6 and the second matching layer film stack 7 adopt an atomic layer deposition technology to coat a pinhole-free compact film;
the specific steps of coating are as follows:
1) cleaning the lens body with acetone, ethanol and deionized water in sequence, air drying, partially wiping, placing in a vacuum chamber, maintaining the temperature of the lens body at normal temperature, and vacuumizing to 5 × 10-3Pa below;
2) a Hall ion source is adopted to carry out argon ion bombardment on the mirror surface, the anode voltage is 120-300V, the anode current is 2-10A, and the bombardment lasts for 5-20 minutes;
3) evaporating and plating a first adhesive layer 2 on the mirror surface, preferably with the thickness of 20nm and the speed of 0.2-0.6 nm/s;
4) evaporating a silver film 3 on the mirror surface, wherein the thickness is preferably 180nm, and the speed is 2-3 nm/s;
5) evaporating a second bonding layer 4 on the mirror surface, wherein the thickness is preferably 5nm, and the speed is 0.3-0.5 nm/s;
6) deflating the vacuum chamber, sampling, transferring to an atomic layer deposition reaction chamber, and heating for 3 hours to the preferred temperature of 170 ℃;
7) using TMA and H2Growing Al with the thickness of 5nm on a mirror body by an atomic layer deposition mode of O thermal reaction2O3；
8) According to theoretical design, the film system grows SiO on the mirror body by adopting the atomic layer deposition technology2And HfO2The film system structure of (1);
9) and after the film coating is finished, stopping heating, and sampling after naturally cooling to room temperature.
Compared with the prior art, this patent has following advantage:
1. the high reflection of visible light to infrared is guaranteed on the basis of the silver-based reflector, and meanwhile, the silver film protective layer adopts a long-wave-pass dielectric reflector stack to improve the reflectivity of an ultraviolet band, reduce the absorption of a silver film and the absorption of surface plasma, and realize the high reflectivity of the silver-based film in ultraviolet, visible light and infrared;
2. the silver film protective layer is a lamination of dozens of films with high and low refractive indexes, and is a hard corrosion-resistant film layer, the total thickness is 400-1500 nm, and the silver film protective layer can effectively prevent mechanical scratches and physical and chemical erosion of water vapor, oxygen, sulfide, halide and the like;
3. the atomic layer deposition technology that the silver membrane protective layer of this patent adopted carries out the coating film, can form the tight rete of no pinhole, seals the nanometer hole, when effectively protecting silver reflection film layer, utilizes atomic layer deposition technology conformality and homogeneity characteristics to realize the maintenance of mirror surface shape and smooth finish.
Drawings
FIG. 1 is a schematic diagram of the membrane system of this patent.
FIG. 2 is a comparison of the reflectance spectra curves of the silver-based thin films of examples one and three of this patent with those of a typical silver reflective film at an incident angle of 8 °.
FIG. 3 is a comparison of the reflectance spectra of the silver-based thin film of example two of this patent with those of a typical silver reflective film at an incident angle of 45 °.
Detailed Description
The patent is further described with reference to the following specific examples
Example one
In the embodiment, the primary and secondary mirror reflection films of the Cassegrain telescope system applied to space remote sensing loads are plated, and the reflection spectrum indexes are that the reflectivity of 300-1200 nm is more than 96%, the reflectivity of 250-300 nm is more than 90%, and the reflectivity of 200-250 nm is more than 70%. The selected basic film system structure is shown in fig. 1, wherein the fine structure of each functional film layer is described as follows:
the mirror body is made of fused quartz material, the first bonding layer 2 is NiCr alloy, and the second bonding layer 4 is Al2O3The first matching layer film stack 5, the dielectric reflecting film stack 6 and the second matching layer film stack 7 are low-refractive-index films SiO2And a high refractive index film HfO2A laminate of the above; the specific film system structure is as follows:
20Np180Ap10Mp0.457L 1.056H 0.755L 1.328H(0.92L 0.97H)3(0.813L0.705H)6(0.666L 0.453H)61.746L；
wherein, the subscript P represents the film layer number with the former number as the geometric thickness in nm, N is NiCr alloy, A is Ag, M is Al2O3H is HfO2L is SiO2H and L are front numbers representing weight coefficients of optical thicknesses, each of which has a λ/4 with reference to a center wavelength of 370 nm. The material parameters of each film layer are obtained through actual measurement, and the specific method comprises the following steps: growing a single-layer film on a silicon wafer and fused quartz by adopting a corresponding film growth process, then calibrating the growth rate and the material refractive index by adopting an elliptical polarization measurement method and a spectral measurement method, and carrying out design optimization and film deposition control system by introducing calibrated material parameters into film software.
FIG. 2 shows a silver-based thin film and a typical silver reflective film (30 nm Al is plated on the silver film in sequence)2O3And 150nmSiO2Protective film(s) of the optical film (taking into account the measured surface plasmon absorption). As can be seen from the figure, compared with a typical silver reflecting film, the reflectivity of the silver-based film structure in the ultraviolet band of 200-400 nm is obviously improved, the reflectivity loss of the visible infrared band is extremely low, and the efficient reflection of ultraviolet visible infrared light is realized.
The coating method comprises the following specific steps:
1) sequentially placing the fused quartz lens body into acetone, ethanol and deionized water for ultrasonic cleaning for 15 minutes, drying, dipping the surface with absorbent cotton cloth in alcohol ether mixed solution according to the surface condition to locally wipe the surface, placing the cleaned surface into a coating vacuum chamber, keeping the temperature of the lens body at normal temperature, and vacuumizing to 5 x 10-3Pa below;
2) a Hall ion source is adopted to carry out argon ion bombardment on the mirror surface, the anode voltage is 150V, the anode current is 4A, and the bombardment lasts for 10 minutes;
3) heating a pre-melted nickel-chromium wire mass by adopting a tungsten wire, opening a baffle plate when the nickel-chromium wire mass is melted into a liquid bead shape, increasing the heating power, evaporating a nickel-chromium film on a mirror surface, depositing at a deposition rate of 0.4nm/s and a thickness of 20nm, and closing the baffle plate;
4) a molybdenum boat is adopted to contain silver particles, current is applied to heat the silver particles to melt the silver particles into a mass of liquid, a baffle is opened, heating power is increased to evaporate the liquid silver, a silver film is deposited on a mirror surface, the deposition rate is 2-3 nm/s, the growth thickness is 180nm, and the baffle is closed;
5) heating Al by electron beam evaporation2O3Target material, 5nm Al is evaporated on the mirror surface2O3The growth rate of the film is 0.3-0.5 nm/s, so that the silver reflecting film is not oxidized after being exposed in the atmospheric environment in a short time;
6) standing for half an hour, deflating the vacuum chamber, sampling, transferring the mirror body to an atomic layer deposition reaction chamber, vacuumizing to below 0.4mbar, and heating the reaction chamber for 3 hours to the optimal temperature of 170 ℃;
7) using TMA and H2Growing Al with the thickness of 5nm on the mirror surface by an atomic layer deposition mode of O thermal reaction2O3To realize compact and uniform coverage of the silver film to ensure SiO2And HfO2The atomic layer deposition process can not generate chemical damage to the silver film;
8) according to theoretical design, a film system grows SiO on a mirror surface by adopting an atomic layer deposition technology2And HfO2The film system structure of (1);
9) and after the film coating is finished, stopping heating, and sampling after naturally cooling to room temperature.
Example two
In the embodiment, a pointing mirror or a scanning mirror commonly used for space-to-ground remote sensing loads is selected as an example, the mirror body of the type usually works at an incident angle of 45 degrees, has large size and heavy weight, needs to be lightened, and needs to consider surface shape precision at the same time, so that the stress of a film layer needs to be controlled in the process of plating a reflecting film so as to reduce the surface shape change of the coated mirror surface. Meanwhile, the wavelength of 300-400 nm is an ultraviolet band which is commonly set for remote sensing to the ground, and the method has unique advantages in remote sensing of oil spill on the sea surface. In addition, the atmosphere is opaque to ultraviolet bands of 200-300 nm, so that the reflector containing the ultraviolet bands and used for remote ground sensing loads only needs to have high reflectivity at the bands larger than 300 nm. Under the condition of not reducing the visible infrared reflectivity, the silver-based film structure has good reflection efficiency. The selected basic film system structure is still as shown in fig. 1, wherein the fine structure of each functional film layer is as follows:
the mirror body is made of surface modified SiC material, the first bonding layer 2 is NiCr alloy, and the second bonding layer 4 is Al2O3The first matching layer film stack 5, the dielectric reflecting film stack 6 and the second matching layer film stack 7 are low-refractive-index films SiO2And a high refractive index film HfO2A laminate of the above; the specific film system structure is as follows:
20Np100Ap10Mp0.408L 0.947H 1.048L 0.97H(0.993L 0.834H)31.699L；
wherein, the subscript P represents the film layer number with the former number as the geometric thickness in nm, N is NiCr alloy, A is Ag, M is Al2O3H is HfO2L is SiO2H and L are front numbers representing weight coefficients of optical thicknesses, each of which has a λ/4 with reference to a center wavelength of 370 nm.
Compared with the first example, the thickness of the silver film 3 is reduced, the dielectric reflective film stack 6 is simplified, the change of the mirror surface shape caused by film stress is reduced, and meanwhile, the high reflectivity of the wavelength larger than 300nm is met. Fig. 3 is a comparison of the theoretically designed reflectance spectra of the silver-based thin film of example two and a typical silver reflective film. As can be seen from figure 3, the reflectivity of the silver-based thin film structure provided by the patent at the ultraviolet band of 300-400 nm is obviously improved, and the reflectivity of the silver-based thin film structure at the visible infrared band is hardly lost.
EXAMPLE III
In this embodiment, a mirror of a spectrometer is selected as an example, and this type of mirror has low requirements on imaging quality and is therefore insensitive to surface deformation. In addition, the film is used on the ground, and the stress influence of the film can be reduced by thickening the substrate even if the surface shape control is required. Meanwhile, the reflecting mirror of the type also needs to seek high reflection efficiency from ultraviolet to near infrared so as to improve the signal sensitivity of the instrument.
The surface processing of the reflector for the ground is not as strict as the requirement of aerospace products, and relatively more point defects exist on the surface of the reflector. In order to avoid the moisture adsorption and other corrosive gas adsorption of the point defects exposed in the atmosphere, and further influence the reliability and the service life of the silver reflector, the adhesive layer I2 and the silver film 3 are considered to be thickened so as to ensure the complete coverage of the point defects. The film structure is based on the reflective film structure in the first example, and the designed reflection spectrum is still as shown in fig. 2 without change. The thicknesses of the adhesive layer one 2 and the silver film 3 in the film system structure become 50nm and 300 nm. The specific film system structure is as follows:
50Np300Ap10Mp0.457L 1.056H 0.755L 1.328H(0.92L 0.97H)3(0.813L0.705H)6(0.666L 0.453H)61.746L；
wherein, the subscript P represents the film layer number with the former number as the geometric thickness in nm, N is NiCr alloy, A is Ag, M is Al2O3H is HfO2L is SiO2H and L are front numbers representing weight coefficients of optical thicknesses, each of which has a λ/4 with reference to a center wavelength of 370 nm.
Claims (1)
1. A silver-based film structure capable of efficiently reflecting ultraviolet, visible and infrared rays is characterized in that:
the structure of the film system of the silver-based film structure is as follows: sequentially plating a first bonding layer (2), a silver film (3), a second bonding layer (4), a first matching layer film stack (5), a dielectric reflecting film stack (6) and a second matching layer film stack (7) on the reflector body (1);
the reflector body (1) is a glass, fused quartz, aluminum, titanium, surface modified silicon carbide or beryllium mirror;
the first bonding layer (2) is Al2O3A single film layer or a multilayer composite film of Ni, Cr, NiCr alloy or NiCrN alloy, wherein the thickness of the film layer is 10-50 nm;
the thickness of the silver film (3) is 100-300 nm;
the second bonding layer (4) is Al2O3A layer having a thickness of 5 to 30 nm;
the matching layer film stack I (5) is a low-refractive-index film SiO2And a high refractive index film HfO2Adopts 2-layer structure LH or 4-layer structure LHLH, L is SiO2H is HfO2；
The dielectric reflecting film stack (6) is a low refractive index film SiO2And a high refractive index film HfO2The dielectric reflective film stack with the wave band of 200-400 nm is formed, and the film structure is a (LH)x、a(LH)xb(LH)yOr a (LH)xb(LH)yc(LH)zWherein a, b and c represent the central wavelength coefficient values of the reflecting film stack, and satisfy a>b>c, x, y and z represent the number of lamination cycles which are respectively 2-5, 6-8 and 6-8;
the second matching layer film stack (7) is a low-refractive-index film SiO2And a high refractive index film HfO2The formed lamination adopts a single-layer structure L or a three-layer structure LHL.
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Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN111560602A (en) * | 2020-04-13 | 2020-08-21 | 哈尔滨工业大学 | Optimization method for surface recombination of oxide film |
| JP2022179405A (en) * | 2021-05-21 | 2022-12-02 | ハンド ヘルド プロダクツ インコーポレーティッド | Methods, apparatuses and systems for providing optical coatings for optical components |
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2019
- 2019-07-10 CN CN201921071037.8U patent/CN210270237U/en not_active Withdrawn - After Issue
Cited By (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN111560602A (en) * | 2020-04-13 | 2020-08-21 | 哈尔滨工业大学 | Optimization method for surface recombination of oxide film |
| CN111560602B (en) * | 2020-04-13 | 2021-10-26 | 哈尔滨工业大学 | Optimization method for surface recombination of oxide film |
| JP2022179405A (en) * | 2021-05-21 | 2022-12-02 | ハンド ヘルド プロダクツ インコーポレーティッド | Methods, apparatuses and systems for providing optical coatings for optical components |
| JP7498221B2 (en) | 2021-05-21 | 2024-06-11 | ハンド ヘルド プロダクツ インコーポレーティッド | Method, apparatus and system for providing optical coatings for optical components |
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