Process for producing a short-wave low-reflection film system on a germanium substrate

Abstract

A preparation method of a germanium substrate 2-2.3 mu m short wave low reflection film system comprises the following steps: S1, cleaning of the germanium substrate as a lens and an accompanying plating piece, the accompanying plating piece being a round piece and a wedge-shaped piece; S2, loading the lens into a tool clamp, and hanging the tool clamp into a cavity; S3, vacuumizing and cleaning a Hall ion source; S4, sequentially coating each film layer on a first surface of the lens according to 34.8 nm SiO / 64.3 nm Ge / 52.2 nm ZnS / 272.8 nm SiO, electron beam heating evaporation of SiO film layers and Ge film layers, resistance heating evaporation of ZnS film layers, a deposition rate of the SiO film layer being 0.6 nm / s, a deposition rate of the Ge film layer being 0.3 nm / s, a deposition rate of the ZnS film layer being 0.8 nm / s, and ion source assisted deposition; S5, cooling the cavity, and taking out the tool clamp together with the lens; and S6, repeating steps S1 to S5 to coat the same film system on a second surface of the lens, wherein the wedge-shaped piece is not cleaned when repeating step S1, and is not put into the tool clamp when repeating step S2.

Description

TECHNICAL FIELD

[0001] The present disclosure relates to the field of infrared coating, and more particularly to a preparation method of a germanium substrate 2-2.3 μm short wave low reflection film system. BACKGROUND

[0002] In the field of infrared optical coating, germanium has good infrared transmittance and refractive index, and is therefore commonly used to manufacture infrared optical lenses, infrared cameras, infrared telescopes, and infrared sensors and other equipment, and is widely used in infrared imaging systems. However, developing a film system capable of low reflection of 2-2.3 μm short wave is crucial to improving the performance of products using germanium substrates. In addition, improving the various environmental adaptability of products using germanium substrates is also an important development direction. SUMMARY

[0003] In view of the problems in the background art, an object of the present disclosure is to provide a preparation method of a germanium substrate 2-2.3 μm short wave low reflection film system, which can be used to improve the surface reflectivity of 2-2.3 μm short wave of the germanium substrate prepared together with the film system on both sides.

[0004] Another object of the present disclosure is to provide a preparation method of a germanium substrate 2-2.3 μm short wave low reflection film system, which can pass eight tests including water bubble test, salt spray test, adhesion test, cold and hot impact test, constant temperature and humidity test, abrasion resistance test, low temperature test and high temperature test, and thus can improve the various environmental adaptability of products after coating films on both sides of the germanium substrate.

[0005] Thus, the preparation method of a germanium substrate 2-2.3 μm short wave low reflection film system includes the steps of: S1, cleaning the surface of a germanium substrate as a lens and a companion plate, wherein the companion plate is a round plate with equal thickness and a wedge-shaped plate with a first polished plane and a second rough surface; S2, loading the treated lens into a tool clamp, and hanging the tool clamp loaded with the lens into the cavity of a vacuum coating machine, and setting the temperature of the cavity to 150℃; S3, starting vacuum pumping of the vacuum coating machine, and when the vacuum degree reaches 1.0×10 -3Pa, turn on the Hall ion source of the vacuum coating machine for cleaning. The cleaning time is 6 minutes. The parameters of the Hall ion source are: anode voltage 220V, anode current 1.2A, neutralization current 1.5A, neutralization gas flow rate 10sccm, and argon flow rate percentage 100%; S4, on the first surface of the lens, apply a four-layer film system consisting of SiO, Ge, and ZnS: 34.8nm SiO / 64.3nm Ge / 52.2nm ZnS. S1: 272.8nm SiO, sequentially depositing each film layer. The nm numbers preceding SiO, Ge, and ZnS indicate the corresponding film thickness. SiO and Ge films are evaporated using electron beam heating, while ZnS films are evaporated using resistance heating. The deposition rate for SiO is 0.6nm / s, for Ge is 0.3nm / s, and for ZnS is 0.8nm / s. Ion source-assisted deposition is used for each film layer, and deposition is completed at a chamber temperature of 150°C. S5: After depositing the film system on the first surface of the lens, the chamber is allowed to cool naturally to below 60°C. The fixture and lens are then removed. S6: Repeat steps S1 to S5 to deposit the same film system on the second surface of the lens. The wedge is not cleaned during step S1 and is not placed in the fixture during step S2.

[0006] The beneficial effects of this disclosure are as follows: In the preparation method of the 2-2.3μm short-wave low-reflection film system on a germanium substrate according to this disclosure, the same Sub (germanium substrate) / SiO / Ge / ZnS / SiO / Air film system is deposited on both sides of the germanium substrate through steps S1 to S6. Among the three film materials SiO, Ge, and ZnS, SiO has two film layers, and Ge and ZnS each have one film layer. The two SiO film layers are respectively used as the bottom and the outer surface, and the Ge film layer and ZnS film layer are located between the two SiO film layers. The prepared germanium substrate and the film system on both sides can be used to improve the surface reflectivity of 2-2.3μm short waves. As verified by the testing process, the prepared germanium substrate and the film system on both sides can pass eight tests, including water immersion test, salt spray test, adhesion test, thermal shock test, constant temperature and humidity test, abrasion resistance test, low temperature test, and high temperature test, thereby improving the environmental adaptability of the product after coating on both sides of the germanium substrate. Attached Figure Description

[0007] Figure 1 This is a schematic structural diagram of a germanium substrate and the film system on both sides, prepared according to the method for preparing a 2-2.3 μm short-wavelength low-reflection film system on a germanium substrate disclosed herein.

[0008] Figure 2 It is a photograph of the wedge-shaped piece in the plating sheet.

[0009] Figure 3It is a graph showing the reflectance of the wedge-shaped sheet and the corresponding film system on the first surface in the substrate of Example 1. Detailed Implementation

[0010] The accompanying drawings illustrate embodiments of this disclosure, and it will be understood that the disclosed embodiments are merely examples of this disclosure, which can be implemented in various forms. Therefore, the specific details disclosed herein should not be construed as limiting, but are intended only as the basis for the claims and as an illustrative basis to teach those skilled in the art how to implement this disclosure in various ways.

[0011] [Preparation method of 2-2.3μm short-wavelength low-reflection film system on germanium substrate]

[0012] Reference Figure 1 The method for preparing a 2-2.3 μm short-wavelength low-reflection film system on a germanium substrate according to this disclosure includes the following steps:

[0013] S1, the surfaces of the germanium substrate used as the lens and the product are cleaned. The substrate is a circular sheet of uniform thickness and a wedge-shaped sheet with a polished first surface and a rough, textured second surface (e.g., ...). Figure 2 (as shown);

[0014] S2, load the processed lens into the tooling fixture, and hang the tooling fixture with the lens loaded into the vacuum coating machine cavity. The temperature of the cavity is set to 150℃.

[0015] S3, the vacuum coating machine starts vacuuming, and the vacuum level reaches 1.0×10⁻⁶. -3 Pa, turn on the Hall ion source of the vacuum coating machine for cleaning. The cleaning time is 6 minutes. The parameters of the Hall ion source are: anode voltage of 220V, anode current of 1.2A, neutralization current of 1.5A, neutralization gas flow rate of 10sccm, and argon flow rate of 100%.

[0016] S4, on the first surface of the lens, consists of a four-layer film system composed of three materials: SiO, Ge, and ZnS.

[0017] 34.8nm SiO / 64.3nm Ge / 52.2nm ZnS / 272.8nm SiO, each film layer was deposited sequentially.

[0018] The numbers preceding SiO, Ge, and ZnS with "nm" indicate the film thickness of the corresponding layer. The SiO and Ge layers were evaporated using electron beam heating, while the ZnS layer was evaporated using resistance heating. The deposition rate of the SiO layer was 0.6 nm / s, the Ge layer was 0.3 nm / s, and the ZnS layer was 0.8 nm / s. All layers were deposited using ion source-assisted deposition, and the deposition of each layer was completed at a cavity temperature of 150°C.

[0019] S5. After the coating system is applied to the first surface of the lens, the cavity is naturally cooled to below 60°C, and the tooling fixture is removed along with the lens.

[0020] S6, repeat steps S1 to S5 to deposit the same film system on the second surface of the lens, wherein the wedge is not cleaned when repeating step S1 and is not placed in the tooling fixture when repeating step S2.

[0021] In the method for preparing a 2-2.3 μm short-wavelength low-reflectance film system on a germanium substrate according to this disclosure, the same Sub (germanium substrate) / SiO / Ge / ZnS / SiO / Air film system is deposited on both sides of the germanium substrate through steps S1 to S6. Among the three film materials SiO, Ge, and ZnS, SiO has two layers, Ge and ZnS each have one layer. The two SiO layers are used as the underside and the outer surface, respectively, and the Ge and ZnS layers are located between the two SiO layers. The prepared germanium substrate, along with the film system on both sides, can be used to improve the surface reflectivity of 2-2.3 μm short waves. As verified by the testing process, the prepared germanium substrate, along with the film system on both sides, can pass eight tests, including water immersion test, salt spray test, adhesion test, thermal shock test, constant temperature and humidity test, abrasion resistance test, low temperature test, and high temperature test, thereby improving the environmental adaptability of the product after coating on both sides of the germanium substrate.

[0022] The cleaning in step S1 helps improve the surface condition of each surface of the lens, and helps improve the adhesion between the coating system on each surface and the corresponding surface of the lens. In step S1, for example, ultrasonic cleaning or manual cleaning is used to clean the surface of the lens. Specifically, in step S1, ultrasonic cleaning of the lens surface involves polishing with an alumina polishing slurry followed by ultrasonic rinsing with pure water. For example, in step S1, the alumina polishing slurry used is a 0.1μm polycrystalline diamond slurry from Nanjing Hengrui Precision Optics Co., Ltd. In step S1, for example, the product is a lens or a flat plate. In step S1, for example, the thickness of the disc in the coating is 2mm.

[0023] The temperature setting of the vacuum coating machine in step S2 heats the lens through the cavity of the coating machine, which helps the film to grow from the lens and reduces the stress of film growth.

[0024] Step S3 uses a Hall ion source for cleaning, which removes impurities and oil molecules adsorbed on the surface of each side of the lens from the substrate surface, thereby significantly improving the interface state and helping to improve the bonding performance between the film and the corresponding surface of the lens. At the same time, cleaning with a Hall ion source can heat the corresponding surface of the lens, which helps the film grow from the lens and reduces the film growth stress.

[0025] In step S4, in one example, a Hall ion source is used. When depositing the SiO film, the ion source parameters are: neutralization current of 0.5A, neutralization gas flow rate of 8 sccm, anode voltage of 120V, anode current of 1.2A, argon flow rate ratio of 30%, and oxygen flow rate ratio of 70%. When depositing the Ge film, the ion source parameters are: neutralization current of 0.5A, neutralization gas flow rate of 8 sccm, anode voltage of 120V, anode current of 1.0A, and argon flow rate ratio of 100%. When depositing the ZnS film, the ion source parameters are: neutralization current of 0.5A, neutralization gas flow rate of 8 sccm, anode voltage of 120V, anode current of 1.2A, and argon flow rate ratio of 100%.

[0026] In step S4, in one example, argon gas is introduced and a vacuum is drawn during the deposition of each film layer to maintain a flow-through constant vacuum. The flow-through constant vacuum setting is not lower than 5.0 × 10⁻⁶. -3 Pa.

[0027] In step S4, for example, the crystal oscillator method is used to monitor the film thickness using the corresponding crystal oscillators of multiple crystal oscillators of the crystal controller. After ion source cleaning, the crystal controller controls the new crystal oscillator among the multiple crystal oscillators to work accordingly, and the crystal oscillator frequency is not less than 5.99MHz.

[0028] After step S6 is completed, in one example, the wedge-shaped sheet in the co-coated sheet, together with the film system corresponding to the first surface, has an average reflectivity of less than 0.8% in the 2-2.3 μm band.

[0029] After step S6 is completed, in one example, the disc in the substrate, together with the film system on both sides, passes the water immersion test, salt spray test, adhesion test, thermal shock test, constant temperature and humidity test, abrasion resistance test, low temperature test, and high temperature test.

[0030] [test]

[0031] Example 1

[0032] The preparation method of the germanium substrate 2-2.3μm short-wavelength low-reflection film system in Example 1 adopts the following steps:

[0033] S1, the surfaces of the germanium substrate used as the lens and the product are cleaned. The substrate consists of a circular piece of uniform thickness and a wedge-shaped piece with a polished surface on the first side and a rough surface on the second side. The surface of the lens is cleaned using ultrasonic waves. The ultrasonic surface cleaning process involves polishing with an alumina polishing slurry followed by ultrasonic cleaning with pure water. The alumina polishing slurry used is a 0.1μm polycrystalline diamond slurry from Nanjing Hengrui Precision Optics Co., Ltd. The thickness of the circular piece in the substrate is 2mm. The product is a lens.

[0034] S2, load the processed lens into the tooling fixture, and hang the tooling fixture with the lens loaded into the vacuum coating machine cavity. The temperature of the cavity is set to 150℃.

[0035] S3, the vacuum coating machine starts vacuuming, and the vacuum level reaches 1.0×10⁻⁶. -3 Pa, turn on the Hall ion source of the vacuum coating machine for cleaning. The cleaning time is 6 minutes. The parameters of the Hall ion source are: anode voltage of 220V, anode current of 1.2A, neutralization current of 1.5A, neutralization gas flow rate of 10sccm, and argon flow rate of 100%.

[0036] S4, on the first surface of the lens, consists of a four-layer film system composed of three materials: SiO, Ge, and ZnS.

[0037] 34.8nm SiO / 64.3nm Ge / 52.2nm ZnS / 272.8nm SiO, each film layer was deposited sequentially.

[0038] In this diagram, the numbers preceding SiO, Ge, and ZnS indicate the film thickness. SiO and Ge films were evaporated using electron beam heating, while ZnS films were evaporated using resistance heating. The deposition rate for SiO was 0.6 nm / s, for Ge was 0.3 nm / s, and for ZnS was 0.8 nm / s. All films were deposited using ion source-assisted deposition at a chamber temperature of 150°C.

[0039] In step S4,

[0040] The ion source used is a Hall ion source.

[0041] When depositing the SiO film, the ion source parameters are: neutralization current of 0.5A, neutralization gas flow rate of 8sccm, anode voltage of 120V, anode current of 1.2A, argon flow rate of 30%, and oxygen flow rate of 70%.

[0042] When depositing the Ge film, the ion source parameters are: neutralization current of 0.5A, neutralization gas flow rate of 8sccm, anode voltage of 120V, anode current of 1.0A, and argon gas flow rate of 100%.

[0043] When depositing the ZnS film, the ion source parameters are: neutralization current of 0.5A, neutralization gas flow rate of 8sccm, anode voltage of 120V, anode current of 1.2A, and argon gas flow rate of 100%.

[0044] In step S4,

[0045] Argon gas was introduced and a vacuum was drawn during the deposition of each film layer to maintain a constant flow vacuum. The constant flow vacuum was set to 5.0 × 10⁻⁶. -3 Pa;

[0046] The crystal oscillator method is used to monitor the film thickness by using the corresponding crystal oscillators of multiple crystal oscillators in the crystal controller. After cleaning with the ion source, the crystal controller controls the new crystal oscillator in the multiple crystal oscillators to work accordingly. The crystal oscillator frequency is not less than 5.99MHz.

[0047] S5. After the coating system is applied to the first surface of the lens, the cavity is naturally cooled to 60°C, and the tooling fixture is taken out along with the lens.

[0048] S6, repeat steps S1 to S5 to deposit the same film system on the second surface of the lens, wherein the wedge is not cleaned when repeating step S1 and is not placed in the tooling fixture when repeating step S2.

[0049] The wedge-shaped plate in the surcharge plate of Example 1 is used to test reflectivity. Figure 3 This is a graph showing the reflectance of the wedge-shaped sheet and the corresponding film system on the first surface in the substrate of Example 1. From... Figure 3 It can be seen that the wedge-shaped sheet in the substrate, together with the film system corresponding to the first surface, has an average reflectivity of less than 0.8% in the 2-2.3μm band.

[0050] The following tests were performed on the discs in Example 1 after coating both sides.

[0051] Water immersion test: Take tap water and conduct a water immersion test for 2 hours. Observe whether the film layer on each surface of the disc in the immersion sheet falls off from the disc in the immersion sheet, and observe whether the film layer on each surface of the disc in the immersion sheet cracks.

[0052] Salt spray test: Neutral salt spray test for 48 hours, observe whether the film layer on each surface of the disc in the surcharged sheet peels off, and observe whether the film layer on each surface of the disc in the surcharged sheet cracks.

[0053] Adhesion test: Apply 3M tape to each side of the disc in the coating sheet by hand, and pull the tape in the opposite direction to the adhesive end to observe whether the film layer is pulled up.

[0054] Thermal shock test: The film is subjected to thermal shock in the range of -40℃ to 85℃ for 24 hours in a high and low temperature chamber. Observe whether the film layer on each surface of the disc in the substrate peels off and whether the film layer on each surface of the disc in the substrate cracks.

[0055] Constant temperature and humidity test: In a constant temperature and humidity chamber, at 50℃ and 95% relative humidity for 48 hours, observe whether the film layer on each surface of the disc in the substrate peels off and whether the film layer on each surface of the disc in the substrate cracks.

[0056] Friction resistance test (medium friction test): Wrap the rubber friction head of the rubber with degreased cloth and apply a pressure of 4.9N to the film surface of the coated sheet for 50 cycles (25 back and forth). Observe whether there are scratches or signs of damage on the film surface.

[0057] Low temperature test: In a low temperature chamber, at -40℃ for 48 hours, observe whether the film layer on each surface of the disc in the substrate peels off and whether the film layer on each surface of the disc in the substrate cracks.

[0058] High temperature test: In a high temperature chamber, at 85℃ for 48 hours, observe whether the film layer on each surface of the disc in the substrate has peeled off and whether the film layer on each surface of the disc in the substrate has cracked.

[0059] In the water immersion test, salt spray test, thermal shock test, constant temperature and humidity test, low temperature test, and high temperature test, the film layer did not peel off or crack; in the adhesion test, the film layer was not pulled up; in the abrasion resistance test, there were no signs of scratch damage on the film layer surface, i.e., it can withstand moderate abrasion. In other words, the disc in the surcharge sheet of Example 1, together with the film system on both sides, passed a total of eight tests, including the water immersion test, salt spray test, adhesion test, thermal shock test, constant temperature and humidity test, abrasion resistance test, low temperature test, and high temperature test.

[0060] Several exemplary embodiments have been described in detail above, but this document is not intended to limit itself to the explicitly disclosed combinations. Therefore, unless otherwise stated, the various features disclosed herein can be combined to form several other combinations, which are not shown for simplicity.

Claims

1. A method for preparing a 2-2.3 μm short-wavelength low-reflection film system on a germanium substrate, characterized in that, Including the following steps: S1, the surface of the germanium substrate used as the lens and the product are cleaned. The substrate is a circular piece of equal thickness and a wedge-shaped piece with a polished flat surface on the first side and a rough surface on the second side. S2, load the processed lens into the tooling fixture, and hang the tooling fixture with the lens loaded into the vacuum coating machine cavity. The temperature of the cavity is set to 150℃. S3, the vacuum coating machine starts vacuuming, and the vacuum level reaches 1.0×10⁻⁶. -3 Pa, turn on the Hall ion source of the vacuum coating machine for cleaning. The cleaning time is 6 minutes. The parameters of the Hall ion source are: anode voltage of 220V, anode current of 1.2A, neutralization current of 1.5A, neutralization gas flow rate of 10sccm, and argon flow rate of 100%. S4, on the first surface of the lens, a four-layer film system consisting of SiO, Ge, and ZnS is sequentially deposited: 34.8nm SiO / 64.3nm Ge / 52.2nm ZnS / 272.8nm SiO. The numbers preceding SiO, Ge, and ZnS with "nm" indicate the film thickness of the corresponding layer. The SiO and Ge layers were evaporated using electron beam heating, while the ZnS layer was evaporated using resistance heating. The deposition rate of the SiO layer was 0.6 nm / s, the Ge layer was 0.3 nm / s, and the ZnS layer was 0.8 nm / s. All layers were deposited using ion source-assisted deposition, and the deposition of each layer was completed at a cavity temperature of 150°C. S5. After the coating system is applied to the first surface of the lens, the cavity is naturally cooled to below 60°C, and the tooling fixture is removed along with the lens. S6, repeat steps S1 to S5 to deposit the same film system on the second side of the lens, wherein the wedge is not cleaned when repeating step S1 and is not placed in the tooling fixture when repeating step S2.

2. The method for preparing a 2-2.3 μm short-wavelength low-reflection film system on a germanium substrate according to claim 1, characterized in that, In step S1, the surface of the lens is cleaned using ultrasound or by hand.

3. The method for preparing a 2-2.3 μm short-wavelength low-reflection film system on a germanium substrate according to claim 2, characterized in that, In step S1, the surface cleaning treatment of the lens is performed by ultrasonic cleaning, which involves polishing with aluminum oxide polishing liquid followed by ultrasonic cleaning with pure water.

4. The method for preparing a 2-2.3 μm short-wavelength low-reflection film system on a germanium substrate according to claim 3, characterized in that, In step S1, the alumina polishing slurry used is a 0.1μm polycrystalline diamond slurry from Nanjing Hengrui Precision Optics Co., Ltd.

5. The method for preparing a 2-2.3 μm short-wavelength low-reflection film system on a germanium substrate according to claim 1, characterized in that, In step S1, the product is a lens or a flat plate.

6. The method for preparing a 2-2.3 μm short-wavelength low-reflection film system on a germanium substrate according to claim 1, characterized in that, In step S1, the thickness of the disc in the plating sheet is 2 mm.

7. The method for preparing a 2-2.3 μm short-wavelength low-reflection film system on a germanium substrate according to claim 1, characterized in that, In step S4, The ion source used is a Hall ion source. When depositing the SiO film, the ion source parameters are: neutralization current of 0.5A, neutralization gas flow rate of 8sccm, anode voltage of 120V, anode current of 1.2A, argon flow rate of 30%, and oxygen flow rate of 70%. When depositing the Ge film, the ion source parameters are: neutralization current of 0.5A, neutralization gas flow rate of 8sccm, anode voltage of 120V, anode current of 1.0A, and argon gas flow rate of 100%. When depositing the ZnS film, the ion source parameters are as follows: neutralization current is 0.5A, neutralization gas flow rate is 8sccm, anode voltage is 120V, anode current is 1.2A, and argon gas flow rate is 100%.

8. The method for preparing a 2-2.3 μm short-wavelength low-reflection film system on a germanium substrate according to claim 1, characterized in that, In step S4, Argon gas is introduced and a vacuum is drawn during the deposition of each film layer to maintain a constant flow vacuum. The constant flow vacuum setting is not lower than 5.0 × 10⁻⁶. -3 Pa; The crystal oscillator method is used to monitor the film thickness by using the corresponding crystal oscillators of multiple crystal oscillators in the crystal controller. After cleaning with the ion source, the crystal controller controls the new crystal oscillator in the multiple crystal oscillators to work accordingly, and the crystal oscillator frequency is not less than 5.99MHz.

9. The method for preparing a 2-2.3 μm short-wavelength low-reflection film system on a germanium substrate according to claim 1, characterized in that, After step S6 is completed, the wedge-shaped sheet in the substrate, together with the corresponding film system on the first surface, has an average reflectivity of less than 0.8% in the 2-2.3 μm band; After step S6 is completed, the disc in the substrate, together with the film system on both sides, undergoes water immersion test, salt spray test, adhesion test, thermal shock test, constant temperature and humidity test, abrasion resistance test, low temperature test, and high temperature test.

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