An extreme ultraviolet band wide band gap high reflectivity photonic crystal film

Abstract

The present application relates to the technical field of optical film, more particularly, the present application relates to a kind of photonic crystal film of wide band gap high reflectivity in extreme ultraviolet band;The photonic crystal film can be prepared by electrochemical assisted self-assembly deposition method, comprising the following steps: weighing water, ethanol, silicon source, surfactant, sodium nitrate, hydrochloric acid is carried out pre-hydrolysis reaction, the cathode potential is applied on the conductive substrate to carry out electrochemical assisted self-assembly deposition for a certain time, the electrode is immediately washed with water, 130 DEG C drying, then the mesoporous film is calcined in air at 450 DEG C for a certain time, photonic crystal film is obtained;The mesoporous aperture of the photonic crystal film of the present application can be adjusted in the range of 2nm-4nm, and high reflectivity can be obtained in the extreme ultraviolet band of 5-12nm, and the preparation time is short, the preparation thickness can be adjusted in the range of 20nm-200nm, flexible adjustment, simple operation, without special equipment and conditions, and the preparation cost is low.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of optical thin films, and more particularly to a photonic crystal thin film with a wide band gap and high reflectivity in the extreme ultraviolet band. BACKGROUND

[0002] Optical thin films are one or more films coated on the surface of an optical part to change the optical properties of the surface of the part, which can be metal films or dielectric films, and are applied in the fields of laser systems, optical communication, optical display, space technology, etc. Based on the interference of light, when light is projected onto the surface layer of the thin film, part of the light is reflected on the surface, and the remaining part is refracted into the film layer, of which part is absorbed to become heat energy, and the remaining part is transmitted. Optical thin film devices are prepared into reflective films, anti-reflective films, transmissive films, polarizing films and interference filters, etc. by using this performance of light. With the increasing precision and complexity of optical systems, higher and higher requirements are put forward for imaging quality, especially for laser systems in the extreme ultraviolet band (5-40 nm), and higher and higher requirements are put forward for high-performance extreme ultraviolet optical thin films (wide band gap and high reflectivity).

[0003] Since the 1980s, the improvement of nanoscale coating technology and ultra-precision optical processing technology has made great progress in the theory and preparation technology of optical thin films. However, when the wavelength is in the extreme ultraviolet band, the photon energy is greater than the band gap of many materials, so the extreme ultraviolet laser irradiation will cause the electrons in the material to transition from the valence band to the conduction band, resulting in strong intrinsic absorption. Therefore, it is difficult for metal single-layer films and multilayer films prepared by conventional design methods to meet the development needs of high reflectivity, which has become a bottleneck restricting its future development. The commonly used materials at present are mainly fluorides, high-bandwidth oxides, etc., among which the fluoride materials are mainly MgF2 and AlF3, the high-refractive-index materials are LaF3 and GdF3, and the oxides are mainly SiO2 and Al2O3. These materials need to be prepared by high-energy deposition technology, such as electron beam evaporation ion beam assisted polishing method (reflectivity up to 69.5%, incident wavelength 13.0 nm, incident angle 11.5°), magnetron sputtering (reflectivity up to 68%, incident wavelength 12.75 nm, incident angle 11.5°), ion beam sputtering (reflectivity up to 52%, incident wavelength 13-15 nm, incident angle 0-16°), etc. In addition, the Lawrence-Livermore group in the United States has conducted research on the preparation technology of multilayer films with shorter wavelength, and the Ru / B4C multilayer film prepared by them has a reflectivity of 20% at 7 nm; the 500-layer Mo / Y multilayer film prepared by the Montcalm group in Canada has a reflectivity of 13% at 8.1 nm. Since the thickness of each layer of the multilayer film is about 1 / 4 of the working wavelength, the thickness of the extreme ultraviolet multilayer film is extremely thin, and the control precision is required to be high (better than 0.1 nm). However, due to the limitations of materials and preparation technology, the research on extreme ultraviolet optical thin film materials still has the common problems of narrow wavelength range and low reflectivity, which need to be solved urgently.

[0004] Photonic crystal is a microstructure material with different refractive index materials changing periodically. The most important feature of photonic crystal is to use the scattering and multiple interference of light in the periodic structure to form a photonic band gap, that is, the light falling in the band gap is prohibited to propagate. The position of the photonic band gap is mainly determined by the refractive index (or dielectric constant) of the dielectric and the lattice parameter of the photonic crystal. According to this characteristic, the propagation of electromagnetic waves of different wavelengths can be selectively controlled. At present, the main methods for preparing photonic crystals are focused ion beam, femtosecond laser interference method, precision machining method, colloidal crystal method and inverse opal structure method, etc. However, these methods are commonly used for preparing visible and near-infrared band photonic crystals, and there is little research on shorter waveband such as extreme ultraviolet band photonic crystals.

[0005] Ordered mesoporous molecular sieve film has a wide application in catalysis, adsorption, separation, drug release and chemical sensing due to its high specific surface area, large pore volume and uniform and adjustable pore size. The special pore structure of the mesoporous molecular sieve is very suitable for the structure of two-dimensional photonic crystal, which makes up for the difficulty in preparation of the waveband. Meanwhile, the unique pore structure of the mesoporous molecular sieve provides a possibility for application in the extreme ultraviolet waveband photonic crystal. SUMMARY

[0006] The technical problem to be solved by the present application is that the current multilayer film technology and photonic crystal are difficult to obtain wide waveband range and high reflectivity in the extreme ultraviolet waveband, especially in the lower waveband below 13 nm. Based on this, the purpose of the present application is to provide a photonic crystal film with wide band gap and high reflectivity suitable for the 5-12 nm extreme ultraviolet waveband.

[0007] To this end, the technical solution adopted by the present application is a photonic crystal film with wide band gap and high reflectivity in the extreme ultraviolet waveband, wherein the photonic crystal film is a mesoporous silica film with hexagonal arranged and vertically oriented pore channels, the thickness of the mesoporous film structure is 20-200 nm, and the mesopore size is 2-4 nm.

[0008] The vertically oriented mesoporous silica film has the photonic crystal band gap characteristics due to its unique hexagonal ordered mesoporous structure, and the band gap energy corresponds to the extreme ultraviolet waveband range. Through experiments, it is verified that when the incident angle is less than 3°, the mesopore size of the photonic crystal film of the present application can obtain high reflectivity in the 5-12 nm extreme ultraviolet waveband, and the reflectivity can reach 60% to 80%.

[0009] The photonic crystal film of the present application can be prepared by electrochemical assisted self-assembly deposition method, which has the advantages of simple preparation process, short time and low preparation cost.

[0010] The present application also provides a preparation method of the photonic crystal film by electrochemical assisted self-assembly deposition method, which specifically comprises the following steps:

[0011] 1) A surfactant, sodium nitrate and water and ethanol solution are weighed and added, dissolved to be clear, then a silicon source is added, and hydrochloric acid is used to adjust the pH value to 3, and pre-hydrolysis is carried out for 2.5 h to obtain a mixed solution;

[0012] The molar ratio of the surfactant, the silicon source, the water, the ethanol and the sodium nitrate in the mixed solution is 0.064-0.122:0.2-0.38:111.11:34.25:0.2.

[0013] 2) Put the conductive substrate in the above solution, and apply a constant voltage of -1.2V to -1.5V or a constant current of -0.3mA·cm-2 to -0.74mA·cm-2 for 10s to 40s.

[0014] The concentration of the surfactant used for preparing the mixed solution is 16-30.4 mM, the concentration of the silicon source is 50-95 mM, and the concentration of sodium nitrate is 50 mM.

[0015] Preferably, the molar ratio of the surfactant, the silicon source, water, ethanol, and sodium nitrate in the mixed solution is 0.070-0.096:0.22-0.30:111.11:34.25:0.2:0.012.

[0016] In the present application, the surfactant is one of dodecyl trimethyl ammonium bromide, tetradecyl trimethyl ammonium bromide, hexadecyl trimethyl ammonium bromide, octadecyl trimethyl ammonium bromide, and docosyl trimethyl ammonium bromide.

[0017] The silicon source is one of tetraethyl orthosilicate, white carbon black, and silica sol.

[0018] The substrate is one of ITO conductive glass, single-throw silicon wafer, stainless steel, Au electrode, and Cu electrode.

[0019] Compared with the prior art, the present application has the following beneficial effects:

[0020] The present application utilizes the mesoporous silica film with vertically oriented channels as a two-dimensional photonic crystal structure for constructing an extreme ultraviolet (EUV) band wide-bandgap and high-reflectivity film.

[0021] The photonic crystal film of the present application can be prepared by an electrochemical-assisted self-assembly deposition method. First, the surfactant and sodium nitrate are dissolved in water and ethanol, and then stirred uniformly. The pH value is adjusted to 3 by hydrochloric acid. An appropriate amount of tetraethyl orthosilicate is added to the solution and stirred for 2.5h. Then, the substrate is placed in the above sol, and a cathode potential or current is applied under constant potential or constant current conditions for 10s to 40s for deposition. Finally, drying, aging, and calcination are performed to remove the surfactant, and the photonic crystal film is obtained. The preparation method of the photonic crystal film of the present application has the advantages of simple process, short time, and low preparation cost. The thickness can be flexibly adjusted within the range of 20nm to 200nm by adjusting the deposition time, voltage, silicon source concentration, and multiple deposition, and the operation is simple without the need for special equipment and conditions. The preparation cost is low, and the method has great application prospects.

[0022] The present application combines the unique band gap characteristics of photonic crystals and ordered mesoporous films, and constructs a mesoporous two-dimensional photonic crystal film material with a wide band gap and high reflectivity in the 5-12 nm extreme ultraviolet band. By introducing a hexagonal arrangement of vertically oriented mesoporous two-dimensional photonic crystal film structure, high reflectivity in the extreme ultraviolet band is obtained. And the vertically oriented mesoporous silica photonic crystal film is prepared by electrochemical assisted self-assembly deposition method, which provides a new idea for designing and preparing a thin film with a wide band gap and high reflectivity in the extreme ultraviolet band of lower wave band, and provides a new low-cost preparation method for photonic crystal preparation. BRIEF DESCRIPTION OF DRAWINGS

[0023] Figure 1 The high-resolution electron microscope image of the film of Example 1 in the present application.

[0024] Figure 2 The high-resolution electron microscope image of the film of Example 2 in the present application.

[0025] Figure 3 The reflectivity graph of the film of Example 1 in the present application in the 5-12 nm wave band range.

[0026] Figure 4 The reflectivity graph of the film of Example 2 in the present application in the 5-12 nm wave band range.

[0027] Figure 5 The reflectivity graph of the film of Example 5 in the present application in the 5-12 nm wave band range. DETAILED DESCRIPTION

[0028] The technical solutions of the present application will be further described in detail below in combination with specific embodiments.

[0029] The technical solutions in the embodiments of the present application will be described clearly and completely below in combination with the drawings of the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, not all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor are within the scope of protection of the present application.

[0030] The photonic crystal film structure with high reflectivity in the extreme ultraviolet band is characterized in that it is an ordered mesoporous film with vertically oriented channels, and the film material is silica.

[0031] The thickness of the mesoporous film is 20 nm-200 nm.

[0032] The mesoporous channels are arranged in a hexagonal arrangement, and the pore size is 2 nm-4 nm.

[0033] The thin film material can be prepared by an electrochemical assisted self-assembly deposition method. The specific preparation embodiment is as follows.

[0034] Example 1

[0035] The photonic crystal thin film structure for high reflectivity in the extreme ultraviolet band is prepared by the electrochemical assisted self-assembly deposition method. The adopted substrate is ITO conductive glass (1 cm*1 cm), the deposition voltage is -1.3 V, and the counter electrode is a platinum electrode. The silicon source is tetraethyl orthosilicate, the silicon source concentration is 55 mM, the surfactant is cetyltrimethylammonium bromide (CTAB), the CTAB concentration is 17.6 mM, the molar ratio of surfactant: silicon source: water: ethanol: sodium nitrate in the mixed solution is 0.0712:0.2236:111.11:34.25:0.2, and the deposition time is 25 s. As shown in FIG. 1, the photonic crystal thin film structure for high reflectivity in the extreme ultraviolet band is prepared by the electrochemical assisted self-assembly deposition method. Figure 1 As shown in the high-resolution electron microscope image, the mesoporous channels of the thin film present regular hexagonal arrangement, the thickness of the thin film is about 82 nm, and the pore size is about 2.65 nm. Figure 4 The reflectivity spectrum of the photonic crystal thin film is prepared.

[0036] Example 2

[0037] The photonic crystal thin film structure for high reflectivity in the extreme ultraviolet band is prepared by the electrochemical assisted self-assembly deposition method. The adopted substrate is ITO conductive glass (2 cm*2 cm), the deposition voltage is -1.3 V, and the counter electrode is a platinum electrode. The silicon source is tetraethyl orthosilicate, the silicon source concentration is 75 mM, the surfactant is cetyltrimethylammonium bromide (CTAB), the CTAB concentration is 24 mM, the molar ratio of surfactant: silicon source: water: ethanol: sodium nitrate in the mixed solution is 0.0968:0.3025:111.11:34.25:0.2, and the deposition time is 15 s. As shown in FIG. 2, the photonic crystal thin film structure for high reflectivity in the extreme ultraviolet band is prepared by the electrochemical assisted self-assembly deposition method. Figure 2 As shown in the high-resolution electron microscope image, the mesoporous channels of the thin film present regular hexagonal arrangement, the thickness of the thin film is about 55 nm, and the pore size is about 2.65 nm. Figure 4 The reflectivity spectrum of the photonic crystal thin film is prepared.

[0038] Example 3

[0039] The photonic crystal thin film structure for high reflectivity in the extreme ultraviolet band is prepared by using the electrochemical assisted self-assembly deposition method. The substrate used is ITO conductive glass (2 cm*2 cm), the deposition voltage is -1.4 V, and the counter electrode is a platinum electrode. The silicon source is tetraethyl orthosilicate, the silicon source concentration is 65 mM, the surfactant is cetyltrimethylammonium bromide (CTAB), the concentration of CTAB is 20.8 mM, and the molar ratio of surfactant: silicon source: water: ethanol: sodium nitrate in the mixed solution is 0.0845: 0.2894: 111.11: 34.25: 0.2,

[0040] The deposition time is 20 s. The mesoporous channels of the thin film present regular hexagonal arrangement, the thickness of the thin film is about 68 nm, and the pore size is about 2.65 nm.

[0041] Example 4

[0042] The photonic crystal thin film structure for high reflectivity in the extreme ultraviolet band is prepared by using the electrochemical assisted self-assembly deposition method. The substrate used is ITO conductive glass (2 cm*2 cm), the deposition voltage is -1.3 V, and the counter electrode is a platinum electrode. The silicon source is tetraethyl orthosilicate, the silicon source concentration is 75 mM, the surfactant is cetyltrimethylammonium bromide (CTAB), the concentration of CTAB is 24 mM, and the molar ratio of surfactant: silicon source: water: ethanol: sodium nitrate in the mixed solution is 0.0968: 0.3025: 111.11: 34.25: 0.2, the deposition time is 15 s, and the pore size is about 2.65 nm. After the prepared thin film is washed, a second deposition is carried out under the same conditions, and the thickness of the thin film is about 103 nm.

[0043] Example 5

[0044] The photonic crystal thin film structure for high reflectivity in the extreme ultraviolet band is prepared by using the electrochemical assisted self-assembly deposition method. The substrate used is ITO conductive glass (5 cm*5 cm), the deposition voltage is -1.3 V, and the counter electrode is a platinum electrode. The silicon source is tetraethyl orthosilicate, the silicon source concentration is 55 mM, the surfactant is octadecyltrimethylammonium bromide (C18TAB), the concentration of C18TAB is 17.6 mM, and the molar ratio of surfactant: silicon source: water: ethanol: sodium nitrate in the mixed solution is 0.0713: 0.2236: 111.11: 34.25: 0.2, and the deposition time is 25 s. The mesoporous channels of the thin film present regular hexagonal arrangement, the thickness of the thin film is about 62 nm, and the pore size is about 3.0 nm. Figure 4 To obtain the reflectivity spectrum of the photonic crystal thin film.

[0045] Example 6

[0046] The photonic crystal thin film structure for high reflectivity in the extreme ultraviolet band is prepared by using electrochemical assisted self-assembly deposition method. The substrate used is ITO conductive glass (2 cm*2 cm), the deposition current voltage is -1.3 V, the counter electrode is a platinum electrode. The silicon source is tetraethyl orthosilicate, the silicon source concentration is 75 mM, the surfactant is dodecyl trimethyl ammonium bromide (DTAB), the concentration of DTAB is 37.5 mM, the molar ratio of surfactant: silicon source: water: ethanol: sodium nitrate in the mixed solution is 0.0966:0.3025:111.11:34.25:0.2, and the deposition time is 20 s. The mesoporous channels of the thin film present regular hexagonal arrangement, the film thickness is about 43 nm, and the pore size is about 2.0 nm.

[0047] Example 7

[0048] The photonic crystal thin film structure for high reflectivity in the extreme ultraviolet band is prepared by using electrochemical assisted self-assembly deposition method. The substrate used is stainless steel sheet (1 cm*1 cm), the deposition voltage is -1.2 V, the counter electrode is a platinum electrode. The silicon source is silica sol, the silicon source concentration is 55 mM, the surfactant is dodecyl trimethyl ammonium bromide (CTAB), the concentration of CTAB is 17.6 mM, the molar ratio of surfactant: silicon source: water: ethanol: sodium nitrate in the mixed solution is 0.0968:0.3025:111.11:34.25:0.2, and the deposition time is 20 s. The mesoporous channels of the thin film present regular hexagonal arrangement, the film thickness is about 59 nm, and the pore size is about 3.7 nm.

[0049] Example 8

[0050] The photonic crystal thin film structure for high reflectivity in the extreme ultraviolet band is prepared by using electrochemical assisted self-assembly deposition method. The substrate used is Au electrode sheet (1 cm*1 cm), the deposition voltage is -1.2 V, the counter electrode is a platinum electrode. The silicon source is silica sol, the silicon source concentration is 55 mM, the surfactant is dodecyl trimethyl ammonium bromide (CTAB), the concentration of CTAB is 17.6 mM, the molar ratio of surfactant: silicon source: water: ethanol: sodium nitrate in the mixed solution is 0.0968:0.3025:111.11:34.25:0.2, and the deposition time is 20 s. The mesoporous channels of the thin film present regular hexagonal arrangement, the film thickness is about 59 nm, and the pore size is about 3.7 nm.

[0051] Example 9

[0052] The photonic crystal film structure for high reflectivity in the extreme ultraviolet band is prepared by using electrochemical assisted self-assembly deposition method. The substrate used is a Cu sheet (2 cm*2 cm), the deposition voltage is -1.3 V, and the counter electrode is a platinum electrode. The silicon source is tetraethyl orthosilicate, the silicon source concentration is 65 mM, the surfactant is cetyltrimethylammonium bromide (CTAB), the CTAB concentration is 20.8 mM, the molar ratio of surfactant: silicon source: water: ethanol: sodium nitrate in the mixed solution is 0.0845:0.2894:111.11:34.25:0.2, and the deposition time is 25 s. The mesoporous channels of the film present regular hexagonal arrangement, the film thickness is about 67 nm, and the pore size is about 2.65 nm.

[0053] Example 10

[0054] The photonic crystal film structure for high reflectivity in the extreme ultraviolet band is prepared by using electrochemical assisted self-assembly deposition method. The substrate used is a single-polished silicon wafer (1 cm*1 cm), the deposition voltage is -1.5 V, and the counter electrode is a platinum electrode. The silicon source is tetraethyl orthosilicate, the silicon source concentration is 55 mM, the surfactant is cetyltrimethylammonium bromide (CTAB), the CTAB concentration is 17.6 mM, the molar ratio of surfactant: silicon source: water: ethanol: sodium nitrate in the mixed solution is 0.0712:0.2236:111.11:34.25:0.2, and the deposition time is 30 s. The mesoporous channels of the film present regular hexagonal arrangement, the film thickness is about 53 nm, and the pore size is about 2.65 nm.

[0055] The above detailed the preferred embodiments of the patent, but the patent is not limited to the above embodiments, and various changes can be made within the knowledge of those skilled in the art without departing from the spirit of the patent.

Claims

1. An extreme ultraviolet band wide band gap high reflectivity photonic crystal thin film, characterized in that, The structure of the photonic crystal thin film is a vertical oriented mesoporous thin film structure, the thickness of the mesoporous thin film structure is 20-200nm, the mesoporous pore size is 2nm-4nm, and the mesoporous channel is hexagonal arrangement; the material of the photonic crystal thin film is silicon dioxide. When the incident angle is 3°>i>0°, the reflectivity of the photonic crystal thin film to the 5-12nm extreme ultraviolet band is higher than 65%.

2. The photonic crystal film of claim 1, wherein the photonic crystal film has a wide bandgap and a high reflectivity in an extreme ultraviolet (EUV) wavelength range. The preparation method comprises the following steps: The silicon source, the surfactant, the sodium nitrate, the water and the ethanol are stirred uniformly, the pH value of the mixture is adjusted to 3 by hydrochloric acid, and the mixture is hydrolyzed sufficiently to obtain a mixed solution; the molar ratio of the surfactant, the silicon source, the water, the ethanol, the sodium nitrate and the hydrochloric acid in the mixed solution is 0.064-0.122:0.2-0.38:111.11:34.25:0.2:0.

012. The conductive substrate is placed in the above solution, and a constant voltage of-1.2V to-1.5V or a constant current of-0.3mA•cm-2 to-0.74mA•cm-2 is applied for 10s-40s.

3. The photonic crystal film of claim 2, wherein the photonic crystal film has a high reflectivity in an extreme ultraviolet (EUV) band. The molar ratio of the surfactant, the silicon source, the water, the ethanol and the sodium nitrate in the mixed solution is 0.070-0.096:0.22-0.30:111.11:34.25:0.2:0.

012.

4. The photonic crystal film of claim 2 or 3, wherein the photonic crystal film has a wide bandgap in the extreme ultraviolet range and a high reflectivity. The surfactant is one of dodecyl trimethyl ammonium bromide, tetradecyl trimethyl ammonium bromide, hexadecyl trimethyl ammonium bromide, octadecyl trimethyl ammonium bromide and docosyl trimethyl ammonium bromide.

5. The photonic crystal film of claim 2 or 3, wherein the photonic crystal film has a wide bandgap in the extreme ultraviolet range and a high reflectivity. The silicon source is one of tetraethyl orthosilicate, white carbon black and silica sol.

6. The photonic crystal film of claim 2 or 3, wherein the photonic crystal film has a wide bandgap in the extreme ultraviolet range and a high reflectivity. The substrate is one of ITO conductive glass, single-throw silicon wafer, stainless steel, Au electrode and Cu electrode.

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