KR20190133889A - GRAPHENE TRANSPARENT ELECTRODE AND LCoS BASED WAVELENGTH SELECTIVE SWITCH COMPRISING THE SAME - Google Patents

Abstract

The present invention provides a graphene transparent electrode capable of greatly improving light output of a device used for optical communication an infrared wavelength range by having not only excellent light transmittance in visible and infrared regions, but also significantly improved light transmittance in the infrared region in comparison with the visible region. The graphene transparent electrode includes a substrate and at least one layer of graphene transferred onto the substrate.

Description

A wavelength selection switch using a graphene transparent electrode and a silicon liquid crystal element including the same {GRAPHENE TRANSPARENT ELECTRODE AND LCoS BASED WAVELENGTH SELECTIVE SWITCH COMPRISING THE SAME}

The present invention relates to a graphene transparent electrode and a silicon liquid crystal device-based wavelength selection switch including the same, specifically, having excellent light transmittance in the visible region and at the same time having an improved light transmittance in the infrared region is used for optical communication in the infrared wavelength range The present invention relates to a graphene transparent electrode capable of significantly improving the light output of a device, and a silicon liquid crystal device-based wavelength selection switch including the same.

Optical networks use Wavelength Selective Switch (WSS) to dynamically route optical wavelength signals from a source to a destination. Specifically, a wavelength selection switch (WSS) is required to transmit a large amount of information through a single optical fiber through a single optical fiber through optical communication, and to transmit a signal of a specific wavelength to an arbitrary output port in an input signal composed of multiple wavelengths. will be.

In the past, microelectromechanical (MEMS) mirror-based wavelength selection switches have been developed, but recently, liquid crystal on silicon (LCoS) device-based wavelength selection switches have excellent port expandability and are advantageous for alignment. This is emerging as a new technology.

The liquid crystal on silicon (LCoS) device includes a liquid crystal material interposed between a transparent electrode layer having a transparent electrode and a silicon substrate divided into a two-dimensional array of individually addressable pixels. Specifically, incident light for the silicon liquid crystal device-based wavelength selection switch is adjusted through differential phase delay, which is performed by a complementary metal-oxide semiconductor (CMOS) backplane and a liquid crystal layer. For this purpose, a transparent electrode layer is required as the common electrode. Such a transparent electrode needs to be transparent in the infrared wavelength band in order to minimize the loss of the amount of light used for optical communication, and the light transmittance of the transparent electrode layer has an important influence on the intensity of the reflected light.

Specifically, Korean Laid-Open Patent Publication No. 2003-0062886 discloses a silicon liquid crystal device-based wavelength selection switch using indium tin oxide (ITO), which is a representative transparent electrode material currently used, as a transparent electrode. The silicon liquid crystal device-based wavelength selection switch using indium-tin oxide (ITO) as a transparent electrode satisfies transparent properties in the visible light region of 400 to 700 nm wavelength, while transparent properties and light transmittance are rapidly changed in the infrared wavelength range of 1500 nm or more. There is a problem that the light output of the device used for optical communication in the infrared wavelength band is significantly reduced. In addition, in order to use indium tin oxide (ITO) as a transparent electrode in the infrared wavelength range, it is necessary to improve transmittance through additional thin film deposition.

Korean Laid-Open Patent No. 2003-0062886

The present invention has been made to solve the above-described problems, the first problem to be solved by the present invention has an excellent light transmittance in the visible region and at the same time have an improved light transmittance in the infrared region device used for optical communication in the infrared wavelength range It is to provide a graphene transparent electrode and a silicon liquid crystal device-based wavelength selection switch including the same that can significantly improve the light output of the.

In addition, the second problem to be solved by the present invention is to provide a graphene transparent electrode having a low sheet resistance value in the infrared region by a simple process, and can maintain a transparent property, it is easy to commercialize the graphene transparent electrode and including the same To provide a silicon liquid crystal device-based wavelength selection switch.

In order to solve the above problems, the present invention includes a substrate and at least one layer of graphene transferred on the substrate, the graphene is light transmittance of 98% or more in the wavelength range of 1500 ~ 1700nm when the sheet resistance is 400Ω / sq or less It provides a graphene transparent electrode having a.

According to a preferred embodiment of the present invention, the graphene may satisfy all of the following conditions (a) and (b).

(a) The light transmittance in the wavelength band of 1500 ~ 1700nm is higher than the light transmittance in the wavelength band of 500 ~ 700nm

(b) The graphene has a light transmittance of 100% or more in the wavelength range of 1500 ~ 1700nm when the sheet resistance is 400Ω / sq or less

According to another preferred embodiment of the present invention, the graphene may further satisfy the following condition (c).

(c) satisfy the following relation

[Relationship 1]

T ₁₅₀₀ -T ₅₅₀ ≥2.0 (%)

(T ₁₅₀₀ : Light transmittance of graphene (%) in 1500nm wavelength band, T ₅₅₀ : light transmittance of graphene in 550nm wavelength band (%))

In addition, the present invention provides a wavelength selection switch using a silicon liquid crystal device in which a liquid crystal layer is formed between a silicon backplane layer and a glass substrate layer, the reflective layer pixel electrode formed between the silicon backplane layer and the liquid crystal layer to cause light modulation; and It provides a wavelength selection switch using a silicon liquid crystal device, comprising; the graphene transparent electrode of any one of claims 1 to 3 formed between the liquid crystal layer and the glass substrate layer.

According to a preferred embodiment of the present invention, the wavelength selection switch using the silicon liquid crystal device may have a light reflectance of 72% or more in all wavelength bands of 1000 ~ 1600nm.

According to another preferred embodiment of the present invention, the wavelength selection switch using the silicon liquid crystal device may have a light reflectance of 80% or more in all wavelength bands of 1500 ~ 1600nm.

According to another preferred embodiment of the present invention, the wavelength selection switch using the silicon liquid crystal device can satisfy all of the following conditions (d) and (e).

(d) R _G in the wavelength range of 1000 to 1400 nm ≤ R _I

(e) R _G in the wavelength range 1500-1600 nm ≥ R _I

(R _G : Light reflectance (%) _I of the wavelength selection switch using the silicon liquid crystal device : Light reflectance (%) when using indium tin oxide (ITO) instead of graphene as a transparent electrode included in the wavelength selection switch using the silicon liquid crystal device

According to another preferred embodiment of the present invention, the wavelength selection switch using the silicon liquid crystal device can satisfy the following relation 2 in the wavelength band 1530 ~ 1565nm.

[Relationship 2]

1.7 ≤ (R _{G -} R _I ) / R _I × 100 ≤ 4.0

(R _G : Light reflectance (%) of wavelength selection switch using silicon liquid crystal device using graphene transparent electrode, R _I : Light reflectance (%) of wavelength selection switch using silicon liquid crystal device using indium tin oxide (ITO) transparent electrode )

Hereinafter, terms used in the present invention will be briefly described.

The term "graphene" means that a plurality of carbon atoms are covalently linked to each other to form a two-dimensional film (usually sp2 bond). The carbon atoms constituting the graphene form a 6-membered ring as a basic repeating unit, but may further include a 5-membered ring and / or a 7-membered ring. Depending on the amount of 5-membered and / or 7-membered rings that may be included in graphene, the shape of the graphene may vary. Graphene may be formed of a single layer, but a plurality of them may be stacked to form a plurality of layers, and may be up to 100 nm thick.

The present invention not only has excellent light transmittance in both the visible region and the infrared region, but also has a significantly improved light transmittance in the infrared region compared to the visible region, thereby significantly improving the light output of devices used for optical communication in the infrared wavelength range. Provided are a transparent electrode and a silicon liquid crystal device-based wavelength selection switch including the same.

In addition, the present invention can have a low sheet resistance value in the infrared region and at the same time maintain a transparent property, so that the graphene transparent electrode and silicon liquid crystal device-based wavelength selection switch including the same can be used as infrared imaging, infrared sensor, infrared emitter, etc. To provide.

1 is a graph of the transmittance of graphene according to an embodiment of the present invention.
2 is a structural diagram of a silicon liquid crystal device-based wavelength selection switch according to an embodiment of the present invention.
3 is an optical wavelength band separation table.
4 is a reflectance graph of a silicon liquid crystal device-based wavelength selection switch according to an exemplary embodiment of the present invention.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings so that those skilled in the art may easily implement the present invention.

As described above, a silicon liquid crystal device-based wavelength selection switch using indium tin oxide (ITO) as a transparent electrode satisfies transparent properties in the visible region in the 400 to 700 nm wavelength range while the infrared wavelength range of 1500 nm or more. In this case, the transparent property and the light transmittance are sharply lowered, and thus there is a problem that the light output of the device used for the optical communication in the infrared wavelength band is significantly lowered. In addition, in order to use indium tin oxide (ITO) as a transparent electrode in the infrared wavelength range, it is necessary to improve transmittance through additional thin film deposition.

Therefore, the present invention includes a substrate and at least one layer of graphene transferred onto the substrate, wherein the graphene has a light transmittance of 98% or more at a wavelength range of 1500 to 1700 nm when the sheet resistance is 400 Ω / sq or less. The fin transparent electrode was provided to seek to solve the above problems.

As a result, the present invention not only has excellent light transmittance in both the visible and infrared regions, but also has a significantly improved light transmittance in the infrared region compared to the visible region, thereby significantly improving the light output of devices used for optical communication in the infrared wavelength range. have. In addition, the present invention has a low sheet resistance in the infrared region and at the same time can maintain a transparent property has the advantage that can be utilized in various fields such as infrared imaging, infrared sensor, infrared light emitter.

First, the said board | substrate is demonstrated. The substrate may include one or more layers of graphene transferred onto the substrate, and the substrate may be any one that may be commonly used in the art. However, the substrate may be a flat material, and more preferably PET. (polyethylene terephthalate), glass (glass), quartz (quartz), sapphire (wafer), or a wafer (wafer) may be used, and a flexible material may be used.

Next, the graphene included in the graphene transparent electrode of the present invention will be described.

The graphene is a carbon nanomaterial having a two-dimensional planar structure composed of a monoatomic layer formed by strong covalent bonds of carbon atoms, and has high charge mobility, thermal conductivity, and excellent chemical resistance. In addition, the single layer thickness of the graphene is only about the size of one carbon atom may be about 0.25 ~ 0.35nm. The graphene has a metallic property, has conductivity in a layer direction, and has high mobility of a charge carrier, thereby implementing a high-speed electronic device. The graphene has excellent mechanical robustness and chemical stability, has both semiconductor and conductor properties, and is thin, and thus has great applicability to flat panel display devices, transistors, energy storage devices, and nano-sized electronic devices. If the graphene is used, it is easy to manufacture a device using a semiconductor process technology, and in particular, there is an advantage in that large area integration is easy.

The present invention provides a graphene transparent electrode using the graphene, the graphene included in the present invention has a sheet resistance of 400 Ω / sq or less, when the sheet resistance range is satisfied, the light transmittance in the wavelength range of 1500 ~ 1700nm 98% or more to be. Preferably, when the sheet resistance of the graphene is 350 Ω / sq or less, the graphene may have a light transmittance of 99% or more in the wavelength band of 1500 to 1700 nm, and more preferably, when the sheet resistance of the graphene is 300 Ω / sq or less, the wavelength band of 1500 to 1700 nm. Can have a light transmittance of 100% or more. In general, the optical conductivity of graphene is known as a constant value in a wide wavelength range, but doping by increasing the charge density on the graphene surface can suppress the optical conductivity in the infrared region. If the optical conductivity is low, the amount of light absorbed at the infrared wavelength is reduced, thus increasing the transmittance in the infrared region.

Generally, the optical conductivity of graphene is known to have a constant value in a wide wavelength range. However, the present invention is doping through the increase in the charge density on the surface of the graphene is suppressed optical conductivity in the infrared region, thereby reducing the amount of light absorbed in the infrared wavelength to improve the transmittance in the infrared region have.

Accordingly, the graphene of the present invention has a low sheet resistance in the wavelength range of 1500-1700 nm, which is an infrared region, and has a significantly improved light transmittance, and has a transmittance close to 100% even in the wavelength range of 1500-1700 nm. It has an effect of retaining excellent optical properties compared to the material.

In this regard, Figure 1 is a graph of the transmittance of the graphene according to an embodiment of the present invention. Referring to the graph, it can be seen that the graphene included in the present invention has significantly improved transmittance in the wavelength band of 1500 nm or more. That is, it can be seen that the graphene only transmittance of the present invention has a high value of 96.6% at 550 nm, and has a high value of 100.8% at 1500 nm, which is rather effective in the infrared region. In addition, it can be seen that even in the region of more than 1500nm, the total transmittance of graphene and PET decreases little by little, more than 2000nm. In contrast, the transmittance of graphene only of the present invention is stably high at 1500 nm or more, which is maintained in a region of 2000 nm or more, and thus it may be confirmed that the graphene of the present invention has an excellent transmittance over the entire wavelength range. .

The graphene transparent electrode may be used in various applications depending on the conductive properties, the graphene of the present invention should be less than 400Ω / sq. If the sheet resistance of the graphene exceeds 400Ω / sq, light transmittance is significantly lower than 96% in the wavelength range of 1500 to 1700 nm, and it may be difficult to use the transparent electrode.

In addition, if the light transmittance is less than 96% in the wavelength range of 1500 ~ 1700nm which is an infrared region, it is difficult for the graphene to maintain a transparent property in the wavelength band, it is difficult to minimize the loss of the amount of light used for optical communication This can happen. As a result, light loss occurs while the incident light passes through the transparent electrode layer, which may cause a problem that the intensity of the reflected light is significantly lowered.

According to a preferred embodiment of the present invention, the graphene may satisfy all of the following conditions (a) and (b).

(a) The light transmittance in the wavelength band of 1500 ~ 1700nm is higher than the light transmittance in the wavelength band of 500 ~ 700nm

(b) The graphene has a light transmittance of 100% or more in the wavelength range of 1500 ~ 1700nm when the sheet resistance is 400Ω / sq or less

Graphene included in the present invention is more excellent in the light transmittance in the wavelength range of 1500 ~ 1700nm than the light transmittance in the wavelength range of 500 ~ 700nm which is a visible light region. In the wavelength range of 1500-1700 nm, which is an infrared ray region, when the sheet resistance is 400 Ω / sq or less, a remarkably high light transmittance of 100% or more can be satisfied. Accordingly, the present invention not only has excellent light transmittance in both the visible region and the infrared region, but also has a significantly improved light transmittance in the infrared region as compared to the visible region, thereby significantly improving the light output of the device used for optical communication in the infrared wavelength range. It has an effect.

In addition, the graphene may further satisfy the following condition (c).

(c) satisfy the following relation

[Relationship 1]

T ₁₅₀₀ -T ₅₅₀ ≥ 2.0 (%)

(T ₁₅₀₀ : Light transmittance of graphene (%) in 1500nm wavelength band, T ₅₅₀ : light transmittance of graphene (%) in 550nm wavelength band)

In the graphene of the present invention, the light transmittance (T ₁₅₀₀ ) in the ₁₅₀₀ nm wavelength band may be 2% or more higher than the light transmittance (T ₅₅₀ ) in the 550 nm wavelength band. If the T ₁₅₀₀ -T ₅₅₀ is less than 2%, the transparent property of the transparent electrode rapidly decreases in the infrared wavelength band, and a large amount of light loss is generated by the transparent electrode, thereby decreasing the intensity of the reflected light, which is not suitable for the optical communication field. May occur.

The present invention also provides a wavelength selection switch using a silicon liquid crystal device in which a liquid crystal layer is formed between a silicon backplane layer and a glass substrate layer, comprising: a reflective layer pixel electrode formed between the silicon backplane layer and the liquid crystal layer to cause light modulation; It provides a wavelength selection switch using a silicon liquid crystal device comprising a; and any one of the graphene transparent electrode formed between the liquid crystal layer and the glass substrate layer. Accordingly, in addition to excellent light transmittance in both the visible and infrared regions, in the infrared region, the graphene transparent has a significantly improved light transmittance compared to the visible region and can significantly improve the light output of devices used for optical communication in the infrared wavelength range. There is an effect that can provide a silicon liquid crystal device-based wavelength selection switch including an electrode. In addition, it is possible to maintain a transparent property while having a low sheet resistance value in the infrared region, there is an advantage that can be used in various ways such as infrared imaging, infrared sensor, infrared light emitter.

First, a liquid crystal on silicon (LCoS) device used in the present invention will be described. The silicon liquid crystal device controls the direction of incident light in the reflecting plate located at each pixel by using the diffraction phenomenon of light.It has no moving parts, so it is strong in vibration, has excellent port expandability and robustness, loss compensation for each channel, wavelength displacement compensation, It has the advantage of being able to easily perform the function of I / O channel monitoring. The silicon liquid crystal device is manufactured in a reflective type by configuring the pixel electrode on the silicon backplane.

In the silicon liquid crystal device, a liquid crystal layer is formed between the silicon backplane layer and the glass substrate layer. The silicon backplane layer is a silicon wafer substrate, and the glass substrate layer constitutes a touch portion of the device, and a liquid crystal layer is injected between the silicon backplane layer and the glass substrate layer to form a liquid crystal on silicon (LCoS) which is a micro display device. ) Configure the device.

Arbitrary angle according to a specific image pattern displayed in the liquid crystal on silicon (LCoS) device region to which the incident optical signal is touched by using the characteristic that the phase state of the liquid crystal layer changes according to the voltage applied to both ends of the liquid crystal layer As a result, the incident light is deflected and reflected. In general, since the aperture of the input optical signal is larger than the size of a single pixel, the optical signal is reflected through a plurality of pixels. In the liquid crystal on silicon (LCoS) device-based wavelength selection switch of the present invention, each wavelength of incident light is incident on the silicon liquid crystal device according to the image pattern displayed on the liquid crystal on silicon (LCoS) device. Reflect at different angles.

In addition, a reflective layer pixel electrode is formed between the silicon backplane layer and the liquid crystal layer to cause light modulation. The reflective layer pixel electrode may be used for optical communication by changing the intensity of the input light to cause light modulation to put a signal on the light. The reflective layer pixel electrode may be an electrode commonly used in the art, and may be preferably an aluminum reflective electrode.

In this regard, Figure 2 is a structural diagram of a silicon liquid crystal device-based wavelength selection switch according to an embodiment of the present invention. Referring to the drawing, a liquid crystal layer exists between the silicon backplane layer and the glass substrate layer, and a reflective layer pixel electrode is formed between the silicon backplane layer and the glass substrate layer. In addition, since the graphene transparent electrode is formed between the glass substrate layer and the liquid crystal layer, it can be seen that the light passes through the graphene transparent electrode twice. Therefore, in order to minimize the loss of light, it is necessary for the graphene transparent electrode to maintain a transparent property in the infrared wavelength band, and the transmittance of the transparent electrode has an important effect on the intensity of the reflected light, and thus the excellent transmittance of the graphene transparent electrode is necessary. can confirm.

Meanwhile, any one of the graphene transparent electrodes of the present invention described above may be formed between the liquid crystal layer and the glass substrate layer to form a wavelength selection switch using a silicon liquid crystal device. This not only has excellent light transmittance in both the visible and infrared regions, but also has a significantly improved light transmittance in the infrared region compared to the visible region, which can significantly improve the light output of devices used for optical communication in the infrared wavelength range. An element-based wavelength selection switch can be provided. Accordingly, the present invention has an advantage that can be utilized in various ways such as infrared imaging, infrared sensor, infrared light emitter.

The wavelength selection switch using the silicon liquid crystal device of the present invention may have a light reflectance of 72% or more in all wavelength bands of 1000 to 1600nm, and more preferably, light reflectance of 80% or more in all wavelength bands of 1500 to 1600nm. That is, according to the preferred embodiment of the present invention, the light reflectance may be 72% or more at all wavelengths in the range of 1000 to 1600 nm, and at the same time, the light reflectance may be 80% or more at all wavelengths in the range of 1500 to 1600 nm.

According to a preferred embodiment of the present invention, the wavelength selection switch using the silicon liquid crystal device of the present invention can satisfy both of the following conditions (d) and (e).

(d) R _G in the wavelength range of 1000 to 1400 nm ≤ R _I

(e) R _G in the wavelength range 1500-1600 nm ≥ R _I

(R _G : Light reflectance (%) of wavelength selection switch using silicon liquid crystal device using graphene transparent electrode, R _I : Light reflectance (%) of wavelength selection switch using silicon liquid crystal device using indium tin oxide (ITO) transparent electrode )

In this case, R _G means the light reflectance of the wavelength selection switch using the silicon liquid crystal device of the present invention, R _I is the liquid crystal layer and the glass substrate included in the wavelength selection switch using the silicon liquid crystal device of the present invention It refers to the light reflectance when using indium tin oxide (ITO) commonly used in the art in place of the graphene transparent electrode formed between the layers.

Through this, the present invention can provide a wavelength selection switch using a silicon liquid crystal device suitable for the infrared region of the 1500 ~ 1600nm wavelength range, there is an advantage that can be utilized in various technical fields using infrared, such as infrared imaging, infrared sensor, infrared emitter. .

Meanwhile, FIG. 3 is an optical wavelength band classification table, and according to the International Telecommunication Union-Telecommunication Standardization Sector (ITUT-T) optical wavelength band classification, C band (1530 nm to 1565 nm), L band (1565 nm to 1625 nm), and U band for medium to long distance transmission A light source with a wavelength in the band (1625 nm to 1675 nm) is used. Among them, the C band is a low loss band used for medium and long distance transmission, and it is necessary to improve light transmittance in the wavelength band to improve light output of devices used in optical communication.

Accordingly, the present invention provides a wavelength selection switch using a silicon liquid crystal device having a significantly improved light reflectance in the C band, that is, in the wavelength band 1530nm to 1565nm used for optical communication. In this regard, according to a preferred embodiment of the present invention,

The wavelength selection switch using the silicon liquid crystal device of the present invention may satisfy the following Equation 2 in the wavelength range of 1530-1565 nm.

[Relationship 2]

1.7 ≤ (R _{G -} R _I ) / R _I × 100 ≤ 4.0

(R _G : Light reflectance (%) of the wavelength selection switch using the silicon liquid crystal device, R _I : Light when the indium tin oxide (ITO) is used instead of graphene as a transparent electrode included in the wavelength selection switch using the silicon liquid crystal device. reflectivity(%))

The relation 2 may preferably be 1.7 ≦ (R _{G −} R _I ) / R _I × 100 ≦ 3.8, and more preferably 1.7 ≦ (R _{G −} R _I ) / R _I × 100 ≦ 3.6 .

Through this, the present invention is remarkably excellent in the light reflectance in the C band region, there is an effect that can provide a wavelength selection switch using a silicon liquid crystal device suitable for use in the wavelength region.

Specifically, Figure 4 is a graph of the reflectance of the silicon liquid crystal device-based wavelength selection switch according to an embodiment of the present invention. Referring to the graph, it can be seen that the wavelength selection switch using the silicon liquid crystal device including the graphene transparent electrode of the present invention has a significantly high reflectance in the wavelength range of 1500 to 1600 nm, and thus can be used in various technical fields using infrared rays. .

As a result, the wavelength selection switch using the graphene transparent electrode of the present invention and the silicon liquid crystal device including the same have excellent light transmittance in the visible region and at the same time have an improved light transmittance in the infrared region. Significantly improved light output can be utilized in various technical fields using infrared, such as infrared imaging, infrared sensors, infrared emitters.

Hereinafter, the present invention will be described in more detail with reference to specific examples.

Example  One

A Cu plate at 35 ° C. was charged by CVD. CH ₄ was flowed into the furnace at about 1000 ° C. at a rate of 30 sccm for about 5 minutes. Then, in the atmosphere of H ₂ , cooling was carried out at a rate of 60 ° C./min up to 600 ° C. and at a rate of 40 ° C./min up to room temperature, thereby forming graphene on Cu. The laminate of Cu and graphene was immersed in a (NH ₄ ) S 2 O 8 4 wt% aqueous solution for 120 minutes to remove Cu. The graphene thus obtained was immersed in a composition containing 3 wt% of 1,2,4-benzotriazine, 3 wt% of H ₂ O ₂ , 9 wt% of H ₂ SO _4, and the balance of water for 40 minutes. Doped graphene was obtained. A graphene transparent electrode provided on a glass substrate using the doped graphene was prepared. Next, a reflective layer pixel electrode was provided on the silicon backplane layer, and a sealing material was applied. Thereafter, liquid crystal was applied to form a liquid crystal layer. The graphene transparent electrode formed on the glass substrate layer was laminated on the liquid crystal layer, and the sealing material was cured to prepare a wavelength selection switch using a silicon liquid crystal device.

Comparative example  One

Indium tin oxide (ITO) electrode was used in place of the graphene transparent electrode was carried out in the same manner as in Example 1.

Experimental Example  1. Reflectance measurement

The reflectance of the wavelength selection switch using the silicon liquid crystal device manufactured through Example 1 and Comparative Example 1 was measured, and the results are shown in the graphs of Table 1 and FIG. 4. In Table 1, the increase rate of the reflectance is represented by rounding to two decimal places.

Table 1

Referring to Table 1, it can be seen that Example 1 including the graphene transparent electrode of the present invention is significantly superior in reflectance compared to Comparative Example 1. In particular, the 1500 nm or more shows a remarkably excellent increase rate, 1565 nm shows a high increase rate of 3.49% it can be seen that the reflectance of the present invention is remarkably excellent.

Claims (8)

A substrate and at least one layer of graphene transferred onto the substrate,
The graphene is a graphene transparent electrode having a light transmittance of 98% or more in the wavelength band of 1500 ~ 1700nm when the sheet resistance is 400Ω / sq or less.
The method of claim 1,
The graphene is a graphene transparent electrode, characterized in that to satisfy all of the following conditions (a) and (b).
(a) The light transmittance in the wavelength band of 1500 ~ 1700nm is higher than the light transmittance in the wavelength band of 500 ~ 700nm
(b) The graphene has a light transmittance of 100% or more in the wavelength range of 1500 ~ 1700nm when the sheet resistance is 400Ω / sq or less
The method of claim 1,
The graphene is a graphene transparent electrode, characterized in that further satisfying the following condition (c).
(c) satisfy the following relation
[Relationship 1]
T ₁₅₀₀ -T ₅₅₀ ≥ 2.0 (%)
(T ₁₅₀₀ : Light transmittance of graphene (%) in 1500nm wavelength band, T ₅₅₀ : light transmittance of graphene in 550nm wavelength band (%))
In a wavelength selection switch using a silicon liquid crystal device in which a liquid crystal layer is formed between a silicon backplane layer and a glass substrate layer,
A reflective layer pixel electrode formed between the silicon backplane layer and the liquid crystal layer to cause light modulation; and
And a graphene transparent electrode according to any one of claims 1 to 3 formed between the liquid crystal layer and the glass substrate layer.
The method of claim 4, wherein
A wavelength selection switch using a silicon liquid crystal device, characterized in that the light reflectance is 72% or more in all wavelength bands of 1000 ~ 1600nm.
The method of claim 5,
A wavelength selection switch using a silicon liquid crystal device, characterized in that the light reflectance is more than 80% in all wavelength bands of 1500 ~ 1600nm.
The method of claim 4, wherein
A wavelength selection switch using a silicon liquid crystal device, characterized by satisfying all of the following conditions (d) and (e).
(d) R _G in the wavelength range of 1000 to 1400 nm ≤ R _I
(e) R _G in the wavelength range 1500-1600 nm ≥ R _I
(R _G : Light reflectance (%) of the wavelength selection switch using the silicon liquid crystal device, R _I : Light when the indium tin oxide (ITO) is used instead of graphene as a transparent electrode included in the wavelength selection switch using the silicon liquid crystal device. reflectivity(%))
The method of claim 4, wherein
A wavelength selective switch using a silicon liquid crystal device, characterized in that the following relation 2 is satisfied in the wavelength range of 1530-1565 nm.
[Relationship 2]
1.7 ≤ (R _{G -} R _I ) / R _I × 100 ≤ 4.0
(R _G : Light reflectance (%) of wavelength selection switch using silicon liquid crystal device using graphene transparent electrode, R _I : Light reflectance (%) of wavelength selection switch using silicon liquid crystal device using indium tin oxide (ITO) transparent electrode )

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