TWI571430B - Method of making photonic crystal - Google Patents

Description

Method for preparing photonic crystal

The present invention relates to a method of preparing a photonic crystal. In particular, it relates to a method of preparing a photonic crystal having submicron pores.

Physical Vapor Transport (PVT) and Physical Vapor Deposition (PVD) are used as the technology for growing strontium carbide, which is also used as a technology for mass production of wafers. For example, a method of growing ruthenium carbide crystals disclosed in U.S. Patent No. 5,746,827 uses a physical vapor phase transfer (PVT) method to grow large-sized crystals.

In addition, a photonic crystal is a structure in which a refractive index or a dielectric constant of a material changes periodically in a two-dimensional or three-dimensional space, and the structure mimics the arrangement of atoms in a solid crystal. Therefore, in the related prior art, such as the patents of the Republic of China Patent Nos. I318418 and 8384988, most of them are grown into an approximate three-dimensional structure in a two-dimensional manner, and the photonic crystal can only be applied to the transmission in the two-dimensional direction. Due to the difficulty in production, three-dimensional photonic crystals have been behind the two-dimensional photonic crystals in research progress. One of the reasons why three-dimensional crystal fabrication methods have not been published in China and the United States is that it is traditionally difficult to use deposition methods to alternately deposit different atoms into a multi-layered layered structure. For example, U.S. Patent No. 8,384,988 controls the deposition of atoms by means of electrochemical voltage. U.S. Patent No. 8,309,113 and U.S. Patent No. 7,799,378 use an etchable material or a microparticle of a polymer material as a filler between different media, and a multi-layer stack to form a three-dimensional structure. . U.S. Patent Nos. 7,094,161 and 7,719,216 each use optical methods to prepare photonic crystals. The former uses the principle of laser optical diffraction to generate interference fringes to prepare the periodic structure of the photonic crystal, and the latter uses the reticle method to generate the same photonic crystal period as the photomask. Sexual structure. Photonic crystal materials produced by techniques such as electrochemical methods, etching, optical exposure development, and semiconductor processes are often fabricated in a simple process that is easy to process and etch, and the selectivity of materials of such photonic crystals is easily limited.

The interior of the photonic crystal has different media that are periodically arranged. For example, suppose a photonic crystal has a first medium and a second medium which are periodically arranged, wherein the first medium has a higher refractive index n1 and the second medium has a higher refractive index n2, then the second medium The refractive index ratio is n1/n2, and the larger the ratio, the larger the refractive index difference between the media, which will make the photonic crystal have a larger photonic band gap.

Common materials for photonic crystals include: cerium oxide having a refractive index (n) of 1.45; and zinc oxide having a refractive index (n) of 2.0. Compared with ceria and zinc oxide, the wide bandgap material has a higher refractive index, for example, niobium carbide, which has a refractive index (n) of 2.65, aluminum nitride, a refractive index (n) of 2.15, and nitridation. Gallium has a refractive index (n) of 2.4.

In the case where air having a refractive index (n) close to 1 is also used as the second medium having a lower refractive index, the larger the refractive index of the first medium, the larger the refractive index difference of the photonic crystal, and the larger Photonic band gap. The use of a wide energy gap material having a higher refractive index as the first medium contributes to a difference in refractive index between the two dielectrics to obtain a photonic crystal having a larger photonic band gap.

Therefore, it is necessary to provide a method for preparing a photonic crystal which can utilize a wide energy gap material to solve the problem of insufficient refractive index difference between two dielectrics in a conventional photonic crystal.

In order to solve the above-mentioned shortcomings of the prior art, the present invention provides a method for preparing a photonic crystal, comprising: Step 1: taking a seed crystal and etching on one side of the seed crystal to form a seed crystal having a submicron gap on the surface; 2: taking a graphite disk, coating graphite glue on one side of the graphite disk, and attaching the seed having the submicron gap to the graphite disk by the graphite glue to form a seed crystal seat; Step 3: Positioning the seed crystal holder above a growth chamber, placing the raw material below the growth chamber; Step 4: forming a thermal field inside the growth chamber by a heating device, and controlling the thermal field, so that the a seed holder located at a relatively cold end of the thermal field and having the material at a relatively hot end of the thermal field, thereby sublimating the material from a solid to a gas molecule; and step 5: controlling the temperature, thermal field, The atmosphere and pressure cause the gas molecules to be transported and deposited on the seed crystal, thereby forming a photonic crystal; during the step 5, the submicron voids form a local high temperature, and the crystals at the bottom of the submicron void are formed. Sublimated into gas molecules, gas molecules are formed, thereby increase the depth of the sub-micron gap, then the sub-micron-based gas molecules in the crystalline voids on the surface of the graphite plastic, thereby closing the gap sub-micron, submicron holes is formed.

In the above preparation method, in step 1-5, the photonic crystal prepared in the previous step 1-5 is used as a seed crystal, thereby forming a photonic crystal having a multi-layer micron hole. .

The above preparation method, wherein the seed crystal and the raw material are wide energy gap materials.

The above preparation method, wherein the wide gap material is tantalum carbide, gallium nitride or aluminum nitride.

The above preparation method, wherein the wide gap material is tantalum carbide.

In the above preparation method, the surface of the tantalum carbide is a kneading surface.

In the above preparation method, the depth of the submicron void formed by etching in the step 1 is greater than 500 μm.

The above preparation method, wherein the graphite gel system further comprises a doping element, in the process of performing step 5, the doping element is evaporated and diffused into the submicron void, and deposited in the submicron void, so that The doping element is eventually coated within the submicron hole.

The above preparation method, wherein the doping element is carbon.

The above preparation method, wherein the doping element is a metal element.

The present invention uses a seed crystal having a submicron void on the surface and a physical vapor phase transport system to grow a wide band gap single crystal crystal, and air or a specific metal element can be periodically coated inside the wide band gap crystal to form a photonic crystal.

A method for preparing a photonic crystal of the present invention is characterized in that a seed crystal having a submicron void on the surface is used, thereby causing a difference in temperature gradient, and the crystal at the bottom of the submicron void is sublimated into a gas molecule, thereby deepening the submicron void. The depth, then, the gas molecules in the submicron voids crystallize on the surface of the graphite gel, causing the seed crystal to gradually coat the doping elements or form holes in the crystal growth process, thereby forming a two-dimensional or even three-dimensional photonic crystal.

Compared with the prior art, a photonic crystal preparation method of the present invention can use a wide energy gap material to prepare a photonic crystal, and the photonic crystal prepared by the wide energy gap material has a higher refractive index characteristic. Large photonic band gap.

In order to fully understand the objects, features and effects of the present invention, the present invention will be described in detail by the following specific embodiments.

Example 1

Example 1 prepares a photonic crystal having a single-layer micron hole by the following steps:

Step 1: A seed crystal is taken and etched on one side of the seed crystal to form a seed crystal having a submicron void on the surface.

In Example 1, the seed crystal is niobium carbide, but the present invention is not limited thereto. The seed crystal can also be other wide bandgap materials such as aluminum nitride or gallium nitride. In the case where lanthanum carbide is used as the seed crystal, preferably, the surface of the seed crystal is a kneading surface.

In step 1, one side of the seed crystal can be provided with a submicron pattern of submicron voids by etching.

In the step 1, the depth of the submicron void is 500 μm, but the present invention is not limited thereto. Preferably, the submicron void has a depth greater than 500 μm.

Step 2: taking a graphite disk, coating graphite glue on one side of the graphite disk, and attaching the seed having a submicron gap to the graphite disk by the graphite glue to form a seed crystal seat.

The seed crystal holder prepared by the step 2 is as shown in FIG. 1 , wherein the seed crystal holder 110 comprises: a graphite disc 111; a graphite glue 112 coated on one side of the graphite disc 111; and a surface A seed crystal 114 having a submicron void 113, wherein the submicron void 113 is between the graphite paste 112 and the seed crystal 114.

Step 3: The seed holder is placed above a growth chamber, and the raw material is placed below the growth chamber.

As shown in FIG. 2, the seed holder 110 is placed above a growth chamber 120, and the material 121 is placed below the growth chamber 120. A heating device 122 is disposed around the growth chamber 120. The heating device 122 is used to form a thermal field inside the growth chamber in a subsequent step.

In the first embodiment, the raw material is tantalum carbide, but the present invention is not limited thereto. The material may also be other wide bandgap materials such as aluminum nitride or gallium nitride.

Step 4: forming a thermal field inside the growth chamber by a heating device, and controlling the thermal field so that the seed holder is located at a relatively cold end of the thermal field, and the material is located at a relatively hot end of the thermal field. Thereby, the raw material is sublimated from a solid to a gas molecule.

Step 5: controlling the temperature, the thermal field, the atmosphere and the pressure in the growth chamber, causing the gas molecules to be transported and deposited on the seed crystal, thereby forming a photonic crystal; during the step 5, the submicron void is Forming a local high temperature, sublimating the crystal at the bottom of the submicron void into gas molecules, thereby deepening the depth of the submicron void, and then, the gas molecules in the submicron void are crystallized on the surface of the graphite gel, thereby closing the time Micron voids form submicron pores.

As shown in FIG. 3, during the step 5, the submicron void 113 forms a local high temperature, and the crystal at the bottom of the submicron void is sublimated into gas molecules, thereby deepening the depth of the submicron void 113.

As shown in FIG. 4, subsequently, the gas molecules in the submicron voids are crystallized on the graphite paste 112, thereby blocking the submicron voids to form submicron pores 141.

In Example 1, the temperature in the growth chamber was controlled to be 2100-2200 ° C; the atmosphere was Ar/N ₂ ; and the pressure was 1-5 torr. However, the present invention is not limited thereto, and those having ordinary knowledge in the technical field of the present invention can control the temperature, the heat field, and the atmosphere in the growth chamber according to factors such as the seed crystal used and the material of the raw material and the desired deposition rate. And pressure in the appropriate range.

Example 2

Example 2 prepares a photonic crystal having two-layer micropores by the following steps:

Step 1: The photonic crystal prepared in Example 1 was taken as a seed crystal, and etching was performed on one side of the seed crystal to form a seed crystal having a submicron void on the surface.

In Example 2, the seed crystal is niobium carbide, but the present invention is not limited thereto. The seed crystal can also be other wide bandgap materials such as aluminum nitride or gallium nitride. In the case where lanthanum carbide is used as the seed crystal, preferably, the surface of the seed crystal is a kneading surface.

In step 1, one side of the seed crystal can be provided with a submicron pattern of submicron voids by etching.

In the step 1, the depth of the submicron void is 500 μm, but the present invention is not limited thereto. Preferably, the submicron void has a depth greater than 500 μm.

Step 2: taking a graphite disk, coating graphite glue on one side of the graphite disk, and attaching the seed having a submicron gap to the graphite disk by the graphite glue to form a seed crystal seat.

The seed crystal holder prepared by the step 2 is as shown in FIG. 5, wherein the seed crystal holder 210 comprises: a graphite plate 211; a graphite glue 212 coated on one side of the graphite disk 211; and a surface A seed crystal 214 having a submicron void 213 and having a first layer of micropores 241 therein, wherein the submicron void 213 is between the graphite paste 212 and the seed crystal 214.

Step 3: The seed holder is placed above a growth chamber, and the raw material is placed below the growth chamber.

The growth chamber used in Example 2 and the arrangement of the seed crystal holder and the raw material in the growth chamber were the same as in Example 1.

In the embodiment 2, the raw material is tantalum carbide, but the invention is not limited thereto. The material may also be other wide bandgap materials such as aluminum nitride or gallium nitride.

Step 4: forming a thermal field inside the growth chamber by a heating device, and controlling the thermal field so that the seed holder is located at a relatively cold end of the thermal field, and the material is located at a relatively hot end of the thermal field. Thereby, the raw material is sublimated from a solid to a gas molecule.

Step 5: controlling the temperature, the thermal field, the atmosphere and the pressure in the growth chamber, causing the gas molecules to be transported and deposited on the seed crystal, thereby forming a photonic crystal; during the step 5, the submicron void is Forming a local high temperature, sublimating the crystal at the bottom of the submicron void into gas molecules, thereby deepening the depth of the submicron void, and then, the gas molecules in the submicron void are crystallized on the surface of the graphite gel, thereby closing the time Micron voids form a second level of microscopic pores.

As shown in FIG. 6, during the step 5, the submicron voids 213 form a local high temperature, and the crystals at the bottom of the submicron voids are sublimated into gas molecules, thereby deepening the depth of the submicron voids 213.

As shown in FIG. 7, subsequently, the gas molecules in the submicron voids are crystallized on the graphite paste 212, thereby closing the submicron voids to form second layer micropores 242.

In Example 2, the temperature in the growth chamber was controlled to be 2100-2200 ° C; the atmosphere was Ar/N ₂ ; and the pressure was 1-5 torr. However, the present invention is not limited thereto, and those having ordinary knowledge in the technical field of the present invention can control the temperature, the heat field, and the atmosphere in the growth chamber according to factors such as the seed crystal used and the material of the raw material and the desired deposition rate. And pressure in the appropriate range.

Example 2 Using the photonic crystal prepared in Example 1 as a seed crystal, the steps 1-5 described in Example 1 were repeated to prepare a photonic crystal having a two-layer micron hole. However, the present invention is not limited thereto, and steps 1-5 may be further repeated a plurality of times. In the repetition process, the photonic crystal prepared in the previous step 1-5 is used as a seed crystal, thereby forming a multi-layer micron hole. The photonic crystals are obtained to obtain a complete two-dimensional or even three-dimensional photonic crystal structure.

Example 3

Example 3 is to prepare a photonic crystal having a 1-layer micron hole and a doping element in the hole by the following steps:

Step 1: A seed crystal is taken and etched on one side of the seed crystal to form a seed crystal having a submicron void on the surface.

In Example 3, the seed crystal is niobium carbide, but the present invention is not limited thereto. The seed crystal can also be other wide bandgap materials such as aluminum nitride or gallium nitride. In the case where lanthanum carbide is used as the seed crystal, preferably, the surface of the seed crystal is a kneading surface.

In step 1, one side of the seed crystal can be provided with a submicron pattern of submicron voids by etching.

In the step 1, the depth of the submicron void is 500 μm, but the present invention is not limited thereto. Preferably, the submicron void has a depth greater than 500 μm.

Step 2: taking a graphite disk, coating a graphite paste containing a doping element on one side of the graphite disk, and attaching the seed having a submicron gap to the graphite disk by the graphite glue to form a crystal Planting. Compared to Example 1, the graphite gum of Example 3 further comprises a doping element.

In Embodiment 3, the doping element is carbon, but the present invention is not limited thereto. The doping element can also be a metal element.

The seed crystal holder prepared by the step 2 is as shown in FIG. 8 , wherein the seed crystal holder 310 comprises: a graphite disc 311; a graphite glue 312 coated on one side of the graphite disc 311, the graphite paste 312 A doping element 343 is included therein; and a seed 314 having a submicron void 313 on the surface, wherein the submicron void 313 is between the graphite paste 312 and the seed crystal 314.

Step 3: The seed holder is placed above a growth chamber, and the raw material is placed below the growth chamber.

The growth chamber used in Example 3 and the arrangement of the seed crystal holder and the raw material in the growth chamber were the same as in Example 1.

In Example 3, the raw material is cerium carbide, but the present invention is not limited thereto. The material may also be other wide bandgap materials such as aluminum nitride or gallium nitride.

Step 4: forming a thermal field inside the growth chamber by a heating device, and controlling the thermal field so that the seed holder is located at a relatively cold end of the thermal field, and the material is located at a relatively hot end of the thermal field. Thereby, the raw material is sublimated from a solid to a gas molecule.

Step 5: controlling the temperature, the thermal field, the atmosphere and the pressure in the growth chamber, causing the gas molecules to be transported and deposited on the seed crystal, thereby forming a photonic crystal; during the step 5, the submicron void is Forming a local high temperature, sublimating the crystal at the bottom of the submicron void into gas molecules, thereby deepening the depth of the submicron void, and then, the gas molecules in the submicron void are crystallized on the surface of the graphite gel, thereby closing the time a micron void, forming a submicron hole; and, during the performing step 5, the doping element is evaporated and diffused into the submicron void, and deposited in the submicron void, so that the doping element is finally coated Within the micron hole.

As shown in FIG. 9, during the step 5, the sub-micron voids 313 form a local high temperature, and the crystals at the bottom of the sub-micron voids are sublimated into gas molecules, thereby deepening the depth of the sub-micron voids 313. At the same time, the doping element 343 is evaporated and diffused into the submicron voids 313.

As shown in FIG. 10, subsequently, the gas molecules in the submicron voids are crystallized on the graphite paste 312, thereby blocking the submicron voids to form submicron pores 341, and the doping element 343 is deposited on the submicron. In the gap, it is finally covered within the submicron hole 341.

In Example 3, the temperature in the growth chamber was controlled to be 2100-2200 ° C; the atmosphere was Ar/N ₂ ; and the pressure was 1-5 torr. However, the present invention is not limited thereto, and those having ordinary knowledge in the technical field of the present invention can control the temperature, the heat field, and the atmosphere in the growth chamber according to factors such as the seed crystal used and the material of the raw material and the desired deposition rate. And pressure in the appropriate range.

The method for preparing a photonic crystal of the present invention, in the process of performing step 5, because the submicron void has a lower thermal conductivity than the surrounding crystalline material, so that the thermal conductivity of the side having the submicron void in the seed crystal, It varies with the submicron pattern formed by the submicron voids. In this seed crystal, the submicron void has a higher temperature due to poor thermal conductivity. During the course of step 5, the local high temperature at the submicron voids causes the crystals at the bottom of the submicron void to sublime into gas molecules, thereby deepening the depth of the submicron void. Subsequently, in the submicron void, gas molecules near the graphite gel crystallize on the surface of the graphite gel due to a gradual decrease in temperature, thereby closing the submicron void to form submicron pores.

The present invention further analyzes the temperature change of the seed crystal having the submicron void on the surface of the present invention after heating by the heat field in the growth chamber by thermal simulation. Using the same method, the seed crystals having no submicron voids on the surface were analyzed, and the temperature change after heating in the heating field in the growth chamber was used as a control.

Figure 11 is a isotherm simulation of the seed crystal having submicron voids on the surface of the present invention. It can be seen from Figure 11 that after the seed crystal is heated by the thermal field in the growth chamber, the temperature near the submicron void is slightly higher than the temperature of the adjacent crystal. In Fig. 11, the higher the height of the isotherm, the more uneven the temperature distribution of the region, so that if there is a periodic submicron gap at the junction of the seed crystal and the graphite glue, there will be a comparison. Significant temperature changes. From Fig. 11, it can be explained that during the step 5 of the present invention, the submicron void region has a temperature difference from the adjacent crystal region. The present invention utilizes this temperature difference to cause the seed crystal to form submicron pores inside during the step 5, and to further coat the doping element in the submicron pore.

Figure 12 is an isotherm simulation of a seed crystal having no submicron voids on its surface. As can be seen from Fig. 11 and Fig. 12, the isotherm near the surface of the seed crystal of Fig. 12 is relatively flat compared to Fig. 11, showing that the surface temperature does not change significantly when the surface of the seed crystal does not have submicron voids.

The invention has been described above in terms of the preferred embodiments, and it should be understood by those skilled in the art that the present invention is not intended to limit the scope of the invention. It should be noted that variations and permutations equivalent to those of the embodiments are intended to be included within the scope of the present invention. Therefore, the scope of protection of the present invention is defined by the scope of the patent application.

110‧‧‧ seed seat
111‧‧‧ Graphite disk
112‧‧‧Graphite
113‧‧‧ micron voids
114‧‧‧ seed crystal
120‧‧‧ Growth room
121‧‧‧Materials
122‧‧‧ heating device
141‧‧1 micron holes
210‧‧‧ Seed seat
211‧‧‧ Graphite disk
212‧‧‧Graphite
213‧‧‧ micron voids
214‧‧‧ seed crystal
241‧‧‧First level micron holes
242‧‧‧Second level micron holes
310‧‧‧ seed seat
311‧‧‧ Graphite disk
312‧‧‧Graphite
313‧‧ ‧ micron void
314‧‧‧ seed crystal
341‧‧1 micron holes
343‧‧‧Doped elements

Fig. 1 is a schematic view showing a seed crystal holder of Example 1 of the present invention. Fig. 2 is a schematic view showing a growth chamber of the first embodiment of the present invention. 3 is a schematic view showing the photonic crystal of Embodiment 1 of the present invention in the process of performing Step 5. 4 is a schematic view showing the photonic crystal of Embodiment 1 of the present invention in the process of performing Step 5. Fig. 5 is a schematic view showing a seed crystal holder of Example 2 of the present invention. 6 is a schematic view showing the photonic crystal of Embodiment 2 of the present invention in the process of performing Step 5. FIG. 7 is a schematic view showing the photonic crystal of Embodiment 2 of the present invention in the process of performing Step 5. Fig. 8 is a schematic view showing a seed crystal holder of Example 3 of the present invention. 9 is a schematic view showing the photonic crystal of Embodiment 3 of the present invention in the process of performing Step 5. FIG. 10 is a schematic view showing the photonic crystal of Embodiment 3 of the present invention in the process of performing Step 5. Fig. 11 is an isotherm simulation diagram of a seed crystal having a submicron void on the surface of the present invention. [Fig. 12] is an isotherm simulation diagram of a seed crystal having no submicron voids on its surface.

110‧‧‧ seed seat

111‧‧‧ Graphite disk

112‧‧‧Graphite

113‧‧‧ micron voids

114‧‧‧ seed crystal

Claims (10)

A method for preparing a photonic crystal, comprising: Step 1: taking a seed crystal, etching on one side of the seed crystal to form a seed crystal having a submicron gap on the surface; Step 2: taking a graphite disk, and taking the graphite disk Graphite glue is coated on one side, and the side of the seed crystal having the submicron gap is attached to the graphite disk by the graphite glue to form a seed crystal seat; Step 3: placing the seed crystal seat above a growth chamber And placing the raw material under the growth chamber; Step 4: forming a thermal field inside the growth chamber by a heating device, and controlling the thermal field so that the seed crystal seat is located at a relatively cold end of the thermal field, And placing the material at a relatively hot end of the thermal field, thereby sublimating the material from a solid to a gas molecule; and step 5: controlling the temperature, thermal field, atmosphere, and pressure within the growth chamber to cause the gas molecule to be transported and deposited The seed crystal, thereby forming a photonic crystal; during the step 5, the submicron void forms a local high temperature, and the crystal at the bottom of the submicron void is sublimated into gas molecules, thereby deepening the submicron void Depth, then, the sub-micron-based gas molecules in the crystalline voids on the surface of the graphite plastic, thereby closing the gap sub-micron, submicron holes is formed. The preparation method according to claim 1, wherein the step 1-5 is further repeated a plurality of times, and in the repeating process, the photonic crystal prepared in the previous step 1-5 is used as a seed crystal, thereby forming a multi-layer Photonic crystals of micron holes. The preparation method according to claim 1, wherein the seed crystal and the raw material are wide energy gap materials. The preparation method according to claim 3, wherein the wide gap material is tantalum carbide, gallium nitride or aluminum nitride. The preparation method of claim 4, wherein the wide gap material is tantalum carbide. The preparation method according to claim 5, wherein the surface of the tantalum carbide is a kneading surface. The preparation method according to claim 1, wherein the depth of the submicron void formed by etching in the step 1 is greater than 500 μm. The preparation method according to claim 1, wherein the graphite gel system further comprises a doping element, and during the performing step 5, the doping element is evaporated and diffused to the submicron void, and deposited in the submicron. In the void, the doping element is finally coated within the submicron pore. The preparation method of claim 8, wherein the doping element is carbon. The preparation method according to claim 8, wherein the doping element is a metal element.