KR102263263B1 - HIGH SURFACE AREA GaN PHOTOELECTRODE FOR WATER DECOMPOSITION AND METHOD OF MANUFACTURING THE SAME - Google Patents

Abstract

Disclosed is a GaN photo-electrode having a high specific surface area for water decomposition and a method of manufacturing the same, which can form a plurality of GaN nanopillars with porosity by applying two steps of electrochemical etching and physical etching and can improve the efficiency of the photo-electrode by securing a larger specific surface area by attaching a co-photocatalyst. A method of manufacturing a GaN photo-electrode having a high specific surface area for water decomposition includes: (a) preparing a substrate on which a GaN thin film layer is formed; (b) forming a nanoporous GaN thin film layer by wet etching the GaN thin film layer formed on the substrate; (c) forming an insulating layer on the nanoporous GaN thin film layer; (d) depositing a metal material on the insulating layer to form a metal thin film, then annealing the metal thin film to form a plurality of metal nano mask patterns arranged spaced apart from each other at regular intervals; (e) forming a plurality of GaN nanopillars by dry etching the insulating layer and the nanoporous GaN thin film layer exposed by the metal nano mask pattern; (f) removing the insulating layer and the metal nano mask pattern from the plurality of GaN nanopillars; and (g) attaching a photocatalyst to the plurality of GaN nanopillars.

Description

HIGH SURFACE AREA GaN PHOTOELECTRODE FOR WATER DECOMPOSITION AND METHOD OF MANUFACTURING THE SAME

The present invention relates to a high specific surface area GaN porous photoelectrode for water decomposition and a method for manufacturing the same, and more particularly, to a plurality of porous photoelectrodes having porosity by applying two steps of an electrochemical etching method (EC etching) and a physical etching method A high specific surface area GaN porous photoelectrode for water decomposition, which can improve the efficiency of a photoelectrode by securing a larger specific surface area by forming GaN nanopillars and attaching a photocatalyst, and a method for manufacturing the same will be.

Since the existing fossil fuel-based energy system causes problems such as global warming, environmental pollution, and resource depletion, the so-called hydrogen economy has been proposed as an alternative.

The hydrogen economy is the use of hydrogen fuel as an energy carrier instead of conventional fossil fuels. One of the most fundamental and key problems to realize this is to economically produce hydrogen fuel without emitting greenhouse gases or pollutants.

The photoelectrochemical hydrogen production method, which has recently been the subject of worldwide interest and research, illuminates the interface between a semiconductor and an electrolyte to perform water decomposition at the interface, where the semiconductor/electrolyte interface absorbs photons. It plays a key role in converting energy into chemical energy, that is, hydrogen fuel.

A variety of semiconductor materials, also called photoelectrodes, are being studied, from single crystal materials such as Si and GaAs to _{metal oxides such as TiO 2 .} Numerous studies have been conducted since it was shown that hydrogen generation is possible when light is irradiated to the TiO _{2 electrode. However, in order to realize a practical device, two major problems need to be solved.}

First, it is necessary to increase the energy conversion efficiency of the photoelectrode. In photoelectrochemical hydrogen production using sunlight, energy conversion efficiency is directly related to the energy band gap of semiconductor materials. Currently, most metal oxide materials (TiO ₂ , ZnO, etc.) have a very large energy band gap, so they absorb only photons in the ultraviolet region of the solar spectrum and do not absorb light in other regions. .

On the other hand, semiconductor materials having a low to mid band gap, such as Si and GaAs, have a band gap between 1.0 and 1.5 eV, so they can absorb most of the light from infrared to ultraviolet.

However, in order to cause water decomposition without external voltage supply, a photovoltage of 1.5 V or more is required. In general, the photovoltage exhibited by these photoelectrodes is considerably smaller than this. That is, a dilemma arises in the selection of the energy band interval of the photoelectrode.

Second, the reliability of the photoelectrode is also an important issue. Considering that the lifespan required for a typical utility scale solar cell is 15 to 20 years, ultimately, the operating life of the solar hydrogen generator should be comparable to this.

However, in general, a semiconductor electrode is a corrosive material, and since it is continuously irradiated with sunlight in a strong acid or strong basic electrolyte, it is a very challenging situation to achieve a required lifespan.

A variety of photoelectrode materials have been developed to solve the key problem for photoelectrochemical hydrogen production.

To this end, recently, gallium nitride photoelectrodes for photoelectrochemical water decomposition using sunlight have been developed, and these gallium nitride photoelectrodes for water decomposition are mostly produced in the form of films and used for hydrogen production.

However, the conventional gallium nitride photoelectrode for water decomposition is formed in a porous GaN structure through electrochemical etching, but in this case, additional photocatalyst is applied to the surface. there was.

In other words, when using electrochemical etching to fabricate a porous hole with a diameter of about 50 nm, the surface area can have a surface area several times that of a thin film, but when a photocatalyst of 50 nm or more is used, it is applied only to the surface and the meaning of producing a porous structure is half became

As a related prior document, there is Korean Patent Application Laid-Open No. 10-2013-0109717 (published on Oct. 8, 2013), which describes a platinum-gallium oxide nanowire, a manufacturing method thereof, and a gas sensor using the same.

An object of the present invention is to form a plurality of GaN nanopillars having porosity by applying two steps of an electrochemical etching method (EC etching) and a physical etching method, and attaching a photocatalyst (co-photocatalyst), An object of the present invention is to provide a high specific surface area GaN porous photoelectrode for water decomposition capable of improving the efficiency of the photoelectrode by securing a larger specific surface area, and a method for manufacturing the same.

A method for manufacturing a high specific surface area GaN porous photoelectrode for water decomposition according to an embodiment of the present invention for achieving the above object includes the steps of: (a) preparing a substrate on which a GaN thin film layer is formed; (b) forming a nanoporous GaN thin film layer by wet etching the GaN thin film layer on the substrate; (c) forming an insulating layer on the nanoporous GaN thin film layer; (d) depositing a metal material on the insulating layer to form a metal thin film, then annealing the metal thin film to form a plurality of metal nano mask patterns spaced apart from each other at regular intervals; (e) forming a plurality of GaN nanopillars by dry etching the insulating layer and the nanoporous GaN thin film layer exposed by the metal nanomask pattern; (f) removing the insulating layer and the metal nanomask pattern on the plurality of GaN nanopillars; and (g) attaching a photocatalyst to the plurality of GaN nanopillars.

In step (a), the substrate is silicon (Si), sapphire (sapphire), glass, silicon carbide (SiC), gallium oxide (Ga ₂ O ₃ ), GaN is deposited sapphire (GaN on Sapphire), InGaN and any one of deposited sapphire (InGaN on sapphire, AlGaN on sapphire) and AlN deposited sapphire (AlN on sapphire).

In step (b), the wet etching is performed by an electrochemical etching (EC) method.

In addition, in step (c), the insulating layer is _{made of a SiO 2} material, and is formed to a thickness of 10 ~ 200nm.

In step (d), the metal thin film may be formed of Ni, Ag, Au. It is formed by depositing at least one metal material selected from Al, Cu, Mo, Ti, and Cr.

The metal thin film is preferably formed to a thickness of 10 to 50 nm.

In addition, in step (d), the annealing treatment is performed for 1 to 60 minutes as the sum of the annealing start temperature and the annealing end temperature under the conditions of an annealing start temperature of 400 to 550° C. and an annealing end temperature of 600 to 800° C.

Here, in the annealing process, the temperature is gradually increased from the annealing start temperature to the annealing end temperature at a rate of 10 to 80° C./sec.

In step (e), each of the plurality of GaN nanopillars may have the same diameter as the plurality of metal nanomask patterns.

In step (f), the insulating layer and the metal nanomask pattern are removed by wet etching using a buffered oxide etchant (BOE) etchant.

In step (g), the photocatalyst may include at least one material selected from among RhO, CrO, ZnS, NiO, CdS, and TiO.

A high specific surface area GaN porous photoelectrode for water decomposition according to an embodiment of the present invention for achieving the above object includes: a substrate; a plurality of GaN nanopillars spaced apart from each other on the substrate; and a photocatalyst attached to the surface of the plurality of GaN nanopillars.

Here, each of the plurality of GaN nanopillars has a shape of any one of polygons including a triangle, a quadrangle, a pentagon, a hexagon, and an octagon when viewed in a plan view.

The photocatalyst may include at least one material selected from RhO, CrO, ZnS, NiO, CdS, and TiO.

In addition, the photocatalyst may be randomly attached to the exposed side wall and upper surface of the plurality of GaN nanopillars.

A high specific surface area GaN porous photoelectrode for water decomposition according to the present invention and a method for manufacturing the same are obtained by applying two-step etching of wet etching using electrochemical etching (EC etching) and dry etching, which is physical etching. By forming GaN nanopillars, they are spaced apart from each other at regular intervals while having a porous structure to increase the area exposed to the outside.

Accordingly, the high specific surface area GaN porous photoelectrode for water decomposition and the method for manufacturing the same according to the present invention can secure a larger surface area because the plurality of GaN nanopillars have a porous structure, and the plurality of GaN nanopillars are spaced apart from each other at regular intervals. It is possible to maximize the exposure area by being spaced apart from each other, thereby improving the water decomposition efficiency of the photoelectrode.

As a result, the high specific surface area GaN porous photoelectrode for water decomposition and the method for manufacturing the same according to the present invention are porous GaN nanopillars manufactured by applying electrochemical etching (EC) and physical etching in two steps. has a structural advantage of maximizing the water decomposition efficiency of a photoelectrode for water decomposition because it can apply various photocatalysts over the entire area with a larger surface area than when simply grafting one etching method. .

1 to 6 are process perspective views illustrating a method for manufacturing a high specific surface area GaN porous photoelectrode for water decomposition according to an embodiment of the present invention.
7 to 12 are cross-sectional views illustrating a method for manufacturing a high specific surface area GaN porous photoelectrode for water decomposition according to an embodiment of the present invention.

Advantages and features of the present invention, and methods for achieving them, will become apparent with reference to the embodiments described below in detail in conjunction with the accompanying drawings. However, the present invention is not limited to the embodiments disclosed below, but will be embodied in various different forms, only this embodiment allows the disclosure of the present invention to be complete, and common knowledge in the technical field to which the present invention belongs It is provided to fully inform the possessor of the scope of the invention, and the present invention is only defined by the scope of the claims. Like reference numerals refer to like elements throughout.

Hereinafter, a high specific surface area GaN porous photoelectrode for water decomposition and a method for manufacturing the same according to a preferred embodiment of the present invention will be described in detail with reference to the accompanying drawings.

Method for manufacturing high specific surface area GaN porous photoelectrode for water decomposition

1 to 6 are process perspective views illustrating a method for manufacturing a high specific surface area GaN porous photoelectrode for water decomposition according to an embodiment of the present invention, and FIGS. 7 to 12 are high specific surface area GaN porosity for water decomposition according to an embodiment of the present invention. It is a process cross-sectional view showing the photoelectrode manufacturing method.

As shown in FIGS. 1 and 7 , the substrate 110 on which the GaN thin film layer 120 is formed is prepared.

Here, the substrate 110 may have a plate shape having one surface and the other surface opposite to the one surface, but this is exemplary and the shape may be variously changed.

As the substrate 110, silicon (Si), sapphire (sapphire), glass, silicon carbide (SiC), gallium oxide (Ga ₂ O ₃ ), GaN-deposited sapphire (GaN on Sapphire), InGaN-deposited sapphire ( It may include any one of InGaN on sapphire, AlGaN-deposited sapphire (AlGaN on sapphire), and AlN-deposited sapphire (AlN on sapphire).

Next, as shown in FIGS. 2 and 8 , the GaN thin film layer ( 120 in FIG. 1 ) on the substrate 110 is wet-etched to form the nanoporous GaN thin film layer 125 .

In this step, the wet etching is preferably performed by an electrochemical etching (EC) method.

By using such electrochemical etching, it is possible to form the nanoporous GaN thin film layer 125 having porous holes having an average diameter of 10 to 60 nm. Accordingly, the nanoporous GaN thin film layer 125 has a surface area several times larger than that of the GaN thin film layer.

3 and 9 , an insulating layer 130 is formed on the nanoporous GaN thin film layer 125 .

The insulating layer 130 is preferably formed to a thickness of 10 to 200 nm using a PECVD method. Here, it is preferable to use a material that can be selectively removed for the insulating layer 130 . To this end, the insulating layer 130 may be made of a material capable of wet etching. Specifically, the insulating layer 130 is preferably made _{of a SiO 2 material.}

Next, as shown in FIGS. 4 and 10 , a metal thin film is formed by depositing a metal material on the insulating layer 130 , and then the metal thin film is annealed to form a plurality of metal nanomasks spaced apart from each other at regular intervals. A pattern 140 is formed.

Here, the metal thin film is formed of Ni, Ag, Au. It may be formed by depositing at least one metal material selected from Al, Cu, Mo, Ti, and Cr.

It is preferable to form the metal thin film to a thickness of 10 to 50 nm, and a more preferable range may be 20 to 40 nm. When the thickness of the metal thin film is less than 10 nm, there is a risk that the metal nanomask pattern 140 having a circular structure may not be properly formed during annealing treatment because the thickness is too thin. Conversely, when the thickness of the metal thin film exceeds 50 nm, it may act as a factor to increase the heat treatment temperature during annealing treatment due to excessive thickness design, thereby increasing the manufacturing cost.

In this step, the annealing treatment is performed in a state in which the substrate 110 on which the metal thin film is formed is put into a rapid thermal annealing furnace, which is a high temperature heat treatment furnace. At this time, an atmosphere of at least one of nitrogen, argon, and hydrogen may be maintained in the vacuum chamber of the rapid heat treatment furnace.

By performing annealing treatment in a gas atmosphere of at least one of nitrogen, argon, and hydrogen using such a rapid heat treatment furnace, a metal thin film is rapidly melted while maintaining a uniform and uniform circular shape by surface tension at regular intervals to form a plurality of metal nanomask patterns 140 spaced apart from each other.

This annealing treatment is preferably carried out for 1 to 60 minutes as the sum of the annealing start temperature and the annealing end temperature under conditions of an annealing start temperature of 400 to 550° C. and an annealing end temperature of 600 to 800° C. In this case, it is more preferable that the annealing treatment is gradually increased in temperature from the annealing start temperature to the annealing end temperature at a rate of 10 to 80° C./sec.

In this way, by gradually increasing the temperature from the annealing start temperature to the annealing end temperature during the annealing treatment, the rate at which the metal thin film is melted can be adjusted, so that in the process of melting the metal thin film, a plurality of metal nano mask patterns 140 It may become possible to control to have these various forms. Accordingly, the plurality of metal nanomask patterns 140 may have any one shape among polygons including a triangle, a quadrangle, a pentagon, a hexagon, and an octagon when viewed in a plan view.

In this step, when the annealing end temperature is less than 600° C. or the annealing treatment time is less than 1 minute, sufficient melting is not achieved, so that a plurality of metal nanomask patterns having a circular shape may not be properly formed. Conversely, if the annealing treatment temperature exceeds 800° C. or the annealing treatment time exceeds 60 minutes, it may act as a factor of increasing only the process temperature and time without further increasing the effect, which is not economical.

As shown in FIGS. 5 and 11, the insulating layer (130 in FIG. 4) and the nanoporous GaN thin film layer (125 in FIG. 4) exposed by the metal nano mask pattern (140 in FIG. 4) are dry-etched to form a plurality of GaN nanopillars 150 are formed.

In this step, the dry etching is more preferably using an inductively coupled plasma reactive ion etching (ICP-RIE) method. By dry etching using the ICP-RIE method, only the insulating layer and the nanoporous GaN thin film layer exposed to the outside of the metal nanomask pattern are selectively removed. Accordingly, a plurality of GaN nanopillars 150 having substantially the same shape as the metal nanomask pattern are formed in the lower portion overlapping the metal nanomask pattern.

As described above, in the present invention, the plurality of GaN nanopillars 150 are porous structure by applying wet etching using electrochemical etching (EC etching) and dry etching, which is physical etching. It is possible to form a plurality of GaN nanopillars 150 that are spaced apart from each other at regular intervals and exposed to the outside while having .

Accordingly, since the plurality of GaN nanopillars 150 have a porous structure, it is possible to secure a larger surface area, and they are spaced apart from each other at regular intervals to maximize the exposed area, thereby improving the water decomposition efficiency of the photoelectrode. It has structural advantages.

Next, the insulating layer and the metal nanomask pattern on the plurality of GaN nanopillars 150 are removed.

In this step, the insulating layer and the metal nano mask pattern are removed by wet etching using a buffered oxide etchant (BOE) etchant.

As described above, the plurality of GaN nanopillars 150 on the substrate 110 are exposed to the outside by the removal of the insulating layer and the metal nanomask pattern.

Next, as shown in FIGS. 6 and 12 , a photocatalyst 160 is attached to the plurality of GaN nanopillars 150 .

The photocatalyst 160 may be formed by deposition or coating. Here, the photocatalyst 160 may include at least one material selected from RhO, CrO, ZnS, NiO, CdS, and TiO.

As described above, the method for manufacturing a high specific surface area GaN porous photoelectrode for water decomposition according to an embodiment of the present invention may be completed.

A high specific surface area GaN porous photoelectrode for water decomposition manufactured by the method according to an embodiment of the present invention includes a substrate, a plurality of GaN nanopillars spaced apart from each other at regular intervals on the substrate, and a plurality of GaN nanopillars attached to the surface. It contains a photocatalyst.

In this case, each of the plurality of GaN nanopillars may have a shape of any one of polygons including a triangle, a quadrangle, a pentagon, a hexagon, and an octagon when viewed in a plan view.

Here, the photocatalyst may be randomly attached to the exposed side wall and upper surface of the plurality of GaN nanopillars. Such a photocatalyst includes at least one material selected from RhO, CrO, ZnS, NiO, CdS, and TiO.

As described so far, the high specific surface area GaN porous photoelectrode for water decomposition according to an embodiment of the present invention and a method for manufacturing the same according to an embodiment of the present invention include wet etching using electrochemical etching (EC etching) and dry etching, which is physical etching. By forming a plurality of GaN nanopillars by applying two-step etching of

Accordingly, in the high specific surface area GaN porous photoelectrode for water decomposition and the method for manufacturing the same according to an embodiment of the present invention, a larger surface area can be secured because a plurality of GaN nanopillars have a porous structure, and the plurality of GaN nanopillars are mutually exclusive. Since the exposed area can be maximized by being spaced apart from each other at regular intervals, the water decomposition efficiency of the photoelectrode can be improved.

As a result, the high specific surface area GaN porous photoelectrode for water decomposition and the method for manufacturing the same according to the embodiment of the present invention were produced by applying electrochemical etching (EC) and physical etching in two steps. GaN nanopillars have a larger surface area and can apply various photocatalysts over the entire area than when simply grafting one etching method, so it is possible to maximize the water decomposition efficiency of the photoelectrode for water decomposition. have an advantage

In the above, the embodiments of the present invention have been mainly described, but various changes or modifications can be made at the level of those skilled in the art to which the present invention pertains. Such changes and modifications can be said to belong to the present invention as long as they do not depart from the scope of the technical spirit provided by the present invention. Accordingly, the scope of the present invention should be judged by the claims described below.

110: substrate 120: GaN thin film layer
125: nanoporous GaN thin film layer 130: insulating layer
140: metal nanomask pattern 150: GaN nanopillars
160: photocatalyst

Claims (15)

(a) preparing a substrate on which a GaN thin film layer is formed;
(b) forming a nanoporous GaN thin film layer by wet etching the GaN thin film layer on the substrate;
(c) forming an insulating layer on the nanoporous GaN thin film layer;
(d) depositing a metal material on the insulating layer to form a metal thin film, then annealing the metal thin film to form a plurality of metal nano mask patterns spaced apart from each other at regular intervals;
(e) forming a plurality of GaN nanopillars by dry etching the insulating layer and the nanoporous GaN thin film layer exposed by the metal nanomask pattern;
(f) removing the insulating layer and the metal nanomask pattern on the plurality of GaN nanopillars; and
(g) attaching a photocatalyst to the plurality of GaN nanopillars;
High specific surface area GaN porous photoelectrode manufacturing method for water decomposition, characterized in that it comprises a.
According to claim 1,
In step (a),
the substrate is
Silicon (Si), sapphire (sapphire), glass, silicon carbide (SiC), gallium oxide (Ga ₂ O ₃ ), GaN-deposited sapphire (GaN on Sapphire), InGaN-deposited sapphire (InGaN on sapphire, AlGaN) A method for manufacturing a high specific surface area GaN porous photoelectrode for water decomposition, comprising any one of deposited sapphire (AlGaN on sapphire) and AlN deposited sapphire (AlN on sapphire).
According to claim 1,
In step (b),
The wet etching
A method for manufacturing a high specific surface area GaN porous photoelectrode for water decomposition, characterized in that it is carried out by an electrochemical etching (EC) method.
According to claim 1,
In step (c),
The insulating layer is
A high specific surface area GaN porous photoelectrode manufacturing method for water decomposition, characterized in that it is made of a SiO _{2 material and formed to a thickness of 10 to 200 nm.}
According to claim 1,
In step (d),
The metal thin film
Ni, Ag, Au by sputtering or electron-beam evaporation method. A method of manufacturing a GaN porous photoelectrode with a high specific surface area for water decomposition, characterized in that it is formed by depositing at least one metal material selected from Al, Cu, Mo, Ti and Cr.
6. The method of claim 5,
The metal thin film
A method for manufacturing a high specific surface area GaN porous photoelectrode for water decomposition, characterized in that it is formed to a thickness of 10 to 50 nm.
According to claim 1,
In step (d),
The annealing treatment is
High specific surface area GaN porous photoelectrode manufacturing method for water decomposition, characterized in that the annealing start temperature 400 ~ 550 ℃ and annealing end temperature 600 ~ 800 ℃ conditions, the annealing start temperature and the annealing end temperature is carried out for 1 ~ 60 minutes .
8. The method of claim 7,
The annealing treatment is
High specific surface area GaN porous photoelectrode manufacturing method for water decomposition, characterized in that the temperature is gradually increased at a rate of 10 ~ 80 °C / sec from the annealing start temperature to the annealing end temperature.
According to claim 1,
In step (e),
Each of the plurality of GaN nanopillars is
A method of manufacturing a high specific surface area GaN porous photoelectrode for water decomposition, characterized in that it has the same diameter as the plurality of metal nanomask patterns.
According to claim 1,
In step (f),
The insulating layer and the metal nano mask pattern
A method for manufacturing a high specific surface area GaN porous photoelectrode for water decomposition, characterized in that it is removed by wet etching using a buffered oxide etchant (BOE) etchant.
According to claim 1,
In step (g),
The photocatalyst is
A method for manufacturing a high specific surface area GaN porous photoelectrode for water decomposition, comprising at least one material selected from RhO, CrO, ZnS, NiO, CdS and TiO.
A photoelectrode prepared by the method for manufacturing a high specific surface area GaN porous photoelectrode for water decomposition according to claim 1,
Board;
a plurality of GaN nanopillars spaced apart from each other on the substrate; and
a photocatalyst attached to the surface of the plurality of GaN nanopillars;
High specific surface area GaN porous photoelectrode for water decomposition, characterized in that it comprises a.
13. The method of claim 12,
Each of the plurality of GaN nanopillars is
A GaN porous photoelectrode with a high specific surface area for water decomposition, characterized in that it has any one shape of a polygon including a triangle, a square, a pentagon, a hexagon and an octagon when viewed in a plan view.
13. The method of claim 12,
The photocatalyst is
High specific surface area GaN porous photoelectrode for water decomposition, characterized in that it contains at least one material selected from RhO, CrO, ZnS, NiO, CdS and TiO.
13. The method of claim 12,
The photocatalyst is
A high specific surface area GaN porous photoelectrode for water decomposition, characterized in that it is randomly attached to the exposed side wall and top surface of the plurality of GaN nanopillars.

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