JPH08225937A - Production of nickel oxide based electrochromic material - Google Patents

Abstract

PURPOSE: To provide a producing method of a nickel oxide based electrochromic material. CONSTITUTION: The nickel oxide based electrochromic material is produced with good reproducibility by a reactive DC magnetron sputtering method using a metallic nickel as a target. Visible ray transmissivity is freely controlled within a range from about 7% to about 82% by using this material. In this way, a transmitting sun light is controlled so that a chilling load and a lighting load are reduced as much as possible in a building and a vehicle.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a window material technology for controlling the transmittance of solar energy in buildings and vehicles, and more specifically, it controls automatically incident sunlight without blinds or curtains. The present invention relates to a novel method for producing an electrochromic thin film material.

[0002]

2. Description of the Related Art The phenomenon that color (light transmittance) reversibly changes due to external physical stimulation is called chromism. Among them, reversible color and light transmittance can be obtained by applying voltage or applying current. The phenomenon in which is changed is called electrochromism.

Historically, in 1963, Deb discovered that an amorphous thin film of tungsten oxide (WO ₃ ) which was a transition metal oxide exhibited an electrochromic phenomenon, and became well known.

Applications of practical devices using electrochromic materials are roughly divided into display devices and dimming devices, and in recent years, the application as dimming devices has been attracting attention. A light control element is used as a window material for buildings and vehicles to control the entry and exit of light and heat from the outside.
It is an element that If an electrochromic element is used as a window material, the sunlight transmittance of the window can be controlled so that the cooling and heating load of the building and the lighting load can be suppressed as much as possible, and it is possible to realize an intelligent window that does not require so-called blinds or curtains. .

There are a wide range of materials exhibiting electrochromism, from inorganic materials to organic materials, but at present, tungsten oxide (WO ₃ ) is expected to be the most practical material. Used as a chromic material, prototype products have been developed.

On the other hand, nickel oxide-based electrochromic materials are expected as next-generation chromic materials because of their low material cost and high coloring efficiency, and studies for their practical application are being conducted.

The nickel oxide-based electrochromic thin film can be formed by various methods, but from the viewpoint of little deterioration after repeated coloring and erasing of 10,000 times or more, the sputtering method is also a powerful method. Is one. Further, among the sputtering methods, the reactive DC magnetron sputtering method has an advantage that the cost of the target and the power source can be low.

However, at present, the sputtering method is not often used in actual device fabrication of nickel oxide thin film. The reason for this is that if the film formation speed is increased, a film that is severely deteriorated is formed, so that the film formation speed cannot be increased so much and that the target reacts with oxygen gas to deteriorate and a film with good reproducibility is obtained. This is because there is a drawback that it cannot be obtained.

[0009]

Under the circumstances, the inventors of the present invention have investigated in detail the dependence of various physical properties of the nickel oxide-based electrochromic thin film by the reactive DC magnetron sputtering method on the film forming conditions. The inventors have found that if the growth is carried out under a certain specific condition, the film formation rate can be increased by about an order of magnitude, and a film exhibiting extremely excellent chromic properties can be formed, compared with previously reported, and the present invention was completed. Came to do.

An object of the present invention is to produce a nickel oxide thin film having a good reproducibility, a high speed and a very good electrochromic property by using the reactive DC magnetron sputtering method.

[0011]

The present invention is directed to the production of nickel oxide films exhibiting excellent electrochromic properties by reactive magnetron sputtering, using metallic nickel as a target.

When a film is formed by the reactive sputtering method using a metal target, once the film is formed by sputtering, the target reacts with the introduced oxygen gas and is altered, so that the film grows as it is. When you do
Even if the film is grown under the same conditions, a film having different physical properties from the film obtained last time will be formed.

Therefore, in the present invention, before each growth, only the argon gas is first introduced with the shutter closed before the first stage pre-sputtering is performed to remove the altered surface layer of the target, After confirming the appearance of metallic luster, this time introducing argon and oxygen gas
Two-step pre-sputtering was performed in which the shutter was opened and film formation was started after the target was stabilized in the first step. As a result, it became possible to form a film with good reproducibility.

In reactive sputtering using metallic nickel as a target, the total pressure of argon and oxygen introduced was fixed, the introduced power and the amount of oxygen were changed, and the film formation rate was investigated. As a result, when the amount of oxygen was gradually increased with the power kept constant, the film formation rate rapidly decreased, and after that, when the amount of oxygen introduced increased from a certain amount of oxygen, the growth rate hardly changed. It was

Generally, in reactive sputtering targeting a metal such as aluminum or titanium, the growth rate gradually decreases from zero to a certain amount of oxygen, and the oxygen rapidly increases at a certain amount of oxygen. There is a tendency that the growth rate becomes slower, and thereafter the growth rate does not change much even if the oxygen amount is increased. The first region is called the metal mode, the latter region is called the compound mode, and the region that changes rapidly between them is called the transition region. When nickel is used as a target, unlike the above cases, no metal mode region is observed and the transition region is wide. In the conventionally reported growth, the growth was often performed in the compound mode, and the growth rate was not so high, but in the present invention, the growth rate can be increased to 40 nm / min by performing the growth in the transition region. I found it.

As a result of examining the structure of the grown film by X-ray diffraction, it was found that polycrystalline NiO was present in the film grown under any condition. However, crystallization was better when the substrate temperature during growth was increased.

As a result of investigating the composition of the film just after this growth by Auger electron spectroscopy, the ratio of oxygen atoms to nickel atoms was 1.25-1.4, and the films grown under any conditions contained more oxygen than the composition of NiO. It turned out that it was in a state. Since no peaks due to structures other than NiO are found in X-ray diffraction, it is highly possible that the surface and interface of NiO microcrystals are terminated by OH groups in the film formed by this sputtering. . Therefore, the chemical formula of the obtained film is supposed to be written as NiOxHy.

The electrochromic properties of the grown film were evaluated by performing cyclic voltammetry using 1N KOH as an electrolytic solution and platinum as a counter electrode. The electrochromic properties of the resulting films were found to depend strongly on the substrate temperature during growth.

When the substrate was not heated, deterioration of the film was observed after about 200 cycles. In contrast, the sample grown at a substrate temperature of 200 ° C to 300 ° C did not show very good characteristics after 100 cycles, but showed extremely good characteristics after 1000 cycles. Also, the substrate temperature is 400
When it was set at ℃, it showed almost no good electrochromic property. In addition, when the substrate temperature was the same, the method of the sample that grew fast showed good characteristics.

[0020]

EXAMPLES Next, the present invention will be specifically described based on Examples. Example 1 A nickel oxide thin film was produced by a reactive DC magnetron sputtering method using a triple magnetron sputtering apparatus. Glass coated with ITO (Indium Tin Oxide) is used as the substrate, and the diameter is used as the target.
50 mm metallic nickel was used. As the introduction gas, argon gas and oxygen gas were introduced from two systems so that the total pressure became 5 Pa. The growth rate was controlled by the flow rate of oxygen gas and the applied power. The film thickness was monitored with a quartz film thickness meter during growth, and after growth, the film thickness was also measured with an optical interferometer for calibration.

For growth, the chamber was set to 5 × 10-4
After evacuating to about Pa, with the shutter closed, first, pure argon was introduced and sputtering was performed to remove the oxidized layer on the target surface. Next, oxygen and argon were introduced to perform pre-sputtering for 5 minutes, and then the shutter was opened to grow. As mentioned above, the target surface is liable to be deteriorated in the reactive sputtering, so the pre-sputtering using only argon is important for obtaining good reproducibility.

Example 2 FIG. 1 is a three-dimensional plot of the deposition rate when metallic nickel is used as a target, as a function of the amount of oxygen introduced (ratio of oxygen to argon gas) and the introduced power.

For example, looking at the power of 60 W,
In the area where the amount of oxygen introduced is less than 30%, the growth rate decreases as the amount of oxygen introduced increases, which corresponds to the transition region. On the other hand, the growth rate does not change so much in the area larger than 30%, and this is the compound mode. In addition, nickel has almost no metal region, which is a major feature different from the case of titanium and zirconium. In addition, the amount of oxygen introduced into the compound mode tends to shift to the lower amount side as the power is lowered (the transition region is on the left side and the compound mode is on the right side with the thick solid line in the figure as a boundary).

As can be seen from this figure, when the amount of oxygen introduced is lowered and the power is increased to grow in the transition region, the growth rate can be increased by one digit or more as compared with the growth in the compound mode. I understand.

Example 3 These samples were examined for their electrochromic properties using cyclic voltammetry. Figure 2 shows the transition region (total pressure 5 Pa, oxygen flow 5
%, Power 60 W), and the relationship between the potential and current density in cyclic voltammetry for a sample grown at a substrate temperature of 200 ° C. The current density of this sample after 100 cycles was smaller than that of the sample without heating, but the current density increased up to about 800 cycles as the cycle was repeated and saturated, and became extremely large at 1000 cycles. Substrate temperature
Samples kept at 300 ° C have almost the same characteristics.

Example 4 FIG. 3 shows 1N of a sample prepared under the same conditions as in Example 3.
It shows the change in transmittance in the decolored state and the colored state in a KOH solution. The visible light transmittance at the time of erasing and at the time of coloring was calculated from this transmittance, and they were 7.7% and 82%, respectively.
%, And it can be seen that a material having extremely excellent electrochromic properties that can be controlled to any transmittance during this period is obtained.

The present invention has been described above based on the embodiments, but the present invention is not limited to the above-mentioned embodiments, and can be carried out in any manner as long as the configuration described in the claims is not changed. It goes without saying that it can be done.

[0028]

As described above, the present invention enables the nickel oxide electrochromic thin film to be formed with good reproducibility and at high speed by using the reactive magnetron sputtering method with metal nickel as the target. Is. According to the present invention, from 7% in visible light transmittance
A film with extremely good performance that can control up to 82.3% at 30 nm /
The film can be formed at a high speed of min. Such a film can control solar energy so that the cooling load and lighting load inside the building can be reduced as much as possible, and the cost can be significantly reduced.

[Brief description of drawings]

FIG. 1 shows the relationship between the film formation rate, the amount of oxygen introduced, and the power when reactive sputtering is performed using metallic nickel as a target.

[Fig. 2] Platinum was used as a counter electrode in 1N KOH solution.
The cyclic voltammogram of the nickel oxide thin film showing the best characteristics is shown.

FIG. 3 shows the change in transmittance of a nickel oxide thin film having the best characteristics in a 1N KOH solution during decoloring and coloring.

Claims (3)

[Claims] 1. A method for producing a nickel oxide-based electrochromic material, which comprises forming a film with good reproducibility by a reactive DC magnetron sputtering method. 2. The method for producing a nickel oxide-based electrochromic material according to claim 1, wherein the film is formed at a high speed by a reactive DC magnetron sputtering method. 3. The substrate temperature during the reactive sputtering is 2
The method for producing a nickel oxide-based electrochromic material according to claim 1, wherein the temperature is from 00 ° C to 300 ° C.