TWI873679B - Hydrogen sensor with nickel-doped vanadium pentoxide film and manufacturing method thereof - Google Patents

Abstract

A hydrogen gas sensor with nickel-doped vanadium pentoxide thin film and a manufacturing method thereof, the manufacturing method comprising the following steps: taking a silicon substrate and performing a heating step to form a silicon dioxide layer on the surface of the silicon substrate; using an evaporation technique to deposit a sensing electrode layer on the surface of the silicon dioxide layer; placing a vanadium pentoxide target, a nickel oxide target and the silicon substrate in a sputtering space of a sputtering device, the vanadium pentoxide target and the nickel oxide target respectively maintaining a sputtering distance of 5 cm from the silicon substrate; performing a co-sputtering treatment on the silicon substrate; The silicon substrate is maintained at an operating temperature of 100 degrees Celsius, the co-sputtering treatment time is 60 minutes, the sputtering power of the vanadium pentoxide target is controlled at 120W, the sputtering power of the nickel oxide target is controlled at 30W, and the silicon substrate is rotated to uniformly form a nickel-doped vanadium pentoxide thin film layer on the sensing electrode layer; thereby, the manufactured hydrogen sensor has a response of up to 2355.8% at 300 degrees Celsius, which is 17 times higher than that of the hydrogen sensor not doped with nickel under the same measurement conditions.

Description

Hydrogen gas sensor with nickel-doped vanadium pentoxide film and manufacturing method thereof

The present invention relates to a hydrogen gas sensor having a nickel-doped vanadium pentoxide thin film and a manufacturing method thereof, and in particular to an invention in which a thin film made of a nickel oxide target and a vanadium pentoxide target by co-sputtering is used as a hydrogen gas sensor and has a wide range of responsiveness when sensing hydrogen gas.

When detecting gas in a place, a gas sensor is used for detection. For example, in tunnels, industries, kitchens, gas stations or laboratories, any place where gas is used will be equipped with a gas sensor. Among them, dangerous gases must be monitored, such as flammable gases such as alkanes and hydrogen.

In industrial manufacturing, hydrogen is mostly used in the production of amines in the chemical industry, such as the production of synthetic fertilizers or hydrochloric acid, or in the oil refining industry, steel or glass industry, and a small part is used in the semiconductor manufacturing process.

As the world moves towards reducing carbon emissions, hydrogen is also being used as energy. Hydrogen can be burned to generate energy and used as a power supply or heat source. It can also be used as an energy carrier to store energy generated in other forms.

However, since hydrogen is a colorless, odorless gas with a low flash point at room temperature, and because of its low specific heat, it easily reaches its ignition point after absorbing heat. When hydrogen leaks and encounters sparks, it is very easy to explode, so it is necessary to monitor whether hydrogen leaks at all times. Therefore, there is a patent publication number CN104593738A of the People's Republic of China "A vanadium oxide film and its preparation method". During the preparation process, the oxygen flow rate during annealing is increased to make the surface of the prepared vanadium oxide film loose and porous, and at the same time, the phase change amplitude of the vanadium oxide film is increased. This method overcomes the shortcomings of long preparation time and low phase change amplitude of vanadium oxide film, can strictly control process parameters, improve process repeatability and the phase change amplitude of vanadium oxide film, thereby improving the sensitivity of the device. At the same time, the loose porous morphology increases the specific surface area of the film, which plays an important role in improving the gas-sensitive performance of the sensor and enables it to be better applied in practice.

However, the above-mentioned prior art still has the problem of insensitive response when simply using vanadium oxide as the sensing film. Therefore, how to prepare a gas sensor with better response to hydrogen sensing is one of the goals that people in this field want to work hard on.

Therefore, in order to provide a sensor with better response, a method for manufacturing a hydrogen sensor having a nickel-doped vanadium pentoxide thin film is proposed, comprising the following steps:

A silicon substrate is subjected to a heating step to form a silicon dioxide layer on the surface of the silicon substrate; a chromium-gold film is deposited on the silicon dioxide layer by an evaporation technique, and a sensing electrode layer is formed on the surface of the silicon dioxide layer; a vanadium pentoxide target, a nickel oxide target and the silicon substrate are arranged in a sputtering space of a sputtering device, and the vanadium pentoxide target and the nickel oxide target are respectively kept at a sputtering distance of 5 cm from the silicon substrate; a co-sputtering treatment is performed on the silicon substrate. The silicon substrate is maintained at an operating temperature of 100 degrees Celsius, the co-sputtering treatment time is 60 minutes, the sputtering power of the vanadium pentoxide target is controlled at a first power, the sputtering power of the nickel oxide target is controlled at a second power, the first power is 120W, the second power is 30W, and the silicon substrate is rotated with the normal direction parallel to the sensing electrode layer as the rotation center, so that a nickel-doped vanadium pentoxide thin film layer is uniformly formed on the sensing electrode layer.

Furthermore, the sputtering space is filled with argon gas at a flow rate of 3 cubic centimeters per minute, so that a sputtering pressure in the sputtering space is maintained at 5×10 ^-3 torr.

Furthermore, the sensing electrode layer includes a first electrode and a second electrode, the first electrode and the second electrode are spaced apart, the nickel-doped vanadium pentoxide film layer contacts the first electrode and the second electrode at the same time, and the first electrode and the second electrode constitute an interdigitated electrode.

Furthermore, the thickness of the silicon dioxide layer is 250 nanometers, and the thickness of the sensing electrode layer is 100 nanometers.

A hydrogen sensor with a nickel-doped vanadium pentoxide thin film comprises: A silicon substrate having a surface; a silicon dioxide layer formed on the surface by a heating step; a sensing electrode layer attached to the silicon dioxide layer so that the silicon dioxide layer is between the silicon substrate and the sensing electrode layer; a nickel-doped vanadium pentoxide thin film layer attached to the sensing electrode layer by a co-sputtering process, wherein the co-sputtering process comprises co-sputtering a vanadium pentoxide target and a nickel monoxide target on the sensing electrode layer, wherein the vanadium pentoxide target and the nickel monoxide target are co-sputtered on the sensing electrode layer. The vanadium oxide target and the nickel oxide target are respectively kept at a sputtering distance of 5 cm from the silicon substrate. The co-sputtering treatment is performed for 60 minutes, and the silicon substrate is maintained at an operating temperature of 100 degrees Celsius. The sputtering power of the vanadium pentoxide target is controlled at a first power, and the sputtering power of the nickel oxide target is controlled at a second power, the first power is 120W, and the second power is 30W.

Furthermore, the sensing electrode layer includes a first electrode and a second electrode, the first electrode and the second electrode are spaced apart, the nickel-doped vanadium pentoxide film layer contacts the first electrode and the second electrode at the same time, and the first electrode and the second electrode constitute an interdigitated electrode.

Furthermore, the thickness of the silicon dioxide layer is 250 nanometers, and the thickness of the sensing electrode layer is 100 nanometers.

According to the above technical features, the following effects can be achieved:

1. During the co-sputtering process, the sputtering power of the vanadium pentoxide target was fixed at 120W. When the sputtering power of the nickel oxide target was set to 30W, the hydrogen sensor produced had a response of up to 2355.8% at 300 degrees Celsius, which is 17 times higher than that of the hydrogen sensor without nickel doping under the same measurement conditions.

2. When nickel is doped with vanadium pentoxide to produce nickel-doped vanadium pentoxide thin film, the transition metal nickel will change the morphology of the semiconductor oxide film surface and increase the specific surface area of the oxide film, thereby increasing the area of the hydrogen sensor in contact with hydrogen and increasing the reaction rate.

In view of the above technical features, the main effects of the hydrogen gas sensor having nickel-doped vanadium pentoxide thin film and the manufacturing method thereof of the present invention can be clearly presented in the following embodiments.

Please refer to the first, second, third and fourth figures, the manufacturing method of the hydrogen sensor with nickel-doped vanadium pentoxide thin film of the present invention comprises the following steps:

A silicon substrate 1 is subjected to a heating step to form a silicon dioxide layer 2 on the surface of the silicon substrate 1. The thickness of the silicon dioxide layer 2 is 250 nanometers. A chromium-gold film is deposited on the silicon dioxide layer 2 by an evaporation technique. A sensing electrode layer 3 is formed on the surface of the silicon dioxide layer 2. The thickness of the sensing electrode layer 3 is 100 nanometers. The sensing electrode layer 3 includes a first electrode and a second electrode. The first electrode and the second electrode are arranged at intervals, and the first electrode and the second electrode constitute an interdigitated electrode; a vanadium pentoxide target, a nickel monoxide target and the silicon substrate 1 are arranged in a sputtering space of a sputtering device, and an argon gas is filled in the sputtering space. The flow rate of the argon gas is 3 cubic centimeters per minute, and a sputtering pressure in the sputtering space is maintained at 5x10 ^-3 torr, the vanadium pentoxide target and the nickel oxide target are respectively kept at a sputtering distance of 4 to 6 cm from the silicon substrate 1. In the present embodiment, the sputtering distance is preferably 5 cm. The silicon substrate 1 is then subjected to a co-sputtering treatment to maintain the silicon substrate 1 at an operating temperature of 100 degrees Celsius. The co-sputtering treatment is performed for 60 minutes. The sputtering power of the vanadium pentoxide target is controlled at a first power The sputtering power of the nickel oxide target is controlled at a second power, the first power is 120W, and the second power is 0W, 20W, 30W and 40W respectively, and the silicon substrate 1 rotates with the normal direction parallel to the sensing electrode layer 3 as the rotation center, so that a nickel-doped vanadium pentoxide thin film layer 4 is uniformly formed on the sensing electrode layer 3, and the nickel-doped vanadium pentoxide thin film layer 4 contacts the first electrode and the second electrode at the same time.

A hydrogen sensor with a nickel-doped vanadium pentoxide thin film is manufactured according to the aforementioned manufacturing method of the hydrogen sensor with a nickel-doped vanadium pentoxide thin film, comprising the silicon substrate 1, the silicon dioxide layer 2, the sensing electrode layer 3 and the nickel-doped vanadium pentoxide thin film layer 4; specifically, the silicon dioxide layer 2 is between the silicon substrate 1 and the sensing electrode layer 3, and the nickel-doped vanadium pentoxide thin film layer 4 is attached to the sensing electrode layer 3.

When the hydrogen sensor using the nickel-doped vanadium pentoxide thin film of the present case measures hydrogen, since hydrogen is a reducing gas, the electron affinity of hydrogen molecules is smaller than the work function of the surface of the nickel-doped vanadium pentoxide thin film layer 4, and the electrons in the hydrogen molecules will be transferred to the nickel-doped vanadium pentoxide thin film layer 4, and the hydrogen molecules will form hydrogen ions. In this case, if the nickel-doped vanadium pentoxide thin film layer 4 is an N-type semiconductor, the electron concentration on the surface of the nickel-doped vanadium pentoxide thin film layer 4 will be increased, further reducing the resistance of the nickel-doped vanadium pentoxide thin film layer 4; if the nickel-doped vanadium pentoxide thin film layer 4 is a P-type semiconductor, the electron concentration on the surface of the nickel-doped vanadium pentoxide thin film layer 4 will be reduced, further increasing the resistance of the nickel-doped vanadium pentoxide thin film layer 4.

When sensing hydrogen, a considerable concentration of electrons will be provided to the nickel-doped vanadium pentoxide thin film layer 4 through the reaction mechanism described above, and depending on the form of the hydrogen sensor (N-type or P-type), the resistance of the nickel-doped vanadium pentoxide thin film layer 4 will decrease or increase; when hydrogen sensing stops, the nickel-doped vanadium pentoxide thin film layer 4 will return to its original state.

When metal is doped on the semiconductor oxide film, the morphology of the semiconductor oxide film surface is changed and the specific surface area is increased, thereby increasing the area of the hydrogen sensor in contact with hydrogen. In addition, metal doping will also cause oxygen in the crystal lattice of the semiconductor oxide film to be desorbed, resulting in oxygen deficiency and the formation of oxygen vacancies. For example, in the present case, part of the V5 ⁺ ions in _{the V2O5} crystal lattice are converted into V4 ⁺ ions, thereby causing the effect of oxygen deficiency. As a result, the valence electrons originally attracted by oxygen will be released and become free electrons that can conduct electricity, thereby increasing the conductivity of the nickel-doped vanadium pentoxide thin film layer 4, thereby increasing the response of electrical measurement and shortening the response time and recovery time.

When performing the sputtering process, the rate of thin film sputtering can be controlled by controlling parameters such as the temperature of the substrate, the current of the target, the voltage of the target, and the distance between the sample and the target, thereby affecting the composition of the thin film.

In this case, metal is added to the semiconductor oxide film. During the experiment, the temperature of the substrate and the distance between the test piece and the target are set to fixed values, and only the current and voltage of the target are controlled. Furthermore, the sputtering process in this case is carried out through co-sputtering, so there are two types of targets, namely the vanadium pentoxide target and the nickel oxide target; that is, in this case, the nickel oxide target and the vanadium pentoxide target are used to produce the nickel-doped vanadium pentoxide thin film layer 4 by co-sputtering. When performing the sputtering process, the sputtering power of the vanadium pentoxide target is set to a fixed value, and only the sputtering power of the nickel oxide target is adjusted. When the sputtering power of the nickel oxide target increases, the strength of the external electric field changes, the current density generated by the plasma will also increase, and the argon molecules in the sputtering space will be further ionized, and the energy of the generated ions will also increase relatively, thereby increasing the probability of ions hitting the nickel oxide target, and the sputtering rate of nickel can be increased, so that the nickel-doped vanadium pentoxide thin film layer 4 has more nickel.

In this case, different hydrogen sensors with nickel-doped vanadium pentoxide thin films are co-sputtered by using different sputtering powers of the nickel oxide target, such as 0W, 20W, 30W and 40W, and a fixed sputtering power of the vanadium pentoxide target of 120W, and the parameters during sputtering are such as maintaining a sputtering distance of 5 cm between the vanadium pentoxide target and the nickel oxide target and the silicon substrate 1, and maintaining the temperature of the silicon substrate 1 at 100 degrees Celsius, and corresponding to the nickel-doped vanadium pentoxide thin film layer 4 produced under different sputtering powers of the nickel oxide target. In this case, X-ray photoelectron spectroscopy (XPS) was used to detect the nickel concentration in the nickel-doped vanadium pentoxide thin film layer 4 produced under different sputtering powers, which were 0%, 5.63%, 18.8%, and 19.11%, respectively. It can be seen that when the sputtering power of the nickel oxide target is higher, the concentration of nickel doped in the nickel-doped vanadium pentoxide thin film layer 4 is also relatively increased.

However, an increase in the concentration of nickel doped in the nickel-doped vanadium pentoxide thin film layer 4 does not mean that the responsiveness during hydrogen sensing is better. Excessive nickel doping will cause distortion of the crystal structure and affect the responsiveness of the nickel-doped vanadium pentoxide thin film layer 4. Therefore, this case further measures hydrogen with a fixed concentration to compare which nickel oxide target sputtering power produces a hydrogen sensor with a better responsiveness.

The formula for responsiveness is as follows:

Where _Ig is the current obtained by passing hydrogen, and _Ia is the current obtained in the atmosphere without detecting hydrogen.

Please refer to Figures 5, 6, 7 and 8, which are the relationship diagrams of time and current when multiple hydrogen sensors made by the present invention use different nickel oxide sputtering powers to detect hydrogen. During the detection, hydrogen with a fixed concentration, such as 1000ppm or 500ppm, is introduced, and hydrogen is continuously introduced for 120 seconds and then stopped for 300 seconds, and this is repeated three times to obtain the relationship diagram of time and current when hydrogen sensors made by different nickel oxide sputtering powers are measuring hydrogen. The measured current is substituted into the above-mentioned response formula to obtain the response of hydrogen sensors using different sputtering powers when measuring hydrogen.

Please refer to Figure 9, Figure 10 and Table 1 below, which show electrical properties of each hydrogen sensor measured at a fixed ambient temperature, such as 300°C. When the second power is 0W, the measured response of the hydrogen sensor is 131.6%. Similarly, when the second power is 20W, the response is 977.2%, when the second power is 30W, the response is 2355.8%, and when the second power is 40W, the response is 1934.1%, which is 17 times higher than that when nickel is not doped.

It can be seen that when the second power is 30W, the manufactured hydrogen sensor has the best response of 2355.8%. Table 1 Ambient temperature 300℃ 0W 20W 30W 40W Responsiveness 131.6% 977.2% 2355.8% 1934.1%

Combined with the description of the above embodiments, the operation, use and effects of the present invention can be fully understood. However, the above embodiments are only preferred embodiments of the present invention and cannot be used to limit the scope of implementation of the present invention. In other words, simple equivalent changes and modifications made according to the scope of the patent application of the present invention and the content of the invention description are all within the scope of the present invention.

1: Silicon substrate 2: Silicon dioxide layer 3: Sensing electrode layer 4: Nickel-doped vanadium pentoxide thin film layer

[Figure 1] is a flow chart of the present invention.

[Figure 2] is an appearance diagram of the hydrogen sensor of the present invention.

[Figure 3] is a manufacturing flow chart of the hydrogen sensor of the present invention.

[Figure 4] shows the atomic percentages of vanadium, nickel and oxygen atoms contained in nickel-doped vanadium pentoxide thin films produced by the present invention using different nickel oxide sputtering powers.

[Figure 5] is a graph showing the relationship between current and time when the hydrogen sensor is not doped with nickel and is measuring hydrogen.

[Figure 6] is a graph showing the relationship between current and time when measuring hydrogen in a hydrogen sensor made by sputtering nickel oxide at a power of 20W.

[Figure 7] is a graph showing the relationship between current and time when measuring hydrogen in a hydrogen sensor made by sputtering nickel oxide at a power of 30W.

[Figure 8] is a graph showing the relationship between current and time when measuring hydrogen in a hydrogen sensor made by sputtering nickel oxide at a power of 40W.

[Figure 9] is a graph showing the relationship between the response and time of the hydrogen sensor made by the present invention using different nickel oxide sputtering powers when detecting hydrogen at an ambient temperature of 300°C.

[Figure 10] is a graph showing the relationship between the response and power of the hydrogen sensor made by the present invention using different nickel oxide sputtering powers when detecting hydrogen at an ambient temperature of 300°C.

Claims (2)

A method for manufacturing a hydrogen sensor having a nickel-doped vanadium pentoxide thin film comprises the following steps: Taking a silicon substrate and performing a heating step to form a silicon dioxide layer on the surface of the silicon substrate, the thickness of the silicon dioxide layer is 250 nanometers; Using an evaporation technique to deposit a chromium-gold film on the silicon dioxide layer, and forming a sensing electrode layer on the surface of the silicon dioxide layer, the thickness of the sensing electrode layer is 100 nanometers, the sensing electrode layer includes a first electrode and a second electrode, the first electrode and the second electrode are spaced apart, and the first electrode and the second electrode constitute an interdigitated electrode; A vanadium pentoxide target, a nickel oxide target and the silicon substrate are placed in a sputtering space of a sputtering device, and an argon gas is filled in the sputtering space. The flow rate of the argon gas is 3 cubic centimeters per minute, and a sputtering pressure in the sputtering space is maintained at 5x10-3 torr. The vanadium pentoxide target and the nickel oxide target are respectively kept at a sputtering distance of 5 centimeters from the silicon substrate; A co-sputtering treatment is performed on the silicon substrate to maintain an operating temperature of 100 degrees Celsius. The co-sputtering treatment time is 60 minutes. The sputtering power of the vanadium pentoxide target is controlled at a first power, and the sputtering power of the nickel oxide target is controlled at a second power. The first power is 120W, and the second power is 30W. The silicon substrate rotates with the normal direction parallel to the sensing electrode layer as the rotation center, so that a nickel-doped vanadium pentoxide thin film layer is uniformly formed on the sensing electrode layer. The nickel-doped vanadium pentoxide thin film layer contacts the first electrode and the second electrode at the same time. A hydrogen sensor with nickel-doped vanadium pentoxide thin film comprises: A silicon substrate having a surface; A silicon dioxide layer formed on the surface by a heating step, the thickness of the silicon dioxide layer being 250 nanometers; A sensing electrode layer attached to the silicon dioxide layer so that the silicon dioxide layer is between the silicon substrate and the sensing electrode layer, the thickness of the sensing electrode layer being 100 nanometers, the sensing electrode layer comprising a first electrode and a second electrode, the first electrode and the second electrode being spaced apart, the first electrode and the second electrode forming an interdigitated electrode; A nickel-doped vanadium pentoxide thin film layer is attached to the sensing electrode layer through a co-sputtering process, and the nickel-doped vanadium pentoxide thin film layer contacts the first electrode and the second electrode at the same time. The co-sputtering process includes co-sputtering a vanadium pentoxide target and a nickel oxide target on the sensing electrode layer, and the vanadium pentoxide target and the nickel oxide target are respectively connected to the silicon substrate. The sputtering distance is 5 cm, the co-sputtering treatment time is 60 minutes, and the silicon substrate is maintained at an operating temperature of 100 degrees Celsius. The sputtering power of the vanadium pentoxide target is controlled at a first power, and the sputtering power of the nickel oxide target is controlled at a second power. The first power is 120W, and the second power is 30W.

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