WO2011158827A1 - Ultraviolet ray sensor, and process for production of ultraviolet ray sensor - Google Patents

Abstract

Disclosed is an ultraviolet ray sensor comprising: a p-type semiconductor layer (1) which is mainly composed of a solid solution of NiO and ZnO; and a n-type semiconductor layer (2) which is mainly composed of ZnO and is bound to the p-type semiconductor layer (1) in such a state where a part of the surface of the p-type semiconductor layer (1) is exposed. A first terminal electrode (3a) that is connected to an internal electrode (4) and a second terminal electrode (3b) that is connected to the n-type semiconductor layer (2) are formed at both ends of the p-type semiconductor layer (1), respectively. The internal electrode (4) is composed of a composite oxide represented by general formula: RNiO₃ or the like, containing a rare earth element (R) and Ni as the main components, and having low resistivity. The ultraviolet ray sensor can detect ultraviolet ray readily as a photovoltaic power without the need of using any peripheral circuit and without causing delamination or the like, is inexpensive, and can have a reduced size.

Description

Ultraviolet sensor and method for manufacturing ultraviolet sensor

The present invention relates to an ultraviolet sensor and a method for manufacturing the ultraviolet sensor. More specifically, the present invention relates to a photodiode-type ultraviolet ray having a laminated structure in which a p-type semiconductor layer and an n-type semiconductor layer are heterojunction using an oxide compound semiconductor. The present invention relates to a sensor and a manufacturing method thereof.

Ultraviolet sensors are widely used as flame sensors for fire alarms, burner combustion monitoring devices, etc., and as ultraviolet detection devices for detecting the amount of ultraviolet irradiation outdoors. In recent years, they are also expected to be applied to optical communication devices. ing.

Conventionally, this type of ultraviolet sensor uses a diamond semiconductor or SiC semiconductor as a sensor material. However, these diamond semiconductors and SiC semiconductors have the disadvantage that they are inferior in material processability and are expensive.

Therefore, recently, oxide semiconductors that are easy to process materials and are relatively inexpensive have attracted attention, and an ultraviolet sensor in which a p-type semiconductor layer and an n-type semiconductor layer are heterojunction using these oxide semiconductors. Research and development are actively conducted.

For example, Patent Document 1 discloses a ZnO layer 101 which is an n-type oxide semiconductor and a p-type oxide semiconductor provided so as to be in contact with the ZnO layer 101 (Ni, The (Zn) O layer 102, the first terminal electrode 103 electrically connected to the ZnO layer 101, and the (Ni, Zn) O layer 102 are electrically connected via the conductive layer 104 made of a transition metal oxide or the like. An ultraviolet sensor 106 is disclosed that includes a second terminal electrode 105 connected to the terminal.

In this patent document 1, when ultraviolet light is irradiated in the direction of arrow a and ultraviolet light hits the depletion layer formed at the junction between the n-type ZnO layer 101 and the p-type (Ni, Zn) O layer 102, Carriers are excited to generate a photocurrent, which makes it possible to detect ultraviolet rays.

However, the carrier concentration of the (Ni, Zn) O layer 102 is extremely lower than the carrier concentration of the ZnO layer 101, and the specific resistance of the (Ni, Zn) O layer 102 cannot be made sufficiently low. Even if the 101 is irradiated with ultraviolet rays, only a weak photocurrent is generated. Moreover, since the weak photocurrent is almost consumed by the internal resistance of the (Ni, Zn) O layer 102, it cannot be actually detected as a current value.

For this reason, in Patent Document 1, as shown in FIG. 16, first and second terminal electrodes 103 and 105 are formed on the front surface side of the ZnO layer 101 and the back surface side of the conductive layer 104, respectively, and the power supply circuit 107 is externally provided. And the intensity of ultraviolet rays is detected as a change in resistance value. That is, a voltage is applied to the first and second terminal electrodes 103 and 105 at the time of ultraviolet irradiation, the change is measured by the resistor 109 connected in parallel to the power supply 108, and the ultraviolet intensity is detected by the change in the resistance value. .

Patent Document 2 discloses a laminate including a (Ni, Zn) O layer and a ZnO layer formed so as to cover a part of one main surface of the (Ni, Zn) O layer; A first terminal electrode electrically connected to the Zn) O layer; a second terminal electrode electrically connected to both the (Ni, Zn) O layer and the ZnO layer; An ultraviolet sensor including an internal electrode made of Pd or the like formed in the (Ni, Zn) O layer while being electrically connected to a terminal electrode is disclosed.

In this Patent Document 2, since at least part of the junction between the (Ni, Zn) O layer which is a p-type semiconductor and the ZnO layer which is an n-type semiconductor is exposed on the surface, the ultraviolet rays to be detected are detected in the ZnO layer. Therefore, it is possible to obtain an ultraviolet sensor that does not cause a decrease in sensitivity due to attenuation when passing through the ZnO layer.

Japanese Patent No. 3952076 (FIG. 3) JP 2009-300206 A (FIG. 1, paragraph number [0053])

However, in Patent Document 1, since the power supply circuit 107 is provided outside as described above and the ultraviolet intensity must be detected as a change in resistance value, it is necessary to secure a mounting space for the power supply circuit 107. Further, the resistance value detected by the power supply circuit 107 is high, and therefore a high input impedance measuring machine and an amplifier circuit are separately required. As described above, Patent Document 1 has a problem that an expensive peripheral circuit is required and a device is also enlarged.

In Patent Document 1, the intensity of ultraviolet rays is detected by a change in resistance value. However, since the resistance value of the (Ni, Zn) O layer 102 varies greatly depending on the measurement temperature, the resistance value detected by the power supply circuit 107 is detected. Is a combination of a resistance value due to ultraviolet irradiation and a resistance fluctuation value due to temperature change. For this reason, in order to acquire only ultraviolet intensity, temperature correction etc. were needed and there existed a problem of causing the complexity of a device.

Furthermore, in Patent Document 1, when the substrate is mounted, the (Ni, Zn) O layer 102 has a high resistance that is approximately the same as that of the substrate, so that it is difficult to ensure insulation when mounted.

On the other hand, Patent Document 2 uses Pd as an internal electrode material for simultaneous firing with (Ni, Zn) O in an oxidizing atmosphere at 1250 ° C. That is, in order to co-fire with (Ni, Zn) O, a noble metal material is usually used as the internal electrode material, and it is conceivable to use Pt in addition to Pd.

However, when these precious metal materials are used, the material cost becomes high and there are the following problems.

That is, since these noble metal materials have a large work function, an unnecessary Schottky barrier is formed with (Ni, Zn) O. Therefore, even if a photoelectromotive force is generated by ultraviolet irradiation, it is almost consumed by this Schottky barrier, and as in Patent Document 1, an external power supply circuit must be provided and detected as a resistance change value.

Also, when Pt is used, Pt has a catalytic action on the oxidation reaction, and the reaction is rapidly accelerated in the firing process. For this reason, expansion of the internal electrode may be caused, or cracks may be caused in the (Ni, Zn) O layer, and delamination (delamination) may occur.

In addition, when Pd is used, Pd absorbs oxygen when it reaches a high temperature above a certain temperature (for example, 800 ° C.), and releases oxygen when the temperature is lowered after firing. That is, due to the oxygen releasing action of Pd, oxygen is supplied to the object to be fired when the temperature is lowered, and there is a possibility that a strong oxide layer may be formed on the crystal grain boundary or surface of (Ni, Zn) O. . As a result of the formation of such an oxide layer, the apparent specific resistance of (Ni, Zn) O increases, so that even if a photovoltaic force is generated, it is weak and difficult to detect.

Thus, when a noble metal material like patent document 2 is used for an internal electrode material, it is expensive, and in the case of Pt, there is a possibility of causing delamination, and when Pd is used, Similarly, an external power supply circuit must be provided to detect the ultraviolet intensity by a resistance change, so that an expensive peripheral circuit is required and the device may be increased in size.

The present invention has been made in view of such circumstances, and does not require a peripheral circuit, does not cause delamination, and the like, and can be easily detected at low cost and downsizing as a photovoltaic power. An object of the present invention is to provide a possible ultraviolet sensor and a method for producing the ultraviolet sensor.

In order to achieve the above object, the present inventor uses (Ni, Zn) O as a p-type oxide semiconductor, uses ZnO as an n-type oxide semiconductor, and uses (Ni, Zn) O as an internal electrode. As a result of diligent research on the ultraviolet sensor embedded in the interior of the substrate, by using a low-resistance complex oxide mainly composed of rare earth elements and Ni as an internal electrode material, (Ni, Zn) O The specific resistance can be made sufficiently low, and it has been found that ultraviolet rays can be detected as a photovoltaic force.

The present invention has been made on the basis of such knowledge, and the ultraviolet sensor according to the present invention includes a p-type semiconductor layer mainly composed of a solid solution of NiO and ZnO, and a p-type semiconductor composed mainly of ZnO. An n-type semiconductor layer bonded to the p-type semiconductor layer in a form in which a part of the semiconductor layer is exposed on the surface, an internal electrode embedded in the p-type semiconductor layer, and formed at both ends of the p-type semiconductor layer In the ultraviolet sensor having the terminal electrode formed, the internal electrode is formed of a complex oxide mainly composed of a rare earth element and Ni.

In the ultraviolet sensor of the present invention, it is preferable that the rare earth element includes at least one selected from La, Pr, Nd, Sm, Gd, Dy, Ho, Er, and Yb.

By the way, in the ultraviolet sensor, the internal electrode is electrically connected to one terminal electrode, but is not electrically connected to the other terminal electrode, and the internal electrode and the other terminal electrode are not electrically connected. There is a possibility that an electrical resistance is formed between them, and a closed circuit is formed between the n-type semiconductor layer and the p-type semiconductor layer.

If the generated photocurrent leaks to the closed circuit, that is, the p-type semiconductor layer side, energy loss occurs, which may impair the inherent characteristics of the material. Therefore, it is preferable that the resistance between the internal electrode and the other terminal electrode is increased and electrically insulated so that the photocurrent does not leak to the p-type semiconductor layer side.

That is, in the ultraviolet sensor of the present invention, the terminal electrode includes a first terminal electrode connected to the internal electrode, and a second terminal electrode connected to the n-type semiconductor layer, and at least the first electrode An insulating layer is preferably formed between the two terminal electrodes and the internal electrode.

The insulating layer is a region excluding the entire surface or a part of the surface of the p-type semiconductor layer and the junction interface between the p-type semiconductor layer and the n-type semiconductor layer so as to surround the central portion of the p-type semiconductor layer. By forming the insulating layer, an insulating layer can be formed in substantially the entire region between the terminals parallel to the sensor characteristic acquisition portion, and in addition to the p-type semiconductor layer side, the leakage of photocurrent to the first terminal electrode also occurs. It can be reduced, and it becomes possible to further suppress the energy loss.

That is, the ultraviolet sensor of the present invention is such that the insulating layer surrounds the central portion of the p-type semiconductor layer, and the junction interface between the p-type semiconductor layer and the n-type semiconductor layer. Preferably, it is formed in a region excluding all or a part of.

Also, it is possible to suppress energy loss by providing an insulating layer between the p-type semiconductor layer and the second terminal electrode, as described above.

That is, in the ultraviolet sensor of the present invention, it is preferable that the insulating layer is interposed between the p-type semiconductor layer and the second terminal electrode.

In the ultraviolet sensor of the present invention, it is preferable that the insulating layer contains at least Si.

In the ultraviolet sensor of the present invention, it is preferable that the insulating layer is mainly composed of zinc silicate.

As a method for producing the internal electrode in the ultraviolet sensor, a paste containing a composite oxide containing Ni and a rare earth element as a main component is applied to a green sheet and fired, or a paste containing a rare earth element is applied. There is a method of forming by reacting with Ni contained in a green sheet to be a p-type semiconductor layer. The former can obtain stable characteristics, and the latter can be manufactured at low cost.

That is, in the method for manufacturing an ultraviolet sensor according to the present invention, an internal electrode is embedded in a p-type semiconductor layer mainly composed of a solid solution of NiO and ZnO, and the n-type semiconductor layer mainly composed of the p-type semiconductor layer and ZnO. In which the p-type semiconductor layer manufacturing step for manufacturing the p-type semiconductor layer in which the internal electrode is embedded includes a green sheet mainly composed of a solid solution of NiO and ZnO. A green sheet manufacturing step to be manufactured; a first paste manufacturing step of preparing a first paste containing at least a rare earth element; and applying the first paste to a surface of the green sheet; A first laminated film forming step to be formed; a predetermined number of the green sheets are laminated so that the first coated film is sandwiched between the green sheets; A laminate manufacturing step of manufacturing is characterized in that it contains a firing step of firing the green laminate.

Furthermore, in the method for producing an ultraviolet sensor of the present invention, it is preferable that the first paste production step includes a composite oxide production step of producing a composite oxide from a raw material powder containing a rare earth oxide and a Ni oxide. .

Further, in the method for producing an ultraviolet sensor of the present invention, the first paste production step produces a rare earth paste mainly composed of a rare earth oxide, and the firing step diffuses Ni contained in the green sheet. It is preferable to react with the rare earth element to form an internal electrode made of a composite oxide.

In addition, the insulating layer described above applies a paste containing Si to a green sheet, and reacts Si and Zn contained in the green sheet at the time of simultaneous firing in the firing step to form high-resistance zinc silicate. Therefore, it can be easily manufactured.

That is, in the method for producing an ultraviolet sensor of the present invention, a second paste production step of producing a second paste containing at least Si, and applying the second paste around the first coating film, A second coating film forming step of forming a second coating film, wherein the baking step comprises reacting Zn contained in the green sheet with Si contained in the second coating film, It is preferable to form an insulating layer mainly composed of zinc acid.

Further, in the method for manufacturing an ultraviolet sensor of the present invention, a green sheet on which the first coating film is not formed is used, and the second paste is applied to a peripheral portion of the green sheet, and a third coating film is formed. A third coating film forming step for forming the second coating film, and a fourth coating film forming step for coating the second paste over the entire surface of one surface of the green sheet to form a fourth coating film, In the laminate manufacturing step, the green sheet on which the fourth coating film is formed is arranged in a lower layer to prepare the green laminate, and the firing step includes Zn contained in the green sheet and the third It is preferable that Si contained in the fourth coating film reacts to form an insulating layer mainly composed of zinc silicate.

The method for manufacturing an ultraviolet sensor of the present invention includes a second paste preparation step of preparing the second paste containing at least a Si component, and the first coating film on the side where the surface is not exposed. It is preferable to apply the second paste to the end face of the green laminate.

According to the ultraviolet sensor of the present invention, the p-type semiconductor layer is mainly composed of a solid solution of NiO and ZnO, and the p-type semiconductor layer is composed mainly of ZnO and a part of the p-type semiconductor layer is exposed on the surface. An ultraviolet sensor having an n-type semiconductor layer bonded to a semiconductor layer, an internal electrode embedded in the p-type semiconductor layer, and terminal electrodes formed at both ends of the p-type semiconductor layer, wherein the internal electrode is Since it is formed of a composite oxide containing rare earth elements (eg, La, Pr, Nd, Sm, Gd, Dy, Ho, Er, and Yb) and Ni, the resistance of the p-type semiconductor layer is reduced. It is possible to detect the intensity of ultraviolet rays based on the photovoltaic force obtained at the time of ultraviolet light irradiation. That is, since the internal electrode is a Ni-based oxide like the p-type semiconductor layer, both energy levels are close and there is no Schottky barrier, and the p-type semiconductor layer and the internal electrode are in almost ohmic contact. It becomes. Therefore, it becomes possible to detect ultraviolet rays as a photovoltaic power, particularly a photovoltaic voltage, and it is not necessary to provide a power supply circuit and other peripheral circuits outside, and it is not necessary to use an expensive noble metal material for the internal electrode material. An inexpensive and downsized ultraviolet sensor can be obtained.

The terminal electrode includes a first terminal electrode connected to the internal electrode and a second terminal electrode connected to the n-type semiconductor layer, and at least the second terminal electrode and the internal electrode When an insulating layer (such as zinc silicate containing Si) is formed between the electrode and the electrode, the leakage of photocurrent from the second terminal electrode to the p-type semiconductor layer during ultraviolet irradiation is reduced. Thus, energy loss can be suppressed.

In addition, since the temperature characteristic of the resistance that can be formed between the second terminal electrode and the internal electrode can be cut, the temperature characteristic is also flattened and is not affected by the resistance temperature characteristic of the p-type semiconductor layer. It is possible to detect the intensity of ultraviolet rays with the photovoltage.

Further, the insulating layer is formed so as to surround the central portion of the p-type semiconductor layer, and excludes the surface of the p-type semiconductor layer and the whole or part of the junction interface between the p-type semiconductor layer and the n-type semiconductor layer. When formed in the region, most of the portions other than the portion exhibiting sensor characteristics are covered with the insulating layer, the surface insulation is promoted, and the light to the first terminal electrode is added to the p-type semiconductor layer side. Current leakage can also be reduced. As a result, energy loss can be more effectively suppressed, and environmental adaptability can be improved.

Further, when the insulating layer is interposed between the p-type semiconductor layer and the second terminal electrode, energy loss can be suppressed as described above, and a highly sensitive ultraviolet sensor can be realized. be able to.

Further, according to the method for manufacturing an ultraviolet sensor of the present invention, the p-type semiconductor layer manufacturing step in which the internal electrode is embedded includes at least a green sheet manufacturing step of manufacturing a green sheet mainly composed of a solid solution of NiO and ZnO. A first paste manufacturing step for preparing a first paste containing a rare earth element, and a first coating film forming step for applying the first paste to the surface of the green sheet to form a first coating film A laminate manufacturing step of stacking a predetermined number of the green sheets so that the first coating film is sandwiched between the green sheets, and preparing a green laminate, and a firing step of firing the green laminate Therefore, the internal electrode contains rare earth elements that are difficult to diffuse into the p-type semiconductor layer, and does not promote the oxidation reaction unlike Pd. Nor oxidized layer Akiratsubu boundaries and surface. Also, it does not cause catalysis like Pt, and since the green sheet and the first coating film are Ni-based oxides, the shrinkage behavior at high temperature is close, delamination does not occur, and the internal The electrode is not drawn into the p-type semiconductor layer.

As described above, according to the manufacturing method of the present invention, no Schottky barrier or oxide layer is formed between the internal electrode and the p-type semiconductor layer, and the p-type semiconductor layer is formed without causing delamination. It is possible to easily manufacture an ultraviolet sensor capable of reducing the resistance and detecting the ultraviolet intensity by the photovoltaic force.

In addition, when the first paste preparation step includes a composite oxide preparation step of preparing a composite oxide from a raw material powder containing rare earth oxide and Ni oxide, the composition of the internal electrode is stable. Therefore, a desired photovoltaic power having stable characteristics can be obtained by ultraviolet irradiation.

Further, the first paste preparation step is made to produce a rare earth paste mainly composed of a rare earth oxide, and the firing step is performed by diffusing Ni contained in the green sheet and reacting with the rare earth element. When an internal electrode made of an oxide is formed, a desired internal electrode can be obtained without preparing a composite oxide for forming an internal electrode in advance, and an ultraviolet sensor can be manufactured at low cost. it can.

Also, a second paste production step for producing a paste containing at least Si, and a second coating film for coating the second paste around the first coating film to form a second coating film Forming an insulating layer containing zinc silicate as a main component by reacting Zn contained in the green sheet and Si contained in the second coating film. In this case, it is possible to easily and inexpensively manufacture a high resistance insulating layer extending in the stacking direction.

A third coating film forming step of forming a third coating film by using a green sheet on which the first coating film is not formed, applying the second paste to a peripheral portion of the green sheet; And a fourth coating film forming step of applying the second paste to the entire surface of one surface of the green sheet to form a fourth coating film, and The green sheet on which the coating film is formed is arranged in a lower layer so as to produce the green laminate, and the firing step is included in Zn contained in the green sheet and the third and fourth coating films. When an insulating layer mainly composed of zinc silicate is formed by reacting with Si, the insulating layer should be easily formed in the entire region between the terminals parallel to the sensor characteristic acquisition part. Energy loss even more It is possible to manufacture the ultraviolet sensor capable suppressed.

It is sectional drawing which shows typically one Embodiment (1st Embodiment) of the ultraviolet sensor which concerns on this invention. It is a disassembled perspective view of the green laminated body of 1st Embodiment. It is sectional drawing which showed typically the ultraviolet sensor which formed the closed circuit at the time of ultraviolet irradiation. FIG. 4 is an equivalent circuit diagram of FIG. 3. It is sectional drawing which shows typically 2nd Embodiment of the ultraviolet sensor which concerns on this invention. It is a disassembled perspective view of the green laminated body of 2nd Embodiment. It is sectional drawing which shows typically 3rd Embodiment of the ultraviolet sensor which concerns on this invention. It is sectional drawing which shows typically the green laminated body of 3rd Embodiment. It is sectional drawing which shows typically 4th Embodiment of the ultraviolet sensor which concerns on this invention. It is a disassembled perspective view of the green laminated body of 4th Embodiment. FIG. 3 is a diagram illustrating a method for measuring output current according to the first embodiment. It is a figure which shows the relationship between the irradiance in Example 1, and an output current. FIG. 3 is a diagram showing the relationship between the wavelength and the output current in sample number 1 of Example 1. It is a figure which shows the relationship between the irradiance in Example 3, and an output current. It is a figure which shows the relationship between the wavelength in Example 3, and an output current. It is a figure which shows the detection method of the ultraviolet sensor and electromotive force which were described in patent document 1. FIG.

Next, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

FIG. 1 is a cross-sectional view schematically showing one embodiment (first embodiment) of an ultraviolet sensor according to the present invention.

That is, this ultraviolet sensor has a p-type semiconductor layer 1 mainly composed of a solid solution of NiO and ZnO, and an n-type semiconductor layer 2 made of a ZnO-based material. The n-type semiconductor layer 2 is a p-type semiconductor. The p-type semiconductor layer 1 is bonded in a form in which a part of the surface of the layer 1 is exposed.

The p-type semiconductor layer 1 can be represented by the general formula (Ni _1-x Zn _x ) O (hereinafter referred to as (Ni, Zn) O), and the blending molar ratio x of Zn has good sensitivity. From the viewpoint of obtaining stably, 0.2 ≦ x ≦ 0.4 is preferable. If x is less than 0.2, the Ni content may be excessive and the resistance may be increased. On the other hand, if x exceeds 0.4, the Zn content will be excessive and ZnO particles may be produced. This is because there is a risk of precipitation at the crystal grain boundary and making it an n-type semiconductor.

In addition, the ZnO-based material forming the n-type semiconductor layer 2 may contain a trace amount of additives as long as it contains ZnO as a main component. For example, Al, Co, In, Ga or the like may be contained as a dopant, and Fe, Ni, Mn or the like may be contained as a diffusing agent. Even if a trace amount of Zr, Si, or the like is contained as an impurity, it does not affect the characteristics.

Further, first and second terminal electrodes 3a and 3b are formed on both ends of the p-type semiconductor layer 1. That is, the internal electrode 4 is embedded in the upper part of the p-type semiconductor layer 1 so that one end is exposed on the surface, and the first terminal electrode 3 a is p-type so as to be electrically connected to the internal electrode 4. It is formed at one end of the semiconductor layer 1. The second terminal electrode 3 b is formed at the other end of the p-type semiconductor layer 1 so as to be electrically connected to the n-type semiconductor layer 2.

The first and second terminal electrodes 3a and 3b are formed by sequentially forming a first plating film made of Ni or the like and a second plating film made of Sn or the like on the surface of the external electrode made of Ag or the like.

In the ultraviolet sensor formed as described above, when ultraviolet light is irradiated as shown by an arrow A and the depletion layer formed at the junction interface 7 between the p-type semiconductor layer 1 and the n-type semiconductor layer 2 is irradiated with ultraviolet light, Carriers are excited to generate a photocurrent, and the intensity of ultraviolet rays can be detected by detecting this photocurrent.

In the present embodiment, the internal electrode 4 is composed of an oxide having a perovskite structure represented by the general formula RNiO ₃ or an oxide represented by the general formula R ₂ NiO ₄ . It is formed of a low-resistance complex oxide containing

The reason why the internal electrode 4 is formed of the above-described composite oxide is as follows.

Since (Ni, Zn) O forming the p-type semiconductor layer 1 is fired in an oxidizing atmosphere at around 1200 ° C., normally, a noble metal material such as Pd or Pt is used as the internal electrode material, and simultaneous firing is performed. It is possible to do.

However, as described in the section [Problems to be Solved by the Invention], these noble metal materials are expensive and have a large work function, and a Schottky barrier is formed between them and (Ni, Zn) O. . Since the photovoltaic power is consumed by this Schottky barrier, it is difficult to detect the ultraviolet intensity as the photovoltaic power. Moreover, when Pt is used, there is a risk that delamination may occur due to a rapid reaction in the firing process due to the catalytic action of Pt. In addition, when Pd is used, a strong oxide layer is formed on the grain boundaries and the surface of (Ni, Zn) O due to the oxygen releasing action of Pd during firing, and as a result, the appearance of (Ni, Zn) O The specific resistance above increases, so that only a weak photocurrent can be generated by the ultraviolet sensor. Therefore, when a noble metal material is used as the internal electrode material, an external power supply circuit must be provided to detect the UV intensity based on the resistance change value, and it is difficult to avoid increasing the cost and size of the device. It is.

On the other hand, the composite oxide mainly composed of the rare earth element R and Ni is a Ni-based oxide like (Ni, Zn) O, both of which are close in energy level and have a relationship with (Ni, Zn) O. An unnecessary Schottky barrier can be prevented from being formed between the layers, and almost ohmic contact is achieved. In addition, rare earth elements are less likely to diffuse to the (Ni, Zn) O side than Ni, and no catalytic action or oxygen releasing action occurs. Therefore, the specific resistance of (Ni, Zn) O can be reduced, and the ultraviolet intensity can be detected by the photovoltaic power without detecting the change in resistance. As a result, it is not necessary to provide a power supply circuit and other peripheral devices outside, and the device can be miniaturized. In addition, as described above, the composite oxide containing the rare earth elements R and Ni as the main components is a Ni-based oxide similar to (Ni, Zn) O, so that the shrinkage behavior at a high temperature is (Ni, Zn). Close to O, delamination is unlikely to occur between the p-type semiconductor layer 1 and the internal electrode 4, and there is no phenomenon of drawing the electrode into the sintered body. Further, since it is not necessary to use an expensive noble metal material, it is possible to suppress an increase in price.

For the above reasons, the present embodiment contains an oxide having a perovskite structure represented by the general formula RNiO ₃ and an oxide represented by the general formula R ₂ NiO ₄ , which are mainly composed of rare earth elements R and Ni. The internal electrode 4 is formed of a low resistance composite oxide.

Such a rare earth element is not particularly limited as long as it has a low resistance when a composite oxide is formed with Ni. For example, La, Pr, Nd, Sm, Gd, Dy At least one selected from Ho, Er, and Yb can be used. Of these, it is preferable to use inexpensive La for economic reasons.

Next, the manufacturing method of the ultraviolet sensor will be described in detail.

[Preparation of ZnO sintered body]
Prepare ZnO powder and additives such as various dopants and diffusing agents as required, and weigh a predetermined amount. Then, a solvent such as pure water is added to these weighed products, and cobblestones such as PSZ (partially stabilized zirconia) are used as a grinding medium, and the mixture is sufficiently wet-mixed using a ball mill to obtain a slurry mixture. Next, this slurry-like mixture is dehydrated and dried, granulated to a predetermined particle size, and then calcined at a predetermined temperature for about 2 hours to obtain a calcined powder. Next, a solvent such as pure water is again added to the calcined powder obtained in this manner, and cobblestone is used as a grinding medium, and the mixture is sufficiently wet-ground using a ball mill to obtain a slurry-like pulverized product. Next, after this slurry-like pulverized product is dehydrated and dried, pure water, a dispersant, a binder, a plasticizer, and the like are added to prepare a molding slurry. Thereafter, a molding process is performed on the molding slurry by using a molding process such as the doctor blade method to produce a ZnO green sheet having a predetermined film thickness. Next, a predetermined number of these ZnO green sheets are laminated and pressed to produce a pressed body. Thereafter, the pressure-bonded body is degreased and fired to obtain a ZnO sintered body.

[Production of (Ni, Zn) O Green Sheet]
NiO powder and ZnO powder are weighed so that the compounding molar ratio x of Zn is 0.2 to 0.4, a solvent such as pure water is added to the weighed product, and the ball is used as a grinding medium to sufficiently Mix and pulverize in a wet manner to obtain a slurry mixture. Next, the mixture is dehydrated and dried, granulated to a predetermined particle size, and calcined at a predetermined temperature for about 2 hours to obtain a calcined powder. Next, a solvent such as pure water is added again to the calcined powder thus obtained, and the mixture is sufficiently pulverized in a ball mill using cobblestone as a pulverizing medium to obtain a slurry pulverized product. Next, this slurry-like pulverized product is dehydrated and dried, and then an organic solvent, a dispersant, a binder, a plasticizer, and the like are added to produce a molding slurry. Next, the forming slurry is formed using a forming method such as a doctor blade method, thereby obtaining a (Ni, Zn) O green sheet having a predetermined film thickness.

[Preparation of internal electrode forming paste (first paste)]
NiO powder and R ₂ O ₃ powder (R: rare earth element) are weighed so as to have a molar ratio of 2: 1 and a solvent such as pure water is added to the weighed product, and the ball stone is used as a grinding medium in a ball mill. Thoroughly mix and pulverize in a wet manner to obtain a slurry mixture. Next, the slurry mixture is dehydrated and dried, granulated to a predetermined particle size, and calcined at a predetermined temperature for about 2 hours to obtain a calcined powder. Next, a solvent such as pure water is added again to the calcined powder thus obtained, and the mixture is sufficiently pulverized in a ball mill using cobblestone as a pulverizing medium to obtain a slurry pulverized product. Next, the slurry-like pulverized product is dehydrated and dried to obtain a composite oxide powder containing an oxide represented by the general formula RNiO ₃ or the general formula R ₂ NiO ₄ . Then, the obtained composite oxide powder is mixed with an organic vehicle and kneaded with a three-roll mill, thereby producing an internal electrode forming paste.

The organic vehicle is prepared such that the binder resin is dissolved in an organic solvent, and the binder resin and the organic solvent are, for example, in a volume ratio of 1 to 3: 7 to 9. The binder resin is not particularly limited, and for example, ethyl cellulose resin, nitrocellulose resin, acrylic resin, alkyd resin, or a combination thereof can be used. Also, the organic solvent is not particularly limited, and α-terpineol, xylene, toluene, diethylene glycol monobutyl ether, diethylene glycol monobutyl ether acetate, diethylene glycol monoethyl ether, diethylene glycol monoethyl ether acetate, etc. alone or in combination thereof Can be used.

[Production of green laminate]
A method for producing the green laminate will be described with reference to FIG.

First, a predetermined number of (Ni, Zn) O green sheets 5a, 5b, 5c,... 5n are prepared, and the above-mentioned internal electrode forming paste is applied to the surface of one (Ni, Zn) O green sheet 5b. The conductive film (first coating film) 6 is formed by coating.

Next, a predetermined number of (Ni, Zn) O green sheets 5c to 5n without a conductive film are stacked, and a (Ni, Zn) O green sheet 5b with a conductive film 6 formed thereon is stacked. Further, a (Ni, Zn) O green sheet 5a on which no conductive film is formed is laminated thereon and pressure-bonded to produce a green laminate.

[Production of p-type semiconductor layer 1]
After sufficiently degreasing the green laminate, it is fired at a temperature of around 1200 ° C. for about 5 hours, and the conductive film 6 and the (Ni, Zn) O green sheets 5a to 5n are simultaneously fired, whereby the internal electrode 4 is embedded. Thus obtained p-type semiconductor layer 1 is obtained.

[Preparation of terminal electrodes 3a, 3b]
An external electrode forming paste is applied to both ends of the p-type semiconductor layer 1 and a baking process is performed, thereby forming external electrodes. Here, the conductive material of the external electrode forming paste is not particularly limited as long as it has good conductivity, and Ag, Ag-Pd, or the like can be used.

Then, electrolytic plating is performed to form a two-layered plating film composed of the first plating film and the second plating film, thereby forming the first and second terminal electrodes 3a and 3b.

[Formation of n-type semiconductor layer 2]
Sputtering is performed through a metal mask having a predetermined opening with a ZnO sintered body as a target, a part of the p-type semiconductor layer 1 is exposed on the surface, and is electrically connected to the second terminal electrode 3b. As described above, the n-type semiconductor layer 2 made of a ZnO-based thin film is formed on the surface of the p-type semiconductor layer 1, thereby obtaining an ultraviolet sensor.

As described above, in the present embodiment, since the internal electrode 4 is formed of a low-resistance composite oxide mainly composed of rare earth elements and Ni, the resistance of the p-type semiconductor layer 1 can be reduced. The ultraviolet intensity can be detected by the photovoltaic force obtained during the irradiation with ultraviolet light. That is, since the internal electrode 4 is a Ni-based oxide like the p-type semiconductor layer 1, the energy levels of both are close, and the p-type semiconductor layer 1 and the internal electrode 4 may form a Schottky barrier. There is almost no ohmic contact. Further, even if the (Ni, Zn) O green sheets 5a, 5b, 5c,... 5n and the conductive film 6 are fired simultaneously, the rare earth elements hardly diffuse into the (Ni, Zn) O green sheets 5a, 5b, 5c,. , Oxygen releasing action like Pd does not occur. Therefore, the specific resistance of the p-type semiconductor layer 1 can be sufficiently lowered without forming a strong oxide layer on the crystal grain boundary or surface of (Ni, Zn) O. As a result, the ultraviolet intensity can be detected by the photovoltaic force, particularly the photovoltaic current, without detecting the ultraviolet intensity by the resistance value change. Therefore, it is not necessary to provide a power supply circuit and other peripheral circuits outside, and it is not necessary to use an expensive noble metal material for the internal electrode material, and an inexpensive and downsized ultraviolet sensor can be obtained.

In addition, the catalytic action does not occur as in the case of using Pt for the internal electrode, and the internal electrode material is a Ni-based oxide similar to that of the p-type semiconductor layer 1. Delamination hardly occurs, and the internal electrode 4 is not drawn into the p-type semiconductor layer 1.

Further, since no precious metal materials such as Pd and Pt are used, it is possible to obtain a highly sensitive ultraviolet sensor without causing an increase in price.

In the above embodiment, the internal electrode forming paste containing the composite oxide is prepared, and the internal electrode forming paste is applied to the surface of the (Ni, Zn) O green sheet and then fired. The internal electrode 4 is formed, but as a modification, a rare earth paste whose main component is composed of a rare earth oxide R ₂ O ₃ is produced without including Ni in the internal electrode forming paste, and during firing ( It is also preferable to embed it in a Ni, Zn) O green sheet.

The ultraviolet sensor of this modification can be manufactured as follows.

That is, as in the above embodiment, a ZnO sintered body and a (Ni, Zn) O green sheet are produced.

Next, the R ₂ O ₃ powder is mixed with the above-described organic vehicle and kneaded with a three-roll mill, thereby producing a rare earth paste.

Then, this rare earth paste is applied to the surface of the (Ni, Zn) O green sheet 5b to form a rare earth film (first coating film).

Next, a predetermined number of (Ni, Zn) O green sheets 5c,... 5n on which no rare earth film is formed are laminated, and (Ni, Zn) O green sheets 5b on which a rare earth film is formed are laminated thereon, Further, a (Ni, Zn) O green sheet 5a on which no rare earth film is formed is laminated thereon and pressed to produce a green laminate.

Next, the green laminate is sufficiently degreased and fired at a temperature of about 1200 ° C. for about 5 hours to simultaneously fire the conductive film 6 and the (Ni, Zn) O green sheets 5a to 5n. A p-type semiconductor layer 1 is embedded. In this firing treatment, the rare earth element R is not easily diffused to the (Ni, Zn) O green sheet side, and Ni in the (Ni, Zn) O green sheet is diffused to the rare earth film side. An internal electrode made of a complex oxide mainly composed of the elements R and Ni is formed.

Thereafter, the first and second terminal electrodes 3a, 3b, and the n-type semiconductor layer 2 are sequentially formed by the same method and procedure as in the above embodiment, thereby producing an ultraviolet sensor.

Thus, even if the composite oxide is not synthesized in advance during the preparation of the internal electrode forming paste, a low resistance layer made of a composite oxide containing rare earth elements R and Ni as main components is synthesized during firing, so that it can be manufactured at low cost. Is possible. However, in the case of the above modification, the composition of (Ni, Zn) O is likely to fluctuate during firing, and a different phase such as R ₂ NiO ₆ is likely to be generated.

By the way, as described above, by using a low-resistance composite oxide mainly composed of rare earth elements R and Ni as the internal electrode material, it is possible to use the photovoltaic power without detecting the ultraviolet intensity as a change in resistance value. As shown in FIG. 3, depending on the size of the internal electrode 4, an electrical resistance 8 is formed between the tip of the internal electrode 4 and the second terminal electrode 3b.

In this case, a diode 9 is formed by a pn junction between the p-type semiconductor layer 1 and the n-type semiconductor layer 2 as shown in FIG. Become.

However, when the photocurrent generated by irradiating ultraviolet rays flows in a closed circuit as shown by the arrow B direction and leaks from the second terminal electrode 3b to the p-type semiconductor layer 1 side, energy loss occurs, and the original material is lost. Properties may be impaired.

Therefore, it is preferable to increase the insulation between the internal electrode 4 and the second terminal electrode 3b so that the photocurrent does not leak from the second terminal electrode 3b to the p-type semiconductor layer 1 side.

Hereinafter, the preferred embodiments will be described in detail in the second to fourth embodiments.

FIG. 5 is a sectional view showing a second embodiment of the ultraviolet sensor according to the present invention. In the second embodiment, an insulating layer is provided between the internal electrode 4 and the second terminal electrode 3b. 10 is formed.

Here, the insulating layer 10 is not particularly limited as long as it is an insulating high resistance layer, and for example, Si-containing Si oxide can be used. Is formed of zinc silicate. That is, as will be described later, in the simultaneous firing in the firing step, Si in the insulating film reacts with the surrounding (Ni, Zn) O green sheet to generate zinc silicate, thereby the main component spreading in the stacking direction. A high-resistance insulating layer 10 made of zinc silicate is formed.

And the ultraviolet sensor of this 2nd Embodiment can be manufactured as follows.

First, a ZnO sintered body, a (Ni, Zn) O green sheet, and an internal electrode forming paste are prepared by the same method and procedure as in the first embodiment. Further, the SiO ₂ powder is mixed with an organic vehicle and kneaded by a three-roll mill, thereby producing a SiO ₂ paste (second paste).

Next, a (Ni, Zn) O green sheet, internal electrode forming paste, and SiO ₂ paste are used to produce a green laminate.

FIG. 6 is an exploded perspective view of the green laminate.

First, a predetermined number of (Ni, Zn) O green sheets 11a, 11b, 11c,... 11n are prepared, and on the surface of one (Ni, Zn) O green sheet 11b, the first embodiment and Similarly, an internal electrode forming paste is applied to form a conductive film (first coating film) 12.

Next, an SiO ₂ paste is applied in a U shape so as not to overlap the conductive film 12 on the (Ni, Zn) O green sheet 11 b, and an insulating film (second coating film) 13 is formed around the conductive film 12. Form.

Next, a predetermined number of (Ni, Zn) O green sheets 11c to 11n are stacked, and a (Ni, Zn) O green sheet 11b having a conductive film 12 and an insulating film 13 formed thereon is stacked. A (Ni, Zn) O green sheet 11a is laminated on top of each other and pressed to produce a green laminate.

Next, the green laminate is sufficiently degreased and fired at a temperature of about 1200 ° C. for about 5 hours to simultaneously fire the conductive film 12, the insulating film 13, and the (Ni, Zn) O green sheets 11a to 11n. Then, Zn having a low melting point in (Ni, Zn) O and SiO _{2 of the} insulating film 13 react to form the insulating layer 10 containing zinc silicate as a main component in a state of spreading in the stacking direction. Thereby, the p-type semiconductor layer 1 in which the internal electrode 4 and the insulating layer 10 are embedded is obtained.

After that, the first and second terminal electrodes 3a and 3b are produced by the same method and procedure as in the first embodiment, and then sputtered using a ZnO sintered body as a target, and the p-type semiconductor layer 1 An n-type semiconductor layer 2 is formed on the surface of the substrate, thereby producing an ultraviolet sensor.

Thus, in the second embodiment, since the insulating layer 10 mainly composed of zinc silicate is formed between the internal electrode 4 and the second terminal electrode 3b, the second terminal electrode 3b Leakage of photocurrent to the p-type semiconductor layer 1 side can be reduced, and energy loss can be suppressed.

In addition, since the temperature characteristic of the resistance that can be formed between the second terminal electrode 3b and the internal electrode 4 can be cut, the temperature characteristic is also flattened, and the desired temperature characteristic is not affected by the resistance temperature characteristic. It is possible to detect the ultraviolet intensity with the photovoltage.

FIG. 7 is a cross-sectional view showing a third embodiment of the ultraviolet sensor according to the present invention. In the third embodiment, a gap between the p-type semiconductor layer 1 and the second terminal electrode 3b ′ is shown. An insulating layer 14 is formed.

The ultraviolet sensor according to the third embodiment can be manufactured as follows.

That is, by using the same method and procedure as in the first embodiment, a green laminate 15 is produced as shown in FIG. 8, and then an SiO ₂ paste is applied to the end face on the side where the conductive film 6 is not exposed. Thus, the insulating film 16 is formed. Next, the p-type semiconductor layer 1 is formed by baking in the same manner as in the first embodiment. Also in this case, SiO ₂ reacts with Zn of the (Ni, Zn) O sheet to form the zinc silicate insulating layer 14. After that, as in the first embodiment, after forming the terminal electrodes 3a, 3b ', the n-type semiconductor layer 2 is formed by sputtering using a ZnO sintered body as a target. Produced.

As described above, in the third embodiment, since the insulating layer 14 is formed between the p-type semiconductor layer 1 and the second terminal electrode 3b ′, the photocurrent is transferred from the second terminal electrode 3b ′ to the p. Leakage to the type semiconductor layer 1 can be reduced, and energy loss can be suppressed.

FIG. 9 is a sectional view showing a fourth embodiment of the ultraviolet sensor according to the present invention. In the fourth embodiment, in addition to the second embodiment, the p-type semiconductor layer 1 An insulating layer 17 is formed on the surface of the p-type semiconductor layer 1 and in a region excluding a part of the junction interface between the p-type semiconductor layer 1 and the n-type semiconductor layer 2 so as to surround the central portion.

The ultraviolet sensor according to the fourth embodiment can be manufactured as follows.

First, a ZnO sintered body, a (Ni, Zn) O green sheet, and an internal electrode forming paste are prepared by the same method and procedure as in the first embodiment, and the same method and procedure as in the second embodiment are performed. A SiO ₂ paste is prepared by the procedure.

Next, a (Ni, Zn) O green sheet, internal electrode forming paste, and SiO ₂ paste are used to produce a green laminate.

FIG. 10 is an exploded perspective view of the green laminate.

First, a predetermined number of (Ni, Zn) O green sheets 18a, 18b, 18c,..., 18m, 18n are prepared, and the first implementation is performed on the surface of one (Ni, Zn) O green sheet 18b. As in the above embodiment, the conductive film 19 is formed by applying the internal electrode forming paste.

Next, an SiO ₂ paste is applied in a U shape on the (Ni, Zn) O green sheet 18 b so as not to overlap the conductive film 19, thereby forming an insulating film 20 b around the conductive film 19.

Further, SiO ₂ paste is applied to the peripheral portions of the (Ni, Zn) O green sheets 18a, 18c,... 18m to form insulating films (third coating films) 20a, 20c,. Further, an SiO ₂ paste is applied to the entire surface of the (Ni, Zn) O green sheet 18n to form an insulating film (fourth coating film) 20n.

Next, (Ni, Zn) O green sheets 18a, 18b, 18c,... 18m are laminated on the (Ni, Zn) O green sheet 18n, and are pressed to produce a green laminate.

Next, the green laminate is sufficiently degreased and fired at a temperature of about 1200 ° C. for about 5 hours, and the conductive film 19, the insulating films 20a to 20n, and the (Ni, Zn) O green sheets 18a to 18n are simultaneously formed. Bake. During the firing, Zn in the (Ni, Zn) O green sheets 18a to 18n reacts with SiO _{2 in the} insulating films 20a to 20m to generate zinc silicate. That is, the surface of the p-type semiconductor layer 1 and the p-type semiconductor layer 1 and the n-type semiconductor layer in such a manner that the insulating layer 17 mainly composed of zinc silicate surrounds the central portion of the p-type semiconductor layer 1. 2 is formed in a region excluding a part of the junction interface, whereby the p-type semiconductor layer 1 is manufactured.

After that, the first and second terminal electrodes 3a and 3b are produced by the same method and procedure as in the first embodiment, and then sputtered using a ZnO sintered body as a target, and the p-type semiconductor layer 1 An n-type semiconductor layer 2 is formed on the surface of the substrate, thereby producing an ultraviolet sensor.

As described above, in the fourth embodiment, the surface of the p-type semiconductor layer 1 and the junction interface between the p-type semiconductor layer 1 and the n-type semiconductor layer 2 are formed so as to surround the central portion of the p-type semiconductor layer 1. 7 is formed in a region excluding a part of the portion 7, most of the portion other than the portion exhibiting sensor characteristics is covered with the insulating layer 17, and surface insulation is promoted to obtain good insulation. . And thereby, it can suppress that a photocurrent leaks between the terminal electrode 3a and the n-type semiconductor layer 2, and can further aim at suppression of energy loss. Moreover, since most parts other than the part which expresses a sensor characteristic are covered with the insulating layer 17, plating property, flux resistance, and environmental resistance can be improved.

Further, similar to the second embodiment, the temperature characteristic of the resistance that can be formed between the second terminal electrode 3b and the internal electrode 4 can be cut, so that the resistance temperature characteristic is also flatter and better. Thus, the ultraviolet intensity can be detected with a desired photovoltage without being affected by the temperature characteristics of the resistor.

The present invention is not limited to the above embodiment. For example, in the second to fourth embodiments, SiO ₂ is applied as the insulating paste. However, it may be at least containing Si, and may be in the form of a sol or an organic compound, for example.

In the fourth embodiment, it is formed on the surface of the p-type semiconductor layer 1 and in a region excluding a part of the junction interface 7 between the p-type semiconductor layer 1 and the n-type semiconductor layer 2. An insulating layer may be formed in a region excluding the entire region of the bonding interface 7 according to the use and performance.

Next, specific examples of the present invention will be described.

(Sample No. 1)
[Preparation of ZnO sintered body]
ZnO as a main component and Ga ₂ O ₃ as a dopant were weighed so that the compounding ratio was 99.9 mol% and 0.1 mol%, respectively, in mol%. Then, pure water was added to these weighed products, and the mixture was pulverized in a ball mill using PSZ beads as a pulverization medium to obtain a slurry mixture having an average particle size of 0.5 μm or less. Next, this slurry-like mixture was dehydrated and dried, granulated to a particle size of about 50 μm, and calcined at a temperature of 1200 ° C. for 2 hours to obtain a calcined powder.

Next, pure water was again added to the calcined powder thus obtained, and the mixture was pulverized in a ball mill using PSZ beads as a pulverization medium to obtain a slurry-like pulverized product having an average particle size of 0.5 μm. Next, this slurry-like pulverized product is dehydrated and dried, and pure water and a dispersant are added and mixed. Further, a binder and a plasticizer are added to produce a molding slurry, and the thickness is 20 μm using a doctor blade method. A green sheet was prepared. Next, a predetermined number of the green sheets were laminated so as to have a thickness of 20 mm, and a pressure-bonding treatment was performed at a pressure of 250 MPa for 5 minutes to obtain a pressure-bonded body. Next, the pressure-bonded body was degreased and then fired at a temperature of 1200 ° C. for 20 hours to obtain a ZnO sintered body.

[Production of (Ni, Zn) O Green Sheet]
NiO powder and ZnO powder were weighed so as to have a molar ratio of 7: 3, pure water was added thereto, and the mixture was pulverized with a ball mill using PSZ beads as a pulverization medium to obtain a slurry mixture. Next, this slurry-like mixture was dehydrated and dried, granulated to a particle size of about 50 μm, and calcined at a temperature of 1200 ° C. for 2 hours to obtain a calcined powder. Next, pure water was again added to the calcined powder thus obtained, and the mixture was pulverized in a ball mill using PSZ beads as a pulverization medium to obtain a slurry pulverized product having an average particle size of 0.5 μm. Next, after this slurry-like pulverized product was dehydrated and dried, an organic solvent and a dispersant were added and mixed, and a binder and a plasticizer were further added to prepare a molding slurry. Then, using the doctor blade method, the forming slurry was subjected to a forming process to obtain a (Ni, Zn) O green sheet having a thickness of 10 μm.

[Internal electrode forming paste]
NiO powder and La ₂ O ₃ powder as a rare earth oxide were weighed so as to have a molar ratio of 2: 1, pure water was added to the weighed product, and the mixture was pulverized in a ball mill using PSZ beads as a grinding medium. A slurry mixture was obtained. Next, this slurry-like mixture was dehydrated and dried, granulated to a particle size of about 50 μm, and calcined at a temperature of 1200 ° C. for 2 hours to obtain a calcined powder. Next, pure water was again added to the calcined powder thus obtained, and the mixture was pulverized in a ball mill using PSZ beads as a pulverization medium to obtain a slurry pulverized product having an average particle size of 0.5 μm. The slurry pulverized product was dehydrated and dried to obtain LaNiO ₃ powder. Thereafter, the obtained LaNiO ₃ powder was mixed with an organic vehicle and kneaded with a three-roll mill, thereby producing an internal electrode forming paste. The organic vehicle was prepared by mixing ethyl cellulose resin and α-terpineol so that 30% by volume of ethyl cellulose resin as a binder resin and 70% by volume of α-terpineol as an organic solvent.

[Production of green laminate]
One of the (Ni, Zn) O green sheets was screen printed with an internal electrode forming paste and dried at a temperature of 60 ° C. for 1 hour to form a conductive film having a predetermined pattern.

Next, 20 (Ni, Zn) O green sheets on which no conductive film is formed are stacked, and a (Ni, Zn) O green sheet on which a conductive film is formed is stacked thereon. One (Ni, Zn) O green sheet on which no film was formed was sequentially laminated. These were pressure-bonded at a pressure of 20 MPa and then cut into dimensions of 3.2 mm × 1.6 mm, thereby producing a green laminate.

[Production of p-type semiconductor layer]
The green laminate was sufficiently degreased at a temperature of 300 ° C. and then fired at a temperature of 1250 ° C. for 5 hours, thereby obtaining a p-type semiconductor layer.

[Production of terminal electrode]
Ag paste was applied to both ends of the p-type semiconductor layer and baked at a temperature of 800 ° C. to produce first and second external electrodes. Then, electrolytic plating was performed on the surfaces of the first and second external electrodes to sequentially form a Ni film and a Sn film, thereby producing first and second terminal electrodes.

[Formation of n-type semiconductor layer]
Sputtering is performed using a ZnO sintered body as a target, using a metal mask so as to cover a part of one main surface of the p-type semiconductor layer and to overlap a part of the second terminal electrode. An n-type semiconductor layer having a predetermined pattern of .5 μm was produced, whereby a sample of sample number 1 was obtained.

(Sample No. 2)
A sample of sample number 2 was prepared by the same method and procedure as sample number 1 except that the conductive film to be the internal electrode was prepared using La ₂ O ₃ paste.

The La ₂ O ₃ paste was prepared by mixing commercially available La ₂ O ₃ powder with the same organic vehicle as in sample number 1 and kneading with a three-roll mill.

(Sample No. 3)
Sample No. 3 was prepared by the same method and procedure as Sample No. 1 except that the conductive film to be the internal electrode was prepared using a commercially available Pd paste.

(Sample evaluation)
As shown in FIG. 11, each of the samples of sample numbers 1 to 3 has an internal electrode 32 embedded in the p-type semiconductor layer 31 and first and second ends on both ends of the p-type semiconductor layer 31. Terminal electrodes 33 a and 33 b are formed, and an n-type semiconductor layer 34 is bonded to the surface of the p-type semiconductor layer 31. Then, with respect to each of these samples, ultraviolet light having a wavelength of 365 nm is irradiated on the outer surface on the n-type semiconductor layer 34 side in the dark room as indicated by an arrow C from an ultraviolet light source equipped with a spectroscope. The current flowing between the first and second terminal electrodes 33a and 33b was measured.

The irradiance of ultraviolet light was 0.001 to 10 mW / cm ² and the measurement temperature was controlled to be 25 ° C. ± 1 ° C.

FIG. 12 shows the measurement results. The horizontal axis represents the irradiance (mW / cm ² ), the vertical axis represents the output current (nA), the ◯ mark indicates the sample number 1, and the Δ mark indicates the sample number 2.

Sample No. 3 using Pd paste could not detect the output current. This is because the internal electrode 32 is made of Pd, so that a strong oxide layer is formed on the grain boundaries and the surface of (Ni, Zn) O due to the oxygen releasing action of Pd at a high temperature. It seems that the apparent specific resistance of Zn) O increased and the output current could not be detected as a photovoltaic force.

On the other hand, it was found that the samples Nos. 1 and 2 can detect the output current in proportion to the irradiance. In particular, it was found that Sample No. 1, which was formed by firing a conductive film of LaNiO ₃ , had a stable composition, and thus a larger output current (photoelectromotive force) was obtained.

Next, for sample number 1, the irradiance was set to 1 mW / cm ² and the wavelength response characteristic was examined by changing the light source wavelength of the ultraviolet light stepwise from 200 nm to 600 nm every 10 nm.

FIG. 13 shows the measurement results, where the horizontal axis represents wavelength (nm) and the vertical axis represents output current (nA).

As is apparent from FIG. 13, the ultraviolet sensor of the present invention reacts only to ultraviolet light having a wavelength of 380 nm or less, does not react at all to visible light having a wavelength of 500 nm or more, and has excellent wavelength response characteristics to ultraviolet light. It was confirmed to have

Pr ₆ O ₁₁ , Nd ₂ O ₃ , Sm ₂ O ₃ , Gd ₂ O ₃ , Dy ₂ O ₃ , Ho ₂ O ₃ , Rr ₂ O ₃ , and Yb ₂ O ₃ were prepared as rare earth oxide powders. Sample number 11 was obtained by the same method and procedure as sample number 1 in Example 1, except that the internal electrode forming paste was prepared using these rare earth oxide powders instead of La ₂ O _3. ~ 18 samples were made.

Subsequently, as in Example 1, wavelength 365 nm, ultraviolet light irradiance 1 mW / cm ² was irradiated to each sample and measure the current value between the first and second terminal electrodes.

Table 1 shows the rare earth oxide, internal electrode forming paste, and output current used for sample numbers 11-18. Moreover, the measurement result of [Example 1] is also shown as a reference example.

As is apparent from Table 1, it was confirmed that even when a rare earth element other than La was used, the output current could be detected without providing an external power supply circuit, similarly to La.

Example except that SiO ₂ paste was applied around the (Ni, Zn) O green sheet on which the conductive film was formed, and an insulating film (insulating layer) was formed between the internal electrode and the second terminal electrode Sample No. 21 was prepared in the same manner and procedure as Sample No. 1 No. 1.

Here, the SiO ₂ paste was prepared by mixing commercially available SiO ₂ powder in an organic vehicle similar to Sample No. 1 in [Example 1] and then kneading with a three-roll mill.

The insulating film was formed by applying a LaNiO ₃ paste on a (Ni, Zn) O green sheet and drying at 60 ° C. for 1 hour to form a conductive film, and then applying a SiO ₂ paste around the conductive film. And formed by drying at 60 ° C. for 1 hour.

And the relationship between the irradiance and the output current was examined for the sample No. 21 by the same method and procedure as in Example 1.

FIG. 14 shows the measurement results. The horizontal axis is the irradiance (mW / cm ² ), the vertical axis is the output current (nA), and the sample of sample number 1 is shown again for reference. In the figure, the mark ● is sample number 21 and the mark ○ is sample number 1.

As is apparent from FIG. 14, the sample No. 21 has a larger output current as the irradiance increases than the sample No. 1 sample. This is because an insulating layer is formed between the internal electrode and the second terminal electrode, so that the photocurrent leaking from the second terminal electrode to the p-type semiconductor layer side is reduced, thereby suppressing energy loss. This is probably because

Next, the wavelength response characteristics of Sample No. 21 were examined by the same method and procedure as in Example 1.

FIG. 15 shows the measurement results. The horizontal axis represents wavelength (nm) and the vertical axis represents output current (nA), and the measurement results of sample number 1 are shown again for reference. In the figure, the mark ● is sample number 21 and the mark ○ is sample number 1.

As is clear from FIG. 15, the sample of sample number 21 reacts only to ultraviolet light having a wavelength of 380 nm or less, does not react at all to visible light having a wavelength of 500 nm or more, and has a good wavelength response characteristic to ultraviolet light. It was confirmed to have.

And since the sample of the sample number 21 has an insulating layer formed between the internal electrode and the second terminal electrode, the energy loss is suppressed as described above, and as a result, the peak current (wavelength: about: 330 nm) was confirmed to be nearly 10 times that of the sample No. 1.

Detecting the UV intensity with the photovoltaic force eliminates the need to detect the UV intensity with a resistance change by providing an external power supply circuit or the like, which makes it possible to realize a small and inexpensive UV sensor.

1 p-type semiconductor layer 2 n-type semiconductor layer 3a first terminal electrode 3b, 3b ′ second terminal electrode 4 internal electrodes 5a to 5n (Ni, Zn) O green sheet 6 conductive film (first coating film)
10 Insulating layers 11a to 11n (Ni, Zn) O green sheet 12 Conductive film (first coating film)
13, 20b Insulating film (second coating film)
14 Insulating layer 15 Green laminate 16 Insulating films 17a to 17n Insulating layers 18a to 18n (Ni, Zn) O green sheet 19 Conductive film (first coating film)
20a, 20c to 20m Insulating film (third coating film)
20n insulating film (fourth coating film)

Claims (13)

1. A p-type semiconductor layer mainly composed of a solid solution of NiO and ZnO, and an n-type semiconductor composed mainly of ZnO and bonded to the p-type semiconductor layer in a form in which a part of the p-type semiconductor layer is exposed on the surface. In an ultraviolet sensor having a layer, an internal electrode embedded in the p-type semiconductor layer, and terminal electrodes formed at both ends of the p-type semiconductor layer,
   The ultraviolet sensor, wherein the internal electrode is formed of a complex oxide mainly composed of a rare earth element and Ni.
2. The ultraviolet sensor according to claim 1, wherein the rare earth element includes at least one selected from La, Pr, Nd, Sm, Gd, Dy, Ho, Er, and Yb.
3. The terminal electrode includes a first terminal electrode connected to the internal electrode, and a second terminal electrode connected to the n-type semiconductor layer,
   The ultraviolet sensor according to claim 1, wherein an insulating layer is formed at least between the second terminal electrode and the internal electrode.
4. The insulating layer surrounds the central portion of the p-type semiconductor layer and is formed on the surface of the p-type semiconductor layer and in a region excluding the whole or part of the junction interface between the p-type semiconductor layer and the n-type semiconductor layer The ultraviolet sensor according to claim 3, wherein the ultraviolet sensor is formed.
5. The ultraviolet sensor according to claim 3 or 4, wherein the insulating layer is interposed between the p-type semiconductor layer and the second terminal electrode.
6. The ultraviolet sensor according to any one of claims 3 to 5, wherein the insulating layer contains at least Si.
7. The ultraviolet sensor according to claim 6, wherein the insulating layer contains zinc silicate as a main component.
8. An ultraviolet sensor manufacturing method comprising embedding an internal electrode in a p-type semiconductor layer mainly composed of a solid solution of NiO and ZnO, and joining the p-type semiconductor layer and an n-type semiconductor layer mainly composed of ZnO. ,
   A p-type semiconductor layer manufacturing step of manufacturing the p-type semiconductor layer in which the internal electrode is embedded;
   A green sheet production step of producing a green sheet mainly composed of a solid solution of NiO and ZnO;
   A first paste producing step of producing a first paste containing at least a rare earth element;
   A first coating film forming step of applying the first paste to the surface of the green sheet to form a first coating film;
   A laminate production step of producing a green laminate by laminating a predetermined number of the green sheets so that the first coating film is sandwiched between the green sheets;
   A method for producing an ultraviolet sensor, comprising: a firing step of firing the green laminate.
9. 9. The method of manufacturing an ultraviolet sensor according to claim 8, wherein the first paste manufacturing step includes a composite oxide manufacturing step of manufacturing a composite oxide from a raw material powder containing rare earth oxide and Ni oxide. .
10. In the first paste production step, a rare earth paste mainly comprising a rare earth oxide is produced,
    9. The method for manufacturing an ultraviolet sensor according to claim 8, wherein in the firing step, Ni contained in the green sheet is diffused and reacted with the rare earth element to form an internal electrode made of a composite oxide.
11. A second paste production step of producing a second paste containing at least Si;
    A second coating film forming step of applying the second paste around the first coating film to form a second coating film;
    The said baking process reacts Zn contained in the said green sheet, and Si contained in a said 2nd coating film, and forms the insulating layer which has a zinc silicate as a main component. The manufacturing method of the ultraviolet sensor in any one of Claims 8 thru | or 10.
12. A third coating film forming step of using a green sheet on which the first coating film is not formed, applying the second paste to a peripheral portion of the green sheet, and forming a third coating film;
    A fourth coating film forming step of applying the second paste to the entire surface of one surface of the green sheet to form a fourth coating film;
    The laminate manufacturing step arranges the green sheet on which the fourth coating film is formed in a lower layer to prepare the green laminate,
    The firing step is characterized in that Zn contained in the green sheet reacts with Si contained in the third and fourth coating films to form an insulating layer mainly composed of zinc silicate. The method for manufacturing an ultraviolet sensor according to any one of claims 8 to 11.
13. Including a second paste production step of producing a second paste containing at least a Si component;
    13. The ultraviolet sensor according to claim 8, wherein the second paste is applied to an end face of the green laminated body on a side where the surface of the first coating film is not exposed. Production method.

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