JP2008305815A - Ultraviolet sensor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain a diode-type ultraviolet sensor which has a laminate structure for forming hetero junction, has no directivity, does not need an extraction electrode and further has flat spectral wavelength sensitivity characteristics over a wide wavelength range. <P>SOLUTION: The ultraviolet sensor 1 includes a laminate 4 containing a ZnO layer 2 as an n-type semiconductor and a (Ni, Zn)O layer 3 as a p-type semiconductor. First and second terminal electrodes 5 and 6 are respectively provided on respective ends of the laminate 4. First and second current path application electrodes 7 and 8 electrically connected with the first and second terminal electrodes 5 and 6 are provided in the (Ni, Zn)O layer 3 at a predetermined interval 9 between them and on the same plane. A third current path application electrode 10 with a thin line is provided on an external surface of the ZnO layer 2. The ZnO layer 2 is located on a light receiving side for ultraviolet rays. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an ultraviolet sensor, and more particularly to a diode type ultraviolet sensor having a laminated structure for forming a heterojunction.

For example, JP-A-2004-172166 (Patent Document 1) includes a single crystal substrate made of an n-type semiconductor containing TiO ₂ as a main component and a transition metal oxide thin film formed thereon by epitaxial growth. An optical sensor is described. In this optical sensor, the transition metal oxide thin film side is the light receiving side, and electrodes are provided on the light receiving surface provided by the outer surface of the transition metal oxide thin film and the back surface of the substrate opposite thereto.

  Therefore, this optical sensor has directionality, and it is necessary to form lead electrodes such as bumps. These cause obstruction of the downsizing of the optical sensor, and in order to protect the element, it is necessary to treat the casing and the like, resulting in an increase in cost.

On the other hand, the response wavelength of the conventional optical sensor is 280 to 400 nm for GaPAs, ZnO, and TiO ₂ systems, and 230 nm or less for diamond. Therefore, as long as these conventional optical sensors are used, for example, ultraviolet rays having a wavelength of 250 to 260 nm used for sterilization cannot be efficiently detected.
JP 2004-172166 A

  Therefore, an object of the present invention is to provide an ultraviolet sensor that can solve the above-described problems, that is, has no directivity, does not particularly require an extraction electrode, and has a flat spectral wavelength sensitivity characteristic over a wide wavelength range. Is to try.

  An ultraviolet sensor according to the present invention includes a ZnO layer made of an oxide semiconductor containing ZnO, and an oxide semiconductor made of ZnO dissolved in NiO, in contact with the ZnO layer (Ni , Zn) O layer.

  In order to solve the above-described technical problem, first, an ultraviolet sensor according to the present invention includes a first and a second layer on each end of the laminated body facing each other in a direction in which a Zn layer and a (Ni, Zn) O layer extend. The first feature is that each of the second terminal electrodes is provided.

  In the ultraviolet sensor according to the present invention, the first and second current path providing electrodes electrically connected to the first and second terminal electrodes, respectively, in the (Ni, Zn) O layer. A thin line is provided on the outer surface of the Zn layer so as to be opposed to the distance between the first and second current path applying electrodes. And a third current path providing electrode that is not directly connected to any electrode is provided as a second feature.

  Furthermore, the ultraviolet sensor according to the present invention has a third feature that the Zn layer is used so as to be positioned on the ultraviolet light receiving side.

In the above-described ultraviolet sensor, a protective film may be provided on the outer surface of the Zn layer, thereby completely covering the third current path providing electrode. This protective film is made of, for example, ZnO, Zn ₂ SiO ₄ , glass or resin.

  In another aspect, the ultraviolet sensor according to the present invention is characterized in that the third current path providing electrode is provided in the ZnO layer. That is, the ZnO layer is provided with a third current path providing electrode that is formed with a thin line so as to face the interval between the first and second current path providing electrodes and is not directly connected to any electrode. It is a feature.

  The ultraviolet sensor according to the present invention relates to a surface extending in a direction orthogonal to a surface on which the first and second current path providing electrodes extend and passing through a center position of a distance between the first and second current path providing electrodes. It preferably has a symmetric structure.

  In the present invention, it is preferable that at least the Zn layer and the (Ni, Zn) O layer are obtained by integrally sintering them.

  According to the ultraviolet sensor of the present invention, the current path is “first current path application electrode” → “(Ni, Zn) O layer” → “interface between (Ni, Zn) O layer and ZnO layer” → “ZnO layer” → “third current path providing electrode” → “ZnO layer” → “interface between (Ni, Zn) O layer and ZnO layer” → “(Ni, Zn) O layer” → “second” First current path such as “current path providing electrode” or “second current path providing electrode” → “(Ni, Zn) O layer” → “interface between (Ni, Zn) O layer and ZnO layer” → “ ZnO layer ”→“ third current path providing electrode ”→“ ZnO layer ”→“ interface between (Ni, Zn) O layer and ZnO layer ”→“ (Ni, Zn) O layer ”→“ first current ” Although a second current path such as a “path providing electrode” can be taken, any one of the first and second current paths can take “(Ni, Zn O layer and the current barrier provided by the interface "between the ZnO layer will flow twice in total to the forward and reverse directions. And even if an electric current flows through which direction, since resistance value does not change substantially, the directionality of this ultraviolet sensor can be lost. As a result, the cost for direction selection can be saved, and the risk due to a wrong direction can be reduced.

  In the ultraviolet sensor according to the present invention, the first and second current path providing electrodes are electrically connected to the first and second terminal electrodes, respectively, and the first and second terminal electrodes are laminated bodies. Therefore, no special lead electrode is required, and surface mounting can be applied for mounting. Therefore, the cost for mounting can be reduced, and downsizing of the device using the ultraviolet sensor can be achieved.

  In addition, according to the ultraviolet sensor of the present invention, flat spectral wavelength sensitivity characteristics can be obtained over a wide wavelength range. The reason is considered as follows.

  That is, in the ultraviolet sensor according to the present invention, when ultraviolet light hits the depletion layer formed at the junction between the n-type ZnO layer and the p-type (Ni, Zn) O layer, carriers are excited here, A photocurrent is generated, and ultraviolet light is detected by detecting the photocurrent. In addition to the first or second current path described above, a “first current path application electrode” → “(Ni, Zn) O layer” → “second current path providing electrode” or “second current path providing electrode” → “(Ni, Zn) O layer” → “first current path providing electrode”, etc. Therefore, various current paths can be taken. In addition, the ZnO layer through which current flows, the (Ni, Zn) O layer, and the interface between the (Ni, Zn) O layer and the ZnO layer are made of polycrystalline ceramic, so that the band gap is widened. It is thought that there is. From these facts, according to the ultraviolet sensor according to the present invention, it is considered that the wavelength of the ultraviolet rays that can be detected is widened, and the sensitivity characteristic is flat.

  In the ultraviolet sensor according to the present invention, since the third current path providing electrode located on the ultraviolet light receiving side is formed with a thin line, the transmission of the ultraviolet light is allowed in the gap between the thin lines. And, according to the third current path providing electrode formed with a thin line in this way, since the thin line itself cannot transmit ultraviolet rays, characteristics are obtained at the edge portion of the thin line, but the edge portion of the thin line is Since the distance can be long, the sensitivity can be improved.

  Further, according to the ultraviolet sensor according to the present invention, since the ZnO layer is located on the ultraviolet light receiving side, it is possible to increase the absorption efficiency of ultraviolet rays at the interface between the ZnO layer and the (Ni, Zn) O layer. it can.

  In this invention, when a protective film is provided so as to cover the third current path providing electrode, or when the third current path providing electrode is provided in the ZnO layer, the environmental resistance of the ultraviolet sensor can be improved. In addition, surface scratches during manufacture or transportation can be advantageously prevented.

In particular, when the third current path providing electrode is provided in the ZnO layer, in addition to the effects described above, it is possible to suppress changes in dark resistance (resistance in a dark room) under a high humidity environment. Further, in manufacturing the ultraviolet sensor, the ZnO layer may be laminated so that the third current path providing electrode is disposed in the middle of the lamination process for the ZnO layer, and the efficiency of the lamination process is not lowered. In addition, the firing step can be performed integrally with respect to the ZnO layer having the third current path providing electrode formed therein, so that the productivity is not reduced. The same effect is also achieved when a protective film made of Zn ₂ SiO ₄ having the same hexagonal crystal form as ZnO is formed.

  On the other hand, even when the protective film is made of glass or resin, the change in dark resistance under a high humidity environment can be suppressed. Furthermore, by selecting the glass or resin material, the ultraviolet transmittance can be controlled, and as a result, a desired sensitivity wavelength can be obtained.

  An ultraviolet sensor according to the present invention relates to a surface extending in a direction orthogonal to a surface in which the first and second current path providing electrodes extend and passing through a center position of a distance between the first and second current path providing electrodes. If it has a symmetric structure, the aforementioned directionality can be completely eliminated.

  In the ultraviolet sensor according to the present invention, when at least the ZnO layer and the (Ni, Zn) O layer are obtained by integrally sintering, not only efficient production is possible, but also the ZnO layer And the (Ni, Zn) O layer are likely to have fine irregularities, so that the area of the interface becomes large and light is easily absorbed due to irregular reflection, which leads to higher sensitivity. Make it possible.

  FIG. 1 is a sectional view showing an ultraviolet sensor 1 according to a first embodiment of the present invention.

  The ultraviolet sensor 1 is made of an oxide semiconductor containing ZnO, and is provided so as to be in contact with the ZnO layer 2 and the ZnO layer 2, and made of an oxide semiconductor in which ZnO is dissolved in NiO (Ni , Zn) O layer 3 is provided.

  First and second terminal electrodes 5 and 6 are provided on the respective ends of the stacked body 4 facing in the direction in which the ZnO layer 2 and the (Ni, Zn) O layer extend.

  In the (Ni, Zn) O layer 3, first and second current path providing electrodes 7 and 8 that are electrically connected to the first and second terminal electrodes 5 and 6, respectively, are predetermined between each other. Are provided so as to be located on the same plane with a distance 9 therebetween. FIG. 2 is a cross-sectional view of the ultraviolet sensor 1 along the surface on which the first and second current path providing electrodes 7 and 8 are formed.

  On the outer surface of the ZnO layer 2, a third current path providing electrode 10 is provided so as to face the distance 9 between the first and second current path providing electrodes 7 and 8. FIG. 3 is a plan view of the ultraviolet sensor 1 and shows the outer surface of the ZnO layer 2 on which the third current path providing electrode 10 is formed. The third current path applying electrode 10 is provided so as not to be directly connected to any electrode. The third current path applying electrode 10 is formed with a thin line. The third current path applying electrode 10 shown in FIG. 3 is formed by thin lines arranged in a grid pattern.

  As described above, the ZnO layer 2 is made of an oxide semiconductor containing ZnO, and contains, for example, Al, Co, In, Ga, or the like as a doping material while containing ZnO as a main component. The product may contain Fe group, Fe, Ni, Mn, etc., and may contain Zr, Si, etc. as impurities. In particular, Zr may be included as contamination arising from the media during grinding.

The (Ni, Zn) O layer 3 has a composition represented by (Ni _1-x Zn _x ) O, and x is preferably in the range of 0.2 ≦ x ≦ 0.4. . This is because good sensitivity can be obtained stably. When x is less than 0.2, when the (Ni, Zn) O layer 3 and the ZnO layer 2 are obtained by simultaneous firing, a good bonding state may not be obtained between them, or (Ni , Zn) O layer 3 may increase in resistance, and the output of the ultraviolet sensor 1 may decrease. On the other hand, when x exceeds 0.4, when the (Ni, Zn) O layer is obtained by firing, ZnO particles are generated in the (Ni, Zn) O layer 3, and good with the ZnO layer 2 A bonding interface may not be obtained, and the output of the ultraviolet sensor 1 may decrease.

  The (Ni, Zn) O layer 3 is preferably made of a sintered body. When the (Ni, Zn) O layer 3 is composed of a sintered body, fine irregularities are inevitably formed on the surface, that is, the interface with the ZnO layer 2 due to grain growth that occurs during firing. This unevenness increases the effective light receiving area and gives the property of easily absorbing light by irregular reflection, and as a result, the light receiving sensitivity can be increased.

  The ZnO layer 2 described above is also preferably made of a sintered body. This is because when the ZnO layer 2 is composed of a sintered body, it can be obtained by simultaneous firing with the (Ni, Zn) O layer 3 described above, and the productivity of the ultraviolet sensor 1 can be improved.

  Such an ultraviolet sensor 1 is used so that the ZnO layer 2 is positioned on the ultraviolet light receiving side as indicated by an arrow 11 in FIG. 1, and the outer surface of the ZnO layer 2 receives ultraviolet light. It is considered a surface.

  The ultraviolet sensor 1 has a structure in which ZnO as an n-type semiconductor and (Ni, Zn) O as a p-type semiconductor are heterojunction, and the resistance value thereof varies depending on the carriers generated when the ultraviolet rays are irradiated. By detecting this, it operates as a sensor.

  Current paths that can occur in the ultraviolet sensor 1 are “first current path applying electrode 7” → “(Ni, Zn) O layer 3” → “interface between (Ni, Zn) O layer 3 and ZnO layer 2”. → “ZnO layer 2” → “third current path providing electrode 10” → “ZnO layer 2” → “interface between (Ni, Zn) O layer 3 and ZnO layer 2” → “(Ni, Zn) O layer” 3 ”→“ second current path providing electrode 8 ”or“ second current path providing electrode 8 ”→“ (Ni, Zn) O layer 3 ”→“ (Ni, Zn) O ” Interface between layer 3 and ZnO layer 2 ”→“ ZnO layer 2 ”→“ third current path providing electrode 10 ”→“ ZnO layer 2 ”→“ interface between (Ni, Zn) O layer 3 and ZnO layer ” There is a second current path such as “(Ni, Zn) O layer 3” → “first current path providing electrode 7”. These first and second current paths Are opposite to each other, but in both cases, the “interface between (Ni, Zn) O layer 3 and ZnO layer 2”, that is, the barrier between (Ni, Zn) O and ZnO, in the forward and reverse directions. Will flow twice. Since this barrier is homogeneous in the first current path and the second current path, the resistance value does not change in either case. Therefore, according to the ultraviolet sensor 1, the directionality can be eliminated.

  In particular, the ultraviolet sensor 1 according to this embodiment has a completely symmetrical structure. That is, the ultraviolet sensor 1 extends in a direction orthogonal to the plane in which the first and second current path applying electrodes 7 and 8 extend and is the center of the interval between the first and second current path applying electrodes 7 and 8. It has a symmetrical structure with respect to the plane passing through the position. From this, according to the ultraviolet sensor 1 according to this embodiment, the directionality can be completely eliminated.

  Further, according to the ultraviolet sensor 1, the spectral wavelength sensitivity characteristic is flat over a wide wavelength range. The reason is considered as follows.

  The wavelength of ultraviolet light detected by the ultraviolet sensor 1 is determined by the band gap of ZnO which is an n-type semiconductor and the band gap of (Ni, Zn) O which is a p-type semiconductor. Since the band gap of ZnO is about 3.3 eV, the light absorbed by ZnO has a peak near the wavelength of 370 nm. On the other hand, since the band gap of (Ni, Zn) O is about 4 eV, it has an absorption peak in the vicinity of 300 nm. The wavelength of ultraviolet rays detected by the ultraviolet sensor 1 is determined by combining these peak wavelengths.

  In addition to the above-described first or second current path, the ultraviolet sensor 1 has, for example, “first current path application electrode 7” → “(Ni, Zn) O layer 3” → “second current path”. Current paths such as “current path providing electrode 8” or “second current path providing electrode 8” → “(Ni, Zn) O layer 3” → “first current path providing electrode 7” can also be taken. You can take a route. In addition, since the ZnO layer 2, the (Ni, Zn) O layer 3, and the interface between the (Ni, Zn) O layer 3 and the ZnO layer 2 are made of polycrystalline ceramic, It is thought that the gap is wide.

  From these things, according to this ultraviolet sensor 1, it is thought that a spectral wavelength sensitivity characteristic becomes flat over a wide wavelength range.

  In the ultraviolet sensor 1, as described above, the third current path applying electrode 10 is formed with a thin line. Since the third current path applying electrode 10 itself does not transmit ultraviolet rays, characteristics must be obtained at the edge portion. However, if formed with a thin line as described above, the distance between the edge portions can be increased. Therefore, the sensitivity can be improved.

  FIG. 4 is a sectional view showing an ultraviolet sensor 1a according to the second embodiment of the present invention. In FIG. 4, elements corresponding to the elements shown in FIG.

The ultraviolet sensor 1 a shown in FIG. 4 is characterized in that a protective film 14 is provided on the outer surface of the ZnO layer 2 so as to completely cover the third current path providing electrode 10. The protective film 14 is made of, for example, ZnO, Zn ₂ SiO ₄ , glass, or resin. When the protective film 14 is made of ZnO as described above, the third current path providing electrode 10 is provided in the ZnO layers 2 and 14 from another viewpoint. .

  When the protective film 14 is provided, it acts to reduce the light transmittance, and thus it is unavoidable to reduce the spectral sensitivity characteristics. Nevertheless, the environmental resistance of the ultraviolet sensor 1a can be improved. Therefore, it is possible to prevent surface scratches during production and transportation.

When the protective film 14 is made of ZnO, the protective film 14 acts to suppress a change in dark resistance in the high humidity environment of the ultraviolet sensor 1a. If the protective film 14 is made of ZnO, the ZnO layer 2 and the protective film 14 can be formed by integral sintering. In addition to ZnO, it has been confirmed that the same effect as in the case of ZnO can be obtained when Zn ₂ SiO ₄ having the same hexagonal crystal form is used as the material of the protective film 14.

  Further, when the protective film 14 is made of glass or resin, it is possible to control the ultraviolet transmittance by selecting the material, and as a result, the protective film 14 has a function of obtaining a desired sensitivity wavelength. be able to. Moreover, also when the protective film 14 is comprised from glass or resin, the change of the dark resistance in a high-humidity environment can be suppressed.

  FIGS. 5 to 10 are views corresponding to FIG. 3 for explaining the third to eighth embodiments of the present invention, respectively. These third to eighth embodiments provide various modifications of the third current path applying electrode 10. 5 to 10, elements corresponding to those shown in FIG. 3 are denoted by the same reference numerals, and redundant description is omitted.

  The third current path applying electrode 10a shown in FIG. 5 is formed with fine lines arranged in a comb-teeth shape with the comb-teeth oriented in the longitudinal direction of the ZnO layer 2.

  The third current path applying electrode 10b shown in FIG. 6 is formed with fine lines arranged in a mesh shape.

  The third current path providing electrode 10c shown in FIG. 7 is formed with a plurality of thin lines arranged in parallel to each other.

  The third current path applying electrode 10d shown in FIG. 8 is formed with fine lines arranged in a comb shape in a state where the comb teeth are directed in a direction orthogonal to the longitudinal direction of the ZnO layer 2.

  The third current path applying electrode 10e shown in FIG. 9 is formed with a plurality of circular thin lines arranged in the row and column directions.

  The third current path providing electrode 10f shown in FIG. 10 is formed with a plurality of thin lines extending in a meander shape.

  Next, experimental examples carried out to confirm the effects of the present invention will be described.

1. Experimental example 1
First, in order to produce a green sheet to be a ZnO layer, each raw material inorganic powder of ZnO and Al ₂ O ₃ is converted into ZnO and AlO _3/2 , respectively, 99.99 mol% and 0.01 mol %, And pure water was added thereto, and PSZ (partially stabilized zirconia) beads were used as media to carry out a mixing and pulverizing treatment using a ball mill so that the average particle size was 0.5 μm or less.

  Next, the mixed and pulverized slurry was dehydrated and dried, granulated to a particle size of about 50 μm, and calcined at a temperature of 1200 ° C. for 2 hours. Next, pure water was again added to the calcined powder thus obtained, and mixed and pulverized with a ball mill using PSZ beads as a medium until the average particle size became 0.5 μm.

  Next, after the slurry after the mixing and pulverization treatment is dehydrated and dried, an organic solvent and a dispersant are added and mixed, and a binder and a plasticizer are further added to form a molding slurry, and a doctor blade method is applied to this slurry. A green sheet having a thickness of 10 μm to be a ZnO layer was obtained.

  On the other hand, in order to produce a green sheet to be a (Ni, Zn) O layer, the raw material inorganic powders of NiO and ZnO are converted to NiO and ZnO, respectively, so as to be 70 mol% and 30 mol%, respectively. Weighed, pure water was added thereto, and PSZ beads were used as a medium, and mixed and pulverized by a ball mill so that the average particle size was 0.5 μm or less.

  Next, the mixed and pulverized slurry was dehydrated and dried, granulated to a particle size of about 50 μm, and calcined at a temperature of 1200 ° C. for 2 hours. Next, pure water was again added to the calcined powder thus obtained, and the mixture was pulverized using a PSZ bead as a medium until the average particle size became 0.5 μm.

  Next, after the slurry after the mixing and pulverization treatment is dehydrated and dried, an organic solvent and a dispersant are added and mixed, and a binder and a plasticizer are further added to form a molding slurry, and a doctor blade method is applied to this slurry. A green sheet having a thickness of 10 μm to be a (Ni, Zn) O layer was obtained.

  Next, on the ZnO layer green sheet obtained as described above and on a specific one of the (Ni, Zn) O layer green sheets, the first to the patterns shown in FIGS. A Pd paste containing Pd powder as a conductive component was screen printed so that the third current path applying electrodes 7, 8 and 10 were formed, and then dried at a temperature of 60 ° C. for 1 hour.

  Next, in order to obtain the laminate 4 having the structure shown in FIG. 1, the green sheets for the (Ni, Zn) O layer are stacked so as to have a total thickness of 0.5 mm. The (Ni, Zn) O layer green sheets on which the patterns to be the first and second current path applying electrodes 7 and 8 are printed are stacked in a state in which the printed surface faces downward. A ZnO layer green sheet on which a pattern to be the current path application electrode 10 was printed was overlapped with the printing surface facing upward. And after putting the raw laminated body obtained by laminating | stacking these green sheets into a metal mold and crimping | bonding by the pressure of 20 Mpa, it is the dimension and shape which can take out the laminated body 4 of a structure as shown in FIG. Cut.

  Next, the raw laminate cut as described above was degreased slowly and sufficiently at a temperature of 450 ° C., and then fired at a temperature of 1250 ° C. for 5 hours. In this way, a laminated body 4 after sintering having a structure as shown in FIG. 1 was obtained.

  Next, in order to form the first and second terminal electrodes 5 and 6 as shown in FIGS. 1 to 3, the first and second current path applying electrodes 7 and 8 of the laminated body 4 after sintering. An Ag paste containing Ag powder as a conductive component was applied to each end from which each was derived, and baked at a temperature of 800 ° C. for 10 minutes.

With respect to the ultraviolet sensor 1 according to the embodiment of the present invention obtained as described above, a monochromatic light from 600 nm to 200 nm (accuracy: ± 0.1 nm) is applied using a spectroscope in a dark room with a bias voltage of 1V. Was irradiated to the surface on which the third current path providing electrode 10 of the ultraviolet sensor 1 was formed at intervals of 1 nm, and the resistance was examined. And since the intensity | strength of the monochromatic light of each wavelength changes, the intensity | strength of light is measured using the some ultraviolet sensor 1, It converts into the light intensity of 1 mW / cm < ² >, and the resistance change was estimated, and it was set as the sensitivity of the sensor. . The result is shown in FIG.

  On the other hand, as a comparative example, an ultraviolet sensor 21 having a structure as shown in FIG. 11 was produced and evaluated in the same manner as described above. In FIG. 11, elements corresponding to those shown in FIG.

  The ultraviolet sensor 21 shown in FIG. 11 includes a laminate 4 including a ZnO layer 2 and a (Ni, Zn) O layer 3. One current path providing electrode 22 is provided in the (Ni, Zn) O layer 3, and the other current path providing electrode 23 is provided on the outer surface of the ZnO layer 2. The latter current path providing electrode 23 has a pattern formed by the same thin lines as the third current path providing electrode 10 well shown in FIG. A terminal electrode 24 that is electrically connected to the current path applying electrode 22 is provided at one end of the stacked body 4. Further, the current path providing electrode 23 provided on the ZnO layer 2 is used as the other terminal electrode. The sensitivity of such an ultraviolet sensor 21 is shown as a comparative example in FIG.

  Furthermore, the same evaluation was performed for other types of commercially available ultraviolet sensors, that is, GaPAs sensors and diamond sensors. These evaluation results are also shown in FIG.

  In FIG. 12, the sensitivity is a relative comparison because the evaluation method differs between the samples.

  As can be seen from FIG. 12, according to the ultraviolet sensor of the embodiment of the present invention, a flat spectral wavelength sensitivity characteristic is obtained over a wide wavelength range.

  The dark resistance of the ultraviolet sensor 1 according to the embodiment is 10.4 MΩ when a current is passed from the first current path providing electrode 7 to the second current path providing electrode 8, and conversely the second current. When a current was passed from the path providing electrode 8 to the first current path providing electrode 7, it was 10.3 MΩ. This shows that there is substantially no directionality.

  On the other hand, in the ultraviolet sensor 21 according to the comparative example shown in FIG. 11, when a current is passed from the current path providing electrode 23 to the current path providing electrode 22, it is 8.5 MΩ. It was 0.3 MΩ when a current was passed through the path applying electrode 23. From this, it can be seen that the resistance is greatly changed by changing the current direction.

2. Experimental example 2
In Experimental Example 2, in the process of stacking the green sheets in Experimental Example 1, after stacking the ZnO layer green sheets on which the pattern to be the third current path applying electrode 10 was stacked, any electrode was further formed thereon. As shown in FIG. 4, a protective film 14 made of ZnO is provided through the same steps as in Experimental Example 1 except that a green laminate is produced by laminating green sheets for ZnO layers that are not printed. The ultraviolet sensor 1a was obtained.

  And about the ultraviolet sensor 1a provided with the protective film 14 which consists of ZnO in this way, the sensitivity of the sensor was calculated | required by the method similar to the case of Experimental example 1. FIG. The result is shown as “with ZnO protective film” in FIG. 13. FIG. 13 also shows the sensitivity of the ultraviolet sensor 1 according to the “no protective film” embodiment shown in FIG. As can be seen from FIG. 13, the sensitivity of the UV sensor 1a “with ZnO protective film” is slightly lower than that of the UV sensor 1 “without protective film”.

  Moreover, the time-dependent change of dark resistance was also evaluated. The result is shown in FIG. As shown in FIG. 14, according to the UV sensor 1 a with “ZnO protective film”, the change in dark resistance in a high-humidity environment as compared with the UV sensor 1 without “protective film” obtained in Experimental Example 1. Is suppressed. FIG. 14 shows the results of examining the change in dark resistance of an ultraviolet sensor placed in a humidity bath at a temperature of 80 ° C. and a relative humidity of 95% until 1000 hours have passed.

  In FIG. 14, the dark resistance change rate of the protective film made of the epoxy resin formed on the light receiving surface of the ultraviolet sensor 1 obtained in Experimental Example 1 is shown as “with an epoxy resin protective film”. The dark resistance change rate of the protective film made of alkaline glass formed on the light receiving surface of the ultraviolet sensor 1 obtained in Experimental Example 1 is shown as “with glass protective film”. It can be seen that these “with epoxy resin protective film” and “with glass protective film” ultraviolet sensors also have the effect of suppressing changes in dark resistance in a high humidity environment.

It is sectional drawing which shows the ultraviolet sensor 1 by 1st Embodiment of this invention. It is sectional drawing which follows the surface in which the 1st and 2nd electric current path provision electrodes 7 and 8 were formed of the ultraviolet sensor 1 shown in FIG. It is a top view of the ultraviolet sensor 1 shown in FIG. It is sectional drawing which shows the ultraviolet sensor 1a by 2nd Embodiment of this invention. It is a figure equivalent to FIG. 3 for demonstrating the 3rd Embodiment of this invention. It is a figure equivalent to FIG. 3 for demonstrating the 4th Embodiment of this invention. It is a figure equivalent to FIG. 3 for demonstrating the 5th Embodiment of this invention. It is a figure equivalent to FIG. 3 for demonstrating the 6th Embodiment of this invention. It is a figure equivalent to FIG. 3 for demonstrating the 7th Embodiment of this invention. It is a figure equivalent to FIG. 3 for demonstrating 8th Embodiment of this invention. It is sectional drawing which shows the ultraviolet sensor 21 produced as a comparative example in Experimental example 1. FIG. The spectral wavelength sensitivity characteristics of the ultraviolet sensor 1 manufactured as an example in Experimental Example 1 are shown together with the spectral wavelength sensitivity characteristics of the ultraviolet sensor 21 as a comparative example shown in FIG. 11 and commercially available GaPAs-based sensors and diamond-based sensors. FIG. It is a figure which shows the spectral wavelength sensitivity characteristic of the ultraviolet sensor 1a produced in Experimental example 2 with the "ZnO protective film" with the spectral wavelength sensitivity characteristic of the ultraviolet sensor 1 produced in Experimental example 1 without the protective film. The time-dependent change in dark resistance of the “with ZnO protective film” UV sensor 1a manufactured in Experimental Example 2 in a high-humidity environment is shown in the “No protective film” UV sensor 1 and Experimental Example 2 manufactured in Experimental Example 1. It is a figure shown with the time-dependent change of dark resistance of each produced ultraviolet sensor of "with epoxy resin protective film" and "with glass protective film".

Explanation of symbols

DESCRIPTION OF SYMBOLS 1,1a Ultraviolet sensor 2 ZnO layer 3 (Ni, Zn) O layer 4 Laminated body 5 1st terminal electrode 6 2nd terminal electrode 7 1st current path provision electrode 8 2nd current path provision electrode 9 Space | interval 10 , 10a to 10f Third current path providing electrode 11 Arrow indicating ultraviolet irradiation direction 14 Protective film

Claims (6)

A ZnO layer made of an oxide semiconductor containing ZnO;
A layered product including an (Ni, Zn) O layer, which is provided in contact with the ZnO layer and is made of an oxide semiconductor in which ZnO is dissolved in NiO;
A first terminal electrode and a second terminal electrode are provided on each end of the stacked body facing each other in a direction in which the ZnO layer and the (Ni, Zn) O layer extend.
In the (Ni, Zn) O layer, first and second current path providing electrodes electrically connected to the first and second terminal electrodes, respectively, are spaced apart from each other by a predetermined distance. Provided to be on the same plane,
On the outer surface of the ZnO layer, there is provided a third current path providing electrode which is formed with a thin line so as to face the interval between the first and second current path providing electrodes and which is not directly connected to any electrode. Provided,
The ZnO layer is used to be positioned on the ultraviolet light receiving side.
UV sensor.   The ultraviolet sensor according to claim 1, further comprising a protective film provided on the outer surface of the ZnO layer so as to completely cover the third current path providing electrode. The ultraviolet sensor according to claim 2, wherein the protective film is made of ZnO, Zn ₂ SiO ₄ , glass, or resin. A ZnO layer made of an oxide semiconductor containing ZnO;
A layered product including an (Ni, Zn) O layer, which is provided in contact with the ZnO layer and is made of an oxide semiconductor in which ZnO is dissolved in NiO;
A first terminal electrode and a second terminal electrode are provided on each end of the stacked body facing each other in a direction in which the ZnO layer and the (Ni, Zn) O layer extend.
In the (Ni, Zn) O layer, first and second current path providing electrodes electrically connected to the first and second terminal electrodes, respectively, are spaced apart from each other by a predetermined distance. Provided to be on the same plane,
In the ZnO layer, there is provided a third current path providing electrode which is formed with a thin line so as to face the interval between the first and second current path providing electrodes and which is not directly connected to any electrode,
The ZnO layer is used to be positioned on the ultraviolet light receiving side.
UV sensor.   Having a symmetric structure with respect to a plane extending in a direction orthogonal to a plane in which the first and second current path application electrodes extend and passing through a center position of a distance between the first and second current path application electrodes; The ultraviolet sensor according to claim 1.   The ultraviolet sensor according to claim 1, wherein at least the ZnO layer and the (Ni, Zn) O layer are obtained by integrally sintering them.

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