JP2024024376A - Electrical measurement type surface plasmon resonance sensor and electrical measurement method using the same - Google Patents

Abstract

An object of the present invention is to provide an electrical measurement type SPR sensor whose manufacturing process is not complicated and which can reduce costs. SOLUTION: The SPR sensor 100A is a transparent sensor having a first main surface 121 and a second main surface 122 that are perpendicular to the thickness direction, and a side surface 123 that connects the respective peripheral edges of the first main surface 121 and the second main surface 122. It is formed on a substrate 120 and a first main surface 121 of the transparent substrate 120, and has an electrode film 131, a silicon semiconductor film 132, and a plasmon resonance film 133, which are stacked in this order on the first main surface 121. A sensor chip 140 having a sensor section 130 configured to An electrical measurement device 150 is provided. Furthermore, an incident side surface 123a through which light is incident is formed on a side surface 123 of the transparent substrate 120. [Selection diagram] Figure 1

Description

The present disclosure relates to an electrical measurement type surface plasmon sensor and an electrical measurement method using the same.

Surface plasmon resonance (SPR) refers to a state in which free electrons on a metal surface cause collective oscillations (plasma oscillations). SPR includes Propagating Surface Plasmon Resonance (PSPR), which propagates on metal surfaces, and Localized Surface Plasmon Resonance (LSPR), which localizes in nanometer-sized metal structures. And, is included.

PSPR is a resonance phenomenon caused by the interaction between incident light and an electric field generated around free electrons that cause plasma oscillations on a metal surface. When PSPR is excited, an electron compression wave (SPP: Surface Plasmon Polariton), which is a combination of plasma vibration and electromagnetic waves traveling along the interface, propagates along the metal surface. LSPR is a phenomenon in which metal nanostructures such as metal nanoparticles are polarized and induced by plasma vibration to generate electric dipoles.

A surface plasmon resonance sensor (SPR sensor) has been developed that uses SPR to detect the amount of change in the refractive index of a sample. Generally, an SPR sensor has a plasmon resonance film made of a thin metal film and a prism. By making light incident on one surface of the plasmon resonance film through the prism of the SPR sensor and measuring the intensity of reflected light while changing the incident angle of the light, it is possible to detect a specific incident angle (plasmon resonance) in the total reflection area of the light. It is possible to obtain an incident angle-reflectance curve in which the reflected light intensity becomes minimum at the resonance angle). Since the incident angle-reflectance curve changes depending on the refractive index of the sample, the amount of change in the refractive index of the sample can be detected based on the obtained incident angle-reflectance curve.

Patent Document 1 discloses an electrical measurement type SPR sensor. FIG. 4 shows a conventional electrical measurement type SPR sensor disclosed in Patent Document 1. As shown in FIG. 4, an electrical measurement type SPR sensor 500 disclosed in Patent Document 1 includes a prism 510, a sensor chip 540 having a transparent substrate 520 and a sensor section 530, and an electrical measurement device 550.

A transparent substrate 520 of a sensor chip 540 is disposed on the prism 510, and a sensor section 530 is disposed on the transparent substrate 520. The sensor section 530 includes an electrode film 531 (for example, an ITO electrode film), a silicon semiconductor film 532, and a plasmon resonance film 533, which are stacked in this order on the transparent substrate 520. The electrical measurement device 550 is electrically connected to the electrode film 531 and the plasmon resonance film 533 of the sensor section 530, and is configured to be able to measure the current flowing between the connection terminals or the voltage between the connection terminals. Ru.

In the electrometric SPR sensor 500 disclosed in Patent Document 1, when light is incident from the slope of the prism 510 as shown in FIG. 4, the incident light passes through the transparent substrate 520, the electrode film 531, and the silicon semiconductor film 532. and reaches the plasmon resonance membrane 533. By adjusting the angle of incidence of light on the plasmon resonance film 533 to be equal to or greater than the critical angle, the incident light is totally reflected on the plasmon resonance film 533. When the evanescent waves generated at this time interact with the plasmon resonance film 533, surface plasmon resonance is excited. When surface plasmon resonance is excited, the energy of the incident light is taken away, so the intensity of the reflected light decreases.

Further, the silicon semiconductor film 532 generates power when the incident light and its reflected light pass through the silicon semiconductor film 532. The magnitude of this power generation is measured by electrical measuring device 550, for example as current or voltage. Here, when surface plasmon resonance is excited as described above, the intensity of the reflected light decreases, so the magnitude of power generation due to the reflected light passing through the silicon semiconductor film 532 also decreases. That is, the magnitude of power generation due to light passing through the silicon semiconductor film 532 is influenced by the presence or absence of excitation of surface plasmon resonance.

Therefore, when light is incident on the prism 510 at an incident angle that excites surface plasmon resonance when the sample S is disposed on the surface of the plasmon resonance membrane 533, the electrical measuring device 550 detects the electric power. Analyze sample S by measuring the magnitude (e.g. current) and measuring the magnitude with different samples (for example, detecting the amount of change in refractive index (refractive index difference) between sample S and other samples) )can do.

International Publication No. 2021/075529

(Problem to be solved by the invention)
When manufacturing the electrometric SPR sensor 500 disclosed in Patent Document 1, an electrode film 531, a silicon semiconductor film 532, and a plasmon resonance film 533 are formed in this order on one main surface of the transparent substrate 520. Thereafter, the prism 510 is disposed on the other main surface of the transparent substrate 520. At this time, in order to prevent an air layer from intervening between the transparent substrate 520 and the prism 510, a refractive index adjusting liquid (for example, diiodomethane) is actually dropped on the prism 510, and the dropped refractive index adjusting liquid is interposed. Prism 510 and transparent substrate 520 are brought into close contact.

If it is necessary to interpose the refractive index adjustment liquid between the prism 510 and the transparent substrate 520 as described above, the manufacturing process of the SPR sensor becomes complicated. In order to fabricate an SPR sensor without using a refractive index adjustment liquid, it is possible to use the prism itself as a substrate for film formation, but since the prism must be custom-made, the cost will rise, and for example, it may be necessary to use a disposable one. It cannot be used as an SPR sensor.

An object of the present invention is to provide an electrical measurement type SPR sensor whose manufacturing process is not complicated and which can reduce costs, and an electrical measurement method using the same.

The present disclosure provides a transparent substrate having a first main surface (121) and a second main surface (122) perpendicular to the thickness direction, and a side surface (123) connecting the respective peripheral edges of the first main surface and the second main surface. (120), is formed on the first main surface of the transparent substrate, and has an electrode film (131), a silicon semiconductor film (132), and a plasmon resonance film (133), which are arranged on the first main surface in this order. A sensor chip (140) having a sensor part (130) configured to be stacked on top of the sensor chip (140) is electrically connected to an electrode film and a plasmon resonance film, and is generated by power generation in a silicon semiconductor film. An electrical measuring surface plasmon resonance sensor (100A, 100B) comprising an electrical measuring device (150) that measures current or voltage, and an incident side surface (123a) through which light enters is formed on the side surface of a transparent substrate. I will provide a.

In this case, the angle between the film surface of the plasmon resonance film and the incident side surface may be approximately 90°.

The present disclosure also provides an electrical measurement method using the above electrical measurement type surface plasmon resonance sensor (100A, 100B), in which light is incident from the incident side surface (123a) and the incident light is transmitted to the plasmon resonance membrane ( 133) and the plasmon resonance film is totally reflected by the plasmon resonance film. An electrical measurement method is provided, which includes the step of measuring, using an electrical measurement device (140), a current or voltage generated by power generation in a silicon semiconductor film while the light is being incident on the silicon semiconductor film.

In this case, the predetermined incident angle is configured to be predetermined as an angle at which surface plasmon resonance is excited by interaction between the plasmon resonance film and an evanescent wave generated by total reflection of light incident on the plasmon resonance film. You can also.

According to the present disclosure, the prism can be omitted by allowing light to enter from the incident side of the transparent substrate. Therefore, there is no need to drop a refractive index adjustment liquid between the transparent substrate and the prism, so the manufacturing process can be simplified. Furthermore, since no prism is used, the cost of the electrical measurement type surface plasmon resonance sensor can be reduced.

Further, the present disclosure has a first main surface (221) and a second main surface (222) perpendicular to the thickness direction, and a side surface (223) connecting the respective peripheral edges of the first main surface and the second main surface. A transparent substrate (220), a plasmon resonance film (225) formed on the first main surface of the transparent substrate, an electrode film (231), and a silicon semiconductor film (232) formed on the second main surface of the transparent substrate. ) and a reflective conductive film (233), a power generation unit (230) configured such that these are stacked in this order; It includes an electrical measuring device (250) that is electrically connected and measures the current or voltage generated by power generation in the silicon semiconductor film, and has an incident side surface (223a) on the side surface of the transparent substrate through which light is incident. An electrometric surface plasmon resonance sensor (200A, 200B) is provided.

In this case, the angle between the membrane surface of the plasmon resonance membrane and the incident side surface may be approximately 90 degrees.

The present disclosure also provides an electrical measurement method using the electrical measurement type surface plasmon resonance sensor (200A, 200B), in which light is incident from the incident side surface (223a) and the incident light is transmitted to a silicon semiconductor film (200A, 200B). The light reaches the plasmon resonance film (225) before passing through the plasmon resonance film (232) and is made incident on the incident side surface at a predetermined incident angle so that the light that reaches the plasmon resonance film is totally reflected by the plasmon resonance film. and a step of measuring, with an electrical measuring device (250), the current or voltage generated by power generation in the silicon semiconductor film (232) when light is incident on the incident side surface at a predetermined incident angle. , provides an electrical measurement method.

In this case, the predetermined incident angle is configured to be predetermined as an angle at which surface plasmon resonance is excited by interaction between the plasmon resonance film and an evanescent wave generated by total reflection of light incident on the plasmon resonance film. You can also.

According to the above disclosure, the prism can be omitted by allowing light to enter from the incident side of the transparent substrate. Therefore, there is no need to drop a refractive index adjustment liquid between the transparent substrate and the prism, so the manufacturing process can be simplified. Furthermore, since no prism is used, the cost of the electrical measurement type surface plasmon resonance sensor can be reduced.

Furthermore, according to the above disclosure, the light incident from the transparent substrate can be caused to enter the plasmon resonance film before the light enters the silicon semiconductor film. For this reason, the magnitude of the power measured by the electrical measuring device when surface plasmon resonance is occurring in the plasmon resonant membrane, and the magnitude of the power measured by the electrical measuring device when surface plasmon resonance is not occurring in the plasmon resonating membrane. It is possible to further increase the difference between the amount of power and the amount of power that is generated. Thereby, the sensitivity of the electrometric surface plasmon resonance sensor can be significantly improved.

FIG. 1 shows a schematic configuration of an electrometric surface plasmon resonance sensor according to a first embodiment. FIG. 2 shows a schematic configuration of another SPR sensor according to the first embodiment. FIG. 3 shows how light is reflected when the light is incident from the second main surface of the transparent substrate of the SPR sensor according to the first embodiment. FIG. 4 shows a conventional electrometric SPR sensor. FIG. 5 is a graph showing simulation results of an incident angle-current value curve obtained when a measurement process is performed while changing the external incident angle using the SPR sensor shown in FIG. FIG. 6 is a graph showing simulation results of an incident angle-current value curve when light is incident from the slope of the prism using a conventional SPR sensor using the prism shown in FIG. FIG. 7 is an enlarged view of the vicinity of point E2 of graph E in FIG. FIG. 8 is an enlarged view of the vicinity of point F2 of graph F in FIG. FIG. 9 shows a schematic configuration of an SPR sensor according to the second embodiment. FIG. 10 shows a schematic configuration of an SPR sensor according to another example of the second embodiment. FIG. 11A shows simulation results of the incident angle-current value curve for the SPR sensor according to the first embodiment. FIG. 11B shows a graph obtained by normalizing the graph of FIG. 11A based on the critical angle. FIG. 12A is a graph showing simulation results of an incident angle-current value curve obtained when the measurement process is performed while changing the incident angle using the SPR sensor according to the second embodiment. FIG. 12B shows a graph obtained by normalizing the graph of FIG. 12A based on the critical angle. FIG. 13A is a schematic diagram showing how the SPR sensor according to the first embodiment is irradiated with laser light from the laser oscillation device. FIG. 13B is a schematic diagram showing how the SPR sensor according to the second embodiment is irradiated with laser light from the laser oscillation device. FIG. 14 shows an incident angle-current value curve created based on current values actually measured when using the SPR sensor according to Example 1. FIG. 15 shows an incident angle-current value curve created based on actually measured current values when using the SPR sensor according to Example 2.

Embodiments of the present invention will be described below with reference to the drawings.

(First embodiment)
FIG. 1 shows a schematic configuration of an electrometric surface plasmon resonance sensor (hereinafter simply referred to as SPR sensor) 100A according to the first embodiment. As shown in FIG. 1, the SPR sensor 100A according to this embodiment includes a sensor chip 140 having a transparent substrate 120 and a sensor section 130, and an electrical measuring device 150.

The transparent substrate 120 has a function of supporting the sensor section 130. The material of the transparent substrate 120 is not particularly limited as long as it can transmit light, and may be, for example, glass, plastic, or a polymeric organic compound such as a film. A glass substrate is preferably used as the transparent substrate 120.

The transparent substrate 120 is formed into a thin plate shape, and has a rectangular parallelepiped external shape in this embodiment. The transparent substrate 120 has a hexahedral outer surface including a first main surface 121 as the front surface, a second main surface 122 as the back surface, and four side surfaces 123. Both the first main surface 121 and the second main surface 122 have the same rectangular shape and face each other in the thickness direction. The four side surfaces 123 are planes that connect peripheral edges (four sides of each) of the first principal surface 121 and the second principal surface 122 that face each other in the thickness direction. The distance between the first principal surface 121 and the second principal surface 122 represents the thickness of the transparent substrate 120, and the first principal surface 121 and the second principal surface 122 are planes perpendicular to the thickness direction, and the four The side surface 123 is a plane parallel to the thickness direction. One of the four side surfaces 123 of the transparent substrate 120 is the incident side surface 123a. The entrance side surface 123a is mirror polished. That is, on the side surface 123 of the transparent substrate 120, a mirror-polished incident side surface 123a is formed. The shape of the transparent substrate 120 is not particularly limited as long as it has a first main surface 121, a second main surface 122, and a side surface 123. For example, a polygonal columnar transparent substrate can also be used. Furthermore, the thickness of the transparent substrate 120 is not particularly limited, although it is preferable that the transparent substrate 120 has a thin plate shape. Here, "thin plate shape" is defined as a shape in which the representative diameter (for example, circumscribed circle diameter or geometric mean diameter), maximum diameter, or circumference of the first principal surface 121 or the second principal surface 122 is larger than the thickness. I can do it.

The sensor section 130 is formed (film-formed) on the first main surface 121 of the transparent substrate 120 . The sensor section 130 includes an electrode film 131, a silicon semiconductor film 132, and a plasmon resonance film 133. The sensor section 130 is formed by laminating an electrode film 131, a silicon semiconductor film 132, and a plasmon resonance film 133 in this order on the first main surface 121 of the transparent substrate 120, as shown in FIG.

The electrode film 131 is formed on the first main surface 121 of the transparent substrate 120 . The material for the electrode film 131 can be appropriately selected from those conventionally used as electrodes in the semiconductor field. For example, copper (Cu), gold (Au), silver (Ag), platinum (Pt), zinc (Zn), chromium (Cr), aluminum (Al), titanium (Ti), titanium nitride (TiN), ITO ( Examples of the material for the electrode film 131 include transparent conductive materials such as indium tin oxide, FTO (fluorine-doped tin oxide), and metal oxides such as ZnO doped with other elements (aluminum, gallium, etc.).

It is desirable that the electrode film 131 be made of a transparent conductive film that can transmit as much light as possible. The light transmittance of the electrode film 131 is preferably 40% or more, more preferably 50% or more, and 60% or more when light with a wavelength of 400 to 1500 nm is vertically incident. It is more preferable that Further, the thickness of the electrode film 131 is preferably 1 to 1000 nm.

The method for forming the electrode film 131 is not particularly limited, but a method of forming the electrode film 131 on the first main surface 121 of the transparent substrate 120 by sputtering can be exemplified.

The silicon semiconductor film 132 is a film made of silicon semiconductor. The silicon semiconductor film 132 is configured to have a function of absorbing incident light and generating electricity. In this case, the silicon semiconductor film 132 may be a crystalline silicon semiconductor formed by joining a P-type silicon semiconductor and an N-type silicon semiconductor, or a non-doped silicon semiconductor between the P-type silicon semiconductor and the N-type silicon semiconductor. It may also be an amorphous silicon semiconductor with a semiconductor interposed therebetween. Note that when an amorphous silicon semiconductor is used, an IN-type silicon semiconductor may be used without the P-type silicon semiconductor. Examples of elements to be doped into an N-type silicon semiconductor include phosphorus (P), antimony (Sb), and arsenic (As), and examples of elements to be doped into a P-type silicon semiconductor include boron (B), aluminum (Al), and gallium ( (Ga) can be exemplified.

Further, the silicon semiconductor film 132 has a property of being able to transmit light. The light transmittance of such a silicon semiconductor film 132 is preferably 1 to 80%, and preferably 5 to 70% when light with a wavelength of 400 to 1500 nm is vertically incident. More preferably, it is 5 to 50%. Furthermore, the light transmittance of the silicon semiconductor film 132 is the light transmittance when light with a wavelength of 400 to 700 nm is vertically incident, preferably when light with a wavelength of 675 nm is vertically incident. The transmittance is preferably 1 to 70%, more preferably 5 to 70%, even more preferably 5 to 50%.

The thickness of the silicon semiconductor film 132 is preferably 1000 nm or less, more preferably 1 to 1000 nm, even more preferably 5 to 750 nm, and even more preferably 10 to 500 nm. If the thickness of the silicon semiconductor film 132 is less than 1 nm, the silicon semiconductor cannot exist as a film and will not function adequately as a semiconductor. On the other hand, when the thickness of the silicon semiconductor film 132 exceeds 1000 nm, the light transmittance decreases, the light intensity reaching the plasmon resonance film 133 becomes small, and plasmon resonance tends to be difficult to occur.

The silicon semiconductor film 132 is formed on the electrode film 131 formed on the first main surface 121 of the transparent substrate 120 . Although the method for forming the silicon semiconductor film 132 is not particularly limited, for example, a method of forming the silicon semiconductor film 132 on the electrode film 131 by sputtering or a CVD method can be exemplified.

The plasmon resonance film 133 is a film-like body made of a plasmonic material that can generate surface plasmon resonance when incident light is totally reflected. Furthermore, the plasmon resonance membrane 133 is made of a material that can function as a counter electrode to the electrode membrane 131. Examples of materials for the plasmon resonance film 133 include metals, metal nitrides, and metal oxides, and one of these may be used alone, or a composite material may be used in which two or more of these are used. Preferred metals for the material of the plasmon resonance membrane 133 include gold (Au), silver (Ag), aluminum (Al), copper (Cu), platinum (Pt), palladium (Pd), zinc (Zn), and sodium (Na ) can be exemplified. Titanium nitride (TiN) can be exemplified as a metal nitride preferable for the material of the plasmon resonance film 133. Preferred metal oxides for the material of the plasmon resonance film 133 include ITO (indium tin oxide), FTO (fluorine-doped tin oxide), and ZnO doped with other elements (aluminum, gallium, etc.). Among these, the material of the plasmon resonance membrane 133 is preferably at least one selected from the group consisting of Au, Ag, Al, Cu, Pt, Pd, and TiN; More preferably, it is at least one selected from the group consisting of:

Further, the thickness of the plasmon resonance film 133 is preferably 200 nm or less, more preferably 1 to 200 nm, even more preferably 1 to 150 nm, even more preferably 5 to 100 nm, Even more preferably it is 10 to 60 nm. If the thickness of the plasmon resonance film 133 is less than 1 nm, the plasmon resonance film 133 tends to be unable to exist as a film. On the other hand, if the thickness of the plasmon resonance film 133 exceeds 200 nm, the evanescent waves that may be generated on the surface opposite to the incident surface of the incident light become weak, making it impossible to excite sufficient surface plasmon resonance (especially surface plasmon polariton). There is a tendency. In addition, the thickness of the plasmon resonance film 133 tends to make it possible to measure a wider range of refractive indexes (preferably in the range of 1.33 to 1.40) as the refractive index of the sample S to be measured. It is preferable that the wavelength is from 10 to 34 nm. Further, the thickness of the plasmon resonance film 133 is preferably 35 to 60 nm from the viewpoint of increasing the rate of change in the current value with respect to the change in the refractive index of the sample S.

The plasmon resonance film 133 is formed on the silicon semiconductor film 132 that is formed on the electrode film 131 that is formed on the first main surface 121 of the transparent substrate 120 . The method for forming the plasmon resonance film 133 is not particularly limited, but for example, a method for forming the plasmon resonance film 133 on the silicon semiconductor film 132 by sputtering can be exemplified.

The electrical measurement device 150 is electrically connected to the electrode film 131 and the plasmon resonance film 133 of the sensor unit 130, and has a function of measuring the current flowing between the connection terminals or the voltage between the connection terminals. Each connection terminal of this electrical measuring device 150 is electrically connected to the electrode film 131 and the plasmon resonance film 133, respectively, by a connecting lead wire. Therefore, the electrical measurement device 150 can measure the current or voltage obtained by power generation in the silicon semiconductor film 132 sandwiched between the electrode film 131 and the plasmon resonance film 133, which are respectively connected to two connection terminals. can. Examples of the material for the connecting wire include known materials such as platinum, gold, palladium, iron, copper, and aluminum. Further, the electrical measuring device 150 is not particularly limited as long as it can measure voltage values or current values, and examples include a semiconductor device analyzer, a current measuring device, and a voltage measuring device.

FIG. 2 shows a schematic configuration of another SPR sensor 100B according to this embodiment. The sensor section 130' of the SPR sensor 100B shown in FIG. 2 further includes an adhesive layer 135 in addition to the structure of the sensor section 130 shown in FIG. The adhesive layer 135 is provided between the silicon semiconductor film 132 and the plasmon resonance film 133, and has a function of preventing the plasmon resonance film 133 from peeling off. Examples of the material of the adhesive layer 135 include titanium (Ti), chromium (Cr), nickel (Ni), and titanium nitride (TiN), and when the silicon semiconductor film 132 is made of a silicon semiconductor film other than non-doped silicon, A non-doped silicon film may be the adhesive layer. The adhesive layer 135 may be a single layer containing one of these types, or a multilayer formed by laminating two or more of these types. Further, the adhesive layer 135 does not need to cover the entire interface between the silicon semiconductor film 132 and the plasmon resonance film 133, as long as it is provided to such an extent that peeling of the plasmon resonance film 133 can be prevented. The SPR sensor 100B has the same configuration as the SPR sensor 100A except that the adhesive layer 135 is provided on the sensor section 130'. Therefore, the other components are given the same reference numerals as those shown in the SPR sensor 100A of FIG. 1, and the explanation thereof will be omitted.

When the adhesive layer 135 is interposed between the silicon semiconductor film 132 and the plasmon resonance film 133, the intensity of the incident light is attenuated by the adhesive layer 135, resulting in an evanescent wave generated by total reflection of the light at the plasmon resonance film 133. tends to become weaker and unable to excite surface plasmon resonance with sufficient strength. Therefore, the thinner the adhesive layer 135 is, the better, preferably 25 nm or less, more preferably 1 to 25 nm, and even more preferably 1 to 10 nm.

In addition, as shown in FIGS. 1 and 2, the incident side surface 123a of the transparent substrate 120 is located on the film surface of the plasmon resonance film 133 (the plane on which the plasmon resonance film 133 spreads in a film shape, the bottom surface in FIGS. 1 and 2). The surface is almost perpendicular to the surface. In other words, the angle between the film surface of the plasmon resonance film 133 and the incident side surface 123a is approximately 90°. The term "approximately 90°" here includes an angle that varies from 90° within a range of manufacturing error or design error.

A sample S for measurement is placed on the surface of the plasmon resonance membrane 133. Then, with the sample S disposed on the surface of the plasmon resonance membrane 133, electrical measurement is performed by the electrical measuring device 150 using the SPR sensor 100A or 100B. The electrical measurement method in this case includes an input step and a measurement step. In the incident step, light is incident from the incident side surface 123a of the transparent substrate 120, the incident light reaches the plasmon resonance film 133, and the light that reaches the plasmon resonance film 133 is totally reflected by the plasmon resonance film 133. Light is made incident on the incident side surface 123a at a predetermined incident angle (external incident angle θout). In the measurement step, the electrical measuring device 150 measures the current or voltage generated by power generation in the silicon semiconductor film 132 while the light is incident on the incident side surface 123a at the predetermined incident angle.

By performing the incident step, the light incident on the SPR sensors 100A, 200A from the incident side surface 123a of the transparent substrate 120 passes through the transparent substrate 120, the electrode film 131, and the silicon semiconductor film 132, and reaches the plasmon resonance film 133. do. Further, when the light reaching the plasmon resonance film 133 is totally reflected, an evanescent wave is generated that leaks out to the surface side (upper surface side) of the plasmon resonance film 133. When the incident angle (internal incidence angle θin) of light to the plasmon resonance film 133 reaches a specific incident angle (plasmon resonance angle θr), the evanescent wave and the plasmon resonance film 133 interact to strongly excite surface plasmon resonance. Ru.

Further, when the light incident on the SPR sensors 100A and 100B passes through the silicon semiconductor film 132, conduction electrons and holes are generated due to the internal photoelectric effect in the PIN junction structure, PN junction structure, or IN junction structure of the silicon semiconductor film 132. When these particles move, photovoltaic force is generated. In other words, it generates electricity. The generated power generated in this way is measured as a current value or a voltage value by the electrical measuring device 150 in a measuring step.

The magnitude of the electric power (current value or voltage value) generated by the silicon semiconductor film 132 increases as the intensity of light passing through the silicon semiconductor film 132 increases. Here, when the incident angle (internal incidence angle θin) of the light to the plasmon resonance film 133 is at or near the plasmon resonance angle θr, a part of the incident light enters the plasmon resonance film 133 due to surface plasmon resonance. is greatly absorbed. Therefore, the intensity of the reflected light is greatly reduced. Therefore, when surface plasmon resonance is occurring, that is, when the internal incident angle θin is at or near the plasmon resonance angle θr, the magnitude of the power (for example, current) measured by the electrical measuring device 150 is extremely low. tends to become smaller.

The plasmon resonance angle θr changes depending on the refractive index of the sample S on the surface of the plasmon resonance film 133. Therefore, by specifying the plasmon resonance angle θr, the refractive index of the sample S disposed on the plasmon resonance film 133 can be specified. In addition, by measuring the difference (Δθ) in the plasmon resonance angle θr between the case where a standard sample (for example, water) is arranged and the case where the measurement sample S is arranged, it is possible to The amount of change in refractive index can be detected. Further, the internal incident angle θin or the external incident angle θout (the incident angle of light at the incident side surface 123a of the transparent substrate 120) is fixed in advance to an angle at which plasmon resonance is excited, and the standard sample is placed on the plasmon resonance film 133. The magnitude of power (for example, current) measured by the electrical measuring device 150 when placed on the surface of the plasmon resonance membrane 133 and the magnitude of the electric power measured by the electrical measuring device 150 when the sample S is placed on the surface of the plasmon resonance membrane 133. The amount of change in the refractive index of the sample S with respect to the refractive index of the standard sample can also be detected by measuring the difference ΔL from the magnitude of the electric power (for example, current) applied.

Here, the SPR sensors 100A and 100B according to this embodiment do not include a prism, as can be seen from FIGS. 1 and 2. In this embodiment, light is incident not from the back surface (second main surface 122) of the transparent substrate 120 but from the side surface 123 (incident side surface 123a) of the transparent substrate 120.

FIG. 3 is a diagram showing how light is reflected when the light is incident from the second main surface 122, which is the back surface of the transparent substrate 120 of the SPR sensor 100A. As shown in FIG. 3, the light incident on the transparent substrate 120 from the second principal surface 122 is refracted so that the refraction angle θb becomes smaller than the external incidence angle θout.

Further, the light refracted by the second main surface 122 of the transparent substrate 120 reaches the plasmon resonance film 133 via the electrode film 131 and the silicon semiconductor film 132. Here, in order to prevent light from being totally reflected by the electrode film 131 and the silicon semiconductor film 132, the refractive index of these films is set to be the same as or larger than the refractive index of the transparent substrate 120. Therefore, the light incident from the transparent substrate 120 enters the plasmon resonance film 133 at an internal incident angle θin that is less than the refraction angle θb.

Further, the critical angle θc at the interface between the plasmon resonance film 133 and the silicon semiconductor film 132 is determined by the following equation (1).
θc=sin ⁻¹ (n _s /n _si ) (1)
Here, n _s is the refractive index of the sample s, and n _si is the refractive index of the silicon semiconductor film 132. Note that since the plasmon resonance film 133 is extremely thin, the refractive index of the plasmon resonance film 133 can be ignored in the above equation (1). Therefore, the critical angle θc in equation (1) above can be said to be the critical angle of the interface between the sample s and the silicon semiconductor film 132, and can be determined from the refractive index n _s of the sample s and the refractive index n _si of the silicon semiconductor film 132. I can do it.

When the refractive index n _si of the silicon semiconductor film 132 is equal to the refractive index of the transparent substrate 120 and the sample s is air, the internal incident angle θin becomes the critical angle θc when the external incident angle θout is 90°. On the other hand, when the sample s is water or an aqueous solution, the refractive index n _s of the sample s is larger than the refractive index of air, so the critical angle θc becomes larger than when the sample s is air. Therefore, no matter how the external incident angle θout is adjusted, the internal incident angle θin cannot be made equal to or greater than the critical angle θc. That is, in the case of FIG. 3, the variable range of the internal incident angle θin is limited to the angle range less than the critical angle θc, so it is impossible to realize a state in which the internal incident angle θin is greater than or equal to the critical angle θc. Therefore, when light is incident from the second main surface 122 of the transparent substrate 120, it is basically impossible to cause the light to be totally reflected by the plasmon resonance film 133.

On the other hand, as shown in FIG. 1 or FIG. 1 and 2) and the incident direction of light, the refraction angle θb and the internal incidence angle θin are larger than the external incidence angle θout. Therefore, by varying the external incident angle θout, the variable range of the internal incident angle θin can be adjusted to an angular range that includes the critical angle θc. Therefore, the internal incidence angle θin can be set larger than the critical angle θc. Therefore, the light can be totally reflected by the plasmon resonance film 133, and the internal incident angle θin can be set so as to cause sufficient plasmon resonance.

FIG. 5 is a graph showing simulation results of an incident angle-current value curve obtained when a measurement process is performed using the SPR sensor 100A shown in FIG. 1 while changing the external incident angle θout. Here, the incident angle-current value curve corresponds to the incident angle-reflectance curve described above, and FIG. 5 shows the relationship between the external incident angle θout and the current value measured by the electrical measuring device 150. represent. Further, FIG. 6 is a graph showing simulation results of an incident angle-current value curve when light is incident from the slope of the prism 510 using the conventional SPR sensor 500 using the prism 510 shown in FIG. . 5 and 6, the horizontal axis is the incident angle of light to the transparent substrate 120 or the prism 510 (external incident angle θout), and the vertical axis is the relative amount of current value detected by the electrical measuring device 150 ( %). In FIG. 5, the relative amount of this current value is specifically calculated as the ratio of the amount of light absorption (absorbed light amount) contributing to the current to the amount of incident light. Note that the external incidence angle θout in FIGS. 5 and 6 is the angle between the incident direction of light incident on the transparent substrate 120 or the prism 510 and the perpendicular to the film surface of the plasmon resonance film 133 or 533.

In addition, in FIGS. 5 and 6, graph A indicates that the refractive index of the transparent substrate 120 (or prism 510) is 1.450, and graph B indicates that the refractive index of the transparent substrate 120 (or prism 510) is 1.500. In graph C, the refractive index of the transparent substrate 120 (or prism 510) is 1.550, in graph D, the refractive index of the transparent substrate 120 (or prism 510) is 1.600, and in graph E, the refractive index of the transparent substrate 120 (or prism 510) is 1.600. ) has a refractive index of 1.650, graph F has a refractive index of transparent substrate 120 (or prism 510) of 1.700, graph G has a refractive index of transparent substrate 120 (or prism 510) of 1.750, and graph H is each incident angle-current value curve when the refractive index of the transparent substrate 120 (or prism 510) is 1.80.

Furthermore, each of the graphs A to H consists of a pair of graphs. One of the pair of graphs represents the incident angle-current value curve when water (refractive index 1.333) is placed as a standard sample on the surface of the plasmon resonance membrane 133 or 533, and the other of the pair of graphs , represents an incident angle-current value curve when a substance with a refractive index of 1.34 (for example, an aqueous solution with an adjusted concentration of sucrose) is disposed on the surface of the plasmon resonance film 133 or 533.

In the graphs A, B, C, D, and E of FIG. 5, there are points A1, B1, C1, D1, and E1 that are convex upward. The external incidence angle θout indicated by these points is the total reflection start angle θs, which is the external incidence angle corresponding to the critical angle of light incident on the plasmon resonance film 133. The external incident angle range larger than the total reflection start angle θs is the range in which light is totally reflected by the plasmon resonance film 133. Similarly, in the graphs A to H in FIG. 6, there are points A1, B1, C1, D1, E1, F1, G1, and H1 that are convex upward. The external incidence angle θout indicated by this point is the total reflection start angle θs corresponding to the critical angle of light incident on the plasmon resonance film 533. The external incident angle range larger than the total reflection start angle θs is the range in which light is totally reflected by the plasmon resonance film 533.

Further, in the graphs A, B, C, D, E, and F of FIG. 5, there are points A2, B2, C2, D2, E2, and F2 where the current value is approximately the minimum value (convex downward). The external incidence angle θout indicated by these points is the angle corresponding to the plasmon resonance angle θr. Similarly, in graphs B, C, D, E, F, G, and H in Fig. 6, there are points B2, C2, D2, E2, F2, G2, and H2 where the current value is a minimum value (convex downward). . The external incident angle θout indicated by this point is the angle corresponding to the plasmon resonance angle θr. When the external incidence angle θout is an angle corresponding to the plasmon resonance angle θr, surface plasmon resonance is most strongly excited in the plasmon resonance films 133 and 533.

As can be seen from FIGS. 5 and 6, the smaller the refractive index of the transparent substrate 120 or the prism 510, the larger the total reflection start angle θs becomes. Similarly, the smaller the refractive index of the transparent substrate 120 or the prism 510, the larger the external incidence angle θout corresponding to the plasmon resonance angle θr becomes.

Further, as shown in FIG. 6, when using the conventional SPR sensor 500, when the refractive index of the prism 510 is in the range of 1.450 to 1.800, the external incidence angle θout corresponding to the plasmon resonance angle θr is 55 Distributed within the range of 85° to 85°. On the other hand, as shown in FIG. 5, when using the SPR sensor 100A of this embodiment, when the refractive index of the transparent substrate 120 is in the range of 1.450 to 1.800, the external incidence corresponding to the plasmon resonance angle θr is The angle θout is distributed within a wide range of 20° to 75°. This means that when light is incident from the incident side surface 123a of the transparent substrate 120 as in this embodiment, the internal incident angle θin at the plasmon resonance film 133 is set to the plasmon resonance angle θr from an angle where the external incident angle θout is small. On the other hand, in the SPR sensor 500 shown in FIG. 4, unless the external incident angle θout is larger than a predetermined value (for example, 50°), the internal incident angle θin at the plasmon resonance film 533 is changed to the plasmon resonance angle. This means that it cannot be set to θr.

FIG. 7 is an enlarged view of the vicinity of point E2 of graph E in FIG. FIG. 8 is an enlarged view of the vicinity of point F2 of graph F in FIG. A pair of graphs are depicted in these figures. A graph Ea in FIG. 7 shows an incident angle-current value curve when water (refractive index 1.333) is provided as a standard sample on the surface of the plasmon resonance film 133, and a graph Eb in FIG. The incident angle-current value curve is shown when a substance with a refractive index of 1.34 (for example, an aqueous solution with an adjusted concentration of sucrose) is provided on the surface of the film 133. The graph Fa in FIG. 8 shows the incident angle-current value curve when water (refractive index 1.333) is provided on the surface of the plasmon resonance film 533, and the graph F2 in FIG. The incident angle-current value curve is shown when a substance with a refractive index of 1.34 (for example, an aqueous solution with an adjusted sucrose concentration) is provided.

As can be seen from FIG. 7, the external incidence angle (hereinafter sometimes referred to as external resonance angle) θra corresponding to the plasmon resonance angle in the graph Ea is smaller than the external resonance angle θrb in the graph Eb. Similarly, as can be seen from FIG. 8, the external resonance angle θra of the graph Fa is smaller than the external resonance angle θrb of the graph Fb.

Furthermore, as can be seen by comparing FIGS. 7 and 8, the difference Δθ1 between the external resonance angle θrb of the graph Eb in FIG. 7 and the external resonance angle θra of the graph Ea is equal to the external resonance angle θrb of the graph Fb in FIG. is larger than the difference Δθ2 between the external resonance angle θra of the graph Fa and the external resonance angle θra of the graph Fa.

Furthermore, the difference ΔL1 between the current value La of graph E1 and the current value Lb of graph E2 when the external incidence angle θout is fixed at 36° in FIG. 7 is the same as when the external incidence angle θout is fixed at 68° in FIG. is larger than the difference ΔL2 between the current value La of the graph F1 and the current value Lb of the graph F2.

The reason why Δθ1 is larger than Δθ2 and ΔL1 is larger than ΔL2 is inferred as follows. That is, as can be seen by comparing FIGS. 5 and 6, when the SPR sensor 100A according to this embodiment is used, the angular range of the external incident angle in which the incident light is totally reflected by the plasmon resonance film 133 is wide. , the total reflection area in each graph in FIG. 5 is drawn as if the total reflection area in each graph in FIG. 6 was stretched horizontally. Therefore, in each of the graphs A to H in FIG. 5, the interval between the external resonance angles of the pair of graphs also increases, so Δθ1 becomes larger than Δθ2. Similarly, in each pair of graphs A to H in FIG. 5, the difference in current values at a predetermined external incidence angle θout also increases, so ΔL1 becomes larger than ΔL2.

In this way, using the SPR sensors 100A and 100B according to this embodiment, the incident angle to the incident side surface 123a of the transparent substrate 120 is preset (fixed) to an angle at which surface plasmon resonance is excited, and the standard sample and The difference between the current value (or voltage value) obtained for the standard sample and the current value (or voltage value) obtained for the measurement sample S by performing the injection step and the measurement step on the measurement sample S. can be expanded more than before. Therefore, the amount of change in the refractive index of the sample S can be detected with higher accuracy.

Furthermore, according to the present embodiment, by allowing light to enter from the incident side surface 123a of the transparent substrate 120, surface plasmon resonance can be caused in the plasmon resonance film 133 without using a prism, and the above-mentioned By performing the incident step and the measurement step, the amount of change in the refractive index of the sample S can be measured. Therefore, the prism can be omitted, and there is no need to interpose a refractive index adjustment liquid between the prism and the transparent substrate. Therefore, the manufacturing process of the SPR sensor can be simplified, and the cost of the SPR sensor can be reduced.

(Second embodiment)
Next, a second embodiment will be described. FIG. 9 shows a schematic configuration of an SPR sensor 200A according to the second embodiment. As shown in FIG. 9, an SPR sensor 200A according to the second embodiment includes a sensor chip 240 having a transparent substrate 220, a plasmon resonance film 225, and a power generation section 230, and an electrical measurement device 250.

The transparent substrate 220 has the same configuration as the transparent substrate 120 described in the first embodiment, and is formed in a rectangular parallelepiped shape having a first main surface 221, a second main surface 222, and four side surfaces 223. One of the four side surfaces 223 is the entrance side surface 223a. The entrance side surface 223a is mirror polished. That is, a mirror-polished entrance side surface 223a is formed on the side surface 223 of the transparent substrate 220.

Plasmon resonance film 225 is formed on first main surface 221 of transparent substrate 220 . Further, the power generation section 230 is provided on the second main surface 222 of the transparent substrate 220. Therefore, the sensor chip 240 is configured such that the transparent substrate 220 is sandwiched between the plasmon resonance film 225 and the power generation section 230.

The plasmon resonance membrane 225 is configured to have the same function as the plasmon resonance membrane 133 described in the first embodiment. As the material of the plasmon resonance membrane 225, the materials shown as examples of the material of the plasmon resonance membrane 133 described in the first embodiment can be used.

The power generation unit 230 includes an electrode film 231, a silicon semiconductor film 232, and a reflective conductive film 233. 222 in a stacked manner.

The configurations of the electrode film 231 and the silicon semiconductor film 232 are the same as those of the electrode film 131 and the silicon semiconductor film 132 described in the first embodiment. Further, the reflective conductive film 233 is configured to have high conductivity to the extent that it can be used as an electrode, and to have a function of reflecting light. The reflective conductive film 233 may be made of the same material as the plasmon resonance film 225. For example, when the plasmon resonance film 225 is an Au film, the reflective conductive film 233 can also be an Au film. Further, the reflective conductive film 233 may be made of a different material from that of the plasmon resonance film 225. For example, a configuration can be adopted in which the plasmon resonance film 225 is an Au film and the reflective conductive film 233 is an Ag film.

The electrical measurement device 250 is electrically connected to the electrode film 231 and the reflective conductive film 233 of the power generation section 230, and has a function of measuring the current flowing between the connection terminals or the voltage between the connection terminals. Similar to the electrical measuring device 150 according to the first embodiment, this electrical measuring device 250 is electrically connected to the electrode film 231 and the reflective conductive film 233 by connecting conductive wires.

FIG. 10 shows a schematic configuration of an SPR sensor 200B according to another example of the second embodiment. In addition to the configuration of the SPR sensor 200A shown in FIG. 9, the SPR sensor 200B shown in FIG. 10 further includes a first adhesive layer 235 and a second adhesive layer 237. The first adhesive layer 235 is provided between the transparent substrate 220 and the plasmon resonance film 225. The second adhesive layer 237 is provided between the silicon semiconductor film 232 and the reflective conductive film 233 of the power generation section 230. The first adhesive layer 235 is provided to prevent the plasmon resonance membrane 225 from peeling off. The second adhesive layer 237 is provided to prevent the reflective conductive film 233 from peeling off. As the material of the second adhesive layer 237, the material shown in the example of the material of the adhesive layer 135 described in the first embodiment can be adopted. Examples of the material of the first adhesive layer 235 include titanium (Ti), chromium (Cr), nickel (Ni), and titanium nitride (TiN).

Also in this embodiment, the incident side surface 223a of the transparent substrate 220 is substantially perpendicular to the film surface of the plasmon resonance film 225 (the plane on which the plasmon resonance film 225 spreads in a film shape, the bottom surface in FIGS. 9 and 10). It is a good aspect. In other words, the angle between the film surface of the plasmon resonance film 225 and the incident side surface 223a is approximately 90°.

A sample S for measurement is placed on the surface of the plasmon resonance membrane 225. Note that if the reflective conductive film 233 is made of a material that can also be used as a plasmon resonance film, the sample S can be placed on the surfaces of both the plasmon resonance film 225 and the reflective conductive film 233. Then, with the sample S disposed on the surface of the plasmon resonance membrane 225, electrical measurement is performed by the electrical measuring device 250 using the SPR sensor 200A or 200B. The electrical measurement method in this case includes an input step and a measurement step. In the incident step, light is incident from the incident side surface 223a of the transparent substrate 220, and the incident light reaches the plasmon resonance film 225 before passing through the silicon semiconductor film 232 of the power generation section 230, and the plasmon resonance film 225 The light is made incident on the incident side surface 223a at a predetermined external incident angle θout so that the light that reaches the plasmon resonance film 225 is totally reflected. In the measurement step, the electrical measuring device 250 measures the current or voltage generated by power generation in the silicon semiconductor film 232 when light is incident on the incident side surface 223a at a predetermined external incidence angle θout.

By performing the incident step, the light that has entered the SPR sensors 200A and 200B from the incident side surface 223a of the transparent substrate 220 first passes through the silicon semiconductor film 232 of the power generation section 230 after exiting the transparent substrate 220. ), the light that reaches the plasmon resonance film 225 and reaches the plasmon resonance film 225 is totally reflected by the plasmon resonance film 225. The light totally reflected by the plasmon resonance film 225 passes through the transparent substrate 220 again, and then reaches the reflective conductive film 233 via the electrode film 231 and the silicon semiconductor film 232 of the power generation section 230. The light reflected by the reflective conductive film 233 enters the transparent substrate 220 via the silicon semiconductor film 232 and the electrode film 231 again.

In this incident step, surface plasmon resonance occurs when the evanescent wave generated by total reflection of light on the plasmon resonance film 225 interacts with the plasmon resonance film 225. When surface plasmon resonance occurs, the intensity of reflected light decreases significantly. On the other hand, if surface plasmon resonance does not occur, the intensity of reflected light does not decrease much.

Furthermore, when the light incident on the SPR sensors 200A and 200B passes through the silicon semiconductor film 232 of the power generation section 230, conduction electrons are generated due to the internal photoelectric effect in the PIN junction structure, PN junction structure, or IN junction structure of the silicon semiconductor film 232. and holes are generated, and the movement of these generates photovoltaic force. In other words, it generates electricity. The generated power generated in this way is measured as a current value or a voltage value by the electrical measuring device 250. The sample S can be analyzed (for example, the amount of change in the refractive index can be detected) based on the measured current value or voltage value.

In the SPR sensors 100A and 100B according to the first embodiment, the light incident from the incident side surface 123a of the transparent substrate 120 passes through the silicon semiconductor film 132 before reaching the plasmon resonance film 133. Therefore, regardless of whether surface plasmon resonance occurs in the plasmon resonance film 133, power generation occurs by the light that first passes through the silicon semiconductor film 132. Therefore, whether or not surface plasmon resonance occurs in the plasmon resonance film 133, the amount of power generated by the light that first passes through the silicon semiconductor film 132 is the same, and there is no difference in the amount of power generated. What is generated is the amount of power generated when the light after being reflected by the plasmon resonance film 133 passes through the silicon semiconductor film 132. In other words, the power generated by the light that first passes through the silicon semiconductor film 132 can be said to be power generation that does not contribute to the analysis of the sample S (detection of the amount of change in the refractive index).

Furthermore, in the SPR sensors 100A and 100B according to the first embodiment, the intensity of the light that first passes through the silicon semiconductor film 132 is the highest, so the amount of power generation is also the highest. Therefore, the largest amount of power generation is not reflected in the detection of the amount of change in the refractive index of the sample S based on the measurement result of the electrical measuring device 150, and there is a possibility that the sensitivity of the SPR sensor cannot be sufficiently increased.

On the other hand, in the SPR sensors 200A and 200B according to the present embodiment, the light incident on the transparent substrate 220 from the incident side surface 223a of the transparent substrate 220, before passing through the silicon semiconductor film 232 of the power generation section 230, It reaches the plasmon resonance membrane 225. Therefore, all the light that passes through the silicon semiconductor film 232 after that is influenced by the presence or absence of surface plasmon resonance excitation in the plasmon resonance film 225. Therefore, if surface plasmon resonance occurs in the plasmon resonance film 225, the intensity of the light will be greatly reduced, and the light whose intensity has been greatly reduced will pass through the silicon semiconductor film 232 from the beginning. The amount of power generated by the silicon semiconductor film 232 is significantly reduced. On the other hand, if surface plasmon resonance does not occur in the plasmon resonance film 225, the intensity of light hardly decreases. Therefore, in this case, the amount of power generation in the silicon semiconductor film 232 increases because the light whose intensity has not decreased passes through the silicon semiconductor film 232. As described above, by using the SPR sensors 200A and 200B according to the present embodiment, the difference in the amount of power generation (for example, the output current difference) can be increased. Thereby, the sensitivity of the SPR sensor can be significantly improved.

FIG. 11A is a graph showing simulation results of the incident angle-current value curve for the SPR sensor 100A according to the first embodiment. Here, the horizontal axis of the graph in FIG. 11A is the internal incident angle θin, which is the incident angle of light to the plasmon resonance film 133, and the vertical axis is the relative amount (%) of the current value. Note that FIG. 11A shows respective incident angle-current value curves when the refractive index of the sample S disposed in the SPR sensor 100A is changed stepwise from 1.3330 to 1.3360.

Further, FIG. 11B is a graph obtained by normalizing the graph of FIG. 11A based on the case where the internal incident angle θin is the critical angle θc. Specifically, FIG. 11B is a graph obtained by normalizing the graph shown in FIG. 11A by setting the value of the vertical axis at the critical angle θc to 1.

According to FIG. 11B, the difference (CA1−CA2 ) is found to be 55.4%. That is, the reduction rate of the current value when the internal incidence angle θin changes from the critical angle θc to the plasmon resonance angle θr is 55.4%.

FIG. 12A is a graph showing simulation results of an incident angle-current value curve obtained when the measurement process is performed while changing the incident angle using the SPR sensor 200A according to the second embodiment. Similar to the graph of FIG. 11A, the horizontal axis of the graph in FIG. 12A is the internal incident angle θin, which is the angle of incidence of light on the plasmon resonance film 225, and the vertical axis is the relative amount (%) of the current value. Note that FIG. 12A also shows incident angle-current value curves when the refractive index of the sample S disposed in the SPR sensor 200A is changed stepwise from 1.3330 to 1.3360.

FIG. 12B is a graph obtained by normalizing the graph of FIG. 12A based on the critical angle θc. According to FIG. 12B, the difference (CB1−CB2 ) is found to be 94.6%. In other words, the current reduction rate when the internal incident angle θin changes from the critical angle θc to the plasmon resonance angle θr is 94.6%.

As described above, by using the SPR sensor 200A according to the second embodiment, the reduction rate of the current value at the plasmon resonance angle θr can be reduced by about 1. It can be made up to 7 times larger. Therefore, the slope of the incident angle-current value curve near the plasmon resonance angle θr can be made steeper. Then, the steeper the slope of the incident angle-current value curve, the greater the difference ΔL in current magnitude due to the difference in the refractive index of the sample S. Therefore, the sensitivity of the SPR sensor can be greatly improved.

[Example 1] Production of the SPR sensor according to the first embodiment (1) Formation of electrode film on glass substrate A rectangular parallelepiped glass substrate (S -NBH5, refractive index: 1.648) was prepared for incident light of 670 nm. Next, one of the side surfaces of the glass substrate was mirror-polished to form an incident side surface on the side surface. Next, an ITO film (highly durable transparent conductive film, electrical resistance 5Ω) was formed as an electrode film on one main surface (first main surface) of the glass substrate.

(2) Formation of silicon semiconductor film Next, an n-type silicon semiconductor film was formed on the ITO film formed on the glass substrate. In this case, sputtering was performed using a sputtering device QAM-4 manufactured by ULVAC Co., Ltd., using P (phosphorus)-doped n-type Si (electrical resistivity 0.02 Ω cm or less) manufactured by Furuuchi Chemical Co., Ltd. as a target. An n-type silicon semiconductor film with a thickness of 20 nm was formed on the ITO film by a method.

Next, a film with a thickness of 170 nm was deposited on the n-type silicon semiconductor film by sputtering using the same equipment as above and using non-doped Si manufactured by Furuuchi Chemical Co., Ltd. (electrical resistivity 1000 Ω cm or more) as a target. An i-type silicon semiconductor film was formed. An n-type silicon semiconductor film and an i-type silicon semiconductor film formed on the ITO film constitute a silicon semiconductor film. This silicon semiconductor film is amorphous.

(3) Formation of plasmon resonance film Next, using the same apparatus as above, Au manufactured by Tanaka Kikinzoku Kogyo Co., Ltd. was deposited on the silicon semiconductor film formed as described above (on the i-type silicon semiconductor film). (purity 99.99%), a 50 nm thick Au film (plasmon resonance film) was formed by sputtering.

(4) Connection of electrical measuring device Next, an electrical measuring device was connected between the ITO film and the plasmon resonance film. A semiconductor device analyzer B1500A manufactured by Keysight Technologies Co., Ltd. was used as an electrical measuring device.

Through the above steps, an SPR sensor 100A according to the first embodiment was manufactured.

[Example 2] Production of an SPR sensor according to the second embodiment (1) Formation of an electrode film on a glass substrate On the other main surface (second main surface) of a glass substrate having the same configuration as in Example 1. As an electrode film, an ITO film (highly durable transparent conductive film, electrical resistance 5Ω) having the same structure as in Example 1 was formed.
(2) Formation of silicon semiconductor film Next, an n-type silicon semiconductor film having the same structure as in Example 1 was formed by the same method on the ITO film formed on the glass substrate. Next, on the formed n-type silicon semiconductor film, an i-type silicon semiconductor film having the same structure as in Example 1 was formed by the same method.

(3) Formation of reflective conductive film Next, an Au film was formed as a reflective conductive film on the silicon semiconductor film formed as described above (on the i-type silicon semiconductor film). In this case, an Au film with a thickness of 50 nm was formed by sputtering using a sputtering device QAM-4 manufactured by ULVAC Co., Ltd. and using Au (purity 99.99%) manufactured by Tanaka Kikinzoku Kogyo Co., Ltd. as a target. A film was formed.

(4) Formation of plasmon resonance film Next, a plasmon resonance film (50 nm thick Au film) having the same structure as in Example 1 was deposited on one main surface (first main surface) of the glass substrate using the same method. The film was formed using

(5) Connection of electrical measuring device Subsequently, an electrical measuring device having the same configuration as in Example 1 was connected between the ITO film and the reflective conductive film (Au film).

Through the above steps, an SPR sensor 200A according to the second embodiment was manufactured.

[Measurement of generated current]
A laser oscillation device (CPS670F, manufactured by Thorlabs, Inc.) and a polarizing plate (CMM1-PBS251/M, manufactured by Thorlabs, Inc.) were prepared. Further, a sample was placed on the surface of each plasmon resonance film (Au film) of the SPR sensor 100A according to Example 1 and the SPR sensor 200A according to Example 2, which were manufactured as described above. Note that water (standard sample) and an aqueous sucrose solution (concentration 2.5%) were used as samples. Then, using the prepared laser oscillation device and polarizing plate, a laser beam with a wavelength of 670 nm was irradiated onto the SPR sensors 100A and 200A on which the sample was disposed, respectively.

FIG. 13A is a schematic diagram showing how the SPR sensor 100A according to the first embodiment is irradiated with laser light from the laser oscillation device. Further, FIG. 13B is a diagram showing how the SPR sensor 200A according to the second embodiment is irradiated with laser light from the laser oscillation device. As shown in FIGS. 13A and 13B, the laser oscillation device 300 emits laser light with an output of 4.0 mW and a wavelength of 670 nm. The emitted laser light is P-polarized by the polarizing plate 400, and then enters the incident side surface of the glass substrate G of the SPR sensors 100A and 200A. At this time, in the SPR sensor 100A, the laser beam incident from the incident side of the glass substrate G reaches the plasmon resonance film P (Au film) via the electrode film E (ITO film) and the silicon semiconductor film H. The SPR sensor 100A was arranged with the incident side surface of the glass substrate G inclined relative to the optical axis of the laser beam. In addition, in the SPR sensor 200A, the laser beam incident on the incident side surface of the glass G substrate is transmitted to the plasmon resonance film P (Au) formed on one main surface (first main surface) of the glass substrate G. The incident side of the glass substrate G is aligned with respect to the optical axis of the laser beam so that the laser beam reaches the plasmon resonant film P before passing through the silicon semiconductor film H. The SPR sensor 200A was placed in a relatively inclined state.

For each of the SPR sensors 100A and 200A, the electric current was measured by the electrical measuring device M while changing the external incident angle θout of the laser beam. Then, based on the measurement results, incident angle-current value curves were created for each of the SPR sensors 100A and 200A.

FIG. 14 shows an incident angle-current value curve created based on the actually measured current value when using the SPR sensor 100A according to the first embodiment. Further, FIG. 15 shows an incident angle-current value curve created based on the actually measured current value when using the SPR sensor 200A according to the second embodiment. In FIGS. 14 and 15, graph A is an incident angle current value curve when water is used as a sample, and graph B is an incident angle current value curve when a sucrose aqueous solution is used as a sample. Note that the horizontal axis in FIGS. 14 and 15 is the external incident angle θout, and the vertical axis is the actually measured current value.

In FIG. 14, when the external incident angle θout is about 56°, the difference between the current value of graph A and the current value of graph B (current value difference ΔL1) is the largest. Further, in FIG. 15, when the external incidence angle is about 54°, the difference between the current value of graph A and the current value of graph B (current value difference ΔL2) is the largest. As is clear from comparing FIGS. 14 and 15, the current value difference ΔL2 is larger than the current value difference ΔL1. Therefore, according to the SPR sensor 200A according to Example 2, the difference in current due to the difference in the refractive index of the sample becomes larger, and therefore it is understood that the sensitivity can be significantly improved.

Although the embodiments of the present invention have been described above, the present invention should not be limited to the above embodiments. For example, in the above embodiment, a rectangular parallelepiped-shaped transparent substrate is shown as the transparent substrate, but the transparent substrate need not be rectangular parallelepiped-shaped as long as it has a side surface through which light enters. For example, a hexagonal columnar transparent substrate can be used, and one of its sides can be used as the incident side. Thus, the present invention can be modified without departing from its spirit.

100A, 100B, 200A, 200B... Electric measurement type SPR sensor, 120, 220... Transparent substrate, 121, 221... First principal surface, 122, 222... Second principal surface, 123, 223... Side surface, 123a, 223a... Incident Side surface, 130, 130'... Sensor chip, 131, 231... Electrode film, 132, 232... Silicon semiconductor film, 133, 250... Plasmon resonance film, 135... Adhesive layer, 140, 240... Electrical measurement device, 230... Power generation Part, 233... Reflective conductive film, 235... Second adhesive layer, 250... Plasmon resonance film, 255... First adhesive layer, 300... Laser oscillation device, 400... Polarizing plate, θin... Internal incident angle, θout... External incident angle , θr...Plasmon resonance angle

Claims (8)

a transparent substrate having a first principal surface and a second principal surface perpendicular to the thickness direction and a side surface connecting respective peripheral edges of the first principal surface and the second principal surface; and the first principal surface of the transparent substrate. a sensor chip formed on the first main surface, and a sensor section having an electrode film, a silicon semiconductor film, and a plasmon resonance film, which are stacked in this order on the first main surface; ,
an electrical measuring device that is electrically connected to the electrode film and the plasmon resonance film and measures current or voltage generated by power generation in the silicon semiconductor film;
Equipped with
An electrometric surface plasmon resonance sensor, wherein an incident side surface through which light is incident is formed on the side surface of the transparent substrate. The electrometric surface plasmon sensor according to claim 1,
An electrical measurement type surface plasmon resonance sensor, wherein the angle between the membrane surface of the plasmon resonance membrane and the incident side surface is approximately 90 degrees. a transparent substrate having a first principal surface and a second principal surface perpendicular to the thickness direction and a side surface connecting respective peripheral edges of the first principal surface and the second principal surface; and the first principal surface of the transparent substrate. a plasmon resonance film formed on the transparent substrate, and an electrode film, a silicon semiconductor film, and a reflective conductive film formed on the second main surface of the transparent substrate, and these are stacked in this order. a sensor chip having a power generation section configured of;
an electrical measuring device that is electrically connected to the electrode film and the reflective conductive film and measures the current or voltage generated by power generation in the silicon semiconductor film;
Equipped with
An electrometric surface plasmon resonance sensor, wherein an incident side surface through which light is incident is formed on the side surface of the transparent substrate. The electrometric surface plasmon resonance sensor according to claim 3,
An electrical measurement type surface plasmon resonance sensor, wherein the angle between the membrane surface of the plasmon resonance membrane and the incident side surface is approximately 90 degrees. An electrical measurement method using the electrical measurement type surface plasmon resonance sensor according to claim 1 or 2,
The light is incident on the plasmon resonance film at a predetermined angle of incidence so that the light enters the plasmon resonance film from the incident side surface and the light that reaches the plasmon resonance film is totally reflected by the plasmon resonance film. a step of making it incident on the incident side;
measuring, with the electrical measuring device, a current or voltage generated by power generation in the silicon semiconductor film when light is incident on the incident side surface at the predetermined incident angle;
electrical measurement methods, including; The electrical measurement method according to claim 5,
The predetermined incident angle is an electrical angle that is predetermined as an angle at which surface plasmon resonance is excited by the interaction between the evanescent wave generated by total reflection of light incident on the plasmon resonance film and the plasmon resonance film. Measuring method. An electrical measurement method using the electrical measurement type surface plasmon resonance sensor according to claim 3 or 4,
Light enters from the incident side surface, and the incident light reaches the plasmon resonance film before passing through the silicon semiconductor film, and the light that reaches the plasmon resonance film is totally reflected by the plasmon resonance film. making light incident on the incident side at a predetermined angle of incidence,
measuring, with the electrical measuring device, a current or voltage generated by power generation in the silicon semiconductor film when light is incident on the incident side surface at the predetermined incident angle;
electrical measurement methods, including; The electrical measurement method according to claim 7,
The predetermined incident angle is an electrical angle that is predetermined as an angle at which surface plasmon resonance is excited by the interaction between the evanescent wave generated by total reflection of light incident on the plasmon resonance film and the plasmon resonance film. Measuring method.

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