CN112666243A - Optical addressing square wave/alternating current volt-ampere electrochemical sensing system and method - Google Patents
Optical addressing square wave/alternating current volt-ampere electrochemical sensing system and method Download PDFInfo
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- CN112666243A CN112666243A CN202011376443.2A CN202011376443A CN112666243A CN 112666243 A CN112666243 A CN 112666243A CN 202011376443 A CN202011376443 A CN 202011376443A CN 112666243 A CN112666243 A CN 112666243A
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Abstract
The invention discloses a light addressing square wave/alternating current volt-ampere electrochemical sensing system and a method, a semiconductor chip is fixed at the lower end of a detection cell device, a through hole containing cavity is arranged on the detection cell device, a counter electrode and a reference electrode of the electrochemical detection device are arranged in detection liquid at intervals, a working electrode of the electrochemical detection device is electrically connected with the lower end of the semiconductor chip, constant laser is adopted to irradiate a specific position of the semiconductor chip with a field effect structure to excite and generate in-situ photon-generated carriers, simultaneously, the external voltage of the semiconductor chip is modulated by utilizing the SWV or ACV function of an electrochemical workstation to influence the directional migration and diffusion process of the photon-generated carriers, so that in-situ photocurrent is obtained by external circuit detection, the detection of the pH value of a solution and the in-situ detection and imaging of the surface impedance of the chip can be realized, compared with the traditional electrochemical analysis method, provides a new solution for high-throughput multi-site electrochemical detection.
Description
Technical Field
The invention belongs to the photoelectric chemical sensing and imaging technology, and particularly relates to a light-addressable square wave/alternating current volt-ampere electrochemical sensing system and method.
Background
Square Wave Voltammetry (SWV) is a method in which a square wave voltage with a large amplitude is superposed on a step voltage for rapid scanning, and the difference between the currents at the last stage of a positive half cycle and the last stage of a negative half cycle of the square wave is recorded, so that the charging current is well eliminated, and a current-potential voltammogram can be recorded in a short time. Alternating Current Voltammetry (ACV) is to apply a dc potential which is scanned slowly with time to a working electrode, superimpose a sine wave ac component, measure the amplitude and corresponding phase angle of the ac component of the current, and obtain a corresponding ac voltammogram. The two methods have the characteristics of multiple functions, high sensitivity and high efficiency, and are widely applied to quantitative analysis and kinetic research of substances. However, conventional SWV and ACV electrical analysis methods do not have spatial resolution, reflect the whole information of the detected sample by using the average result of electrode measurement, are difficult to meet the requirements of high-flux and multi-site detection and sensing, and cannot perform two-dimensional imaging on the detected sample.
Disclosure of Invention
The invention provides an addressable square wave/alternating current volt-ampere electrochemical sensing and imaging method, which realizes sensing and detection of surface potential and system impedance with spatial resolution capability and overcomes the defect that the conventional electrochemical detection technology lacks spatial resolution capability.
In order to achieve the purpose, the invention adopts the following technical scheme:
a light addressing square wave/alternating current volt-ampere electrochemical sensing system comprises a laser device, a semiconductor chip, a detection cell device, an electrochemical detection device, a displacement device and an optical imaging device; the semiconductor chip is fixed in the lower extreme of detection cell device, be equipped with the through-hole on the detection cell device and hold the chamber, the through-hole holds the intracavity and is used for placing detection liquid, it can with the semiconductor chip up end contact to detect liquid, electrochemistry detection device's counter electrode and reference electrode interval are placed in detecting liquid, electrochemistry detection device's working electrode is connected with semiconductor chip lower extreme electricity, laser device and optical imaging device set up in detection cell device upper end, optical imaging device's light source and laser device's laser can shine on semiconductor chip upper surface through the through-hole appearance chamber, semiconductor chip and detection cell device are fixed in on the displacement device.
Furthermore, the electrochemical detection device comprises an electrochemical workstation, a counter electrode, a reference electrode and a working electrode, wherein the counter electrode, the reference electrode and the working electrode are all connected with the electrochemical workstation, the electrodes adopt platinum wires, the reference electrode adopts an Ag/AgCl reference electrode, and the working electrode is connected with the semiconductor chip.
Furthermore, the laser device comprises a laser controller, a laser, a collimating lens, a beam splitter prism and an amplifying objective lens, wherein the amplifying objective lens is arranged at the upper end of the detection cell device, the collimating lens is arranged at the laser emitting end of the laser, the beam splitter prism is arranged between the collimating lens and the amplifying objective lens, and the laser is connected with the laser controller.
Furthermore, the optical imaging device comprises an LED illumination light source, a field lens and a CCD camera, the CCD camera is connected with a computer, the computer is used for acquiring and storing images, the field lens is arranged on one side of the beam splitter prism, and the field lens, the beam splitter prism and the magnifying objective lens are arranged on the same straight line.
Further, the semiconductor chip is a pH sensitive semiconductor chip or an impedance sensitive semiconductor chip.
Further, the pH sensitive semiconductor chip comprises a sensitive layer, an insulating layer, a semiconductor layer and an ohmic contact layer which are sequentially stacked from top to bottom, the ohmic contact layer is electrically connected with a working electrode of the electrochemical detection device and is in contact with electrolyte in the detection cell device, the impedance sensitive semiconductor chip comprises the insulating layer, the semiconductor layer and the ohmic contact layer which are sequentially stacked from top to bottom, the ohmic contact layer is electrically connected with the working electrode of the electrochemical detection device, and the insulating layer is in contact with the electrolyte in the detection cell device.
Furthermore, the detection cell device comprises a detection cavity and an electric connection sheet, wherein the detection cavity is provided with a through hole cavity, the lower end face of the semiconductor chip is in sealing contact with the lower end face of the detection cavity, the electric connection sheet is arranged at the lower end of the semiconductor chip, and the electric connection sheet is electrically connected with the semiconductor chip.
An optically addressed square wave/alternating current voltammetric electrochemical imaging method comprising the steps of:
s1, fixing the detection cell device fixed with the pH sensitive semiconductor chip on the displacement device, and adding buffer salt electrolytes with different pH values into a through hole cavity of the detection cell device; putting a counter electrode and a reference electrode of the electrochemical detection device into electrolyte, and connecting a working electrode with an ohmic contact layer of the pH sensitive semiconductor chip;
s2, adjusting the displacement device to enable the laser generated by the laser to irradiate the upper end of the pH sensitive semiconductor chip through the through hole cavity of the detection cell device, and enabling the laser focus point to be located at the position of 0.8-1.2cm of the surface of the semiconductor;
and S3, sequentially carrying out SWV and ACV electrochemical tests on the solutions with different pH values by adopting an electrochemical workstation to obtain a dark/light current-potential curve, thereby completing addressable square wave/alternating current volt-ampere electrochemical sensing detection.
An optically addressed square wave/alternating current volt-ampere electrochemical sensing method comprises the following steps:
s1, fixing the detection cell device fixed with the impedance sensitive semiconductor chip on the displacement device, and adding electrolyte into the detection cell device; putting a counter electrode and a reference electrode of the electrochemical detection device into electrolyte, and connecting a working electrode with an ohmic contact layer of the impedance sensitive semiconductor chip through an electric connection sheet;
s2, adjusting the displacement device to enable the laser generated by the laser to irradiate the surface of the impedance sensitive semiconductor chip through the through hole cavity of the detection cell device and enable the laser focus point to be positioned on the surface of the semiconductor chip;
s3, sequentially carrying out SWV and ACV electrochemical tests by adopting an electrochemical workstation to respectively obtain I-V curves of the tested SWV and ACV;
s4, adjusting the displacement device, observing through the optical imaging system, enabling the semiconductor chip to perform two-dimensional scanning on a horizontal plane relative to the laser by taking the photoetching pattern as a center, and taking the SWV photocurrent magnitude under the fixed potential of the corresponding coordinate, thereby obtaining the photocurrent distribution image of the photoetching pattern, namely the photoaddressing square wave volt-ampere electrochemical impedance diagram;
further, the displacement device is adjusted to enable the electric semiconductor chip to move linearly relative to the laser in a horizontal direction, SWV scanning is conducted on the edge of the photoetching pattern on the semiconductor chip, so that a current-position curve under a fixed potential is obtained, differential processing is conducted on the current-position curve, and the size of the half-peak width is obtained, namely the size of the spatial resolution of the optical addressing square wave volt-ampere impedance imaging.
Compared with the prior art, the invention has the following beneficial technical effects:
the invention relates to a light-addressable square wave/alternating current volt-ampere electrochemical sensing system, a semiconductor chip is fixed at the lower end of a detection cell device, a through hole containing cavity is arranged on the detection cell device, so that detection liquid can be contacted with the upper end surface of the semiconductor chip to form a detection space, a counter electrode and a reference electrode of an electrochemical detection device are arranged in the detection liquid at intervals, a working electrode of the electrochemical detection device is electrically connected with the lower end of the semiconductor chip, a laser device is arranged at the upper end of the detection cell device, laser of the laser device can irradiate the upper surface of the semiconductor chip through the through hole containing cavity, the semiconductor chip and the detection cell device are fixed on a displacement device, the specific position of the chip is irradiated by the laser, based on SWV and ACV electric analysis means of an electrochemical workstation, addressable detection of the surface potential and system impedance of, simple structure and easy wide application.
The invention relates to a light-addressable square wave/alternating current volt-ampere electrochemical sensing and imaging method, which adopts constant laser to irradiate a specific position of a semiconductor chip with a field effect structure, excites and generates an in-situ photon-generated carrier, and simultaneously modulates the external voltage of the semiconductor chip by utilizing the SWV or ACV function of an electrochemical workstation to influence the directional migration and diffusion process of the photon-generated carrier, thereby obtaining the in-situ photocurrent in an external circuit detection, and realizing the detection of the pH value of a solution and the in-situ detection and imaging of the surface impedance of the chip.
Drawings
Fig. 1 is a schematic structural diagram in an embodiment of the present invention.
FIG. 2 is a schematic view of a test cell device and a semiconductor chip mounting structure according to an embodiment of the present invention.
FIG. 3 is a SWV current-potential I-V curve diagram of a pH sensitive semiconductor chip with and without light in an embodiment of the present invention.
FIG. 4 is a graph of the current-potential I-V of the ACV of the pH sensitive semiconductor chip with and without light according to an embodiment of the present invention.
FIG. 5 is a SWV curve of potential scanning of a pH sensitive semiconductor chip according to an embodiment of the present invention; fig. 5a is a graph of the photo-addressable SWV in buffer solutions with pH 3,4,5,6,7,8,9.2, respectively, and fig. 5b is a graph of the potential as a function of pH at-100 nA constant current.
Fig. 6 is a graph of potential scan ACV of a pH sensitive semiconductor chip in an embodiment of the present invention, fig. 6a is a graph of photo-addressable ACV in buffer solutions with pH 3,4,5,6,7,8, and 9.2, respectively, and fig. 6b is a graph of the linear relationship of potential versus pH at a constant current of 410 nA.
Fig. 7 is a graph of the scanning I-V curve of an optically addressed SWV of an impedance sensitive semiconductor chip in an embodiment of the present invention in areas with SU8 coverage and without SU 8.
Fig. 8 is a graph of the scanning I-V of an optically addressed ACV of an impedance-sensitive semiconductor chip in an embodiment of the present invention in an area with SU8 coverage and in an area without SU 8.
FIG. 9 is a two-dimensional scan of a focused laser over a SU8 pattern, according to an embodiment of the present invention, and FIG. 9a is an optical image taken by an optical imaging system; FIG. 9b is a two-dimensional distribution plot of photocurrent obtained from a SWV scan at a potential of-0.8V.
FIG. 10 shows the result of a linear scan of a focused laser at the edge of an SU8 pattern according to an embodiment of the present invention, and FIG. 10a is a plot of SWV current versus position (I-x) at the resulting-0.8V potential; FIG. 10b is the result of evaluating spatial resolution based on SWV current-position (I-x) plots.
Wherein, 1, a laser device; 2. a semiconductor chip; 3. a detection cell device; 4. an electrochemical detection device; 5. a displacement device; 6. a counter electrode; 7. a reference electrode; 8. a working electrode; 9. a sensitive layer; 10. an insulating layer; 11. a semiconductor layer; 12. an ohmic contact layer; 13. a detection cavity; 14. an electrically connecting sheet; 15. a seal ring; 16. a bolt group; 17. an electrochemical workstation; 18. an optical imaging device; 19. a laser controller; 20. a laser; 21. a collimating lens; 22. a beam splitter prism; 23. a magnifying objective lens; 24. an LED illumination light source; 25. a field lens; 26. a computer; 27. a CCD camera.
Detailed Description
The invention is described in further detail below with reference to the accompanying drawings:
as shown in fig. 1, an optical addressing square wave/ac volt-ampere electrochemical sensing system comprises a laser device 1, a semiconductor chip 2, a detection cell device 3, an electrochemical detection device 4, a displacement device 5 and an optical imaging device 18; semiconductor chip 2 is fixed in detection pond device 3 lower extreme, it holds the chamber to be equipped with the through-hole on detection pond device 3, the through-hole holds the intracavity and is used for placing detection liquid, it can contact with semiconductor chip 2 up end to detect liquid, electrochemical detection device 4's counter electrode 6 and reference electrode 7 interval are placed in detecting liquid, electrochemical detection device 4's working electrode 8 is connected with semiconductor chip 2 lower extreme electricity, laser device 1 and optical imaging device set up in detection pond device 3 upper end, optical imaging device's light source and laser device 1's laser can shine in semiconductor chip 2 upper surface through the through-hole appearance chamber, laser device 1 and optical imaging device 2 form confocal system, semiconductor chip 2 and detection pond device 3 are fixed in on displacement device 5.
The electrochemical detection device 4 includes an electrochemical workstation 17, a counter electrode 6, a reference electrode 7, and a working electrode 8. The counter electrode, the reference electrode and the working electrode are connected with an electrochemical workstation and used for SWV and ACV electrochemical detection; the counter electrode adopts a platinum wire, the reference electrode adopts an Ag/AgCl reference electrode, and the working electrode is connected with the semiconductor chip.
The laser device 1 comprises a laser controller 19, a laser 20, a collimating lens 21, a beam splitter prism 22 and an amplifying objective lens 23, the amplifying objective lens 23 is arranged at the upper end of the detection cell device 3, the collimating lens 21 is arranged at the laser emitting end of the laser 20, the beam splitter prism 22 is arranged between the collimating lens 21 and the amplifying objective lens 23, the laser is connected with the laser controller and generates laser with the wavelength of 405nm, the laser irradiates the upper surface of the semiconductor chip through the collimating lens 21, the beam splitter prism 22, the amplifying objective lens 23 and the through hole containing cavity, and the diameter of a light spot is about 10 mu m when the light spot is focused; the magnifying objective 23 has a magnification of 10.
The optical imaging device comprises an LED illumination light source 24, a field lens 25 and a CCD camera 27, the CCD camera is connected with a computer 26, the computer 26 is used for obtaining and storing images, the field lens 25 is arranged on one side of the beam splitter prism 22, the field lens 25, the beam splitter prism 22 and the magnifying objective 23 are arranged on the same straight line, LED illumination light irradiates the upper surface of the semiconductor chip through the through hole containing cavity, and reflected light of the LED illumination light passes through the magnifying objective 23, the beam splitter prism, the field lens and the CCD camera to obtain optical images.
The semiconductor chip 2 adopts a pH sensitive semiconductor chip or an impedance sensitive semiconductor chip; the pH sensitive semiconductor chip comprises a sensitive layer 9, an insulating layer 10, a semiconductor layer 11 and an ohmic contact layer 12 which are sequentially stacked from top to bottom, wherein the ohmic contact layer 12 is electrically connected with a working electrode 8 of the electrochemical detection device 4 to form good contact so as to conduct current, and the sensitive layer 9 is in contact with electrolyte in the detection cell device 3. The impedance sensitive semiconductor chip comprises an insulating layer 10, a semiconductor layer 11 and an ohmic contact layer 12 which are sequentially stacked from top to bottom, wherein the ohmic contact layer 12 is electrically connected with a working electrode 8 of the electrochemical detection device 4, the insulating layer 10 is in contact with an electrolyte in the detection cell device 3, and the surface of the insulating layer is provided with an SU8 photoresist pattern.
As shown in fig. 2, the detection cell device 3 includes a detection cavity 13 and an electrical connection sheet 14, the detection cavity 13 is provided with a through hole cavity, the semiconductor chip 2 contacts with the lower end surface of the detection cavity 13, the electrical connection sheet 14 is arranged at the lower end of the semiconductor chip 2, and the electrical connection sheet 14 is electrically connected with the semiconductor chip 2; the semiconductor chip 2 is fixedly connected with the detection cavity 13 through the bolt group 16, and the semiconductor chip 2 is clamped between the electric connecting sheet 14 and the detection cavity 13; specifically, the ohmic contact layer 12 of the semiconductor chip 2 is in contact with the electrical connection pad 14.
And a sealing ring 15 is arranged between the semiconductor chip 2 and the lower end surface of the detection cavity 13, and the sealing ring is a silicon rubber sealing ring. The detection cavity 13 is made of organic glass. The electrical connection sheet 14 is an aluminum sheet.
The pH sensitive semiconductor chip is used for solution pH test,the application adopts the specific structure of the pH sensitive semiconductor chip as follows: (50nm Si)3N4) Insulating layer (100nm SiO)2) -semiconductor layer (p-Si,100,1-10 Ω cm) -ohmic contact (30nm Cr,150nm Au), in which Si3N4The ohmic contact is prepared by magnetron sputtering method, SiO2Is grown by a thermal oxidation method.
The impedance sensitive semiconductor chip is used for impedance imaging, and the specific structure of the impedance sensitive semiconductor chip is adopted in the application as follows: insulating layer self-assembled organic monolayers (SAMs) -semiconductor layer (p-Si,100,1-10 Ω cm) -ohmic contact (30nm Cr,150nm Au), wherein SAMs is an undecylenic acid film grown by a thermally induced silylation method and has a thickness of 1nm, and compared with a conventional silicon oxide insulating layer, the impedance sensitivity of the system can be significantly increased. During electrochemical detection, the sensitive layer of the semiconductor chip faces upwards and is used as a working electrode to be in contact with electrolyte, and SU 82005 photoresist patterns with the thickness of about 5 mu m are prepared on the surface of the insulating layer.
The displacement device 5 adopts a three-dimensional electric displacement system, and the detection cell device 3 is fixed on an XY plane of the displacement system.
An optically addressed square wave/alternating current volt-ampere electrochemical sensing method comprises the following steps:
s1, cleaning and assembling the semiconductor chip:
and 3, fixing the detection cell device 3 assembled with the semiconductor chip on a displacement device 5, and adjusting the displacement device to enable the laser generated by the laser device 1 to irradiate the semiconductor chip.
S2, photocurrent response test:
adjusting the Z-direction height of the displacement device 5 to enable the semiconductor chip on the detection cell device 3 to be located at the position of 0.8-1.2cm of the focal point of the laser generated by the laser device 1, namely in a non-focusing state, and turning off or on the laser.
Connecting a pH sensitive semiconductor chip with a working electrode, taking a silver/silver chloride reference electrode as a reference electrode, and taking a platinum wire as a counter electrode to form a three-electrode system; the voltage sweep range of the SWV is: 0.4 to-1.2V, the amplitude is 0.05V, and the scanning frequency is 1 KHz; the voltage sweep range of the ACV is: 0.1 to-1.5V, amplitude of 0.02V and scanning frequency of 200 Hz.
S3, pH sensitivity test:
and adjusting the Z-direction height of the displacement device 5 to enable the semiconductor chip on the detection cell device 3 to be positioned at the position of a laser focus generated by the laser device 1, namely, in a non-focusing state, and inspecting the sensitivity of the pH sensitive semiconductor chip to the pH of the solution. 2ml of different (pH value: 3-9.2) 0.1M NaCl buffer solutions were added to the detection chamber, and the I-V curves corresponding to SWV and ACV were tested accordingly. The voltage sweep range of the SWV is: 0.4 to-1.2V, the amplitude is 0.05V, and the scanning frequency is 1 KHz; the voltage sweep range of the ACV is: 0.1 to-1.5V, amplitude of 0.02V and scanning frequency of 200 Hz.
S4, impedance in-situ detection and imaging:
And 2, based on the SWV I-V curve result obtained in the step 1, carrying out two-dimensional scanning on the SU8 pattern at a potential of-0.8V to obtain an SWV photo-current diagram, and comparing the SWV photo-current diagram with an optical diagram shot by an optical imaging system. The pattern is subjected to SWV test (-0.78 to-0.8V, amplitude 0.05V and scanning frequency 100Hz) by two-dimensional scanning (step length: 4 μm, dead time: 2.3s, scanning range: 200 μm × 200 μm) of the displacement device in the x and y directions, namely, the SWV current of the point under-0.8V is collected every time the displacement device moves to the point, so that a photocurrent two-dimensional image is obtained.
An SU 82005 pattern was prepared on the surface of the semiconductor chip using standard photolithography, with a photoresist thickness of 5 μm and a pattern of 100 μm square.
Step 3) detecting the resolution of the optical addressing SWV impedance imaging under-0.8V potential: through the linear movement of the displacement device in the x direction (step length: 2 μm, dead time: 2.3s), the pattern edge is subjected to SWV scanning (-0.78 to-0.8V, amplitude 0.05V and scanning frequency 100Hz), namely, when the displacement device moves to one point, the SWV current of the point under-0.8V is collected, so that a photocurrent-position (I-x) curve is obtained, the curve is subjected to differential processing, and the half-peak width is obtained, namely the spatial resolution of the optical addressing SWV impedance imaging.
For the above described applications for surface potential sensing and impedance imaging, the detection results are as follows:
when the potential scanning range is 0.4 to-1.2V, the potential amplitude is 0.05V, and the scanning frequency is 1KHz, the SWV I-V curve of the pH sensitive semiconductor chip is shown in FIG. 3, and it can be known from FIG. 3 that the photocurrent changes with the potential in an "s" curve: when the potential is more positive (0.4 to-0.1V), the SWV current is lower and has smaller change, and corresponds to the accumulation layer of the specific I-V curve of the field effect structure; along with the continuous reduction of the potential, the absolute value of the photocurrent is gradually increased, and the photocurrent corresponds to a depletion layer of the field effect structure; the current reaches saturation when the potential is minus 1.2V, and the current corresponds to an inversion layer of a field effect structure.
When the potential scanning range is 0.1 to-1.5V, the amplitude is 0.02V, and the scanning frequency is 200Hz, the ACV photocurrent curve of the pH sensitive semiconductor chip is shown in FIG. 4. As can be seen from fig. 4, the photocurrent also shows the trend of "s" curve with the potential: when the potential is more positive, the current is relatively lower and the change is smaller, and the potential is 0.1 to-0.1V; with the continuous reduction of the potential, the photocurrent gradually increases until the saturation is reached around-1.2V.
When the potential scanning range is 0.4 to-1.2V, the potential amplitude is 0.05V, and the scanning frequency is 1KHz, the optical addressing SWV curve of the pH sensitive semiconductor chip tested in the solution with different pH values is shown in FIG. 5 a; the I-V curve gradually shifts towards the negative potential direction along with the increase of the pH value of the solution; as shown in FIG. 5b, the pH sensitivity was 55.9mV/pH at a constant photocurrent of-100 nA.
When the potential scanning range is 0.3 to-0.8V, the amplitude is 0.02V, and the scanning frequency is 200Hz, the optical addressing ACV curve of the pH sensitive semiconductor chip tested in the solution with different pH values is shown in FIG. 6 a. As the pH of the solution increases, the I-V curve also gradually shifts toward a negative potential. As shown in FIG. 6b, the pH sensitivity was 46.7mV/pH at a constant photocurrent of 405 nA.
When the potential scanning range is-0.4 to-0.8V, the potential amplitude is 0.05V, and the scanning frequency is 100Hz, the SWV curve of the scanning of the focused laser on the SU8 photoresist covered area and the uncovered area on the impedance sensitive semiconductor chip is shown in FIG. 7. Since the SU8 photoresist increases the impedance of the chip surface in situ, the absolute value of the photocurrent is significantly reduced in the current saturation region, i.e., the inversion layer, where the chip surface has SU8 coverage compared to the region without SU 8.
When the potential scanning range is-0.3 to-0.55V, the potential amplitude is 0.1V and the scanning frequency is 10Hz, the ACV curves of the areas covered by the SU8 photoresist and the areas not covered by the SU-8 photoresist of the focused laser on the impedance-sensitive semiconductor chip are shown in FIG. 8, and the impedance of the chip surface can be increased in situ by the SU8 photoresist, so that the photocurrent of the chip surface with the SU8 covering part is remarkably reduced compared with that without the SU8 on the inversion layer.
Taking the SU8 pattern as the center, an optical image was taken using an optical imaging system as shown in fig. 9 a. Taking SU8 pattern as the center, performing xy-direction two-dimensional scanning (step length: 4 μm, dead time: 2.3s, scanning range: 200 μm × 200 μm) by a displacement device, simultaneously performing SWV test (-0.78-0.8V, amplitude 0.05V, scanning frequency 100Hz), and obtaining SWV photocurrent two-dimensional image as shown in FIG. 9b by taking the corresponding position coordinate of-0.8V and SWV current. Since SU8 photoresist increases the impedance of the chip surface in situ, the photocurrent is significantly lower in the area covered by the photoresist. The SWV photo-streaming image can better correspond to the optical image.
By means of linear movement of the displacement device in the x direction (step size: 2 μm, dead time: 2.5s, scanning range: 90 μm), optical addressing SWV scanning is performed on the edges of the pattern of the impedance sensitive semiconductor chip SU8 to-0.78V, amplitude is 0.05V, scanning frequency is 100Hz, and the SWV current magnitude under the corresponding position coordinate of-0.8V is taken to obtain a current-position I-x curve as shown in FIG. 9a, and a curve obtained by differentiating the I-x curve is shown in FIG. 9 b. As can be seen from fig. 9a, since SU8 increases the in-situ impedance of its coverage area, the absolute value of the photocurrent increases dramatically as the laser light moves from the SU8 coverage area to the SU 8-free area. The spatial resolution of the optically addressed SWV is about 5.2 μm, as can be seen by the half-width after the differentiation process.
The invention provides an addressable photoelectrochemical detection method, which uses a beam of constant laser to irradiate a semiconductor field effect structure to generate local photon-generated carriers, and simultaneously uses the SWV or ACV function of an electrochemical workstation to modulate the external voltage of a semiconductor chip to obtain photocurrent through detection. The results show that when silicon nitride is used as the sensitive layer, the detection of the pH value of the solution can be achieved. In addition, the semiconductor chip based on SAMs insulation can be used for in-situ detection and imaging of chip surface impedance. Compared with the traditional electrochemical analysis method, the light-addressable SWV/ACV provided by the invention has certain spatial resolution capability, and provides a solution for high-flux multi-site electrochemical detection.
Claims (10)
1. A light-addressable square wave/alternating current volt-ampere electrochemical sensing system is characterized by comprising a laser device (1), a semiconductor chip (2), a detection cell device (3), an electrochemical detection device (4), a displacement device (5) and an optical imaging device (18); semiconductor chip (2) are fixed in and detect pond device (3) lower extreme, it holds the chamber to be equipped with the through-hole on detecting pond device (3), the through-hole holds the intracavity and is used for placing detection liquid, it can contact with semiconductor chip (2) up end to detect liquid, counter electrode (6) and reference electrode (7) interval of electrochemistry detection device (4) are placed in detecting liquid, working electrode (8) and semiconductor chip (2) lower extreme electricity of electrochemistry detection device (4) are connected, laser device (1) and optical imaging device (18) set up in detecting pond device (3) upper end, the light source of optical imaging device (18) and the laser of laser device (1) can shine in semiconductor chip (2) upper surface through the through-hole appearance chamber, semiconductor chip (2) and detecting pond device (3) are fixed in on displacement device (5).
2. An optically addressed square wave/alternating current volt-ampere electrochemical sensing system according to claim 1, characterized in that the electrochemical detection device (4) comprises an electrochemical workstation, a counter electrode, a reference electrode and a working electrode, wherein the counter electrode, the reference electrode and the working electrode are all connected with the electrochemical workstation, the electrodes are platinum wires, the reference electrode is an Ag/AgCl reference electrode, and the working electrode is connected with a semiconductor chip.
3. An optically addressed square wave/ac volt-ampere electrochemical sensing system as claimed in claim 1, wherein the laser device (1) comprises a laser controller (19), a laser (20), a collimating lens (21), a beam splitter prism (22) and a magnifying objective (23), the magnifying objective (23) is disposed at the upper end of the detection cell device (3), the collimating lens (21) is disposed at the laser emitting end of the laser (20), the beam splitter prism (22) is disposed between the collimating lens (21) and the magnifying objective (23), and the laser is connected to the laser controller.
4. An optically addressed square wave/ac volt-ampere electrochemical sensing system according to claim 1, characterized in that the optical imaging device comprises an LED illumination source (24), a field lens (25) and a CCD camera, the CCD camera is connected with a computer (26), the computer (26) is used for acquiring and storing images, the field lens (25) is arranged at one side of the beam splitter prism (22), and the field lens (25), the beam splitter prism (22) and the magnifying objective lens (23) are in a straight line.
5. An optically addressed square wave/ac volt-ampere electrochemical sensing system according to claim 2, characterized in that the semiconductor chip (2) is a pH sensitive semiconductor chip or an impedance sensitive semiconductor chip.
6. An optically addressed square wave/ac volt-ampere electrochemical sensing system according to claim 5, characterized in that the pH sensitive semiconductor chip comprises a sensitive layer (9), an insulating layer (10), a semiconductor layer (11) and an ohmic contact layer (12) stacked in sequence from top to bottom, the ohmic contact layer (12) is electrically connected to the working electrode (8) of the electrochemical detection device (4), the sensitive layer (9) is in contact with the electrolyte in the detection cell device (3), the impedance sensitive semiconductor chip comprises an insulating layer (10), a semiconductor layer (11) and an ohmic contact layer (12) stacked in sequence from top to bottom, the ohmic contact layer (12) is electrically connected to the working electrode (8) of the electrochemical detection device (4), and the insulating layer (10) is in contact with the electrolyte in the detection cell device (3).
7. The optical addressing square wave/alternating current volt-ampere electrochemical sensing system according to claim 1, characterized in that the detection cell device (3) comprises a detection cavity (13) and an electrical connection sheet (14), wherein the detection cavity (13) is provided with a through hole cavity, the semiconductor chip (2) is in sealing contact with the lower end surface of the detection cavity (13), the electrical connection sheet (14) is arranged at the lower end of the semiconductor chip (2), and the electrical connection sheet (14) is electrically connected with the semiconductor chip (2).
8. An optically addressed square wave/AC volt-ampere electrochemical test method based on the optically addressed square wave/AC volt-ampere electrochemical sensing system as claimed in claim 5, characterized by comprising the following steps:
s1, fixing the detection cell device fixed with the pH sensitive semiconductor chip on the displacement device, and adding buffer salt electrolytes with different pH values into a through hole cavity of the detection cell device; putting a counter electrode and a reference electrode of the electrochemical detection device into electrolyte, and connecting a working electrode with an ohmic contact layer of the pH sensitive semiconductor chip;
s2, adjusting the displacement device to enable the laser generated by the laser to irradiate the upper end of the pH sensitive semiconductor chip through the through hole cavity of the detection cell device, and enabling the laser focus point to be located at the position of 0.8-1.2cm of the surface of the semiconductor;
and S3, sequentially carrying out SWV and ACV electrochemical tests on the solutions with different pH values by adopting an electrochemical workstation to obtain a dark/light current-potential curve, thereby completing addressing square wave/alternating current volt-ampere electrochemical sensing detection.
9. An optically addressed square wave/ac volt-ampere electrochemical imaging method based on the optically addressed square wave/ac volt-ampere electrochemical sensing system as claimed in claim 5, comprising the steps of:
s1, fixing the detection cell device fixed with the impedance sensitive semiconductor chip on the displacement device, and adding electrolyte into the detection cell device; putting a counter electrode and a reference electrode of the electrochemical detection device into electrolyte, and connecting a working electrode with an ohmic contact layer of the impedance sensitive semiconductor chip through an electric connection sheet;
s2, adjusting the displacement device to enable the laser generated by the laser to irradiate the surface of the impedance sensitive semiconductor chip through the through hole cavity of the detection cell device and enable the laser focus point to be positioned on the surface of the semiconductor chip;
s3, sequentially carrying out SWV and ACV electrochemical tests by adopting an electrochemical workstation to respectively obtain I-V curves of the tested SWV and ACV;
s4, adjusting the displacement device, observing through the optical imaging system, making the semiconductor chip perform two-dimensional scanning on a horizontal plane relative to the laser by taking the photoetching pattern as the center, and taking the SWV photocurrent under the fixed potential of the corresponding coordinate, thereby obtaining the photocurrent distribution image of the photoetching pattern, namely the photoaddressing square wave volt-ampere electrochemical impedance diagram.
10. The method of claim 9, wherein the displacement device is adjusted to move the electric semiconductor chip linearly in a horizontal direction relative to the laser to perform SWV scanning on the edge of the lithographic pattern on the semiconductor chip to obtain a current-position curve at a fixed potential, and the current-position curve is subjected to differential processing to obtain a half-peak width, which is the spatial resolution of the photo-addressable square wave voltammetric impedance imaging.
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