Nanoscale photoelectric response measurement system and method

Abstract

The present invention discloses a nanoscale photoelectric response measurement system and method, wherein the system includes an excitation light source, a nanoprobe sensor, a nanomobile platform and a control module, wherein the nanoprobe sensor includes a nanocantilever and a nanoprobe, the nanomobile platform is rigidly connected to the nanocantilever, and the control module is connected to the nanomobile platform; the excitation light source is used to irradiate the light source onto the photoelectric device; the nanomobile platform is used to control the nanoprobe to move above the photoelectric device; the nanoprobe is used to collect the photoinduced image force of a preset area on the photoelectric device; the control module is used to control the nanomobile platform and obtain the photoelectric response value of the photoelectric device according to the collected photoinduced image force. The present invention measures the photoelectric response value of the photoelectric device by collecting the photoinduced image force, avoids the influence of external noise, improves the measurement sensitivity and the photoelectric response spatial resolution, and can be widely used in the field of photoelectric response measurement.

Description

Technical Field

[0001] The present invention relates to the field of photoelectric response measurement, and in particular to a nanoscale photoelectric response measurement system and method. Background Art

[0002] Solar energy is a renewable energy resource development method that my country attaches great importance to, and it is also the fastest industrialized new energy. Photovoltaic cells can already achieve sufficiently high power generation efficiency, but they occupy too much area and the power generation is not stable enough. Therefore, new high-performance energy conversion materials such as photoelectric conversion are the core and original driving force of energy conversion devices. Especially with the development of nanomaterial technology, high-efficiency photoelectric conversion technology based on nanomaterials has always been a hot spot in scientific research.

[0003] In the field of signal detection, photoelectric sensors are key components for realizing photoelectric conversion in various photoelectric detection systems. They can be used to detect non-electrical physical quantities that directly cause changes in light quantity, such as light intensity, illuminance, radiation temperature measurement, gas composition analysis, etc.; they can also be used to detect other non-electrical quantities that can be converted into changes in light quantity, such as part diameter, surface roughness, strain, displacement, vibration, speed, acceleration, as well as the shape of objects, identification of working status, etc. Photoelectric sensors have the characteristics of non-contact, fast response, and reliable performance, so they are widely used in industrial automation devices and robots. With the development of industrial technology, the demand for ultra-limit photoelectric sensors is increasing, such as ultra-fast and ultra-high sensitivity photoelectric sensors. Due to the characteristics of low noise and high signal-to-noise ratio of low-dimensional nanomaterials, nanomaterial photoelectric sensors will dominate the development of ultra-limit photoelectric sensors in the future.

[0004] At present, there are two main ways to measure the photoelectric response of nanomaterials. The first is to use a conductive cantilever beam and a probe to scan and collect the surface potential of each point, thereby providing the composition and electronic state information of the local structure of the surface. The second is scanning photocurrent imaging, which uses precise optical focusing technology to achieve very small light aggregation, and then scans the sample point by point, while measuring the corresponding light response. It is the most direct way to react to the macroscopic photoelectric properties of the material. However, this method of current collection has the following disadvantages: the photoelectric sensing area of ​​nanoscale photoelectric devices is nanoscale. Due to the small photoelectric absorption area and low photoelectric conversion efficiency, the photocurrent generated is usually relatively weak. The photocurrent of nanophotoelectric devices is usually only nanoamperes (10^-9 amperes) or picoamperes (10^-12 amperes), so the influence of external interference on the measurement results is very serious, resulting in a very low signal-to-noise ratio, affecting the measurement accuracy. Another disadvantage is that the optical focusing is at the micron level, and the spatial resolution after point-by-point scanning is still at the micron level, which cannot accurately reflect the photoelectric response distribution of nanomaterial photoelectric devices. Summary of the invention

[0005] In order to solve one of the above technical problems, the purpose of the present invention is to provide a nanoscale photoelectric response measurement system and method, which converts the effect of the photoelectric field into atomic force through a photoinduced mirror force field to achieve the measurement of nanoscale photoelectric response.

[0006] The technical solution adopted by the present invention is:

[0007] A nanoscale photoelectric response measurement system comprises an excitation light source, a nanoprobe sensor, a nanomobile platform and a control module, wherein the nanoprobe sensor comprises a nanocantilever and a nanoprobe, the nanomobile platform is rigidly connected to the nanocantilever, and the control module is connected to the nanomobile platform;

[0008] The excitation light source is used to irradiate the light source onto the photoelectric device, so as to generate a photoinduced mirror force between the photoelectric device and the nanoprobe;

[0009] The nano mobile platform is used to control the movement of the nano probe above the optoelectronic device;

[0010] The nanoprobe is used to collect the photoinduced image force of a preset area on the optoelectronic device;

[0011] The control module is used to control the nano mobile platform and obtain the photoelectric response value of the photoelectric device according to the collected photoinduced image force.

[0012] Furthermore, the tip size of the nanoprobe is 1-10 nanometers.

[0013] Furthermore, the excitation light source adopts a continuous spectrum fiber laser.

[0014] Furthermore, the control module includes an atomic force microscope.

[0015] Another technical solution adopted by the present invention is:

[0016] A method for measuring nanoscale photoelectric response comprises the following steps:

[0017] irradiating a light source onto the optoelectronic device to generate a photoinduced mirror force between the optoelectronic device and the nanoprobe;

[0018] Controlling the nanoprobe to move above the optoelectronic device to collect the photoinduced image force of a preset area on the optoelectronic device;

[0019] The photoelectric response value of the photoelectric device is obtained according to the collected photoinduced image force.

[0020] Furthermore, the step of irradiating the light source onto the photoelectric device to generate a photoinduced mirror force between the photoelectric device and the nanoprobe is specifically as follows:

[0021] A modulated laser light source pulse light source is used to irradiate the optoelectronic device, so as to generate a photoinduced mirror force with a preset frequency peak between the optoelectronic device and the nanoprobe.

[0022] Further, the method further comprises the following steps:

[0023] Under the condition that there is no light source irradiating the optoelectronic device, controlling the nanoprobe to move above the optoelectronic device;

[0024] The atomic force at each moving point is recorded to obtain the first scanning image of the optoelectronic device.

[0025] Furthermore, the step of controlling the nanoprobe to move above the optoelectronic device to collect the photoinduced image force of a preset area on the optoelectronic device is specifically as follows:

[0026] dividing a photosensitive area of ​​the optoelectronic device into a plurality of areas according to the first scanned image;

[0027] The nanoprobe is controlled to move to each area in turn to collect the photoinduced image force of the area until the photoinduced images of all areas are collected.

[0028] Furthermore, the step of obtaining the photoelectric response value of the photoelectric device according to the collected photoinduced image force is specifically as follows:

[0029] Subtracting the collected photoinduced image force from the atomic force recorded in the first scanning image to obtain a force difference value;

[0030] The photoelectric response value of the photoelectric device is obtained according to the force difference value.

[0031] Furthermore, the step of controlling the nanoprobe to move to each region in sequence is specifically as follows:

[0032] When it is detected that the peak value of the photoinduced image force collected in the current area reaches a preset value, the nanoprobe is controlled to move to the next area for collection.

[0033] The beneficial effects of the present invention are as follows: the present invention measures the photoelectric response value of the photoelectric device by collecting the photoinduced image force, thereby avoiding the influence of external noise and greatly improving the measurement sensitivity and the spatial resolution of the photoelectric response. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 is a flow chart of the steps of a method for measuring nanoscale photoelectric response in an embodiment;

[0035] Figure 2 is a schematic diagram of the operation of the response measurement system in the embodiment;

[0036] Figure 3 is a schematic diagram of enhancing incident light at the probe tip in an embodiment;

[0037] Figure 4 is a side view of an optoelectronic device in an embodiment;

[0038] Figure 5 Schematic diagram of laser timing and photoinduced image force in an embodiment. DETAILED DESCRIPTION

[0039] Reference Figure 2 , this embodiment provides a nanoscale photoelectric response measurement system, including an excitation light source 1, a nanoprobe sensor, a nanomobile platform and a control module, wherein the nanoprobe sensor includes a nanocantilever 3 and a nanoprobe 4, the nanomobile platform is rigidly connected to the nanocantilever 3, and the control module is connected to the nanomobile platform;

[0040] The excitation light source is used to irradiate the light source onto the photoelectric device, so as to generate a photoinduced mirror force between the photoelectric device and the nanoprobe;

[0041] The nano mobile platform is used to control the movement of the nano probe above the optoelectronic device;

[0042] The nanoprobe is used to collect the photoinduced image force of a preset area on the optoelectronic device;

[0043] The control module is used to control the nano mobile platform and obtain the photoelectric response value of the photoelectric device according to the collected photoinduced image force.

[0044] The nano mobile platform is used to control two-dimensional or three-dimensional movement on the surface of the optoelectronic device. A number of brakes are arranged in the nano mobile platform. The brake can be a piezoelectric tube brake (piezoelectric crystal). The brake controls the nano probe to move above the optoelectronic device. The existing technology is to obtain the photoelectric response value of the optoelectronic device by collecting the current on the optoelectronic device. However, since the current is very small (reaching the picoampere level), it is very susceptible to external noise, so the photoelectric response value of the optoelectronic device cannot be accurately measured. In this embodiment, a method is adopted to convert the effect of the photoelectric field into atomic force through a photoinduced mirror force field to achieve the measurement of nanoscale photoelectric response. Refer to Figure 2 The nanoprobe does not need to contact the optoelectronic device, nor does it need to conduct electricity. When the optoelectronic device generates photogenerated carriers, the nanoprobe 4 interacts with the photosensitive area 5 of the optoelectronic device, and the probe and the device surface directly form a photoinduced image force in pN. This tiny force will cause the probe to deform, and the photoelectric response of the point can be determined by measuring the deformation. In addition, refer to Figure 3When the incident light is irradiated at the tip of the nanometer-scale sharp metal probe with appropriate wavelength and polarization, under the combined effect of the local surface plasmon resonance effect, the lightning rod effect and the antenna effect, a strong local electromagnetic field enhancement will be generated within a few nanometers to more than ten nanometers around the needle tip. At this time, the metal needle tip can be regarded as a nano light source with extremely high power, so that the force is better exerted on the area of ​​the optoelectronic device under the needle tip, greatly improving the measurement sensitivity. In this embodiment, the photoelectric response value of the optoelectronic device is measured by collecting the photoinduced image force, avoiding the influence of external noise, so the photoelectric response value of a smaller optoelectronic device can be measured, such as the photoelectric response value of a certain area of ​​a certain optoelectronic device, thereby improving the measurement sensitivity. Among them, the external pin 2 of the optoelectronic device is a metal conductive pin that can be connected to an external circuit, and the photosensitive area 5 is the area where the photoelectric response measurement is required.

[0045] In addition, the spatial resolution of traditional scanning photocurrent imaging depends on the size of the scanning spot. The scanning spot is usually achieved by focusing an optical lens, and its size is limited by the optical wavelength and the Rayleigh diffraction limit. The ideal spot size is also submicron. The scale of nanoscale devices / nanomaterial optoelectronic devices is 1-100 nanometers. In order to achieve spatial resolution, the measurement resolution scale should be less than 10 nanometers. Another reason for the low spatial resolution is that the scanning control accuracy of the scanning controller is limited; in traditional methods, the movement of the spot depends on the position movement of the light source (usually a laser), and its control accuracy also limits the spatial resolution of the final scanning imaging. In this example, there is no requirement for the size of the spot. The resolution of this example mainly depends on the size of the nanoprobe. When the nanoprobe is small enough, the nanometer size can be detected, which improves the spatial resolution.

[0046] Regarding photoinduced image force, in 2005, Dazzi et al. pioneered the use of atomic force needle tips as sensors for photoelectric absorption. The experiment was as follows: polymer materials generate heat under infrared light irradiation, which causes local expansion of the material. The probe of the atomic force microscope can accurately measure local deformation (10-50 picometers) and convert the expansion into infrared absorption. The infrared absorption spectrum can be measured by changing the wavelength within the range allowed by the light source. The displacement of infrared absorption thermal expansion needs to be amplified by contact resonance, and infrared excitation can use pulsed lasers to achieve the feasibility of measurement. An important breakthrough in molecular spectroscopy recently came from the Wickramasinghe team. In 1991, Wickramasinghe proposed the concept of polarizing the atomic probe under the incident light field and generating an image force. The image force is very weak, about a few to tens of piconewtons. The team proposed a dual-frequency modulation mechanism, using tapping mode to detect photoinduced image force. Tapping mode is the most commonly used imaging mode of atomic force microscopy and is also widely used in nanoscale-related industries.

[0047] As a further optional embodiment, the tip size of the nanoprobe is 1-10 nanometers.

[0048] In this embodiment, the tip enhancement effect of the nanoprobe is used. The tip of the nanoprobe is usually 3-5 nanometers, and some are thinner. The enhancement effect is greatest at the tip of the needle, so the measurement of each point can be controlled below 3 nanometers. The traditional method uses spot scanning, and each spot is at least several hundred nanometers. In addition, when measuring the photoelectric response, this embodiment does not directly measure the photocurrent, but converts the photoelectric response to the photoinduced image force, and calculates the photocurrent by measuring the magnitude of the force. The sensitivity of the photoinduced image force is much higher than that of directly measuring the photocurrent, which greatly improves the sensitivity of the measurement.

[0049] As a further optional implementation, the excitation light source adopts a continuous spectrum fiber laser.

[0050] As a further optional implementation, the control module includes an atomic force microscope.

[0051] like Figure 1 As shown, this embodiment also provides a method for measuring nanoscale photoelectric response, comprising the following steps:

[0052] S1. Obtaining the morphological characteristics of optoelectronic devices;

[0053] First, the first image scan is performed on the measured photoelectric device through the atomic force microscope system. There is no laser light source excitation in this scanning imaging. The scanned image is used as the feedforward information of the initial pre-image, and is used for planning the path and calculating the photoelectric response value. Specifically, it includes steps S11-S12:

[0054] S11, controlling the nanoprobe to move above the optoelectronic device without irradiating the optoelectronic device with a light source;

[0055] S12. Record the atomic force at each moving point to obtain a first scanning image of the optoelectronic device.

[0056] In the first scan, the atomic force probe is used to scan the entire sample. There is no laser light source pulse during this scan. The morphological characteristics of the optoelectronic device sample can be obtained, such as length, width and height. The surface of the optoelectronic device is usually not completely flat, such as Figure 4 shown.

[0057] S2, irradiating the light source onto the photoelectric device to generate a photoinduced mirror force between the photoelectric device and the nanoprobe;

[0058] The light source can be a common laser or any light source that can generate a wavelength that the photoelectric device responds to. When the light source irradiates the photoelectric device, the photoelectric device will generate a corresponding current. In order to improve the sensitivity of the signal, a modulated excitation signal is used to achieve ultra-high sensitivity measurement. The specific steps are as follows:

[0059] A modulated laser light source pulse light source is used to irradiate the optoelectronic device, so as to generate a photoinduced mirror force with a preset frequency peak between the optoelectronic device and the nanoprobe.

[0060] Reference Figure 5 , the timing control of the laser light source pulse is shown in (a). (b) is the force of the normal peak force tapping mode; (a) is a laser pulse with a frequency of f, where the frequency of the peak force measurement is 2N times the laser light source pulse, and N can be 1-128. By subtracting the peak force measured during laser excitation from the peak force without laser excitation, the mirror force result of laser excitation can be obtained. The excitation light source can be a continuous spectrum fiber laser, and its external modulation frequency can be adjusted from 1 Hz to tens of kilohertz.

[0061] Peak force tapping mode is a scanning probe imaging method based on atomic force microscopy. The trajectory of the atomic force probe tip is completely controlled by an external piezoelectric crystal. The measurement system observes the instantaneous force acting on the sample at any time during the process of the tip approaching the sample. Once the peak force reaches the set value, the feedback loop forces the tip to leave the sample through the piezoelectric crystal to prepare for the next measurement cycle. The characteristic of peak force tapping mode is that the time of interaction between the tip and the sample is fully controllable. By setting the measurement time, the signal-to-noise ratio of the image force can be improved.

[0062] S3, controlling the nanoprobe to move above the optoelectronic device to collect the photoinduced image force of a preset area on the optoelectronic device;

[0063] Pre-plan the moving path of the nanoprobe on the optoelectronic device, and then control the movement of the nanoprobe, as shown in steps S31-S32:

[0064] S31, dividing a photosensitive area of ​​the optoelectronic device into a plurality of areas according to the first scan image;

[0065] S32, controlling the nanoprobe to move to each region in turn, and collecting the photoinduced image force of the region, until the photoinduced images of all regions are collected.

[0066] Reference Figure 4, from point A to point B, the heights of A and B can be obtained through the first scan. During the first scan, there is no light excitation, and there is no photoinduced mirror force. At this time, the measured height and position information are the most accurate. During the second scan, the atomic probe measures the superposition of the photoinduced mirror force and the height information. For example, the distance from point A to point B is 5nm, which can be accurately obtained through the first scan. During the second scan, point A is 5 nanometers to the right. The XY coordinate position of the probe is controlled by the nano-mobile platform so that it stops precisely at point B. This ensures that the image scanned by the final XY coordinate corresponds to the first scan image of the device.

[0067] Specifically, the photosensitive area of ​​the optoelectronic device can be divided into m rows and n columns, and the nanoprobe is controlled to first scan the n areas in the first row, and then scan the n areas in the second row, and so on, until all areas are scanned to obtain a second scanned image.

[0068] The step of controlling the nanoprobe to move to each region in sequence is specifically as follows:

[0069] When it is detected that the peak value of the photoinduced image force collected in the current area reaches a preset value, the nanoprobe is controlled to move to the next area for collection.

[0070] As the probe tip approaches the sample, the measurement system observes the instantaneous force acting on the sample at any time. Once the peak force reaches the set value, the feedback loop forces the tip to leave the sample through the piezoelectric crystal to prepare for the next measurement cycle. The peak force tapping mode is characterized by the fully controllable interaction time between the tip and the sample. By setting the measurement time, the signal-to-noise ratio of the image force can be improved.

[0071] S4. Obtaining a photoelectric response value of the photoelectric device according to the collected photoinduced image force.

[0072] In the second scanning image acquisition, the laser signal is introduced to achieve high-precision position positioning. Specifically, as shown in steps S41-S42:

[0073] S41, subtracting the collected photoinduced image force from the atomic force recorded in the first scanning image to obtain a force difference;

[0074] S42. Obtain a photoelectric response value of the photoelectric device according to the force difference value.

[0075] The image force result for laser excitation is obtained by subtracting the peak force measured during laser excitation from the peak force without laser excitation.

[0076] In summary, compared with the existing photoelectric response measurement technology, this embodiment has at least the following beneficial effects:

[0077] (1) All current solutions measure the overall current of the optoelectronic device or scan a large area, which limits the sensitivity of the measurement. This embodiment indirectly measures the photoelectric response of the nanoscale optoelectronic device through the mirror force, which can achieve a photoelectric response measurement with a spatial resolution of 1 nanometer. The spatial resolution of the device response is greatly improved, which can provide accurate guidance for the design and manufacture of nanoscale devices.

[0078] (2) This embodiment performs frequency modulation on the excitation light signal and the measurement peak force signal so that they work at different frequencies, but their working frequencies are in a 2N-fold frequency relationship, thereby achieving ultra-high-precision measurement of photoinduced mirror force and improving the sensitivity of the measurement signal.

[0079] (3) This embodiment uses a double scanning imaging method and uses the first scan as a feedforward control signal to achieve high-precision position control.

[0080] The above is a specific description of the preferred implementation of the present invention, but the invention is not limited to the embodiments. Those skilled in the art can make various equivalent modifications or substitutions without violating the spirit of the present invention. These equivalent modifications or substitutions are all included in the scope defined by the claims of this application.

Claims

1. A nanoscale photoelectric response measurement system, It is characterized in that It includes an excitation light source, a nanoprobe sensor, a nanomobile platform and a control module, wherein the nanoprobe sensor includes a nanocantilever and a nanoprobe, the nanomobile platform is rigidly connected to the nanocantilever, and the control module is connected to the nanomobile platform; The excitation light source is used to irradiate the light source onto the photoelectric device, so as to generate a photoinduced mirror force between the photoelectric device and the nanoprobe; The nano mobile platform is used to control the movement of the nano probe above the optoelectronic device; The nanoprobe is used to collect the photoinduced image force of a preset area on the optoelectronic device; The control module is used to control the nano mobile platform and obtain the photoelectric response value of the photoelectric device according to the collected photoinduced image force; The tip size of the nanoprobe is 1-10 nanometers. When measuring the photoelectric response, the photoelectric response is converted into a photoinduced image force, and the photocurrent is calculated by measuring the magnitude of the force. Among them, when the incident light with a preset wavelength and polarization is irradiated on the tip of a sharp metal probe at the nanoscale, a local electromagnetic field enhancement is generated in the range near the tip. At this time, the metal tip is regarded as a nano light source, thereby exerting better force on the area of ​​the optoelectronic device under the tip.

2. A nanoscale photoelectric response measurement system according to claim 1, It is characterized in that The excitation light source adopts a continuous spectrum fiber laser.

3. A nanoscale photoelectric response measurement system according to claim 1, It is characterized in that The control module includes an atomic force microscope.

4. A nanoscale photoelectric response measurement method, applied to a nanoscale photoelectric response measurement system as claimed in any one of claims 1 to 3, It is characterized in that The following steps are involved: irradiating a light source onto the optoelectronic device to generate a photoinduced mirror force between the optoelectronic device and the nanoprobe; Controlling the nanoprobe to move above the optoelectronic device to collect the photoinduced image force of a preset area on the optoelectronic device; The photoelectric response value of the photoelectric device is obtained according to the collected photoinduced image force.

5. A nanoscale photoelectric response measurement method according to claim 4, It is characterized in that The step of irradiating the light source onto the photoelectric device to generate a photoinduced mirror force between the photoelectric device and the nanoprobe is specifically as follows: A modulated laser light source pulse light source is used to irradiate the optoelectronic device, so as to generate a photoinduced mirror force with a preset frequency peak between the optoelectronic device and the nanoprobe.

6. A method for measuring nanoscale photoelectric response according to claim 5, It is characterized in that The following steps are also included: Under the condition that there is no light source irradiating the optoelectronic device, controlling the nanoprobe to move above the optoelectronic device; The atomic force at each moving point is recorded to obtain the first scanning image of the optoelectronic device.

7. A method for measuring nanoscale photoelectric response according to claim 6, It is characterized in that The step of controlling the nanoprobe to move above the optoelectronic device to collect the photoinduced image force of a preset area on the optoelectronic device is specifically: dividing a photosensitive area of ​​the optoelectronic device into a plurality of areas according to the first scanned image; The nanoprobe is controlled to move to each area in turn to collect the photoinduced image force of the area until the photoinduced images of all areas are collected.

8. A method for measuring nanoscale photoelectric response according to claim 7, It is characterized in that The step of obtaining the photoelectric response value of the photoelectric device according to the collected photoinduced image force is specifically as follows: Subtracting the collected photoinduced image force from the atomic force recorded in the first scanning image to obtain a force difference value; The photoelectric response value of the photoelectric device is obtained according to the force difference value.

9. A method for measuring nanoscale photoelectric response according to claim 7, It is characterized in that The step of controlling the nanoprobe to move to each region in sequence is specifically as follows: When it is detected that the peak value of the photoinduced image force collected in the current area reaches a preset value, the nanoprobe is controlled to move to the next area for collection.

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