Real-time in-situ spectral integrated measurement method and device based on single-sided single reflection

Abstract

The application discloses a kind of real-time in-situ spectral integrated measurement method and device based on single-sided single reflection.The application directly calculates the light intensity transmittance of film by measuring the reflectivity of film-reflector system on single side, without knowing the dielectric constant of film material and the thickness of film in advance;The transmittance spectrum of film can be obtained by measuring the transmittance of film at different wavelengths;This process only measures the reflected light intensity of film-reflector system once, without involving the amplitude superposition of light or the interference of light;More importantly, the incident light and the light returned by reflector are collinear, and all on the same side of the sample, which makes the entire measurement system very compact and easy to integrate;Further increase the incident angle, the light reflected by film surface and the light reflected by reflector will not be measured by the system, so the measurement device can directly measure the fluorescence spectrum of film under the excitation of continuous light or monochromatic light.

Description

Technical Field

[0001] The present invention relates to an optical thin film measurement technology, and in particular to a real-time in-situ spectrum integrated measurement method based on single-side single reflection and an integrated measurement device thereof. Background Art

[0002] Thin films are widely used in modern photonics and optoelectronics technologies, such as photovoltaics, storage, and chips. They can be used to manufacture a variety of optoelectronic devices, chips, and instruments. Thin film properties, such as material properties, thickness, and uniformity, are crucial to the performance of optoelectronic devices and chips. The optical properties of a material can be characterized by measuring transmittance or absorbance. Furthermore, integrating thin film transmittance or absorbance measurements with film-forming equipment allows for real-time, in-situ measurement of the film growth process. This allows for studying the dynamics of the film-forming process, which is crucial for understanding and optimizing device functionality.

[0003] There are two main methods for measuring the transmittance or absorbance of thin films: reflection and transmission. Both film thickness meters and ellipsometers based on reflection systems use the principle of thin film interference to study the properties of thin films, such as film thickness and the complex refractive index of the material, by measuring the reflected light of the thin film. The transmittance or absorbance of the film can be further calculated based on the film thickness and the complex refractive index of the material. The physical essence of this reflection system instrument (ellipsometer and film thickness meter) is based on multiple reflections of light at the interface of different materials. The interference spectrum is obtained by superimposing the amplitudes of these reflected lights, and then a complex fitting formula is used to obtain the film thickness or complex refractive index. This method requires knowing one of the parameters of the film thickness and complex refractive index in order to fit the other parameter through the formula. Although the probe of this film thickness meter is very small (about 30mm 2 ), which is easy to integrate, but in the process of thin film material growth, the two parameters of film thickness and material properties are unknown, so it is impossible to fit the interference spectrum, and thus the film thickness meter cannot achieve real-time in-situ measurement of the film growth process. In addition, for a single-wavelength light source, it is impossible to fit it with a formula, and the film thickness meter cannot obtain the complex refractive index of the material at a single wavelength. The ellipsometer is based on measuring the change in the polarization state of the reflected light of the thin film, using precise optical models and complex calculations to simultaneously solve the film thickness and the complex refractive index of the material, thereby achieving real-time in-situ measurement of the thin film. However, this reflective ellipsometer requires a large oblique light incidence (the incident angle θ is about 70°), and a detector or spectrometer must be set at the corresponding angular position (-θ, the reflected light beam position), which makes the entire optical system bulky and difficult to integrate.

[0004] Film thickness meters and ellipsometers based on reflection systems don't utilize the transmitted light portion and cannot directly measure the transmittance of thin films. Transmission-based instruments such as spectrophotometers can directly measure the transmittance or absorbance of thin films. These transmission systems require incident light from one side of the sample and collection of the transmitted light from the other side to perform the measurement. This configuration makes the entire measurement system bulky and difficult to integrate. Typically, integrating a transmission system with a device requires modification of the device being integrated, significantly impacting its versatility and practicality. For example, integrating a transmission system with a dual-fiber tip into a spin coater or heated annealing station requires drilling a hole through the center of the spin coater or heated annealing station, extending from bottom to top, to accommodate one of the fiber tips and allow the light beam to pass through. However, some film-forming equipment, such as large-area coaters and vacuum heating / cooling coating systems (molecular beam epitaxy (MBE) and electron beam evaporation (Ebeam)), is not easily accessible through-holes, making integration with transmission systems difficult. In summary, it is still a huge challenge to obtain a method and device that is small in size, easy to integrate, and can measure the transmittance (or absorbance) of a thin film in real time and in situ. Summary of the Invention

[0005] In order to solve the above-mentioned problems, the present invention proposes a real-time in-situ spectral integrated measurement method based on single-sided single reflection and an integrated measurement device thereof. The single-sided single reflection method is used to realize real-time in-situ measurement of the transmission spectrum of the thin film without knowing the complex refractive index and film thickness of the thin film material in advance; further, the measurement device is integrated with a commonly used spin coater and a heating annealing table without the need to modify the integrated instrument. The experiment demonstrates real-time in-situ spectral monitoring of the transmission spectrum during the growth of the perovskite film.

[0006] One object of the present invention is to provide a real-time in-situ spectral integrated measurement method based on single-side single reflection.

[0007] The real-time in-situ spectral integrated measurement method based on single-side single reflection of the present invention comprises the following steps:

[0008] 1) Build a real-time in-situ spectral integrated measurement device:

[0009] The film to be measured is placed on a transparent substrate with the environment above the film; the transmittance of the substrate T s ≥5%;

[0010] The substrate is placed on a reflective surface to form a film-reflective surface system, and the reflective surface is placed on a sample stage; the reflective surface is a flat reflective surface or a curved reflective surface; when the reflective surface is a flat reflective surface, the angle between the film surface to be measured and the plane where the reflective surface is located is the tilt angle β; when the reflective surface is a curved reflective surface, the angle between the film surface to be measured and the tangent plane of the reflection point is the tilt angle β, β>0;

[0011] An incident light path and an outgoing light path are arranged above the film; a light source is coupled to the incident light path, an end of the outgoing light path is coupled to a detector or a spectrometer, and the detector or the spectrometer is connected to a computer;

[0012] 2) Beam propagation:

[0013] Parallel beam: The light emitted by the light source is collimated and becomes a parallel beam that is incident on the film through the incident light path. The light intensity of the beam is I0. The incident light is incident on the surface of the film at an incident angle α, α=β>0. Part of the light is reflected into the environment, and the other part of the light is refracted by the film and the substrate and then perpendicularly incident on the reflecting surface. It is then perpendicularly reflected by the reflecting surface and returns along the original path. Finally, it is refracted from the upper surface of the film into the environment.

[0014] Divergent beam: The light emitted by the light source is not collimated to form a divergent beam that is incident on the film through the incident light path. The light intensity of the beam is I0, and the divergence angle is γ = arcsin (NA). NA is the numerical aperture of the optical fiber or lens in the output light path. The central ray of the divergent beam, i.e., the principal ray, is incident on the surface of the film at an incident angle α. α>arcsin (NA) and α≥β>

[0015] 0, part of the light is reflected into the environment, and the part of the divergent light beam that is perpendicular to the reflecting surface, that is, the light with an angle of (α-β) with the main light, is refracted by the film and the substrate and is vertically incident on the reflecting surface. It is then vertically reflected by the reflecting surface and returns along the original path, and finally refracted from the upper surface of the film into the environment;

[0016] 3) Beam reception:

[0017] The light beam refracted from the upper surface of the film-reflecting surface system into the environment is received by a detector or spectrometer via the outgoing optical path, and the light intensity I of the light beam refracted from the upper surface of the film-reflecting surface system into the environment is obtained. R ;

[0018] 4) Light intensity formula:

[0019] The intensity I of the light beam refracted from the upper surface of the film-reflector system to the environment R satisfy:

[0020] I R =I0×T×T s ×R m ×T s ×T

[0021] Where T is the light transmittance of the film, T s is the light transmittance of the substrate, R m is the light intensity reflectivity of the reflecting surface;

[0022] 5) Reflectivity formula:

[0023] According to the light intensity formula in step 4), the reflectivity R of the film-reflecting surface system is obtained as:

[0024]

[0025] 6) Obtain transmittance:

[0026] According to the known light intensity transmittance T of the substrate s and the light intensity reflectivity R of the reflecting surface m , using the reflectivity formula in step 5), the light intensity transmittance T of the film is further obtained:

[0027]

[0028] Therefore, the light intensity transmittance T of the film can be directly calculated by measuring the reflectivity R of the film-reflecting surface system without knowing the complex refractive index of the film material and the thickness of the film in advance. This method is suitable for real-time in-situ measurement during the film growth process.

[0029] Wherein, in step 1), the reflective surface is a reflective mirror or a reflective film. The sample stage is a bracket, a support frame, a support shell or a block support.

[0030] The light source uses a multi-wavelength light source to directly measure the film transmittance spectrum; or the light source uses a monochromatic light source to measure the film transmittance at one wavelength.

[0031] The incident light path and the outgoing light path adopt an optical fiber transmission system or a free space transmission system. When the optical fiber transmission system is adopted, the incident light path adopts an incident optical fiber, and the outgoing light path adopts an outgoing optical fiber. When the free space transmission system is adopted, the incident light path adopts a first lens, and the outgoing light path adopts a second lens. In the incident light path, the incident light is collimated by the first lens and then incident on the upper surface of the film through a beam splitter. In the outgoing light path, the outgoing light is collected by the second lens after passing through the beam splitter and coupled to a detector or spectrometer. The beam splitter adopts a beam splitter prism or a beam splitter.

[0032] In step 2), for a parallel light beam, when α=β>0, the reflected light from the upper and lower surfaces of the film cannot return along the original path to be collected and measured by the measurement system, and only the light reflected perpendicularly by the reflecting surface returns along the original path to be collected; for a divergent light beam, when α is greater than arcsin (NA), the reflected light from the upper and lower surfaces of the film cannot enter the optical fiber or lens to be collected by it, and only the light reflected perpendicularly by the reflecting surface returns along the original path to be collected; where NA is the numerical aperture of the optical fiber or lens.

[0033] Another object of the present invention is to provide a real-time in-situ spectral integrated measurement device based on single-side single reflection.

[0034] The real-time in-situ spectral integrated measurement device based on single-side single reflection of the present invention comprises: a substrate, a reflective surface, a sample stage, a light source, an incident light path, an outgoing light path, a detector or a spectrometer, and a computer;

[0035] The film to be measured is placed on a transparent substrate, with the environment above the film; the transmittance of the substrate T s ≥5%;

[0036] The substrate is placed on a reflective surface to form a film-reflective surface system, and the reflective surface is placed on a sample stage; the reflective surface is a flat reflective surface or a curved reflective surface; when the reflective surface is a flat reflective surface, the angle between the surface of the film to be measured and the plane on which the reflective surface is located is the tilt angle β; when the reflective surface is a curved reflective surface, the angle between the surface of the film to be measured and the tangent plane of the reflection point is the tilt angle β, β>0;

[0037] An incident light path and an outgoing light path are arranged on the film; a light source is coupled to the incident light path, an end of the outgoing light path is coupled to a detector or a spectrometer, and the detector or the spectrometer is connected to a computer;

[0038] When the light emitted by the light source is collimated and becomes a parallel beam that is incident on the film through the incident light path, the intensity of the beam is I0; the incident light is incident on the surface of the film at an incident angle α, α=β>0, part of the light is reflected into the environment, and the other part of the light is refracted by the film and the substrate and incident on the reflecting surface, and then is reflected vertically by the reflecting surface and returns along the original path, and finally refracted from the upper surface of the film into the environment; or, the light emitted by the light source is not collimated to form a divergent beam that is incident on the film through the incident light path, the intensity of the beam is I0, and the divergence angle is γ=arc sin(NA), where NA is the numerical aperture of the optical fiber or lens in the outgoing light path; the principal ray of the divergent light beam, i.e., the central ray of the divergent light beam, is incident on the surface of the film at an incident angle α, where α>arcsin(NA) and α≥β>0. A portion of the light is reflected into the environment. The portion of the divergent light beam that is perpendicular to the reflecting surface, i.e., the light with an angle (α-β) with the principal ray, is refracted by the film and substrate and perpendicularly incident on the reflecting surface. It is then perpendicularly reflected by the reflecting surface and returns along the original path, and finally refracted from the upper surface of the film into the environment;

[0039] The light beam refracted from the upper surface of the film-reflecting surface system to the environment is received by a detector or a spectrometer through an outgoing optical path to obtain the light intensity of the light beam refracted from the upper surface of the film-reflecting surface system to the environment; the reflectivity of the film-reflecting surface system is obtained according to the light intensity; the light intensity transmittance T of the substrate is known. s and the light intensity reflectivity R of the reflecting surface m , and the reflectivity of the film-reflecting surface system, the light intensity transmittance of the film is obtained.

[0040] The curved reflective surface is a surface that is a tangent plane of the incident light perpendicular to the incident point. The curved reflective surface may be a spherical reflective surface, a conical reflective surface or other curved reflective surfaces.

[0041] Furthermore, the present invention's real-time in-situ spectral integrated measurement device based on single-side single reflection is integrated with a film-forming device to achieve real-time in-situ monitoring of the transmission spectrum during the thin film growth process. The film-forming device is a spin coater, a heating annealing table, or a coating machine.

[0042] Advantages of the present invention:

[0043] The present invention directly calculates the light intensity transmittance of the film by measuring the reflectivity of the film-reflecting surface system on a single side, without knowing the dielectric constant of the film material and the thickness of the film in advance; measuring the film transmittance at different wavelengths can obtain the transmittance spectrum of the film; this process only measures the reflected light intensity of the film-reflecting surface system once, and does not involve the amplitude superposition or interference of light; more importantly, the incident light and the light returned by the reflecting surface are collinear and on the same side of the sample, which makes the entire measurement system very compact and easy to integrate; by further increasing the incident angle, the light reflected from the film surface and the light reflected from the reflecting surface will not be measured by the system, so the measuring device can directly measure the fluorescence spectrum of the film under the excitation of continuous light or monochromatic light. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] Figure 1 Schematic diagram of the transmittance principle of the real-time in-situ spectral integrated measurement method based on single-sided single reflection of the present invention, wherein: (a) is a schematic diagram of a plane reflecting surface, where the light beam is perpendicular to the horizontal plane; (b) is a schematic diagram of a plane reflecting surface, where the light beam is inclined to the horizontal plane; (c) is a schematic diagram of a spherical reflecting surface, where the light beam is perpendicular to the horizontal plane; (d) is a schematic diagram of a spherical reflecting surface, where the light beam is inclined to the horizontal plane; (e) is a schematic diagram of a conical reflecting surface, where the light beam is inclined to the horizontal plane; (f) is a schematic diagram of other curved reflecting surfaces, where the light beam is inclined to the horizontal plane;

[0045] Figure 2 Schematic diagrams of the real-time in-situ spectral integrated measurement device based on single-side single reflection of the present invention, wherein (a) is a schematic diagram of the optical fiber transmission system - vertical light incidence; (b) is a schematic diagram of the optical fiber transmission system - oblique light incidence; (c) is a schematic diagram of the free-space transmission system;

[0046] Figure 3 Graphs showing the reflection and transmission spectra of a perovskite film obtained according to an embodiment of the real-time in-situ spectral integrated measurement method based on single-side single reflection of the present invention, wherein (a) shows the result when the film thickness is h = 240 nm; (b) shows the result when the film thickness is h = 190 nm; and (c) shows the result when the film thickness is h = 130 nm.

[0047] Figure 4 Schematic diagrams of an experimental device for the integrated application of the real-time in-situ spectral integrated measurement method based on single-side single reflection of the present invention and other film-making equipment, (a) is a schematic diagram of the integration with a spin coater; (b) is a schematic diagram of the integration with a heated annealing station;

[0048] Figure 5 The graphs show the real-time in-situ measurement of the time evolution of the transmittance spectrum of a perovskite film during annealing using the real-time in-situ spectral integrated measurement method based on single-side single reflection of the present invention. (a) to (c) show the time evolution of the transmittance spectrum of perovskite films prepared with different concentrations of ink during annealing for 0 to 20 seconds and 0 to 600 seconds, respectively.

[0049] Figure 6 It is a schematic diagram of the integrated application of the real-time in-situ spectral integration device based on single-side single reflection and the film-making equipment of the present invention. DETAILED DESCRIPTION

[0050] The present invention will be further described below through specific embodiments in conjunction with the accompanying drawings.

[0051] The real-time in-situ spectral integrated measurement device based on single-side single reflection of this embodiment includes: a substrate, a reflective surface, a sample stage, a light source, an incident light path, an outgoing light path, a spectrometer, and a computer;

[0052] The film to be measured is placed on a transparent substrate, with the environment above the film; the transmittance of the substrate T s ≥5%;

[0053] like Figure 1 As shown, the substrate is placed on the reflective surface to form a film-reflective surface system, and the reflective surface is set on the sample stage; the reflective surface is a flat reflective surface or a curved reflective surface; when the reflective surface is a flat reflective surface, the angle between the film surface to be measured and the plane where the reflective surface is located is the tilt angle β; when the reflective surface is a curved reflective surface, the angle between the film surface to be measured and the tangent plane of the reflection point is the tilt angle β, β>0. Figure 1 In the figure, (a) is a plane reflecting surface, the light beam is perpendicular to the horizontal plane; (b) is a plane reflecting surface, the light beam is inclined to the horizontal plane; (c) is a spherical reflecting surface, the light beam is perpendicular to the horizontal plane; (d) is a spherical reflecting surface, the light beam is inclined to the horizontal plane; (e) is a conical reflecting surface, the light beam is inclined to the horizontal plane; (f) is other curved reflecting surfaces of the tangent plane perpendicular to the incident point, the light beam is inclined to the horizontal plane.

[0054] like Figure 2As shown, an incident light path and an outgoing light path are provided on the film; a light source is coupled to the incident light path, and the end of the outgoing light path is coupled to a detector or spectrometer, which is connected to a computer. The incident and outgoing light paths utilize either a fiber optic transmission system or a free-space transmission system. When utilizing a fiber optic transmission system, the incident light path utilizes an input fiber, and the outgoing light path utilizes an outgoing fiber. When utilizing a free-space transmission system, the incident light path utilizes a first lens, and the outgoing light path utilizes a second lens. In the incident light path, the incident light is collimated by the first lens and then incident on the top surface of the film through a beam splitter. In the outgoing light path, the outgoing light passes through the beam splitter, is collected by the second lens, and is coupled to the spectrometer. The beam splitter utilizes a beam splitter prism or a beam splitter. Figure 2 In the figure, (a) is the optical fiber transmission system - light vertical incidence; (b) is the optical fiber transmission system - light oblique incidence; (c) is the free space transmission system. Only three measurement devices are shown here, the optical fiber transmission system and the free space transmission system. Figure 1 All cases in can be integrated separately.

[0055] When the light emitted by the light source is collimated and becomes a parallel beam that is incident on the film through the incident light path, the intensity of the beam is I0; the incident light is incident on the surface of the film at an incident angle α, α=β>0, part of the light is reflected into the environment, and the other part of the light is refracted by the film and the substrate and incident on the reflecting surface, and then is reflected vertically by the reflecting surface and returns along the original path, and finally refracted from the upper surface of the film into the environment; or, the light emitted by the light source is not collimated to form a divergent beam that is incident on the film through the incident light path, the intensity of the beam is I0, and the divergence angle is γ=arc sin(NA), NA is the numerical aperture of the optical fiber or lens in the output light path; the principal ray of the divergent light beam, that is, the light in the middle of the divergent light beam, is incident on the surface of the film at an incident angle α, α>arcsin(NA) and α≥β>0, and a part of the light is reflected into the environment. The part of the divergent light beam that is perpendicular to the reflecting surface, that is, the light with an angle of (α-β) with the principal ray, is refracted by the film and the substrate and vertically incident on the reflecting surface, and then is vertically reflected by the reflecting surface and returns along the original path, and finally refracted from the upper surface of the film into the environment.

[0056] The light beam refracted from the upper surface of the film-reflecting surface system into the environment is received by the spectrometer through the outgoing optical path, and the light intensity I of the light beam refracted from the upper surface of the film-reflecting surface system into the environment is measured. R ,satisfy:

[0057] I R =I0×T×T s ×R m ×T s ×T

[0058] Where T is the light transmittance of the film, T s is the light transmittance of the substrate, Rm is the light intensity reflectivity of the reflective surface; according to the light intensity formula, the reflectivity R of the film-reflective surface system is obtained as:

[0059]

[0060] When the light transmittance of the substrate T s and the light intensity reflectivity R of the reflecting surface m When the above reflectivity formula is known, the light intensity transmittance T of the film can be further obtained:

[0061]

[0062] The light transmittance T of the film can be directly calculated by measuring the reflectivity R of the film-reflecting surface system, without having to know the complex refractive index of the film material and the film thickness in advance. This method is suitable for real-time in-situ measurement during the film growth process.

[0063] Use Figure 2 The experiment was conducted using the optical fiber transmission system shown in (a). The numerical aperture of the optical fiber used in the experiment was NA = 0.22 ± 0.02, corresponding to a divergence angle of 12.5°. The input and output optical fibers have a common port, which is fixed by a five-axis optical fiber holder. The five-axis optical fiber holder adjusts the three-dimensional position of the optical fiber on the film and adjusts the pitch of the optical fiber so that the optical fiber is perpendicular to the surface of the film. The sample stage used in the experiment is Figure 1 (a) shows a plane reflective surface and the light beam is perpendicular to the horizontal plane. The sample stage is made of copper. The tilt angle α on the upper surface of the sample stage is 13.1°, which is greater than the optical fiber divergence angle of 12.5°. Therefore, the optical fiber probe only collects the light reflected from the plane reflective surface, but does not collect the reflected light from the upper and lower surfaces of the film. The reflection spectrum and transmission spectrum of the perovskite MAPbI3 film-reflective surface system were measured in the experiment. The substrate under the film is made of glass, as shown in Figure 2. Figure 3 shown. Figure 3In (a), the thickness of the MAPbI3 film is h = 240 nm. The dashed line is the reflectance spectrum of the MAPbI3 film-reflecting surface system measured using the device, the solid line is the calculated transmittance spectrum of the MAPbI3 film, and the dashed line is the transmittance spectrum of a MAPbI3 film with a thickness of h = 240 nm measured using a spectrophotometer. The dashed line's reflectance spectrum of the MAPbI3 film-reflecting surface system shows that in the long-wavelength range (λ > 780 nm), the perovskite film has minimal absorption, resulting in minimal energy loss of light reaching the reflective surface through the film and substrate, resulting in strong light reflected by the copper reflective surface (reflectance of the film-reflecting surface system ~0.6). In the short-wavelength range (λ < 760 nm), the perovskite film has strong absorption, resulting in significant attenuation of light reaching the reflective surface through the film and substrate, resulting in a minimal effect of the copper reflective surface. Therefore, in the short-wavelength range, the reflectance of the film-reflecting surface system rapidly approaches zero as the wavelength decreases.

[0064] The reflection spectrum of the film-reflecting surface system measured by the single-side single reflection method ( Figure 3 Based on the dashed line in (a), the light intensity transmittance formula can be used to directly calculate the film transmittance spectrum, such as Figure 3 (a) is shown by the solid line. The film transmission spectrum measured by the transmission spectrophotometer is shown as Figure 3 As shown by the dashed line in (a). A comparison shows that the film transmission spectrum obtained using the method of the present invention agrees well with that measured by a transmission spectrophotometer. In this example, the similarity between the transmission spectra obtained using the spectral angle matching method (SAM) was calculated to be 2.67°. Based on the obtained film transmission spectrum, the absorbance of the film can be calculated using log(1 / T).

[0065] In order to further verify the accuracy of the test of the present invention, MAPbI3 perovskite films with thicknesses of h = 190 nm and h = 130 nm were also measured. The experimental results are shown in Figure 2. Figure 3 By comparing the transmission spectrum (solid line) measured by the single-side single reflection method with the transmission spectrum (dotted line) measured by the transmission spectrophotometer, the transmission spectra of films of different thicknesses measured by these two methods are basically consistent, with spectral similarities of 1.82° and 1.39° respectively. Figure 1 Similar results can be obtained for other reflective surfaces. Measuring a film's transmittance spectrum using a single-reflection setup requires only a single acquisition of the reflectance of the film-reflective surface system, with an acquisition time of less than 200 milliseconds. Measuring a film's transmittance spectrum using a transmission-type spectrophotometer requires rotating the grating, and the acquisition time is approximately 5 minutes. Therefore, using a single-sided single-reflection setup allows for faster and more accurate film transmittance measurements.

[0066] The present invention is integrated with film-making equipment such as a spin coater, a heating annealing table or a coater:

[0067] Many thin films are prepared using spin coaters and coating machines. The device proposed in this invention can be directly integrated with the spin coater without any modification to the spin coater. Figure 4 As shown in (a), it is only necessary to fix the sample stage with a rotationally symmetric reflective surface on the turntable of the spin coater. Heating annealing is a common method to improve the quality and performance of thin films, and is widely used in the preparation of various thin film materials, especially in the fields of semiconductors, optoelectronic materials, etc. The heating annealing process can reduce defects in the film, thereby improving the crystallinity of the film and enhancing the electronic and optical properties of the film. The present invention proposes to directly integrate the single-sided single reflection device with the heating annealing stage, as shown in the schematic diagram. Figure 4 (b) As shown. Similarly, the integration process does not require any modification to the heating annealing table. Just place the sample table with the reflective surface on the heating table. The single-sided single reflection device can also be integrated with the coating machine. It should be pointed out that only two integration examples are shown here, the spin coater and the heating annealing table and Figure 1 The other curved surfaces in the device can be integrated separately. Integrating the device of the present invention directly with film-making equipment such as a spin coater, a heating annealing table or a coating machine can achieve real-time in-situ spectral measurement of the thin film growth process.

[0068] The following is an experiment in which the device of the present invention is directly integrated with a heating annealing table. The sample table with a reflective surface is fixed on the heating annealing table. Figure 2 (b) is made of copper. Since copper has a high thermal conductivity of 413W / (mK), the results of annealing the film on a copper sample table and directly placing the film on the annealing table are consistent.

[0069] First, set the heating annealing table to the required experimental temperature (100°C) in advance. After the heating annealing table is heated, use a thermocouple thermometer to measure the temperature of the sample table. Its temperature is 100°C, which is the same as the temperature of the heating annealing table, thanks to the excellent thermal conductivity of copper. In the experiment, a MAPbI3 perovskite ink with a concentration of 1.25M was spin-coated on a glass substrate treated with oxygen plasma using a spin coater. After the spin coater is completed, the sample is immediately transferred to a low-pressure auxiliary device to wait for the MAPbI3 perovskite crystal nucleus to be fully precipitated. Then, place the thin film sample as follows Figure 4 (a) is mounted on a copper sample stage as shown.

[0070] Figure 5In the figure, (a) shows the transmittance spectrum changes of the film prepared with 1.25M perovskite ink at annealing times of 0 to 20s (left) and 0 to 600s (right); (b) shows the transmittance spectrum changes of the film prepared with 1M perovskite ink at annealing times of 0 to 20s (left) and 0 to 600s (right); (c) shows the transmittance spectrum changes of the film prepared with 0.75M perovskite ink at annealing times of 0 to 20s (left) and 0 to 600s (right).

[0071] According to the measurement method of the present invention, the reflection spectrum R(λ) of the film-reflecting surface system can be continuously collected during the film annealing process, and then the relationship between the transmission spectrum T(λ) of the film during the annealing process and time can be directly calculated, such as Figure 5 As shown in (a). During the annealing process of MAPbI3 film from 0 to 4 s, the band edge of the transmission spectrum of the film obviously red-shifted (from 650nm to 750nm). This phenomenon indicates that during this period, the perovskite crystal nuclei grew to form a thin film; during the period of 4 to 9 s, the band edge of the film transmission spectrum slowly red-shifted from 750nm to 760nm (the characteristic transmission band edge of MAPbI3), indicating that during this period, the organic solvent in the film continuously evaporated under the action of heating and annealing, and the main component of the film was converted into MAPbI3 perovskite; within the time range of 10 to 600 s (after the heating and annealing was completed), the band edge of the film transmission spectrum remained unchanged (760nm).

[0072] This integrated device was used to measure the transmittance spectra of thin films prepared with perovskite inks at concentrations of 1M and 0.75M during heating and annealing. The measurement results are shown in Figure 5 As shown in (b) and (c). For the film prepared with the perovskite ink with a concentration of 1M, the band edge of the film transmittance spectrum slowly red-shifts from 650nm to 760nm in the time of 0-8s; and the band edge of the film transmittance spectrum remains unchanged (760nm) in the time range of 9-600s (heating annealing is completed). For the film prepared with the perovskite ink with a concentration of 0.75M, the band edge of the film transmittance spectrum slowly red-shifts to 760nm in the time of 0-8s; and the band edge of the film transmittance spectrum remains unchanged (760nm) in the time range of 9-600s (heating annealing is completed). The band edge of the transmittance spectrum of the film prepared with the perovskite ink with a concentration of 1.25M ( Figure 5 a) It is not until annealing for 10s that the formation of the band edge of the transmission spectrum is stable. The speed of formation of the band edge of the transmission spectrum is slower than that of the film prepared by the perovskite ink with a concentration of 1M and 0.75M. This is because the increase in the concentration of the perovskite ink increases the thickness of the film. In addition, by Figure 5It can be seen intuitively that after the transmission band edge of the perovskite films of different thicknesses is formed, their transmission spectra remain essentially unchanged until the entire heating and annealing process is completed. The above experimental results fully demonstrate the successful integration of the single-sided single-reflection device proposed in this invention with the heating and annealing stage.

[0073] The present invention proposes a real-time in-situ spectral integrated measurement method based on single-sided single reflection, and uses this method to measure the transmittance spectra of perovskite films of different thicknesses. In the single-sided single reflection method for measuring the transmittance of thin films, in order to avoid collecting reflected light from the upper and lower surfaces of the film, the incident light is allowed to be incident obliquely on the film surface; in order to effectively utilize the transmitted light, the present invention proposes to set a flat or curved reflective surface under the substrate so that the transmitted light is perpendicularly incident on the reflective surface and then returns along the original path to be collected by an optical fiber or lens. This single-sided single reflection measurement method does not require the complex refractive index of the film material and the thickness of the film to be known in advance, and is suitable for real-time in-situ measurement during the film growth process. In addition, because the incident light and the light returning from the original path of the reflective surface are collinear and both on the same side of the sample, the entire measurement system becomes very compact and easy to integrate. Experimental results show that the transmittance spectra of perovskite films of different thicknesses measured by the measurement method proposed by the present invention are in good agreement with the results measured by a transmission spectrophotometer, and the spectral similarity obtained by the two measurement methods is better than 2.7°. Compared with traditional transmission methods (such as spectrophotometers), the single reflection method has the advantages of small size, easy integration, and fast measurement speed.

[0074] Furthermore, the present invention integrates the single-side single reflection measurement device with the film-making equipment, such as Figure 6 As shown, the real-time in-situ monitoring of the transmission spectrum during the thin film growth process was successfully achieved. This integrated device enables real-time in-situ measurement of the thin film growth process, providing an effective and feasible solution for studying the dynamics of the film-forming process and understanding and optimizing device functions.

[0075] Finally, it should be noted that the purpose of disclosing the embodiments is to facilitate a further understanding of the present invention. However, those skilled in the art will appreciate that various substitutions and modifications are possible without departing from the spirit and scope of the present invention and the appended claims. Therefore, the present invention should not be limited to the contents disclosed in the embodiments; the scope of protection claimed by the present invention shall be determined by the scope defined in the claims.

Claims

1. A real-time in-situ spectral integrated measurement method based on single-side single reflection, characterized in that: The measuring method comprises the following steps: 1) Build a real-time in-situ spectral integrated measurement device: The film to be measured is placed on a transparent substrate with the environment above the film; the transmittance of the substrate T s ≥5%; The substrate is placed on a reflective surface to form a film-reflective surface system, and the reflective surface is placed on a sample stage; the reflective surface is a flat reflective surface or a curved reflective surface; when the reflective surface is a flat reflective surface, the angle between the film surface to be measured and the plane where the reflective surface is located is the tilt angle β; when the reflective surface is a curved reflective surface, the angle between the film surface to be measured and the tangent plane of the reflection point is the tilt angle β, β>0; An incident light path and an outgoing light path are arranged above the film; a light source is coupled to the incident light path, an end of the outgoing light path is coupled to a detector or a spectrometer, and the detector or the spectrometer is connected to a computer; 2) Beam propagation: Parallel beam: The light emitted by the light source is collimated and becomes a parallel beam that is incident on the film through the incident light path. The light intensity of the beam is I0. The incident light is incident on the surface of the film at an incident angle α, α=β>0. Part of the light is reflected into the environment, and the other part of the light is refracted by the film and the substrate and then perpendicularly incident on the reflecting surface. It is then perpendicularly reflected by the reflecting surface and returns along the original path. Finally, it is refracted from the upper surface of the film into the environment. Divergent beam: The light emitted by the light source is not collimated to form a divergent beam that is incident on the film through the incident light path. The light intensity of the beam is I0, and the divergence angle is γ = arcsin (NA). NA is the numerical aperture of the optical fiber or lens in the output light path. The central light of the divergent beam, i.e., the principal light, is incident on the surface of the film at an incident angle α, where α>arcsin (NA) and α≥β>0. A portion of the light is reflected into the environment. The portion of the divergent beam that is perpendicular to the reflecting surface, i.e., the light with an angle of (α-β) with the principal light, is refracted by the film and substrate and vertically incident on the reflecting surface. It is then vertically reflected by the reflecting surface and returns along the original path. Finally, it is refracted from the upper surface of the film into the environment. 3) Beam reception: The light beam refracted from the upper surface of the film-reflecting surface system into the environment is received by a detector or spectrometer via the outgoing optical path, and the light intensity I of the light beam refracted from the upper surface of the film-reflecting surface system into the environment is obtained. R ; 4) Light intensity formula: The intensity I of the light beam refracted from the upper surface of the film-reflector system to the environment R satisfy: I R =I0×T×T s ×R m ×T s ×T Where T is the light transmittance of the film, T s is the light transmittance of the substrate, R m is the light intensity reflectivity of the reflecting surface; 5) Reflectivity formula: According to the light intensity formula in step 4), the reflectivity R of the film-reflecting surface system is obtained as: 6) Obtain transmittance: According to the known light intensity transmittance T of the substrate s and the light intensity reflectivity R of the reflecting surface m , using the reflectivity formula in step 5), the light intensity transmittance T of the film is further obtained: Therefore, the light intensity transmittance T of the film can be directly calculated by measuring the reflectivity R of the film-reflecting surface system without knowing the complex refractive index of the film material and the thickness of the film in advance. This method is suitable for real-time in-situ measurement during the film growth process.

2. The measuring method according to claim 1, wherein In step 1), a multi-wavelength light source is used as the light source to directly measure the thin film transmittance spectrum; or a monochromatic light source is used to measure the thin film transmittance at one wavelength.

3. The measuring method according to claim 1, wherein: In step 1), the reflective surface adopts a reflective mirror or a reflective film.

4. The measuring method according to claim 1, wherein In step 1), the sample stage adopts a bracket, a support frame, a support shell or a block support.

5. The measuring method according to claim 1, wherein: The incident light path and the outgoing light path adopt an optical fiber transmission system or a free space transmission system; when the optical fiber transmission system is adopted, the incident light path adopts an incident optical fiber, and the outgoing light path adopts an outgoing optical fiber; When a free-space transmission system is used, the first lens is used in the incident light path and the second lens is used in the outgoing light path. In the incident light path, the incident light is collimated by the first lens and then incident on the upper surface of the film through the spectrometer. In the outgoing light path, the outgoing light is collected by the second lens after passing through the spectrometer and coupled to the detector or spectrometer.

6. The measuring method according to claim 1, wherein: The real-time in-situ spectral integrated measurement device is integrated with the film-making equipment to realize real-time in-situ monitoring of the transmission spectrum of the thin film growth process.

7. A real-time in-situ spectral integrated measurement device based on single-side single reflection, characterized in that: The real-time in-situ spectral integrated measurement device comprises: a substrate, a reflective surface, a sample stage, a light source, an incident light path, an outgoing light path, a detector or a spectrometer, and a computer; The film to be measured is placed on a transparent substrate, with the environment above the film; the transmittance of the substrate T s ≥5%; The substrate is placed on a reflective surface to form a film-reflective surface system, and the reflective surface is placed on a sample stage; the reflective surface is a flat reflective surface or a curved reflective surface; when the reflective surface is a flat reflective surface, the angle between the surface of the film to be measured and the plane on which the reflective surface is located is the tilt angle β; when the reflective surface is a curved reflective surface, the angle between the surface of the film to be measured and the tangent plane of the reflection point is the tilt angle β, β>0; An incident light path and an outgoing light path are arranged on the film; a light source is coupled to the incident light path, an end of the outgoing light path is coupled to a detector or a spectrometer, and the detector or the spectrometer is connected to a computer; When the light emitted by the light source is collimated and becomes a parallel beam, it is incident on the film through the incident light path; the incident light is incident on the surface of the film at an incident angle α, α=β>0, part of the light is reflected into the environment, and the other part of the light is refracted by the film and the substrate and is incident on the reflecting surface, then is vertically reflected by the reflecting surface and returns along the original path, and finally is refracted from the upper surface of the film into the environment; or, the light emitted by the light source is not collimated to form a divergent beam, which is incident on the film through the incident light path, and the divergence angle of the light beam is γ=arcsin(NA), NA is the numerical aperture of the optical fiber or lens in the output light path; the principal ray of the divergent beam, that is, the middle ray of the divergent beam, is incident on the surface of the film at an incident angle α, α>arcsin(NA) and α≥β>0, part of the light is reflected into the environment, and the part of the divergent beam perpendicular to the reflecting surface, that is, the light with an angle of (α-β) with the principal ray, is refracted by the film and the substrate and is vertically incident on the reflecting surface, then is vertically reflected by the reflecting surface and returns along the original path, and finally is refracted from the upper surface of the film into the environment; A light beam refracted from the upper surface of the film-reflecting surface system into the environment is received by a detector or a spectrometer via an outgoing light route to obtain the light intensity of the light beam refracted from the upper surface of the film-reflecting surface system into the environment; the reflectivity of the film-reflecting surface system is obtained based on the light intensity; the light intensity transmittance of the film is obtained based on the known light intensity transmittance of the substrate and the light intensity reflectivity of the reflective surface, as well as the reflectivity of the film-reflecting surface system.

8. The real-time in-situ spectral integrated measurement device according to claim 7, characterized in that: The real-time in-situ spectral integrated measurement device is integrated with the film-making equipment to achieve real-time in-situ monitoring of the transmission spectrum during the thin film growth process.

9. The real-time in-situ spectral integrated measurement device according to claim 7, characterized in that: The reflective surface is a reflective mirror or a reflective film.

10. The real-time in-situ spectral integrated measurement device according to claim 7, characterized in that: The incident light path and the outgoing light path adopt an optical fiber transmission system or a free space transmission system; when the optical fiber transmission system is adopted, the incident light path adopts an incident optical fiber, and the outgoing light path adopts an outgoing optical fiber; When a free-space transmission system is used, the first lens is used in the incident light path and the second lens is used in the outgoing light path. In the incident light path, the incident light is collimated by the first lens and then incident on the upper surface of the film through the spectrometer. In the outgoing light path, the outgoing light is collected by the second lens after passing through the spectrometer and coupled to the detector or spectrometer.

Images