Application of ac-driven backlight in characterization of surface morphology of thin film sample and characterization system of surface morphology of thin film

Abstract

The application discloses application of an alternating-current driving type backlight source in characterization of a surface morphology of a thin film sample. A characterization system of a thin film surface morphology is also disclosed, which comprises an input area component, a test area component and an output area component, and a corresponding characterization method of the thin film surface morphology. The application can realize the function of characterizing and testing the surface morphology of the thin film sample without probe contact and current injection, and can realize the function of constructing a three-dimensional image of the surface of the thin film through horizontal and vertical scanning of the probe. The device of the application can be used for efficient measurement, and the alternating electric field driving nano LED array can achieve the effect of zero damage to the surface of the sample.

Description

Technical Field

[0001] This invention relates to the application of an AC-driven backlight in characterizing the surface morphology of thin film samples, a characterization system for thin film surface morphology, and a corresponding characterization method for thin film surface morphology. Background Technology

[0002] Optoelectronic devices have received widespread attention in research over the past few decades, and have been widely applied in many fields, such as communication storage, display lighting, food safety, and new displays. GaN-based optoelectronic devices have high luminous efficiency, energy-saving and environmentally friendly advantages, small size, and long lifespan, making them highly promising. GaN materials have been extensively studied and used in optoelectronic devices such as light-emitting diodes (LEDs) and lasers (LDs). Although research on GaN-based LEDs is relatively in-depth, traditional LEDs generally operate under direct current (DC), which has limitations: as pixel size decreases, it becomes difficult to integrate metal electrodes onto LED devices or form good ohmic contacts. A novel LED driving technology—alternating current (AC) electric field driving technology—has emerged and received widespread attention in areas where DC-driven nano-LEDs are limited.

[0003] As a potential alternative to DC-driven LEDs, AC electric field driving technology for LEDs has been extensively studied due to its unique advantages and potential application value. Compared to DC-driven light-emitting devices, AC driving has significant advantages in the field of nanoscale light-emitting devices. For example, by changing the direction and frequency of the applied electric field, charge accumulation in the light-emitting device can be effectively prevented, thereby improving luminous efficiency; in AC-driven devices, the insulating dielectric layer can avoid non-radiative recombination of injected charge carriers, thus reducing heat generation. GaN-based LEDs driven by AC electric fields can achieve contactless driving of nanoscale display pixels, and are expected to replace DC driving as a new driving mode for ultra-high resolution displays. Therefore, exploring and realizing AC-driven nano-LED structures with high gain is an urgent problem to be solved. Summary of the Invention

[0004] This invention discloses the application of AC-driven backlight in characterizing the surface morphology of thin film samples.

[0005] According to the above application, the AC-driven backlight can generate an optical signal related to the film thickness after being excited by an alternating electric field.

[0006] According to the above applications, the AC-driven backlight is a nano-LED array or a quantum dot film, or an organic light-emitting film.

[0007] Preferably, the thin film sample is neither a magnetic thin film nor a metallic thin film.

[0008] The present invention also discloses a characterization system for thin film surface morphology, including an input region component, a test region component, and an output region component;

[0009] The input region assembly is used to apply an alternating electric field over the thin film sample to be tested, and the input region assembly includes at least:

[0010] AC power supply, used to output AC electric field signal to drive the backlight to emit light;

[0011] A cantilever is used to conduct AC signals between the power supply and the probe, and to control the movement of the probe;

[0012] A probe is used to maintain an alternating electric field above the thin film sample to be tested.

[0013] The test area assembly is used to place the thin film sample to be tested and to emit light signals. The test area assembly includes at least:

[0014] AC-driven backlight with dielectric substrate: used to generate an optical signal related to the thickness of the thin film sample under test by being excited by an alternating electric field, with the thin film sample placed on the dielectric substrate;

[0015] ITO, as a transparent conductive layer, needs to be grounded;

[0016] The output area component is used to receive and feed back test data and to draw a three-dimensional image. The output area component includes at least:

[0017] A photodetector is used to receive light signals generated by a backlight and convert them into electrical signals.

[0018] The scanning controller is used to control the cantilever to move the probe horizontally at a constant height above the thin film sample to be tested, and to record the coordinate information of each sampling point corresponding to the probe.

[0019] The image generation module is used to summarize the coordinate positions and peak voltages of each sampling point and describe a three-dimensional image of the relative height of the thin film surface.

[0020] Preferably, the backlight source is a nano-LED array or a quantum dot film, or an organic light-emitting film.

[0021] Preferably, the dielectric substrate is sapphire, silicon, or quartz.

[0022] Preferably, the AC power supply is a sinusoidal AC power supply with a frequency of 10-100kHz.

[0023] This invention also discloses a method for characterizing the surface morphology of thin films, implemented based on the aforementioned system for characterizing the surface morphology of thin films, comprising the following steps:

[0024] (1) Place the thin film sample to be tested on the dielectric substrate;

[0025] (2) An AC power supply excites an AC signal, which is transmitted to the probe through the cantilever and releases an alternating electric field above the thin film sample to be tested. The scanning controller controls the probe to always be at a constant height above the thin film sample to be tested and performs horizontal and vertical shift scanning.

[0026] (3) An alternating electric field excites the backlight to generate an optical signal. The photodetector receives the optical signal generated by the backlight and converts it into an electrical signal. The coordinate information of each sampling point and the peak voltage of the corresponding photoelectric signal are output to the image generation module by the scanning controller and the photodetector, respectively, so as to draw a three-dimensional image of the relative height of the thin film surface morphology.

[0027] The working principle of this invention is as follows: A probe releases an alternating electric field above the thin film. The thin film and the substrate together form a capacitor. Under the action of the capacitor, the alternating electric field excites a backlight to generate an optical signal. A photodetector measures the optical signal and converts it into an electrical signal. The relative height of the thin film affects the size of the capacitor, so that the electrical signal corresponds to the relative height of the thin film. Therefore, a three-dimensional image of the relative height of the thin film surface morphology can be drawn based on the position of the probe and the corresponding electrical signal.

[0028] The beneficial effects of this invention are as follows:

[0029] (1) This invention has a wide range of applications and does not have strict requirements on the surface roughness of the sample. It can be used to test solid or colloidal materials, including insulators.

[0030] (2) The sample is non-destructive. The scanning probe does not need to contact the sample. There is no high-energy electron beam bombarding the sample, which will not cause wear and damage to the sample and probe.

[0031] (3) The test is convenient and does not require irreversible special treatment of the sample;

[0032] (4) No vacuum is required; it can work at room temperature and pressure.

[0033] (5) Three-dimensional imaging can provide information on the height direction of the sample.

[0034] In summary, this invention enables the characterization and testing of the surface morphology of thin film samples without probe contact or current injection, and it can construct a three-dimensional image of the thin film surface through transverse and longitudinal scanning of the probe. The device of this invention allows for efficient measurements, and the alternating electric field driving the nano-LED array achieves zero damage to the sample surface. Attached Figure Description

[0035] Figure 1 This is a structural block diagram of the thin film surface morphology characterization system in an embodiment of the present invention;

[0036] Figure 2 This is a schematic diagram of the composition of the backlight (nanoLED array) in an embodiment of the present invention;

[0037] Figure 3 This is an equivalent circuit diagram of the thin film surface morphology characterization system in an embodiment of the present invention;

[0038] [Explanation of symbols for key components in this invention]

[0039] 1-Input area components; 11-AC power supply;

[0040] 12-Cantilever; 13-Probe;

[0041] 2-Test area components; 21-Thin film sample;

[0042] 22- Substrate of the backlight; 23- Light-emitting components of the backlight (taking a nano-LED array as an example);

[0043] 24-ITO; 3-Output area components;

[0044] 31-Photodetector; 32-Scan controller;

[0045] 33-Image generation module.

[0046] The specific embodiments of the present invention will be further described below with reference to the accompanying drawings. Detailed Implementation

[0047] The present invention will be further described below with reference to the embodiments, but the description of the embodiments does not limit the scope of protection of the present invention in any way.

[0048] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used herein in the specification of this invention is for the purpose of describing particular embodiments only and is not intended to limit the invention. Furthermore, while this document provides examples of parameters containing specific values, it should be understood that the parameters need not be exactly equal to the corresponding values, but can approximate the corresponding values ​​within acceptable error tolerances or design constraints. Directional terms mentioned in the embodiments, such as “up,” “down,” “front,” “back,” “left,” “right,” etc., are only for reference to the accompanying drawings. Therefore, the directional terms used are for illustrative purposes and not for limiting the scope of protection of this invention.

[0049] Unless otherwise specified, all substances or instruments used in the following examples can be obtained from conventional commercial sources.

[0050] In embodiments of the present invention, a characterization system for thin film surface morphology is provided. For example... Figure 1 As shown, the device includes an input region component 1, a test region component 2, and an output region component 3. The input region component 1 is an alternating electric field excitation device, including an AC power supply 11, a cantilever 12, and a probe 13. The test region component 2 is a sample carrier and test signal generation device, including a thin film sample 21, a sapphire substrate 22, a backlight (nano-LED array), and ITO 24. The output region component 3 is a signal conversion and image acquisition device, including a photodetector 31, a scanning controller 32, and an image generation module 33.

[0051] The following sections will provide a detailed description of each component of the thin film surface morphology characterization system in this embodiment.

[0052] The AC power supply 11 consists of an AC waveform generator (Tektronix AFG2021) and a lock-in amplifier (PINTECHHA-520). The output AC signal is transmitted to the micro probe 13 via the cantilever 12, releasing an alternating electric field that can excite the backlight nano-LED array to emit light. The electric field frequency is controlled between 10-100kHz.

[0053] The cantilever 12 is connected to and fixed to the probe 13, and is suspended at a constant height on the surface of the thin film sample 21. It can be scanned point by point by the scanning controller 32.

[0054] The backlight nano-LED array is an AC-driven nano-LED array fabricated from a commercially available InGaN / GaN-based LED wafer 23 grown on a 450μm thick sapphire substrate 22. Its specific structure is as follows: Figure 2 As shown, a nano-LED array with a diameter of 100nm, a height of 1μm, and a period of 200nm is formed through semiconductor microfabrication technology.

[0055] The thin film sample 21 is placed on top of an inverted backlight nano-LED array and bonded to a sapphire substrate 22, while the transparent conductive layer ITO 24 is grounded. This system can be modeled as follows: Figure 3 The equivalent circuit shown has the thin film sample 21 and sapphire substrate 22 equivalent to capacitor C. 衬底 .

[0056] The photodetector 31 is an APD avalanche photodetector used to receive the light signal generated by the backlight nano-LED array 23 and convert it into an electrical signal. It is suitable for visible light in the range of 380nm-780nm and requires a 12V operating voltage from a power supply.

[0057] The function of the scanning controller 32 is to control the horizontal movement of the cantilever 12 and the probe 13, perform horizontal and vertical point-by-point scanning according to the preset step size and interval, and feed back the coordinates of each point to the image generation module 33.

[0058] The image generation module 33 combines the sampling point coordinate information (x, y) output by the scanning controller 32 with the peak voltage V of the electrical signal at that point output by the photodetector 31 to form a three-dimensional vector coordinate (x, y, V), thereby constructing a three-dimensional image within the scanning range.

[0059] The testing process for the thin film surface morphology characterization system in this embodiment is as follows:

[0060] AC power supply 11 outputs an AC signal, which is conducted through cantilever 12 and probe 13 to excite an alternating electric field at a constant height above thin film sample 21. Scan controller 32 controls probe 13 to perform point-by-point scanning in the horizontal direction and records the horizontal coordinates of each sampling point. Based on the capacitance characteristics of thin film sample 21 and sapphire substrate 22, the capacitance of each sampling point changes due to differences in film thickness or dielectric constant. The changes in capacitance in the testing system correspond to different luminous intensities of the backlight nano-LED array.

[0061] The light signal generated by the backlight nano-LED array is transmitted to the photodetector 31 via the transparent conductive layer ITO 24 and converted into an AC signal. The image generation module 33 integrates the horizontal coordinate information of each sampling point provided by the scanning controller 32 with the peak voltage information corresponding to each sampling point provided by the photodetector, thereby characterizing the relative height of the sample surface within the scanning range, which allows for the analysis of the surface morphology of the thin film sample. The method for describing the three-dimensional image of the relative height of the thin film surface based on the peak voltage is an existing method, which can be found in Chaoxing Wu, Kun Wang, and Tailiang Guo. 2022. "Theoretical Study of LED Operating in Noncarrier Injection Mode" Nanomaterials 12, no. 15: 2532. https: / / doi.org / 10.3390 / nano12152532.

[0062] The embodiments of the present invention have now been described in detail with reference to the accompanying drawings. Based on the above description, those skilled in the art should have a clear understanding of the characterization system for thin film surface morphology of the present invention.

[0063] The above embodiments are preferred embodiments of the present invention, but the embodiments of the present invention are not limited to the above embodiments. Any changes, modifications, substitutions, combinations, or simplifications made without departing from the spirit and principle of the present invention shall be considered equivalent substitutions and shall be included within the protection scope of the present invention.

Claims

1. A characterization system for thin film surface morphology, characterized in that: Includes input area components, test area components, and output area components; The input region assembly is used to apply an alternating electric field over the thin film sample to be tested, and the input region assembly includes at least: AC power supply, used to output AC electric field signal to drive the backlight to emit light; A cantilever is used to conduct AC signals between the power supply and the probe, and to control the movement of the probe; A probe is used to maintain an alternating electric field above the thin film sample to be tested. The test area assembly is used to place the thin film sample to be tested and to emit light signals. The test area assembly includes at least: AC-driven backlight with dielectric substrate: used to generate an optical signal related to the thickness of the thin film sample under test by being excited by an alternating electric field, with the thin film sample placed on the dielectric substrate; ITO, as a transparent conductive layer, needs to be grounded; The output area component is used to receive and feed back test data and draw three-dimensional images, and the output area component includes at least: A photodetector is used to receive light signals generated by a backlight and convert them into electrical signals. The scanning controller is used to control the cantilever to move the probe at a constant height above the thin film sample to perform horizontal scanning and record the coordinate information of each sampling point corresponding to the probe. The image generation module is used to summarize the coordinates and peak voltage of each sampling point and describe a three-dimensional image of the relative height of the thin film surface.

2. The thin film surface morphology characterization system according to claim 1, characterized in that: The backlight source is a nano-LED array, a quantum dot film, or an organic light-emitting film.

3. The thin film surface morphology characterization system according to claim 1, characterized in that: The dielectric substrate is sapphire, silicon, or quartz.

4. The thin film surface morphology characterization system according to claim 1, characterized in that: The AC power supply is a sinusoidal AC power supply with a frequency of 10-100kHz.

5. A method for characterizing the surface morphology of a thin film, implemented based on the thin film surface morphology characterization system according to any one of claims 1-4, characterized in that... The steps include: (1) Place the thin film sample to be tested on a dielectric substrate; (2) An AC power supply excites an AC signal, which is transmitted to the probe through the cantilever and releases an alternating electric field above the thin film sample to be tested. The scanning controller controls the probe to always be at a constant height above the thin film sample to be tested and performs horizontal and vertical shift scanning. (3) An alternating electric field excites the backlight to generate an optical signal. The photodetector receives the optical signal generated by the backlight and converts it into an electrical signal. The coordinate information of each sampling point and the peak voltage of the corresponding photoelectric signal are output to the image generation module by the scanning controller and the photodetector, respectively, so as to draw a three-dimensional image of the relative height of the thin film surface morphology.

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