Our research is mainly cross-field integration research, such as integrating semiconductor solar photovoltaic components and single-cell biochips to achieve self-powered biochips, integrating various micro-nano process technologies such as laser interference lithography, anodized aluminum, and nanoparticles. Research on rice imprinting technology on solar cells and light-emitting diode components and the development of novel optical analysis technology on two-dimensional materials. In cross-field integrated research, the study of basic physical mechanisms is very important, such as the interaction between electrons and holes. The relationship between transmission and the polarity of cancer cells, the generation mechanism of surface plasmon waves by component surface microstructure, and the force between atomic layers in two-dimensional materials. These basic mechanisms involve physics, chemistry, materials, optics, etc. There are still many things that are not yet clear about these research topics. If these mysteries can be further solved, it will make a considerable contribution to both basic science and engineering. Houxue will explain relevant past research results:
[Application of hyperspectral imaging microscopy to detect large-area low-layer graphene films]
We use hyperspectral imaging technology to propose a new optical detection method, aiming to be applied to the layer number detection of large-area graphene films. In this study, chemical vapor deposition (CVD) was used to grow a few layers of graphene films on copper foil, and the graphene films were transferred to silicon dioxide (300nm)/silicon substrates and glass substrates respectively. First, Raman spectroscopy is used to measure graphene films transferred on different substrates. Since graphene films with different layers have different G-band intensities, the position of each layer can be analyzed. We then use an optical microscope and CCD to photograph the sample, and combine it with our hyperspectral imaging technology for analysis to capture the spectral characteristics of each layer, and calculate and discuss the spectral differences between graphene films with different layers. Since different numbers of layers have different spectral performances, the principal axis component analysis method is used to construct a database of spectral characteristics of different numbers of layers. This database can be used to identify the number of graphene layers on different substrates. Afterwards, a Graphical User Interface (GUI) was written in conjunction with Microsoft Visual Basic 2010, which can automatically, quickly and accurately mark the range of each layer of graphene in the image with different colors.
The purpose of this research is to construct a system for analyzing graphene films with different layers. The experimental process is shown in Figure 1. At the beginning of the experiment, a spectral characteristic database of graphene films with different layers must be established, and then used as a new sample. When analysis is to be performed, a comparison will be made against this database. The process of establishing the database is as follows: Use a Micro-Raman Spectrometer to measure the position of each layer distribution of the prepared graphene film sample, and use an optical microscope and CCD to capture images of the same position ( Image capture system (ICS), the CCD image obtained can be combined with multispectral imaging (MSI) to obtain the spectral characteristics (380nm-780nm) of each layer of the graphene film, and then use principal component analysis (Principle Component Ananaysis, PCA) and principal component score (PCS) analysis, we can define the judgment conditions for each layer, thus completing the establishment of our database. When a new graphene sample is to be analyzed, it is placed under an optical microscope and a CCD is used to capture surface images. However, since electronic products produce high-frequency noise during signal transmission, we perform median filtering on the image to remove noise (Noise Reduction), and then use hyperspectral imaging technology to obtain the spectral characteristic value of each pixel. Principal component score analysis calculates it with the discriminant of each layer of graphene film in the database to know the number of graphene film layers at the pixel position, and uses different colors to clearly distinguish the different layers of graphene film in the image. Mark it out.
The purpose of this research is to construct a system for analyzing graphene films with different layers. The experimental process is shown in Figure 1. At the beginning of the experiment, a spectral characteristic database of graphene films with different layers must be established, and then used as a new sample. When analysis is to be performed, a comparison will be made against this database. The process of establishing the database is as follows: Use a Micro-Raman Spectrometer to measure the position of each layer distribution of the prepared graphene film sample, and use an optical microscope and CCD to capture images of the same position ( Image capture system (ICS), the CCD image obtained can be combined with multispectral imaging (MSI) to obtain the spectral characteristics (380nm-780nm) of each layer of the graphene film, and then use principal component analysis (Principle Component Ananaysis, PCA) and principal component score (PCS) analysis, we can define the judgment conditions for each layer, thus completing the establishment of our database. When a new graphene sample is to be analyzed, it is placed under an optical microscope and a CCD is used to capture surface images. However, since electronic products produce high-frequency noise during signal transmission, we perform median filtering on the image to remove noise (Noise Reduction), and then use hyperspectral imaging technology to obtain the spectral characteristic value of each pixel. Principal component score analysis calculates it with the discriminant of each layer of graphene film in the database to know the number of graphene film layers at the pixel position, and uses different colors to clearly distinguish the different layers of graphene film in the image. Mark it out.
Figure 1. Establishment process of hyperspectral imaging technology database
Figure 2(a) shows the micro-Raman spectrum measurement results of sample A. It can be found that there are peaks near the Raman shift of 1581cm -1 and 2676cm -1 . According to the literature, it is known that these two peaks represent G respectively. -band and 2D-band, where G-band is an optical oscillation of carbon atoms that can be observed in various carbon materials, while 2D-band comes from the interaction between two phonons and light. The double resonance mode formed is related to the electrical structure of graphene. Through the ratio of G/2D, we can know the number of graphene film layers at the position of the Raman measurement sample and then know the microscope image of sample A. The distribution position of each layer in , is shown in Figure 2(b).
Figure 2. (a) Micro-Raman spectrum of sample A (b) Locating the positions of each layer of the sample through spectral analysis
We read the microscope image of sample A (shown in Figure 2(b)) for analysis. Using hyperspectral imaging technology, we can obtain the simulated spectrum of each pixel (Pixel) and input it into the database range defined in the previous section. Identify within the system, and then use different colors to mark the sample images of different layer positions, as shown in Figure 3(a), where black represents the position of the substrate, red, yellow, green, blue and white represent layers 1 to 4 respectively. And the position of more than four layers of graphene film, but from this image, it was found that there is a lot of noise in the analysis results. The noise may be due to the high-frequency noise generated by the CCD or image capture. In order to filter out These noises interfere with our analysis. We perform median filtering on the original image to reduce the noise. Then we analyze the median filtered image. The analysis results can be obtained as shown in Figure 3(b). From the results It is known that this method can indeed find the position of different layers of graphene films on silicon dioxide (300nm)/silicon substrate.
Figure 3. (a) Sample images at different layer positions (b) Analysis of images after median filtering
Black represents the position of the substrate, and red, yellow, green, blue, purple and white represent the positions of one to five layers and more than five layers of graphene films respectively. In Figure 3, the measurement results are obtained under an optical microscope using a 20x objective lens. The CCD display magnification is about 25x, so the overall magnification is about 500x. With this measurement system, we can get the image size on the CCD. Images of approximately 80530um 2 , these images have 640*480 pixels, and the calculated resolution of this system is approximately 500 nm. In order to understand whether this graphene analysis layer technology can achieve higher resolution, we magnified the sample to a 40x objective lens for measurement. Through this measurement system, we can obtain an image size of about 21410um on the CCD. 2 image, and the image has 640*480 pixels, the resolution of this system can be calculated to be approximately 250nm.
[Research on the application of hyperspectral image reconstruction technology in identifying the stage of bladder cancer cells]
We injected bladder cancer cells into the single-cell array chip (as shown in Figure 4(a)), allowing the cells to be arranged in an array to detect the type of bladder cancer cells. In addition to detecting bladder cancer cells using hyperspectral imaging technology (shown in Figure 4(b)), we also use Raman spectroscopy to measure bladder cancer cells (shown in Figure 5). Affected by keratin and tryptophan, Normal and cancerous cells will have different characteristic intensities. In this study, we imported four different human bladder (cancer) cells into single-cell array wafers, and analyzed the normal bladder cells E7 and three bladder cells (TSGH-8301, J82, TCC- SUP ) with varying degrees of cancer. The stage of each cell can be confirmed using methods such as phase contrast microscopy, multispectral imaging, principal component analysis, and automated cycling cell algorithms. The establishment of the entire research method was very complex, but it was very successful and fast for using single-cell array wafers to identify different stages of cancer cells. The average sensitivity and specificity in the diagnosis of bladder cancer cells at different stages were 85.7% and 91.2% in 419 bladder cells, and the results are shown in Figure 6. In the future, we will continue processing and identifying cancerous features in the image processing stage to improve detection accuracy. We hope that this method can detect different stages of cancer cells with rapid and easy identification.
Figure 4 (a) Single-cell biochip (b) Microscopic images of normal, second-stage, third-stage, and fourth-stage bladder cancer cells
Figure 5 Raman spectra of four types of cells
[Research on optical and material properties of metal oxide related materials]
We used nanoimprint technology to create a series of hexagonal hole nanostructures on the nGaN substrate, and then used the Sol-Gel-Like dip technique to grow 1.5μm n-type zinc oxide Nano-column, and finally use a radio frequency reactive magnetron sputtering machine to grow a 50nm nanometer-thick cuprous oxide film layer to form a pn Cu2O/ZnO core-shell structure. Through different According to the imprint width and imprint spacing, samples A, B, C, and D of Cu2O/ZnO Hetero-structure corresponding to the aperture ratios of 0.0627, 0.0392, 0.0832, and 0.0537 can be obtained respectively. Through SEM and AFM measurements, we can find that the 50nm Cu2O film is coated on the ZnO nanorod to form a core-shell structure. Then through the XRD and XRC analysis results, we find that the Cu2O lattice structure has multiple properties. The characteristics of the crystal, its lattice plane (lattice plane) is (111) and (220), and sample C has the narrowest XRC half-width value, so sample C has better material properties. In the measurement results of optical properties, we found that the luminescent PEAK of the test piece did not shift with changes in temperature, and sample C also had good optical properties. Through the analysis results of HRTEM, we can find that there is an intermediate layer at the internal junction of Cu2O/ZnO. The existence of this intermediate layer directly affects the lattice arrangement of Cu2O at the top, corners, and sides of the ZnO nanorod. The Cu2O film is in different The direction of nanorod interface growth has different lattice alignment directions. Finally, we found that samples with larger aperture ratios will have better optical properties and material properties. In the future, we hope to apply this structure to solar cell components.
[Preparation of zinc oxide/cuprous oxide photoelectrochemical biosensor and its application in the detection of esophageal cancer cells]
We use electrochemical deposition to grow p-type cuprous oxide films and hydrothermal method to grow n-type zinc oxide nanopillars. The structure of this PN heterojunction has sensitive photoelectrochemical (PEC) reactions and self-powering functions. Four types of human esophageal cancer cells (ECCs) were detected without applying additional bias voltage. The photocurrent measured by this biosensor for cancer cells with different degrees of canceration was compared with that of an empty biosensor. They are about 80~300% higher respectively, with a sensing time of about 0.5 seconds and the ability to repeat measurements for dozens of cycles.
Scheme 1 A PEC biosensor is proposed for rapid and accurate identification of different cancer stages human esophageal cells.
The picture below shows our academic achievements under this research theme.
Patent layout planning: Currently, 7 Taiwan patents (6 have been approved) and 6 U.S. patents (5 have been approved) have been applied for. The planning diagram is as follows:
Potential for academic merit
2004 was the most important time for the development of two-dimensional materials. That year, the research team of Professor AK Geim of the University of Manchester in the UK successfully produced graphene for the first time using a mechanical exfoliation method. Graphene has excellent properties such as high electrical conductivity, high thermal conductivity, high mechanical strength, transparency and other excellent properties. It soon attracted strong attention in various academic fields. This also won AK Geim and his student KSNovoselov the 2010 Nobel Prize in Physics. However, although graphene has many advantages, it unfortunately lacks an energy gap and cannot be effectively used in the field of field-effect transistors. In 2011, Professor A. Kis of the Ecole Polytechnique Fédérale de Lausanne in Switzerland successfully produced a single-layer molybdenum disulfide transistor using a mechanical exfoliation method. Its structure and semiconducting properties make it an ideal material for transistors and can be directly combined with Silicon competition. Molybdenum disulfide has three atomic layers in its structure and belongs to transition metal dichalcogenides (TMDs). Their chemical formula is MX2, where M is a transition metal (such as Mo or W) and X is a chalcogen element ( Such as S, Se and Te). Compared with graphene, it has more energy gaps. This type of material already has an indirect bandgap semiconductor in its multilayer state. When the thickness is reduced to a single-layer structure, a direct bandgap semiconductor will be formed, which will be effectively used in the fields of optoelectronics and semiconductors.
Recently, scientists have begun to study two-dimensional heterostructures. By superposing different two-dimensional materials, the electronic properties can be freely modulated, which brings unlimited business opportunities for researchers to explore new physics and develop new optoelectronic components. Two-dimensional heterostructures are particularly eye-catching in optoelectronic applications because the two-dimensional single-layer material has an optical energy gap and exhibits very strong optoelectronic interactions in the near-infrared to visible spectrum range. These materials are also ideal for light-emitting diodes, solar cells, and high carrier mobility electronics. In terms of basic research, literature on their electronic structures and interesting valley spin electrons is also emerging. An atomic-level two-dimensional material with a single layer or several layers of thickness. Its structural characteristic is that atoms are arranged in the same plane to form a hexagonal honeycomb structure. The production of single-layer two-dimensional materials was first formed by peeling off blocks, and its crystallization quality is better. As for the chemical vapor deposition method that is currently widely used, there is still room for improvement in large-area material production. Such materials include common graphene with conductor properties, transition metal dichalcogenides (Transition Metal Dichalcogenides) MoS2, WSe2, etc. with semiconductor energy gaps, and high dielectric coefficient insulator boron nitride (BN). In addition, there is also the use of molecular beam epitaxy to grow topological insulators (Topological Insulators) in which the material itself is an insulator but its surface is a conductor. After the advent of these materials, two-dimensional materials quickly became popular materials.
Because the layered two-dimensional material itself has special electronic conductivity, thermal conductivity, optical and mechanical properties, and is easy to integrate into today's device manufacturing processes, it is regarded as a novel material with great potential to replace silicon components. It has a great chance to become one of the material choices for the next generation of semiconductor devices after the size is reduced, and it can also be incorporated into flexible electronic component systems in the non-silicon era. Due to the rise of two-dimensional materials, there have been studies on stacking different two-dimensional materials in layers and exploring their unique properties. Heterogeneous materials such as stacks of graphene and MoS2 are connected by covalent bonds in the plane to form a network system (Network), and the upper and lower layers are stacked by weak van der Waals forces (Stack). The stack made of two-dimensional materials has multiple characteristics, so the possible components in the stack can include insulators, semiconductors, and even conductors. Therefore, the produced stack heterostructure has two layers composed of different two-dimensional materials. The above structure), exhibits homostructure characteristics that are different from those in the past.
In the past, our laboratory has used multi-spectral imaging technology, combined with single-cell biological chips provided by the Department of Mechanical Engineering, to conduct research on cancer cell staging based on optical image processing. On the other hand, we have also conducted semiconductor material synthesis and nanotechnology. Related research on nanometer microstructures. During the research process, we successfully produced some nanometer microstructures of cuprous oxide and zinc oxide. These micro-nanostructures were made using anodized aluminum technology and double-beam interference technology. Therefore, we hope to combine the two fields of biomedical detection and semiconductor component production through biochips, and use semiconductor material synthesis technology and micro-nano structure technology to produce biosensors. Based on this, we can develop a low-cost A biosensor with low cost, fast response time, and simple detection procedure, uses the heterostructure of PN semiconductor to produce a functional nanosemiconductor biosensor, and uses its photoelectrochemical characteristics to achieve the desired performance without applying additional bias voltage. Under the conditions, cancer cells are detected, reducing the interference of background noise on the detection signal and improving its sensitivity.
In the research on the preparation of optoelectronic components of two-dimensional materials, we have also conducted research on graphene/metal oxide/metal chalcogenide nanoheterostructures in the past, using the unique optoelectronic material properties to gain single-cell biosensor photoelectrochemistry and Self-powering properties and their applications. In the study, we used four esophageal cancer cell lines, namely OE21, OE21-1, CE81T2-1/VGH, and CE81T2-4/VGH, to sense targets of single-cell biosensors. . In past projects, we have also invited Prof. Fedorov Vladimir Efimovich from Nikolaev Institute of Inorganic Chemistry, Siberian Branch of the Russian Academy of Sciences as partners on this research topic. Prof. Fedorov's expertise is graphene and metal sulfur The growth and preparation of family compound materials, and the research on this part is also one of the key projects of this research.
Recently, scientists have begun to study two-dimensional heterostructures. By superposing different two-dimensional materials, the electronic properties can be freely modulated, which brings unlimited business opportunities for researchers to explore new physics and develop new optoelectronic components. Two-dimensional heterostructures are particularly eye-catching in optoelectronic applications because the two-dimensional single-layer material has an optical energy gap and exhibits very strong optoelectronic interactions in the near-infrared to visible spectrum range. These materials are also ideal for light-emitting diodes, solar cells, and high carrier mobility electronics. In terms of basic research, literature on their electronic structures and interesting valley spin electrons is also emerging. An atomic-level two-dimensional material with a single layer or several layers of thickness. Its structural characteristic is that atoms are arranged in the same plane to form a hexagonal honeycomb structure. The production of single-layer two-dimensional materials was first formed by peeling off blocks, and its crystallization quality is better. As for the chemical vapor deposition method that is currently widely used, there is still room for improvement in large-area material production. Such materials include common graphene with conductor properties, transition metal dichalcogenides (Transition Metal Dichalcogenides) MoS2, WSe2, etc. with semiconductor energy gaps, and high dielectric coefficient insulator boron nitride (BN). In addition, there is also the use of molecular beam epitaxy to grow topological insulators (Topological Insulators) in which the material itself is an insulator but its surface is a conductor. After the advent of these materials, two-dimensional materials quickly became popular materials.
Because the layered two-dimensional material itself has special electronic conductivity, thermal conductivity, optical and mechanical properties, and is easy to integrate into today's device manufacturing processes, it is regarded as a novel material with great potential to replace silicon components. It has a great chance to become one of the material choices for the next generation of semiconductor devices after the size is reduced, and it can also be incorporated into flexible electronic component systems in the non-silicon era. Due to the rise of two-dimensional materials, there have been studies on stacking different two-dimensional materials in layers and exploring their unique properties. Heterogeneous materials such as stacks of graphene and MoS2 are connected by covalent bonds in the plane to form a network system (Network), and the upper and lower layers are stacked by weak van der Waals forces (Stack). The stack made of two-dimensional materials has multiple characteristics, so the possible components in the stack can include insulators, semiconductors, and even conductors. Therefore, the produced stack heterostructure has two layers composed of different two-dimensional materials. The above structure), exhibits homostructure characteristics that are different from those in the past.
In the past, our laboratory has used multi-spectral imaging technology, combined with single-cell biological chips provided by the Department of Mechanical Engineering, to conduct research on cancer cell staging based on optical image processing. On the other hand, we have also conducted semiconductor material synthesis and nanotechnology. Related research on nanometer microstructures. During the research process, we successfully produced some nanometer microstructures of cuprous oxide and zinc oxide. These micro-nanostructures were made using anodized aluminum technology and double-beam interference technology. Therefore, we hope to combine the two fields of biomedical detection and semiconductor component production through biochips, and use semiconductor material synthesis technology and micro-nano structure technology to produce biosensors. Based on this, we can develop a low-cost A biosensor with low cost, fast response time, and simple detection procedure, uses the heterostructure of PN semiconductor to produce a functional nanosemiconductor biosensor, and uses its photoelectrochemical characteristics to achieve the desired performance without applying additional bias voltage. Under the conditions, cancer cells are detected, reducing the interference of background noise on the detection signal and improving its sensitivity.
In the research on the preparation of optoelectronic components of two-dimensional materials, we have also conducted research on graphene/metal oxide/metal chalcogenide nanoheterostructures in the past, using the unique optoelectronic material properties to gain single-cell biosensor photoelectrochemistry and Self-powering properties and their applications. In the study, we used four esophageal cancer cell lines, namely OE21, OE21-1, CE81T2-1/VGH, and CE81T2-4/VGH, to sense targets of single-cell biosensors. . In past projects, we have also invited Prof. Fedorov Vladimir Efimovich from Nikolaev Institute of Inorganic Chemistry, Siberian Branch of the Russian Academy of Sciences as partners on this research topic. Prof. Fedorov's expertise is graphene and metal sulfur The growth and preparation of family compound materials, and the research on this part is also one of the key projects of this research.
