Fangzhou Xia

@article{2023JoVE,

title = {Active Probe Atomic Force Microscopy with Quattro-Parallel Cantilever Arrays for High-Throughput Large-Scale Sample Inspection},

author = {Fangzhou Xia* and Kamal Youcef-Toumi and Thomas Sattel and Eberhard Manske and Ivo W. Rangelow},

url = {https://www.jove.com/t/65210},

doi = {10.3791/65210},

issn = {1940-087X},

year  = {2023},

date = {2023-06-16},

urldate = {2023-06-16},

journal = {Journal of Visualized Experiments},

pages = {e65210},

abstract = {An Atomic Force Microscope (AFM) is a powerful and versatile tool for nanoscale surface studies to capture 3D topography images of samples. However, due to their limited imaging throughput, AFMs have not been widely adopted for large-scale inspection purposes. Researchers have developed high-speed AFM systems to record dynamic process videos in chemical and biological reactions at tens of frames per second, at the cost of a small imaging area of up to several square micrometers. In contrast, inspecting large-scale nanofabricated structures, such as semiconductor wafers, requires nanoscale spatial resolution imaging of a static sample over hundreds of square centimeters with high productivity. Conventional AFMs use a single passive cantilever probe with an optical beam deflection system, which can only collect one pixel at a time during AFM imaging, resulting in low imaging throughput. This work utilizes an array of active cantilevers with embedded piezoresistive sensors and thermomechanical actuators, which allows simultaneous multi-cantilever operation in parallel operation for increased imaging throughput. When combined with large-range nano-positioners and proper control algorithms, each cantilever can be individually controlled to capture multiple AFM images. With data-driven post-processing algorithms, the images can be stitched together, and defect detection can be performed by comparing them to the desired geometry. This paper introduces principles of the custom AFM using the active cantilever arrays, followed by a discussion on practical experiment considerations for inspection applications. Selected example images of silicon calibration grating, highly-oriented pyrolytic graphite, and extreme ultraviolet lithography masks are captured using an array of four active cantilevers ("Quattro") with a 125 {textmu}m tip separation distance. With more engineering integration, this high-throughput, large-scale imaging tool can provide 3D metrological data for extreme ultraviolet (EUV) masks, chemical mechanical planarization (CMP) inspection, failure analysis, displays, thin-film step measurements, roughness measurement dies, and laser-engraved dry gas seal grooves.},

keywords = {Atomic Force Microscopy, Automation, Experimentation, Instrumentation, Material Science, Mechatronics, MEMS, Method, Sensor},

pubstate = {published},

tppubtype = {article}

}

@article{2023IEEETM,

title = {AFM SMILER: A Scale Model Interactive Learning Extended Reality Toolkit for Atomic Force Microscopy based on Digital Twin Technology},

author = {Fangzhou Xia* and Shane Lovet and Eyan Forsythe and Malek Ibrahim and Kamal Youcef-Toumi},

url = {https://ieeexplore.ieee.org/abstract/document/10136835},

doi = {10.1109/TMECH.2023.3274695},

year  = {2023},

date = {2023-06-01},

urldate = {2023-01-01},

journal = {IEEE Transactions on Mechatronics (in preparation)},

abstract = {Atomic force microscope (AFM) is a precision mechatronic system for nanoscale imaging of surfaces. Due to limited instrument access and lack of visualization techniques, understanding its principles can be challenging. Digital twin technology allows the creation of virtual representations of physical systems, which can be particularly useful to address challenges in AFM education. To realistically simulate nanoscale physics, we first developed new efficient algorithms for four virtual scale models, including cantilever mechanics, probe transducers, controller tuning, and contact mechanics. Second, three simulated experiment interactive learning modules are developed for instrument operation, including virtual imaging, system overview, and imaging modalities. In the end, three hardware systems are integrated for an extended reality experience, including a macroscopic AFM scale model, a haptic device for probe-sample interaction force feedback and an upgraded low-cost educational AFM for nanoscale imaging and instrumentation. This completes the eight total modules for the AFM SMILER: A Scale Model Interactive Learning Extended Reality toolkit. Preliminary studies shows the toolkit being helpful for AFM education. In addition to mechatronics and nanotechnology education, techniques developed in this work can be generally applied to computationally efficient realistic digital twin creation.},

keywords = {Atomic Force Microscopy, Design, Education, Experimentation, Instrumentation, Intelligence, Mechatronics, MEMS, Modeling & Simulation, Nanorobotics, Sensor, Theory},

pubstate = {published},

tppubtype = {article}

}

@article{2022MDPIBiosensors,

title = {Review: Advanced Atomic Force Microscopy for Biomedical Research},

author = {Fangzhou Xia* and Kamal Youcef-Toumi},

url = {https://www.mdpi.com/2079-6374/12/12/1116},

year  = {2022},

date = {2022-01-01},

urldate = {2022-01-01},

journal = {Biosensors},

volume = {12},

number = {12},

pages = {1116},

publisher = {MDPI},

abstract = {Visualization of biomedical samples in their native environments at the microscopic scale is crucial for studying fundamental principles and discovering biomedical systems with complex interaction. The study of dynamic biological processes requires a microscope system with multiple modalities, high spatial/temporal resolution, large imaging ranges, versatile imaging environments and ideally in-situ manipulation capabilities. Recent development of new Atomic Force Microscopy (AFM) capabilities has made it such a powerful tool for biological and biomedical research. This review introduces novel AFM functionalities including high-speed imaging for dynamic process visualization, mechanobiology with force spectroscopy, molecular species characterization, and AFM nano-manipulation. These capabilities enable many new possibilities for novel scientific research and allow scientists to observe and explore processes at the nanoscale like never before. Selected application examples from recent studies are provided to demonstrate the effectiveness of these AFM techniques.},

keywords = {Atomic Force Microscopy, Instrumentation, Medication, MEMS, Nanorobotics, Review},

pubstate = {published},

tppubtype = {article}

}

@article{2021Mechatronics,

title = {A Modular Low-cost Atomic Force Microscope for Precision Mechatronics Education},

author = {Fangzhou Xia* and James Edwin Quigley and Xiaotong Zhang and Chen Yang and Yi Wang and Kamal Youcef-Toumi},

url = {https://www.sciencedirect.com/science/article/abs/pii/S0957415821000441},

issn = {0957-4158},

year  = {2021},

date = {2021-01-01},

urldate = {2021-01-01},

journal = {Mechatronics},

volume = {76},

pages = {102550},

publisher = {Elsevier},

abstract = {Precision mechatronics and nanotechnology communities can both benefit from a course centered around an Atomic Force Microscope (AFM). Developing an AFM can provide precision mechatronics engineers with a valuable multidisciplinary hands-on training experience. In return, such expertise can be applied to the design and implementation of new precision instruments, which helps nanotechnology researchers make new scientific discoveries. However, existing AFMs are not suitable for mechatronics education due to their different original design intentions. Therefore, we address this challenge by developing an AFM intended for precision mechatronics education.



This paper presents the design and implementation of an educational AFM and its corresponding precision mechatronics class. The modular educational AFM is low-cost (<4,000$) and easy to operate. The cost reduction is enabled by new subsystem development of a buzzer-actuated scanner and demodulation electronics designed to interface with a myRIO data acquisition system. Moreover, the use of an active cantilever probe with piezoresistive sensing and thermomechanical actuation significantly reduced experiment setup overhead with improved operational safety. In the end, the developed AFM capabilities are demonstrated with imaging results. The paper also showcases the course design centered around selected subsystems. The new AFM design allows scientific-method-based learning, maximizes utilization of existing resources, and offers potential subsystem upgrades for high-end research applications. The presented instrument and course can help connect members of both the AFM and the mechatronics communities to further develop advanced techniques for new applications.},

keywords = {Atomic Force Microscopy, Design, Education, Experimentation, Instrumentation, Mechatronics, Nanorobotics, Signal Processing},

pubstate = {published},

tppubtype = {article}

}

@article{2019NM,

title = {Lights Out! Nano-Scale Topography Imaging of Sample Surface in Opaque Liquid Environments with Coated Active Cantilever Probes},

author = {Fangzhou Xia* and Chen Yang and Yi Wang and Kamal Youcef-Toumi and Christoph Reuter and Tzvetan Ivanov and Mathias Holz and Ivo W Rangelow},

url = {https://www.mdpi.com/2079-4991/9/7/1013},

year  = {2019},

date = {2019-01-01},

urldate = {2019-01-01},

journal = {Nanomaterials},

volume = {9},

number = {7},

pages = {1013},

publisher = {Multidisciplinary Digital Publishing Institute},

abstract = {Atomic force microscopy is a powerful topography imaging method used widely in nanoscale metrology and manipulation. A conventional Atomic Force Microscope (AFM) utilizes an optical lever system typically composed of a laser source, lenses and a four quadrant photodetector to amplify and measure the deflection of the cantilever probe. This optical method for deflection sensing limits the capability of AFM to obtaining images in transparent environments only. In addition, tapping mode imaging in liquid environments with transparent sample chamber can be difficult for laser-probe alignment due to multiple different refraction indices of materials. Spurious structure resonance can be excited from piezo actuator excitation. Photothermal actuation resolves the resonance confusion but makes optical setup more complicated. In this paper, we present the design and fabrication method of coated active scanning probes with piezoresistive deflection sensing, thermomechanical actuation and thin photoresist polymer surface coating. The newly developed probes are capable of conducting topography imaging in opaque liquids without the need of an optical system. The selected coating can withstand harsh chemical environments with high acidity (e.g., 35% sulfuric acid). The probes are operated in various opaque liquid environments with a custom designed AFM system to demonstrate the imaging performance. The development of coated active probes opens up possibilities for observing samples in their native environments.},

keywords = {Atomic Force Microscopy, Experimentation, Instrumentation, Material Science, Mechatronics, MEMS, Nanorobotics, Sensor},

pubstate = {published},

tppubtype = {article}

}

@article{2018IEEETIE,

title = {Charge controller with decoupled and self-compensating configurations for linear operation of piezoelectric actuators in a wide bandwidth},

author = {Chen Yang* and Changle Li and Fangzhou Xia and Yanhe Zhu and Jie Zhao and Kamal Youcef-Toumi},

url = {https://ieeexplore.ieee.org/document/8466119},

year  = {2018},

date = {2018-01-01},

urldate = {2018-01-01},

journal = {IEEE Transactions on Industrial Electronics},

volume = {66},

number = {7},

pages = {5392-5402},

publisher = {IEEE},

abstract = {Charge control is a well-known sensorless approach to operate piezoelectric actuators, which has been proposed for more than 30 years. However, it is rarely used in industry because the implemented controllers suffer from the issues of limited low-frequency performance, long settling time, floating-load, and loss of stroke, etc. In this paper, a novel controller circuit dedicated to overcome these issues is presented. In the proposed scheme, a grounded-load charge controller with decoupled configuration is developed, which separates high-frequency and low-frequency paths, thus achieving arbitrarily low transition frequency without increasing the settling time. Based on this, a self-compensating configuration is further proposed and integrated into the controller circuit, which makes full use of controller output to improve its own control performance at low frequencies. Experimental results show that the presented charge controller can effectively reduce more than 88% of the hysteretic nonlinearity even when operating close to the transition frequency. To demonstrate its practical value, we then integrate it into a custom-designed high-speed atomic force microscope system. By comparing images obtained from using voltage drive and charge controller, it is clear that the piezoelectric hysteresis has been significantly reduced in a wide bandwidth.},

keywords = {Atomic Force Microscopy, Experimentation, Instrumentation, Mechatronics, Motion Control, Piezoelectricity, Theory},

pubstate = {published},

tppubtype = {article}

}

@article{2017JVST,

title = {Active scanning probes: A versatile toolkit for fast imaging and emerging nanofabrication},

author = {Ivo W Rangelow* and Tzvetan Ivanov and Ahmad Ahmad and Marcus Kaestner and Claudia Lenk and Iman S Bozchalooi and Fangzhou Xia* and Kamal Youcef-Toumi and Mathias Holz and Alexander Reum},

url = {https://avs.scitation.org/doi/10.1116/1.4992073},

year  = {2017},

date = {2017-01-01},

urldate = {2017-01-01},

journal = {Journal of Vacuum Science & Technology B, Nanotechnology and Microelectronics: Materials, Processing, Measurement, and Phenomena},

volume = {35},

number = {6},

pages = {06G101},

publisher = {AVS},

abstract = {With the recent advances in the field of nanotechnology, measurement and manipulation requirements at the nanoscale have become more stringent than ever before. In atomic force microscopy, high-speed performance alone is not sufficient without considerations of other aspects of the measurement task, such as the feature aspect ratio, required range, or acceptable probe-sample interaction forces. In this paper, the authors discuss these requirements and the research directions that provide the highest potential in meeting them. The authors elaborate on the efforts toward the downsizing of self-sensed and self-actuated probes as well as on upscaling by active cantilever arrays. The authors present the fabrication process of active probes along with the tip customizations carried out targeting specific application fields. As promising application in scope of nanofabrication, field emission scanning probe lithography is introduced. The authors further discuss their control and design approach. Here, microactuators, e.g., multilayer microcantilevers, and macroactuators, e.g., flexure scanners, are combined in order to simultaneously meet both the range and speed requirements of a new generation of scanning probe microscopes.},

keywords = {Actuator, Atomic Force Microscopy, Instrumentation, MEMS, Nanorobotics, Review, Sensor},

pubstate = {published},

tppubtype = {article}

}