Dr. Sai Gao Profile

Dr. Sai Gao

at Physikalisch-Technische Bundesanstalt

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Author

Publications (19)

Proceedings Article | 15 August 2023 Paper

Characterization of the maximum measurable slope of optical topography measuring instruments

Sai Gao, Andre Felgner, Dorothee Hueser, Silvana Wyss, Uwe Brand

Proceedings Volume 12618, 126182L (2023) https://doi.org/10.1117/12.2673840

KEYWORDS: Optical spheres, Objectives, Microscopes, Optical testing, Equipment, Confocal microscopy, 3D metrology, Optical microscopes, Signal detection, Optical surfaces

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Proceedings Article | 10 August 2023 Presentation + Paper

Simulation of light scattering from complex 3D structures for confocal microscope using accelerated boundary element method

L. Fu, A. Birk, K. Frenner, Sai Gao, S. Reichelt

Proceedings Volume 12619, 1261908 (2023) https://doi.org/10.1117/12.2688329

KEYWORDS: Confocal microscopy, Microscopes, Light scattering, Equipment, 3D modeling, Silicon, Modeling

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Proceedings Article | 10 August 2023 Presentation + Paper

Rigorous modeling of a confocal microscope

Silvana Wyss, Jan Krüger, Jana Grundmann, Bernd Bodermann, Sai Gao, Liwei Fu, Alexander Birk, Karsten Frenner, Stephan Reichelt

Proceedings Volume 12619, 126190Q (2023) https://doi.org/10.1117/12.2673784

KEYWORDS: Simulations, Finite-difference time-domain method, Microscopes, Light sources and illumination, Finite element methods, Confocal microscopy, Reflection, Diffraction, Plane waves

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Proceedings Article | 20 May 2022 Paper

Development of a sinusoidal pseudochirp material measure for the characterization of optical surface topography measuring instruments

Andre Felgner, Sai Gao, Dorothee Hueser, Uwe Brand

Proceedings Volume 12137, 121370S (2022) https://doi.org/10.1117/12.2621821

KEYWORDS: Microscopes, Confocal microscopy, Standards development, Optical testing, Objectives, Optical microscopes, Calibration, Spatial resolution, Spatial frequencies, Optical components

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Proceedings Article | 21 June 2019 Presentation + Paper

Characterization of the topography fidelity of 3D optical microscopy

S. Gao, A. Felgner, D. Hüser, L. Koenders

Proceedings Volume 11057, 110570G (2019) https://doi.org/10.1117/12.2526032

KEYWORDS: 3D metrology, Optical microscopy

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Proceedings Article | 7 June 2017 Paper

A multi-functional MEMS-SPM for quantitative characterization of nano-objects

Zhi Li, Sai Gao, Uwe Brand, Karla Hiller, Nicole Wollschläger, Xianghui Zhang

Proceedings Volume 10246, 102460J (2017) https://doi.org/10.1117/12.2265680

KEYWORDS: Scanning probe microscopy, Head, Transducers, Graphene, Prototyping, Silicon, Sensing systems, Microelectromechanical systems, Calibration, Atomic force microscopy, Metrology, Actuators, Microscopes, Microscopy, Atomic force microscope, Microfabrication

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Proceedings Article | 21 May 2015 Paper

Smart sensors and calibration standards for high precision metrology

Uwe Brand, Sai Gao, Lutz Doering, Zhi Li, Min Xu, Sebastian Buetefisch, Erwin Peiner, Joachim Fruehauf, Karla Hiller

Proceedings Volume 9517, 95170V (2015) https://doi.org/10.1117/12.2179455

KEYWORDS: Silicon, Standards development, Calibration, Microelectromechanical systems, Sensors, Microtechnology, Metrology, Atomic force microscopy, Sensor calibration, Bridges

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Proceedings Article | 21 May 2015 Paper

An active reference spring array for in-situ calibration of the normal spring constant of AFM cantilevers

S. Gao, U. Brand, S. Hahn, K. Hiller

Proceedings Volume 9517, 951719 (2015) https://doi.org/10.1117/12.2178850

KEYWORDS: Microelectromechanical systems, Calibration, Atomic force microscopy, Transducers, Semiconducting wafers, Etching, Autoregressive models, Photomasks, Reactive ion etching, Wafer bonding

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Proceedings Article | 1 May 2014 Paper

Towards traceable mechanical properties measurement of silicon nanopillars using contact resonance force microscopy

S. Gao, U. Brand

Proceedings Volume 9132, 91321D (2014) https://doi.org/10.1117/12.2052475

KEYWORDS: Atomic force microscopy, Silicon, Calibration, Transducers, Fourier transforms, Microscopy, Microelectromechanical systems, Interferometers, Finite element methods, Iron

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Proceedings Article | 1 May 2014 Paper

A dual-styli micro-machined system for precise determination of the thickness of free-standing thin films

Zhi Li, Sai Gao, Helmut Wolff, Uwe Brand, Ludger Koenders

Proceedings Volume 9132, 91321G (2014) https://doi.org/10.1117/12.2052415

KEYWORDS: Microelectromechanical systems, Silicon, Transducers, Interferometers, Thin films, Microfabrication, Glasses, Sensors, Calibration, Sapphire

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Proceedings Article | 5 May 2012 Paper

A micro-SPM head array with exchangeable cantilevers

S. Gao, H. Wolff, K. Herrmann, U. Brand, K. Hiller, S. Hahn, A. Sorger, J. Mehner

Proceedings Volume 8430, 84301E (2012) https://doi.org/10.1117/12.922641

KEYWORDS: Head, Actuators, Scanning probe microscopy, Microelectromechanical systems, Capacitance, Metrology, Time metrology, Calibration, Structural design, Scanning tunneling microscopy

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Proceedings Article | 8 September 2011 Paper

Lateral comb-drive MEMS structure for micro-measuring probe application

Fengming Sun, Sai Gao, Xing Fu, Uwe Brand, Konrad Herrmann

Proceedings Volume 8191, 81911H (2011) https://doi.org/10.1117/12.900706

KEYWORDS: Capacitance, Microelectromechanical systems, Actuators, Ruby, Optical spheres, Sensing systems, Sensors, Analog electronics, Calibration, Metrology

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Proceedings Article | 5 May 2011 Paper

A comb-drive scanning-head array for fast scanning-probe microscope measurements

S. Gao, H. Wolff, K. Herrmann, U. Brand, K. Hiller, S. Hahn, A. Sorger, J. Mehner

Proceedings Volume 8066, 806626 (2011) https://doi.org/10.1117/12.886938

KEYWORDS: Head, Microelectromechanical systems, Actuators, Scanning probe microscopy, Calibration, Capacitance, Sensing systems, Prototyping, Microscopes, Interferometers

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Proceedings Article | 14 May 2010 Paper

A micro-SPM head array for large-scale topography measurement

S. Gao, Z. Li, K. Herrmann

Proceedings Volume 7718, 77181L (2010) https://doi.org/10.1117/12.854397

KEYWORDS: Head, Scanning probe microscopy, Actuators, Microelectromechanical systems, Metrology, Atomic force microscopy, Interferometers, Calibration, Sensing systems, Scanning probe microscopes

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Proceedings Article | 14 May 2010 Paper

An optical microform calibration system for ball-shaped hardness indenters

Zhi Li, Sai Gao, Konrad Herrmann

Proceedings Volume 7718, 77181C (2010) https://doi.org/10.1117/12.854800

KEYWORDS: Calibration, Confocal microscopy, Microscopes, Objectives, Spherical lenses, Optical testing, Optical calibration, Sensors, Polarizers, Image resolution

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Proceedings Article | 25 April 2008 Paper

In-situ imaging of interlayer nanodeformation with improved differential confocal microscopy

Z. Li, S. Gao, K. Herrmann

Proceedings Volume 6995, 699516 (2008) https://doi.org/10.1117/12.780267

KEYWORDS: Confocal microscopy, Sensors, Microscopes, Finite element methods, Light sources, Prototyping, Inspection, Reflection, Mathematical modeling, Beam splitters

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Nanoindentation testing has proved to be an effective tool to determine the mechanical properties of small volumes of materials applied in various micro-systems, including hardness, indentation modulus, creep and so on. Nowadays, with the help of advanced numerical methods, especially the finite element analysis (FEA) technique, further mechanical properties of the material under test (e.g. tensile strength, etc.) can be interpreted from the typical indentation curve. However, the reliability and accuracy of these analytical models have to be well tested. Recently, the deformed topography of the interlayer surface within the tip-film-substrate system has been proposed to be the reference for the evaluation of FEA and other mathematic models for indentation testing. Here an in-situ interlayer deformation imaging system based on differential confocal microscopy is therefore developed, which has the capability to measure in-situ the real-time topography deformation within a layered specimen during nanoindentation testing. By means of linear regression and interpolation of the linear region of the standard confocal microscopy, differential confocal microscopy (DCM) can achieve a very high resolution for topography measurements. However, the actual capability and measurement uncertainty of DCM would be subject to those common-mode error sources like surface heterogeneity, intensity fluctuation of the light source, etc. In this paper an improved DCM is proposed, which introduces an additional point detector to the conventional DCM, creating dual confocal signals with slight relative axial shifting. The real topography of the surface under test can then be easily deconvoluted from the dual differential signals, whilst the common-mode errors within the measurement are eliminated. A prototype was developed and applied for measuring a step-height composed of two different materials and for in-situ inspection of the interlayer deformation during nanoindentation testing. Preliminary experimental results verify the feasibility and accuracy of the proposed method.

Proceedings Article | 25 April 2008 Paper

Determination of in-plane displacement of MEMS by means of an AFM sensor

S. Gao, Z. Li, K. Herrmann

Proceedings Volume 6993, 69930J (2008) https://doi.org/10.1117/12.780407

KEYWORDS: Microelectromechanical systems, Atomic force microscopy, Sensors, Actuators, Scanning probe microscopy, Inspection, Confocal microscopy, Performance modeling, Calibration, Finite element methods

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Proceedings Article | 25 April 2008 Paper

A microelectromechanical force actuator for nano-tensile testing system

S. Gao, K. Herrmann

Proceedings Volume 6993, 69930H (2008) https://doi.org/10.1117/12.780400

KEYWORDS: Actuators, Microelectromechanical systems, Prototyping, Finite element methods, Calibration, 3D modeling, Thin films, Interferometers, Atomic force microscopy, Silicon

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Proceedings Article | 9 October 2000 Paper

New advance in laser interferometry

Chunyong Yin, Zhixia Chao, Sai Gao, Hong Jiang, Jin Sun

Proceedings Volume 4221, (2000) https://doi.org/10.1117/12.402620

KEYWORDS: Interferometers, Laser stabilization, Semiconductor lasers, Laser interferometry, Heterodyning, Reflection, Polarization, Laser applications, Mirrors, Velocity measurements

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Showing 5 of 19 publications

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