Haixia Shang

Phase shifting nano-moiré method with scanning tunneling microscope

In this paper, a new nano-moire method using scanning tunneling microscope (STM) is proposed. This method is capable of measuring nanoscopic deformation of matter. The formation mechanism of the STM moire fringe and the phase shifting technique used in STM moire fringes are explained in details. Typical experiments are conducted with the crystal lattices of freshly cleaved highly oriented pyrolytic graphite, are used as specimen grating, to generate STM moire fringe patterns. Phase shifting is realized in four steps from 0 to 2π by controlling the PZT in the STM system to shift the specimen in the vertical direction. This method provides a new way for disposal of moire fringes pattern in the nano-moire measurement.

Nanometre moire fringes in scanning tunnelling microscopy of surface lattices

A novel class of moire fringe patterns in scanning tunnelling microscope (STM) imaging is presented and analysed in this paper. The moire fringe is generated from the interference of the atomic lattice of the specimen and STM scanning lines. Both parallel and rotational STM moire fringes of the surface of highly oriented pyrolytic graphite (HOPG) are investigated. The formation principle and experimental techniques of STM moire fringes are discussed. Nanometre scale resolution and sensitivity are found in the moire fringe patterns. They precisely magnify the STM image of lattice irregularities. A potential application—measuring surface deformation and defects in the nanometre range—is proposed.

Phase shifting focused ion beam moiré method

In this article, a phase shifting technique for focused ion beam (FIB) moire method is proposed, which is able to measure the full field in-plane deformation of an object in a micrometer scale. The FIB moire is generated by the interference between a prepared specimen grating and FIB raster scan lines. The principle of phase shifting technique for FIB moire is described in detail. With this method, phase shifting was realized in four steps from 0 to 2 π by shifting the focused ion beam controlled by a FIB system. This method is successfully used to measure the virtual deformation in a micro-electro-mechanical system structure with a 2500 lines/mm grating. The experiments prove the validity of this technique and show its ability of determine the full field strain with high accuracy.

Three dimensional moire interferometer

A new moire interferometer, known as multifunction 3D function interferometry system is developed by authors, which combines the advantages of four-beam moire interferometer with the Twyman/Green interference system. The system can measure in-plane and out-of-plane deformation synchronously with high accuracy and high sensitivity. A compact phase shifter is used to improve the measurement sensitivity. The optical theory, components, key techniques, unique ability, and specifications of the system are described in detail in this paper. Some typical experiments using this system have been done and gained good results.

Micro/nano grating and its application to moire measurement

In this paper, some novel micro/nano- moire grating fabricating techniques are introduced. The gratings are produced by the SPM lithography, FIB lithography, and molecular beam epitaxy (MBE) method. The moire patterns formed with these gratings are also introduced. The gratings are successfully to be used to measure the residual deformation in the surface around a step edge of the Al/Si artificial nanocluster with the moire methods. The successful experimental results verify the feasibility of these methods.

Application of phase shifting technique for SEM scanning moire method im MEMS

A new phase shifting SEM scanning moire method is proposed in this paper. The phase shifting technique is realized in four steps from 0 to 2 π by shifting electron beam in y-axis direction controlled by SEM system. It is successfully applied to measure the virtual strain of a MEMS structure with grating of 5000 lines/mm. The experiments prove the technique can be widely used in meso-deformation measurement, and also show the sensitivity of experiments is highly improved after phase shifting technique. It provides a new way for disposal of fringes patterns in sub-micro moire method.

Development of the Advanced Moiré Methods With High Resolution Microscopy at Fml

The mechanical behaviours of engineering materials in micro/nanoscopic range have aroused general concern in recent years. To understand the rule of these behaviours, the experimental technique with high sensitivity and spatial resolution are required. However, most of the existing methods cannot meet such requirements. Some novel micro/nano-moire methods have been developed recently at failure mechanics lab. (FML), Tsinghua University, China. This paper offers an introduction of these new methods, which can be realized under the focus ion beam (FIB), atomic force microscope (AFM), scanning tunnelling microscope (STM), laser scanning confocal microscope (LSCM) as well as the transmission electron microscope (TEM). These micro/nano-moire methods are able to offer quantitative analysis to micro/nano-deformation of the sample surface. The measurement principles and experimental techniques of these methods are described in detail. Some applications of these methods are given. The successful experimental results demonstrate the feasibility of these methods and also verify that the methods can offer a high sensitivity for displacement measurement with mico/nano-meter spatial resolution, and it will find a wide application in micro/ nano-mechanics research.

Micro/nano moire methods

Two novel micro/nano moire method, SEM scanning moiré and AFM scanning moire techniques are discussed in this paper. The principle and applications of two scanning moire methods are described in detail. The residual deformation in a polysilicon MEMS cantilever structure with a 5000 lines/mm grating after removing the SiO2 sacrificial layer is accurately measured by SEM scanning moire method. While AFM scanning moire method is used to detect thermal deformation of electronic package components, and formation of nano-moire on a freshly cleaved mica crystal. Experimental results demonstrate the feasibility of these two moire methods, and also show they are effective methods to measure the deformation from micron to nano-scales.