Papers by Author: Li Han

Abstract: 100nm thin Mg/B precursor films were prepared on SiC substrates in ZZSX-500 vacuum coating machine. They were annealed by electron-beam(EB) which only took fractions of a second. In this paper the best annealing duration to fabricate the superconducting MgB₂ thin films was investigated. Under the optimized annealing condition(accelerating voltage 15kV, electron beam current 5mA, annealing duration 0.7s), the superconducting MgB₂ thin film with critical temperature Tc^onset~35.3 K and transition width ∆Tc~1K was fabricated. Besides that, a nano-bridge (about 100×200nm²) was etched on the superconducting MgB₂ thin film by Focused Ion Beam (FIB). It’s a relative simple and efficient method. The nano-bridge exhibited the effect of Josephson junction with RSJ characteristics. At the same time a little loss of superconducting property was detected.

Abstract: Micro-structure dimension metrology is a grand challenge to current metrological methods and tools. In this paper, a retraceable metrological scanning electron microscopy (M-SEM) system with precision stage and laser interferometer is presented in detail. The double stages structure is used to realize both sample positioning in 50mm×50mm range and accuracy imaging in several tens of micron scale. In order to acquiring metrological scanning image, the control system based on digital signal processing (DSP) is constructed. Furthermore, this paper focuses on demonstrating a metrological SEM image edge detection algorithm which is the essential part of the metrological SEM system to realize the traceable metrology of line width.

Abstract: Scanning tunneling microscope (STM) has several advantages, such as high resolution, and is wildly used. Piezoelectric scanner brings the horizontal resolution of STM up to 0.1 nm, and is it derived by piezoelectric ceramic. Piezoelectric scanner has piezoelectric ceramic’s character. So, piezoelectric scanner output must be calibrated at regular intervals. Graphite atom arrange in a special manner. In the same layer, the distance between adjacent atoms is the same, 0.25nm. This feature can be used to measure length and calibrate small scale scanning. For the 512 × 512 resolution image, the maximum scan range that can distinguish atoms is 30nm2. More large area of atomic image needs to use image stitching technology. By image stitching, small scale scanning, less than 1μm can be calibrated.