Surface etching induced by Ce silicide formation on Si(1 0 0)

We investigate the temperature-dependent surface etching process induced by Ce silicide on Si(1 0 0) using scanning tunneling microscopy and X-ray photoelectron spectroscopy. We found that step edges on the Si(1 0 0) surface are gradually roughened due to the formation of Ce silicide as a function of substrate temperature. Unlike the Si(1 1 1) surface, however, terrace etching also occurs in addition to step roughening at 500 °C. Moreover, we found that Si(1 0 0) dimers are released and formed dimer vacancy lines because bulk diffusion of Ce silicide into Si(1 0 0) surface occurs the defect-induced strain at higher temperature (∼600 °C).     

Dynamics of copper atoms on Si(1 1 1)-7 × 7 surfaces

This study investigated the dynamics of copper atoms adsorbed on Si(1 1 1)-7 × 7 surfaces between 300 K and 623 K using a variable-temperature scanning tunneling microscope (STM). The diffusion behavior of copper clusters containing up to ∼6 atoms into a particular half unit cell of the 7 × 7 reconstructed Si(1 1 1) surface was considered. The movements and the formation of copper clusters were tracked in detail. The activation energies and pre-exponential factors for various diffusion paths were estimated. Finally, the Cu-etching-Si process and the quasi-5 × 5 incommensurated phase of Cu/Si islands were discussed.     

Spectroscopic and microscopic investigations of organic ultrathin films: Correlation between geometrical structures and unoccupied electronic states

In this review, we summarize recent progress in experimental approaches to the investigation of the unoccupied electronic structures of organic ultrathin films, based on a combination of spectroscopic and microscopic techniques. At the molecule/substrate interface, electronic structures are greatly affected by the geometrical structures of adsorbed molecules. In addition, a delicate balance between substrate-molecule and intermolecular interactions plays an important role in the formation of complex polymorphism. In this context, we have clarified the correlation between geometric and electronic structures using a combination of two-photon photoemission (2PPE) spectroscopy, low energy electron diffraction (LEED) and scanning tunneling microscopy (STM). Organic ultrathin films of metal phthalocyanines and polycyclic aromatic hydrocarbons (naphthalene, rubrene and perylene) on graphite substrates were examined as model systems. Depending on the substrate temperature and coverage, unique morphologies, including well-ordered films, a metastable phase and a two-dimensional gas-like phase, were determined at the molecular level. The data show that variations in molecular orientation have a significant impact on the occupied/unoccupied electronic structures. In addition to static information regarding electronic states, ultrafast electron excitation and relaxation dynamics can be tracked in real time on the femtosecond scale by time-resolved 2PPE spectroscopy. The excited electron dynamics of rubrene films are discussed herein, taking into account structural information, in the presence and absence of an overlap of the wave function with the substrate. Spatial resolution at the molecular level is also obtainable via STM-based local spectroscopy and mapping, which have been utilized to elucidate the spatial extent of unoccupied orbitals in real space. Visible photon emissions from the unoccupied states of perylene monolayer films were observed using 2PPE, representing a characteristic deexcitation process from electronically excited states, depending on the surface structure. These spectroscopic and molecular level microscopic investigations provide fundamental insights into the electronic properties of organic/substrate interfaces.     

大面阵CMOS实时同步成像及显示系统的设计

为了能够实时成像和同步显示,设计了一种结构简单、携带方便的大面阵CMOS实时成像及显示系统,采用EPF10K50完成了MT9M413C36STM图像生成时序和SXGA显示时序及数据输出的多路转换设计.图像传感器的数据输出转换为两路,一路数据输出给处理电路进行图像实时处理;另一路经ADV7127视频数模变换后输出,可以连接SXGA形式的显示器同步显示图像.实验设计了相关硬件电路,并用VHDL语言编写了驱动程序,在Quartus 8.0的开发环境下,进行了调试.结果表明,该系统可以在1280×1024 @ 60Hz逐行扫描模式下稳定地工作.     

STM spectroscopy on superconducting FeSe1−xTex single crystals at 300 mK

We report cryogenic scanning tunneling spectroscopy measurements on single crystals of superconducting FeSe_1−xTe_x, at doping levels of x=0.5 and 0.7, with critical temperatures . Atomically resolved topographic images were obtained, showing large-scale density-of-state clustering which appears to have no periodicity and to vary with the doping. Conductance spectra taken at 300 mK showed a generally asymmetric V-shaped background, along with a sharp dip structure within . These spectra appeared to vary over ∼nm length scale, and not correlated with the topography. The overall spectral evolution versus temperature is consistent with the dip structure arising from a superconducting energy gap which closes above T_c, and with the spectral background having a non-superconducting origin. The persistence of finite zero-bias conductance down to 300 mK, well below T_c, indicates the presence of low-energy quasiparticles on parts of the Fermi surface. We discuss our data in light of some other recent spectroscopic measurements of FeSe_1−xTe_x, and in terms of its characteristic band structure.     

K~+-核散射研究进展

本文简要回顾了K+ 核散射实验和理论方面近几年的研究进展。我们通过把介质中的K+ 核子相互作用与介质中的夸克凝聚联系起来 ,计算了K+ 核相互作用的非传统机制的贡献。结果表明核密度相关的介质内夸克凝聚可以解释K+ 核散射中的非传统介质效应。     

基于STM32的建筑物接地电阻检测仪的研制

针对目前建筑物接地电阻检测装置存在的缺陷,提出一种基于STM32的建筑物接地电阻检测的系统方案。该方案根据三极补偿原理,采用嵌入式系统控制的主从机软硬件实现接地电阻的精确测量。检测系统包括交流合成、信号采集和数据处理三部分。检测系统由STM32控制产生频率精度高、波形稳定的交流电流注入接地网,对地网中的电压电流信号经带通滤波、差分放大、同步AD转换、FFT处理得到精确地接地电阻值。本检测系统能够提高检测精度以及检测效率,实现检测工作的智能化。     

基于GPS/LBS双模定位人体监护系统的研究

据报道每年中国丢失的儿童、老人、智障患者共有80多万,只有极少数可以被安全找回,再者当今社会经常出现老年人摔倒在地而无人搀扶的情况。为解决此类问题,本文设计了一款基于GPS/LBSS的人体定位监护系统。该系统以ARMSCortex-M3S系列的STM32F103ZE为核心处理器,结合GPS卫星定位模块、无线通信模块、三轴加速度计和三轴陀螺仪以及在VC++平台开发的GIS上位机构成监护系统。该监护系统可根据用户的需求实现实时定位、紧急求救、跌倒检测、电子围栏等功能。定位模式采用GPS/LBS双模式定位,提高定位精度;通信方式采取GSM/GPRS双通信模式,无通信盲区,数据传输稳定。     

Construction of two-dimensional (2D) H-bonded supramolecular nanostructures studied by STM

In this review,a group of two-dimensional（2D） hydrogen-bonded supramolecular networks developed in our laboratory are discussed.Our attention is mainly focused on:（1） recognition of Fe³⁺ through twocomponent molecular networks;（2） site-selective fabrication of 2D fullerene arrays;and（3） fabrication of the nanoporous structure regulated by photoisomerization reaction process.It is envisioned that special supramolecular nanostructures,through H-bonding interactions,can be constructed or reconstructed to be further investigated toward the research of multi-component systems,molecule recognition,single molecular switches,and host-guest supramolecular chemistry.     

Monolayer MoS2 of high mobility grown on SiO2 substrate by two-step chemical vapor deposition

We report a novel two-step ambient pressure chemical vapor deposition (CVD) pathway to grow high-quality MoS₂ monolayer on the SiO₂ substrate with large crystal size up to 110 μm. The large specific surface area of the pre-synthesized MoO₃ flakes on the mica substrate compared to MoO₃ powder could dramatically reduce the consumption of the Mo source. The electronic information inferred from the four-probe scanning tunneling microscope (4P-STM) image explains the threshold voltage variations and the n-type behavior observed in the two-terminal transport measurements. Furthermore, the direct van der Pauw transport also confirms its relatively high carrier mobility. Our study provides a reliable method to synthesize high-quality MoS₂ monolayer, which is confirmed by the direct 4P-STM measurement results. Such methodology is a key step toward the large-scale growth of transition metal dichalcogenides (TMDs) on the SiO₂ substrate and is essential to further development of the TMDs-related integrated devices.