高阻抗前置放大器的设计与研制

本前置放大器采用超高速缓冲放大器ＬＨ００３３,并将半导体探测器与前置放大器同时屏蔽,克服了传统放大器体积大,噪声强,易受环境因素干扰等缺点。放大器工作可靠,灵敏度高,适合于各类在电磁环境恶劣下极弱小信号的测量。     

低噪声运放前置放大器的实用设计

根据噪声理论阐述了低噪声运放前置放大器的一般实用设计方法,以及利用Ｅｎ～Ｒｓ和Ｅｎ～ｆ曲线选择和使用低噪声运放的正确方法。     

用于纳米计量的双元扫描隧道显微镜

研制了用于纳米计量的双元扫描隧道显微镜 ,介绍了双元扫描隧道显微镜的原理和仪器系统 ,利用该系统对原子晶格图象进行扫描 ,验证了纳米计量的可行性 ,给出了部分被测样品的纳米计量结果     

生物电前置放大器研究与设计

介绍一种由高性能仪表放大器AD623组成的生物电前置放大器,分析了生物电前置放大器的性能,并通过实验证明该设计的合理性.采用运放单电源供电电路,实现成本低廉,结构简单,性能优越的设计,可广泛应用于低功耗医疗仪器设备.     

高性能肌电检测前置放大器的设计

介绍了一种为消除50Hz干扰而设计的肌电(EMG)前置放大器，通过对前置放大器采取电磁屏蔽处理、DC-DC隔离变换器供电和浮地共模自举等措施。获得了满意的抗50Hz干扰性能。     

CMOS光接收机前置放大器设计

利用CMOS工艺设计一种用于SDHSTM-4速率级（622Mbit／s）光接收机的前置放大器。采用商用SmartSpice电路仿真软件和CSMC-HJ0．6μm工艺参数对该电路进行仿真。仿真结果表明：在5V电源电压下，该电路中频增益为79dBΩ，3dB带宽为560MHz，可稳定工作在622Mbit／s的速率上。     

开放式多功能扫描探针显微镜系统

开放式多功能扫描探针显微镜、集成扫描隧道显微镜、原子力显微镜、横向力显微镜和静电力显微镜．具有接触、半接触和非接触工作模式，可进行作用力、电流、电位、光能量等参数的高度局域综合测量,具有极高的开放性和可扩展性，支持用户进行二次开发。     

与光学显微镜结合的扫描隧道显微镜

研制了一种与光学显微镜结合的扫描隧道显微镜。在CCD摄家机监视下，利用XY冲击式样品台，可将针尖移动到10×10mm2样品的任一特定区域扫描。仪器具有原子（A）量级分辨率，最大扫描范围可达2×2μm2。文中给出了本仪器获得的一些样品图像结果。     

扫描隧道显微镜和原子力显微镜

介绍了扫描隧道显微镜(STM)和原子力显微镜(AFM)的原理和目前情况。     

四极质谱检测中复合放大器的低噪声高带宽设计

四极质谱峰信号是10-11A到10-6A级的微弱电流,并且快速变化,所以在大动态范围内实现低噪声和高带宽是设计关键。设计一种开环增益(ac)可调整的同相输入复合跨阻抗放大器,分析ac对信号和噪声的作用。在较低放大倍率时,改变ac后同相输入复合放大器会降低自身产生的噪声,实现低噪声;在较高放大倍率时,改变ac后同相输入复合放大器能扩展被极高阻值的反馈电阻和寄生电容降低的信号带宽。实验结果表明：与反相输入复合放大器相比,同相输入复合放大器在106-107V/A放大时能降低5-30%噪声,在108V/A放大时扩展带宽1.8倍并提高10-15%质谱峰强度,提高了质谱峰的信噪比。     

Effect of fabrication process parameters on the apex‐radius of STM tungsten nanotip

Scanning tunneling microscope (STM) has found a wide application in nanoscience and nanotechnology. This microscope uses an ultra‐sharp metallic tip for image acquisition. Resolution of STM images depends largely on the radius of the tip apex; the smaller the radius the higher the resolution. In the present research, an experimental set‐up was designed and implemented for fabrication of STM tungsten nanotip using electrochemical‐etching method with the aim of optimization of nanotip fabrication process parameters by using Taguchi method. These parameters are electrolyte concentration, immersion length of the tungsten wire, inner diameter of the cathode tube, and the process voltage. It was found that the optimum level of the process parameters for gaining minimum radius of the nanotip apex is electrolyte concentration of 2 M/lit, wire immersion length of 4 mm, cathode tube inner diameter of 55 mm, and voltage of 3.5 V within the range of experiments. By setting the process parameters on the optimum level, the radius of the nanotip apex was decreased by five times in comparison to the mean value of the experimental results. The radius of the nanotip apex was improved down to about 10 nm under the optimum conditions. SCANNING 31: 65–74, 2009. © 2009 Wiley Periodicals, Inc.     

Fractal characterization by frequency analysis: III. Effect of noise

The effect of noise in the fractal characterization by frequency analysis of surface images obtained by scanning tunnelling microscopy (STM), atomic force microscopy (AFM) or profilometry has been studied. The origin of noise and its relationship to the signal is discussed. A procedure to simulate noisy images is presented. From the study it is concluded that the method usually used to characterize noise in STM is not valid and it is shown that fractal characterization of surfaces when noise is present by traditional frequency analysis methods is not possible. A new method to perform both the noise characterization and the fractal characterization of surfaces when noise is present is proposed.     

Bridging the gap between conventional and video-speed scanning probe microscopes

A major disadvantage of scanning probe microscopy is the slow speed of image acquisition, typically less than one image per minute. This paper describes three techniques that can be used to increase the speed of a conventional scanning probe microscope by greater than one hundred times. This is achieved by the combination of high-speed vertical positioning, sinusoidal scanning, and high-speed image acquisition. These techniques are simple, low-cost, and can be applied to many conventional microscopes without significant modification. Experimental results demonstrate an increased scan rate from 1 to 200 Hz. This reduces the acquisition time for a 200×200 resolution image from 3 min to 1 s.     

原子力显微技术在生命科学中的应用概况

从原子力显微技术自发明以来应用于生命科学领域的文章量来概述其应用和发展情况；同时，分成生物大分子、超分子聚集体和细胞三类，总结了原子力显微技术应用于生命科学的大部分研究对象，并简单介绍了其应用的发展规律。     

Photon scanning tunneling microscope,now and in the future

The concept of photon tunneling and the principle of the photon scanning tunneling microscope (PSTM) are described. The history of the PSTM and its development in China are reviewed. The principal problem in the recent development of the PSTM, together with its solution, is discussed. The distinguishing features and the future of the PSTM are described.     

扫描隧道显微镜精密工作台及其控制技术研究

针对扫描隧道显微镜工作台高精度控制的需求，设计了一种基于神经网络理论的控制系统，其微位移工作台由压电陶瓷驱动器和柔性铰链机构组成。在对驱动器结构进行分析的基础上，建立了工作台的数学模型。以三层神经网络自学习PID控制器代替常规PID控制器，实现了样本的在线采集和优化，有效地克服了神经网络控制器需要离线训练的缺点；采用BP算法对神经网络进行在线训练，增强了系统的实时控制性能。实验结果表明，10μm下的过渡时间从3．25s缩短到1．6s，稳态误差从2．78％减小到1．39％。     

Integration of a high‐NA light microscope in a scanning electron microscope

We present an integrated light‐electron microscope in which an inverted high‐NA objective lens is positioned inside a scanning electron microscope (SEM). The SEM objective lens and the light objective lens have a common axis and focal plane, allowing high‐resolution optical microscopy and scanning electron microscopy on the same area of a sample simultaneously. Components for light illumination and detection can be mounted outside the vacuum, enabling flexibility in the construction of the light microscope. The light objective lens can be positioned underneath the SEM objective lens during operation for sub‐10 μm alignment of the fields of view of the light and electron microscopes. We demonstrate in situ epifluorescence microscopy in the SEM with a numerical aperture of 1.4 using vacuum‐compatible immersion oil. For a 40‐nm‐diameter fluorescent polymer nanoparticle, an intensity profile with a FWHM of 380 nm is measured whereas the SEM performance is uncompromised. The integrated instrument may offer new possibilities for correlative light and electron microscopy in the life sciences as well as in physics and chemistry.     

A new method of scanning tunneling spectroscopy for study of the energy structure of semiconductors and free electron gas in metals

In this study, anew method for the scanning tunneling spectroscopy (STS) of direct and indirect gap semiconductors and free electron gas in metals is proposed. Band structures of Si, porous Si, and Ge were studied. The tunneling current-voltage characteristics of Si and porous Si surfaces were measured over different voltage intervals from tens of mV to 20 V under incident light from an Xe lamp and those of a Ge surface in the dark. The correlation between the shapes of the I-V curves and band structure of the materials was calculated. It was found that the curves are linear if measured in the voltage range V₀ E_g/(2e) and nonlinear when V₀ α E_g/(2e) (in the measurements the applied voltage was changed from -V₀ to V₀). The method was used for the observation of a new effect of tunneling of free electron gas having thermal energies from a metal tip to a band gap state of the semiconductor. The energy spectrum of free electron gas was measured.