Fast low-noise transimpedance amplifier for scanning tunneling microscopy and beyond

Abstract

A transimpedance amplifier has been designed for scanning tunneling microscopy (STM). The amplifier features low noise (limited by the Johnson noise of the 1 GΩ feedback resistor at low input current and low frequencies), sufficient bandwidth for most STM applications (50 kHz at 35 pF input capacitance), a large dynamic range (0.1 pA to 50 nA without range switching) as well as a low input voltage offset. The amplifier is also suited for placing its first stage into the cryostat of a low-temperature STM, minimizing the input capacitance and reducing the Johnson noise of the feedback resistor. The amplifier may also find applications for specimen current imaging and electron-beam induced current measurements in scanning electron microscopy, and as a photodiode amplifier with a large dynamic range. This paper also discusses sources of noise including the often neglected effect of non-balanced input impedance of operational amplifiers, and describes how to accurately measure and adjust the frequency response of low-current transimpedance amplifiers.

Direct assessment of the acidity of individual surface hydroxyls

“…The preparation chambers contain standard surface cleaning and heating facilities. The analysis chambers are equipped with a low-temperature STM/AFM (Omicron) head and a Tribus (ScientaOmicron) head, respectively, using qPlus sensors 10 and low-noise amplifiers 31,32 . Tips were electrochemically etched from a 25-μm-thick tungsten wire.…”

A Multitechnique Study of C2H4 Adsorption on Fe3O4(001)

“…The STM data were acquired in a two-vessel UHV chamber consisting of a preparation chamber ( p <10 –10 mbar) and an analysis chamber ( p <2 × 10 –11 mbar). The analysis chamber is equipped with a Tribus STM head (Sigma Surface Science) and a low-noise in-vacuum preamplifier . The STM measurements were conducted in constant current mode with an electrochemically etched W tip.…”

“…The analysis chamber is equipped with a Tribus STM head (Sigma Surface Science) and a low-noise in-vacuum preamplifier. 27 The STM measurements were conducted in constant current mode with an electrochemically etched W tip. The STM images were corrected for distortion and creep of the piezo scanner as described in ref ( 28 ).…”

Low-noise preamplifier for scanning tunneling microscope

“…到。这种前置电流放大器的噪声水平要足够低，能够分辨 pA 量级的隧穿电流变 化 [4] ，同时还应该具有较大的动态范围。近年来基于 STM 探针的原子搬运 [5,6] 及自动化操纵 [7] 发展迅速且引人注目。在对单个原子进行搬运时，隧穿结电阻约 为 50 kΩ-500 kΩ [6] ，对应隧穿电流可达 10 nA-100 nA 量级。自动化原子搬运等 实验操作要求前置电流放大器能够通过计算机程序远程控制进行增益切换。 前置 电流放大器的带宽也是影响 STM 性能的重要因素，由于反馈电阻寄生电容的存 在，GΩ 量级增益的前置电流放大器的带宽通常被限制在几百 Hz 范围。考虑到 压电陶瓷的响应在 10 kHz 量级 [8] ，将电流放大器的带宽优化至对应范围将有助 于提高 STM 系统扫描成像等核心功能的运行速度。 隧穿电流中的散粒噪声的测量能够揭示电子输运过程中的相互作用信息， 为 凝聚态物理关联电子体系的研究提供重要数据和物理基础， 比如量子霍尔系统中 的分数电荷 [9,10] ，超导体中的库伯对 [11,12] 以及量子点接触中的输运特性 [13,14] 等。 利用工作在室温的前置电流放大器直接测量隧穿电流中的散粒噪声无需进行互 相关测量 [13,15,16] 和高频测量 [17,18]…”