High temporal resolution electrical characterization technology of single-molecule devices

Abstract

<p indent=0mm>Single-molecule electronics is a cross-discipline which aims at employing the individual molecule as the functional element for further miniaturization of the silicon-based microelectronics, and also focuses on the physical and chemical phenomena at single-molecule level. With the development of the single-molecule electronics, numerous novel physical and chemical effects such as Kondo physics, superconductivity and chemical reactions catalyzed by local strong electric fields, and single-molecule electronic devices including filed-effect transistors, diodes, and photo-switches have been widely explored. However, most of the abovementioned investigations are implemented at the millisecond level owing to the low temporal resolution of the measurement instrument, which makes it difficult to monitor the reaction events at faster time scales as well as meet the requirement of the high operating speed of the single-molecule devices. As a result, more attentions have been paid to develop the high temporal resolution electrical characterization techniques. In conventional single-molecule electrical measurement techniques, there is a big challenge that the extremely weak current signal through the single-molecule junction puts higher demands on the current amplification system of the instrument. However, the response speed of such amplifying circuits is relatively low, which limits the temporal resolution for single-molecule electrical measurements. In order to break through the limitation of temporal resolution, much efforts have been made in recent years. On the one hand, the low response speed caused by DC circuits can be improved through increasing the response speed of the current amplifying circuits. On the other hand, AC signal provides a promising approach to improve the temporal resolution, considering that the AC signal has already proven its application potential in the study of other micro-scale high-speed processes. This method requires the addition of AC signal measurement equipment in the circuit, including AC-DC separation circuits, RF amplifiers and lock-in amplifiers, etc., in addition, how to conduct effective data analysis is also a challenge worth considering. In this article, we will give a comprehensive review on the high temporal resolution electrical characterization techniques in the field of single-molecule electronics. This review will describe the challenges, developments, and applications of high temporal resolution electrical characterization techniques. We will briefly explain the significance of the research on the high temporal resolution electrical characterization techniques in the first part, the second part will describe the technical bottleneck of conventional single-molecule electrical measurement techniques, the third part will focus on the applications of the high temporal resolution electrical characterization techniques, and we will draw some expectations and conclusions in the fourth part. Although the high temporal resolution electrical characterization technology of single-molecule devices is still staying at the primary stage for its high requirements for circuit technology and measurement equipment, but this characterization technology can provide us with effective means to study higher-speed processes and more essential properties at the single-molecule scale, which includes the rearrangement of atoms, the structural transformation of molecules, and even the charge or energy transfer at the molecule-electrode interface. Those properties are also the guarantee for the manufacture of high-performance single-molecule electronic devices in the future. Therefore, we believe that the high temporal resolution electrical characterization techniques of single-molecule devices is full of development prospects and will be employed widely in the future.