Progress and development in multiple-probe scanning probe microscopes

Abstract

Scanning probe microscopes (SPM) is one of the important tools for micro/nano-scale morphological characterization, physical property measurement and micro/nano operation. However, the traditional SPM has only a single probe and its function is limited. The emergence of multiple-probe scanning probe microscopes (MP-SPM) greatly expands the application of SPM. Characterizing the electrical transport properties of materials is very important for materials and microelectronics, because it can effectively guide synthetization of high-quality materials and fabrication of high-performance devices. Traditionally, directly measuring the conductivity of nanomaterials is performed using the nanofabricated electrodes connected to the nanomaterial of interest and the monolithic micro-four-point probes. However, photoresist and organic solvents may be left on the surface of the nanomaterial during nanofabrication, which will affect the intrinsic measurement of electrical transport properties. As for the monolithic micro-four-point probes, probe spacing is quite large due to the limitation of the manufacturing process and it will not change any more once they have been manufactured, which limits its flexibility. MP-SPMs multiple probes can act as measuring electrodes with precise localization, and the probe-sample distance can be controlled precisely, providing a means of flexible and non-destructive detection of micro/nanoscale electrical transport properties of samples. Micro/nano-manipulation systems help to manufacture microelectronic and photonic devices, renewable energy apparatus and biomedical diagnosis chip, etc. Typical micro/nano-manipulation systems are established based on optical tweezer, magnetic tweezer, scanning electron microscopy (SEM) and SPM. However, they all have limitations. Optical tweezer may damage the sample due to the continuously irradiated lasers. Magnetic tweezer has a poor ability to control the object quantificationally, and low resolution. The system based on SEM is restricted to a vacuum working environment. On the surface of the sample, traditional single-probe SPM can perform nano-manipulation, such as push and pull, but it is limited to two-dimensional space, and three-dimensional manipulation might be a great challenge. In addition, due to the lack of real-time visual feedback during the manipulation process, it always works at a time-consuming mode, such as scanning-manipulating-scanning. Although some researchers have designed augmented reality, local scanning and other methods to improve the efficiency of manipulation, the efficiency of manipulation is still low due to the serial procedure of single probe SPM. MP-SPM have been developed to provide multiple probes which can be controlled independently, and achieve complex nano-manipulation by cooperation among the probes. Furthermore, MP-SPM can image with a certain probe; and the imaging results, serving as priori/feedback information, can guide other probes manipulation, thereby it improves the efficiency and accuracy of micro/nano-manipulation. In this paper, the basic structure of MP-SPM, including the structure of multiple-probe scanning tunneling microscopy and multiple-probe atomic force microscopy, is presented. Furthermore, we also introduce the methods to decrease the distance between the probes and calibrate the multiple probes position and the principle of measuring the resistivity of materials using multiple-probe technology. Then we summarize the recent application advances of the measurement of electrical transport properties, the micro/nano-manipulation, the parallel imaging/ manipulation, and the mechanical properties at the micro/nano scale etc. Finally, we discuss the frontier development, the opportunities as well as the challenges of MP-SPM.