多探针扫描探针显微镜研究进展与应用

Progress and development in multiple-probe scanning probe microscopes

扫描探针显微镜(SPM)是微纳尺度形貌表征、物性测量及微纳操作的重要工具之一.传统的SPM只有单一探针,功能单一,多探针扫描探针显微镜(MP-SPM)的出现拓展了SPM的应用.MP-SPM的多个探针可充当精确定位的测量电极,从而提供了一种无损探测样品微纳尺度电学输运性质的方法;也可相当于多只独立活动的"手",相互配合实现复杂的纳米操作;还可以探针成像,成像信息作为其他探针操作的先验/反馈信息,从而提高操作的效率及准确性.本文首先介绍了MP-SPM的基本仪器结构,多探针距离缩小及位置标定方法,以及使用多探针技术测量材料电阻率的原理,接着总结了近年来MP-SPM在样品微纳尺度电学输运性质测量、微纳操作、并行成像与操作以及新型力学性质测量等方面的应用,最后探讨了该技术的前沿发展以及面临的机遇与挑战.

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-SPM's 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 inde- pendently,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.