In-situ TEM Observation of Formation-Retraction-Fracture Experiment of Liquid-Like Silicon Nanocontact
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In-situ TEM Observation of Formation-Retraction-Fracture Experiment of Liquid-Like Silicon Nanocontact Tadashi Ishida1, Kuniyuki Kakushima1,2 and Hiroyuki Fujita1 1 Center for International Research on Micronano Mechatronics, Institute of Industrial Science, University of Tokyo, 4-6-1 Komaba, Meguro, Tokyo, 153-8505, JAPAN. 2 Tokyo Institute of Technology, 4259 Nagatsuda, Midori, Yokohama, Kanagawa, 226-8502, JAPAN. ABSTRACT We have examined the change of mechanical characteristics of silicon nanocontacts with and without the pre-treatment by flowing current through the contact. The silicon nanocontact formed between silicon tips by a mechanical contact was quickly deformed during its tensile test under a transmission electron microscope, after applying over 100 μA at a high bias voltage around 15 V between tips for a short duration. In the tensile experiment, the diameter of the nanocontact easily decreased from the initial diameter of 98 nm to 30 nm and the length increased from 11 nm to 66 nm. At 30 nm in diameter, it was suddenly fractured without further elongation and became round tips with smooth surfaces. According to the close observation, the silicon nanocontact seemed amorphous. In the retraction process of the silicon nanocontact, steps moved along the surface from the neck of the nanocontact to the tip side at the speed of 7.0 nm/s. Nano-scaled round step propagations were repeated from the neck to the tip. The step propagation caused the fast thinning of the nanocontact. On the other hand, the silicon nanocontact formed at 1 V in bias voltage was gradually thinned from 42.5 nm to 1.6 nm in diameter and elongated from 2.9 nm to 61.9 nm in length. From the comparison of silicon nanocontacts with and without the pre-treatment, the silicon nanocontact after flowing substantial current showed quick deformation and had different mechanical characteristics from the silicon nanocontact without the pre-treatment. INTRODUCTION Silicon is one of the most common materials for micro/nano devices [1,2]. It is widely used not only in very large scale integrated (VLSI) devices but also in micro electro mechanical systems (MEMS). The dimensions of the devices are minimizing to have better properties [3]. It is important to measure the electronic and mechanical properties of silicon at the nano scale because the properties are expected to be very different in such a small scale from ordinary scales. Many researchers have studied the electronic and mechanical properties of a silicon nanowire and a nanocontact for the further development of nano devices [4,5]. In the study on the electric and mechanical properties of nano structures, experiment with in-situ observation is favorable because the properties of nano structures are sensitively changed by their shapes [6]. Thus, in-situ observation was performed by a transmission electron microscope (TEM) with a help of small actuators, such as a piezoelectric actuator [7,8], a polymer membrane actuator driven by charge-up [9] and a MEMS actuator [10]. These equipments could ac
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