Abstract
One-dimensional (1D) nanostructures are extensively used in the design of novel electronic devices, sensors, and energy devices. One of the major challenges faced by the electronics industry is the problem of contact between the 1D nanostructure and electrode, which can limit or even jeopardize device operations. Herein, a universal method that can realize good Ohmic and mechanical contact between an individual 1D nanostructure and a tungsten needle at sub-micron or micron scale is investigated and presented in a scanning electron microscope (SEM) chamber with the synergy of an electron beam and electrical current flowing through the welded joint. The linear I‒V curves of five types of individual 1D nanostructures, characterized by in-situ electrical measurements, demonstrate that most of them demonstrate good Ohmic contact with the tungsten needle, and the results of in-situ tensile measurements demonstrate that the welded joints possess excellent mechanical performance. By simulation analysis using the finite element method, it is proved that the local heating effect, which is mainly produced by the electrical current flowing through the welded joints during the welding process, is the key factor in achieving good Ohmic contact.
Highlights
In recent decades, one-dimensional (1D) nanostructures have become the subject of extensive research, owing to their unique and excellent electrical, optical, thermal, mechanical, and magnetic properties
The temperature distribution of the individual 1D nanostructure under the synergy of the electron beam and electrical current flowing through the welded joints was calculated using the Comsol Multiphysics package
The heating energy of the e-beam was assumed to be a disk with a Gaussian distribution on the welded joint in the simulation, whereas most of energy conversion occurred in the tungsten needle. This means that the temperature at the welded joint in the actual welding process was lower than the value of simulation. These results show that the local heating effect generated by the e-beam was not sufficient to establish a good Ohmic contact at the welding position, and the Joule heat generated by the electrical current flowing through the nanowires and the welded joint was the main heating source of the local heating effect
Summary
One-dimensional (1D) nanostructures have become the subject of extensive research, owing to their unique and excellent electrical, optical, thermal, mechanical, and magnetic properties. To utilize the excellent properties of 1D nanostructures in the electronic devices, nanostructure welding technology, which can realize good Ohmic and machinal contact between an 1D nanostructure and an electrode, has been one of the most important processes in the application of 1D nanostructures. By rapid thermal annealing at 600–800 ◦C for 30 s, the contact resistances of carbon nanotube (CNT) devices have been reduced [17]. Dong et al developed a method to reduce contact resistance between CNTs and metal electrodes by local Joule heating [18]. The methods reported above usually require tedious procedures, such as electron-beam (e-beam) lithography, metal deposition, and removal of e-beam resist, which risk contamination of the nanowire surfaces by the photoresist
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