Peculiar Atomic Bond Nature in Platinum Monatomic Chains

Abstract

Metal atomic chains have been reported to change their electronic or magnetic properties by slight mechanical stimulus. However, the mechanical response has been veiled because of lack of information on the bond nature. Here, we clarify the bond nature in platinum (Pt) monatomic chains by our in situ transmission electron microscope method. The stiffness is measured with sub-N/m precision by quartz length-extension resonator. The bond stiffnesses at the middle of the chain and at the connection to the base are estimated to be 25 and 23 N/m, respectively, which are higher than the bulk counterpart. Interestingly, the bond length of 0.25 nm is found to be elastically stretched to 0.31 nm, corresponding to a 24% strain. Such peculiar bond nature could be explained by a novel concept of “string tension”. This study is a milestone that will significantly change the way we think about atomic bonds in one-dimension.

Critical shear stress of gold nanocontacts estimated by in situ transmission electron microscopy equipped with a quartz length-extension resonator

“…In addition, the mechanical energy dissipation of the oscillating LER can be measured from the change in the oscillation excitation voltage to keep the LER oscillation amplitude constant. 20) The energy dissipation shows a greater increase due to nonconservative phenomena such as the slip of the NC in plastic deformation. It is noted that, even in elastic deformation, it increases due to internal friction of the NC accompanying heat generation as well as internal friction of the LER, proportionally to the square of the oscillation amplitude.…”

“…For this purpose, we developed an in situ transmission electron microscopy (TEM) holder equipped with a quartz length-extension resonator (LER) as a force sensor [Fig. 1(a), and see our previous reports for details [18][19][20] ]. Thereby the equivalent spring constant of a metal NC can be evaluated from the shift in the resonance frequency of LER by frequency modulation method.…”

Understanding the rheology of nanocontacts

“…Reversibility of yielding is in itself not sufficient to account for that, and some additional element must intervene to make the force jumps at necking and bellying large enough, with accumulation of tensile stress, surprisingly even after compressive bellying. That element, theoretically predicted long ago 12 , 13 and recently demonstrated in Pt nanowires 19 is the intrinsically nonzero tensile force—a string tension between the leads—even for a solid nanojunction. In our simulations, tension indeed appeared systematically in all oscillation-free and oscillating nanocontact simulations, as shown by the positive mean force value in Fig.…”

“…The first important step was to establish a realistic nanojunction shape and inner structure. Both are generally unknown experimentally, and expected to evolve in the course of time 12 , 13 with shape evolution routes which depend experimentally on temperature and formation protocols 4 – 6 , 8 , 9 , 14 , 19 , and theoretically also on the precise form of interatomic interactions 3 , 18 , 20 – 23 . In experimental protocols such as that of ref.…”

Mechanical analysis of gold nanocontacts during stretching using an in-situ transmission electron microscope equipped with a force sensor

“…Figure 1(a) shows the schematic of our developed TEM holder. An LER (3EXW-1073, STATEK) with a resonant frequency ( f 0 ) of 1 MHz and a spring constant (k 0 ) of ∼1.85 × 10 6 N m 28) was glued onto a polyether ether ketone (PEEK) board, fixed at the end of a 3-axis piezo actuator to finely control the position of LER. The LER was oscillated at its resonant frequency by applying a sinusoidal excitation voltage to one electrode of LER, using a phase locked loop (PLL) in an FM controller (OC4, SPECS Zurich GmbH).…”