# Low Temperature RF-Plasma Initiated Rapid and Highly Ordered Fracture on Ag Nanowires
## 1 Introduction  
The arrangements and microstructure are intrinsic properties of materials, especially for metal nano-materials. Recently, ordered metal particle-chains (such as Ag, Au, Cu) which exhibit unique optical properties are widely applied in plasmon waveguides, colour filters, and single molecular devices, etc [1, 2, 3]. A traditional strategy based on Rayleigh instability has been developed to fabricate one-dimensional particle-chains from their nanowires [4, 5, 6]. Note that, the liquid state of nanowires is the precondition of Rayleigh instability [7], and high temperature is generally required to melt these materials. For example, ordered conversion only occurs with high temperature (for Cu 600 \({}^{\circ}\)C, Au 500 \({}^{\circ}\)C), and a long-time (about 4 to 6 h) [8, 9], and lead to severely evaporation due to the vacuum or inert gas protection at low pressure. Meanwhile, low temperature (about 0.2 melting points (example: melting point of Ag 961.78 \({}^{\circ}\)C, 0.2 x 961.78 \({}^{\circ}\)C = 192.356 \({}^{\circ}\)C) for grain growth) surface melting induced Rayleigh instability generally causes insufficient or even random fractures of metal nanowires [10]. The high temperature and long-time needs will no doubt blur the application of Rayleigh instability in the fabrication of ordered metal particle-chains.  
Low temperature RF (radio frequency) plasma with highly energetic ions and self-bias properties, can lead to uniform bombarding on material surfaces [11]. The temperature of RF plasma induced structure modifications, such as the welding of nanowires or nanoflakes into hollow structures, is much lower than that based on heating [12]. Generally, plasma treating exerted on nanomaterials, such as carbon nanotubes [13], NiCoP nanoflakes [14], Co\({}_{3}\)O\({}_{4}\) nanowire arrays [12] mainly exhibits surface roughness increment or surface microstructure deformation, and this is because the plasmabombarding directly offers kinetic energy for the atoms of material surfaces. This phenomenon inspires us that high diffusion capacity of Ag atoms on Ag nanowires surfaces can be obtained by RF plasma treatment. Related to the Rayleigh instability, similarly, ordered metal particle-chains should be obtained from metal nanowires with temperature below 100 \({}^{\circ}\)C.  
Herein, we adopted Ag nanowires (AgNWs) as example to realize the large-scale fabrication of the ordered particle-chains. The scale of AgNPs films on silicon substrate are about 1-3 cm\({}^{2}\). To show the universality of this method, AgNPs with various diameters and aggregations were chosen and then treated by plasma. We found that the dispersed AgNPs with various diameters were nearly completely converted into highly ordered particle-chains deposited on Si substrates on a macro scale with only 3 to 5 min. Additionally, the temperature of the Si substrates was no more than 100 \({}^{\circ}\)C during the process. Moreover, similar to the high temperature heat treatment, the periodicity of these particle-chains shows strong dependency on the diameters of AgNPs as expected by Rayleigh instability. Meanwhile, the aperiodicity of particle-chains has been observed as the aggregation of AgNPs begins. Furthermore, wire-wire welding has also been found on AgNPs with the increment of the aggregation.