# Low Temperature RF-Plasma Initiated Rapid and Highly Ordered Fracture on Ag Nanowires
## 3 Results and Discussion
Even after 6 h, only random and insufficient coarsening on AgNWs can be observed, as shown in Figure 2c. As the temperature increases to 450 \({}^{\circ}\)C, the coarsening grade of AgNWs is much higher than that under 200 \({}^{\circ}\)C, as shown Figure 2d. However, the periodicity of formed Ag particle-chains is still relatively low (a little better than that under 200 \({}^{\circ}\)C) under 450 \({}^{\circ}\)C with 6 h. In contrast to RF plasma treatment, the conversion of AgNPs is insufficient and uneven with temperature lower than 0.5\(T_{m}\) by heat treatment. Based on the above results, RF plasma treatment shows significant differences with that of traditional thermal induced coarsening due to its low temperature need, rapid and highly ordered conversion on AgNWs. A schematic illustration has been presented to explicate the RF plasma treatment induced uniform conversion of AgNPs, as shown in Figure 3a. When the Ar\({}^{+}\) plasma bombarding is exerted on AgNPs, the kinetic energy of Ar\({}^{+}\) is passed to the atoms on AgNWs surfaces and then to the delivered inside. Such plasma bombarding will greatly enhance the diffusing tendency of Ag atoms on AgNPs [22]. Similar conversion of AgNPs have also been found in AgNPs networks by laser-driven and electro-temperature driven Rayleigh instability at a temperature above 360 \({}^{\circ}\)C [23; 24]. Obviously, the temperature needed for RF plasma treatment is much lower. The initial surface roughness of Ag nanowire is rarely low and has little effects on the instability of the nanowires. Note that the initial surface roughness on Ag nanowire surface (0 s) observed in Figure 3b is broken carbon film of copper mesh. TEM results show that significant surface fluctuation occurs with only 30 s plasma treatment, which proves the faster nonequilibrium diffusion of Ag atoms on AgNPs surfaces by plasma bombarding, as shown in Figure 3b. Following this, rapid surface instability occurs on AgNWs, which leads to the conversion of AgNPs into uniform particle-chains. In this process, the  
Figure 2: (**a**), Morphologies of Ag nanowires with various diameters; (**b**), melting points of Ag nanowires, nanoparticles and hemispheres with diameters ranging from 10 nm to 200 nm; (**c**),(**d**) morphologies of Ag nanowires treated by vacuum heating under 200 \({}^{\circ}\)C and 450 \({}^{\circ}\)C for 6 h.  
diffusion is mainly localized on AgNWs surface, that's why there is little temperature increase on the whole substrate. As shown in Figure 4a, AgPCs with higher periodicity can be obtained through plasma bombarding. The statistical results of centre-to-centre distances between Ag nanoparticles (\(\lambda_{sp}\)), and the average sphere diameters of Ag nanoparticles (\(D\)) have been presented in Figure 4b. Additionally, the diameters of Ag nanoparticles are proportional to the sphere diameters. Apparently, the \(\lambda_{sp}\) shows linear relationship with \(D\), which well accords with the surface diffusion induced Rayleigh instability predicted by [PERSON] [25]. The deviations with Nichols-and-Mullins model can be attributed to the oblate spheroid shaped Ag nanoparticles and pentagonal shaped AgNWs which are different from the perfect cylinders and balls in the theoretical model. The standard deviations of \(\lambda_{sp}\) decrease rapidly from 24.7 % to 1.8 % as the \(D\) decreases from about 1.0 \(\upmu\)m to 0.34 \(\upmu\)m, which is still much smaller than that by high temperature heat treatment. As a result, the plasma treated Ag nanowires are just like isotropic materials with high diffusion abilities, which have rapid and thorough conversion properties to transform into highly ordered particle-chains at a temperature below 100 \({}^{\circ}\)C. Owing to this, these highly ordered particle-chains could be applied as plasmon waveguides to obtain high quality near field optical transmissions. Obvious periodic fracture on AgPCs can be found when AgNPs are overlapped.