Analysis Of Thermal Stability And Tensile Mechanical Properties Of Silicon Nanotubes

Silicon nanotubes appear to be compatible with the silicon-basedmicroelectronics and might become the most versatile building materials fornanoelectronic devices. Especially branched silicon nanotubes, they can implementmore complex functions in nano-devices due to their unique structure. It is necessaryto investigate the performance of silicon nanotubes before they play a significantpotential role in the practical application. Based on Tersoff-potential moleculardynamics method, the thermal stability and tensile mechanical properties of sp2hybridization silicon nanotubes (SiNTs), branched silicon nanotubes(BSiNTs), sp3hybridization silicon nanopipes (SiNPs), branched silicon nanopipes (BSiNPs) andsilicon nanowires (SiNWs) were analyzed. For comparison, the thermal stability andthe tensile mechanical properties of carbon nanotubes(CNTs) and bulk silicon werealso investigated. Main conclusions are as follows.(1) The thermal stability of SiNTs and BSiNTs were analyzed. First of all, thethermal stability of (15,15) SiNTs,(24,4) SiNTs and (26,0) SiNTs with a diameter ofabout3.2nm were estimated. The numerical results showed that the thermal stabilityof three types of SiNTs are independent on their chirality. Secondly, the thermalstability of (9,9) SiNTs,(12,12) SiNTs and (15,15) SiNTs with a different diameterwere analyzed. It can be found that the thermal stability of three types of SiNTs aredepend on the SiNTs diameter. The thermal stability of SiNTs is better with theincreasing of diameter. At last, the thermal stability of (15,15)SiNTs and (15,15)BSiNTis were analysed. It can be found that the thermal stability of (15,15) BSiNTsis independent on the junction. And we found that the structure of all the SiNTs andBSiNTs will be transformd into the non-crystalline structure during the process ofheating. The results are not similar to the thermal stability of CNTs with the samestructure.(2) The thermal stability of SiNPs、BSiNPs and SiNWs with the diameter ofabout3.2nm were analyzed. It can be found that thermal stability of SiNPs、BSiNPsare lower than SiNWs. And we find that the structure of SiNPs and BSiNPs transforminto non-crystalline structure during the process of heating. A minority of the structureof SiNWs transform into non-crystalline structure during the process of heating, whilethe majority of the structure of SiNWs don’t transforme berore they melt fracture.The results are not similar with thermal stability of bulk silicon With the same structure.(3) The tensile mechanical properties of SiNTs and BSiNTs were analyzed. Firstof all, the tensile mechanical properties of (15,15) SiNTs,(24,4) SiNTs and (26,0)SiNTs with a diameter of about3.2nm were analyzed, It can be found that the tensilestrength and young’s modulus of three types of SiNTs are very similar. Secondly, thetensile mechanical properties of (15,15)SiNTs and (15,15)BSiNTs were analyzed, Itcan be found that the tensile strength and young’s modulus of (15,15)SiNTs is greaterthan (15,15)BSiNTs. Because of the special structure in the junction of (15,15)BSiNTs, the junction of (15,15)BSiNTs was destroyed in energy minimizationprocess, which lead to the tensile strength and young’s modulus decrease during thetensile process. In addition, the structure of SiNTs and BSiNTs gradually transform ininitial tension stage, nanotubes neck down to form atomic chain during the tensileprocess, and eventually fracture. Finally, BSiNTs fractured due to the destruction ofthe junction. The results are not similar to the tensile mechanical properties of CNTswith the same structure.(4) The tensile mechanical properties of SiNPs、BSiNPs and SiNWs with adiameter of about3.2nm were analyzed. We found that there is a elasatic deformationstage in initial tension process. The structure of SiNPs、BSiNPs and the seldom ofSiNWs’structure have transformed when respective strain reached a certain value,most part of the structure of SiNWs don’t transform. The simulation results showedthat the tensile strength and Young’s modulus of SiNWs is greater than the SiNPs,while the SiNPs is greater than BSiNPs. Both of them come into neck down to formgradually atomic chain during the tensile process, and fracture eventually. It is easierfor BSiNPs to fracture at the junction because stress concentration. They have slightlydifference in tensile mechanical properties compare with the same structure of bulksilicon.