Atomistic Simulation Of The Electronic Properties Of Silicon/Carbon Nanotubes And The Vibrational Properties Of Silicon Nanowire Resonators

Silicon nanotubes(SiNTs) have been widely used in many fields, such as nano-electronic devices, resonators, field emission display areas, which are similar to carbon nanotubes(CNTs) and silicon nanowires(SiNWs). Therefore, it is of great importance to deeply analyze and study the electronic properties of nanotubes for the future development and application. In addtion, resonators have been widely applied to communications, robotics, industrial process control, computer agriculture and so on. It is also of significance to study the vibrational properties of the resonators. In this paper, the electronic properties of SiNTs/CNTs are simulated and calculated by the first principle of density functional theory. Meanwhile, the molecular dynamics(MD) method is used to analyze vibrational properties of SiNWs. The main contents of this paper are as follows.(1) Based on the density functional theory, the effect of modeling methods on electronic properties of SiNTs/CNTs is discussed. Especially, whether the electronic properties of the non-periodic structure of nanotubes can approach those of the periodic structure is investigated. For the periodic structure of SiNTs/CNTs, with the increase of the repeating units, the value of density of states(DOS) at the Fermi level is greater than zero, so two kinds of nanotubes are metallic. As the value of DOS increases gradually, the metallicity is more and more strong. Compared with CNTs, the metallicity of SiNTs is more strong. Meanwhile, the position of the value of SiNTs at the Fermi level gradually shifts to the trough, so the system is more stable. For the non-periodic structure of SiNTs/CNTs, the value of DOS and highest occupied molecular orbital- lower unoccupied molecular orbital(HOMO-LUMO) energy gap increases with the increase of the length of nanotubes. The value of DOS at the Fermi level is greater than zero, and the value of HOMO-LUMO energy gap is less than zero, so two kinds of nanotubes are also metallic. The values of DOS and HOMO-LUMO energy gap decrease after adding H to dangling bonds of SiNTs/CNTs, implying that the metallicity is weakened. According to the HOMO-LUMO energy gap, for the non-periodic structure of SiNTs, the modeling method of increasing the length of the nanotubes approaches better to the properties of the periodic structure compared with the modeling method of adding H to dangling bonds. The simulation result of CNTs is opposite.(2) The vibrational properties of SiNWs are studied by using the MD method. The effect of different velocity amplitude on various parameters including quality factor Q, frequency as well as amplitude is discussed. The simulated results show that, the magnitude of Q factors increases obviously with the increase of the initial velocity amplitude at a certain temperature. The nonlinear vibration has not been excited when the velocity amplitude equals 0.25?/ps, and the value of frequency about CoM and RMS increases with the increase of velocity amplitude. The value of frequency about external energy is unchanged when the initial velocity amplitude is larger than 1.0?/ps. In addition, the results also show that there is a exponential relationship between the root mean square and the time response, meanwhile, the maximum amplitude during the vibration process is 18 and there is a phase difference between x-deflection and y-deflection.