The Effects Of Isotope Effect And Doping Effect On Radiation Resistance Of Monocrystalline Silicon Materials Were Investigated

As the earliest developed semiconductor material,silicon has been widely used in the production of devices for integrated circuits,solar cells,and aerospace due to its mature manufacturing process and good performance.The requirements for devices in terms of service life and operating performance are increasing as science and technology advance,necessitating research into the theory of radiation damage and anti-radiation reinforcing technology for devices in harsh settings.The theory of radiation damage and anti-radiation reinforcement technology have been extensively studied,however there is still room for more research into these topics because anti-radiation reinforcement technologies have their own drawbacks.Based on this,this paper uses molecular dynamics simulations and a first principles approach,respectively,to discuss the effects of isotope effect and doping effect（fourth main group elements）on the radiation resistance of single crystal silicon materials from the number of defects generated,stability,and electrical properties.The task included in this thesis is as follows:1.The difference in the quantity of defects created inside the two isotope systems at energies of 10 ke V and 20 ke V proton irradiation was determined using the molecular dynamics simulation program LAMMPS.With a difference of 14%in stable defect pairs at 10 ke V and 11%at 20 ke V,the number of peak and stable defect pairs produced by the high quality ³⁰Si isotope system was found to be somewhat lower than that of ²⁸Si,demonstrating the higher radiation resistance of³⁰Si compared to ²⁸Si.Combining ab initio molecular dynamics computations allowed us to determine the differences between the isotope systems’binding energies and lattice constants at 300 K temperature.The findings show that the binding energy of ³⁰Si is higher than that of ²⁸Si because of the different numbers of neutrons in each isotope’s nucleus,and that the lattice constant of high-quality isotopes at ambient temperature is lower than that of low-quality isotopes.As a result,the electrons and holes in ³⁰Si are more readily compounded and the electrical conductivity increases.Consequently,adding high-quality isotopes to a system made of single crystal silicon will help to improve the system’s stability,improve device stability,and lengthen in-orbit lifetime.2.The differences in the lattice structure,stability,and electrical properties of the system when the fourth main group elements（C,Ge,Sn,and Pb）are doped into the single-crystal silicon system are discussed using the first-principles software Vasp.It is found that the lattice constants of Ge,Sn,and Pb doped systems increase linearly with the number of doped atoms due to the difference in atomic radii,and the system undergoes a swelling effect,and the degree of increase in lattice constants is Pb>Sn>Ge,while the lattice constants of C doped systems decrease linearly with the number of doped atoms.Secondly,influenced by the atomic radius,Ge atoms are more likely to replace Si atoms than Sn atoms as well as C and Pb atoms,and the trend of defect formation energy with increasing doping concentration shows Pb>C>Sn>Ge,which means that the high concentration doping system is less likely to be replaced by doping elements and less likely to be synthesized in the process.Also the phonon spectra in different doping cases have no false frequencies,which proves that our simulated system satisfies the mechanical stability.In terms of electrical properties,we found that after the doping of the fourth main group elements,the valence band top position is basically unchanged and the conduction band bottom position gradually moves toward the Fermi energy level,while the s and p orbital contributions of the doped C,Ge,Sn,and Pb atoms are also gradually enhanced from the density of states diagram,leading to the energy band contraction of the doped system,and the band gap continues to decrease with the increase of the doping concentration;changes in bandgap characteristics of some conductors during the increase of doping concentration,C doped material from indirect band gap to become metal-like properties,Ge doping has been the indirect band gap semiconductor,Sn,Pb doping system from the indirect band gap to direct band gap;from the number of energy bands and charge difference density overall,different fourth main group dopant element pairs in the system can increase the electron transition in the material,four elements doping the effect on the electrical properties of the material is C>Pb>Sn>Ge.