Mechanism Investigation Of Lattice Damage Induced By Nucleat And Electronic Energy Losses And Their Coupling Effects Under Ion Irradiation

The interaction between ions and solids,including the further irradiation effects,is a relatively fundamental and essential scientific issue in the field of ion irradiation.To clarifying the mechanisms of both microscopic damage and macroscopic property evolution on such important issue,systematic research and theoretical exposition are the basic approach.During an irradiation,the energetic ions will interact with the lattic of the irradiated material and lose its energy in two different ways:nuclear energy loss and electronic energy loss.For nuclear energy loss,the energy transfer between energetic ions and material nuclei which induced by elastic collisions during the irradiation.Meanwhile,the electronic energy loss is induced by the inelastic collisions between energetic ions and electrons of the target materials.Crystal materials is one of the most important part in modern technologies like infrared,laser and new energy,since it can implement the interaction and conversion of different forms of energy such as force,heat,electricity,light,and magnetism.Specific ion irradiation can further enhance the material performance,and various crystal micro-nano structures can also be prepared based on ion beam technology.Besides,crystal material is not only one of the matrix materials for space function devices,but also an important candidate matrix for the structural materials and solidification of nuclear waste in advanced nuclear energy reactors.For the practical applications mentioned above,the damage behavior and evolution induced by ion irradiation determines the operating performance of space electronics,reactor core fuel,and structural materials.To realize the wider application of functional and structural crystal materials in complicated extreme condations,the damage evolution behavior in ion irradiation environment with different energy regions,which is the hotspot and frontier of the research of interaction between ions and solids,as well as applications in space exploration and nuclear energy,should be studied.In this dissertation,the research is mainly focused on the irradiation of functional and structural crystal materials.The ABO3 crystal materials were irradiated by ions in different energy regions to explore the mechanism of lattice damage induced by nuclear and electronic energy losses and their coupling effects under ion irradiation;the crystal optical waveguide structures were prepared by ion irradiation in different energy regions to explore the physical mechanism and optical characteristics of waveguide structures formed by different irradiation conditions.The outline of this dissertation is as follows:LaAlO3 and YA103 crystals were irradiated with 1 MeV Au+and 20 MeV Si3+,respectively,to investigate the damage behaviors induced by low and medium energy ion irradiation.The damage accumulation produced by Au+ irradiation were analyzed utilizing RBS/channeling technique and fitted utilizing classic disorder accumulation model.The obtained damage accumulation curves under low energy Au+irradiation indicate that YAlO3 crystal has higher damage tolerance than LaA103 crystal under low energy ion irradiated conditions.Also,the damage behaviors of LaAlO3 and YAlO3 crystals irradiated with 20 MeV Si3+have been studied through RBS/channeling,HRTEM,prism coupling techniques and iWKB method.Obtained results indicates that the lattice damage induced by 20 MeV Si3+ irradiation should be attributed to the nuclear energy loss.It is worth noting that,our analysis process provides a noteworthy path(prism coupling measurement and subsequent refractive index profile reconstruction)for studying the damage behavior induced by ion irradiation in crystals.Under swift heavy ion irradiation,electronic energy loss is substantial.In addition,once electronic energy loss exceeds a certain threshold,energetic ions can create ion tracks along their trajectories.However,the latent track damage induced by electronic energy loss is not well understood owing to complex thermal parameters involved and ion velocity effect.Formation and evolution mechanisms of track damage induced by electronic energy loss in crystals were comparatively studied using 200 MeV Kr17+,247 MeV Ar12+and 358 MeV Ni19+irradiation.The results of lattice damage characterization confirmed track damage of different morphologies including isolated spherical defects,discontinuous tracks and continuous tracks were formed in irradiated samples.The electronic energy loss corresponding to the formation of spherical defects is used as the threshold for tracks damage production,which is 14.70 keV/nm for 2.30 MeV/u ion irradiation in LaAlO3 crystal and 8.61 keV/nm for 1.01 MeV/u ion irradiation in YAlO3 crystal.Based on the inelastic thermal spike model,the spatiotemporal evolutions of energy deposition and lattice temperature were numerically calculated for ion irradiated crystals.Then,the formation mechanism of track damage of different morphologies is expounded,and the concept of "temperature threshold" describing track damage behavior is proposed.The irradiation effects induced by different ion velocities and electronic energy loss can be attributed to the lattice temperature,which enables a large number of reported damage data under different irradiation conditions to be analyzed and compared,and improves the predictability of the formation and evolution of radiation damage under the electronic energy loss.Based on the inelastic thermal spike model,the corresponding lattice temperature threshold for irradiation damage is 4340 K for LaA103 crystal and 2845 K for YAlO3 crystal.Unlike low energy or high energy ion irradiation alone,materials in an actual irradiated environment may be simultaneously affected by ions in a wider energy region.In this case,the nuclear energy loss process of low energy ion irradiation and the electronic energy loss process of high energy ion irradiation are no longer mutually independent and may be coupled.Development and improvement of research on material radiation effects and related physical mechanisms in complicated ion irradiation environments can provide the necessary theoretical and experimental basis for the development of new anti-irradiation materials and the study of their damage characteristics.At present,few facilities in the world can simultaneously carry out low energy and high energy double-beam ion irradiation experiments.One solution is to use low energy and high energy ion beams successively,so as to study the damage evolution behavior and mechanism of the pre-damaged area generated by nuclear energy loss under electronic energy loss.Based on the scheme,we conducted the following studies:(i)LaAlO3 and YAlO3 crystals were first irradiated with 1 MeV Au+ to produce initial lattice damage,and then,pre-damaged samples were subsequently irradiated with different energetic ions to explore the coupling between nuclear and electronic energy losses and its induced damage evolution behavior.The results of lattice damage characterization confirmed that,compared with the perfect crystals,the enhanced damage production in the pre-damaged LaAlO3 via subsequent 200 MeV Kr17+irradiation,and the morphology of track damage changed from discontinuous to continuous.Similarly,the enhanced damage production in the pre-damaged YAlO3 samples via subsequent 20 MeV Si3+and 358 MeV Ni19+irradiation,and discontinuous tracks were formed in Ni19+-irradiated sample.Based on the inelastic thermal spike model,the spatiotemporal evolutions of energy deposition and lattice temperature were numerically calculated for pre-damaged crystals,and the physical mechanism of increased damage and track topography change in pre-damaged crystals were analyzed.(?)To further explore the coupling between nuclear and electronic energy losses and induced irradiation effects,SrTiO3 samples were first irradiated by 1 MeV Au+ with different fluence to produce initial lattice damage.Subsequently,highly pre-damaged samples were irradiated with 247 MeV Ar12+ 20 MeV Si3+ and 200 MeV Kr17+,and lowly pre-damaged SrTiO3 samples were irradiated with 20 MeV Si3+and 358 MeV Ni19+.The results of lattice damage characterization confirmed that,compared with perfect SrTiO3 crystal,more severe track damage produced in highly pre-damaged SrTiO3 sample,and discontinuous tracks were formed in pre-damaged samples under Ar12+ and Si3+ irradiation,and the morphology of track damage in pre-damaged samples under Kr17+ irradiation changed from discontinuous to continuous.On the contrary,the damage of lowly pre-damaged SrTiO3 samples decreased.Based on the inelastic thermal spike model,the spatiotemporal evolutions of energy deposition and lattice temperature were numerically calculated,and the physical mechanism of different damage evolution behavior in pre-damaged SrTi03 samples were analyzed.The above research results indicate:(?)the coupling between nuclear and electronic energy losses should be specifically divided into competitive and synergistic effects.The related energy deposition density and temperature increment depend on the thermal parameters of the materials,including their thermal conductivity,specific heat coefficient and electron-phonon coupling parameter.According to the solid-state theory,the defects in the crystalline system could scatter phonons and electrons and reduce the mean free path for phonons and electrons,resulting in a decrease in thermal conductivity,and decrease the electron-phonon mean free path,resulting in an increase in the electron-phonon coupling parameter.Therefore,the diffusion of the local excitation energy in the pre-damaged crystal was suppressed.A more intense thermal spike response are evident in the highly pre-damaged sample,and the lattice temperature therefore increases more substantially,leading to more irradiation damage production;a little more intense thermal spike response are evident in the lowly pre-damaged sample,and the lattice temperature limited increases,leading to pre-damage recrystallization.(?)For some single crystals,direct high energy ion irradiation is difficult to induce track damage,which greatly limits the application of ion irradiation technology in the preparation of nanochannels.Thus,pre-damage greatly enhanced the sensitivity of crystal to the effects of electronic energy loss,which could promote track formation,and obtained track morphologies could be effectively modified.The related findings provide provide a novel strategy for related applications such as preparation of nanochannels.As a basic component of integrated photonic devices,optical waveguides have very important applications in modern optical communications and other fields due to their unique performance and high integration.We utilize displacement damage and tracks damage induced by nuclear and electronic energy loss,respectively,precisely control optical characteristics and related positions in the irradiated crystal,and optical waveguides working at different wavebands were successfully prepared:(1)LaAlO3 sample was irradiated with 6 MeV Si3+,and SrTiO3 samples were irradiated with different energetic ions.The optical properties of the irradiated samples were modified and regulated by nuclear energy loss-induced displacement damage,and optical waveguide structures were successfully prepared.Optical measurements and simulations indicate that the formed LaAlO3 optical waveguide structures could effectively support the transmission of visible light,and the formed SrTiO3 waveguides could effectively support the transmission of visible and near-infrared light,respectively.(2)LiTaO3 sample was irradiated with 247 MeV Ar12+,and optical properties were modified and regulated by electronic energy loss-induced track damage,and optical waveguide structures was successfully prepared.Optical measurements and simulations indicate that the formed LiTaO3 optical waveguide structures could effectively support the transmission of near-infrared light.