| Nanostructure is the key to design and study the radiation tolerance materials through enhancing the sink efficiency to absorb the radiation defects.The Cu/Nb immiscible material systems with positive mixing enthalpy were proved to be an excellent irradiation tolerance material.However,the as-deposited Cu/Nb films are often amorphous due to the change of mixing enthalpy to negative,the special interface structure of Cu/Nb films with enhanced radiation resistance could not be maintained in a good manner.In this paper,Cu/Nb nanocomposite thin films with modulation of 8 nm and total thickness of 2 ?m were prepared by deep oscillation magnetron sputtering(DOMS)and pulsed DC magnetron sputtering(PDCMS).The effects of DOMS discharge peak power controlled by different micro pulse duty cycle were studied to analyze the correlation between the composition,microstructure and electrical/mechanical properties of Cu/Nb nanomultilayer composite films.The proton irradiation experiments were further carried out to study the variation of microstructure and electrical/mechanical properties of Cu/Nb nanomultilayer composite films before and after irradiation:1)The results showed that the constant power of Cu target was 1.0 kW,the micropulse on time of Nb target was increased from 8 ?s to 13 ?s,the peak power was increased from 73.4 kW to 115.2 kW,and the Nb content was increased from 34 at.%to 51 at.%.The Cu/Nb thin film was nano multilayer structure with modulation of 8 nm,and a new Cu/Nb diffraction peak was formed between fcc-Cu(111)and bcc-Nb(110)diffraction peaks.With ?on increased,the hardness of Cu/Nb films increased from 7.0 GPa to 7.8 GPa,the residual stress increased from-17.0 MPa to-429.5 MPa,and the resistivity decreased from 80.4 ??*cm to 52.8 ??*cm.2)After 100 keV,3.6×1016 ions/cm2 proton irradiation,the surface segregation of pure Cu films was caused by thermal stress and strong atomic migration ability.The pure Nb film and Cu/Nb film had no obvious change after irradiation due to the high melting point and low migration ability of Nb element.After proton irradiation,the Cu and Nb phases in Cu/Nb films were gradually separated.The two phases of Cu66Nb34 were completely separated,but the nanocomposite structure remained.After irradiation,the hardness and resistivity of the films increased slightly,but they still had excellent electrical/mechanical properties.3)Based on Monte Carlo method,SRIM and SIMTRA software were used to study the particle transport process of DOMS and PDCMS.The sputtering yield of Cu was 1.83 atoms/ion,and that of Nb was 0.31 atoms/ion;The deposition energy of Nb was higher than that of Cu,which was 42 ev-49 eV for Cu and 51.1-58.1 eV for Nb.This was consistent with the experimental results that PDCMS was used to improve the overall deposition rate and DOMS wass used to regulate the energy of deposition particles to prepare crystalline Cu/Nb films.4)Based on Dynamic Monte Carlo methods,SRIM and MMonCa software were used to study the damage effect after proton irradiation.It was also found that the dislocation effect caused by proton irradiation was small,and the maximum damage value was 0.45 dpa.In order to further explore the evolution behavior of internal defects caused by the thermal peak effect during irradiation,the long-time annealing process in pure Cu and pure Nb media at different temperatures was simulated.It was found that the heating would lead to the formation of interstitial atomic clusters and vacancy clusters in the material,which would affect the macro properties of the material. |
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