We investigated the effect of grain boundary structures on the trapping strength of HeN（N is the number of helium atoms） defects in the grain boundaries of nickel. The results suggest that the binding energy of an i...We investigated the effect of grain boundary structures on the trapping strength of HeN（N is the number of helium atoms） defects in the grain boundaries of nickel. The results suggest that the binding energy of an interstitial helium atom to the grain boundary plane is the strongest among all sites around the plane. The He_N defect is much more stable in nickel bulk than in the grain boundary plane. Besides, the binding energy of an interstitial helium atom to a vacancy is stronger than that to a grain boundary plane. The binding strength between the grain boundary and the HeN defect increases with the defect size. Moreover, the binding strength of the HeN defect to the Σ3（112）[110] grain boundary becomes much weaker than that to other grain boundaries as the defect size increases.展开更多
The emerging wide bandgap semiconductorβ-Ga_(2)O_(3) has attracted great interest due to its promising applications for high-power electronic devices and solar-blind ultraviolet photodetectors.Deep-level defects inβ...The emerging wide bandgap semiconductorβ-Ga_(2)O_(3) has attracted great interest due to its promising applications for high-power electronic devices and solar-blind ultraviolet photodetectors.Deep-level defects inβ-Ga_(2)O_(3) have been intensively studied towards improving device performance.Deep-level signatures E_(1),E_(2),and E_(3) with energy positions of 0.55–0.63,0.74–0.81,and 1.01–1.10 eV below the conduction band minimum have frequently been observed and extensively investigated,but their atomic origins are still under debate.In this work,we attempt to clarify these deep-level signatures from the comparison of theoretically predicted electron capture cross-sections of suggested candidates,Ti and Fe substituting Ga on a tetrahedral site(Ti_(GaI) and Fe_(GaI))and an octahedral site(Ti_(GaII) and Fe_(GaII)),to experimentally measured results.The first-principles approach predicted electron capture cross-sections of Ti_(GaI) and Ti_(GaII) defects are 8.56×10^(–14) and 2.97×10^(–13) cm^(2),in good agreement with the experimental values of E_(1) and E_(3) centers,respectively.We,therefore,confirmed that E_(1) and E_(3) centers are indeed associated with Ti_(GaI) and Ti_(GaII) defects,respectively.Whereas the predicted electron capture cross-sections of Fe_(Ga) defect are two orders of magnitude larger than the experimental value of the E_(2),indicating E_(2) may have other origins like C_(Ga) and Ga_(i),rather than common believed Fe_(Ga).展开更多
基金Project supported by the Program of International S&T Cooperation,China(Grant No.2014DFG60230)the National Basic Research Program of China(Grant No.2010CB934504)+2 种基金Strategically Leading Program of the Chinese Academy of Sciences(Grant No.XDA02040100)the Shanghai Municipal Science and Technology Commission,China(Grant No.13ZR1448000)the National Natural Science Foundation of China(Grant Nos.91326105 and 21306220)
文摘We investigated the effect of grain boundary structures on the trapping strength of HeN（N is the number of helium atoms） defects in the grain boundaries of nickel. The results suggest that the binding energy of an interstitial helium atom to the grain boundary plane is the strongest among all sites around the plane. The He_N defect is much more stable in nickel bulk than in the grain boundary plane. Besides, the binding energy of an interstitial helium atom to a vacancy is stronger than that to a grain boundary plane. The binding strength between the grain boundary and the HeN defect increases with the defect size. Moreover, the binding strength of the HeN defect to the Σ3（112）[110] grain boundary becomes much weaker than that to other grain boundaries as the defect size increases.
基金This work was supported by the National Key Research and Development Program of China under Grant No.2018YFB2200105the Key Research Program of Frontier Sciences,CAS under Grant No.ZDBS-LY-JSC019the National Natural Science Foundation of China(NSFC)under Grant Nos.11925407 and 61927901.
文摘The emerging wide bandgap semiconductorβ-Ga_(2)O_(3) has attracted great interest due to its promising applications for high-power electronic devices and solar-blind ultraviolet photodetectors.Deep-level defects inβ-Ga_(2)O_(3) have been intensively studied towards improving device performance.Deep-level signatures E_(1),E_(2),and E_(3) with energy positions of 0.55–0.63,0.74–0.81,and 1.01–1.10 eV below the conduction band minimum have frequently been observed and extensively investigated,but their atomic origins are still under debate.In this work,we attempt to clarify these deep-level signatures from the comparison of theoretically predicted electron capture cross-sections of suggested candidates,Ti and Fe substituting Ga on a tetrahedral site(Ti_(GaI) and Fe_(GaI))and an octahedral site(Ti_(GaII) and Fe_(GaII)),to experimentally measured results.The first-principles approach predicted electron capture cross-sections of Ti_(GaI) and Ti_(GaII) defects are 8.56×10^(–14) and 2.97×10^(–13) cm^(2),in good agreement with the experimental values of E_(1) and E_(3) centers,respectively.We,therefore,confirmed that E_(1) and E_(3) centers are indeed associated with Ti_(GaI) and Ti_(GaII) defects,respectively.Whereas the predicted electron capture cross-sections of Fe_(Ga) defect are two orders of magnitude larger than the experimental value of the E_(2),indicating E_(2) may have other origins like C_(Ga) and Ga_(i),rather than common believed Fe_(Ga).
