The domains are of fundamental interest for engineering a ferroelectric material. The domain wall and its width control the ferroelectric behavior to a great extent. The stability of polarization in the context of Lan...The domains are of fundamental interest for engineering a ferroelectric material. The domain wall and its width control the ferroelectric behavior to a great extent. The stability of polarization in the context of Landau-Ginzburg free energy functional has been worked out in a previous work by a perturbation approach, where two limits of domain wall width were estimated within the stability zone and they were also found to correspond well with the data on lithium niobate and lithium tantalate. In the present work, it is shown that this model is valid for a wide range of ferroelectric materials and also for a given ferroelectric, such as lithium niobate with different levels of impurities, which are known to affect the domain wall width.展开更多
While experimental evidence demonstrates that the presence of hydrogen（H） impurities in diamond films plays a significant role in determining their physical properties, the small radius of the H atom makes detecting...While experimental evidence demonstrates that the presence of hydrogen（H） impurities in diamond films plays a significant role in determining their physical properties, the small radius of the H atom makes detecting such impurities quite a challenging task. In the present work, first-principles calculations were employed to provide an insight into the effects of the interstitial hydrogen on the electrical and mechanical properties of diamond crystals at the atomic level. The migrated pathways of the interstitial hydrogen are dictated by energetic considerations. Some new electronic states are formed near the Fermi level. The interstitial hydrogen markedly narrows the bandgap of the diamond and weakens the diamond crystal. The obvious decrement of the critical strain clearly implies the presence of an H-induced embrittlement effect.展开更多
YBa2Cu3-xVxO7-y(x=0, 0.1, 0.2, 0.3, 0.4, 0.5 and 0.6) superconductors have been prepared. X-ray diffraction shows that the system remains orthorhombic for all compositions studied, but for x > 0.4 V2O5 was detected...YBa2Cu3-xVxO7-y(x=0, 0.1, 0.2, 0.3, 0.4, 0.5 and 0.6) superconductors have been prepared. X-ray diffraction shows that the system remains orthorhombic for all compositions studied, but for x > 0.4 V2O5 was detected as an impurity phase. Substitution of V5+ for Cu2+ occurs in the Cu(2) sites on the Cu(2)-O planes. The introduction of the high valence element, vanadium, produces the extra free-electrons. These electrons recombine with the positive carrier of the system. It makes depression of the mobility and the Hall number of YBa2Cu3-xVxO7-v and also results in a depression of TC.展开更多
First-principles calculations based on the density functional theory（DFT） and ultra-soft pseudopotential are employed to study the atomic configuration and charge density of impurity P in Ni Al Σ5 grain boundary（G...First-principles calculations based on the density functional theory（DFT） and ultra-soft pseudopotential are employed to study the atomic configuration and charge density of impurity P in Ni Al Σ5 grain boundary（GB）. The negative segregation energy of a P atom proves that a P atom can easily segregate in the Ni Al GB. The atomic configuration and formation energy of the P atom in the Ni Al GB demonstrate that the P atom tends to occupy an interstitial site or substitute a Al atom depending on the Ni/Al atoms ratio. The P atom is preferable to staying in the Ni-rich environment in the Ni Al GB forming P–Ni bonds. Both of the charge density and the deformation charge imply that a P atom is more likely to bond with Ni atoms rather than with Al atoms. The density of states further exhibits the interactions between P atom and Ni atom, and the orbital electrons of P, Ni and Al atoms all contribute to P–Ni bonds in the Ni Al GB. It is worth noting that the P–Ni covalent bonds might embrittle the Ni Al GB and weakens the plasticity of the Ni Al intermetallics.展开更多
The near-infrared responsivity of a silicon photodetector employing the impurity photovoltaic （IPV） effect is investigated with a numerical method. The improvement of the responsivity can reach 0.358 A/W at a wavele...The near-infrared responsivity of a silicon photodetector employing the impurity photovoltaic （IPV） effect is investigated with a numerical method. The improvement of the responsivity can reach 0.358 A/W at a wavelength of about 1200 nm, and its corresponding quantum efficiency is 41.1%. The origin of the enhanced responsivity is attributed to the absorption of sub-bandgap photons, which results in the carrier transition from the impurity energy level to the conduction band. The results indicate that the IPV effect may provide a general approach to enhancing the responsivity of photodetectors.展开更多
We present a systematic study of the impurity scattering effect induced by Pd dopants in the super- conductor SrPt3P. Using a solid-state reaction method, we fabricated the Pd-doped superconductor Sr（Pt1-xPdx）3P. We...We present a systematic study of the impurity scattering effect induced by Pd dopants in the super- conductor SrPt3P. Using a solid-state reaction method, we fabricated the Pd-doped superconductor Sr（Pt1-xPdx）3P. We found that the residual resistivity P0 increases quickly with Pd doping, whereas the residual resistance ratio （RRR） displays a dramatic reduction. In addition, both the nonlinear field-dependent behavior of the Hall resistivity Pxy and the strong temperature dependence of the Hall coefficient RH at low temperature are suppressed by Pd doping. All the experimental results can be explained by an increase in scattering by impurities induced by doping. Our results suggest that the Pt position is very crucial to the carrier conduction in the present system.展开更多
基金supported by National Key R&D Program of China(Grant No.2022YFA1403201)National Natural Science Foundation of China(Grant No.12274205 and No.11874205).
文摘The domains are of fundamental interest for engineering a ferroelectric material. The domain wall and its width control the ferroelectric behavior to a great extent. The stability of polarization in the context of Landau-Ginzburg free energy functional has been worked out in a previous work by a perturbation approach, where two limits of domain wall width were estimated within the stability zone and they were also found to correspond well with the data on lithium niobate and lithium tantalate. In the present work, it is shown that this model is valid for a wide range of ferroelectric materials and also for a given ferroelectric, such as lithium niobate with different levels of impurities, which are known to affect the domain wall width.
基金Project supported by the Project of Construction of Innovative Teams and Teacher Career Development for Universities and Colleges under Beijing Municipality,China(Grant No.IDHT20140504)the National Natural Science Foundation of China(Grant No.51402009)the Foundation for Young Scholars of Beijing University of Technology,China
文摘While experimental evidence demonstrates that the presence of hydrogen（H） impurities in diamond films plays a significant role in determining their physical properties, the small radius of the H atom makes detecting such impurities quite a challenging task. In the present work, first-principles calculations were employed to provide an insight into the effects of the interstitial hydrogen on the electrical and mechanical properties of diamond crystals at the atomic level. The migrated pathways of the interstitial hydrogen are dictated by energetic considerations. Some new electronic states are formed near the Fermi level. The interstitial hydrogen markedly narrows the bandgap of the diamond and weakens the diamond crystal. The obvious decrement of the critical strain clearly implies the presence of an H-induced embrittlement effect.
基金Project supported by the National Science and Technology Committee of China and the National Natural Science Foundation of China.
文摘YBa2Cu3-xVxO7-y(x=0, 0.1, 0.2, 0.3, 0.4, 0.5 and 0.6) superconductors have been prepared. X-ray diffraction shows that the system remains orthorhombic for all compositions studied, but for x > 0.4 V2O5 was detected as an impurity phase. Substitution of V5+ for Cu2+ occurs in the Cu(2) sites on the Cu(2)-O planes. The introduction of the high valence element, vanadium, produces the extra free-electrons. These electrons recombine with the positive carrier of the system. It makes depression of the mobility and the Hall number of YBa2Cu3-xVxO7-v and also results in a depression of TC.
基金Project supported by the National Natural Science Foundation of China(Grant No.51201181)the Scientific Research Fund of Civil Aviation University of China(Grant No.08QD14X)
文摘First-principles calculations based on the density functional theory（DFT） and ultra-soft pseudopotential are employed to study the atomic configuration and charge density of impurity P in Ni Al Σ5 grain boundary（GB）. The negative segregation energy of a P atom proves that a P atom can easily segregate in the Ni Al GB. The atomic configuration and formation energy of the P atom in the Ni Al GB demonstrate that the P atom tends to occupy an interstitial site or substitute a Al atom depending on the Ni/Al atoms ratio. The P atom is preferable to staying in the Ni-rich environment in the Ni Al GB forming P–Ni bonds. Both of the charge density and the deformation charge imply that a P atom is more likely to bond with Ni atoms rather than with Al atoms. The density of states further exhibits the interactions between P atom and Ni atom, and the orbital electrons of P, Ni and Al atoms all contribute to P–Ni bonds in the Ni Al GB. It is worth noting that the P–Ni covalent bonds might embrittle the Ni Al GB and weakens the plasticity of the Ni Al intermetallics.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.61464007,61306084,and 51361022)the Postdoctoral Science Foundation of Jiangxi Province,China(Grant No.2014KY32)the Natural Science Foundation of Jiangxi Province,China(Grant No.20122BAB202002)
文摘The near-infrared responsivity of a silicon photodetector employing the impurity photovoltaic （IPV） effect is investigated with a numerical method. The improvement of the responsivity can reach 0.358 A/W at a wavelength of about 1200 nm, and its corresponding quantum efficiency is 41.1%. The origin of the enhanced responsivity is attributed to the absorption of sub-bandgap photons, which results in the carrier transition from the impurity energy level to the conduction band. The results indicate that the IPV effect may provide a general approach to enhancing the responsivity of photodetectors.
基金This work was supported by the National Natural Science Foundation of China （Grant No. 11204338）, the ＂Strategic Priority Research Program （B）＂ of the Chinese Academy of Sciences （Grant No. XDB04040300）, and the Youth Innovation Promotion Association of the Chinese Academy of Sciences （Grant No. 2015187）. This work was partly sponsored by the Science and Technology Commission of Shanghai Municipality （Grant Nos. 14DZ2260700 and 14521102800）.
文摘We present a systematic study of the impurity scattering effect induced by Pd dopants in the super- conductor SrPt3P. Using a solid-state reaction method, we fabricated the Pd-doped superconductor Sr（Pt1-xPdx）3P. We found that the residual resistivity P0 increases quickly with Pd doping, whereas the residual resistance ratio （RRR） displays a dramatic reduction. In addition, both the nonlinear field-dependent behavior of the Hall resistivity Pxy and the strong temperature dependence of the Hall coefficient RH at low temperature are suppressed by Pd doping. All the experimental results can be explained by an increase in scattering by impurities induced by doping. Our results suggest that the Pt position is very crucial to the carrier conduction in the present system.
