The geometry,stability,binding energy and electronic properties of(SiO2)n and Ge(SiO2)n clusters(n = 7) have been investigated by Density functional theory(DFT).The results show that the lowest energy structur...The geometry,stability,binding energy and electronic properties of(SiO2)n and Ge(SiO2)n clusters(n = 7) have been investigated by Density functional theory(DFT).The results show that the lowest energy structures of Ge(SiO2)n are obtained by adding one Ge on the end site of the O atom or the Si near end site of the O atom in(SiO2)n.The chemical activation of Ge-(SiO2)n is improved compared with(SiO2)n.The calculated second-order difference of energies and fragmentation energies show that the Ge(SiO2)n clusters with n = 2 or 5 are stable.展开更多
We report the pressure dependence of Ge nanocrystals embedded in SiO2 film matrix on Si substrate using Raman scattering and finite element analysis. Delamination of SiO2 film from the Si substrate occurs at ~23 kbar...We report the pressure dependence of Ge nanocrystals embedded in SiO2 film matrix on Si substrate using Raman scattering and finite element analysis. Delamination of SiO2 film from the Si substrate occurs at ~23 kbar due to the large difference between the compressibility of the SiO2 matrix and Si substrate. The observed effect can be understood by the nonhomogeneous distribution of the elastic field in the Ge/SiO2/Si nanosystem. Previous high pressure PL results on the Si/SiO2/Si nanosystem can also be explained by the nonuniform distribution of the elastic field. Although our investigation focuses on the Ge/SiO2/Si nanosystem, our results could provide generally understanding on the elastic properties of different multi-component nanosystems.展开更多
A novel red-emitting K2(Ge,Si)F6:Mn^4+ phosphor with uniform morphology was synthesized by co-precipitation method. The pure K2GeF6 phase with P63 mc space group other than P3m1 space group was affirmed just by in...A novel red-emitting K2(Ge,Si)F6:Mn^4+ phosphor with uniform morphology was synthesized by co-precipitation method. The pure K2GeF6 phase with P63 mc space group other than P3m1 space group was affirmed just by incorporation of Si in K2GeF6 at room temperature according to XRD characterization. SEM images showed lamellar and octahedron grain morphology for K2GeF6:Mn^4+ and K2(Ge,Si)F6:Mn^4+ phosphors, respectively. It was also found that the photoluminescence excitation(PLE) and photoluminescence(PL) showed slight displacement in K2GeF6:Mn^4+ and K2(Ge,Si)F6:Mn^4+ system. And the zero-phonon line(ZPL) of the PL spectrum of K2GeF6:Mn^4+ with Si showed a strong peak. Meanwhile crystalline field surrounding Mn^4+ changes could affect the decay time in this fluoride system. The color gamut of the LED devices based on K2(Ge,Si)F6:Mn^4+ and K2GeF6:Mn^4+ reached up to 94.58% NTSC(National Television Standards Committee) and 94.386% NTSC, respectively, that was much higher than that based on nitride red phosphors. All these original characteristics in K2(Ge,Si)F6:Mn^4+ phosphor are desirable for potential applications as a red phosphor for improving lighting and display quality of conventional white LEDs.展开更多
基金Project supported by the foundation start up for high level talents of Shihezi university (No. RCZX200747)
摘要The geometry,stability,binding energy and electronic properties of(SiO2)n and Ge(SiO2)n clusters(n = 7) have been investigated by Density functional theory(DFT).The results show that the lowest energy structures of Ge(SiO2)n are obtained by adding one Ge on the end site of the O atom or the Si near end site of the O atom in(SiO2)n.The chemical activation of Ge-(SiO2)n is improved compared with(SiO2)n.The calculated second-order difference of energies and fragmentation energies show that the Ge(SiO2)n clusters with n = 2 or 5 are stable.
摘要We report the pressure dependence of Ge nanocrystals embedded in SiO2 film matrix on Si substrate using Raman scattering and finite element analysis. Delamination of SiO2 film from the Si substrate occurs at ~23 kbar due to the large difference between the compressibility of the SiO2 matrix and Si substrate. The observed effect can be understood by the nonhomogeneous distribution of the elastic field in the Ge/SiO2/Si nanosystem. Previous high pressure PL results on the Si/SiO2/Si nanosystem can also be explained by the nonuniform distribution of the elastic field. Although our investigation focuses on the Ge/SiO2/Si nanosystem, our results could provide generally understanding on the elastic properties of different multi-component nanosystems.
基金Project supported by the Major State Basic Research Development Program of China(National Basic Research Program of China)(2014CB643801973)
摘要A novel red-emitting K2(Ge,Si)F6:Mn^4+ phosphor with uniform morphology was synthesized by co-precipitation method. The pure K2GeF6 phase with P63 mc space group other than P3m1 space group was affirmed just by incorporation of Si in K2GeF6 at room temperature according to XRD characterization. SEM images showed lamellar and octahedron grain morphology for K2GeF6:Mn^4+ and K2(Ge,Si)F6:Mn^4+ phosphors, respectively. It was also found that the photoluminescence excitation(PLE) and photoluminescence(PL) showed slight displacement in K2GeF6:Mn^4+ and K2(Ge,Si)F6:Mn^4+ system. And the zero-phonon line(ZPL) of the PL spectrum of K2GeF6:Mn^4+ with Si showed a strong peak. Meanwhile crystalline field surrounding Mn^4+ changes could affect the decay time in this fluoride system. The color gamut of the LED devices based on K2(Ge,Si)F6:Mn^4+ and K2GeF6:Mn^4+ reached up to 94.58% NTSC(National Television Standards Committee) and 94.386% NTSC, respectively, that was much higher than that based on nitride red phosphors. All these original characteristics in K2(Ge,Si)F6:Mn^4+ phosphor are desirable for potential applications as a red phosphor for improving lighting and display quality of conventional white LEDs.