Raman spectra of gallium phosphide （GAP） nanosolids （unheated and heat-treated at 598 and 723 K, respectively） were investigated. It was observed that both the longitudinal optical mode （LO） and the transverse o...Raman spectra of gallium phosphide （GAP） nanosolids （unheated and heat-treated at 598 and 723 K, respectively） were investigated. It was observed that both the longitudinal optical mode （LO） and the transverse optical mode （TO） displayed an asymmetry on the low-wavenumber side. The scattering bands were fitted to a sum of four Lorentzians which were assigned to the LO mode, surface phonon mode, TO mode, and a combination of Ga-O-P symmetric bending and sum band formed from the X-point TA ＋ LA phonons, respectively. Analysis of the characteristic of surface phonon mode revealed that the surface phonon peak of the GaP nanosolids could be confirmed. In the infrared spectrum of the GaP nanoparticles, we observed the bands on account of symmetric stretching and bending of PO2, as well as stretching of Ga-O The Raman scattering intensity arising from the Ga-O-P linkages increased as increasing the heat-treatment temperature.展开更多
The main aim of this paper is to discuss the confinement effects on the optical and acoustic phonon vibrational modes in gallium phosphide（GaP） nanoparticles（cylindric grain）.The Raman scattering from the GaP nano...The main aim of this paper is to discuss the confinement effects on the optical and acoustic phonon vibrational modes in gallium phosphide（GaP） nanoparticles（cylindric grain）.The Raman scattering from the GaP nanoparticles was investigated.It was found that the red-shifts of the longitudinal optical（LO） mode and transverse optical（TO） mode were 15 cm？1 and 13.8 cm？1,respectively.It is generally accepted that the red-shifts of the optical phonon modes are due to the presence of smaller nanosized particles（～1.2 nm） acting as the nanoclustered building blocks of the GaP nanoparticles.In the low frequency Raman spectrum,a set of Stokes lines with almost the same spacing was clearly observed.The scattering feature originates from the discrete phonon density of states of the nanoclustered building blocks.According to Lamb＇s vibrational theory,the Raman shift wavenumbers of the spheroidal mode and torsional mode of the lowest energy surface modes for the nanoclustered building blocks were calculated.Good agreement can be achieved between the calculated results and the observed scattering peaks.These results indicate that the corresponding Raman peaks are due to scattering from the localized acoustic phonons in the nanoclustered building blocks in the GaP nanoparticles.展开更多
The value of spin-orbit splitting Δ 0 of gallium phosphide （GaP） nanoparticles was determined. The information concerning the spin-orbit splitting of the valence band at Γ was acquired using fluorescence and infra...The value of spin-orbit splitting Δ 0 of gallium phosphide （GaP） nanoparticles was determined. The information concerning the spin-orbit splitting of the valence band at Γ was acquired using fluorescence and infrared spectroscopes. Detailed investigation on the fluorescence characteristics under ultraviolet photoexcitation reveals that two doublets of emission transitions are related to the spin-orbit splitting of the valence band. The origin of two broad violet emissions, 3.00 and 3.10 eV, can be attributed to the direct transitions near the Γ point of the Brillouin zone between the Γ 1 conduction band and Γ 15 valance band, that is, Γ 6c –Γ 8v and Γ 6c –Γ 7v , respectively. The origin of two blue emissions, 2.74 and 2.64 eV, can be attributed to the indirect transitions between the X 1 conduction band and Γ 15 valance band, that is, Δ 5c –Γ 8v and Δ 5c –Γ 7v , respectively. Based on these transitions, the spin-orbit splitting Δ 0 of the GaP nanoparticles is determined as 0.10 eV. The infrared spectrum of the GaP nanoparticles shows a band at 817 cm -1 which is assigned to the transition between the Γ 7v and Γ 8v valence band maxima. It follows therefore that the spin-orbit splitting Δ 0 is 0.10 eV.展开更多
Gallium phosphide （GAP） nanoparticulate thin films were easily fabricated by colloidal suspension deposition via GaP nanoparticles dispersed in N,N-dimethylformamide. The microstructure of the film was performed by ...Gallium phosphide （GAP） nanoparticulate thin films were easily fabricated by colloidal suspension deposition via GaP nanoparticles dispersed in N,N-dimethylformamide. The microstructure of the film was performed by x-ray diffraction, high resolution transmission electron microscopy and field emission scanning electron microscopy. The film was further investigated by spectroscopic ellipsometry. After the model GaP＋void[SiO2 was built and an effective medium approximation was adopted, the values of the refractive index n and the extinction coefficient k were calculated for the energy range of 0.75 eV-4.0 eV using the dispersion formula in DeltaPsi2 software. The absorption coefficient of the film was calculated from its k and its energy gaps were further estimated according to the Tauc equation, which were further verified by its fluorescence spectrum measurement. The structure and optical absorption properties of the nanoparticulate films are promising for their potential applications in hybrid solar cells.展开更多
Under mild ambient conditions gallium phosphide （GAP） nanoparticles were employed to carry out the reduction of nitrogen. By using Nessler＇s reagent ammonia was detected in the slurry where the aggregated GAP parti...Under mild ambient conditions gallium phosphide （GAP） nanoparticles were employed to carry out the reduction of nitrogen. By using Nessler＇s reagent ammonia was detected in the slurry where the aggregated GAP particles were suspended in water and bubbled by pure nitrogen. Dependence of the concentration of ammonia upon bubbring time, velocity of the flow of nitrogen, and dosage of GAP particles was investigated. In comparison with the original GAP nanoparticles, the Raman scattering of the GAP particles undergoing the process of nitrogen fixation reveals that two sharp lines at 138 and 182 cm^-1, respectively, emerged from the broad continuum around 100-200 cm^-1. These two lines might be assigned to the translational motions of ammonia adsorbed on the surface of the GAP particles. An assessment of the infrared spectra of the two GAP particles led to the conclusion that the environment of the two H2O molecules was not identical. Analysis of the electron spin resonance results showed that the structure defect, gallium self-interstitial, was not involved in the nitrogen fixation of the GAP nanoparticles.展开更多
Radio-frequency （RF） magnetron sputtering was employed to prepare gallium phosphide （GAP） thick films on zinc sulfide （ZnS） substrates by sputtering a single crystalline GaP target in an Ar atmosphere. The infra...Radio-frequency （RF） magnetron sputtering was employed to prepare gallium phosphide （GAP） thick films on zinc sulfide （ZnS） substrates by sputtering a single crystalline GaP target in an Ar atmosphere. The infrared （IR） transmission properties, structure, morphology, composition and hardness of the film were studied. Results show that both amorphous and zinc-blende crystalline phases existed in the GaP film in almost stoichiometric amounts. The GaP film exhibited good IR transmission properties, though the relatively rough surface and loose microstructure caused a small loss of IR transmission due to scattering. The GaP film also showed a much higher haraness than the ZnS substrate, thereby providing good protection to ZnS.展开更多
In the present study, we have theoretically modelled a surface plasmon resonance （SPR） based sensing chip utilizing a prism made up of gallium phosphidee. It has been found in the study that a large range of refract...In the present study, we have theoretically modelled a surface plasmon resonance （SPR） based sensing chip utilizing a prism made up of gallium phosphidee. It has been found in the study that a large range of refractive index starting from the gaseous medium to highly concentrated liquids can be sensed by using a single chip in the visible region of the spectrum. The variation of the sensitivity as well as detection accuracy with sensing region refractive index has been analyzed in detail. The large value of the sensitivity along with the large dynamic range is the advantageous feature of the present sensing probe.展开更多
We introduce a nanoscale photonic platform based on gallium phosphide. Owing to the favorable material properties, peak power intensity levels of 50 GW∕cm^2 are safely reached in a suspended membrane. Consequently,th...We introduce a nanoscale photonic platform based on gallium phosphide. Owing to the favorable material properties, peak power intensity levels of 50 GW∕cm^2 are safely reached in a suspended membrane. Consequently,the field enhancement is exploited to a far greater extent to achieve efficient and strong light–matter interaction.As an example, parametric interactions are shown to reach a deeply nonlinear regime, revealing cascaded fourwave mixing leading to comb generation and high-order soliton dynamics.展开更多
The growth of GaP layer on GaN with and without buffer layers by metal-organic chemical vapour deposition （MOCVD） has been studied. Results indicate that the GaP low temperature buffer layer can provide a high densi...The growth of GaP layer on GaN with and without buffer layers by metal-organic chemical vapour deposition （MOCVD） has been studied. Results indicate that the GaP low temperature buffer layer can provide a high density of nucleation sites for high temperature （HT） GaP growth. These sites can promote the two-dimensional （2D） growth of HT GaP and reduce the surface roughness. A GaP single crystal layer grown at 680 ℃ is obtained using a 40-nm thick GaP buffer layer. The full-width at half-maximum （FWHM） of the （111） plane of GaP layer, measured by DCXRD, is 560 arcsec. The GaP layer grown on GaN without low temperature GaP buffer layer shows a rougher surface. However, the FWHM of the （111） plane is 408 arcsec, which is the indication of better crystal quality for the GaP layer grown on GaN without a low temperature buffer layer. Because it provides less nucleation sites grown at high growth temperature, the three-dimensional （3D） growth is prolonged. The crystalline quality of GaP is lightly improved when the surface of GaN substrate is pretreated by PH3, while it turned to be polycrystalline when the substrate is pretreated by TEGa.展开更多
In this work, gallium phosphide thin films were deposited on glass substrates by radio frequency （RF） magnetron sputtering technique under different depositions conditions. The X-ray diffraction analysis showed a di...In this work, gallium phosphide thin films were deposited on glass substrates by radio frequency （RF） magnetron sputtering technique under different depositions conditions. The X-ray diffraction analysis showed a diversity of states： from amorphous in the films deposited at 175 ~C to a nearly stoichiometric and polycrystalline films, exhibiting cubic phase with preferred orientation along （220）, in the films deposited at temperatures higher than 250 ~C. Scanning electron microscopy images revealed that all films were uniform with a smooth surface, while the energy-dispersive spectroscopy （EDS） analysis showed that there was a visible dependence on the Ga/P ratio in the deposition conditions and confirmed that a residual Ga metallic phase was presented in the surface of all the films. The Raman analysis showed the structural evolution of the GaP films was strongly dependent on the deposition conditions. The conductivity of the films was slightly dependent on the argon pressure and the rf power, but strongly dependent on the deposition temperature, mainly above 200 ~C. The optical transmission and absorption analyses of the GaP films revealed an indirect band gap of ~ 1.70 eV in the films deposited at temperatures less than 200 ~C, which transited to a band gap of 2.26 eV as the deposition temperature was close to 300 ~C.展开更多
文摘Raman spectra of gallium phosphide （GAP） nanosolids （unheated and heat-treated at 598 and 723 K, respectively） were investigated. It was observed that both the longitudinal optical mode （LO） and the transverse optical mode （TO） displayed an asymmetry on the low-wavenumber side. The scattering bands were fitted to a sum of four Lorentzians which were assigned to the LO mode, surface phonon mode, TO mode, and a combination of Ga-O-P symmetric bending and sum band formed from the X-point TA ＋ LA phonons, respectively. Analysis of the characteristic of surface phonon mode revealed that the surface phonon peak of the GaP nanosolids could be confirmed. In the infrared spectrum of the GaP nanoparticles, we observed the bands on account of symmetric stretching and bending of PO2, as well as stretching of Ga-O The Raman scattering intensity arising from the Ga-O-P linkages increased as increasing the heat-treatment temperature.
文摘The main aim of this paper is to discuss the confinement effects on the optical and acoustic phonon vibrational modes in gallium phosphide（GaP） nanoparticles（cylindric grain）.The Raman scattering from the GaP nanoparticles was investigated.It was found that the red-shifts of the longitudinal optical（LO） mode and transverse optical（TO） mode were 15 cm？1 and 13.8 cm？1,respectively.It is generally accepted that the red-shifts of the optical phonon modes are due to the presence of smaller nanosized particles（～1.2 nm） acting as the nanoclustered building blocks of the GaP nanoparticles.In the low frequency Raman spectrum,a set of Stokes lines with almost the same spacing was clearly observed.The scattering feature originates from the discrete phonon density of states of the nanoclustered building blocks.According to Lamb＇s vibrational theory,the Raman shift wavenumbers of the spheroidal mode and torsional mode of the lowest energy surface modes for the nanoclustered building blocks were calculated.Good agreement can be achieved between the calculated results and the observed scattering peaks.These results indicate that the corresponding Raman peaks are due to scattering from the localized acoustic phonons in the nanoclustered building blocks in the GaP nanoparticles.
文摘The value of spin-orbit splitting Δ 0 of gallium phosphide （GaP） nanoparticles was determined. The information concerning the spin-orbit splitting of the valence band at Γ was acquired using fluorescence and infrared spectroscopes. Detailed investigation on the fluorescence characteristics under ultraviolet photoexcitation reveals that two doublets of emission transitions are related to the spin-orbit splitting of the valence band. The origin of two broad violet emissions, 3.00 and 3.10 eV, can be attributed to the direct transitions near the Γ point of the Brillouin zone between the Γ 1 conduction band and Γ 15 valance band, that is, Γ 6c –Γ 8v and Γ 6c –Γ 7v , respectively. The origin of two blue emissions, 2.74 and 2.64 eV, can be attributed to the indirect transitions between the X 1 conduction band and Γ 15 valance band, that is, Δ 5c –Γ 8v and Δ 5c –Γ 7v , respectively. Based on these transitions, the spin-orbit splitting Δ 0 of the GaP nanoparticles is determined as 0.10 eV. The infrared spectrum of the GaP nanoparticles shows a band at 817 cm -1 which is assigned to the transition between the Γ 7v and Γ 8v valence band maxima. It follows therefore that the spin-orbit splitting Δ 0 is 0.10 eV.
文摘Gallium phosphide （GAP） nanoparticulate thin films were easily fabricated by colloidal suspension deposition via GaP nanoparticles dispersed in N,N-dimethylformamide. The microstructure of the film was performed by x-ray diffraction, high resolution transmission electron microscopy and field emission scanning electron microscopy. The film was further investigated by spectroscopic ellipsometry. After the model GaP＋void[SiO2 was built and an effective medium approximation was adopted, the values of the refractive index n and the extinction coefficient k were calculated for the energy range of 0.75 eV-4.0 eV using the dispersion formula in DeltaPsi2 software. The absorption coefficient of the film was calculated from its k and its energy gaps were further estimated according to the Tauc equation, which were further verified by its fluorescence spectrum measurement. The structure and optical absorption properties of the nanoparticulate films are promising for their potential applications in hybrid solar cells.
文摘Under mild ambient conditions gallium phosphide （GAP） nanoparticles were employed to carry out the reduction of nitrogen. By using Nessler＇s reagent ammonia was detected in the slurry where the aggregated GAP particles were suspended in water and bubbled by pure nitrogen. Dependence of the concentration of ammonia upon bubbring time, velocity of the flow of nitrogen, and dosage of GAP particles was investigated. In comparison with the original GAP nanoparticles, the Raman scattering of the GAP particles undergoing the process of nitrogen fixation reveals that two sharp lines at 138 and 182 cm^-1, respectively, emerged from the broad continuum around 100-200 cm^-1. These two lines might be assigned to the translational motions of ammonia adsorbed on the surface of the GAP particles. An assessment of the infrared spectra of the two GAP particles led to the conclusion that the environment of the two H2O molecules was not identical. Analysis of the electron spin resonance results showed that the structure defect, gallium self-interstitial, was not involved in the nitrogen fixation of the GAP nanoparticles.
基金supported by the Aviation ScienceFoundation of China under grant No. 2008ZE53043
文摘Radio-frequency （RF） magnetron sputtering was employed to prepare gallium phosphide （GAP） thick films on zinc sulfide （ZnS） substrates by sputtering a single crystalline GaP target in an Ar atmosphere. The infrared （IR） transmission properties, structure, morphology, composition and hardness of the film were studied. Results show that both amorphous and zinc-blende crystalline phases existed in the GaP film in almost stoichiometric amounts. The GaP film exhibited good IR transmission properties, though the relatively rough surface and loose microstructure caused a small loss of IR transmission due to scattering. The GaP film also showed a much higher haraness than the ZnS substrate, thereby providing good protection to ZnS.
文摘In the present study, we have theoretically modelled a surface plasmon resonance （SPR） based sensing chip utilizing a prism made up of gallium phosphidee. It has been found in the study that a large range of refractive index starting from the gaseous medium to highly concentrated liquids can be sensed by using a single chip in the visible region of the spectrum. The variation of the sensitivity as well as detection accuracy with sensing region refractive index has been analyzed in detail. The large value of the sensitivity along with the large dynamic range is the advantageous feature of the present sensing probe.
基金“Investissements d’Avenir”program,French Agence Nationale de la Recherche(ANR)(ANR-10-LABX-0035)through the contact“CONDOR”French RENATECH NetworkIDEX AAP IDI 2013(37-2013)
文摘We introduce a nanoscale photonic platform based on gallium phosphide. Owing to the favorable material properties, peak power intensity levels of 50 GW∕cm^2 are safely reached in a suspended membrane. Consequently,the field enhancement is exploited to a far greater extent to achieve efficient and strong light–matter interaction.As an example, parametric interactions are shown to reach a deeply nonlinear regime, revealing cascaded fourwave mixing leading to comb generation and high-order soliton dynamics.
基金Project supported by the National Natural Science Foundation of China (Grant No. 50602018)the Natural Science Foundation of Guangdong Province of China (Grant No. 8251063101000007)the Science and Technology Program of Guangdong Province of China (Grant Nos. 2007498351 and 2009B011100003)
文摘The growth of GaP layer on GaN with and without buffer layers by metal-organic chemical vapour deposition （MOCVD） has been studied. Results indicate that the GaP low temperature buffer layer can provide a high density of nucleation sites for high temperature （HT） GaP growth. These sites can promote the two-dimensional （2D） growth of HT GaP and reduce the surface roughness. A GaP single crystal layer grown at 680 ℃ is obtained using a 40-nm thick GaP buffer layer. The full-width at half-maximum （FWHM） of the （111） plane of GaP layer, measured by DCXRD, is 560 arcsec. The GaP layer grown on GaN without low temperature GaP buffer layer shows a rougher surface. However, the FWHM of the （111） plane is 408 arcsec, which is the indication of better crystal quality for the GaP layer grown on GaN without a low temperature buffer layer. Because it provides less nucleation sites grown at high growth temperature, the three-dimensional （3D） growth is prolonged. The crystalline quality of GaP is lightly improved when the surface of GaN substrate is pretreated by PH3, while it turned to be polycrystalline when the substrate is pretreated by TEGa.
基金supported by the ERDF (European Regional Development Fund) through the COMPETE Programme (operational programme for competitiveness)by the Portuguese National Strategic Reference Framework (NSRF) through the project CFC-5568
文摘In this work, gallium phosphide thin films were deposited on glass substrates by radio frequency （RF） magnetron sputtering technique under different depositions conditions. The X-ray diffraction analysis showed a diversity of states： from amorphous in the films deposited at 175 ~C to a nearly stoichiometric and polycrystalline films, exhibiting cubic phase with preferred orientation along （220）, in the films deposited at temperatures higher than 250 ~C. Scanning electron microscopy images revealed that all films were uniform with a smooth surface, while the energy-dispersive spectroscopy （EDS） analysis showed that there was a visible dependence on the Ga/P ratio in the deposition conditions and confirmed that a residual Ga metallic phase was presented in the surface of all the films. The Raman analysis showed the structural evolution of the GaP films was strongly dependent on the deposition conditions. The conductivity of the films was slightly dependent on the argon pressure and the rf power, but strongly dependent on the deposition temperature, mainly above 200 ~C. The optical transmission and absorption analyses of the GaP films revealed an indirect band gap of ~ 1.70 eV in the films deposited at temperatures less than 200 ~C, which transited to a band gap of 2.26 eV as the deposition temperature was close to 300 ~C.
