In this paper,Raman shifts of a-plane GaN layers grown on r-plane sapphire substrates by low-pressure metal-organic chemical vapor deposition（LPMOCVD） are investigated.We compare the crystal qualities and study the ...In this paper,Raman shifts of a-plane GaN layers grown on r-plane sapphire substrates by low-pressure metal-organic chemical vapor deposition（LPMOCVD） are investigated.We compare the crystal qualities and study the relationships between Raman shift and temperature for conventional a-plane GaN epilayer and insertion AlN/AlGaN superlattice layers for a-plane GaN epilayer using temperature-dependent Raman scattering in a temperature range from 83 K to 503 K.The temperature-dependences of GaN phonon modes（A1（TO）,E2（high）,and E1（TO）） and the linewidths of E2（high） phonon peak are studied.The results indicate that there exist two mechanisms between phonon peaks in the whole temperature range,and the relationship can be fitted to the pseudo-Voigt function.From analytic results we find a critical temperature existing in the relationship,which can characterize the anharmonic effects of a-plane GaN in different temperature ranges.In the range of higher temperature,the relationship exhibits an approximately linear behavior,which is consistent with the analyzed results theoretically.展开更多
Raman soliton self-frequency shifted to mid-infrared band（λ 〉 2 μm） has been achieved in an air-silica microstructure fiber（MF）. The MF used in our experiment has an elliptical core with diameters of 1.08 and 2...Raman soliton self-frequency shifted to mid-infrared band（λ 〉 2 μm） has been achieved in an air-silica microstructure fiber（MF）. The MF used in our experiment has an elliptical core with diameters of 1.08 and 2.48 μm for fast and slow axis. Numerical simulation shows that each fundamental orthogonal polarization mode has two wide-spaced λZDW and theλZDW pairs located at 701/2110 nm and 755/2498 nm along the fast and slow axis, respectively. Using 810-nm Ti：sapphire femtosecond laser as pump, when the output power varies from 0.3 to 0.5 W, the furthest red-shift Raman solitons in both fast and slow axis shift from near-infrared band to mid-infrared band, reaching as far as 2030 and 2261 nm. Also, midinfrared Raman solitons can always be generated for pump wavelength longer than 790 nm if output pump power reaches0.5 W. Specifically, with pump power at 0.5 W, the mid-infrared soliton in slow axis shifts from 2001 to 2261 nm when the pump changes from 790 nm to 810 nm. This means only a 20 nm change of pump results in 260 nm tunability of a mid-infrared soliton.展开更多
Nitrogen hydrate samples were synthesized using liquid nitrogen and powder ice at 16 MPa and 253 K. Confocal laser Raman spectroscopy was used to investigate the characteristics of nitrogen clathrate hydrates. The res...Nitrogen hydrate samples were synthesized using liquid nitrogen and powder ice at 16 MPa and 253 K. Confocal laser Raman spectroscopy was used to investigate the characteristics of nitrogen clathrate hydrates. The results show that the Raman peaks of N-N and O-H stretching vibration in nitrogen hydrates are observed at 2322.4 and 3092.1 cm^-1, respectively, which are very similar to those in natural air clathrate hydrates. For comparison, we measured the Raman peaks of N-N stretching vibration both in liquid nitrogen and nitrogen molecules saturated water, which appear at 2326.6 and 2325.0 cm^-1, respectively. The Raman spectroscopic observations on the dissociation process suggest that nitrogen molecules occupy both the large and small cages in nitrogen clathrate hydrates. However, only one Raman peak is observed for N N stretching vibration because the difference of the environment of nitrogen molecules between large and small cages is too small to be differentiated by Raman spectroscopy.展开更多
Surface-enhanced Raman spectroscopy（SERS） is an intense ongoing hot topic because it is an attractive tool for sensing or detecting molecules in trace amounts. Despite its high specificity and sensitivity, the SERS ...Surface-enhanced Raman spectroscopy（SERS） is an intense ongoing hot topic because it is an attractive tool for sensing or detecting molecules in trace amounts. Despite its high specificity and sensitivity, the SERS technique has not been established as a routine analytic method most likely due to the low reproducibility of the SERS signal. This review considers the influence factors to produce the poor reproducibility during the SERS measurement. This review starts with the discussion of calculation of surface-enhanced Raman intensity in order to explain the reason why it is so difficult to achieve a high reproducibility of SERS measurement from the origin of enhancement mechanism. Then we focus on the fabrication of SERS substrates generally including two types：① single particles and ② arrays on substrate that are directly used to detect molecules or other components.In addition, we discuss the molecule factors and optical system for the reproducibility for sample-to-sample or spot-to-spot on a substrate. In the final part of this review, some effects resulting in the irreproducibility of Raman bands＇ position from recent literatures are discussed.展开更多
Due to its ubiquitous occurrence in igneous,metamorphic,and sedimentary rocks and its wide application in geochronology and geochemistry,zircon has become the most widely used accessory mineral in the geological commu...Due to its ubiquitous occurrence in igneous,metamorphic,and sedimentary rocks and its wide application in geochronology and geochemistry,zircon has become the most widely used accessory mineral in the geological community.Nevertheless,the decay of U and Th causes radiation damage to the zircon structure,resulting in various degrees of metamictization,which can affect the accuracy of U–Pb dates and Hf and O isotope results.If the degree of zircon radiation damage can be quantified,the influence on geochemical analyses can be evaluated,and the results can be corrected more precisely.In this paper,synthetic and natural zircon crystals with different crystallization ages were selected for Raman spectroscopy analysis,cathodoluminescence imaging,and determination of the U and Th concentrations.The results show that Raman FWHM(full width at half bandmaximum)and Raman shift correlate with alpha dose(Da)ofzirconsfollowingtheseequations,FWHM=44.36(±2.32)×[1-exp(-2.74×Da)]-+1.7(±0.19),Raman Shift=-6.53×Da+1007.69.Analysis of synthetic zircon crystals shows that doped REEs(rare earth elements and P)can also lead to an increase in the FWHM.However,this effect can be ignored for natural zircon samples with REE contents at a normal level of hundreds to a few thousand ppm.The FWHM and Raman shift can be used as proxies to measure the degree of zircon radiation damage.Using the updated equations to calculate the latest age when zircon began to accumulate radiation damage,a more accurate and more meaningful“radiation damage age”can be obtained.展开更多
The Raman spectra of the natural end members of the garnet-group minerals, which include pyrope, almandine and spessarite of Fe-Al garnet series and grossularite, andradite and uvarovite of Ca-Fe garnet series, have b...The Raman spectra of the natural end members of the garnet-group minerals, which include pyrope, almandine and spessarite of Fe-Al garnet series and grossularite, andradite and uvarovite of Ca-Fe garnet series, have been studied. Measured Raman spectra of these minerals are reasonably and qualitatively assigned to the intemal modes, translational and rotatory modes of SiO4 tetrahedra,as well as the translational motion of bivalent cations in the X site. The stretch and rotatory Alg modes for the Fe-Al garnet series show obvious Raman shifts as compared with those for the Ca-Fe garnet series, owing to the cations residing in the X site connected with SiO4 tetrahedra by sharing the two edges. The Raman shifts of all members within either of the series are attributed mainly to the properties of cations in the X site for the Fe-Al garnet series and in the Y site for the Ca-Fe gamet series.展开更多
We systematically investigate the optical properties of the InP1-xBix ternary alloys with 0≤x≤2.46%,by using high resolution polarized Raman scattering measurement.Both InP-like and InBi-like optical vibration modes...We systematically investigate the optical properties of the InP1-xBix ternary alloys with 0≤x≤2.46%,by using high resolution polarized Raman scattering measurement.Both InP-like and InBi-like optical vibration modes（LO） are identified in all the samples,suggesting that most of the Bi-atoms are incorporated into the lattice sites to substitute Patoms.And the intensity of the InBi-like Raman mode is positively proportional to the Bi-content.Linear red-shift of the InP-like longitudinal optical vibration mode is observed to be 1.1 cm-1/Bi%,while that of the InP-like optical vibration overtone（2LO） is nearly doubled.In addition,through comparing the（XX） and Z（XY） Raman spectra,longitudinaloptical-plasmon-coupled（LOPC） modes are identified in all the samples,and their intensities are found to be proportional to the electron concentrations.展开更多
The magnetic field in the microwave interaction zone of the fountain atomic clock was measured by stimulated Raman transitions. By measuring the two-photon transition frequency between the Zeeman levels of the two gro...The magnetic field in the microwave interaction zone of the fountain atomic clock was measured by stimulated Raman transitions. By measuring the two-photon transition frequency between the Zeeman levels of the two ground states, we achieved a magnetic field measurement accuracy of the order of 0.28 nT, This method is immune to the Doppler shift and the AC Stark shift. The second order Zeeman shift of the fountain clock is 170.7 × 10^-15, with the uncertainty of 7,2 × 10^-16.展开更多
The Raman–Nath diffraction in acousto–optic effect was studied theoretically and experimentally in the paper. Up to now, each order of diffracted light in Raman–Nath diffraction was still considered simply to be ju...The Raman–Nath diffraction in acousto–optic effect was studied theoretically and experimentally in the paper. Up to now, each order of diffracted light in Raman–Nath diffraction was still considered simply to be just frequency-shifted and to be a plane wave. However, we find that the phase and frequency shifts occur simultaneously and individually in Raman–Nath diffraction. The findings demonstrate that, in addition to the frequency shift, the optical phase of each order of diffracted light is also shifted by the sound wave and fluctuates with the sound wave and is related to the location in the acoustic field from which the diffracted light originates. As a result, the wavefront of each order of diffracted light is modulated to fluctuate spatially and temporally with the sound wave. Obviously, these findings are significant for applications of Raman–Nath diffraction in acousto–optic effect because the optical phase plays an important role in optical coherence technology.展开更多
Phthalate acid esters （PAEs） possess endocrine disruptive effects and can produce reproductive and developmental toxicities. In this paper, both experimental and theoretical studies on FT-IR, Raman and 1H NMR spectr...Phthalate acid esters （PAEs） possess endocrine disruptive effects and can produce reproductive and developmental toxicities. In this paper, both experimental and theoretical studies on FT-IR, Raman and 1H NMR spectra of diethyl phthalate （DEP） have been carried out. The geometrical structure of DEP was optimized at the HF/6-31G＊, HF/6-311G＊＊, B3LYP/6-31G＊, and B3LYP/6-31 IG＊＊ levels, respectively. The harmonic vibrational frequencies, IR intensity, Raman activity and 1H NMR chemical shifts have been computed at the B3LYP/6-31G＊ and B3LYP/6-311G＊＊ levels. Anharmonic corrections to frequencies were obtained by means of second-order perturbation theory （PT2） at the B3LYP/6-31G＊ level. Based on potential energy distribution （PED）, the vibrational assignments have also been performed. The theoretical calculation values were compared with the experimental observations and the results indicate they are in excellent agreement.展开更多
The strain transfer behavior of graphene and black phosphorus heterostructure on fexible substrates plays a crucial role in the functionality and regulation of the device.Specifically,it is imperative to investigate t...The strain transfer behavior of graphene and black phosphorus heterostructure on fexible substrates plays a crucial role in the functionality and regulation of the device.Specifically,it is imperative to investigate the anisotropy associated with strain transfer at the black phosphorus interface.In this study,a sample transfer method was proposed to prevent the contact of black phosphorus with water,achieving monolayer graphene and few-layer black phosphorus heterostructures on a PET flm substrate.Micro-Raman spectroscopy was used to measure the strain of graphene and black phosphorus when the PET flm substrate was under uniaxial tensile loading along the zigzag and armchair directions of black phosphorus,respectively.The Raman shift-strain relationship of black phosphorus was derived,and an interface transfer model was developed for the heterostructure.Based on the model,the strain transfer efficiency of each measuring spot was calculated and the strain transfer mechanism of each layer was analyzed.The results uncover the influence of the anisotropic interlayer properties inside the black phosphorus on the strain transfer behavior in the heterostructure on the flexible substrate.展开更多
基金Project supported by the Fundamental Research Funds for the Central Universities,China (Grant No. K50511250002)the National Key Science & Technology Special Project,China (Grant No. 2008ZX01002-002)+1 种基金the Major Program and State Key Program of the National Natural Science Foundation of China (Grant Nos. 60890191 and 60736033)the Science Fund for Youths Scholars (Grant Nos. 61204006)
文摘In this paper,Raman shifts of a-plane GaN layers grown on r-plane sapphire substrates by low-pressure metal-organic chemical vapor deposition（LPMOCVD） are investigated.We compare the crystal qualities and study the relationships between Raman shift and temperature for conventional a-plane GaN epilayer and insertion AlN/AlGaN superlattice layers for a-plane GaN epilayer using temperature-dependent Raman scattering in a temperature range from 83 K to 503 K.The temperature-dependences of GaN phonon modes（A1（TO）,E2（high）,and E1（TO）） and the linewidths of E2（high） phonon peak are studied.The results indicate that there exist two mechanisms between phonon peaks in the whole temperature range,and the relationship can be fitted to the pseudo-Voigt function.From analytic results we find a critical temperature existing in the relationship,which can characterize the anharmonic effects of a-plane GaN in different temperature ranges.In the range of higher temperature,the relationship exhibits an approximately linear behavior,which is consistent with the analyzed results theoretically.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.61405172,61405173,and 61275093)the Natural Science Foundation of Hebei Province,China(Grant No.F2014203194)+1 种基金the College Science Research Program of Hebei Province,China(Grant No.QN20131044)the Program of Independent Research for the Young Teachers of Yanshan University of China(Grant No.13LGB017)
文摘Raman soliton self-frequency shifted to mid-infrared band（λ 〉 2 μm） has been achieved in an air-silica microstructure fiber（MF）. The MF used in our experiment has an elliptical core with diameters of 1.08 and 2.48 μm for fast and slow axis. Numerical simulation shows that each fundamental orthogonal polarization mode has two wide-spaced λZDW and theλZDW pairs located at 701/2110 nm and 755/2498 nm along the fast and slow axis, respectively. Using 810-nm Ti：sapphire femtosecond laser as pump, when the output power varies from 0.3 to 0.5 W, the furthest red-shift Raman solitons in both fast and slow axis shift from near-infrared band to mid-infrared band, reaching as far as 2030 and 2261 nm. Also, midinfrared Raman solitons can always be generated for pump wavelength longer than 790 nm if output pump power reaches0.5 W. Specifically, with pump power at 0.5 W, the mid-infrared soliton in slow axis shifts from 2001 to 2261 nm when the pump changes from 790 nm to 810 nm. This means only a 20 nm change of pump results in 260 nm tunability of a mid-infrared soliton.
文摘Nitrogen hydrate samples were synthesized using liquid nitrogen and powder ice at 16 MPa and 253 K. Confocal laser Raman spectroscopy was used to investigate the characteristics of nitrogen clathrate hydrates. The results show that the Raman peaks of N-N and O-H stretching vibration in nitrogen hydrates are observed at 2322.4 and 3092.1 cm^-1, respectively, which are very similar to those in natural air clathrate hydrates. For comparison, we measured the Raman peaks of N-N stretching vibration both in liquid nitrogen and nitrogen molecules saturated water, which appear at 2326.6 and 2325.0 cm^-1, respectively. The Raman spectroscopic observations on the dissociation process suggest that nitrogen molecules occupy both the large and small cages in nitrogen clathrate hydrates. However, only one Raman peak is observed for N N stretching vibration because the difference of the environment of nitrogen molecules between large and small cages is too small to be differentiated by Raman spectroscopy.
基金the National Natural Science Foundation of China(No.21375087)the Natural Science Foundation of Shanghai(No.13ZR1422100)
文摘Surface-enhanced Raman spectroscopy（SERS） is an intense ongoing hot topic because it is an attractive tool for sensing or detecting molecules in trace amounts. Despite its high specificity and sensitivity, the SERS technique has not been established as a routine analytic method most likely due to the low reproducibility of the SERS signal. This review considers the influence factors to produce the poor reproducibility during the SERS measurement. This review starts with the discussion of calculation of surface-enhanced Raman intensity in order to explain the reason why it is so difficult to achieve a high reproducibility of SERS measurement from the origin of enhancement mechanism. Then we focus on the fabrication of SERS substrates generally including two types：① single particles and ② arrays on substrate that are directly used to detect molecules or other components.In addition, we discuss the molecule factors and optical system for the reproducibility for sample-to-sample or spot-to-spot on a substrate. In the final part of this review, some effects resulting in the irreproducibility of Raman bands＇ position from recent literatures are discussed.
基金supported by funds from the Strategic Priority Research Program(B)of the Chinese Academy of Sciences(XDB 41000000)the National Natural Science Foundation of China(41973002,41772187)+1 种基金the Fundamental Research Funds for the Central UniversitiesNatural Sciences and Engineering Research Council of Canada(NSERC)Discovery Grant to J.M Hanchar(RGPIN/004649-2015)。
文摘Due to its ubiquitous occurrence in igneous,metamorphic,and sedimentary rocks and its wide application in geochronology and geochemistry,zircon has become the most widely used accessory mineral in the geological community.Nevertheless,the decay of U and Th causes radiation damage to the zircon structure,resulting in various degrees of metamictization,which can affect the accuracy of U–Pb dates and Hf and O isotope results.If the degree of zircon radiation damage can be quantified,the influence on geochemical analyses can be evaluated,and the results can be corrected more precisely.In this paper,synthetic and natural zircon crystals with different crystallization ages were selected for Raman spectroscopy analysis,cathodoluminescence imaging,and determination of the U and Th concentrations.The results show that Raman FWHM(full width at half bandmaximum)and Raman shift correlate with alpha dose(Da)ofzirconsfollowingtheseequations,FWHM=44.36(±2.32)×[1-exp(-2.74×Da)]-+1.7(±0.19),Raman Shift=-6.53×Da+1007.69.Analysis of synthetic zircon crystals shows that doped REEs(rare earth elements and P)can also lead to an increase in the FWHM.However,this effect can be ignored for natural zircon samples with REE contents at a normal level of hundreds to a few thousand ppm.The FWHM and Raman shift can be used as proxies to measure the degree of zircon radiation damage.Using the updated equations to calculate the latest age when zircon began to accumulate radiation damage,a more accurate and more meaningful“radiation damage age”can be obtained.
文摘The Raman spectra of the natural end members of the garnet-group minerals, which include pyrope, almandine and spessarite of Fe-Al garnet series and grossularite, andradite and uvarovite of Ca-Fe garnet series, have been studied. Measured Raman spectra of these minerals are reasonably and qualitatively assigned to the intemal modes, translational and rotatory modes of SiO4 tetrahedra,as well as the translational motion of bivalent cations in the X site. The stretch and rotatory Alg modes for the Fe-Al garnet series show obvious Raman shifts as compared with those for the Ca-Fe garnet series, owing to the cations residing in the X site connected with SiO4 tetrahedra by sharing the two edges. The Raman shifts of all members within either of the series are attributed mainly to the properties of cations in the X site for the Fe-Al garnet series and in the Y site for the Ca-Fe gamet series.
基金Project supported by the National Basic Research Program of China(Grant No.2014CB643903)the National Natural Science Foundation of China(Grant Nos.61225021,11474272.and 11174272)
文摘We systematically investigate the optical properties of the InP1-xBix ternary alloys with 0≤x≤2.46%,by using high resolution polarized Raman scattering measurement.Both InP-like and InBi-like optical vibration modes（LO） are identified in all the samples,suggesting that most of the Bi-atoms are incorporated into the lattice sites to substitute Patoms.And the intensity of the InBi-like Raman mode is positively proportional to the Bi-content.Linear red-shift of the InP-like longitudinal optical vibration mode is observed to be 1.1 cm-1/Bi%,while that of the InP-like optical vibration overtone（2LO） is nearly doubled.In addition,through comparing the（XX） and Z（XY） Raman spectra,longitudinaloptical-plasmon-coupled（LOPC） modes are identified in all the samples,and their intensities are found to be proportional to the electron concentrations.
基金supported by the National Basic Research Program of China (Grant No. 2005CB724506)the National Natural Science Foundation of China (Grant Nos. 10604058 and 10974215)the Open Research Fund of State Key Laboratory of Precision Spectroscope
文摘The magnetic field in the microwave interaction zone of the fountain atomic clock was measured by stimulated Raman transitions. By measuring the two-photon transition frequency between the Zeeman levels of the two ground states, we achieved a magnetic field measurement accuracy of the order of 0.28 nT, This method is immune to the Doppler shift and the AC Stark shift. The second order Zeeman shift of the fountain clock is 170.7 × 10^-15, with the uncertainty of 7,2 × 10^-16.
基金Project supported by the National Natural Science Foundation of China(Grant No.61178089)the Science and Technology Program of the Educational Office of Fujian Province of China(Grant Nos.JB12012 and JB13003)
文摘The Raman–Nath diffraction in acousto–optic effect was studied theoretically and experimentally in the paper. Up to now, each order of diffracted light in Raman–Nath diffraction was still considered simply to be just frequency-shifted and to be a plane wave. However, we find that the phase and frequency shifts occur simultaneously and individually in Raman–Nath diffraction. The findings demonstrate that, in addition to the frequency shift, the optical phase of each order of diffracted light is also shifted by the sound wave and fluctuates with the sound wave and is related to the location in the acoustic field from which the diffracted light originates. As a result, the wavefront of each order of diffracted light is modulated to fluctuate spatially and temporally with the sound wave. Obviously, these findings are significant for applications of Raman–Nath diffraction in acousto–optic effect because the optical phase plays an important role in optical coherence technology.
基金Financially supported by the National Natural Science Foundation of China (41071319, 20977046)the Fundamental Research Funds for the Central Universities of China (1112021101)
文摘Phthalate acid esters （PAEs） possess endocrine disruptive effects and can produce reproductive and developmental toxicities. In this paper, both experimental and theoretical studies on FT-IR, Raman and 1H NMR spectra of diethyl phthalate （DEP） have been carried out. The geometrical structure of DEP was optimized at the HF/6-31G＊, HF/6-311G＊＊, B3LYP/6-31G＊, and B3LYP/6-31 IG＊＊ levels, respectively. The harmonic vibrational frequencies, IR intensity, Raman activity and 1H NMR chemical shifts have been computed at the B3LYP/6-31G＊ and B3LYP/6-311G＊＊ levels. Anharmonic corrections to frequencies were obtained by means of second-order perturbation theory （PT2） at the B3LYP/6-31G＊ level. Based on potential energy distribution （PED）, the vibrational assignments have also been performed. The theoretical calculation values were compared with the experimental observations and the results indicate they are in excellent agreement.
基金supported by the National Natural Science Foundation of China(Grant Nos.12125203,12021002,and 12041201).
文摘The strain transfer behavior of graphene and black phosphorus heterostructure on fexible substrates plays a crucial role in the functionality and regulation of the device.Specifically,it is imperative to investigate the anisotropy associated with strain transfer at the black phosphorus interface.In this study,a sample transfer method was proposed to prevent the contact of black phosphorus with water,achieving monolayer graphene and few-layer black phosphorus heterostructures on a PET flm substrate.Micro-Raman spectroscopy was used to measure the strain of graphene and black phosphorus when the PET flm substrate was under uniaxial tensile loading along the zigzag and armchair directions of black phosphorus,respectively.The Raman shift-strain relationship of black phosphorus was derived,and an interface transfer model was developed for the heterostructure.Based on the model,the strain transfer efficiency of each measuring spot was calculated and the strain transfer mechanism of each layer was analyzed.The results uncover the influence of the anisotropic interlayer properties inside the black phosphorus on the strain transfer behavior in the heterostructure on the flexible substrate.
