Si-based multilayer structures are widely used in current microelectronics. During their preparation, some inhomogeneous residual stress is induced, resulting in competition between interface mismatching and surface e...Si-based multilayer structures are widely used in current microelectronics. During their preparation, some inhomogeneous residual stress is induced, resulting in competition between interface mismatching and surface energy and even leading to structure failure. This work presents a methodological study on the measurement of residual stress in a multi-layer semiconductor heterostructure. Scanning electron microscopy（SEM）, micro-Raman spectroscopy（MRS）, and transmission electron microscopy（TEM） were applied to measure the geometric parameters of the multilayer structure. The relationship between the Raman spectrum and the stress/strain on the [100] and [110] crystal orientations was determined to enable surface and crosssection residual stress analyses, respectively. Based on the Raman mapping results, the distribution of residual stress along the depth of the multi-layer heterostructure was successfully obtained.展开更多
We study the spontaneous Raman scattering （RS） in taper-drawn micro/nano-fibers （MNFs） by employing the photon counting technique. The spectra of RS in five MNFs, which are fabricated by using different heating fl...We study the spontaneous Raman scattering （RS） in taper-drawn micro/nano-fibers （MNFs） by employing the photon counting technique. The spectra of RS in five MNFs, which are fabricated by using different heating flames （hydrogen flame or butane flame） and with different diameters, are measured within a frequency shift range of 1435 cm- 1_3200 cm- 1. From the measured spectra, we observe the RS peaks originated from silica and a unique RS peak with a frequency shift of - 2905 cm-1 （- 87.2 THz）. Unlike the former ones, the latter one is not observable in conventional optical fibers. Furthermore, the unique peak becomes obvious and starts to rapidly increase with the decrease of the diameter of MNFs when the diameter is smaller than 2 μm, and the intensity of the unique peak significantly depends on the heating flame used in the fabricating process. Our investigation is useful for the entanglement generation or optical sensing using taper-drawn MNFs.展开更多
It is important to acquire the composition of Si1-xGex layer, especially that with high Ge content, epitaxied on Si substrate. Two nondestructive examination methods, double crystals X-ray diffraction （DCXRD） and mi...It is important to acquire the composition of Si1-xGex layer, especially that with high Ge content, epitaxied on Si substrate. Two nondestructive examination methods, double crystals X-ray diffraction （DCXRD） and micro-Raman measurement, were introduced comparatively to determine x value in Si1-xGex layer, which show that while the two methods are consistent with each other when x is low, the results obtained from double crystals X-ray diffraction are not credible due to the large strain relaxation occurring in Si1-xGex layers when Ge content is higher than about 20%. Micro-Raman measurement is more appropriate for determining high Ge content than DCXRD.展开更多
Roman scattering measurement of （ 1 - x ） GeS2-x Ga2S3 system glasses was conducted in order to understand the microstructural change caused by the addition of Ga2S3 . According to the change of Raman spectra with t...Roman scattering measurement of （ 1 - x ） GeS2-x Ga2S3 system glasses was conducted in order to understand the microstructural change caused by the addition of Ga2S3 . According to the change of Raman spectra with the addition of Ga2S3, two main structural transformations were deduced ： the gradual enhancement of ethane- like structural units S3 Ge- GeS3 （ 250 cm ^- 1） and S3 Ga- GaS3 （270 cm ^- 1 ） and the appearance of charge imbalanced units [ Ga2 S2 （ S1/2 ）4 ]^2- and [Ga（ S1/2 ）4 ]^- . And this change of structural aspect seems to give as a clue to understanding the cause of the increased rare-earth solubility.展开更多
To investigate the damage profiles of high-fluence low-energy proton irradiation on superconducting materials and related devices, Raman characterization and electrical transport measurement of 40-keV-proton irradiate...To investigate the damage profiles of high-fluence low-energy proton irradiation on superconducting materials and related devices, Raman characterization and electrical transport measurement of 40-keV-proton irradiated YBa_2Cu_3O_(7-x)(YBCO) thin films are carried out. From micro-Raman spectroscopy and x-ray diffraction studies, the main component of proton-radiation-induced defects is found to be the partial transition of superconducting orthorhombic phase to the semiconducting tetragonal phase and non-superconducting secondary phase. The results indicate that the defects induced in the conducting CuO_2 planes, such as increased oxygen vacancies and interstitials, can result in an increase in the resistivity but a decrease in the transition temperature TCwith the increase in the fluence of proton irradiation, which is confirmed in the electrical transport measurements. Especially, zero-resistance temperature TC_0 is not observed at a fluence of 10^(15)p/cm^2.Furthermore, the variation of activation energy U_0 can be explained by the plastic-flux creep theory, which indicates that the plastic deformation and entanglement of vortices in a weakly pinned vortex liquid are caused by disorders of point-like defects. Point-like disorders are demonstrated to be the main contribution to the low-energy proton radiation damage in YBCO thin films. These disorders are likely to cause flux creep by thermally assisted flux flow, which may increase noise and reduce the precision of superconducting devices.展开更多
A series of cubic SiC single crystals were heteroepitaxially grown by the hot-wall chemical vapor deposition (CVD) using a HMDS-C3H8-H2 system on 2 inch silicon substrates with the orientations of (100), (111), (110) ...A series of cubic SiC single crystals were heteroepitaxially grown by the hot-wall chemical vapor deposition (CVD) using a HMDS-C3H8-H2 system on 2 inch silicon substrates with the orientations of (100), (111), (110) and (211), respectively. Even though an initial carbonization was carried out to reduce the large lattice mismatch, residual stress could not be completely relieved, partly also due to the difference of their thermal expansion coefficients. Raman scattering studies for the specimens were performed to estimate the internal stress in the SiC epilayer and the substrate. Raman spectra were mapped out on the sample surface as well as on the cross section using an automated x-y stage with a spatial resolution capable of 100 nm. For all the samples, two Raman peaks corresponding to the transverse optical (TO) and longitudinal optical (LO) phonon modes were observed, even though the intensity varied with the polarization configurations. In the SiC epilayers, tensile stresses decrease away from the interface, while compressive stresses exist in the substrate, with the magnitudes dependent on the growth orientation. The lattice strains were discussed in terms of the elastic deformation theory for the comparison.展开更多
Polarized micro-Raman spectra of a 0.65PbMgl/3Nb2/303 0.35PbTiO3 （0.65PMN-0.35PT） single crystal poled in the [001] direction are obtained in a wide frequency range （50 2000 cm^-1） at different temperatures. The b...Polarized micro-Raman spectra of a 0.65PbMgl/3Nb2/303 0.35PbTiO3 （0.65PMN-0.35PT） single crystal poled in the [001] direction are obtained in a wide frequency range （50 2000 cm^-1） at different temperatures. The best fit to the Raman spectrum at 77 K is achieved using 17 Lorenzians to convolute into it, and this is proved to be a reasonable fit. According to the group theory and selection rules of overtone and combinational modes, apart from the seven Raman modes that are from first-order Raman scattering, the remaining ones are attributed to being from second-order Raman scattering. A comparison between the experimental results and theoretical predictions shows that they are in satisfactory agreement with each other. Our results indicate that at 77 K the sample belongs to the rhombohedral symmetry with the C^53v（R3m） space group （Z = 1）. In our study, on heating, the 0.65PMN 0.35PT single crystal undergoes a rhombohedral → tetragonal → cubic phase transition sequence. The two phase transitions occur at 340 and 440 K, which correspond to the disappearance of the soft mode near 106 cm-1 recorded in VV polarization and the vanishing of the band around 780 cm^-1 in VH polarization, respectively.展开更多
In this work, we are interesting in the measurement of thermal conductivity (on the surface and in-depth) of Porous silicon by the micro-Raman spectroscopy. This direct method (micro-Raman spectroscopy) enabled us to ...In this work, we are interesting in the measurement of thermal conductivity (on the surface and in-depth) of Porous silicon by the micro-Raman spectroscopy. This direct method (micro-Raman spectroscopy) enabled us to develop a systematic means of investigation of the morphology and the thermal conductivity of Porous silicon oxidized or no. The thermal conductivity is studied according to the parameters of anodization and fraction of silicon oxidized. Thermal transport in the porous silicon layers is limited by its porous nature and the blocking of transport in the silicon skeleton what supports its use in the thermal sensors.展开更多
The Darhib mine is one of the several talc deposits in the Hamata area of southeastern Egypt. Several specimens of minerals coming from this mine were subjected to complementary investigation by micro-Raman spectromet...The Darhib mine is one of the several talc deposits in the Hamata area of southeastern Egypt. Several specimens of minerals coming from this mine were subjected to complementary investigation by micro-Raman spectrometry and scanning electron microscopy. The difficulty in their identification is the appearance of most of them: they are all very small and only visible under the mineral binocular microscope(×10 - ×40). They appear as small crystals in fissures and holes and a visual determination on colour and crystal gives only a guess of what kind of mineral it could be. Therefore, only after analyzing them by micro-Raman and scanning electron microscopy it was possible to identify their structure and they can be divided in three main groups: one is quite generic and several minerals of different species were identified, such as quartz, talc, mottramite and chrysocolla, very common in the talc mine (these ones are Si-based minerals);the other one is constituted by four samples which are Zn and/or Cu rich, which means minerals of the rosasite or aurichalcite groups;the last group is constituted by two samples containing mainly Pb..展开更多
基金supported by the National Basic Research Program of China (Grant 2012CB937500)the National Natural Science Foundation of China (Grants 11422219, 11227202, 11372217, 11272232)+1 种基金the Program for New Century Excellent Talents in University (Grant NCET-13)China Scholarship Council (201308120092)
文摘Si-based multilayer structures are widely used in current microelectronics. During their preparation, some inhomogeneous residual stress is induced, resulting in competition between interface mismatching and surface energy and even leading to structure failure. This work presents a methodological study on the measurement of residual stress in a multi-layer semiconductor heterostructure. Scanning electron microscopy（SEM）, micro-Raman spectroscopy（MRS）, and transmission electron microscopy（TEM） were applied to measure the geometric parameters of the multilayer structure. The relationship between the Raman spectrum and the stress/strain on the [100] and [110] crystal orientations was determined to enable surface and crosssection residual stress analyses, respectively. Based on the Raman mapping results, the distribution of residual stress along the depth of the multi-layer heterostructure was successfully obtained.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.11304222 and 11527808)the State Key Development Program for Basic Research of China(Grant No.2014CB340103)
文摘We study the spontaneous Raman scattering （RS） in taper-drawn micro/nano-fibers （MNFs） by employing the photon counting technique. The spectra of RS in five MNFs, which are fabricated by using different heating flames （hydrogen flame or butane flame） and with different diameters, are measured within a frequency shift range of 1435 cm- 1_3200 cm- 1. From the measured spectra, we observe the RS peaks originated from silica and a unique RS peak with a frequency shift of - 2905 cm-1 （- 87.2 THz）. Unlike the former ones, the latter one is not observable in conventional optical fibers. Furthermore, the unique peak becomes obvious and starts to rapidly increase with the decrease of the diameter of MNFs when the diameter is smaller than 2 μm, and the intensity of the unique peak significantly depends on the heating flame used in the fabricating process. Our investigation is useful for the entanglement generation or optical sensing using taper-drawn MNFs.
基金This work is supported by the National Natural Science Foundation of China （Grant Nos. 60336010 ＆ 90401001）973 Program （Grant No. TG 2000036603）the Student Innovation Program of CAS （No. 1731000500010）.
文摘It is important to acquire the composition of Si1-xGex layer, especially that with high Ge content, epitaxied on Si substrate. Two nondestructive examination methods, double crystals X-ray diffraction （DCXRD） and micro-Raman measurement, were introduced comparatively to determine x value in Si1-xGex layer, which show that while the two methods are consistent with each other when x is low, the results obtained from double crystals X-ray diffraction are not credible due to the large strain relaxation occurring in Si1-xGex layers when Ge content is higher than about 20%. Micro-Raman measurement is more appropriate for determining high Ge content than DCXRD.
文摘Roman scattering measurement of （ 1 - x ） GeS2-x Ga2S3 system glasses was conducted in order to understand the microstructural change caused by the addition of Ga2S3 . According to the change of Raman spectra with the addition of Ga2S3, two main structural transformations were deduced ： the gradual enhancement of ethane- like structural units S3 Ge- GeS3 （ 250 cm ^- 1） and S3 Ga- GaS3 （270 cm ^- 1 ） and the appearance of charge imbalanced units [ Ga2 S2 （ S1/2 ）4 ]^2- and [Ga（ S1/2 ）4 ]^- . And this change of structural aspect seems to give as a clue to understanding the cause of the increased rare-earth solubility.
基金Project supported by the National Natural Science Foundation of China(Grant No.61473023)the Aerospace Science and Technology Innovation Fund,CASCInternational S&T Cooperation Program of China(ISTCP)(Grant No.2015DFR80190)
文摘To investigate the damage profiles of high-fluence low-energy proton irradiation on superconducting materials and related devices, Raman characterization and electrical transport measurement of 40-keV-proton irradiated YBa_2Cu_3O_(7-x)(YBCO) thin films are carried out. From micro-Raman spectroscopy and x-ray diffraction studies, the main component of proton-radiation-induced defects is found to be the partial transition of superconducting orthorhombic phase to the semiconducting tetragonal phase and non-superconducting secondary phase. The results indicate that the defects induced in the conducting CuO_2 planes, such as increased oxygen vacancies and interstitials, can result in an increase in the resistivity but a decrease in the transition temperature TCwith the increase in the fluence of proton irradiation, which is confirmed in the electrical transport measurements. Especially, zero-resistance temperature TC_0 is not observed at a fluence of 10^(15)p/cm^2.Furthermore, the variation of activation energy U_0 can be explained by the plastic-flux creep theory, which indicates that the plastic deformation and entanglement of vortices in a weakly pinned vortex liquid are caused by disorders of point-like defects. Point-like disorders are demonstrated to be the main contribution to the low-energy proton radiation damage in YBCO thin films. These disorders are likely to cause flux creep by thermally assisted flux flow, which may increase noise and reduce the precision of superconducting devices.
文摘A series of cubic SiC single crystals were heteroepitaxially grown by the hot-wall chemical vapor deposition (CVD) using a HMDS-C3H8-H2 system on 2 inch silicon substrates with the orientations of (100), (111), (110) and (211), respectively. Even though an initial carbonization was carried out to reduce the large lattice mismatch, residual stress could not be completely relieved, partly also due to the difference of their thermal expansion coefficients. Raman scattering studies for the specimens were performed to estimate the internal stress in the SiC epilayer and the substrate. Raman spectra were mapped out on the sample surface as well as on the cross section using an automated x-y stage with a spatial resolution capable of 100 nm. For all the samples, two Raman peaks corresponding to the transverse optical (TO) and longitudinal optical (LO) phonon modes were observed, even though the intensity varied with the polarization configurations. In the SiC epilayers, tensile stresses decrease away from the interface, while compressive stresses exist in the substrate, with the magnitudes dependent on the growth orientation. The lattice strains were discussed in terms of the elastic deformation theory for the comparison.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.10674171 and 10874236)
文摘Polarized micro-Raman spectra of a 0.65PbMgl/3Nb2/303 0.35PbTiO3 （0.65PMN-0.35PT） single crystal poled in the [001] direction are obtained in a wide frequency range （50 2000 cm^-1） at different temperatures. The best fit to the Raman spectrum at 77 K is achieved using 17 Lorenzians to convolute into it, and this is proved to be a reasonable fit. According to the group theory and selection rules of overtone and combinational modes, apart from the seven Raman modes that are from first-order Raman scattering, the remaining ones are attributed to being from second-order Raman scattering. A comparison between the experimental results and theoretical predictions shows that they are in satisfactory agreement with each other. Our results indicate that at 77 K the sample belongs to the rhombohedral symmetry with the C^53v（R3m） space group （Z = 1）. In our study, on heating, the 0.65PMN 0.35PT single crystal undergoes a rhombohedral → tetragonal → cubic phase transition sequence. The two phase transitions occur at 340 and 440 K, which correspond to the disappearance of the soft mode near 106 cm-1 recorded in VV polarization and the vanishing of the band around 780 cm^-1 in VH polarization, respectively.
文摘In this work, we are interesting in the measurement of thermal conductivity (on the surface and in-depth) of Porous silicon by the micro-Raman spectroscopy. This direct method (micro-Raman spectroscopy) enabled us to develop a systematic means of investigation of the morphology and the thermal conductivity of Porous silicon oxidized or no. The thermal conductivity is studied according to the parameters of anodization and fraction of silicon oxidized. Thermal transport in the porous silicon layers is limited by its porous nature and the blocking of transport in the silicon skeleton what supports its use in the thermal sensors.
文摘The Darhib mine is one of the several talc deposits in the Hamata area of southeastern Egypt. Several specimens of minerals coming from this mine were subjected to complementary investigation by micro-Raman spectrometry and scanning electron microscopy. The difficulty in their identification is the appearance of most of them: they are all very small and only visible under the mineral binocular microscope(×10 - ×40). They appear as small crystals in fissures and holes and a visual determination on colour and crystal gives only a guess of what kind of mineral it could be. Therefore, only after analyzing them by micro-Raman and scanning electron microscopy it was possible to identify their structure and they can be divided in three main groups: one is quite generic and several minerals of different species were identified, such as quartz, talc, mottramite and chrysocolla, very common in the talc mine (these ones are Si-based minerals);the other one is constituted by four samples which are Zn and/or Cu rich, which means minerals of the rosasite or aurichalcite groups;the last group is constituted by two samples containing mainly Pb..
