The acidity of atmospheric aerosols influences fundamental physicochemical processes that affect climate and human health.We recently developed a novel and facilewater-probebased method for directly measuring of the p...The acidity of atmospheric aerosols influences fundamental physicochemical processes that affect climate and human health.We recently developed a novel and facilewater-probebased method for directly measuring of the pH for micrometer-size droplets,providing a promising technique to better understand aerosol acidity in the atmosphere.The complex chemical composition of fine particles in the ambient air,however,poses certain challenges to using a water-probe for pH measurement,including interference from interactions between compositions and the influence of similar compositions on water structure.To explore the universality of our method,it was employed to measure the pH of ammonium,nitrate,carbonate,sulfate,and chloride particles.The pH of particles covering a broad range(0–14)were accurately determined,thereby demonstrating that our method can be generally applied,even to alkaline particles.Furthermore,a standard spectral library was developed by integrating the standard spectra of common hydrated ions extracted through the waterprobe.The library can be employed to identify particle composition and overcome the spectral overlap problem resulting from similar effects.Using the spectral library,all ions were identified and their concentrations were determined,in turn allowing successful pH measurement of multicomponent(ammonium-sulfate-nitrate-chloride)particles.Insights into the synergistic effect of Cl^(–),NO_(3)^(–),and NH_(4)^(+)depletion obtained with our approach revealed the interplay between pH and volatile partitioning.Given the ubiquity of component partitioning and pH variation in particles,the water probemay provide a new perspective on the underlying mechanisms of aerosol aging and aerosol–cloud interaction.展开更多
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
Heterogeneous reactions on the aerosol particle surface in the atmosphere play important roles in air pollution, climate change, and global biogeochemical cycles. However, the reported uptake coefficients of heterogen...Heterogeneous reactions on the aerosol particle surface in the atmosphere play important roles in air pollution, climate change, and global biogeochemical cycles. However, the reported uptake coefficients of heterogeneous reactions usually have large variations and may not be relevant to real atmospheric conditions. One of the major reasons for this is the use of bulk samples in laboratory experiments, while particles in the atmosphere are suspended individually. A number of technologies have been developed recently to study heterogeneous reactions on the surfaces of individual particles. Precise measurements on the reactive surface area, volume, and morphology of individual particles are necessary for calculating the uptake coefficient, quantifying reactants and products, and understanding the reaction mechanism better. In this study, for the first time we used synchrotron radiation X-ray computed tomography（XCT） and micro-Raman spectrometry to measure individual CaCO_3 particle morphology, with sizes ranging from 3.5–6.5 μm. Particle surface area and volume were calculated using a reconstruction method based on software threedimensional（3-D） rendering. The XCT was first validated with high-resolution fieldemission scanning electron microscopy（FE-SEM） to acquire accurate CaCO_3 particle surface area and volume estimates. Our results showed an average difference of only 6.1% in surface area and 3.2% in volume measured either by micro-Raman spectrometry or X-ray tomography. X-ray tomography and FE-SEM can provide more morphological details of individual Ca CO3 particles than micro-Raman spectrometry. This study demonstrated that X-ray computed tomography and micro-Raman spectrometry can precisely measure the surface area, volume, and morphology of an individual particle.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
We developed a set of in-situ Micro-Raman spectroscopy system for autoclave experimental apparatus because of the scientific significance of in-situ Micro-Raman spectroscopy system under the high-pressure hydrothermal...We developed a set of in-situ Micro-Raman spectroscopy system for autoclave experimental apparatus because of the scientific significance of in-situ Micro-Raman spectroscopy system under the high-pressure hydrothermal condition.We used this system to measure the Raman spectrum of water-fluid and quartz crystal at the temperature ranging from 125 to 420℃.The signal-tonoise ratio of the Raman signal is good.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 irradiated...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_(2)Cu_(3)O_(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
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
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
With the application of strain engineering in microelectronics,complex stress states are introduced into advanced semiconductor devices.However,there is still a lack of effective metrology for the decoupling analysis ...With the application of strain engineering in microelectronics,complex stress states are introduced into advanced semiconductor devices.However,there is still a lack of effective metrology for the decoupling analysis of the complex stress states in semiconductor materials.This paper presents an investigation on the 2-axis stress component decoupling of{100}monocrystalline silicon(c-Si)by using oblique backscattering micro-Raman spectroscopy.A spectral-mechanical model was established,and two practicable methods for actual stress decoupling analyses were proposed.The verification experiments demonstrated the correctness and applicability of the methods proposed in this paper.展开更多
Research on the laser ablation behavior of SiC ceramics has great significance for the improvement of their anti-laser ability as high-performance mirrors in space and lasers, or the laser surface micro-machining tech...Research on the laser ablation behavior of SiC ceramics has great significance for the improvement of their anti-laser ability as high-performance mirrors in space and lasers, or the laser surface micro-machining technology as electronic components in micro-electron mechanical systems (MEMS). In this work, the laser ablation of SiC ceramics has been performed by using laser pulses of 12 ns duration at 1064 nm. The laser induced damage threshold (LIDT) below 0.1 J/cm(2) was obtained by 1-on-1 mode and its damage morphology appeared in the form of 'burning crater' with a clear boundary. Micro-Raman mapping technique was first introduced in our study on the laser ablation mechanisms of SiC surface by identifying physical and chemical changes between uninjured and laser-ablated areas. It has been concluded that during the ablation process, SiC surface mainly underwent decomposition to the elemental Si and C, accompanied by some transformation of crystal orientation. The oxidation of SiC also took place but only in small amount on the edges of target region, while there was no hint of SiO2 in the center with higher energy density, maybe because of deficiency of O-2 atmosphere in the ablated area, elimination of SiO2 by carbon at 1505 degrees C, or evaporating at 2230 degrees C.展开更多
基金supported by the National Natural Science Foundation of China(No.91844000)China Postdoctoral Science Foundation(No.2020M670048).
文摘The acidity of atmospheric aerosols influences fundamental physicochemical processes that affect climate and human health.We recently developed a novel and facilewater-probebased method for directly measuring of the pH for micrometer-size droplets,providing a promising technique to better understand aerosol acidity in the atmosphere.The complex chemical composition of fine particles in the ambient air,however,poses certain challenges to using a water-probe for pH measurement,including interference from interactions between compositions and the influence of similar compositions on water structure.To explore the universality of our method,it was employed to measure the pH of ammonium,nitrate,carbonate,sulfate,and chloride particles.The pH of particles covering a broad range(0–14)were accurately determined,thereby demonstrating that our method can be generally applied,even to alkaline particles.Furthermore,a standard spectral library was developed by integrating the standard spectra of common hydrated ions extracted through the waterprobe.The library can be employed to identify particle composition and overcome the spectral overlap problem resulting from similar effects.Using the spectral library,all ions were identified and their concentrations were determined,in turn allowing successful pH measurement of multicomponent(ammonium-sulfate-nitrate-chloride)particles.Insights into the synergistic effect of Cl^(–),NO_(3)^(–),and NH_(4)^(+)depletion obtained with our approach revealed the interplay between pH and volatile partitioning.Given the ubiquity of component partitioning and pH variation in particles,the water probemay provide a new perspective on the underlying mechanisms of aerosol aging and aerosol–cloud interaction.
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supported by the Chinese Ministry of Science and Technology(No.2008AA062503)the National Natural Science Foundation Committee of China(Nos.41421064,20637020)the China Postdoctoral Science Foundation(No.20100470166)
文摘Heterogeneous reactions on the aerosol particle surface in the atmosphere play important roles in air pollution, climate change, and global biogeochemical cycles. However, the reported uptake coefficients of heterogeneous reactions usually have large variations and may not be relevant to real atmospheric conditions. One of the major reasons for this is the use of bulk samples in laboratory experiments, while particles in the atmosphere are suspended individually. A number of technologies have been developed recently to study heterogeneous reactions on the surfaces of individual particles. Precise measurements on the reactive surface area, volume, and morphology of individual particles are necessary for calculating the uptake coefficient, quantifying reactants and products, and understanding the reaction mechanism better. In this study, for the first time we used synchrotron radiation X-ray computed tomography（XCT） and micro-Raman spectrometry to measure individual CaCO_3 particle morphology, with sizes ranging from 3.5–6.5 μm. Particle surface area and volume were calculated using a reconstruction method based on software threedimensional（3-D） rendering. The XCT was first validated with high-resolution fieldemission scanning electron microscopy（FE-SEM） to acquire accurate CaCO_3 particle surface area and volume estimates. Our results showed an average difference of only 6.1% in surface area and 3.2% in volume measured either by micro-Raman spectrometry or X-ray tomography. X-ray tomography and FE-SEM can provide more morphological details of individual Ca CO3 particles than micro-Raman spectrometry. This study demonstrated that X-ray computed tomography and micro-Raman spectrometry can precisely measure the surface area, volume, and morphology of an individual particle.
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.
基金supported by the National Key R&D Program of China(Grant No.2016YFC0600104)the Strategic Priority Research Program(B)of the Chinese Academy of Sciences(XDB 18010401)。
文摘We developed a set of in-situ Micro-Raman spectroscopy system for autoclave experimental apparatus because of the scientific significance of in-situ Micro-Raman spectroscopy system under the high-pressure hydrothermal condition.We used this system to measure the Raman spectrum of water-fluid and quartz crystal at the temperature ranging from 125 to 420℃.The signal-tonoise ratio of the Raman signal is good.
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_(2)Cu_(3)O_(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.
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..
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the National Key Research and Development Program of China(Grant No.2018YFB0703500)the National Natural Science Foundation of China(Grant Nos.11827802,11772223,11772227,11890680,and 61727810)。
文摘With the application of strain engineering in microelectronics,complex stress states are introduced into advanced semiconductor devices.However,there is still a lack of effective metrology for the decoupling analysis of the complex stress states in semiconductor materials.This paper presents an investigation on the 2-axis stress component decoupling of{100}monocrystalline silicon(c-Si)by using oblique backscattering micro-Raman spectroscopy.A spectral-mechanical model was established,and two practicable methods for actual stress decoupling analyses were proposed.The verification experiments demonstrated the correctness and applicability of the methods proposed in this paper.
基金funds from the National Natural Science Foundation of China
文摘Research on the laser ablation behavior of SiC ceramics has great significance for the improvement of their anti-laser ability as high-performance mirrors in space and lasers, or the laser surface micro-machining technology as electronic components in micro-electron mechanical systems (MEMS). In this work, the laser ablation of SiC ceramics has been performed by using laser pulses of 12 ns duration at 1064 nm. The laser induced damage threshold (LIDT) below 0.1 J/cm(2) was obtained by 1-on-1 mode and its damage morphology appeared in the form of 'burning crater' with a clear boundary. Micro-Raman mapping technique was first introduced in our study on the laser ablation mechanisms of SiC surface by identifying physical and chemical changes between uninjured and laser-ablated areas. It has been concluded that during the ablation process, SiC surface mainly underwent decomposition to the elemental Si and C, accompanied by some transformation of crystal orientation. The oxidation of SiC also took place but only in small amount on the edges of target region, while there was no hint of SiO2 in the center with higher energy density, maybe because of deficiency of O-2 atmosphere in the ablated area, elimination of SiO2 by carbon at 1505 degrees C, or evaporating at 2230 degrees C.
