GHz burst-mode femtosecond(fs)laser,which emits a series of pulse trains with extremely short intervals of several hundred picoseconds,provides distinct characteristics in materials processing as compared with the con...GHz burst-mode femtosecond(fs)laser,which emits a series of pulse trains with extremely short intervals of several hundred picoseconds,provides distinct characteristics in materials processing as compared with the conventional irradiation scheme of fs laser(single-pulse mode).In this paper,we take advantage of the moderate pulse interval of 205 ps(4.88 GHz)in the burst pulse for high-quality and high-efficiency micromachining of single crystalline sapphire by laser induced plasma assisted ablation(LIPAA).Specifically,the preceding pulses in the burst generate plasma by ablation of copper placed behind the sapphire substrate,which interacts with the subsequent pulses to induce ablation at the rear surface of sapphire substrates.As a result,not only the ablation quality but also the ablation efficiency and the fabrication resolution are greatly improved compared to the other schemes including single-pulse mode fs laser direct ablation,single-pulse mode fs-LIPAA,and nanosecond-LIPAA.展开更多
Rod-shaped PbW O4 microcrystals of length 1 μm were fabricated by a hydrothermal route and subsequent calcination. Pt nanoparticles（NPs） of different contents（0.5 wt%,1 wt% and 2 wt%） were subsequently deposited ...Rod-shaped PbW O4 microcrystals of length 1 μm were fabricated by a hydrothermal route and subsequent calcination. Pt nanoparticles（NPs） of different contents（0.5 wt%,1 wt% and 2 wt%） were subsequently deposited on the PbW O4 microcrystals,producing robust Pt/PbW O4 composite microcrystals. The PbW O4 microcrystals and Pt/PbW O4 photocatalysts were characterized by X-ray diffraction,N2 sorption measurements,scanning electron microscopy,transmission electron microscopy,and X-ray photoelectron,photoluminescence,Fourier-transform infrared,and ultraviolet-visible diffuse reflectance spectroscopies. The photocatalytic performances of the catalysts were evaluated by the consecutive photocatalytic degradation of acid orange II dye. The Pt/PbW O4 composite microcrystals exhibited high photocatalytic activity and stability. The deposition of Pt NPs produced surface plasmon resonance（SPR）,which induced a large visible light absorption. A Pt NP content of 1-2 wt% resulted in an ~2 times increase in photocatalytic activity,compared with the activity of Pt/PbW O4. The crystal structure and high crystallinity of PbW O4 resulted in its favorable photocatalytic property,and the SPR effect of the Pt NPs promoted visible light harvesting. The Pt NPs also enhanced the separation of photo-generated electrons and holes,which further promoted the photocatalytic reaction.展开更多
AIGaN/GaN high electron mobility transistors grown on sapphire substrates with a 0.3μm gate length and 100μm gate width are fabricated. The device reveals a drain current saturation density of 0.85A/mm at a gate vol...AIGaN/GaN high electron mobility transistors grown on sapphire substrates with a 0.3μm gate length and 100μm gate width are fabricated. The device reveals a drain current saturation density of 0.85A/mm at a gate voltage of 0V and a peak transconductance of 225mS/mm. The unity current gain cutoff frequency and maximum frequency of oscillation are obtained as 45 and 100GHz,respectively. The output power density and gain are 1.8W/mm and 9.5dB at 4GHz,and 1.12W/mm and 11.5dB at 8GHz.展开更多
One novel metal-organic framework [Cu2（L）（μ3-OH）]n（1, H3L = [1,1＇：3＇,1＇＇-terphenyl]-4,4＇＇,5＇-tricarboxylic acid） has been synthesized and characterized by single-crystal powder X-ray diffraction, IR and...One novel metal-organic framework [Cu2（L）（μ3-OH）]n（1, H3L = [1,1＇：3＇,1＇＇-terphenyl]-4,4＇＇,5＇-tricarboxylic acid） has been synthesized and characterized by single-crystal powder X-ray diffraction, IR and thermogravimetric analyses. Complex 1 crystallizes in orthorhombic crystal system, space group Pbca with a = 21.573（19）, b = 5.404（5）, c = 33.78（3） ？, C21H（12）O7Cu2, Mr = 503.39, V = 3938（6） A^3, Z = 8, Dc = 1.698 g·cm^-3, μ = 2.202 mm^-1, F（000） = 2016, 1.531〈θ〈25.009°, λ（Mo Kα） = 0.71073 A, T = 293（2） K, the final R = 0.0448 and wR = 0.1002. The structure of complex 1 is a three-dimensional（3D） framework based on infinite rod-shaped secondary building units and can be simplified as kgd topology. The gas adsorption measurements for N2, CO2, H2O, CH3OH and CH3CH2OH have been done. Fortunately, the selective sorption of CO2 over N2 was found at 195 K.展开更多
Magnetotactic bacteria are a group of Gram-negative bacteria that synthesize magnetic crystals, enabling them to navigate in relation to magnetic field lines. Morphologies of magnetotactic bacteria include spirillum, ...Magnetotactic bacteria are a group of Gram-negative bacteria that synthesize magnetic crystals, enabling them to navigate in relation to magnetic field lines. Morphologies of magnetotactic bacteria include spirillum, coccoid, rod, vibrio, and multicellular morphotypes. The coccid shape is generally the most abundant morphotype among magnetotactic bacteria. Here we describe a species of giant rod-shaped magnetotactic bacteria(designated QR-1) collected from sediment in the low tide zone of Huiquan Bay(Yellow Sea, China). This morphotype accounted for 90% of the magnetotactic bacteria collected, and the only taxonomic group which was detected in the sampling site. Microscopy analysis revealed that QR-1 cells averaged(6.71±1.03)×(1.54±0.20) m m in size, and contained in each cell 42–146 magnetosomes that are arranged in a bundle formed one to four chains along the long axis of the cell. The QR-1 cells displayed axial magnetotaxis with an average velocity of 70±28 mm/s. Transmission electron microscopy based analysis showed that QR-1 cells had two tufts of fl agella at each end. Phylogenetic analysis of the 16 S r RNA genes revealed that QR-1 together with three other rod-shaped uncultivated magnetotactic bacteria are clustered into a deep branch of A lphaproteobacteria.展开更多
A series of main chain liquid crystal aromatic copolyesters with X-shaped and rod-shaped mesogenic units were synthesized via solution condensation polymerizations of 4,4'-(alpha,omega-octanedioyloxy)-dibenzoyl di...A series of main chain liquid crystal aromatic copolyesters with X-shaped and rod-shaped mesogenic units were synthesized via solution condensation polymerizations of 4,4'-(alpha,omega-octanedioyloxy)-dibenzoyl dichlorides with 2,5-bis(p-octanoxy benzoyloxy)-hydroquinone and diphenol. All of the copolyesters showed thermotropic liquid crystalline behaviors through observations using DSC, polarized microscopy and X-ray diffraction. The melting point (T-m) and the isotropization temperature (T-i) change regularly with varying the content of diphenol unit in the copolymers.展开更多
By establishing the finite element models and corresponding calculation methods for the target board and rod-shaped fragment, the penetration effect of the high-velocity rod-shaped fragments＇ impact on the LY- 12cz t...By establishing the finite element models and corresponding calculation methods for the target board and rod-shaped fragment, the penetration effect of the high-velocity rod-shaped fragments＇ impact on the LY- 12cz thin sheet is analyzed by analog calculation. The variation rules of the residual velocity and residual mass of fragments, chock mass and crevasse shape are obtained when the fragment penetrates target board with different incidence velocities and attack angles. Corresponding fitting computation formulas are concluded from the above calculating data. The conclusions are helpful to analyzing the destructivity of fragment and protective ability of aircraft structure. In addition, they can guide the research for battle damage mode and assessment effectively.展开更多
Trapped atoms on photonic structures inspire many novel quantum devices for quantum information processing and quantum sensing.Here,we demonstrate a hybrid photonic-atom chip platform based on a Ga N-onsapphire chip a...Trapped atoms on photonic structures inspire many novel quantum devices for quantum information processing and quantum sensing.Here,we demonstrate a hybrid photonic-atom chip platform based on a Ga N-onsapphire chip and the transport of an ensemble of atoms from free space towards the chip with an optical conveyor belts.Due to our platform’s complete optical accessibility and careful control of atomic motion near the chip with a conveyor belt,successful atomic transport towards the chip is made possible.The maximum transport efficiency of atoms is about 50%with a transport distance of 500μm.Our results open up a new route toward the efficient loading of cold atoms into the evanescent-field trap formed by the photonic integrated circuits,which promises strong and controllable interactions between single atoms and single photons.展开更多
A crack-free AlN film with 4.5 μm thickness was grown on a 2-inch hole-type nano-patterned sapphire substrates(NPSSs) by hydride vapor phase epitaxy(HVPE). The coalescence, stress evolution, and dislocation annihilat...A crack-free AlN film with 4.5 μm thickness was grown on a 2-inch hole-type nano-patterned sapphire substrates(NPSSs) by hydride vapor phase epitaxy(HVPE). The coalescence, stress evolution, and dislocation annihilation mechanisms in the AlN layer have been investigated. The large voids located on the pattern region were caused by the undesirable parasitic crystallites grown on the sidewalls of the nano-pattern in the early growth stage. The coalescence of the c-plane AlN was hindered by these three-fold crystallites and the special triangle void appeared. The cross-sectional Raman line scan was used to characterize the change of stress with film thickness, which corresponds to the characteristics of different growth stages of AlN. Threading dislocations(TDs) mainly originate from the boundary between misaligned crystallites and the c-plane AlN and the coalescence of two adjacent c-plane AlN crystals, rather than the interface between sapphire and AlN.展开更多
The finite-element method has been used to study the thermal stress distribution in large-sized sapphire crystals grown with the sapphire growth technique with micro-pulling and shoulder-expanding at cooled center （S...The finite-element method has been used to study the thermal stress distribution in large-sized sapphire crystals grown with the sapphire growth technique with micro-pulling and shoulder-expanding at cooled center （SAPMAC） method. A critical defect model has been established to explain the growth and propagation of cracks during the sapphire growing process. It is demonstrated that the stress field depends on the growth rate, the ambient temperature and the crystallizing direction. High stresses always exist near the growth interfaces, at the shoulder-expanding locations, the tailing locations and the sites where the diameters undergo sharp changes. The maximum stresses always occur at the interface of seeds and crystals. Cracks often form in the critical defect region and spread in the m-planes and a-planes under applied tensile stresses during crystal growth. The experimental results have verified that with the improved system of crystal growth and well-controlled techniques, the large-sized sapphire crystals of high quality can be grown due to absence of cracks.展开更多
MOCVD-grown 0.25μm gate-length AlGaN/GaN high electron mobility transistors （HEMTs） are fabricated on sapphire substrates. A peak extrinsic transconductance of 250mS/mm and a unity current gain cutoff frequency （f...MOCVD-grown 0.25μm gate-length AlGaN/GaN high electron mobility transistors （HEMTs） are fabricated on sapphire substrates. A peak extrinsic transconductance of 250mS/mm and a unity current gain cutoff frequency （fT） of 77GHz are obtained for a 0.25μm gate-length single finger device. These power devices exhibit a maximum drain current density as high as 1.07A/mm. On-chip testing yielded a continuous-wave output power of 27. 04dBm at 8GHz with an associated power-added efficiency of 26. 5% for an 80 × 10μm device.展开更多
基金supported by MEXT Quantum Leap Flagship Program(MEXT Q-LEAP)Grant Number JPMXS0118067246.
文摘GHz burst-mode femtosecond(fs)laser,which emits a series of pulse trains with extremely short intervals of several hundred picoseconds,provides distinct characteristics in materials processing as compared with the conventional irradiation scheme of fs laser(single-pulse mode).In this paper,we take advantage of the moderate pulse interval of 205 ps(4.88 GHz)in the burst pulse for high-quality and high-efficiency micromachining of single crystalline sapphire by laser induced plasma assisted ablation(LIPAA).Specifically,the preceding pulses in the burst generate plasma by ablation of copper placed behind the sapphire substrate,which interacts with the subsequent pulses to induce ablation at the rear surface of sapphire substrates.As a result,not only the ablation quality but also the ablation efficiency and the fabrication resolution are greatly improved compared to the other schemes including single-pulse mode fs laser direct ablation,single-pulse mode fs-LIPAA,and nanosecond-LIPAA.
基金supported by the National Natural Science Foundation of China(2106700421567008+5 种基金21263005)Project of Jiangxi Province Natural Science Foundation China(20133BAB21003)Training Programs of Innovation and Entrepreneurship for Undergraduates of Jiangxi Province(201310407046)The Landing Project of Science and Technology of Colleges and Universities in Jiangxi Province(KJLD14046)Young Scientist Training Project of Jiangxi Province(20122BCB23015)Yuanhang Engineering of Jiangxi Province~~
文摘Rod-shaped PbW O4 microcrystals of length 1 μm were fabricated by a hydrothermal route and subsequent calcination. Pt nanoparticles（NPs） of different contents（0.5 wt%,1 wt% and 2 wt%） were subsequently deposited on the PbW O4 microcrystals,producing robust Pt/PbW O4 composite microcrystals. The PbW O4 microcrystals and Pt/PbW O4 photocatalysts were characterized by X-ray diffraction,N2 sorption measurements,scanning electron microscopy,transmission electron microscopy,and X-ray photoelectron,photoluminescence,Fourier-transform infrared,and ultraviolet-visible diffuse reflectance spectroscopies. The photocatalytic performances of the catalysts were evaluated by the consecutive photocatalytic degradation of acid orange II dye. The Pt/PbW O4 composite microcrystals exhibited high photocatalytic activity and stability. The deposition of Pt NPs produced surface plasmon resonance（SPR）,which induced a large visible light absorption. A Pt NP content of 1-2 wt% resulted in an ~2 times increase in photocatalytic activity,compared with the activity of Pt/PbW O4. The crystal structure and high crystallinity of PbW O4 resulted in its favorable photocatalytic property,and the SPR effect of the Pt NPs promoted visible light harvesting. The Pt NPs also enhanced the separation of photo-generated electrons and holes,which further promoted the photocatalytic reaction.
文摘AIGaN/GaN high electron mobility transistors grown on sapphire substrates with a 0.3μm gate length and 100μm gate width are fabricated. The device reveals a drain current saturation density of 0.85A/mm at a gate voltage of 0V and a peak transconductance of 225mS/mm. The unity current gain cutoff frequency and maximum frequency of oscillation are obtained as 45 and 100GHz,respectively. The output power density and gain are 1.8W/mm and 9.5dB at 4GHz,and 1.12W/mm and 11.5dB at 8GHz.
基金Supported by the Natural Science Foundation of Shandong Province(No.ZR2016BL01)the Talent Introduction Project of Dezhou University(No.320116)
文摘One novel metal-organic framework [Cu2（L）（μ3-OH）]n（1, H3L = [1,1＇：3＇,1＇＇-terphenyl]-4,4＇＇,5＇-tricarboxylic acid） has been synthesized and characterized by single-crystal powder X-ray diffraction, IR and thermogravimetric analyses. Complex 1 crystallizes in orthorhombic crystal system, space group Pbca with a = 21.573（19）, b = 5.404（5）, c = 33.78（3） ？, C21H（12）O7Cu2, Mr = 503.39, V = 3938（6） A^3, Z = 8, Dc = 1.698 g·cm^-3, μ = 2.202 mm^-1, F（000） = 2016, 1.531〈θ〈25.009°, λ（Mo Kα） = 0.71073 A, T = 293（2） K, the final R = 0.0448 and wR = 0.1002. The structure of complex 1 is a three-dimensional（3D） framework based on infinite rod-shaped secondary building units and can be simplified as kgd topology. The gas adsorption measurements for N2, CO2, H2O, CH3OH and CH3CH2OH have been done. Fortunately, the selective sorption of CO2 over N2 was found at 195 K.
基金Supported by the National Natural Science Foundation of China(Nos.41330962,41276170)the National Natural Science Foundation of China-Shandong Joint Fund for Marine Science Research Centers(No.U1606404)
文摘Magnetotactic bacteria are a group of Gram-negative bacteria that synthesize magnetic crystals, enabling them to navigate in relation to magnetic field lines. Morphologies of magnetotactic bacteria include spirillum, coccoid, rod, vibrio, and multicellular morphotypes. The coccid shape is generally the most abundant morphotype among magnetotactic bacteria. Here we describe a species of giant rod-shaped magnetotactic bacteria(designated QR-1) collected from sediment in the low tide zone of Huiquan Bay(Yellow Sea, China). This morphotype accounted for 90% of the magnetotactic bacteria collected, and the only taxonomic group which was detected in the sampling site. Microscopy analysis revealed that QR-1 cells averaged(6.71±1.03)×(1.54±0.20) m m in size, and contained in each cell 42–146 magnetosomes that are arranged in a bundle formed one to four chains along the long axis of the cell. The QR-1 cells displayed axial magnetotaxis with an average velocity of 70±28 mm/s. Transmission electron microscopy based analysis showed that QR-1 cells had two tufts of fl agella at each end. Phylogenetic analysis of the 16 S r RNA genes revealed that QR-1 together with three other rod-shaped uncultivated magnetotactic bacteria are clustered into a deep branch of A lphaproteobacteria.
基金The work was supported by the National Natural Science Foundation of China.
文摘A series of main chain liquid crystal aromatic copolyesters with X-shaped and rod-shaped mesogenic units were synthesized via solution condensation polymerizations of 4,4'-(alpha,omega-octanedioyloxy)-dibenzoyl dichlorides with 2,5-bis(p-octanoxy benzoyloxy)-hydroquinone and diphenol. All of the copolyesters showed thermotropic liquid crystalline behaviors through observations using DSC, polarized microscopy and X-ray diffraction. The melting point (T-m) and the isotropization temperature (T-i) change regularly with varying the content of diphenol unit in the copolymers.
基金Sponsored by the Ministerial Level Advanced Research Foundation(2164K)
文摘By establishing the finite element models and corresponding calculation methods for the target board and rod-shaped fragment, the penetration effect of the high-velocity rod-shaped fragments＇ impact on the LY- 12cz thin sheet is analyzed by analog calculation. The variation rules of the residual velocity and residual mass of fragments, chock mass and crevasse shape are obtained when the fragment penetrates target board with different incidence velocities and attack angles. Corresponding fitting computation formulas are concluded from the above calculating data. The conclusions are helpful to analyzing the destructivity of fragment and protective ability of aircraft structure. In addition, they can guide the research for battle damage mode and assessment effectively.
基金supported by the National Key R&D Program(Grant No.2021YFF0603701)the National Natural Science Foundation of China(Grant Nos.U21A20433,U21A6006,92265210,12104441,12134014,61905234,and 11974335)+1 种基金the USTC Research Funds of the Double First-Class Initiative(Grant No.YD2030002007),USTC Research Funds of the Double First-Class Initiativesupported by the Fundamental Research Funds for the Central Universities。
文摘Trapped atoms on photonic structures inspire many novel quantum devices for quantum information processing and quantum sensing.Here,we demonstrate a hybrid photonic-atom chip platform based on a Ga N-onsapphire chip and the transport of an ensemble of atoms from free space towards the chip with an optical conveyor belts.Due to our platform’s complete optical accessibility and careful control of atomic motion near the chip with a conveyor belt,successful atomic transport towards the chip is made possible.The maximum transport efficiency of atoms is about 50%with a transport distance of 500μm.Our results open up a new route toward the efficient loading of cold atoms into the evanescent-field trap formed by the photonic integrated circuits,which promises strong and controllable interactions between single atoms and single photons.
基金supported by the National Natural Science Foundation of China (Grant No. 61974158)the Natural Science Fund of Jiangsu Province, China (Grant No. BK20191456)。
文摘A crack-free AlN film with 4.5 μm thickness was grown on a 2-inch hole-type nano-patterned sapphire substrates(NPSSs) by hydride vapor phase epitaxy(HVPE). The coalescence, stress evolution, and dislocation annihilation mechanisms in the AlN layer have been investigated. The large voids located on the pattern region were caused by the undesirable parasitic crystallites grown on the sidewalls of the nano-pattern in the early growth stage. The coalescence of the c-plane AlN was hindered by these three-fold crystallites and the special triangle void appeared. The cross-sectional Raman line scan was used to characterize the change of stress with film thickness, which corresponds to the characteristics of different growth stages of AlN. Threading dislocations(TDs) mainly originate from the boundary between misaligned crystallites and the c-plane AlN and the coalescence of two adjacent c-plane AlN crystals, rather than the interface between sapphire and AlN.
基金National Defence Pre-research Foundation of China (41312040404)
文摘The finite-element method has been used to study the thermal stress distribution in large-sized sapphire crystals grown with the sapphire growth technique with micro-pulling and shoulder-expanding at cooled center （SAPMAC） method. A critical defect model has been established to explain the growth and propagation of cracks during the sapphire growing process. It is demonstrated that the stress field depends on the growth rate, the ambient temperature and the crystallizing direction. High stresses always exist near the growth interfaces, at the shoulder-expanding locations, the tailing locations and the sites where the diameters undergo sharp changes. The maximum stresses always occur at the interface of seeds and crystals. Cracks often form in the critical defect region and spread in the m-planes and a-planes under applied tensile stresses during crystal growth. The experimental results have verified that with the improved system of crystal growth and well-controlled techniques, the large-sized sapphire crystals of high quality can be grown due to absence of cracks.
文摘MOCVD-grown 0.25μm gate-length AlGaN/GaN high electron mobility transistors （HEMTs） are fabricated on sapphire substrates. A peak extrinsic transconductance of 250mS/mm and a unity current gain cutoff frequency （fT） of 77GHz are obtained for a 0.25μm gate-length single finger device. These power devices exhibit a maximum drain current density as high as 1.07A/mm. On-chip testing yielded a continuous-wave output power of 27. 04dBm at 8GHz with an associated power-added efficiency of 26. 5% for an 80 × 10μm device.
