Developing a versatile etching strategy for constructing hierarchically porous metal-organic frameworks(HP-MOFs)with anticipated mesopores and micropores remains a crucial scientific challenge in probing the enhanced ...Developing a versatile etching strategy for constructing hierarchically porous metal-organic frameworks(HP-MOFs)with anticipated mesopores and micropores remains a crucial scientific challenge in probing the enhanced performance and potential applications of MOF materials.Herein,a universal vapor etching method is implemented to controllably create HP-MOFs.Based on the principle that the concentration of vapor is lower than that of the solution,the etching rate and strength toward MOFs are greatly reduced,enabling us to obtain intermediate products during etching.Using this strategy,a series of desired HP-MOFs with varying metal nodes have been prepared.The resultant HP-MOFs integrate the merits of mesopores(mass transfer facilitation)and micropores(large internal surface area).For the degradation of the nerve agent,dimethyl 4-nitrophenyl phosphate,HP-UiO-66 exhibits better catalytic activity than pristine UiO-66.展开更多
Nonpolar （1120） GaN films are grown on the etched a-plane GaN substrates via metalorganic vapor phase epitaxy. High-resolution X-ray diffraction analysis shows great decreases in the full width at half maximum of th...Nonpolar （1120） GaN films are grown on the etched a-plane GaN substrates via metalorganic vapor phase epitaxy. High-resolution X-ray diffraction analysis shows great decreases in the full width at half maximum of the samples grown on etched substrates compared with those of the sample without etching, both on-axis and off-axis, indicating the reduced dislocation densities and improved crystalline quality of these samples. The spatial mapping of the E2 （high） phonon mode demonstrates the smaller line width with a black background in the wing region, which testifies the reduced dislocation densities and enhanced crystalline quality of the epitaxial lateral overgrowth areas. Raman scattering spectra of the E2 （high） peaks exhibit in-plane compressive stress for all the overgrowth samples, and the E2 （high） peaks of samples grown on etched substrates shift toward the lower frequency range, indicating the relaxations of in-plane stress in these GaN films. Furthermore, room temperature photoluminescence measurement demonstrates a significant decrease in the yellow-band emission intensity of a-plane GaN grown on etched templates, which also illustrates the better optical properties of these samples.展开更多
Plasma enhanced chemical vapor deposition (PECVD) and electron cyclotron resonance (ECR) etching were used in the development of silica layers for planar waveguide applications. The addition of GeH4 to silica was used...Plasma enhanced chemical vapor deposition (PECVD) and electron cyclotron resonance (ECR) etching were used in the development of silica layers for planar waveguide applications. The addition of GeH4 to silica was used to control the refractive index of core layers with core-to-clad index differences in the range of 0.2%-1.3%. Refractive index uniformity variance of ±0.0003 was achieved after annealing for 4-inch Si (100) wafers. The core layers with thickness up to 6 μm were etched by ECR with optimized recipe and mask material. Low-loss silica-on-silicon waveguides whose propagation loss is approximately 0.07 dB/cm at 1550 nm are fabricated.展开更多
Novel silicon nanotubes with inner-diameter of 60-80 nm was prepared using; hydrogen-added dechlorination of SiCl4 followed by chemical vapor deposition (CVD) on a NixMgyO catalyst. The TEM observation showed that the...Novel silicon nanotubes with inner-diameter of 60-80 nm was prepared using; hydrogen-added dechlorination of SiCl4 followed by chemical vapor deposition (CVD) on a NixMgyO catalyst. The TEM observation showed that the suitable reaction temperature is 973 K for the formation of silicon nanotubes. Most of silicon nanotubes have one open end and some have two closed ends. The shape of nanoscale silicon, however, isa micro-crystal type at 873 K, a rod or needle type at 993 K and an onion-type at 1023 K, respectively.展开更多
Anisotropic materials, like carbon nanotubes(CNTs), are the perfect substitutes to overcome the limitations of conventional metamaterials; however, the successful fabrication of CNT forest metamaterial structures is s...Anisotropic materials, like carbon nanotubes(CNTs), are the perfect substitutes to overcome the limitations of conventional metamaterials; however, the successful fabrication of CNT forest metamaterial structures is still very challenging. In this study, a new method utilizing a focused ion beam(FIB) with additional secondary etching is presented, which can obtain uniform and fine patterning of CNT forest nanostructures for metamaterials and ranging in sizes from hundreds of nanometers to several micrometers. The influence of the FIB processing parameters on the morphology of the catalyst surface and the growth of the CNT forest was investigated, including the removal of redeposited material,decreasing the average surface roughness(from 0.45 to 0.15 nm), and a decrease in the thickness of the Fe catalyst.The results showed that the combination of FIB patterning and secondary etching enabled the growth of highly aligned, highdensity CNT forest metamaterials. The improvement in the quality of single-walled CNTs(SWNTs), defined by the very high G/D peak ratio intensity of 10.47, demonstrated successful fine patterning of CNT forest for the first time. With a FIB patterning depth of 10 nm and a secondary etching of 0.5 nm, a minimum size of 150 nm of CNT forest metamaterials was achieved. The development of the FIB secondary etching method enabled for the first time, the fabrication of SWNT forest metamaterials for the optical and infrared regime, for future applications, e.g., in superlenses, antennas,or thermal metamaterials.展开更多
基金financially supported by the National Natural Science Foundation of China(22175030)the Open Project of State Key Laboratory of Supramolecular Structure and Materials(sklssm202205)。
文摘Developing a versatile etching strategy for constructing hierarchically porous metal-organic frameworks(HP-MOFs)with anticipated mesopores and micropores remains a crucial scientific challenge in probing the enhanced performance and potential applications of MOF materials.Herein,a universal vapor etching method is implemented to controllably create HP-MOFs.Based on the principle that the concentration of vapor is lower than that of the solution,the etching rate and strength toward MOFs are greatly reduced,enabling us to obtain intermediate products during etching.Using this strategy,a series of desired HP-MOFs with varying metal nodes have been prepared.The resultant HP-MOFs integrate the merits of mesopores(mass transfer facilitation)and micropores(large internal surface area).For the degradation of the nerve agent,dimethyl 4-nitrophenyl phosphate,HP-UiO-66 exhibits better catalytic activity than pristine UiO-66.
基金Project supported by the National Natural Science Foundation of China(Grant No.61204006)the Fundamental Research Funds for the Central Universities,China(Grant No.K50511250002)the National Key Science & Technology Special Project,China(Grant No.2008ZX01002-002)
文摘Nonpolar （1120） GaN films are grown on the etched a-plane GaN substrates via metalorganic vapor phase epitaxy. High-resolution X-ray diffraction analysis shows great decreases in the full width at half maximum of the samples grown on etched substrates compared with those of the sample without etching, both on-axis and off-axis, indicating the reduced dislocation densities and improved crystalline quality of these samples. The spatial mapping of the E2 （high） phonon mode demonstrates the smaller line width with a black background in the wing region, which testifies the reduced dislocation densities and enhanced crystalline quality of the epitaxial lateral overgrowth areas. Raman scattering spectra of the E2 （high） peaks exhibit in-plane compressive stress for all the overgrowth samples, and the E2 （high） peaks of samples grown on etched substrates shift toward the lower frequency range, indicating the relaxations of in-plane stress in these GaN films. Furthermore, room temperature photoluminescence measurement demonstrates a significant decrease in the yellow-band emission intensity of a-plane GaN grown on etched templates, which also illustrates the better optical properties of these samples.
基金This work was supported by the National Natural Science Foundation of China under Grant No. 60177023.
文摘Plasma enhanced chemical vapor deposition (PECVD) and electron cyclotron resonance (ECR) etching were used in the development of silica layers for planar waveguide applications. The addition of GeH4 to silica was used to control the refractive index of core layers with core-to-clad index differences in the range of 0.2%-1.3%. Refractive index uniformity variance of ±0.0003 was achieved after annealing for 4-inch Si (100) wafers. The core layers with thickness up to 6 μm were etched by ECR with optimized recipe and mask material. Low-loss silica-on-silicon waveguides whose propagation loss is approximately 0.07 dB/cm at 1550 nm are fabricated.
基金the NSF of China (No.29773037 No. 29933040 and No. 20023001) and the NSF of Fujian province (No. E9910001 and No. E0010006).
文摘Novel silicon nanotubes with inner-diameter of 60-80 nm was prepared using; hydrogen-added dechlorination of SiCl4 followed by chemical vapor deposition (CVD) on a NixMgyO catalyst. The TEM observation showed that the suitable reaction temperature is 973 K for the formation of silicon nanotubes. Most of silicon nanotubes have one open end and some have two closed ends. The shape of nanoscale silicon, however, isa micro-crystal type at 873 K, a rod or needle type at 993 K and an onion-type at 1023 K, respectively.
文摘Anisotropic materials, like carbon nanotubes(CNTs), are the perfect substitutes to overcome the limitations of conventional metamaterials; however, the successful fabrication of CNT forest metamaterial structures is still very challenging. In this study, a new method utilizing a focused ion beam(FIB) with additional secondary etching is presented, which can obtain uniform and fine patterning of CNT forest nanostructures for metamaterials and ranging in sizes from hundreds of nanometers to several micrometers. The influence of the FIB processing parameters on the morphology of the catalyst surface and the growth of the CNT forest was investigated, including the removal of redeposited material,decreasing the average surface roughness(from 0.45 to 0.15 nm), and a decrease in the thickness of the Fe catalyst.The results showed that the combination of FIB patterning and secondary etching enabled the growth of highly aligned, highdensity CNT forest metamaterials. The improvement in the quality of single-walled CNTs(SWNTs), defined by the very high G/D peak ratio intensity of 10.47, demonstrated successful fine patterning of CNT forest for the first time. With a FIB patterning depth of 10 nm and a secondary etching of 0.5 nm, a minimum size of 150 nm of CNT forest metamaterials was achieved. The development of the FIB secondary etching method enabled for the first time, the fabrication of SWNT forest metamaterials for the optical and infrared regime, for future applications, e.g., in superlenses, antennas,or thermal metamaterials.
