Silica whispering gallery mode（WGM） microcavities were fabricated by the buffered oxide etcher and potassium hydroxide wet etching technique without any subsequent chemical or laser treatments. The silicon pedestal ...Silica whispering gallery mode（WGM） microcavities were fabricated by the buffered oxide etcher and potassium hydroxide wet etching technique without any subsequent chemical or laser treatments. The silicon pedestal underneath was an octagonal pyramid, thus providing a pointed connection area with the top silica microdisk while weakly influencing the resonance modes. The sidewalls of our microdisks were wedge shaped, which was believed to be an advantage for the mode confinement. Efficient coupling from and to the 60 μm diameter microdisk structure was achieved using tapered optical fibres, exhibiting a quality factor of 1.5×10^4 near a wavelength of 1550 nm. Many resonance modes were observed, and double transverse electric modes were identified by theoretical calculations. The quality factor of the microdisks was also analysed to deduce the cavity roughness. The wet etching technique provides a more convenient avenue to fabricate WGM microdisks than conventional fabrication methods.展开更多
Dual heteroatom-doped carbons have attracted widespread research attention as catalysts in the field of energy storage and conversion due to their unique electronic structures and chemical tunability.In particular,bor...Dual heteroatom-doped carbons have attracted widespread research attention as catalysts in the field of energy storage and conversion due to their unique electronic structures and chemical tunability.In particular,boron and nitrogen co-doped carbon(B,N@C)has shown great potential for photo/electrocatalytic applications.However,more needs to be done for rational designing and regulating the structure of these materials to improve their catalytic performance.Herein,monodispersed hierarchical porous B,N@C nanocages were fabricated by pyrolyzing zeolite imidazole framework(ZIF)which was treated with ammonia borane or boric acid via an integrated double-solvent impregnation and nanocofined-etching method.The treated ZIF-8 provided an essential structural template to achieve B,N co-doped hierarchical structures with micro/meso/macro multimodal pore size distributions.The resultant B,N@C nanocages displayed high catalytic activities for electrochemical oxygen reduction reaction(ORR)in alkaline media,outperforming most carbon-based catalysts,particularly from the perspective of the half-wave potentials.Such high catalytic performance is due to the enhanced activity by the coexistence of B and N and the mass transfer promoted by the unique hierarchical porous structure.展开更多
By introducing the mechanical motion into the confined etchant layer technique(CELT), we have developed a promising ultraprecision machining method, termed as electrochemical mechanical micromachining(ECMM), for produ...By introducing the mechanical motion into the confined etchant layer technique(CELT), we have developed a promising ultraprecision machining method, termed as electrochemical mechanical micromachining(ECMM), for producing both regular and irregular three dimensional(3 D) microstructures. It was found that there was a dramatic coupling effect between the confined etching process and the slow-rate mechanical motion because of the concentration distribution of electrogenerated etchant caused by the latter. In this article, the coupling effect was investigated systemically by comparing the etchant diffusion, etching depths and profiles in the non-confined and confined machining modes. A two-dimensional(2 D) numerical simulation model was proposed to analyze the diffusion variations during the ECMM process, which is well verified by the machining experiments. The results showed that, in the confined machining mode, both the machining resolution and the perpendicularity tolerance of side faces were improved effectively. Furthermore, the theoretical modeling and numerical simulations were proved valuable to optimize the technical parameters of the ECMM process.展开更多
WHEN scanning electrochemical microscopy (SECM) with feedback mode is used to etchcertain surface, the etchant molecules generated at a microelectrode diffuse to the surface andreact therein with the surface species, ...WHEN scanning electrochemical microscopy (SECM) with feedback mode is used to etchcertain surface, the etchant molecules generated at a microelectrode diffuse to the surface andreact therein with the surface species, resulting in local etching pattern. It is noted that theetching resolution of SECM is dominantly determined by the size of the microelectrode.However, many experimental results have shown the significant influence of the lateral diffu-sion of etchant on the etching resolution. Therefore, a thin diffusion layer of the展开更多
This paper mainly focuses on solving the low yield problem for lateral phase change random access memory with a fully confined phase change material node. Improper over-etching and bad step-coverage of physical vapor ...This paper mainly focuses on solving the low yield problem for lateral phase change random access memory with a fully confined phase change material node. Improper over-etching and bad step-coverage of physical vapor deposition were the main reasons for the poor contact quality, which leads to the low yield problem. Process improvement was carried out to better control over-etching within 10 nm. Atomic layer deposition process was used to replace physical vapor deposition to guarantee good step coverage. Contrasting cross-sectional photos taken by scanning electron microscopy showed great improvement in contact quality. The atom layer deposition process was demonstrated to have good prospects in nano-contact for phase change memory application.展开更多
Core-shell hybrid nanomaterials have shown new properties and functions that are not attainable by their single counterparts.Nanoscale confinement effect by porous inorganic shells in the hybrid nanostructures plays a...Core-shell hybrid nanomaterials have shown new properties and functions that are not attainable by their single counterparts.Nanoscale confinement effect by porous inorganic shells in the hybrid nanostructures plays an important role for chemical transformation of the core nanoparticles.However,metal-organic frameworks(MOFs)have been rarely applied for understanding mechanical insight into such nanoscale phenomena in confinement,although MOFs would provide a variety of properties for the confining environment than other inorganic shells such as silica and zeolite.Here,we examine chemical transformation of a gold nanorod core enclosed by a zeolitic imidazolate framework(ZIF)through chemical etching and regrowth,followed by quantitative analysis in the core dimension and curvature.We find the nanorod core shows template-effective behavior in its morphological transformation.In the etching event,the nanorod core is spherically carved from its tips.The regrowth on the spherically etched core inside the ZIF gives rise toformation of a raspberry-like branched nanostructure in contrast to the growth of an octahedral shape in bulk condition.We attribute the shell-directed regrowth to void space generated at the interfaces between the etched core and the ZIF shell,intercrystalline gaps in mult-domain ZIF shells,and local structural deformation from the acidic reaction conditions.展开更多
基金Project supported by the Postdoctoral Science Foundation of China(Grant No.2015M582041)the Special Project on the Integration of Industry,Education and Research of Aviation Industry Corporation of China
文摘Silica whispering gallery mode（WGM） microcavities were fabricated by the buffered oxide etcher and potassium hydroxide wet etching technique without any subsequent chemical or laser treatments. The silicon pedestal underneath was an octagonal pyramid, thus providing a pointed connection area with the top silica microdisk while weakly influencing the resonance modes. The sidewalls of our microdisks were wedge shaped, which was believed to be an advantage for the mode confinement. Efficient coupling from and to the 60 μm diameter microdisk structure was achieved using tapered optical fibres, exhibiting a quality factor of 1.5×10^4 near a wavelength of 1550 nm. Many resonance modes were observed, and double transverse electric modes were identified by theoretical calculations. The quality factor of the microdisks was also analysed to deduce the cavity roughness. The wet etching technique provides a more convenient avenue to fabricate WGM microdisks than conventional fabrication methods.
基金We acknowledge support under the Australian Research Council’s Future Fellowship(No.FT190100658,Z.H.)support from the Alexander von Humboldt Foundation(Z.H.).X.W.also acknowledges the Chinese Scholarship Council(CSC)for financial support.
文摘Dual heteroatom-doped carbons have attracted widespread research attention as catalysts in the field of energy storage and conversion due to their unique electronic structures and chemical tunability.In particular,boron and nitrogen co-doped carbon(B,N@C)has shown great potential for photo/electrocatalytic applications.However,more needs to be done for rational designing and regulating the structure of these materials to improve their catalytic performance.Herein,monodispersed hierarchical porous B,N@C nanocages were fabricated by pyrolyzing zeolite imidazole framework(ZIF)which was treated with ammonia borane or boric acid via an integrated double-solvent impregnation and nanocofined-etching method.The treated ZIF-8 provided an essential structural template to achieve B,N co-doped hierarchical structures with micro/meso/macro multimodal pore size distributions.The resultant B,N@C nanocages displayed high catalytic activities for electrochemical oxygen reduction reaction(ORR)in alkaline media,outperforming most carbon-based catalysts,particularly from the perspective of the half-wave potentials.Such high catalytic performance is due to the enhanced activity by the coexistence of B and N and the mass transfer promoted by the unique hierarchical porous structure.
基金supported by the National Natural Science Foundation of China (21573054, 21327002, 91323303, 21621091)the Joint Funds Key Project of the National Natural Science Foundation of China (U1537214)+2 种基金the State Key Program of National Natural Science of China (51535003)Self-Planned Task (SKLRS201606B) of State Key Laboratory of Robotics and System (HIT)the Open Project of the State Key Laboratory for Manufacturing Systems Engineering (Xi'an Jiaotong University)
文摘By introducing the mechanical motion into the confined etchant layer technique(CELT), we have developed a promising ultraprecision machining method, termed as electrochemical mechanical micromachining(ECMM), for producing both regular and irregular three dimensional(3 D) microstructures. It was found that there was a dramatic coupling effect between the confined etching process and the slow-rate mechanical motion because of the concentration distribution of electrogenerated etchant caused by the latter. In this article, the coupling effect was investigated systemically by comparing the etchant diffusion, etching depths and profiles in the non-confined and confined machining modes. A two-dimensional(2 D) numerical simulation model was proposed to analyze the diffusion variations during the ECMM process, which is well verified by the machining experiments. The results showed that, in the confined machining mode, both the machining resolution and the perpendicularity tolerance of side faces were improved effectively. Furthermore, the theoretical modeling and numerical simulations were proved valuable to optimize the technical parameters of the ECMM process.
文摘WHEN scanning electrochemical microscopy (SECM) with feedback mode is used to etchcertain surface, the etchant molecules generated at a microelectrode diffuse to the surface andreact therein with the surface species, resulting in local etching pattern. It is noted that theetching resolution of SECM is dominantly determined by the size of the microelectrode.However, many experimental results have shown the significant influence of the lateral diffu-sion of etchant on the etching resolution. Therefore, a thin diffusion layer of the
基金supported by the National Basic Research Program of China(No.2011CB922103)the National Natural Science Foundation of China(Nos.61376420,61404126,A040203)the Science and Technology Project of Shenzhen(No.JCYJ20140509172609175)
文摘This paper mainly focuses on solving the low yield problem for lateral phase change random access memory with a fully confined phase change material node. Improper over-etching and bad step-coverage of physical vapor deposition were the main reasons for the poor contact quality, which leads to the low yield problem. Process improvement was carried out to better control over-etching within 10 nm. Atomic layer deposition process was used to replace physical vapor deposition to guarantee good step coverage. Contrasting cross-sectional photos taken by scanning electron microscopy showed great improvement in contact quality. The atom layer deposition process was demonstrated to have good prospects in nano-contact for phase change memory application.
基金the Korea Institute of Energy Technology Evaluation and Planning(No.20192050100060)from the Korea government Ministry of Trade,Industry,and Energy(MOTIE)and the Korea Basic Science Institute(KBSI)National Research Facilities&Equipment Center(NFEC)(No.2019R 1A 6C 1010042)from the Ministry of Education of Korea.In addition,this work was partially supported by the N ano.M aterial Technology D evelopm ent Program(No.2009-0082580)Basic Science Research Program(No.2020R1C1C1007568)through the National Research Foundation of Korea funded by the Ministry of Science,Information&Communication Technology(ICT),and Future Planning.
文摘Core-shell hybrid nanomaterials have shown new properties and functions that are not attainable by their single counterparts.Nanoscale confinement effect by porous inorganic shells in the hybrid nanostructures plays an important role for chemical transformation of the core nanoparticles.However,metal-organic frameworks(MOFs)have been rarely applied for understanding mechanical insight into such nanoscale phenomena in confinement,although MOFs would provide a variety of properties for the confining environment than other inorganic shells such as silica and zeolite.Here,we examine chemical transformation of a gold nanorod core enclosed by a zeolitic imidazolate framework(ZIF)through chemical etching and regrowth,followed by quantitative analysis in the core dimension and curvature.We find the nanorod core shows template-effective behavior in its morphological transformation.In the etching event,the nanorod core is spherically carved from its tips.The regrowth on the spherically etched core inside the ZIF gives rise toformation of a raspberry-like branched nanostructure in contrast to the growth of an octahedral shape in bulk condition.We attribute the shell-directed regrowth to void space generated at the interfaces between the etched core and the ZIF shell,intercrystalline gaps in mult-domain ZIF shells,and local structural deformation from the acidic reaction conditions.
