Ablation threshold is an important concept in the study of femtosecond laser micro-and nano-machining.In this paper,the ablation experiments of three kinds of surface roughness 4H-Si C substrates irradiated by femtose...Ablation threshold is an important concept in the study of femtosecond laser micro-and nano-machining.In this paper,the ablation experiments of three kinds of surface roughness 4H-Si C substrates irradiated by femtosecond laser were carried out.The feature thresholds were systematically measured for three surface roughness Si C substrates and found in the modification and annealing regions ranging from coincidence(R_(a)=0.5 nm)to a clear demarcation(R_(a)=5.5 nm),eventually being difficult to identify the presence of the former(R_(a)=89 nm).Under multi-pulse laser irradiation,oriented ripple structures were generated in the annealing region,where deep subwavelength ripples(about 110 nm,Λ≈0.2λ)can be generated above substrates with surface roughness higher than 5.5 nm.We investigated the effect of surface roughness on the ablation morphology,ablation threshold,and periodic structures of femtosecond laser ablation of 4H-Si C substrates,while the ablation threshold was tended to decrease and stabilize with the increase of pulse number N≥500.展开更多
An SF6/CF4 cyclic reactive-ion etching （RIE） method is proposed to suppress the surface roughness and to opti- mize the morphology of Ge fin, aiming at the fabrication of superior Ge FinFETs for future CMOS technolo...An SF6/CF4 cyclic reactive-ion etching （RIE） method is proposed to suppress the surface roughness and to opti- mize the morphology of Ge fin, aiming at the fabrication of superior Ge FinFETs for future CMOS technologies. The surface roughness of the Ge after RIE can be sufficiently reduced by introducing SF6-O2 etching steps into the CF4-O2 etching process, while maintaining a relatively large ratio of vertical etching over horizontal etching of the Ge. As a result, an optimized rms roughness of 0.9nm is achieved for Ge surfaces after the SF6/CF4 cyclic etching with a ratio of greater than four for vertical etching over horizontal etching of the Ge, by using a proportion of 60% for SF6-O2 etching steps.展开更多
在红外探测领域,InSb材料已经大规模地被用于制造3~5μm波长范围的焦平面阵列探测器。对更大规模、更高性能探测器的需求日益增长,而该类探测器需要在更大尺寸、更高质量的晶片上制备。所以,对4 in InSb晶片加工技术进行了研究。通过优...在红外探测领域,InSb材料已经大规模地被用于制造3~5μm波长范围的焦平面阵列探测器。对更大规模、更高性能探测器的需求日益增长,而该类探测器需要在更大尺寸、更高质量的晶片上制备。所以,对4 in InSb晶片加工技术进行了研究。通过优化研磨、抛光工艺参数,最终获得总厚度偏差小于等于10μm、翘曲度小于等于20μm、表面粗糙度小于1 nm、表面质量优的4 in InSb晶片,提高了加工效率,能够满足大规模高质量红外焦平面探测器的使用需求。展开更多
We study the coupled flow and heat transfer of power-law nanofluids on a non-isothermal rough rotating disk subjected to a magnetic field.The problem is formulated in terms of specified curvilinear orthogonal coordina...We study the coupled flow and heat transfer of power-law nanofluids on a non-isothermal rough rotating disk subjected to a magnetic field.The problem is formulated in terms of specified curvilinear orthogonal coordinate system.An improved BVP4C algorithm is proposed,and numerical solutions are obtained.The influence of volume fraction,types and shapes of nanoparticles,magnetic field and power-law index on the flow,and heat transfer behavior are discussed.The obtained results show that the power-law exponents(PLE),nanoparticle volume fraction(NVF),and magnetic field inclination angle(MFIA)have almost no effects on velocities in the wave surface direction,but have small or significant effects on the azimuth direction.The NVF has remarkable influences on local Nusselt number(LNN)and friction coefficients(FC)in the radial direction and the azimuth direction(AD).The LNN increases with NVF increasing while FC in AD decreases.The types of nanoparticles,magnetic field strength,and inclination have small effects on LNN,but they have remarkable influences on the friction coefficients with positively correlated heat transfer rate,while the inclination is negatively correlated with heat transfer rate.The size of the nanoparticle shape factor is positively correlated with LNN.展开更多
In flat jet electrochemical milling, the electrolyte forms a backward parallel flow after impacting the workpiece, resulting in a weak current density distribution on the workpiece. Poor surface quality usually occurs...In flat jet electrochemical milling, the electrolyte forms a backward parallel flow after impacting the workpiece, resulting in a weak current density distribution on the workpiece. Poor surface quality usually occurs on the machined titanium alloy surface because it inevitably suffers from the weak current density. In this study, a method of flat jet electrochemical milling with tailoring the backward parallel flow was proposed to eliminate the negative effects caused by the weak current density. Multiphysics simulations are carried out to comprehend the mechanism of flat jetEC milling with tailoring backward parallel flow and better construct the novel tool electrode.Experiments on flat jet electrochemical milling of TC4 alloy with and without tailoring backward parallel flow are conducted. The results reveal that, compared with flat jet electrochemical milling without tailoring backward parallel flow, the recommended tool reduces the surface roughness by86% to 93%, and improves the material removal rate by 93% to 163% with different feed rates.Additionally, the recommended tool is more conducive to maintaining the inherent hardness of the material. Finally, a surface with low Sa of 0.37 μm is obtained.展开更多
基金Project(52075103)supported by the National Natural Science Foundation of ChinaProject(2020B1515120058)supported by the Key Project of Regional Joint Fund of Guangdong Basic and Applied Basic Research Foundation,China。
文摘Ablation threshold is an important concept in the study of femtosecond laser micro-and nano-machining.In this paper,the ablation experiments of three kinds of surface roughness 4H-Si C substrates irradiated by femtosecond laser were carried out.The feature thresholds were systematically measured for three surface roughness Si C substrates and found in the modification and annealing regions ranging from coincidence(R_(a)=0.5 nm)to a clear demarcation(R_(a)=5.5 nm),eventually being difficult to identify the presence of the former(R_(a)=89 nm).Under multi-pulse laser irradiation,oriented ripple structures were generated in the annealing region,where deep subwavelength ripples(about 110 nm,Λ≈0.2λ)can be generated above substrates with surface roughness higher than 5.5 nm.We investigated the effect of surface roughness on the ablation morphology,ablation threshold,and periodic structures of femtosecond laser ablation of 4H-Si C substrates,while the ablation threshold was tended to decrease and stabilize with the increase of pulse number N≥500.
基金Supported by the National Basic Research Program of China under Grant No 2011CBA00607the National Natural Science Foundation of China under Grant No 61376097+1 种基金the Zhejiang Provincial Natural Science Foundation of China under Grant No LR14F040001Specialized Research Fund for the Doctoral Program of Higher Education of China under Grant No20130091110025
文摘An SF6/CF4 cyclic reactive-ion etching （RIE） method is proposed to suppress the surface roughness and to opti- mize the morphology of Ge fin, aiming at the fabrication of superior Ge FinFETs for future CMOS technologies. The surface roughness of the Ge after RIE can be sufficiently reduced by introducing SF6-O2 etching steps into the CF4-O2 etching process, while maintaining a relatively large ratio of vertical etching over horizontal etching of the Ge. As a result, an optimized rms roughness of 0.9nm is achieved for Ge surfaces after the SF6/CF4 cyclic etching with a ratio of greater than four for vertical etching over horizontal etching of the Ge, by using a proportion of 60% for SF6-O2 etching steps.
文摘在红外探测领域,InSb材料已经大规模地被用于制造3~5μm波长范围的焦平面阵列探测器。对更大规模、更高性能探测器的需求日益增长,而该类探测器需要在更大尺寸、更高质量的晶片上制备。所以,对4 in InSb晶片加工技术进行了研究。通过优化研磨、抛光工艺参数,最终获得总厚度偏差小于等于10μm、翘曲度小于等于20μm、表面粗糙度小于1 nm、表面质量优的4 in InSb晶片,提高了加工效率,能够满足大规模高质量红外焦平面探测器的使用需求。
基金supported by the National Natural Science Foundations of China(Grant No.11772046)。
文摘We study the coupled flow and heat transfer of power-law nanofluids on a non-isothermal rough rotating disk subjected to a magnetic field.The problem is formulated in terms of specified curvilinear orthogonal coordinate system.An improved BVP4C algorithm is proposed,and numerical solutions are obtained.The influence of volume fraction,types and shapes of nanoparticles,magnetic field and power-law index on the flow,and heat transfer behavior are discussed.The obtained results show that the power-law exponents(PLE),nanoparticle volume fraction(NVF),and magnetic field inclination angle(MFIA)have almost no effects on velocities in the wave surface direction,but have small or significant effects on the azimuth direction.The NVF has remarkable influences on local Nusselt number(LNN)and friction coefficients(FC)in the radial direction and the azimuth direction(AD).The LNN increases with NVF increasing while FC in AD decreases.The types of nanoparticles,magnetic field strength,and inclination have small effects on LNN,but they have remarkable influences on the friction coefficients with positively correlated heat transfer rate,while the inclination is negatively correlated with heat transfer rate.The size of the nanoparticle shape factor is positively correlated with LNN.
基金supported by Defense Industrial Technology Development Program (Grant No. JCKY2021605B003)National Natural Science Foundation of China for Creative Research Groups (Grant No. 51921003)Postgraduate Research & Practice Innovation Program of Jiangsu Province (Grant No. KYCX20_0181)。
文摘In flat jet electrochemical milling, the electrolyte forms a backward parallel flow after impacting the workpiece, resulting in a weak current density distribution on the workpiece. Poor surface quality usually occurs on the machined titanium alloy surface because it inevitably suffers from the weak current density. In this study, a method of flat jet electrochemical milling with tailoring the backward parallel flow was proposed to eliminate the negative effects caused by the weak current density. Multiphysics simulations are carried out to comprehend the mechanism of flat jetEC milling with tailoring backward parallel flow and better construct the novel tool electrode.Experiments on flat jet electrochemical milling of TC4 alloy with and without tailoring backward parallel flow are conducted. The results reveal that, compared with flat jet electrochemical milling without tailoring backward parallel flow, the recommended tool reduces the surface roughness by86% to 93%, and improves the material removal rate by 93% to 163% with different feed rates.Additionally, the recommended tool is more conducive to maintaining the inherent hardness of the material. Finally, a surface with low Sa of 0.37 μm is obtained.
