To indirectly investigate the dislocation behavior of Fe-36wt%Ni Invar alloy by the etch pit method,polished Invar specimens were etched by a solution containing 4 g copper sulfate,20 mL hydrochloric acid,and 20 mL de...To indirectly investigate the dislocation behavior of Fe-36wt%Ni Invar alloy by the etch pit method,polished Invar specimens were etched by a solution containing 4 g copper sulfate,20 mL hydrochloric acid,and 20 mL deionized water for 2 min.Etch pits in the etched surfaces were observed.All the etch pits in one specific grain exhibited similar shapes,which are closely related to the grain orientations.These etch pits were characterized as dislocation etch pits.It was observed that etch pits arranged along grain boundaries,gathered at grain tips and strip-like etch pit clusters passed through a number of grains in the pure Invar specimens.After the addition of a small amount of alloying elements,the identification of a single dislocation etch pit is challenging compared with the pure Invar alloy.Thus,the observation of etch pits facilitates the investigation on the dislocation behavior of the pure Invar alloy.In addition,alloying elements may affect the densities and sizes of etch pits.展开更多
The analysis of threading dislocation density(TDD)in Ge-on-Si layer is critical for developing lasers,light emitting diodes(LEDs),photodetectors(PDs),modulators,waveguides,metal oxide semiconductor field effect transi...The analysis of threading dislocation density(TDD)in Ge-on-Si layer is critical for developing lasers,light emitting diodes(LEDs),photodetectors(PDs),modulators,waveguides,metal oxide semiconductor field effect transistors(MOS-FETs),and also the integration of Si-based monolithic photonics.The TDD of Ge epitaxial layer is analyzed by etching or transmission electron microscope(TEM).However,high-resolution x-ray diffraction(HR-XRD)rocking curve provides an optional method to analyze the TDD in Ge layer.The theory model of TDD measurement from rocking curves was first used in zinc-blende semiconductors.In this paper,this method is extended to the case of strained Ge-on-Si layers.The HR-XRD 2θ/ωscan is measured and Ge(004)single crystal rocking curve is utilized to calculate the TDD in strained Ge epitaxial layer.The rocking curve full width at half maximum(FWHM)broadening by incident beam divergence of the instrument,crystal size,and curvature of the crystal specimen is subtracted.The TDDs of samples A and B are calculated to be 1.41×10~8cm^(-2)and 6.47×10~8cm^(-2),respectively.In addition,we believe the TDDs calculated by this method to be the averaged dislocation density in the Ge epitaxial layer.展开更多
The limiting length of tunnels, llim, of Al foil electro-etched in HCl-H2SO4 solution and the corresponding anodic polarization curves in the same solution were measured. It is found that there is a dependence of llim...The limiting length of tunnels, llim, of Al foil electro-etched in HCl-H2SO4 solution and the corresponding anodic polarization curves in the same solution were measured. It is found that there is a dependence of llim on the potential difference, △φ, between the pitting potential, φpit, and the corrosion potential, φcorr, of Al foil, when the temperature and H2SO4 concentration of HCl-H2SO4 electrolyte are changed. The dynamic equation on the tunnel growing and the linear equation between llim and △φ were deduced by analyzing the relationship among the over-potential on Al foil surface, the transport over-potential in tunnel solution and the over-potential at tunnel tip during the electro-etching. The results show that the growing velocity of tunnels decreases with their extending in length and the changing trend of llim can be judged by measuring △φ, which supplies a convenient access to explore new kinds of etchants.展开更多
The morphologies of tunnel tips in diferent stages for aluminum foils during DC etching in 1.5 mol/L HCl solution at 90 C were observed by field emission scanning electron microscopy(FE-SEM).A novel model was proposed...The morphologies of tunnel tips in diferent stages for aluminum foils during DC etching in 1.5 mol/L HCl solution at 90 C were observed by field emission scanning electron microscopy(FE-SEM).A novel model was proposed to describe the morphological evolution of tunnel tips throughout the growth processes.In the pit nucleation stage,the pits vary from the hemispherical to half-cubic shapes due to the activation of pit tips from the center to the edge.During the tunnel growth stage,the pits dissolve toward the depth direction and develop into the tunnels,and their tips remain flat.In the tip passivation stage,as the passivation of tunnel tips speeds up from the edge to the center,the tunnel tips change from flat shapes to three-dimensional protrusions.The mechanism may be attributed to the order of activation or passivation on the tunnel tips changed in diferent stages.展开更多
Pure potassium dihydrogen phosphate (KDP) crystals and KDP doped with L-alanine have been grown by slow evaporation technique at room temperature. Grown crystals have been characterized using powder X-ray diffraction,...Pure potassium dihydrogen phosphate (KDP) crystals and KDP doped with L-alanine have been grown by slow evaporation technique at room temperature. Grown crystals have been characterized using powder X-ray diffraction, (XRD), Energy Dispersive X-ray spectroscopy (EDX) and Fourier Transform Infrared spectroscopy (FTIR). The presence of L-alanine into pure KDP crystal was confirmed by FTIR and EDX spectra. Crystal structure has been studied by XRD. Pure KDP and L-alanine doped KDP crystals both possessed tetragonal structure. The transparency is found to increase with the increase of doping concentrations of the grown crystals as observed by UV-Vis spectra. A.C. electrical conductivity of grown crystals along the growth axis was carried out at various temperatures ranging from 35?C - 400?C. Dielectric constant and dielectric losses are measured as a function of temperature and this study reveals the contribution of space charge polarization. Crystal defects and surface morphology are studied by dissolution solvent technique and reveals the step growth mechanism for both pure and doped crystals.展开更多
A commercial epi-ready(201)β-Ga_(2)O_(3) wafer was investigated upon diamond sawing into pieces measuring 2.5×3 mm^(2).The defect structure and crystallinity in the cut samples has been studied by X-ray diffract...A commercial epi-ready(201)β-Ga_(2)O_(3) wafer was investigated upon diamond sawing into pieces measuring 2.5×3 mm^(2).The defect structure and crystallinity in the cut samples has been studied by X-ray diffraction and a selective wet etching technique.The density of defects was estimated from the average value of etch pits calculated,including near-edge regions,and was obtained close to 109 cm^(-2).Blocks with lattice orientation deviated by angles of 1-3 arcmin,as well as non-stoichiometric fractions with a relative strain about(1.0-1.5)×10^(-4)in the[201]direction,were found.Crystal perfection was shown to decrease significantly towards the cutting lines of the samples.To reduce the number of structural defects and increase the crystal perfection of the samples via increasing defect motion mobility,the thermal annealing was employed.Polygonization and formation of a mosaic structure coupled with dislocation wall appearance upon 3 h of annealing at 1100℃ was observed.The fractions characterized by non-stoichiometry phases and the block deviation disappeared.The annealing for 11 h improved the homogeneity and perfection in the crystals.The average density of the etch pits dropped down significantly to 8×10^(6) cm^(-2).展开更多
文摘To indirectly investigate the dislocation behavior of Fe-36wt%Ni Invar alloy by the etch pit method,polished Invar specimens were etched by a solution containing 4 g copper sulfate,20 mL hydrochloric acid,and 20 mL deionized water for 2 min.Etch pits in the etched surfaces were observed.All the etch pits in one specific grain exhibited similar shapes,which are closely related to the grain orientations.These etch pits were characterized as dislocation etch pits.It was observed that etch pits arranged along grain boundaries,gathered at grain tips and strip-like etch pit clusters passed through a number of grains in the pure Invar specimens.After the addition of a small amount of alloying elements,the identification of a single dislocation etch pit is challenging compared with the pure Invar alloy.Thus,the observation of etch pits facilitates the investigation on the dislocation behavior of the pure Invar alloy.In addition,alloying elements may affect the densities and sizes of etch pits.
基金Project supported by the Research Plan in Shaanxi Province,China(Grant No.2016GY-085)the Opening Project of Key Laboratory of Microelectronic Devices&Integrated Technology,Institute of Microelectronics,Chinese Academy of Sciences(Grant No.90109162905)+1 种基金the Fundamental Research Funds for the Central Universities(Grant No.17-H863-04-ZT-001-019-01)the National Natural Science Foundation of China(Grant Nos.61704130 and 61474085)
文摘The analysis of threading dislocation density(TDD)in Ge-on-Si layer is critical for developing lasers,light emitting diodes(LEDs),photodetectors(PDs),modulators,waveguides,metal oxide semiconductor field effect transistors(MOS-FETs),and also the integration of Si-based monolithic photonics.The TDD of Ge epitaxial layer is analyzed by etching or transmission electron microscope(TEM).However,high-resolution x-ray diffraction(HR-XRD)rocking curve provides an optional method to analyze the TDD in Ge layer.The theory model of TDD measurement from rocking curves was first used in zinc-blende semiconductors.In this paper,this method is extended to the case of strained Ge-on-Si layers.The HR-XRD 2θ/ωscan is measured and Ge(004)single crystal rocking curve is utilized to calculate the TDD in strained Ge epitaxial layer.The rocking curve full width at half maximum(FWHM)broadening by incident beam divergence of the instrument,crystal size,and curvature of the crystal specimen is subtracted.The TDDs of samples A and B are calculated to be 1.41×10~8cm^(-2)and 6.47×10~8cm^(-2),respectively.In addition,we believe the TDDs calculated by this method to be the averaged dislocation density in the Ge epitaxial layer.
基金Project supported by University New Materials Disciplines Construction Program of Beijing, China
文摘The limiting length of tunnels, llim, of Al foil electro-etched in HCl-H2SO4 solution and the corresponding anodic polarization curves in the same solution were measured. It is found that there is a dependence of llim on the potential difference, △φ, between the pitting potential, φpit, and the corrosion potential, φcorr, of Al foil, when the temperature and H2SO4 concentration of HCl-H2SO4 electrolyte are changed. The dynamic equation on the tunnel growing and the linear equation between llim and △φ were deduced by analyzing the relationship among the over-potential on Al foil surface, the transport over-potential in tunnel solution and the over-potential at tunnel tip during the electro-etching. The results show that the growing velocity of tunnels decreases with their extending in length and the changing trend of llim can be judged by measuring △φ, which supplies a convenient access to explore new kinds of etchants.
基金the financial support by the Guangxi Hezhou Guidong Electronics Technology Co.Ltd.the Research Project of Guangxi Zhuang Autonomous Region(Nos.1346011-7 and 1298019-11)
文摘The morphologies of tunnel tips in diferent stages for aluminum foils during DC etching in 1.5 mol/L HCl solution at 90 C were observed by field emission scanning electron microscopy(FE-SEM).A novel model was proposed to describe the morphological evolution of tunnel tips throughout the growth processes.In the pit nucleation stage,the pits vary from the hemispherical to half-cubic shapes due to the activation of pit tips from the center to the edge.During the tunnel growth stage,the pits dissolve toward the depth direction and develop into the tunnels,and their tips remain flat.In the tip passivation stage,as the passivation of tunnel tips speeds up from the edge to the center,the tunnel tips change from flat shapes to three-dimensional protrusions.The mechanism may be attributed to the order of activation or passivation on the tunnel tips changed in diferent stages.
文摘Pure potassium dihydrogen phosphate (KDP) crystals and KDP doped with L-alanine have been grown by slow evaporation technique at room temperature. Grown crystals have been characterized using powder X-ray diffraction, (XRD), Energy Dispersive X-ray spectroscopy (EDX) and Fourier Transform Infrared spectroscopy (FTIR). The presence of L-alanine into pure KDP crystal was confirmed by FTIR and EDX spectra. Crystal structure has been studied by XRD. Pure KDP and L-alanine doped KDP crystals both possessed tetragonal structure. The transparency is found to increase with the increase of doping concentrations of the grown crystals as observed by UV-Vis spectra. A.C. electrical conductivity of grown crystals along the growth axis was carried out at various temperatures ranging from 35?C - 400?C. Dielectric constant and dielectric losses are measured as a function of temperature and this study reveals the contribution of space charge polarization. Crystal defects and surface morphology are studied by dissolution solvent technique and reveals the step growth mechanism for both pure and doped crystals.
基金funded by the Russian Science Foundation,project#23-29-10196。
文摘A commercial epi-ready(201)β-Ga_(2)O_(3) wafer was investigated upon diamond sawing into pieces measuring 2.5×3 mm^(2).The defect structure and crystallinity in the cut samples has been studied by X-ray diffraction and a selective wet etching technique.The density of defects was estimated from the average value of etch pits calculated,including near-edge regions,and was obtained close to 109 cm^(-2).Blocks with lattice orientation deviated by angles of 1-3 arcmin,as well as non-stoichiometric fractions with a relative strain about(1.0-1.5)×10^(-4)in the[201]direction,were found.Crystal perfection was shown to decrease significantly towards the cutting lines of the samples.To reduce the number of structural defects and increase the crystal perfection of the samples via increasing defect motion mobility,the thermal annealing was employed.Polygonization and formation of a mosaic structure coupled with dislocation wall appearance upon 3 h of annealing at 1100℃ was observed.The fractions characterized by non-stoichiometry phases and the block deviation disappeared.The annealing for 11 h improved the homogeneity and perfection in the crystals.The average density of the etch pits dropped down significantly to 8×10^(6) cm^(-2).
