Si/SiC heterostructures with different growth temperatures were prepared on 6 HSiC(0001)by LPCVD.Current mode atomic force microscopy and transmission electron microscopy were employed to investigate the electrical pr...Si/SiC heterostructures with different growth temperatures were prepared on 6 HSiC(0001)by LPCVD.Current mode atomic force microscopy and transmission electron microscopy were employed to investigate the electrical properties and crystalline structure of Si/SiC heterostructures.Face-centered cubic(FCC)on hexagonal close-packing(HCP)epitaxy of the Si(111)/SiC(0001)heterostructure was realized at 900°C.As the growth temperature increases to1050°C,the<110>preferred orientation of the Si film is observed.The Si films on 6 H-SiC(0001)with different growth orientations consist of different distinctive crystalline grains:quasi-spherical grains with a general size of 20μm,and columnar grains with a typical size of 7μm×20μm.The electrical properties are greatly influenced by the grain structures.The Si film with<110>orientation on SiC(0001)consists of columnar grains,which is more suitable for the fabrication of Si/SiC devices due to its low current fluctuation and relatively uniform current distribution.展开更多
Self-sensing and –actuating probes optimized for conventional tapping mode atomic force microscopy (AFM) are described. 32-kHz quartz tuning forks with a chemically etched and focus ion beam (FIB) sharpened (curvatur...Self-sensing and –actuating probes optimized for conventional tapping mode atomic force microscopy (AFM) are described. 32-kHz quartz tuning forks with a chemically etched and focus ion beam (FIB) sharpened (curvature radii are 5-10 nm) tungsten tip are stable at air and liquid nitrogen atmosphere and at a wide range of temperatures. If driven at constant frequency, the scan speed of such sensors can be up to 3 Hz. AFM was performed on polymer samples in order to study the stability and applicability of these sensor for investigation of soft materials with high dynamical tendencies.展开更多
Fracture processes in ship-building structures are in many cases of a 3-D character. A finite element （FE） model of an all fracture mode （AFM） specimen was built for the study of 3-D mixed mode crack fracture beha...Fracture processes in ship-building structures are in many cases of a 3-D character. A finite element （FE） model of an all fracture mode （AFM） specimen was built for the study of 3-D mixed mode crack fracture behavior including modes Ⅰ,Ⅱ, and Ⅲ. The stress intensity factors （SIFs） were calculated by the modified virtual crack closure integral （MVCCI） method, and the crack initiation angle assessment was based on a recently developed 3-D fracture criterion--the Richard criterion. It was shown that the FE model of the AFM-specimen is applicable for investigations under general mixed mode loading conditions, and the computational results of crack initiation angles are in agreement with some available experimental findings. Thus, the applicability of the FE model of the AFM-specimen for mixed mode loading conditions and the validity of the Richard criterion can be demonstrated.展开更多
相位成像是轻敲模式下原子力显微镜(tapping mode atomic force microscope,TM-AFM)最具有特色的成像方式。本文以获得高质量的相位像为主要研究目的,利用Euler-Bernoulli(欧拉-伯努利)梁方程,将系统动力学模型简化为基于支承运动的弹...相位成像是轻敲模式下原子力显微镜(tapping mode atomic force microscope,TM-AFM)最具有特色的成像方式。本文以获得高质量的相位像为主要研究目的,利用Euler-Bernoulli(欧拉-伯努利)梁方程,将系统动力学模型简化为基于支承运动的弹簧谐振子模型,推导出相位与激励频率之间的关系。实验结果与理论分析一致,这一结论对于寻找TM-AFM操作中最合适的激励频率范围具有重要意义。展开更多
The interaction of proteins with solid surfaces is a fundamental phenomenon in the biomaterials field. We investigated, using atomic force microscopy (AFM), the interactions of a recombinant amelogenin with titanium, ...The interaction of proteins with solid surfaces is a fundamental phenomenon in the biomaterials field. We investigated, using atomic force microscopy (AFM), the interactions of a recombinant amelogenin with titanium, a biphasic calcium phosphate (BCP) and mica. The unbinding processes were compared to those of an earlier studied protein, namely fibrinogen. Force spectroscopy (AFM) experiments were carried out at 0 ms, 102 ms, 103 ms and 104 ms of contact time. In general, the rupture forces increased as a function of interaction time. The unbinding forces of amelogenin interacting with the BCP surface were always stronger than those of the amelogenin-titanium system. The unbinding forces of fibrinogen interacting with the BCP surface were always much stronger than those of the fibrinogen-titanium system. For the most part, this study provides direct evidence that recombinant amelogenin binds more strongly than fibrinogen on the studied substrates.展开更多
Real-time atomic force microscopy (AFM) imaging revealed for the first time, the detailed growth/dissolution mechanism of Lauryl glycol (LG) or 1, 2 dodecanediol molecules on HOPG at the nano-level after recrystallizi...Real-time atomic force microscopy (AFM) imaging revealed for the first time, the detailed growth/dissolution mechanism of Lauryl glycol (LG) or 1, 2 dodecanediol molecules on HOPG at the nano-level after recrystallizing them from chloroform solution. At the early stage of recrystallization, parallelogram-like-structures having lengths of several microns and distinct widths (between ~ 100 - 400 nm) were observed. Growth/dissolution behavior of these parallelogram-like-structures as a function of time was investigated. While dissolution occurred along all three dimensions, growth was found to be strictly two dimensional. Both the growth and dissolution process were found to be logarithmic in nature. The average growth rates along their length and width were found to be 11 nm/min and 1.5 nm/min respectively. Average dissolution rate in percentage on HOPG surface was found to be ~ 0.078%/min. Based upon the recrystallization of LG molecules schematics are drawn for a better understanding of the recrystallization process.展开更多
In this work, we investigate the Co-Si reaction, the Co growth mode at room temperature, diffusion be- haviour as well as morphology evolution during annealing on both H-terminated and clean Si(001) and Si(111) sur- f...In this work, we investigate the Co-Si reaction, the Co growth mode at room temperature, diffusion be- haviour as well as morphology evolution during annealing on both H-terminated and clean Si(001) and Si(111) sur- faces. From in-situ X-ray photoelectron spectroscopy (XPS) investigation, “Co-Si” reaction appears to occur on both H-terminated and clean surfaces at room temperature (RT) and the silicide crystallinity is improved upon annealing. Co growth mode on H-terminated Si surfaces occurs in a pseudo layer-by-layer manner while small close-packed is- land growth mode is observed on the clean Si surface. Upon annealing at different temperatures, Co atom concentra- tion decreases versus annealing time, which in part is attributed to Co atoms inward diffusion. The diffusion behav- iour on both types of surfaces demonstrates a similar trend. Morphology study using ex-situ atomic force microscopy (AFM) shows that the islands formed on Si(001) surface after annealing at 700 °C are elongated with growth direc- tions alternate between the two perpendicular [ 110 ] and [110] directions. Triangular islands are observed on Si (111) surface.展开更多
基金Supported by the National Key Research and Development Program of China(2018YFB2200500)the National Natural Science Foundation of China(51402230,51177134,21503153)+1 种基金Natural Science Basic Research Plan in Shaanxi Province of China(2017JM6075,2015JM6282)Scientific Research Program Funded by Shaanxi Provincial Education Department(17JK0335)。
文摘Si/SiC heterostructures with different growth temperatures were prepared on 6 HSiC(0001)by LPCVD.Current mode atomic force microscopy and transmission electron microscopy were employed to investigate the electrical properties and crystalline structure of Si/SiC heterostructures.Face-centered cubic(FCC)on hexagonal close-packing(HCP)epitaxy of the Si(111)/SiC(0001)heterostructure was realized at 900°C.As the growth temperature increases to1050°C,the<110>preferred orientation of the Si film is observed.The Si films on 6 H-SiC(0001)with different growth orientations consist of different distinctive crystalline grains:quasi-spherical grains with a general size of 20μm,and columnar grains with a typical size of 7μm×20μm.The electrical properties are greatly influenced by the grain structures.The Si film with<110>orientation on SiC(0001)consists of columnar grains,which is more suitable for the fabrication of Si/SiC devices due to its low current fluctuation and relatively uniform current distribution.
文摘Self-sensing and –actuating probes optimized for conventional tapping mode atomic force microscopy (AFM) are described. 32-kHz quartz tuning forks with a chemically etched and focus ion beam (FIB) sharpened (curvature radii are 5-10 nm) tungsten tip are stable at air and liquid nitrogen atmosphere and at a wide range of temperatures. If driven at constant frequency, the scan speed of such sensors can be up to 3 Hz. AFM was performed on polymer samples in order to study the stability and applicability of these sensor for investigation of soft materials with high dynamical tendencies.
文摘Fracture processes in ship-building structures are in many cases of a 3-D character. A finite element （FE） model of an all fracture mode （AFM） specimen was built for the study of 3-D mixed mode crack fracture behavior including modes Ⅰ,Ⅱ, and Ⅲ. The stress intensity factors （SIFs） were calculated by the modified virtual crack closure integral （MVCCI） method, and the crack initiation angle assessment was based on a recently developed 3-D fracture criterion--the Richard criterion. It was shown that the FE model of the AFM-specimen is applicable for investigations under general mixed mode loading conditions, and the computational results of crack initiation angles are in agreement with some available experimental findings. Thus, the applicability of the FE model of the AFM-specimen for mixed mode loading conditions and the validity of the Richard criterion can be demonstrated.
文摘相位成像是轻敲模式下原子力显微镜(tapping mode atomic force microscope,TM-AFM)最具有特色的成像方式。本文以获得高质量的相位像为主要研究目的,利用Euler-Bernoulli(欧拉-伯努利)梁方程,将系统动力学模型简化为基于支承运动的弹簧谐振子模型,推导出相位与激励频率之间的关系。实验结果与理论分析一致,这一结论对于寻找TM-AFM操作中最合适的激励频率范围具有重要意义。
文摘The interaction of proteins with solid surfaces is a fundamental phenomenon in the biomaterials field. We investigated, using atomic force microscopy (AFM), the interactions of a recombinant amelogenin with titanium, a biphasic calcium phosphate (BCP) and mica. The unbinding processes were compared to those of an earlier studied protein, namely fibrinogen. Force spectroscopy (AFM) experiments were carried out at 0 ms, 102 ms, 103 ms and 104 ms of contact time. In general, the rupture forces increased as a function of interaction time. The unbinding forces of amelogenin interacting with the BCP surface were always stronger than those of the amelogenin-titanium system. The unbinding forces of fibrinogen interacting with the BCP surface were always much stronger than those of the fibrinogen-titanium system. For the most part, this study provides direct evidence that recombinant amelogenin binds more strongly than fibrinogen on the studied substrates.
文摘Real-time atomic force microscopy (AFM) imaging revealed for the first time, the detailed growth/dissolution mechanism of Lauryl glycol (LG) or 1, 2 dodecanediol molecules on HOPG at the nano-level after recrystallizing them from chloroform solution. At the early stage of recrystallization, parallelogram-like-structures having lengths of several microns and distinct widths (between ~ 100 - 400 nm) were observed. Growth/dissolution behavior of these parallelogram-like-structures as a function of time was investigated. While dissolution occurred along all three dimensions, growth was found to be strictly two dimensional. Both the growth and dissolution process were found to be logarithmic in nature. The average growth rates along their length and width were found to be 11 nm/min and 1.5 nm/min respectively. Average dissolution rate in percentage on HOPG surface was found to be ~ 0.078%/min. Based upon the recrystallization of LG molecules schematics are drawn for a better understanding of the recrystallization process.
文摘In this work, we investigate the Co-Si reaction, the Co growth mode at room temperature, diffusion be- haviour as well as morphology evolution during annealing on both H-terminated and clean Si(001) and Si(111) sur- faces. From in-situ X-ray photoelectron spectroscopy (XPS) investigation, “Co-Si” reaction appears to occur on both H-terminated and clean surfaces at room temperature (RT) and the silicide crystallinity is improved upon annealing. Co growth mode on H-terminated Si surfaces occurs in a pseudo layer-by-layer manner while small close-packed is- land growth mode is observed on the clean Si surface. Upon annealing at different temperatures, Co atom concentra- tion decreases versus annealing time, which in part is attributed to Co atoms inward diffusion. The diffusion behav- iour on both types of surfaces demonstrates a similar trend. Morphology study using ex-situ atomic force microscopy (AFM) shows that the islands formed on Si(001) surface after annealing at 700 °C are elongated with growth direc- tions alternate between the two perpendicular [ 110 ] and [110] directions. Triangular islands are observed on Si (111) surface.
