Papers by Keyword: Atomic Force Microscope (AFM)

Abstract: An improved arc welding method was developed to fabricate carbon nanotube probe under direct view of optical microscope. The new fabrication method here needs not coat silicon probe in advance with metal film, which greatly reduces the fabrication’s difficulty. An easy method for shortening the nanotube probe was also developed. The improved fabrication method here is simple and reliable. The fabricated carbon nanotube probe showed good properties of higher length-to-diameter aspect ratio, better wear characteristics than silicon probe.

Abstract: The mechanism responsible for scanning probe field-induced oxidation in ambient air is attributed to an electrochemical process, i.e., anodic oxidation or anodization,after the analyses is given of a surface of a sample exposed to air. The effects of biases, tip speeds on morphology of field-induced oxidation, are introduced and deduced in the form of kinetics formula of oxidation growth. The field-induced oxidation of hydrogen-passivated Si (Si:H)using contact-mode AFM in air at room temperature is investigated. The result achieved from the experiment and that drawn from theoretical analysis are identical, which indicates the accuracy of the experimental operation.This experiment suggested that it may be used for further investigation of field-induced oxidation technology.

Abstract: Colloidal probe atomic force microscopy is a very useful tool in the study of colloidal interactions. Although this technique has been applied to study interactions between a particle and a polarized electrode during electrodeposition, it has never been used to study interactions in high electric fields as encountered in electrophoretic deposition. In this work, a preliminary study was undertaken to verify whether colloidal probe AFM could be used to measure the electrophoretic force on a particle. It was found that the electrophoretic force could be detected by colloidal probe AFM under certain circumstances. In order to prevent that the contribution of the cantilever on the measurement of the electrophoretic force becomes large, the charge on the cantilever should be small compared to the charge of the particle, which is attached to the cantilever. Moreover, the area of cantilever surface which is oriented parallel to the electric field should be small to minimize the contribution of the cantilever.

Abstract: The hydrogen influence on the microstructure of the austenitic-ferritic Cr22-Ni5-Mo3 stainless steel was investigated. Cathodic hydrogen charging was performed electrochemically from aqueous solution of 0.1M H2SO4 with hydrogen entry promoter addition. The aim of this study was to reveal microstructural changes appearing during the hydrogen charging and particularly to clarify the occurrence of phase transformations induced by hydrogen. The specific changes in both phases of steel were observed. In the ferritic phase, strong increase of dislocation density was noticed. Longer time of hydrogen charging leaded also to the strips and twin plates formation in ferrite phase. In the austenitic phase, the generation of stacking faults, followed by the formation of α' martensite was remarked.

Abstract: Homogeneous nano-thin layer of hydroxyapatite (HAp) nanocrystals on the gold surface was fabricated by an electrophoretic deposition method (EPD); the HAp nanocrystals were dispersed into ethanol and the applied voltage was varied. The HAp nanocrystals were prepared by a wet method at 4 °C and 80 °C, which were characterized by X-ray diffraction and Fourier-transform infrared spectroscopy. The micro-thin layer of HAp nanocrystals was initially formed, and the ultrasonic treatments can remove the surplus nanocrystals from the surface. The nanostructure of the surface was investigated by atomic force microscopy and contact angle measurement. The thickness of coating layers was approximately 20nm and the root mean square (RMS) roughness was under 6.6 nm, which was clearly depended on the crystal sizes, applied voltages and applied times.

Abstract: When atomic force microscopy is used to retrieve nanomechanical surface properties of materials, unsuspected measurement and instrumentation errors may occur. In this work, some error sources are investigated and operating and correction procedures are proposed in order to maximize the accuracy of the measurements. Experiments were performed on sapphire, Ni, Co and Ni-30%Co samples. A triangular pyramidal diamond tip was used to perform indentation and scratch tests, as well as for surface visualization. It was found that nonlinearities of the z-piezo scanner, in particular the creep of the z-piezo, and errors in the determination of the real dimensions of tested areas, are critical parameters to be considered. However, it was observed that there is a critical load application rate, above which the influence of the creep of the z-piezo can be neglected. Also, it was observed that deconvolution of the tip geometry from the image of the tested area is essential to obtain accurate values of the dimensions of indentations and scratches. The application of these procedures enables minimizing the errors in nanomechanical property measurements using atomic force microscopy techniques.

Abstract: Deposition of thin plasma polymer films as final layer on organic coatings can provide one promising solution to tailor the surface properties offering third functionality and increased mechanical properties. The present work is dedicated to the study of the barrier properties of polyurethane coil coatings modified by different plasma polymerization processes. Microwave (MW) and radio frequency (RF) plasmas were used to deposit thin films with different composition from various precursor mixtures. Transmission electron microscopy (TEM) and atomic force microscopy (AFM) were used to reveal the evolution of the plasma treated coil coatings during weathering tests. Electrochemical impedance spectroscopy (EIS) was employed to study the barrier properties of the coatings. The results show a degradation effect of the plasma treatment on the barrier properties of the coil coatings especially in the case of the oxygen-containing plasmas. However addition of a fluorinecontaining component to the precursor mixture leads to the elimination of the negative effect of the plasma treatment on the barrier properties of the coil coatings. The fluorine-containing films exhibit higher weathering stability in comparison with the fluorine-free ones.

Abstract: Chain reorientation may be induced in polyvinylidene fluoride (PVDF) in its β-phase by applying a deformation perpendicular to the pre-oriented polymeric chains. This reorientation begins right after the yielding point and seems to be completed when the stress-strain curve stabilizes. As the deformation process plays an important role in the processing and optimisation properties of the material for practical applications, different deformation stress was applied to the PVDF lamellas and their topographic change and piezoelectric response were studied by means of scanning force microscopy in a piezo-response mode. The experimental results confirm the previously observed chain reorientation that occurs right after the yielding point and that is completed when the yielding region is passed. This reorientation is accompanied by a stretching of the granular structures observed in the topographical images and variations in the domain response. The observed results help to explain the variations in the macroscopic response of the material.

Abstract: Investigation of the microstructure, properties and biocompatibility of the Ti-6Al-4V alloy nitrided under glow discharge was performed. The microstructural analyses were carried out using light microscopy, X-ray diffraction, analytical scanning and transmission electron microscopy. Phase identifications and chemical composition of the layer and bulk material (substrate) were determined by electron diffraction and energy dispersive X-ray spectrometry. Atomic force microscopy was applied for layer surface topography measurements. Microhardness and Young’s modulus measurements as well as frictional wear resistance and corrosion resistance tests were performed. The investigation revealed a clear correlation between the micro/nanostructure and surface topography of the layer with its micromechanical, tribological and corrosion properties. In-vitro examinations of biofilm and cell behaviour show that the nitrided Ti-6Al-4V alloy exhibits good biocompatibility.

Abstract: The paper gives an overview of recent research activities that explore new pathways to achieve selective structurization of semiconductor surfaces by electrochemical deposition or dissolution techniques. Of a particular emphasis are pathways that are based on a two step procedure: First, locally a semiconductor surface is selectively activated (or de-activated) using techniques with a high lateral resolution (focussed ion electron beam, or AFM). In a second step, an electrochemical reaction (dissolution or material deposition) is selectively carried out at sensitized surface locations. Different examples of this strategy are given including selective suppression of a surface by damage induced amorphization. Additionally, smart structuring approaches involving self-organization of deposition or dissolution processes are shortly discussed.