Jen-Ching Huang

Scratch properties of nickel thin films using atomic force microscopy

Experiments using atomic force microscopy (AFM) as a machining tool for scratching patterns on nickel thin films have been conducted with an emphasis on establishing the material scratchability or more general, the nanoscale machinability. The effects of the scratch parameters, including the applied tip force and scratch direction, on the size of the scratched geometry were investigated. The primary factors that measure the scratchability were then assessed. The scratchability of Ni as compared to that of Si was specifically evaluated and discussed. A stress-hardness analysis was also performed to further validate the experimental and correlation results. All results indicate that the Ni thin film possesses excellent scratchability and one order of magnitude higher than that of Si. Based on the correlation formula developed, Ni should be able to be precisely scratched by AFM tip with the required dimension and nanoscale accuracy and precision.

A study of the estimation method of the cutting force for a conical tool under nanoscale depth of cut by molecular dynamics.

This study uses molecular dynamics to simulate the nanoscale cutting of a Cu single crystal by a conical diamond tool. Actual nanoscale straight-line cutting experiments were performed, and the experimental results are compared with the simulation results. The heaping of copper atoms is qualitatively quite consistent with the simulation result. This paper also proposes a nanoscale contact pressure factor (NCP factor) that is applicable to the probes at different tip radii. An estimation model of the cutting force for nanoscale cutting is established. This model can estimate the cutting force during actual nanoscale cutting. Actual nanoscale cutting experiments were performed for verification, and the difference between the cutting force estimated by this model and the actual force is very small.

The study of nanoscratch and nanomachining on hard multilayer thin films using atomic force microscope

In this study, nanoscratching and nanomachining were conducted using an atomic force microscope (AFM) equipped with a doped diamond-coated probe (DDESP-10; VEECO) to evaluate the fabrication of nanopatterns on hard, Cr₂N/Cu multilayer thin films. The influence of normal force, scratch speed, and repeated scratches on the properties of hard multilayer thin films was also investigated. The nanoscratch experiments led researchers to establish a probe preparation and selection criteria (PPS criteria) to enhance the stability and accuracy of machining hard materials. Experimental results indicate that the depth of grooves produced by nanoscratching increased with an increase in normal force, while an increase in the number of scratches in a single location increased the groove depth but decreased friction. Therelationships among normal force and groove depth more closely resembled a logarithmic form than other mathematical models, as did the relationship between repeated scratching and its effect on groove depth and friction. The influence of scratch speed on friction was divided into two ranges. Between 0.1 and 2 µm/s, friction decreased logarithmically with an increase in scratch speed; however, when the speed exceeded 2 µm/s, the friction appeared stable. In this study, multilayered coatings were successfully machined, demonstrating considerable promise for the fabrication of nanopatterns in multilayered coatings at the nanoscale.

The application of neural networks in fixture planning by pattern classification

The objective of this paper is to study the fixture planning of modular fixtures for cutting by means of a computer-aided fixture system (CAFS). The fixture planning presented here integrates the database of modular fixtures, neural networks, the heuristic algorithm of fixture position and the use of Advanced Modelling Extension Release 2.1 (AME) of AutoCAD R12 as the 3D graphic interface. The function suitable for the AME environment was also controlled to obtain detailed data of the geometry and topology of the workpiece to develop the fixture planning for modular fixtures. First of all, the concept of group technology (GT) was used to establish the coding database of the modular fixture element for use in the system. This paper presents fixture planning which combines the pattern recognition capability of the neural networks and the concept of GT to group the workpieces with different patterns but identical fixture modes into the same group. After network training, the fixture mode of the workpiece to be clamped can be inferred, and the selection of the fixture elements can be completed.

Evaluation of Tribological Behavior of Al‐Co‐Cr‐Fe‐Ni High Entropy Alloy Using Molecular Dynamics Simulation

High-entropy alloys have been studied extensively for their excellent properties and performance, including outstanding strength and resistance to oxidation at high temperatures. This study employed molecular dynamics simulation to produce a high-entropy alloy containing an equal molar ratio of Al, Co, Cr, Fe, and Ni and investigated the tribological behavior of the material using a diamond tool in a vacuum environment. We also simulated a AlCoCrFeNi high-entropy alloy cooled from a high temperature molten state to 300 K in a high-speed quenching process to produce an amorphous microstructure. In a simulation of nanoscratching, the cutting force-distance curve of high-entropy alloys was used to evaluate work hardening and stick-slip. An increase in temperature was shown to reduce the scratching force and scratching resistance. Nanoscratching the high-entropy alloy at elevated temperatures provided evidence of work hardening; however, the degree of work hardening decreased with an increase in temperature. And it can also be found that when the temperature is higher, the fluctuation of the cutting force curve is greater.

Fabricating Nanostructures by Atomic Force Microscopy

In this study, we used a conductive Atomic Force Microscopy (AFM) probe to fabricate nanostructures and nanopatterns on a silicon chip using nano-oxidation technology. The height of grown oxidized nanodots tends to increase as the piezoelectric loading in nano-oxidation increases, while the number of oxidized nanodots affects the height of oxidation. In terms of patterning, the height and width of nanodots tend to decrease as the probe scanning speed increases. Moreover, in this study, we used nano-oxidation to perform complex nanopatterning, and found that complex and well-defined nanopatterns could be fabricated on a scale of 1000 ×1000 nm2. The technology proposed in this study can directly define nanostructures without limitations of the wavelength of the light source and light diffraction. The technology has the advantages of low cost and great potential for development.

The influence of the bias type, doping condition and pattern geometry on AFM tip‐induced local oxidation

Abstract In this article, the influences of bias types, doping conditions, and pattern geometry on the kinetics of oxides on Si substrates produced by AFM tip‐induced local oxidation were investigated. The growth height of oxide using a +10V sample bias is higher than that when using a ‐10V tip bias, while the magnitude of sample‐tip bias is kept the same. A polygon concept was introduced to produce a circular pattern. The effects of the number of sides in the polygon on the height of oxide circular pattern were explored. It was observed that the oxide height increases with the number of sides of the polygon pattern when the radius is the same. And the oxide is higher on p‐Si(100) than on p‐Si(111) or n‐Si(111).

The study on the atomic force microscopy base nanoscale electrical discharge machining

This study proposes an innovative atomic force microscopy (AFM) based nanoscale electrical discharge machining (AFM-based nanoEDM) system which combines an AFM with a self-produced metallic probe and a high-voltage generator to create an atmospheric environment AFM-based nanoEDM system and a deionized water (DI water) environment AFM-based nanoEDM system. This study combines wire-cut processing and electrochemical tip sharpening techniques on a 40-µm thick stainless steel sheet to produce a high conductive AFM probes, the production can withstand high voltage and large current. The tip radius of these probes is approximately 40 nm. A probe test was executed on the AFM using probes to obtain nanoscales morphology of Si wafer surface. The silicon wafer was as a specimen to carry out AFM-base nanoEDM process in atmospheric and DI water environments by AFM-based nanoEDM system. After experiments, the results show that the atmospheric and DI water environment AFM-based nanoEDM systems operate smoothly. From experimental results, it can be found that the electric discharge depth of the silicon wafer at atmospheric environments is a mere 14.54 nm. In a DI water environment, the depth of electric discharge of the silicon wafer can reach 25.4 nm. This indicates that the EDM ability of DI water environment AFM-based nanoEDM system is higher than that of atmospheric environment AFM-based nanoEDM system. After multiple nanoEDM process, the tips become blunt. After applying electrochemical tip sharpening techniques, the tip radius can return to approximately 40 nm. Therefore, AFM probes produced in this study can be reused.

The Study of Single-walled Nanotube Reinforced Epoxy Composites by Molecular Dynamics

Recently, enhance the mechanical property of nanocomposite were used by adding the nanotubes. The mechanical properties of the nanocomposite were affected by interfacial bonding energy between nanotubes and polymers. In this paper, the interfacial bonding energy and Youngs moulds of single-walled nanotube (SWNT) reinforced epoxy composites were investigated using molecular dynamics (MD) simulations based on a cured epoxy resin model, which was constructed by incorporating three-dimensional crosslinks formed during curing reaction. The structure types of SWNT include the armchair, zigzag and chiral was used in this study. After simulation, adding SWNT in the epoxy resin really has been reinforced effect, and the larger chiral angle of SWNT the better to strengthen. The study also calculated the interfacial bonding energy between the epoxy and the SWNT affects the ability of strengthening to the composite of SWNT. Within the range of 273K-473K, the temperature has a little influence on Youngs moulds of SWNT reinforced epoxy composites.

A study of the nanomachining and nanopatterning on different materials using atomic force microscopy

This study investigated the nanomachining and nanopatterning on different materials using an atomic force microscope. Straight-line nanomachining was applied to materials, namely, mica, polycarbonate (PC), and gold, under different loading forces in order to understand the appearance and the accumulation of chips of different materials after nanomachining. This study discusses nanopatterning capabilities upon by NanoLithography software on PC, and gold. The results show that the loading force of the probe is greater, the cutting depth would also increase, and the trend showed logarithmic. And the chip accumulation behaviour on mica, PC and gold is different. This study successfully fabricated micro-scaled Chinese characters on PC and circular nano-patterns with a diameter of 500 nm and complex nano-patterns (1,000 nm ´ 1,000 nm) by the linear combination on the gold sample. It found that segments of circular shape consisting of straight lines can affect the outside shape of the circle.