An atomistic investigation on the mechanism of machining nanostructures when using single tip and multi-tip diamond tools

Abstract

In our previous work, a scale-up fabrication approach to cost effectively manufacturing nano-gratings over large area has been developed through diamond turning by using a multi-tip diamond tool fabricated by Focused IonBeam. The objective of this study is to gain an in-depth understanding of the mechanism of machining nanostructures on single crystal copper through diamond turning when using a single tip and a multi-tip nanoscale diamond tool. For this purpose atomistic models of a single tip tool for multi-pass cutting and a multi-tip tool for single-pass cutting were built, respectively. The nature of the cutting chip formation, dislocation nucleation and propagation, cutting forces, and temperature distribution during nanometric cutting processes were studied through molecular dynamics (MD) simulations. Results show that nanostructure generation process at steady cutting stage was governed by a strong localization of the dislocation movement and the dynamic equilibrium of chip-tool contact area. Except the apparent improvement of machining efficiency that proportional to the tool tip numbers, the nano-grooves generated by multi-tip tool also have higher centre symmetry than those machined by single tip tool.While the average tangential cutting force per tip were calculated all around 33.3 nN, a larger normal cutting force per tip being 54.1nN was observed when using a multi-tip tool. A concept of atomistic equivalent temperature was proposed and used to analysis the important features of temperature distribution during the machining process. The advantage, disadvantage and applicability of diamond turning using multi-tip tool were discussed in comparison with those of using single-tip tool. The findings suggest that diamond turning using multi-tip tool might be more applicable than using single tip tool when apply to scale-up fabrication of periodic nanostructures.

Investigation of the shape transferability of nanoscale multi-tip diamond tools in the diamond turning of nanostructures

“…The visualization of atomistic configurations was realized by VMD (Visual Molecular Dynamics) software. The color scheme of centro-symmetry parameter (CSP) value [9] is indicated in Table 2. Table 2.…”

“…The atoms with cyan and blue color represent the particle dislocations and stacking faults, respectively. As is evident from extension of the stacking faults [9]. The quality of the machined nanostructures was characterized by both the form accuracy of the machined nanostructures and the thickness of the deformed layers.…”

“…Recently nano-gratings with the pitch as lower as 150 nm were fabricated using a nanoscale multi-tip diamond tool through the diamond turning operations [8]. The effect of feed rate and the alignment issues on machining accuracy associated with the use of separate single-tip tool can be completely eliminated when using nanoscale multi-tip tools [9]. Owing to the unprecedented merits of high throughput, one-step, and highly flexible precision capabilities, this technique has led to the hope for breaking the technical bottleneck for the scale-up manufacturing nanostructures.…”

“…As the nanostructures are formed synchronously within a single cutting pass, the interactions of the deformed layers created by each tool tip might alter the material removal mechanism [9] and result in unpredictable processing defects. Although a few reports can be found in the literature preliminarily describing the high form accuracy and throughput of this technique [4][5][6][7][8], no experimental or theoretical research work has been found which investigated the dependence of 3 the form accuracy of machined nanostructures on the tool geometrical parameters.…”

“…Numerous MD nanometric cutting models were built to emulate the material removal process [10][11][12] and to study the effect of tool geometry on the machined surface quality [13][14][15]. Recently the difference in machining nanostructures between using single tip and multi-tip diamond cutting tools has also been reported [9,16].…”