AFM tip-based nanomachining with increased cutting speed at the tool-workpiece interface

This paper reports a study towards enhancing the throughput of the Atomic Force Microscope (AFM) tip-based nanomachining process by increasing the cutting speed at the interface between the tool and the workpiece. A modified AFM set-up was implemented, which combined the fast reciprocating motions of a piezoelectric actuator, on which the workpiece was mounted, and the linear displacement of the AFM stage, which defined the length of produced grooves. The influence of the feed, the feed direction and the cutting speed on the machined depth and on the chip formation was studied in detail when machining poly(methyl methacrylate). A theoretical cutting speed over 5 m/min could be achieved with this set-up when the frequency of the piezoelectric actuator reciprocating motions was 40 kHz. This is significantly better than the state of the art for AFM-based nanomachining, which is currently less than 1 m/min.</p

Insight into mechanics of AFM tip-based nanomachining: bending of cantilevers and machined grooves

Atomic force microscope (AFM) tip-based nanomachining is currently the object of intense research investigations. Values of the load applied to the tip at the free end of the AFM cantilever probe used for nanomachining are always large enough to induce plastic deformation on the specimen surface contrary to the small load values used for the conventional contact mode AFM imaging. This study describes an important phenomenon specific for AFM nanomachining in the forward direction: under certain processing conditions, the deformed shape of the cantilever probe may change from a convex to a concave orientation. The phenomenon can principally change the depth and width of grooves machined, e.g. the grooves machined on a single crystal copper specimen may increase by 50% on average following such a change in the deformed shape of the cantilever. It is argued that this phenomenon can take place even when the AFM-based tool is operated in the so-called force-controlled mode. The study involves the refined theoretical analysis of cantilever probe bending, the analysis of experimental signals monitored during the backward and forward AFM tip-based machining and the inspection of the topography of produced grooves

A new process chain for producing bulk metallic glass replication masters with micro- and nano-scale features

YesA novel process chain for serial production of polymer-based devices incorporating both micro- and nano-scale features is proposed. The process chain is enabled by the use of Zr-based bulk metallic glasses (BMG) to achieve the necessary level of compatibility and complementarity between its component technologies. It integrates two different technologies, namely laser ablation and focused ion beam (FIB) milling for micro-structuring and sub-micron patterning, respectively, thus to fabricate inserts incorporating different length scale functional features. Two alternative laser sources, namely nano-second (NS) and pico-second (PS) lasers, were considered as potential candidates for the first step in this master-making process chain. The capabilities of the component technologies together with some issues associated with their integration were studied. To validate the replication performance of the produced masters, a Zr-based BMG insert was used to produce a small batch of micro-fluidic devices by micro-injection moulding. Furthermore, an experimental study was also carried out to determine whether it would be possible by NS laser ablation to structure the Zr-based BMG workpieces with a high surface integrity whilst retaining the BMG's non-crystalline morphology. Collectively, it was demonstrated that the proposed process chain could be a viable fabrication route for mass production of polymer devices incorporating different length scale features

Research on classroom practice: A monograph for topic study group 24, ICME 11 - The introductory chapter

published_or_final_versionThe 11th International Congress on Mathematical Education (ICME 11), Monterrey, Mexico, 6-13 July 2008. In Quaderni di Ricerca in Didattica, 2009, n. S4, p. 1-

Substrate surface patterning by optical near field modulation around colloidal particles immersed in a liquid

Optical near field enhancements in the vicinity of particles illuminated by laser light are increasingly recognized as a powerful tool for nanopatterning applications, but achieving sub-wavelength details from the near-field distribution remains a challenge. Here we present a quantitative analysis of the spatial modulation of the near optical fields generated using single 8 ps, 355 nm (and 532 nm) laser pulses around individual colloidal particles and small close packed arrays of such particles on silicon substrates. The analysis is presented for particles in air and, for the first time, when immersed in a range of liquid media. Immersion in a liquid allows detailed exploration of the effects on the near field of changing not just the magnitude but also the sign of the refractive index difference between the particle and the host medium. The level of agreement between the results of ray tracing and Mie scattering simulations, and the experimentally observed patterns on solid surfaces, should encourage further modelling, predictions and demonstrations of the rich palette of sub-wavelength surface profiles that can be achieved using colloidal particles immersed in liquids

AFM tip-based nanomachining with increased cutting speed at the tool-workpiece interface

This paper reports a study towards enhancing the throughput of the Atomic Force Microscope (AFM) tip-based nanomachining process by increasing the cutting speed at the interface between the tool and the workpiece. A modified AFM set-up was implemented, which combined the fast reciprocating motions of a piezoelectric actuator, on which the workpiece was mounted, and the linear displacement of the AFM stage, which defined the length of produced grooves. The influence of the feed, the feed direction and the cutting speed on the machined depth and on the chip formation was studied in detail when machining poly(methyl methacrylate). A theoretical cutting speed over 5 m/min could be achieved with this set-up when the frequency of the piezoelectric actuator reciprocating motions was 40 kHz. This is significantly better than the state of the art for AFM-based nanomachining, which is currently less than 1 m/min

Topological features in the ferromagnetic Weyl semimetal CeAlSi: Role of domain walls

In the ferromagnetic (FM) Weyl semimetal CeAlSi both space-inversion and time-reversal symmetries are broken. Our quantum oscillation (QO) data indicate that the FM ordering modifies the Fermi surface topology and also leads to an unusual drop in the QO amplitude. In the FM phase, we find a pressure-induced suppression of the anomalous and the loop Hall effects. This cannot be explained based on the electronic band structure or magnetic structure, both of which are nearly pressure independent. Instead, we show that a simplified model describing the scattering of Weyl fermions off FM domain walls can potentially explain the observed topological features. Our study highlights the importance of domain walls for understanding transport in FM Weyl semimetals