Article Preview
TopIntroduction
One of the most prominent techniques in conducting nanomachining is Scanning probe microscopy, such as scanning-tunneling microscopy (STM) (Della Pia & Costantini 2013) and atomic force microscopy (AFM) (Lin, Chen et al., 2011). SPMs are used for manipulating materials down to the nanometer scale because of their inherent capability of working at atomic levels. Recently, there has been a tremendous increase in the usage of STMs and AFMs well beyond their originally intended nano metrological applications, which have opened up a variety of practical routes for ultra-precision machining. AFM, in particular has proved to be a versatile tool for conducting mechanical modification, local anodic oxidation (Lee, Ahn et al., 2012), atoms manipulation and thermal–mechanical writing (Malshe, Rajurkar et al., 2010) Many different processes have been developed based on AFM to conduct sophisticated lithography such as nanocutting, nanoscratching, and nano electro-machining (Malshe, Rajurkar et al., 2010). However, these processes have limitations regarding the type of work material, tool wear and profile of machined cavity.
Vibration Assisted Nano Impact-machining by Loose Abrasives (VANILA) process - a tip-based nanomachining process that uses a single-point AFM probe with loose abrasives and vibration assistance has been investigated and can be used to perform target specific impact-based machining of nanoscale features on hard and brittle materials such as glass and ceramics materials (James and Sundaram 2012). The process was developed based on an AFM platform in which slurry of nano diamond abrasive particles is introduced between the tool and the workpiece. The machining is conducted in tapping mode where the tool probe continuously hammers the abrasive nanoparticles, suspended in liquid medium, which in turn impacts the workpiece surface. A schematic of the VANILA process is shown in Figure 1.
Figure 1. Schematic of VANILA process, a) Tool striking the abrasive particle, b) Abrasive particle impacting workpiece surface, c) Material removal from the workpiece
The feasibility of nanoscale machining using the VANILA process was successfully demonstrated experimentally on Silicon and Borosilicate Glass substrates. Nano-cavities with circular cross-sections having depths in the range of 5-100 nm and diameters in the range of 50-300 nm were obtained on these substrates. In addition, patterns of nano-cavities, shown in Figure 2 were successfully machined to demonstrate the controllability and repeatability of the process.
Figure 2. AFM images of nano-cavity pattern machined using the VANILA Process, a) on Silicon Substrate (James & Sundaram 2012), (b) on Borosilicate Glass Substrate