Influence of the mechanical behaviour of cantilevers on the topography of nano-scale grooves during AFM tip-based machining Raheem Sadoon Jamel1,2 , Emmanuel Brousseau1 , Feodor M. Borodich1 1Cardiff School of Engineering, Cardiff University, Cardiff, United Kingdom 2Department of Mechanical Engineering, Kufa University, Iraq Contact BrousseauE@cf.ac.uk AL-Musawirs@cardiff.ac.uk 07448018696 Introduction Experimental Methodology Results and Discussions AFM tip-based nanomachining is a method, which may be used to generate micro- and nanoscale cavities on the surface of a processed workpiece [1, 2]. The existing body of research studies in this field demonstrated the implementation this technique along different processing directions. Figure 1 illustrates two of the main machining directions, which are typically found in the literature. For the so-called “forward direction” [3], it is generally assumed, such as in [4-6], that the bending of the cantilever is concave as represented with Figure 1(b). However, the deformed shape of the cantilever along this direction, and also along a direction at an inclined angle with respect to such a pure forward configuration, should depend on load conditions acting on the tip. A schematic description of the AFM set-up utilised for nanomachining is showed in Figure ‎2. An XE-100 AFM instrument from Park Systems was employed in all experiments. The tests were performed on a single crystal copper sample using a DNISP probe from Bruker. A data acquisition system was developed to capture three voltage signals as described in Table 1. The cutting speed and length of the produced grooves were 5 μm/s and 15 μm, respectively. The machining tests were conducted along the inclined forward direction as specified in Figure 3. The normal loads applied by the tip onto the sample ranged between 14 µN and 40 µN. Fn Fc Mc Z1 V2 V1 STEP3: Steady state machining (keeping the A-B voltage constant)   Z2 Backward Direction STEP 2: Z scanner moving up to reduce the PSPD voltage from V2 to V1 STEP 1: A-B voltage increasing from V1 to V2 as a result of the generation of the moment Mc 2 Convex bending Y stage motion  (a) Top view Backward Forward Sample Directions of motion for the AFM probe: Cantilever Forward direction Cantilever (concave deflection) (b) Side view Figure 1. Illustration of backward and forward AFM scratching y x z Stage DAQ PSPD Mirror Laser Controller Sample Z scanner A C B D Inclined Forward Direction CASE A: Applied force between (14 to 30 µN) Z1 V1 V2 Mc CASE B: Applied force between (33 to 39 µN) Z2 Z3 Convex Concave 3 STEP2:The Z scanner moves down increases the voltage STEP 1: A-B voltage reducing STEP3:Steady state machining  STEP4:TheZ-scanner moves down again(deflected shape changed)   Deflected shape (convex only) Aim of the research Figure 2. Schematic description of the AFM probe-based nano machining set-up. The aim of this work is to demonstrate experimentally that both deformed shapes of the cantilever can be observed during actual nanomachining tests along an inclined forward direction depending of the processing conditions utilised as specified in Figure 3. Table 1 Monitored signals Name Physical description   A-B signal position sensitive photodiode (PSPD). Z-detector signal a strain gauge sensor. Y stage signal monitoring of the lateral motion of the AFM stage. Y X Pure forward direction Inclined forward direction 22.5˚ Tip Cantilever Figure 3. Considered inclined forward cutting direction with respect to the cantilever orientation and tip geometry. Illustration of Z-Detector Signal The groove depth and width increased by over 50% after the cantilever shape change SEM and AFM inspections of produced grooves Inclined forward direction Set normal load: 33 µN Cutting direction 2 µm 200 nm Selected cross sections 4 Shearing Ploughing V0 A Tip approach stage Z1 B Indentation stage Z2 C Transition stage D Scratching stage E Tip retraction stage V1 (corresponding to a set applied force) or Material to be removed 1 2 3 4 AFM nanomachining stages 1 References Conclusions [1] Tseng A 2011 Small 7 3409-3427 [2] Yan Y, Geng Y and Hu Z 2015 Int. J. Mach. Tools Manuf. 99 1-18 [3] Tseng A, et al .J 2011 Appl. Surf. Sci. 257 9243-9250 [4] Ruan J-A and Bhushan B 1994 Journal of Tribology 116 378-388 [5] Malekian M, et al . 2010 J. Micromech. and Microeng. 20 115016 (11pp) [6] Geng Y, et al .2013 J. Vac. Sci. Technol. B 31 061802 The deflection of the probe may change from a convex to a concave shape during the actual groove formation process. 2. This phenomenon during machining significantly influences the resulting groove topography 3. It is important to take into account the non-rigid nature of AFM probes when studying AFM tip-based nanomachining.