Mesoscopic physical removal of material using sliding nano-diamond contacts

Abstract

Wear mechanisms including fracture and plastic deformation at the nanoscale are central to understand sliding contacts. Recently, the combination of tip-induced material erosion with the sensing capability of secondary imaging modes of AFM, has enabled a slice-and-view tomographic technique named AFM tomography or Scalpel SPM. However, the elusive laws governing nanoscale wear and the large quantity of atoms involved in the tip-sample contact, require a dedicated mesoscale description to understand and model the tip-induced material removal. Here, we study nanosized sliding contacts made of diamond in the regime whereby thousands of nm3 are removed. We explore the fundamentals of high-pressure tip-induced material removal for various materials. Changes in the load force are systematically combined with AFM and SEM to increase the understanding and the process controllability. The nonlinear variation of the removal rate with the load force is interpreted as a combination of two contact regimes each dominating in a particular force range. By using the gradual transition between the two regimes, (1) the experimental rate of material eroded on each tip passage is modeled, (2) a controllable removal rate below 5 nm/scan for all the materials is demonstrated, thus opening to future development of 3D tomographic AFM.

Investigation of AFM-based machining of ferroelectric thin films at the nanoscale

“…The machined depth at 99 µN load also increases dramatically from 17 ± 2 nm for 60 nm line-separation, to 45 ± 6 nm for 10 nm line-separation, highlighting the strong effect of varying line-separation with the increased overlap between adjacent machined lines at low separations effectively enabling repeated machining over the same regions and an increased depth. 6,49 The shallowest machined depth of 0.9 ± 0.3 nm was obtained with 49 µN load at a 10 nm line-separation. This is similar to the gradual (< 1 nm) removal of material observed in a number of previous works.…”

“…1 One of the approaches to achieve this end is atomic force microscopy (AFM)-based machining, where a force is applied via a sufficiently stiff AFM probe to mechanically remove material locally from the sample. [2][3][4] Also referred to as mechanical scanning probe lithography or nanomechanical machining, this technique has been utilised in a number of recent studies to, e.g., fabricate complex arrays of 3D nanodots on polymer polycarbonate samples 5 and nanochannels of varying depth in silicon, 6 reproduce photographs on a polished aluminium disk, 7 and form single photon emitters via nanoindentations on a polymer film. 8 The analysis of AFMbased machining behaviour has been utilised to characterise the hardness of materials in nanoscale sclerometry measurements, 9 and AFM-based machining has also been used to precisely remove material from regions of the sample surface in tomography investigations.…”

Emerging Scanning Probe–Based Setups for Advanced Nanoelectronic Research

“…More recently, Scalpel AFM has been also used to etch the semiconducting surfaces of Si, Ge, and SiGe for microelectronic industry, but no electrical information was collected . In addition, Eyben et al used Scalpel AFM combined with scanning spreading resistance microscopy to etch the source‐drain and local interconnect of field effect transistors (FETs) with channels lengths of <10 nm, and constructed high‐resolution 2D carrier maps.…”

Improving the Consistency of Nanoscale Etching for Atomic Force Microscopy Tomography Applications

“…Recently, conductive AFM has been combined with nanomachining in order to perform conductance tomography, mapping electrical current as material is worn from the sample (Buckwell et al, 2015a;Celano and Vandervorst, 2017). Whereas nanofabrication requires high loading forces to rapidly machine structures, material must be removed more slowly and controllably during tomography, such that a high depth resolution is achieved through films tens to hundreds of nanometers thick (Celano et al, 2018). As such, relatively low loading forces are employed, typically in the range of a few micronewtons using boron-doped diamond probes.…”