A comprehensive analysis of the electrical current passing through the tip-substrate junction during oxidation of silicon by scanning probe microscopy (SPM) is presented. This analysis of experimental results under dc-bias conditions resolves the role of electronic and ionic contributions, especially for the initial stages of the reaction, determines the effective contact area of the tip-substrate junction, and unifies the roles of space charge and meniscus formation. In Part I of this work, we demonstrate that SPM oxidation is governed by a maximum charge density generated by electronic species within the junction at the onset of the oxidation process. Excess charge is channeled into lateral diffusion, keeping the charge density within the reaction zone constant and reducing the aspect ratio of the resulting oxide features. A uniform charge density implies that SPM oxides contain a fixed defect concentration, in accordance with the space-charge model. The effective (electrical) thickness of SPM oxides determined by these defects is investigated by Fowler-Nordheim analysis. We conclude that most of the electrical current involved in high voltage SPM oxidation of Si does not actually induce surface oxide growth, and that lateral diffusion and small aspect ratios are unavoidable aspects of contact-mode conditions.

A new technique for producing nanometre scale patterns on thin layers (<30 nm thick) of PMMA on silicon is described. The method consists of inducing the local modification of the PMMA by applying a positive voltage between the silicon and an atomic force microscope (AFM) tip. At voltages larger than 28 V, it is observed that a hole is directly produced on the PMMA. The silicon surface is simultaneously oxidized even in the case where a hole has not been created. Monitoring of the electrical current through the AFM tip during the application of the voltage allows elucidating the mechanism of the PMMA removal. The process is used to define nanometre scale electrodes by combining the AFM lithography with electron beam lithography, metal deposition and lift-off processes.

The findings demonstrate that although Handexos meets the initial functional requirements and underlines the potential for assisting SCI and post-stroke subjects in ADLs, several aspects such as mechanical complexity and low adaptability to different hand sizes need to be further addressed. Implications for Rehabilitation Wearable robotics devices could improve the activities of daily living in patients with spinal cord injury or stroke. They could be a tool for rehabilitation of the upper limb. Further usability tests to improve this type of tools are recommended.