External magnetic field guiding in HiPIMS to control sp(3) fraction of tetrahedral amorphous carbon films

Amorphous carbon films have many applications that require control over their sp(3) fraction to customise the electrical, optical and mechanical properties. Examples of these applications include coatings for machine parts, biomedical and microelectromechanical devices. In this work, we demonstrate the use of a magnetic field with a high-power impulse magnetron sputtering (HiPIMS) source as a simple, new approach to give control over the sp(3) fraction. We provide evidence that this strategy enhances the deposition rate by focusing the flux, giving films with high tetrahedral bonding at the centre of the deposition field and lower sp(3) fractions further from the centre. Resistive switching appears in films with intermediate sp(3) fractions. The production of thin amorphous carbon films with selected properties without the need for electrical bias opens up applications where insulating substrates are required. For example, deposition of sp(3) rich films on polymers for wear resistant coatings as well as fabrication of resistive switching devices for neuromorphic technologies that require tuning of the sp(3) fraction on insulating substrates are now possible.