Tailoring mechanical properties and electrical conductivity of flexible niobium carbide nanocomposite thin films

摘要

Flexible NbC nanocomposite thin films with carbon content ranging from 0 to99 at.% were deposited at room temperature on Si (100) and polystyrenesubstrates by non-reactive magnetron sputtering from pure Nb and C targetswithout applying bias voltage to the substrates. HRTEM images reveal that thefilms exhibit a nanocomposite structure consisting of NbC nanocrystals (2 to 15nm in size) embedded in an amorphous carbon matrix. By simply adjusting the Nbflux in the plasma, we can monitor the nanocrystal size and the percent offree-carbon phase in the films, which in turn allows for the tailoring of bothmechanical properties and electric conductivity of the films. It was found thatthe films composed of ~8-10% free-carbon exhibited a relative high hardness andelastic recovery, around 23 GPa and 85%, respectively, and an electricalconductivity of 2.2x106 S/m at 22C. This study indicates the potential of thisnon-reactive sputtering approach in depositing hard, elastic and electricallyconductive nanocomposite films at low temperatures, which is especially usefulfor preparation of films on temperature sensitive polymers or plasticsubstrates for nano- and micro- electronics applications.