The combined effect of laser fluence and target deterioration in determining the chemical composition of pulsed laser deposited boron carbide films

A series of boron carbide films of 180±30 nm thickness has been deposited by KrF excimer laser ablation of a sintered B4C target in high vacuum. Rutherford backscattering spectroscopy revealed that the chemical composition of the films grown on Si substrates, at room temperature, at laser fluences tuned between 2 and 14.3 J cm−2 varied depending not only on the actual laser fluence but also on the past record of the B4C target. Parallel SEM mapping of both film and target surfaces pointed to a correlation between changes in film composition, droplet density and target surface deterioration. This correlation is discussed in detail.