Focus movement distance per pulse dependence of electrical conductivity and diameter of diamond internal modification induced by picosecond laser

Abstract

Internal and local modifications via ultrashort pulsed laser illumination to diamond are promising for manufacturing diamond electronic devices. The relationship between the diameter/electrical conductivity of modified regions and the laser fluence distribution was investigated. Picosecond laser illumination without scanning the laser focus fabricated short modified regions in diamond. As a result, the calculated laser fluence distribution matches the distribution of the modified regions. Wire-shaped modified regions were fabricated via laser illumination with scanning of the laser focus, and the corresponding diameter and electrical conductivity were investigated by controlling the laser focus movement distance per pulse (Vf). The modified regions fabricated with varying Vf were divided into three categories depending on the trend of the relationship between the diameter and electrical conductivity. The diameters of the modified regions were constant at the maximum values when Vf was sufficiently small, decreased with increasing Vf, and reached a minimum when Vf was sufficiently large. The modified regions became more electrically conductive with increasing Vf, even when the deposited energy per unit length decreased. Moreover, the electrical conductivity decreased significantly when the diameter became constant at the minimum value. Finally, the relationship between the diameter/electrical conductivity of the modified regions and the laser fluence distribution was elucidated.