Enhancing single-ion detection efficiency by applying substrate bias voltage for deterministic single-ion doping

A single-ion implantation technique that enables us to implant dopant ions one-by-one into semiconductors until the desired number is reached has been developed. The key to controlling the ion number is to detect secondary electrons (SEs) emitted from a target upon ion incidence. The SE detection efficiency currently achieved is 90% due to the low probability of SE emission, but has been enhanced to almost 100% by increasing the number of SEs by controlling the substrate bias voltage. This improvement has accelerated the prospects for realizing single-dopant devices, which are necessary for the ultimate control of the ion number.