In-situ control of on-chip angstrom gaps, atomic switches, and molecular junctions by light irradiation

•Adjustable nanogaps with sub-angstrom precision were fabricated by laser irradiation..•Atomic-level metal contacts switches were realized and the direction of the switching can be selectively controlled..•The nanogap’s size can be continuously changed, providing a technique to measure the conductance of single molecules.•The small spatial focus size of the laser beam makes it feasible to realize addressable on chip molecular junction arrays.