Pulsed-dosing controls self-assembly: 1-Bromopentane on Si(1 1 1)-7 × 7

► High-pressure dosing with short pulses of gas has been combined with UHV STM. ► 1-Bromopentane physisorbed on Si(1 1 1), (a) one-per-corner-hole (OPCH), (b) circles. ► Localized reaction formed chemisorbed bromine-atoms, OPCH or circles.