Reactive scattering of Cl2 on GaAs (100): Cl2 and GaCl product distributions

Time-of-flight and angular distributions of GaCl produced from etching of GaAs (100) by molecular chlorine have been investigated in the range 400–550°C by pulsed, supersonic, molecular beam scattering. The angular distribution is well described by a cosine curve as expected for simple desorption. The TOF distributions of GaCl reveal that it is produced by two surface processes. The Cl2 distributions also show two components: (i) prompt production (accommodation and desorption of incident Cl2) and (ii) delayed chemical production. In all cases the delayed component is well described by a simple e−t/π expression. Chemical production of Cl2 seems strongly linked to the slower GaCl production and both pathways display the same temperature dependence. The time constants obey τ=τ0 exp (E/kT) with E = 110 ± 10 kJ mol−1 for both pathways.