Surface reactions of TiCl4 and Al(CH3)3 on GaAs(100) during the first half-cycle of atomic layer deposition

► Al(CH3)3 and TiCl4 pulses mimic the first half-cycle of atomic layer deposition. ► Both precursors removed the oxide left on GaAs(100) after aqueous HF treatment. ► Al(CH3)3 deposited an Al2O3 layer. ► TiCl4 deposited a small TiO2 coverage below 135 °C, but no TiO2 was deposited from 170-230 °C. ► The GaAs surface was passivated by Cl atoms bound to an elemental As overlayer.