Room-Temperature Atomic Layer Deposition of Elemental Antimony

Atomic layer deposition (ALD) of elemental antimony was achieved on hydrogen-terminated silicon (H–Si) and SiO2/Si substrates using Sb­(SiMe3)3 and SbCl3 in the temperature range 23–65 °C. The mirrorlike films were confirmed to be composed of crystalline antimony by XPS (for the film deposited at 35 °C) and XRD, with low impurity levels and strong preferential orientation of crystal growth relative to the substrate surface. To the best of our knowledge, this is the first example of room-temperature thermal ALD (with demonstrated self-limiting growth) of a pure element. Film growth at 35 °C exhibited a substrate-enhanced mechanism, characterized by faster film growth for the first ∼125 ALD cycles, where substantial deposition occurs on the original substrate surface (GPC = 1.3 Å/cycle on SiO2/Si and 1.0 Å/cycle on H–Si) and slower film growth (GPC = 0.40 Å/cycle on SiO2/Si and 0.27 Å/cycle on H–Si) after ∼125 cycles, once much of the initial substrate surface has been covered. Films deposited using 500–2000 ALD cycles were shown to be continuous by SEM. The use of less than 250 cycles afforded discontinuous films. However, in this initial growth phase, when the deposition occurs primarily on the original substrate surface, in situ surface pretreatment by Sb­(SiMe3)3 or SbCl3 (50 × 0.4 or 0.8 s pulses) followed by the use of longer precursor pulses (0.4 or 0.8 s) during the first 50 ALD cycles resulted in improved nucleation. For example, on H–Si, a continuous 6.7 nm thick film was produced after initial pretreatment with 50 × 0.8 s pulses of SbCl3, followed by 50 ALD cycles using 0.8 s pulses. The use of longer pulses in the first 50 ALD cycles following surface pretreatment is likely required to achieve complete reactivity with an increased density of reactive surface sites.