Growth dynamics in patterned TiO2 deposited by direct atomic layer processing (DALP) in ambient conditions

Area-selective atomic layer deposition (AS-ALD) is a nanofabrication method delivering atomic layers of patterned films with exceptional precision, but it still relies on vacuum hardware and surface chemistry pretreatments that limit flexibility and throughput. Direct atomic layer processing (DALP) is an ALD-based technique that allows the deposition of single atomic layers in an additive fashion through a micronozzle, with no requirements for vacuum. In this work, we demonstrate DALP deposition of line-patterned TiO2 2–18 nm thin films deposited at temperatures from 80 to 250 °C. We show that the films were locally deposited, with no overspray, with a surface uniformity of 0.03 ± 0.01 nm, and a roughness in the range of 0.23 ± 0.09 nm (80 °C) to 0.57 ± 0.05 nm (250 °C). Moreover, we find that the films undergo a transient growth regime at a low number of cycles, with low nucleation delay (0–11 cycles) and a rapid growth relaxation with decay time-constants τ from 18 to 32 cycles, depending on the temperature. A linear growth regime is achieved after ≈3τ, with values from 0.033 ± 0.001 (250 °C) to 0.052 ± 0.003 (80 °C) nm/cycle. These results show that DALP produces ALD quality TiO2 at ambient pressure and line speeds up to 200 mm/s, providing a high-throughput alternative to inhibitor-based AS-ALD.