Polycrystalline and high purity SnO₂ films by plasma-enhanced atomic layer deposition using H₂O plasma at very low temperatures of 60–90 °C

High-quality SnO₂ films with excellent crystallinities, purities, and high densities grown at low deposition temperatures (<100 °C) are essential owing to their applications in flexible electronics and energy devices. In this work, we successfully demonstrated plasma-enhanced atomic layer deposition (PEALD) of SnO₂ films at very low deposition temperatures of 60–90 °C using dimethylamino-2-methyl-2-propoxy-tin(II) (Sn(dmamp)₂) and H₂O plasma as the Sn precursor and reactant, respectively. These films showed a high growth per cycle of 0.24–0.30 nm/cycle owing to the excellent reactivity between Sn(dmamp)₂ and H₂O plasma. These films had significantly high densities of 6.20–6.68 g·cm⁻³, which are noticeably superior when compared to those of the previously reported SnO₂ films fabricated by ALD using different precursor/reactant combinations. The SnO₂ films showed negligible impurity concentrations, irrespective of the deposition temperature. The polycrystalline structure of the SnO₂ films was confirmed by X-ray diffraction and transmission electron microscopy measurements. These films, deposited at low temperatures of 60–90 °C, exhibited excellent electrical properties, i.e., high carrier concentrations of 3 × 10¹⁶−3 × 10¹⁸/cm³ and low resistivities of 4.20–57.2 Ω cm.