Ultrasmooth, high electron mobility amorphous In-Zn-O films grown by atomic layer deposition

Ultrasmooth and highly conductive amorphous In-Zn-O (a-IZO) films are grown by atomic layer deposition (ALD). This opens a new pathway to highly transparent and conductive oxides with an extreme conformality. In this process, a-IZO films of various compositions are deposited by alternate stacking of ZnO and In₂O₃ atomic-layers at a temperature of 200 C. The IZO films have an amorphous phase over a wide composition range, 43.2-91.5 at %, of In cation ratio. The In-rich a-IZO film (83.2 at % In) exhibits a very low resistivity of 3.9 × 10^-4 Ω cm and extremely high electron mobility in excess of 50 cm² V^-1 s^-1, one of the highest among the reported ALD-grown transparent conducting oxides. Moreover, it exhibits an ultrasmooth surface (∼0.2 nm in root-mean-square roughness), and can be conformally coated onto nanotrench structures (inlet size: 25 nm) with excellent step coverage of 96%.