Boron-induced amorphization in In2O3 enabling flexible transparent conductive films

We investigated the effects of boron concentration and post-deposition annealing temperature on the electrical properties of indium boron oxide (IBO), demonstrating a high-performance transparent conducting oxide film that rivals indium tin oxide (ITO), even when deposited at room temperature without any post-deposition annealing. Optimal performance was obtained at a boron content of 2.5 at.%, yielding a resistivity of 3.6 × 10 −4 Ω cm, Hall mobility of 47.2 cm 2 V −1 s −1 , and carrier density of 3.6 × 10 20 cm −3 . Although the carrier concentration was comparable to that of non-doped In 2 O 3 , the mobility was notably enhanced. This improvement is attributed to the fact that boron, having the same valence as indium, does not introduce excess carriers, while its smaller ionic radius enhances the overlap of In 5 s orbitals, facilitating more efficient carrier transport. Because IBO is compatible with room-temperature processing, films were also deposited on poly(ethylene terephthalate) substrates to evaluate their potential as flexible transparent conductors in comparison with ITO. The increase in resistance under mechanical bending was less than one-third that of ITO, suggesting superior mechanical durability for IBO. This difference may originate from the highly amorphous nature of the IBO film. Furthermore, nanoindentation measurements revealed Young's moduli of 70.0 and 130.8 GPa for IBO and ITO, respectively, indicating that amorphous IBO possesses high mechanical flexibility, consistent with the bending resistance test results. • Indium boron oxide (IBO) films were fabricated by room-temperature sputtering. • IBO exhibits ITO-comparable resistivity of 3.6 × 10 −4 Ω cm without any annealing. • Boron incorporation induces high amorphization in the In 2 O 3 network. • Boron incorporation enables controlled oxygen-vacancy formation in amorphous IBO. • IBO on PET demonstrates superior mechanical flexibility for TCO applications.