A 3-μm-thick film of Magnéli Ti4O7 was successfully fabricated on the surface of Ti metal foil by a stepwise oxidation process involving annealing at 973 K in air followed by heating to 1173 K under a low oxygen partial pressure. Transmission electron microscopy and high-angle annular dark-field scanning transmission electron microscopy showed that the Magnéli Ti4O7 phase consisted of a period of four layers of equiaxial grains several hundreds of nanometers in size. The black Magnéli Ti4O7 thin film formed by our process absorbed light in the visible and near-infrared regions. Figure (a) Appearance and (b) corresponding XRD patterns of a sample before and after heating. (I) Ti metal foil before heating, and after heating to (II) 973 K 10.8 ks in air, (III) 1173 K with no resting time in air, and two-step heat treatment involving heating at 973 K 10.8 ks in air and subsequent heating to 1173 K with no resting time under (IV) PO2 = 1.0 × 10−5 atm, (V) PO2 = 1.0 × 10−10 atm, respectively. Display omitted