Palladium oxide (PdO) was deposited on platinum by reactive sputter deposition, and the PdO thin film grown on the Pt substrate had a flakelike morphology. The nanosized flake had a core-shell structure with a single Pd grain encapsulated by a crystalline PdO surface layer. The formation of the PdO capped nanoflakes was ascribed to a large interfacial stress due to a lattice mismatch between PdO and Pt. Field emission characteristics of the nanoflakes were studied and a field-enhancement factor of 791 was obtained.