The degradation of ferroelectric (FE) properties of atomic layer deposited Hf_0.5Zr_0.5O₂ films with increasing thickness was mitigated by inserting 1 nm-thick Al₂O₃ interlayer at middle position of the thickness of the FE film. The large P_r of 10 μC/cm², which is 11 times larger than that of single layer Hf_0.5Zr_0.5O₂ film with equivalent thickness, was achieved from the films as thick as 40 nm. The Al₂O₃ interlayer could interrupt the continual growth of Hf_0.5Zr_0.5O₂ films, and the resulting decrease of grain size prevented the formation of non-ferroelectric monoclinic phase. The Al₂O₃ interlayer also largely decreased the leakage current of the Hf_0.5Zr_0.5O₂ films.

For the utilization of graphene in various energy storage and conversion applications, it must be synthesized in bulk with reliable and controllable electrical properties. Although nitrogen-doped graphene shows a high doping efficiency, its electrical properties can be easily affected by oxygen and water impurities from the environment. We here report that boron-doped graphene nanoplatelets with desirable electrical properties can be prepared by the simultaneous reduction and boron-doping of graphene oxide (GO) at a high annealing temperature. B-doped graphene nanoplatelets prepared at 1000 °C show a maximum boron concentration of 6.04 ± 1.44 at %, which is the highest value among B-doped graphenes prepared using various methods. With well-mixed GO and g-B₂O₃as the dopant, highly uniform doping is achieved for potentially gram-scale production. In addition, as a proof-of-concept, highly B-doped graphene nanoplatelets were used as an electrode of an electrochemical double-layer capacitor (EDLC) and showed an excellent specific capacitance value of 448 F/g in an aqueous electrolyte without additional conductive additives. We believe that B-doped graphene nanoplatelets can also be used in other applications such as electrocatalyst and nano-electronics because of their reliable and controllable electrical properties regardless of the outer environment.