Enhanced Crystallinity of h‐BN Films Induced by Substrate Bias During Magnetron Sputtering

Abstract

The synthesis of uniform, highly crystalline thin films of hexagonal boron nitride (h‐BN) is an important step for its applications in multilayered devices with other emerging 2D materials. We report on the growth of high purity h‐BN by reactive magnetron sputtering from a pure B target in an Ar/N2 plasma. Enhanced h‐BN crystallinity on Ni substrates was achieved using a negative DC substrate bias during deposition, which served to increase the energy of incident ions, causing higher adatom mobility and re‐sputtering of weakly bound species on the growth surface. Growth rates between 0.002 to 1.1 Å s−1 were observed as the power was varied from 10 to 200 W and the growth temperature was either room temperature or 850 °C. BN films grown on a r‐sapphire substrate or a silicon (100) wafer with native oxide were smooth but amorphous under all conditions. Crystalline growth was observed on unbiased Ni foil substrates heated to 850 °C provided the growth rate was below 0.01 Å s−1, but the films were a non‐uniform mixture of h‐BN crystals and a disordered phase. Using a −50 V substrate bias, a high degree of h‐BN crystallinity and film homogeneity over large areas on the Ni substrate was achieved.