RF bias-enhanced heteroepitaxial nucleation of (100) diamond on (100) Ir/a-sapphire

Abstract

We report radio-frequency (RF) bias-enhanced nucleation (RF-BEN) of heteroepitaxial (100) diamond on (100) Iridium (Ir)/a-sapphire by 2.45 GHz microwave plasma chemical vapor deposition (MPCVD) in 8% CH4 diluted by hydrogen. The electrically insulating sapphire substrate acts as a capacitor of low impedance between the iridium film and the substrate holder and allows RF biasing current to flow through it. Because of a higher electron mobility than positive ions, a time-average negative DC bias voltage is induced on iridium with respect to the plasma leading to the nucleation of heteroepitaxial diamonds. Subsequent diamond growth in 0.5% CH4 diluted by hydrogen produces (100) diamond films. X-ray diffraction (XRD) at sample tilt = 88° confirms the diamond (400) reflection with a rocking-curve full width half maximum of  ≈ 1.27°. XRD {111} pole-figure measurements confirm reduced mosaic spread and the absence of twins. The RF-BEN technique is promising for producing heterogeneous diamond wafers on iridium-coated large-area electrical insulating substrates.