Simonas Krotkus
AIXTRON SE, Herzogenrath, Germany _______________________________________
Integration of h-BN with other two-dimensional (2D) materials allows to retain a clean van der Waals interface which plays the key role in determining performance at a device level. Multilayer h-BN films are thus desired for a number of applications in opto- and microelectronics. However, wafer-scale synthesis of h-BN with precise thickness and controlled crystal quality is challenging due to poorly understood growth mechanism as well as lack of established standardized metrology procedures.
Here, we present progress on h-BN growth up to 8“ sapphire substrates and demonstrate its application as a gate dielectric for effective switching of graphene FETs and as an active media for resistive-switching devices. Spectroscopic ellipsometry procedure was developed to assess the synthesis of thin h-BN films on a wafer scale. Special emphasis was placed on a reliable evaluation of layer thickness, accounting for stress-induced changes in the optical properties of the epitaxial film on the foreign substrate and corroborating findings with GIXRD, XRR, Raman and AFM investigation. Key role of temperature in determining thin film uniformity was identified, which enabled us to achieve uniform h-BN deposition across the wafer (Fig. 1). Our results highlight the importance of the interface control to improve performance of 2D material based electronic devices and provide metrology protocol for thickness determination of thin 2D films.
Figure 1. Thickness mapping by ellipsometry of three different processes of h-BN on 8″ sapphire wafers produced by CVD using borazine precursor.
Email: s.krotkus@aixtron.com