Effects of sapphire nitridation and growth temperature on the epitaxial growth of hexagonal boron nitride on sapphire

TL;DR

This study investigates how sapphire nitridation and growth temperature affect the quality of epitaxial hexagonal boron nitride films grown via CVD on sapphire, identifying optimal conditions for high-quality film formation.

Contribution

It provides new insights into the effects of nitridation and growth temperatures on hBN film quality and establishes optimal parameters for epitaxial growth on sapphire substrates.

Findings

Optimal nitridation and growth temperatures improve film crystallinity.

Higher than optimal temperatures do not enhance epitaxial growth.

High-quality hBN films exhibit specific lattice constants and vibrational characteristics.

Abstract

This paper reports on the epitaxial growth of hexagonal boron nitride (hBN) films on sapphire substrates in a cold wall chemical vapor deposition (CVD) system where different sapphire nitridation and hBN growth temperatures were employed. A thin and amorphous nitridated layer was formed at a low temperature (850 C), which enabled subsequent epitaxial hBN growth at 1350 C. The influences of the sapphire nitridation temperature and the growth temperature on the film quality were analyzed by X-ray diffraction (XRD) measurements. Higher than optimum nitridation and growth temperatures improve the crystalline quality of the nitridated layer, but does not favor the epitaxial growth of hBN. hBN films grown at the optimum conditions exhibit the c-lattice constant of 6.66 {\AA} from the XRD {\theta}-2{\theta} scan, and the characteristic in plane stretching vibration at 1370.5/cm from Raman spectroscopy. X-ray photoelectron spectroscopy analysis confirmed the formation of stoichiometric hBN films with excellent uniformity.