Graphene-Assisted Epitaxy of Group IV Semiconductor Nanostructures and Thin Films

Abstract

The growth of single crystalline group IV materials on amorphous substrates is useful in applications ranging from electronics to renewable energy. Graphene-assisted (or van der Waals) epitaxy is a promising route to achieve such films but has largely been limited to III-V and II-VI materials. In this work, we use graphene as a template for the low temperature epitaxy of group IV nanostructures and thin films. We investigate the effect of growth parameters and type of nucleation site (e.g., metal catalysts vs. graphene defects) on the crystal growth. We observe that metal catalysts enable in-plane group IV nanowire growth via the vapor-solid-solid mechanism at temperatures as low as 150 °C. The observation that neighboring nanowires are oriented 60º with respect to each other implies that the graphene crystal plays a critical role in the growth process. Graphene surface defects, induced by hydrogen radical exposure, can also be used to initiate crystal growth at elevated temperature. We leverage the differences in group IV atom sticking probability on graphene and amorphous surfaces to achieve selective epitaxy on graphene-on-oxide patterns. Transient studies as a function of the graphene pattern dimensions reveal a competition between crystal expansion and ripening. Our studies extend graphene-assisted epitaxy to a new, technologically-relevant materials system and provide fundamental insight into the underlying physicochemistry.