Affiliation:
1. Nanophotonics Technology Center (NTC), Universitat Politècnica de València, 46022 Valencia, Spain
2. Institute of Optoelectronic Systems and Microtechnology (ISOM), Universidad Politécnica de Madrid, 28040 Madrid, Spain
Abstract
In this work, we study the influence of the different surface terminations of c-plane sapphire substrates on the synthesis of graphene via plasma-enhanced chemical vapor deposition. The different terminations of the sapphire surface are controlled by a plasma process. A design of experiments procedure was carried out to evaluate the major effects governing the plasma process of four different parameters: i.e., discharge power, time, pressure and gas employed. In the characterization of the substrate, two sapphire surface terminations were identified and characterized by means of contact angle measurements, being a hydrophilic (hydrophobic) surface and the fingerprint of an Al- (OH-) terminated surface, respectively. The defects within the synthesized graphene were analyzed by Raman spectroscopy. Notably, we found that the ID/IG ratio decreases for graphene grown on OH-terminated surfaces. Furthermore, two different regimes related to the nature of graphene defects were identified and, depending on the sapphire terminated surface, are bound either to vacancy or boundary-like defects. Finally, studying the density of defects and the crystallite area, as well as their relationship with the sapphire surface termination, paves the way for increasing the crystallinity of the synthesized graphene.
Funder
Generalitat Valenciana
AGENCIA ESTATAL DE INVESTIGACIÓN of Ministerio de Ciencia e Innovacion
European Regional Development Fund
European Union NextGenerationEU
Subject
General Materials Science,General Chemical Engineering