title: Role of limited hydrogen and flow interval on the growth of single crystal to continuous graphene by low-pressure chemical vapor deposition.
abstract: A method for defect-free large crystallite graphene growth remains unknown despite much research effort. In this work, we discuss the role of flow duration of H2gas for the production of graphene as per requirement and production at a minimum flow rate considering the safety issue of hydrogen utilization. The copper substrate used for growth was treated for different time intervals (0 to 35 min) in H2flow prior to growth. Structural and chemical changes occurring in the copper substrate surface were probed by grazing incidence x-ray diffraction and x-ray photoelectron spectroscopy. The results were correlated with the Raman spectroscopy data, which can quantify the quality of graphene. With increasing H2flow interval, secondary nucleation sites were observed and growth favored few-layer graphene structures. The surface-adsorbed oxygen molecules and its conversion to an OH terminated surface with increasing hydrogen flow interval was found to be a key factor in enhancing nucleation density. The Stranski-Krastanov type of nucleation was observed for samples grown with different time intervals of H2treatment, except 5 min of H2flow prior to growth for which the Volmer-Weber type of growth favored monolayer graphene crystallite growth.
authors.affiliation: Advanced Carbon Products section, Advanced Materials and Devices Division, CSIR-National Physical Laboratory, New Delhi-110012, India. Academy of Scientific & Innovative Research (AcSIR), CSIR-NPL, New Delhi-110012, India.
authors.forename: Munu
authors.initials: M
authors.lastname: Borah
authors.forename: Abhishek K
authors.initials: AK
authors.lastname: Pathak
authors.forename: Dilip K
authors.initials: DK
authors.lastname: Singh
authors.forename: Prabir
authors.initials: P
authors.lastname: Pal
authors.forename: Sanjay R
authors.initials: SR
authors.lastname: Dhakate