Visualization of CVD-grown graphene on Cu film using area-selective ALD for quality management

The present study investigates the atomic layer deposition (ALD) of an Al₂O₃ film on graphene atop copper with water vapor (H₂O), oxygen plasma (O₂ plasma) and ozone (O₃) serving as oxidants. With water vapor as an oxidant, surface-sensitive deposition results in significant differences in growth on single layer graphene (SLG) and multilayer graphene (MLG). Al₂O₃ completely covers areas of SLG, while virtually no Al₂O₃ is deposited on areas of MLG. The MLG areas are removed by O₂ plasma, and exposed copper areas are oxidized. Information about MLG, including the location, size, and density, can be determined by employing optical microscopy. Scanning electron microscopy (SEM), Raman spectroscopy, transmission electron microscopy (TEM), and X-ray photoelectron spectroscopy (XPS) are used to confirm the validity of the surface-selective deposition of Al₂O₃ on graphene grown on copper. We developed a process to distinguish SLG and MLG on copper. The characterization results were fed back to the synthesis conditions, and we confirmed that high-quality SLG can be grown on copper almost devoid of MLG. This characterization technique is suitable for large-area graphene (up to meter scale graphene), and can be utilized as feedback for growth and process conditions to ensure high-quality graphene.