Acceleration of photocarrier relaxation in graphene results in the enhancement of its properties for graphene-based ultrafast optical devices. The acceleration can be achieved by utilizing the relaxation paths outside the graphene to avoid bottlenecks in the graphene for photocarrier relaxation. In this study, we investigate photocarrier relaxation in epitaxial and transferred monolayer graphene on SiC with a buffer layer at room temperature by means of time-resolved photoluminescence spectroscopy. The photoluminescence decay at 0.7 eV in the epitaxial monolayer graphene is faster than that in the transferred monolayer graphene. On the basis of the three-temperature model calculation, it is found that the carrier–phonon interaction with phonons of the buffer layer for the epitaxial monolayer graphene is 3 times stronger than that for the transferred monolayer graphene. This study demonstrates that ultrafast photocarrier relaxation can be achieved in graphene by epitaxial growth.

Li + desolvation process has been regarded as the rate-limiting process in Li + insertion reaction with graphite anode in lithium-ion batteries. In contrast, Li + desolvation process is absent in solid-state batteries. We fabricated thin-film all-solid-state cells by depositing lithium phosphorus oxynitride glass (LiPON) electrolyte onto a multilayer-graphene (MGr) film by RF magnetron sputtering and measured the charge/discharge performance of the cells. It was found that the charge transfer resistance at the LiPON/MGr interface was significantly small, although the LiPON/MGr interface was supposed to have inorganic solid electrolyte interphase resulting from the LiPON reduction decomposition. Consequently, the dominant factor for the overall overpotential was the ohmic loss for LiPON, and hence the capacity retention was still maintained at 60% even at nearly 900C when the LiPON film thickness was 4 μm.

Graphene on SiC (000-1) tends to grow in multiple layers and does not have a single orientation relation with the SiC substrate. It has been considered impossible to control the rotation angle of multilayer graphene on SiC (000-1). In this study, we grew graphene on off-axis SiC substrates with various off angles from 0° to 8° and investigated their in-plane rotation and electronic structures systematically. As the off angle toward the [11-20]SiC direction increased, graphene rotated by 30° with respect to SiC became less dominant and instead, graphene rotated by 30 ± 2.5° appeared. We also found that the uniformity of the graphene rotation angle was relatively high on SiC substrates with a small off angle toward the [1-100]SiC direction. Our results suggest that the step-terrace structure defined by the substrate off-direction and angle plays an important role in the controllability of the rotation angle of graphene.

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