Determining the Oblique Angle of Vertical Graphene Arrays Using Helicity-Resolved Raman Spectroscopy

The microscopic structure of a macroscopic material assembled from a nanoscale determines its performance in practical functional applications. The rapid, effective, and in situ characterization of the microscopic structure, particularly the spatial orientation of nanomaterials in the assembly, is of urgent need but remains challenging. Herein, we report a Raman spectroscopic technique to characterize the oblique angle of vertical graphene (VG) arrays that are promising for thermal management applications. Raman spectroscopy is a powerful tool not only for the characterization of the composition and lattice structure of materials but also for the determination of structural orientation owing to the polarization-dependent Raman intensities. Using helicity-resolved Raman spectroscopy (HRRS), we show that the oblique angle of VG can be characterized quantitatively with an error of less than 5 degrees. The technique is advantageous over the conventional linearly polarized Raman spectroscopy in simplicity and reliability, but if in combination, can be a versatile approach to characterize the spatial orientation of materials in more complex systems.