Preparation of Multi-Layer Graphene Using Nitrogen-Doped Ultrananocrystalline Diamond as a Solid-State Carbon Source

The present investigation deals with the growth of multilayer graphene (MLG) using nitrogen-doped ultrananocrystalline diamond (N-UNCD) as a solid-state carbon source on nanopatterned sapphire substrates (NPSS). The nucleation-enhanced method of the NPSS has been used to grow continuous and smooth N-UNCD thin films. The MLG was obtained by depositing a 200-nm-thick Ni layer on N-UNCD/NPSS, followed by thermal processing at 700 °C in a low-pressure chemical vapor deposition system. After removing the residual Ni, the Raman spectrum reveals that the t-PA peaks at 1140 and 1480 cm⁻¹ of N-UNCD have disappeared, leaving only the D-band at 1350 cm⁻¹, G-band at 1580 cm⁻¹, and 2D band peak at 2700 cm⁻¹. The full width at half-maximum of the 2D-band peak is 76 cm⁻¹ ,indicating that an MLG can be prepared on a sapphire substrate. The temperature-dependent current–voltage (I–V) measurement demonstrated that MLG has a positive temperature coefficient (PTC) of resistance and is a promising electrode material for suppressing the thermal runaway of high-power electronic devices.