UV Raman studies on carbon nitride structures

Visible (514 nm) and deep UV (257 nm) Raman spectra of monoclinic tetracyanoethylene (tcne) are recorded at ambient conditions and also after laser heating at ambient pressure and at 40 GPa. Tetracyanoethylene (C2(CN)4) is a convenient precursor to synthesize hard C3N4 materials. At low incident laser powers the UV Raman spectra of virgin tcne resemble visible Raman spectra, and at higher powers there appear new, broad modes that increase in intensity as a function of laser power. When tcne is laser-heated at ambient pressure, there are two broad UV Raman peaks about 1,405 cm–1 and 1,604 cm–1 whereas visible laser Raman excitation results in too high a fluorescent background to show up any Raman modes. Raman spectrum of tcne laser heated at 40 GPa show broad peaks indicative of multiphase formation. The spectrum has additional modes at lower frequencies, and comparison with calculated Raman frequencies points to possible formation of a-C3N4.