Xuqiang Zhang

Synthesis of crystalline C3N4 by MPCVD

In this study, carbon nitride thin films are synthesized on Si and Pt substrates by microwave plasma chemical vapor deposition (MPCVD). The major part of the films is composed of alpha-C3N4 and beta-C3N4. XPS and FT-IR spectra strongly support the existence of C-N covalent bonds in C3N4. Raman spectra also support the existence of beta-C3N4. The carbon nitride films on Pt substrates have a high bulk modulus of 349 GPa

Crystalline β-C3N4 synthesized by MPCVD

Carbon nitride films were grown on Si and Pt substrates by microwave plasma chemical vapor deposition (MPCVD) method. Scanning electron microscope (SEM) observations show that the films deposited on Si substrates consisted of densely populated hexagonal crystalline rods. Energy dispersive X-ray (EDX) analyses show that N/C ratios of the rods were in the range of 1.0 to 2.0 depending on deposition condition. X-ray diffraction experiments show that the films consisted of crystalline phase β-C3N4. Comparison with films grown on Pt substrate show that the main X-ray diffraction peaks of β-C3N4 are existed in films deposited on both substrate. XPS study showed that carbon and nitride atoms are covalent bounded to each other. IR results show that the film is predominantly C-N bonded. Raman measurement showed characteristic peaks of β-C3N4 in the low wave number region. Temperature dependent growth experiments show that the amount of Si3N4 in the films grown on Si substrates can be significantly reduced to negligible amount by controlling the substrate temperature.

On the structure and composition of crystalline carbon nitride films synthesized by microwave plasma chemical vapor deposition

Crystalline carbon nitride thin films were prepared on Si (100) substrates by a microwave plasma chemical vapor deposition (MPCVD) method, using CH4:N2 as precursor gases. The surface morphologies observed by scanning electron microscopy (SEM) of the carbon nitride films deposited on Si substrate at 830°C were consisted of hexagonal crystalline rods. The effect of substrate temperature on the formation of carbon nitrides was investigated. X-ray photoelectron spectroscopy (XPS) analysis indicated that the maximum value of the N:C atomic ratio in the films deposited at a substrate temperature of 830°C was 1.20, which is close to the stoichiometric value of C3N4. The X-ray diffraction (XRD) pattern of the film deposited at 830°C indicates no amorphous phase in the film, which is composed of b- and a-C3N4 phase containing an unidentified CN phase. Fourier transform infrared (FTIR) and Raman spectroscopy support the existence of CN covalent bond.

Characterization of carbon nitride thin films deposited by microwave plasma chemical vapor deposition

Abstract The carbon nitride films have been prepared on Si substrates using microwave plasma chemical vapor deposition (MPCVD) technique. The experimental X-ray diffraction (XRD) spectra of films deposited on Si substrates appear to contain all of the strong peaks of α-C 3 N 4 and β-C 3 N 4 , but there is considerable peak overlap, therefore the existence of these phases cannot, for certain, be claimed from this data. However, the N/C atomic ratio is close to the stoichiometric value 1.33. X-Ray photoelectron spectroscopy (XPS) analysis indicated that the binding energies of C 1s and N 1s are 286.43 and 399.08 eV, respectively. The shifts are attributed to the polarization of the CN bond. Both observed Raman and Fourier transform infrared (FT-IR) spectra were compared with the theoretical calculations. The results support the existence of a CN covalent bond in the films.

Crystalline β-C3N4 films deposited on metallic substrates by microwave plasma chemical vapor deposition

Abstract Carbon nitride films were grown on poly-crystalline metallic substrates, such as Ta, Mo and Pt, by the microwave plasma chemical vapor deposition (MPCVD) method. The deposited films were examined by scanning electron microscope (SEM), energy dispersive X-ray (EDX) and XRD. SEM observations show that the films deposited on Pt substrates consisted of small crystalline grains, while the morphology of the films on the other substrates were irregular. X-ray diffraction experiments show that metallic carbide or nitride are formed in films deposited on Ta and Mo but not on Pt substrates. However, characteristic peaks of crystalline β-C 3 N 4 and α-C 3 N 4 can be seen in films deposited on all three substrates. EDX analysis show that N/C ratios can be as high as 4/3 for carbon nitride films deposited on Pt under optimized growth conditions.