Characterization of fullerene-like CNx thin films deposited by pulsed-laser ablation of graphite in nitrogen

Abstract

Fullerene‐like CNx thin films were synthesized by Pulsed‐Laser Ablation (PLA) of pyrolythic graphite (99.99%) target in nitrogen using a (500 mJ, 7 ns, 1064 nm) Nd:YAG‐pulsed laser. The films were deposited onto silicon substrates at 300 °C and nitrogen pressures within the 5–100 mTorr range. The composition and structure of these films were analyzed by means of Reflection Absorption Infrared Spectroscopy (RAIRS), XPS, and Raman spectroscopy and the morphology of the film surfaces by AFM. The RAIRS analysis of films deposited at different pressures shows the presence of the 2229 and 2273 cm–1 stretching peaks associated to CN triple bonds (C≡N) of nitriles and isocyanides. On the other hand, the XPS study of the N 1s bonding energy region provided typical spectra of the CNx materials. The spectra present the energy peaks at 400.8 (P2) and 398.4 eV (P3), which are usually assigned to nitrogen that is bonded to sp2 and sp3‐coordinated C atoms, respectively. For a fullerene‐like structure with developed basal planes, nitrogen is mostly bonded in a sp2‐rich environment. In our conditions, in films deposited at 5 mTorr the P2/P3 ratio is 1.41 indicating a fullerene‐like structure. Finally, the Raman analysis of films produced at different pressures, shows the characteristic D and G peaks at 1360–1370 cm–1 and 1580–1590 cm–1 related to the bond length in sp3 or sp2‐coordinated carbon respectively. The study demonstrated that laser ablation technique, by using an Nd:YAG‐pulsed laser, is a viable technique for the growth of fullerene‐like CNx films. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Plasma characterization of pulsed-laser ablation process used for fullerene-like CNx thin film deposition

“…In fact, films grown at 5 mTorr presented the highest N content (23%) and P 2 /P 3 ratio (1.41), for N 1s nitrogen bonding and the highest Raman I(D)/I(G) ratio (2.45), related to the lowest G-peak position (1548.1 cm −1 ). These results indicate highest fullerene likeness under our experimental conditions [12]. …”

“…This result can be correlated to the N/C ratio of deposited CNx films, calculated using the ratio between the N 1s and C 1s peaks obtained through X-ray Photoemission Spectroscopy (XPS). We found that nitrogen content decreased from 23% to 18%, as pressure was increased from 5 to 30 mTorr [12]. In order to determine formation mechanisms, we have estimated the vibrational temperature of CN molecules using a relative emission intensity method.…”

Effect of Nitrogen Concentration on Capacitance, Density of States, Electronic Conductivity, and Morphology of N-Doped Carbon Nanotube Electrodes

“…High-resolution XPS analysis shows three distinct peaks at 398.6, 400.9, and 404.9 eV (Supporting Information). The peak at 398.6 eV is commonly attributed to pyridinic-type nitrogen, ,– and the peak at 400.9 eV is attributed to a convolution of both pyrrolic/pyridonic and quaternary functionalities, the former at 400 eV and the latter at 401 eV. ,,– The assignment of the peak at 404.9 eV is unclear and could be attributed to chemisorbed N-oxides, ,, pyridinic oxides, , molecular N 2 , , or shakeup satellites. , This peak cannot be assigned to one single functionality and is instead possibly a convolution of various possible coordinations. Heat treatment experiments were undertaken to determine the effect of removable surface N-oxides on the total nitrogen content.…”

Surface smoothing of sputter deposited amorphous CNx films by silicon addition

“…For the film S1, the sp 2 peak at 284.6 eV in C 1s spectrum is close to that of nitrogen-free amorphous carbon film (284.5 eV) deposited under similar conditions, but the sp 3 peak at 285.8 eV is higher than that of carbon film (285.3 eV), for the sp 3 peak of b-C 3 N 4 is at 287.6 eV [17]. Correspondingly, in the N 1s spectrum, the peak at 398.6 eV is ascribed to N-C bond and that at 400.4 eV is to N@C bond [18].…”