Spectroscopic Analysis of a Pulsed-Laser Deposition System for Fullerene-like Cn x Film Production

Abstract

Plasma produced by a (1064 nm) Nd:YAG laser focused onto a graphite target at different nitrogen pressures in the range of 1-90 mTorr, was studied spectroscopically. In the spectral range of 350-600 nm, emission lines of CI neutral carbon (501.12, and 505.21 nm), NI neutral nitrogen (493.5 nm), CII (426.72, 463.7, 515.11 nm), and CIII ions (465.02 and 569.59 nm), and NII ions (501.06, and 500.73 nm), were dominating. Bands of C 2 Swan (d 3 g → a 3 u , ν = 2, 1, 0, −1), and CN Violet (B 2 + → X 2 + , ν = 1, 0, −1) systems, and ionic emissions from the First Negative system N2 + (band head at 391.44 nm), were faintly observed under our specific experimental conditions. From the band intensities, vibrational temperature for CN and C 2 was calculated to be 1.25 and 0.31 eV at 90 mTorr, respectively. The electron density and temperature, measured by Stark broadening, assuming a local thermodynamic equilibrium (LTE), were found to be 2.1 × 10 17 cm −3 and 0.33 eV at 1mTorr, respectively. The validity of the LTE is discussed according to the results discussed. Pressure dependence shows a decrease in the vibrational temperature when nitrogen pressure increases, while the electron density and temperature increase.

Optical spectroscopy of emission from CN plasma formed by laser ablation

“…The estimation of vibrational temperature of the carbon plasma was done according to the Boltzmann distribution: where λ is the wavelength corresponding to the emission, h Planck's constant, c the velocity of light, C a constant, G(ν ) the term value corresponding to the vibrational level in the upper electronic state and T vib the vibrational temperature. Under the assumption that the carbon plasma are in local thermodynamic equilibrium, the vibrational temperature for bands C 2 Swan ( ν = 1, in the 467-474 nm range) and CN violet ( ν = 2, in the 450-460 nm range) systems, respectively, were calculated from the sums of the band-head strengths measured in various ν or ν progressions against the vibrational term values G(ν ) [10]. The spectroscopy constants G(ν ) used for calculations were obtained from the handbook [11].…”