Orientation tendency of PLD carbon films as a function of substrate temperature: A NEXAFS study

摘要: Abstract Electronic properties of graphene nano-structures are highly anisotropic and correlated to their basal plane orientation. In this work, we tried study explain how deposition temperature can draw a definite growth direction. Carbon films have been deposited by Pulsed Laser Ablation (Nd:YAG, 2nd harmonic: λ=532 nm, hν=2.33 eV, τ=7 ns, ν=10 Hz, Φ ≈7 J/cm2), from pyrolytic graphite target on Si substrates. PLD depositions were performed in vacuum, at increasing substrate temperature, ranging room (RT) 900 °C. Near-edge X-ray absorption fine structure (NEXAFS), SEM Raman spectroscopy used characterise the films. Using linearly polarized Synchrotron radiation HOPG (Highly Oriented Pyrolytic Graphite) as reference system, investigated, ex situ, occurrence an average orientation distribution nano-sized clusters, grown high temperature. The results angle-dependent NEXAFS film °C provide evidence that sheets show tendency grow with planes oriented perpendicularly surface. At low is less structured. features ascribable graphitic character pronounced broadened; absence angle dependence measurements suggest C-structures randomly oriented. corresponding spectrum substantiates prevailing amorphous nature film.