The dependence of barrier heights of a-C: Fe/n-Si heterojunctions on film-depositing temperatures

Iron doped amorphous carbon (a-C: Fe) films on n-Si substrates were fabricated by pulse laser deposition technique. Barrier heights of the heterojunctions, measured in the electrical methods, were found to decrease gently below 300 degrees C and then increase anomalously thereafter. An interface energy band model was proposed to interpret the band structure of the heterojunctions as well as to calculate bandgaps of the a-C: Fe films. The abnormal increase in the barrier heights above 300 degrees C was attributed to the narrowing of pi and pi* bands due to the increased ordering degree of the sp(2) clusters in a-C films, which was verified in Raman spectra and electron energy loss spectroscopy. (C) 2011 American Institute of Physics. [doi :10.1063/1.3587157]status: publishe