Effects of iron on the infrared photoresponse of carbon/n-Si junctions prepared by plasma decomposition of propylene and ferrocene

Abstract

Iron containing carbon films were deposited on n‐Si substrate at 300 °C by dc plasma decomposition of propylene gas and ferrocene vapor. The films were investigated for the effect of iron on the photoresponse of a light emitting diode at 940 nm wavelength. The photocurrent was shown to vary with iron content and the variation in the photovoltage with iron content showed the same trend as that of photocurrent against iron content. The dependence of photocurrent on the light chopping frequency revealed that the attenuation of photocurrent with the frequency was small compared with the junction without iron. The states of iron in the carbon matrix were studied by x‐ray photoelectron spectroscopy. The peak position shifted to higher binding energies with higher iron content. Peak analysis revealed two separate elemental peaks at 709 and 711 eV. The intensity of the 709 eV peak due to the iron in the low valence state showed a correlation with the magnitude of the photocurrent. From those observations the action of the iron in the low valence state was inferred to change the electronic state at the carbon film/n‐Si junction to promote the photocarrier generation and ultimately enhance the photoresponse.