Structural and electrical properties of amorphous carbon-sulfur composite films

In this paper, we discu ss the synthesis of carbon -sulfur composite (a-C:S) films by vapour phase pyrolysis of maleic anhydride and sulfur. Structural changes in the system are analysed by scanning electron microscopy and powder X-ray diffraction. Microhardness test depicts an in crease in the value of hardness with an increase in sulfur concentration. Electrical conductivity of composite samples varies with sulfur co n- centration. Magnetoresistance (MR) measurements show a drastic increase in the value of MR for the samples prepared at < 900°C. Thermal stability of these samples is analysed by thermogravime tric analysis, which depends on the host structure and the amount of intercalated species. tems and is closely related to temperature dependence of conductivity. The effect of magnetic field ( B) on the weak localization of electrons i s similar to that of inela stic scat- tering. It suppresses the phase coherence between the par - tial waves associated with an electron and this reduces the localization, causing the resistance to d ecrease with magnetic field (negative magnetoresistance). The contri- bution to magnetoresist ance from electron-electron inter- action is positive and is predominantly due to Zeeman splitting of the spin -up and spin-down bands. The magne- toresistance is interpreted to be due to distortion of ele c- tron orbit at low fields and due to shrinkage of electron wave function at high fields. Magnetoresi stance shows a B 2 dependence at low fields and is temperature depen - dent, whereas at high fields it is independent of temper a- ture and exhibits a B