Growth and ac-Properties of Lanthanum-Manganese Oxide Films on Si Substrates

The prepared (La-Mn) oxide thin films on glass and p-Si substrates have been characterised by UV-VIS absorption spectroscopy, energy dispersion X-ray fluorescence (EDXRF) and X-ray diffraction (XRD). The XRF spectrum was used to determine the weight fraction ratio of Mn to La in the prepared samples. The optical studies determine the optical bandgaps of the prepared samples and its variation with crystallisation. XRD shows that La oxide and Mn oxide do not prevent each other to crystallise alone and do not form a solid solution. However, grains of LaMnO₃ compound were observed to be formed through a solid-state reaction for T > 800 degC. The ac-conductance and capacitance were studied, as a function of frequency and gate voltage. It was found that the "correlated barrier hopping" CBH model controls the frequency dependence of the conductivity, while the Kramers-Kronig (KK) relations explain the frequency dependence of the relative permittivity. The parameters of CBH model were determined showing that the ac-conduction is realised by a single-polaron hopping mechanism