DC-conduction mechanism in crystalline oxidised La and La–Mn films grown on p-Si substrate

Abstract

Crystalline lanthanum oxide (LAO) and lanthanum–manganese (La–Mn) oxide thin films were prepared on p-Si substrates and characterised by X-ray fluorescence (XRF) and X-ray diffraction (XRD) methods. Hydroxide compounds [La(OH) 3 and LaOOH] in addition to La 2O 3 structure were detected in the prepared crystalline LAO films. Those hydroxide compounds reduced the dielectric constant of the prepared LAO to 6.4. The XRD study of La–Mn oxide films shows that La oxide and Mn oxide crystallised each alone at 600 °C without forming one complex compound or a solid solution. Furthermore, lanthanum hydroxide compounds were not detected in La–Mn oxide samples. The oxide-voltage dependence of the DC-current density for both LAO and La–Mn oxide films were found to follow the voltage dependent part of Richardson–Schottky (RS) equation, and therefore, the field-lowering coefficient and the dynamic relative permittivity were determined. On the other hand, the temperature dependence of the DC-leakage current density for both types of films was not obeying the temperature-dependence part of RS formula. It shows that the leakage current in crystalline LAO and La–Mn oxide insulating films have a metallic-temperature behaviour. This behaviour was explained due to the superimposing of RS mechanism with another conduction mechanism that was suggested to be the carrier-trapping mechanism. Generally, the experimental data demonstrated that addition of Mn oxide to La oxide forming La–Mn oxide that almost terminate the hygroscopic products does not change the DC-conduction nature and does not improve the insulating quality towards that of pure La 2O 3.