Improving the sensitivity of LaMnO3 NTC films by Al ion implantation

Abstract

The Al ion implantation was employed to modify the NTC characteristics of LaMnO3 thin films sputtered on Si/SiO2 substrates under different annealing temperatures. The crystal structure, morphology and ion distribution of the as-sputtered LaMnO3 thin films and as-annealed Al-implanted films were carefully evaluated. Results indicated that (LaMnAlxO3)y(Al2O3)1-y composite phase existed over the annealing temperature range after Al3+ implanting into the LaMnO3 film of perovskite phase. The film was nucleated throughout and the size of the grain decreased with the increase in annealing temperature. The Al3+ implantation promoted the reduction of oxygen vacancy concentration while leading to the reduction in the equilibrium oxygen vacancy. As a result, the Mn3+/Mn4+ ratio declined and the number of carriers reduced, which helped to increase the carrier migration barrier and activation energy. The direct manifestation of the latter is the increase of the thermal constant B value from 3192 K to 2111 K based on the premise of resistivity is closed. The successful modification of a traditional perovskite-type NTC material will bring an innovative perspective to the design of advanced functional film materials and provide ideas for further exploration of the material in high B and low resistivity temperature sensor applications.