Produção e caracterização elétrica de filmes finos de telureto com nanopartículas de ouro depositados pela técnica sputtering para aplicação em memórias.

Abstract

This work has the objective to fabricate and characterize electrically tellurite thin films containing gold nanoparticles, deposited by the sputtering technique, for application in memory devices. Thin films were produced from ceramic tellurite targets and gold nanoparticles were nucleated in order to observe their influence on memory behavior. An appropriate method was developed for the nucleation of the nanoparticles by means of heat treatment. Films with different nanoparticles sizes and concentration and different oxygen fluxes during the deposition, were produced. The films were characterized by techniques such as Transmission Electron Microscopy (TEM), Profilometry, Rutherford Backscatter Spectrometry (RBS) and current x voltage (I-V) curves. Using I-V measurements, it was possible to identify the best conditions for memory applications and correlate them with the process variables studied. The results showed that the best condition for memory applications was found in films with 100 nm thickness and deposited with oxygen flow of 1 sccm, opening shutter in 50 and heat treated for 10 or 20 hours at 325 ºC. In these cases, current abrupt increase (4 orders of magnitude) was observed at about 6.5 V for 10 hours of heat treatment and 3.5 V for 20 hours of heat treatment, indicating the transition from high impedance state to low impedance state. Gold nanoparticles provide a larger electron storage capability, and do not favor the electric transport through the insulator; they act as traps for electrical charges, which reduces the leak current to lower levels. It was studied the influence of the gold nanoparticles diameter and volumetric concentration on the voltage associated to the abrupt current. These parameters played an important role in the memory effect, as they determined the facility/difficulty to fill and saturate the traps (Au nanoparticles) with electrons. The materials studied in the present work, based on TeO2-ZnO thin films with Au nanoparticles, are promising for applications in nonvolatile memory device with similar characteristics to organic materials used for the same purpose.