The chemical and morphological properties of thin aluminum oxide film surfaces (Al₂O₃ having 10 nm in thickness) in the as-deposited (dry) and after immersion (in pH buffer solutions) conditions were studied. Careful measurement conditions have been followed in order to determine any possible physical and/or chemical change on the surface of these films (after immersion in pH), so that proper correlation to their high and stable sensitivity to pH is possible. After deposition of thin Al₂O₃ films (by Atomic Layer Deposition, ALD) on chemically oxidized p-type silicon wafers, the resulting Al₂O₃/SiO_X/Si stacked structures were characterized by Fourier-Transform Infrared Spectroscopy (FTIR) and Atomic Force Microscopy (AFM) before and after immersion in pH buffer solutions. Also, the Capacitance-Voltage (C-V) and Current-Voltage (I-V) characteristics were obtained after fabrication of Metal-Insulator-Semiconductor (MIS) devices in order to correlate the good chemical and morphological characteristics of thin Al₂O₃ to its electrical properties. Based on the characterization results, low surface oxidation/dissolution mechanisms are found in ALD aluminum oxide films when immersed in pH buffer solutions during short immersion times (immersion time ≤ 10 minutes); therefore, leading to the characteristic slow degradation of the sensitivity to pH for this dielectric material.

We present the resistive switching characteristics of Metal-Insulator-Metal (MIM) devices based on amorphous Al₂O₃which is deposited by Atomic Layer Deposition (ALD). A maximum processing temperature for this memory device is 300°C, making it ideal for Back-End-of-Line (BEOL) processing. Although some variations in the forming, set, and reset voltages (VFORM,VSET, andVRESET) are obtained for many of the measured MIM devices (mainly due to roughness variations of the MIM interfaces as observed after atomic-force microscopy analysis), thememristoreffect has been obtained after cyclicI-Vmeasurements. These resistive transitions in the metal oxide occur for bothbipolarandunipolarconditions, while theIOFF/IONratio is around 4–6 orders of magnitude and is formed at gate voltages ofVg<4 V. In unipolar mode, a gradual reduction inVSETis observed and is related to combined (a) incomplete dissolution of conductive filaments (made of oxygen vacancies and metal ions) which leaves some residuals and (b) thickening of chemically reduced Al₂O₃during localized Joule heating. This is important because, by analyzing the macroscopic resistive switching behavior of this MIM structure, we could indirectly relate it to microscopic and/or nanoscopic phenomena responsible for the physical mechanism upon which most of these devices operate.