In this work, solution shearing approach is used to fabricate sustainable, de-ionized water based 15 nm aluminum oxide (AlO_x) thin films employing a combination of low-temperature thermal annealing and deep UV exposure techniques. Their electrical performance is evaluated for memristive technology, demonstrating bipolar resistive switching and a stable ON/OFF ratio of ≈10². Devices exhibit endurance for 100 cycles and retention exceeding 40 h. Moreover, the device showcases eight voltage-regulated resistive switching states, equivalent to 4 bits. All multilevel states exhibit a significant increase in the memory window and stable retention for 3 h. This study illustrates that the resistive switching results from the conductive filament development is facilitated by oxygen vacancies. Charge conduction modeling of I–V characteristics reveals that the mechanism is dominated by space charge-limited conduction (SCLC) during filament formation, followed by Ohmic conduction. A negative differential resistance (NDR) effect occurs due to the sudden rupture of the filament when the polarity is reversed. The voltage-regulated multilevel behavior can be attributed to the enhancement of the pre-existing oxygen vacancy conductive filament or the formation of multiple filaments. Overall, the bilayer AlO_x thin film demonstrates significant potential for application in multibit-level memory storage devices.