The Atomic Layer Deposition technique for the fabrication of memristive devices: impact of the precursor on pre-deposited stack materials

C. P. QUINTEROS; A. HARDTDEGEN; M. BARELLA; F. GOLMAR; F. PALUMBO; J. CURIALE; P. LEVY; S. HOFFMANN-EIFERT

New uses of Micro and Nanomaterials

IntechOpen

Año: 2018; p. 3 - 23

Atomic Layer Deposition (ALD) is a standard technique employed to grow thin film oxides for a variety of applications. We describe the technique, and demonstrate its use for obtaining memristive type devices. The metal / insulator / metal stack is fabricated by means of ALD grown HfO2, deposited on top of a highly doped Si substrate with a SiO2 film and a Ti electrode. Enhanced device capabilities (forming free, self-limiting current, non-crossing hysteretic current-voltage features) are presented and discussed. Careful analysis of the stack structure by means of X-ray reflectometry, atomic force microscopy, and secondary ion mass spectroscopy revealed a modification of the device stack from the intended sequence, HfO2/Ti/SiO2/Si. Analytical studies unravel an oxidation of the Ti layer which is addressed to the use of the ozone precursor in the HfO2 ALD process. A new deposition process and the model deduced from impedance measurements support our hypothesis: the role played by ozone on the previously deposited Ti layer is found to determine overall features of the device. Besides, these ALD tailored multifunctional devices exhibit rectification capability, and long enough retention to deserve their use as memory cells in a crossbar architecture and multibit approach, envisaging other other potential applications.