Oxygen Vacancy Kinetics Mechanism of the Negative Forming-Free Process and Multilevel Resistance Based on Hafnium Oxide RRAM

Abstract

Switching between high resistance states and low resistance states in a resistive random access memory device mainly depends on the formation and fracture of conductive filaments. However, the randomness of the conductive filament growth and the potential breakdown of the large voltage in the forming process will lead to unstable resistive switching and memory performance. We studied the possible natural forming process of conductive filaments for intrinsic defects under the influence of top electrode material based on the structure of W/HfO2-x/Pt. Such a simple device shows long retention time and great endurance cycles. The dendritic oxygen vacancy (VO) conductive filament model was constructed, and the dynamic VO migration under directional external bias was described according to the characteristic electrical performance. In addition, we also explored the relationship between the multilevel resistance and the evolution of a dendritic VO conductive filament, signifying the potential application of multilevel storage in the future. Furthermore, a Ag/HfO2-x/Ag selector was fabricated to assemble the memory device in wire connection which exhibits the potential of eliminating leaky current in the memory array. The connection also indicates that the fabrication process of the 1S1R structure can be simplified by using the same functional layer.

Oxygen Vacancy Density Dependence with a Hopping Conduction Mechanism in Multilevel Switching Behavior of HfO2-Based Resistive Random Access Memory Devices

“…A V o 2+ evolution model was also proposed by Qi et al . to explain the dendritic filament under different negative electric fields . Although these works of literature exhibit various methods of explaining filament evolution in multilevel states, there have been limited physics understanding on the behavior and density of oxygen vacancies ( n D ) at different stopping reset voltages ( V stop ).…”

“…25 Numerical models were also proposed by Larentis et al and Kim et al to explore temperature and fieldaccelerated migration of V o 2+ . 26,27 Arrhenius equation models were also investigated by Chiu et al and Khurana et al 28,29 Furthermore, a negative voltage-modulated multilevel resistive switching during reset was observed and explained using conduction mechanisms by Chakrabarti et al and Samanta et al 30,31 33 Although these works of literature exhibit various methods of explaining filament evolution in multilevel states, there have been limited physics understanding on the behavior and density of oxygen vacancies (n D ) at different stopping reset voltages (V stop ). Such a study is important because a combination of experimental and theoretical aspects will provide a more comprehensive understanding of filament evolution in multilevel state RRAM.…”

Phase/Interfacial-Engineered Two-Dimensional-Layered WSe2 Films by a Plasma-Assisted Selenization Process: Modulation of Oxygen Vacancies in Resistive Random-Access Memory

“…For all measurements, the potential was applied on a top electrode, whereas the bottom electrode was kept grounded. Since Pt has less binding force with oxygen atoms than W, the oxygen ion migration to and from the W electrode is considered the main mechanism of the RS. , The negative bias of −4 V with a compliance current ( I C ) of 1 mA was given to SET the device to a low-resistance state (LRS), while the positive bias of 2.5 V was given to RESET the device back to the high-resistance state (HRS). The coefficient of variation, C V = σ/μ (where σ and μ are the standard deviation and mean, respectively), shows remarkable uniformity of −20 and 20% for SET and RESET voltages with the 2D-layered WSe 2 film at the plasma-assisted selenization temperature of 300 °C (Figure i,j).…”

Enhanced Memristive Performance via a Vertically Heterointerface in Nanocomposite Thin Films for Artificial Synapses

“…One is the conductive filament type, wherein resistance modulation occurs through the creation or rupture of a conductive channel. 14 Typically, the constituents forming this conductive channel are oxygen vacancies (OVs) residing within the functional layer or highly mobile metal atoms in the active electrode, driven by an electric field. There are some reports on the direct observation of the formation/ rupture of the conductive filaments, mainly using in situ transmission electron microscopy (TEM) to observe the dynamic evolution of the conducting filaments.…”