We present an investigation of structural changes in silicon-rich silicon oxide metal-insulator-metal resistive RAM devices. The observed unipolar switching, which is intrinsic to the bulk oxide material and does not involve movement of metal ions, correlates with changes in the structure of the oxide. We use atomic force microscopy, conductive atomic force microscopy, x-ray photoelectron spectroscopy, and secondary ion mass spectroscopy to examine the structural changes occurring as a result of switching. We confirm that protrusions formed at the surface of samples during switching are bubbles, which are likely to be related to the outdiffusion of oxygen. This supports existing models for valence-change based resistive switching in oxides. In addition, we describe parallel linear and nonlinear conduction pathways and suggest that the conductance quantum, G0, is a natural boundary between the high and low resistance states of our devices.

We present an investigation of structural changes in silicon-rich silicon oxide metal-insulator-metal resistive RAM devices. The observed unipolar switching, which is intrinsic to the bulk oxide material and does not involve movement of metal ions, correlates with changes in the structure of the oxide. We use atomic force microscopy, conductive atomic force microscopy, x-ray photoelectron spectroscopy, and secondary ion mass spectroscopy to examine the structural changes occurring as a result of switching. We confirm that protrusions formed at the surface of samples during switching are bubbles, which are likely to be related to the outdiffusion of oxygen. This supports existing models for valence-change based resistive switching in oxides. In addition, we describe parallel linear and nonlinear conduction pathways and suggest that the conductance quantum, G0, is a natural boundary between the high and low resistance states of our devices.

Redox-based resistive random access memory (RRAM) has the scope to greatly improve upon current methods of data storage, despite incomplete understandings of material switching mechanisms. We make use of atomic force microscopy (AFM), conductive atomic force microscopy (cAFM) and X-ray photoelectron spectroscopy (XPS) to characterise the physical processes occurring in the changes in conductance state in silicon-rich silicon oxide RRAM. Surface analyses of the insulating oxide layer of our devices are employed to establish the chemical and structural properties of pristine and switched states. The removal of oxygen from the active layer is observed to be concomitant with the appearance of varying degrees of surface distortion and regions of high conductivity in an otherwise-insulating material. These results support the currently-recognised model of a resistive switching mechanism that is reliant upon the migration of oxygen ions under an electrical bias. (© 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

Filamentary conduction in resistive switching metal- insulator-metal devices is often modeled from the circuital viewpoint using diode-like structures with series resistances. We show in this letter which arrangement of diodes and resistances is compatible with experimental multilevel set and reset I-V characteristics in electroformed TiN/SiOx/TiN structures. The proposed model is based on the solution of the generalized diode equation corresponding to N diodes arranged in parallel with a single series resistance. The model is simple yet accurate and it is able to capture the essential features exhibited by the I-V curves in the low and high bias regimes, revealing that a single equation can deal with both the low and high resistance states. An exact expression for the differential conductance suitable for small-signal analysis and circuit simulators is also provided.

Resistive RAM (RRAM) are of great interest to the silicon microelectronics industry, offering the possibility of low programming energy per bit, rapid switching, and very high levels of integration. Moreover a great effort has been devoted to exploring the potential of RRAM in neuromorphic applications. Here we present the study of silicon-rich silica films to establish the switching properties, chemical and structural changes during the resistance switching. We present electrical measurements and we discuss on structural changes using the atomic force microscopy (AFM) and conductive atomic force microscopy (CAFM). Further we use AFM to perform tomography studies of filaments. We report the emission of molecular oxygen during the resistance switching.

Redox-based resistive RAM presents a development in non-volatile data storage, despite an incomplete understanding of switching mechanisms. However, in order to optimize and standardize device behavior it is necessary to have a better understanding of physical processes governing switching. Many oxide dielectrics have been studied in relation to switching, but silicon-based devices in particular offer a high capacity for integration into existing CMOS technologies at low cost. We present analyses of silicon-rich silica films to establish the chemical and structural processes underpinning electronic resistance switching behavior. Atomic force microscopy, x-ray photoelectron spectroscopy and secondary ion mass spectroscopy are used to characterize observed resistance changes. Reduction and structural reconfiguration of the oxide is seen to be concomitant with structural distortions and the appearance of conductive regions in otherwise-insulating material. Crucially, we demonstrate for the first time the correlation between resistance switching and the emission of oxygen from an electrically stressed dielectric film. These results confirm the current model of an oxygen-based mechanism and highlight the inherent limitations imposed by gradual oxygen depletion on device lifetime.