Bipolar and unipolar resistive switching in Cu-doped SiO2

Scalable nonvolatile memory devices that operate at low voltage and current, exhibit multilevel cell capability, and can be read nondestructively using simple circuitry, are highly sought after. Such devices are of particular interest if they are compatible with back-end-of-line processing for CMOS integrated circuits. A variety of resistance-change technologies show promise in this respect, but a new approach that is based on switching in copper-doped silicon dioxide may be the simplest and least expensive to integrate. This paper describes the characteristics Of W-(Cu/SiO2)-Cu programmable metallization cell (PMC) devices formed by the thermal diffusion of Cu into deposited SiO2 PMC devices operate by the electrochemical control of metallic pathways in solid electrolytes. Both unipolar and bipolar resistive switching could be attained in these devices. Bipolar switching, which is identical to that seen in PMC devices based On other solid electrolytes, was observed for low bias (a few tenths of volts) and programming currents in the microampere range. The resistance ratio between high and low states was on the order of 10(3), and a multibit storage is considered possible via the strong dependence of ON-state resistance on programming current. The low and high resistance states were stable for more than 5 x 10(4) s. The devices could be made to exhibit unipolar switching using a negative bias on the order of -1V combined with erase currents of hundreds of microampere to a few milliampere. In this case, the OFF/ON ratio was 10(6)

Structure, vibrations and electronic transport in silicon suboxides: Application to physical unclonable functions

This work focuses on the structure and electronic transport in atomistic models of silicon suboxides (a-SiOx; x = 1.3,1.5 and 1.7) used in the fabrication of a Physical Unclonable Function (PUF) devices. Molecular dynamics and density functional theory simulations were used to obtain the structural, electronic, and vibrational properties that contribute to electronic transport in a-SiOx. The percentage of Si-[Si1, O3] and Si-[Si3, O1], observed in a-SiO1.3, decrease with increasing O ratio. Vibrations in a-SiOx showed peaks that result from topological defects. The electronic conduction path in a-SiOx favored Si-rich regions and Si atoms with dangling bonds formed charge-trapping sites. For doped a-SiOx, the type of doping results in new conduction paths, hence qualifying a-SiOx as a viable candidate for PUF fabrication as reported by Kozicki [Patent-Publication-No.: US2021/0175185A1, 2021]