Analog reservoir computing (ARC) systems have attracted attention owing to their efficiency in processing temporal information. However, the distinct functionalities of the system components pose challenges for hardware implementation. Herein, we report a fully integrated ARC system that leverages material versatility of the ferroelectric-to-mixed phase boundary (MPB) hafnium zirconium oxides integrated onto indium–gallium–zinc oxide thin-film transistors (TFTs). MPB-based TFTs (MPBTFTs) with nonlinear short-term memory characteristics are utilized for physical reservoirs and artificial neuron, while nonvolatile ferroelectric TFTs mimic synaptic behavior for readout networks. Furthermore, double-gate configuration of MPBTFTs enhances reservoir state differentiation and state expansion for physical reservoir and processes both excitatory and inhibitory pulses for neuronal functionality with minimal hardware burden. The seamless integration of ARC components on a single wafer executes complex real-world time-series predictions with a low normalized root mean squared error of 0.28. The material-device co-optimization proposed in this study paves the way for the development of area- and energy-efficient ARC systems.

Gas sensor technology is widely utilized in various areas ranging from home security, environment and air pollution, to industrial production. It also hold great promise in non-invasive exhaled breath detection and an essential device in future internet of things. The past decade has witnessed giant advance in both fundamental research and industrial development of gas sensors, yet current efforts are being explored to achieve better selectivity, higher sensitivity and lower power consumption. The sensing layer in gas sensors have attracted dominant attention in the past research. In addition to the conventional metal oxide semiconductors, emerging nanocomposites and graphene-like two-dimensional materials also have drawn considerable research interest. This inspires us to organize this comprehensive 2020 gas sensing materials roadmap to discuss the current status, state-of-the-art progress, and present and future challenges in various materials that is potentially useful for gas sensors.

In this work, the low-frequency noise (LFN) characteristics of hafnium-zirconium oxide (HZO) ferroelectric field-effect transistors (FeFETs) with and without high-pressure forming gas annealing (HPA) treatment are investigated. The origin of $1/ {f}$ noise in the FeFET without HPA is changed from carrier number fluctuation to Hooge’s mobility fluctuation after wake-up due to the remote phonon scattering from the polarized HZO. Also, Hooge’s parameter is increased by the program/erase (P/E) cycling-induced stress. On the contrary, only the correlated mobility fluctuation is increased after the wake-up in the FeFET with HPA. Furthermore, the LFN of the FeFET with HPA shows robustness to P/E cycling-induced stress after the wake-up, showing superb endurance performance.

In contrast to RRAMs, the 1/f noise of the FTJ in the LRS is approximately two orders of magnitude larger than that in the HRS, indicating that the conduction mechanism in each state differs significantly.

We investigate the effects of length ( ${L}$ ) and width ( ${W}$ ) scaling on the low-frequency noise characteristics of the ferroelectric tunnel junction (FTJ). The FTJ is composed of metal/ferroelectric/dielectric/semicondu- ctor (TiN/HfZrO₂/SiO₂/ ${n}^{+}$ Si). In the high-resistance state, 1/ ${f}$ noise increases proportionally to 1/ ${W}^{\alpha }{L}^{\beta }$ ( $\alpha \cong ~1$ , $\beta >1$ ), whereas the shot noise has no scaling dependence. In the low-resistance state, the 1/ ${f}$ noise of the FTJ shows a more sensitive dependence on ${L}$ scaling than ${W}$ scaling since the switching and conduction mechanisms are more affected by the process-induced damaged edge regions.

We demonstrate the factors that determine the tunneling electroresistance (TER) of the ferroelectric tunnel junction (FTJ) by investigating the effects of temperature ( T ) and the number of cycles ( N ) on remnant polarization ( P_r ) and carrier transport process. The fabricated FTJs have a metal/ ferroelectric/ insulator/semiconductor structure. The P_r is increased with increasing T and N due to oxygen vacancy redistribution. However, the increased P_r in a higher T and N does not improve the TER ratio. Using current-voltage characterization and low-frequency noise spectroscopy, we reveal that the carrier transport process at the interface between the ferroelectric and dielectric layers becomes more important than P_r in determining the TER ratio.