Machine Learning-Powered Ultrahigh Controllable and Wearable Magnetoelectric Piezotronic Touching Device.

Recent advancements in nanomaterials have enabled the application of nanotechnology to the development of cutting-edge sensing and actuating devices. For instance, nanostructures' collective and predictable responses to various stimuli can be monitored to determine the physical environment of the nanomaterial, such as temperature or applied pressure. To achieve optimal sensing and actuation capabilities, the nanostructures should be controllable. However, current applications are limited by inherent challenges in controlling nanostructures that counteract many sensing mechanisms that are reliant on their area or spacing. This work presents a technique utilizing the piezo-magnetoelectric properties of nanoparticles to enable strain sensing and actuation in a flexible and wearable patch. The alignment of nanoparticles has been achieved using demagnetization fields with computational simulations confirming device characteristics under various types of deformation followed by experimental demonstrations. The device exhibits favorable piezoelectric performance, hydrophobicity, and body motion-sensing capabilities, as well as machine learning-powered touch-sensing/actuating features.

Sensitivity-Enhanced, Room-Temperature Detection of NH3 with Alkalized Ti3C2Tx MXene.

A layered Ti3C2Tx MXene structure was prepared by etching MAX-phase Ti3AlC2 with hydro-fluoric acid (HF), followed by alkalization in sodium hydroxide (NaOH) solutions of varying concentrations and for varying durations. Compared to sensors utilizing unalkalized Ti3C2Tx, those employing alkalized Ti3C2Tx MXene exhibited enhanced sensitivity for NH3 detection at room temperature and a relative humidity of 40%. Both the concentration of NaOH and duration of alkalization significantly influenced sensor performance. Among the tested conditions, Ti3C2Tx MXene alkalized with a 5 M NaOH solution for 12 h exhibited optimal performance, with high response values of 100.3% and a rapid response/recovery time of 73 s and 38 s, respectively. The improved sensitivity of NH3 detection can be attributed to the heightened NH3 adsorption capability of oxygen-rich terminals obtained through the alkalization treatment. This is consistent with the observed increase in the ratio of oxygen to fluorine atoms on the surface terminations of the alkalization-treated Ti3C2Tx. These findings suggest that the gas-sensing characteristics of Ti3C2Tx MXene can be finely tuned and optimized through a carefully tailored alkalization process, offering a viable approach to realizing high-performance Ti3C2Tx MXene gas sensors, particularly for NH3 sensing applications.

Optimizing Al-doped ZrO2 as the gate dielectric for MoS2 field-effect transistors.

In this work, we investigate the effects on the electrical properties of few-layered MoS2 field-effect transistors (FETs) following Al incorporation into ZrO2 as the gate dielectrics of the devices. A large improvement in device performance is achieved with the Al-doped ZrO2 gate dielectric when Zr:Al = 1:1. The relevant MoS2 transistor exhibits the best electrical characteristics: high carrier mobility of 40.6 cm2 V-1 s-1 (41% higher than that of the control sample, and an intrinsic mobility of 68.0 cm2 V-1 s-1), a small subthreshold swing of 143 mV dec-1, high on/off current ratio of 6 × 106 and small threshold voltage of 0.71 V. These are attributed to the facts that (i) Al incorporation into ZrO2 can decrease its oxygen vacancies; densify the dielectric film; and smooth the gate dielectric surface, thus reducing the traps at/near the Zr0.5Al0.5O y /MoS2 interface and the gate leakage current; (ii) adjusting the dielectric constant of the gate dielectric to an appropriate value, which achieves a reasonable trade-off between the gate screening effect on the Coulomb-impurity scattering and the surface optical phonon scattering. These results demonstrate that optimized Zr0.5Al0.5Oy is a potential gate dielectric material for MoS2 FET applications.

Effects of HfO2 encapsulation on electrical performances of few-layered MoS2 transistor with ALD HfO2 as back-gate dielectric.

The carrier mobility of MoS2 transistors can be greatly improved by the screening role of high-k gate dielectric. In this work, atomic-layer deposited (ALD) HfO2 annealed in NH3 is used to replace SiO2 as the gate dielectric to fabricate back-gated few-layered MoS2 transistors, and good electrical properties are achieved with field-effect mobility (µ) of 19.1 cm2 V-1 s-1, subthreshold swing (SS) of 123.6 mV dec-1 and on/off ratio of 3.76 × 105. Furthermore, enhanced device performance is obtained when the surface of the MoS2 channel is coated by an ALD HfO2 layer with different thicknesses (10, 15 and 20 nm), where the transistor with a 15 nm HfO2 encapsulation layer exhibits the best overall electrical properties: µ = 42.1 cm2 V-1 s-1, SS = 87.9 mV dec-1 and on/off ratio of 2.72 × 106. These improvements should be associated with the enhanced screening effect on charged-impurity scattering and protection from absorption of environmental gas molecules by the high-k encapsulation. The capacitance equivalent thickness of the back-gate dielectric (HfO2) is only 6.58 nm, which is conducive to scaling of the MoS2 transistors.