In this paper, we report the demonstration of highly sensitive flexible strain sensors formed by a network of metallic nanoparticles (NPs) grown under vacuum on top of a cracked thin alumina film which has been deposited by atomic layer deposition.
Highlights
A hybrid nanomaterial based gas-sensing array has been used for pesticide detection.
The pesticide is the commercially available organophosphate based Chloract 48 EC.
The array has successfully distinguished between relative humidity and pesticide.
The successful operation of the array has been validated via the PCA method.
This study expands the limited available results related to pesticide gas-sensors.
Accurate control over the various resistance states is highly desired in order to attain reliable multilevel memory performance. However, due to the inherent random nature of oxygen vacancy creation, serious variability issues may arise. In this work, we demonstrate promising multilevel capability with ultra‐low power consumption in the range of nW, using sub‐200 nA operating current in a 45 nm TiO2−x‐based resistive random access memory (RRAM) with embedded small (≈5 nm in diameter) Pt nanocrystals (NCs). As the resistance values present a strong dependence on both the oxygen vacancy density and the diameter of the conducting filament (CF), hence the degree of the variability (or uniformity) can be improved by controlling one of these two parameters. It is shown here that the presence of NCs allows for the generation of multiple and dense CFs due to the concentrated electric field around the NCs which, in turn, enhance the consecutive cycling (temporal) uniformity, even at very low operating power conditions.
In this work, the working performance of Platinum (Pt), solvent-free nanoparticle (NP)-based strain sensors made on a flexible substrate has been studied. First, a new model has been developed in order to explain sensor behaviour under strain in a more effective manner than what has been previously reported. The proposed model also highlights the difference between sensors based on solvent-free and solvent-based NPs. As a second step, the ability of atomic layer deposition (ALD) developed Al2O3 (alumina) thin films to act as protective coatings against humidity while in adverse conditions (i.e., variations in relative humidity and repeated mechanical stress) has been evaluated. Two different alumina thicknesses (5 and 11 nm) have been tested and their effect on protection against humidity is studied by monitoring sensor resistance. Even in the case of adverse working conditions and for increased mechanical strain (up to 1.2%), it is found that an alumina layer of 11 nm provides sufficient sensor protection, while the proposed model remains valid. This certifies the appropriateness of the proposed strain-sensing technology for demanding applications, such as e-skin and pressure or flow sensing, as well as the possibility of developing a comprehensive computational tool for NP-based devices.
The incorporation of metal nanocrystals (NCs) within TiO 2-x thin films offers great advantages for adjusting a wide range of non-volatile memory properties, ranging from resistive and capacitive switching to synaptic capabilities. In this study, it is demonstrated that by inserting very small NCs (%3 nm diameter) of either Pt or Ta, resistance changes over six orders of magnitude and capacitance changes over two orders of magnitude can be induced, with promising variability due to the local enhancement of the electric field effect, while these effects are attributed to the energy band diagram configuration induced by the presence of NCs. The gradual switching pattern observed exhibits also attractive synaptic properties, offering higher design flexibility for neuromorphic applications.
ExperimentalThe structure of the RRAM devices was the following: TiN (40 nm)/Ti (4 nm)/TiO 2-x (22.5 nm)/Pt or Ta NCs/TiO 2-x (22.5 nm)/Au (40 nm)/SiO 2 /Si, while the fabrication details
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