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While mixed ionic-electronic conductors with metal-insulator transition (MIT) are promising candidates for designing neuromorphic computing hardware, the fundamentals of resistive switching in these materials are yet to be well understood. This work studies the switching mechanism of the three-terminal nonvolatile redox transistor (NVRT) containing the LiCoO 2 (LCO) channel layer with tunable preferred crystallographic orientation. We used atomic force microscope nanotomography to reconstruct the 3D conductance map of NVRTs, that reveals the applied gate electric-field induces the MIT via reversible phase separation in the LCO channel layer, with the nonequilibrium thermodynamics analytical model providing validation to this mechanism. By operating in the post - percolation region, the memory properties can continuously adjust the conductance states of NVRTs. The percolation conductance mechanism via the metallic LCO phase ensures the exceptional linearity and reproducibility of conductance modulation, whereas the field-, rather than current-, induced transition results in the low energy consumption replicating key features of the living neural cells. [Display omitted] • Three-terminal transistor containing an epitaxial LiCoO 2 channel layer can mimic the potentiation/depression of a synapse. • Electrical field-induced nanoscale MIT and sequential percolation of metallic LCO phase in the transistor was verified. • A broad range and linear analog responses were achieved by modulating the device conductance in the post-percolation region. [ABSTRACT FROM AUTHOR]

Bismuth(III) sulfide (Bi 2 S 3) is a promising cathode material for aqueous zinc ion batteries (ZIBs), yet suffers from serious capacity issues due to its poor electrical conductivity and microstructural degradations. In this work, Bi 2 S 3 anchored on reduced graphene oxide (rGO) is prepared through hydrothermal reaction and is used as cathode material for aqueous ZIBs. Raman and XPS characterizations confirmed that the oxygen bridge in Bi–O–C heterostructures is successfully created during the hydrothermal synthesis. These oxygen bridges are energy favourable in the Bi 2 S 3 /rGO composite materials and serve as the electron transfer channels for rapid charge compensation during Zn2+ incorporation/extraction. Rotating ring–disc electrode (RRDE) measurements demonstrate improved electrochemical stability of the Bi 2 S 3 /rGO composite material compared to pristine Bi 2 S 3. As a result of these improved characteristics, Bi 2 S 3 /rGO composite shows notably better rate performance and cycling stability than unsupported Bi 2 S 3. Ex-situ X-ray diffraction and XPS characterizations indicate that Zn2+ undergoes a reversible conversion reaction with Bi 2 S 3 to form ZnS/Bi0, rather than being intercalated into Bi 2 S 3 crystal interlayers. The rGO substrate forms chemical bonds with bismuth in the composite material, and the strongly anchored bismuth on the rGO through a Bi–O–C bridge enables a highly reversible conversion reaction. As a result, the Bi 2 S 3 /rGO composite with 8 wt% rGO can deliver a reversible capacity of ∼186 mAh g−1 at the current density of 500 mA g−1 after 150 cycles, showing high promise as Zn-ion battery material. [ABSTRACT FROM AUTHOR]

The harmless disposal of lead paste in the spent lead-acid batteries (LABs) remains an enormous challenge in traditional pyrometallurgical recycling. Here, we introduced a hydrometallurgical method for the recycling of the spent LABs' waste to obtain the β -PbO as a novel zinc ion batteries (ZIBs) active material. The obtained β -PbO exhibits ultra-flat charge/discharge voltage platforms (0.21 mV/(mAh g−1)) and stable specific capacity. During the charge/discharge, the β -PbO spontaneously triggers the formation of (ZnSO 4)[Zn(OH) 2 ] 3 ·5H 2 O (ZHS) micro-sheets as a surface passivation layer. Moreover, the ex-situ X-ray spectra reveal that the reversible phase transformation occurs between PbSO 4 and Pb with the assistance of ZHS by adjusting the PH value on the electrode-electrolyte interface. The synergistic two-phase-reaction mechanism generates ultra-flat voltage platforms upon the charge/discharge. This "energy-saving and environment-friendly" recycling route eliminates the major source of emission of pollution particulates/gases compared to the traditional pyrometallurgical recycling, while at the same time replacing energy-consuming and environmentally detrimental processes of synthesis of current ZIBs cathodes. [ABSTRACT FROM AUTHOR]

Abstract: The analysis of the formation of ultra-thin organic films is a very important issue. In fact, it is known that the properties of organic light emitting diodes and field effect transistors are strongly affected by the early growth stages. For instance, in the case of sexithiophene, the presence of domains made of molecules with the backbone parallel to the substrate surface has been indirectly evidenced by photoluminescence spectroscopy and confocal microscopy. On the contrary, conventional scanning force microscopy both in contact and intermittent contact modes have failed to detect such domains. In this paper, we show that Ultrasonic Force Microscopy (UFM), sensitive to nanomechanical properties, allows one to directly identify the structure of sub-monolayer thick films. Sexithiophene flat domains have been imaged for the first time with nanometer scale spatial resolution. A comparison with lateral force and intermittent contact modes has been carried out in order to explain the origins of the UFM contrast and its advantages. In particular, it indicates that UFM is highly suitable for investigations where high sensitivity to material properties, low specimen damage and high spatial resolution are required. [Copyright &y& Elsevier]

Induced disorder in graphene enables changes in electrical and thermal transport. It has been shown previously that disorder is very important for electron cooling in graphene through disorder-assisted electron-phonon scattering, particularly via the supercollisions process. Here we study electron-momentum relaxation due to electron-phonon scattering while increasing the degree of disorder. With in-situ scanning thermal microscopy we monitor the temperature rise in the constriction region of a bowtie-shaped graphene device while increasing the disorder by means of feedback-controlled voltage ramps at high-current densities. Analysis of the combined thermal and electrical measurements in the low bias regime shows that the relative change of the momentum scattering rate vs temperature, as measured at room temperature, increases with strong local disorder. By excluding other candidate mechanisms for this phenomenon, including a change of the charge carriers density and activation of optical phonons, we conclude that the increase we observe in the temperature-dependent component of the scattering rate is likely due to new acoustic phonon scattering channels that open up as disorder increases. [Display omitted] [ABSTRACT FROM AUTHOR]

Scanning thermal microscopy (SThM), which enables measurement of thermal transport and temperature distribution in devices and materials with nanoscale resolution is rapidly becoming a key approach in resolving heat dissipation problems in modern processors and assisting development of new thermoelectric materials. In SThM, the self-heating thermal sensor contacts the sample allowing studying of the temperature distribution and heat transport in nanoscaled materials and devices. The main factors that limit the resolution and sensitivities of SThM measurements are the low efficiency of thermal coupling and the lateral dimensions of the probed area of the surface studied. The thermal conductivity of the sample plays a key role in the sensitivity of SThM measurements. During the SThM measurements of the areas with higher thermal conductivity the heat flux via SThM probe is increased compared to the areas with lower thermal conductivity. For optimal SThM measurements of interfaces between low and high thermal conductivity materials, well defined nanoscale probes with high thermal conductivity at the probe apex are required to achieve a higher quality of the probe-sample thermal contact while preserving the lateral resolution of the system. In this paper, we consider a SThM approach that can help address these complex problems by using high thermal conductivity nanowires (NW) attached to a tip apex. We propose analytical models of such NW-SThM probes and analyse the influence of the contact resistance between the SThM probe and the sample studied. The latter becomes particularly important when both tip and sample surface have high thermal conductivities. These models were complemented by finite element analysis simulations and experimental tests using prototype probe where a multiwall carbon nanotube (MWCNT) is exploited as an excellent example of a high thermal conductivity NW. These results elucidate critical relationships between the performance of the SThM probe on one hand and thermal conductivity, geometry of the probe and its components on the other. As such, they provide a pathway for optimizing current SThM for nanothermal studies of high thermal conductivity materials. Comparison between experimental and modeling results allows us to provide direct estimates of the contact thermal resistances for various interfaces such as MWCNT-Al (5×10 −9 ±1×10 −9 K m 2 W −1 ), Si 3 N 4 –Al (6×10 −8 ±2.5×10 −8 K m 2 W −1 ) and Si 3 N 4 −graphene (~10 −8 K m 2 W −1 ). It was also demonstrated that the contact between the MWCNT probe and Al is relatively perfect, with a minimal contact resistance. In contrast, the thermal resistance between a standard Si 3 N 4 SThM probe and Al is an order of magnitude higher than reported in the literature, suggesting that the contact between these materials may have a multi-asperity nature that can significantly degrade the contact resistance. [ABSTRACT FROM AUTHOR]