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A novel transient electronics technology that is capable of completely dissolving or decomposing in certain conditions after a period of operation offers unprecedented opportunities for medical implants, environmental sensors, and other applications. Here, we describe a biodegradable, flexible silicon-based electronic system that detects NO species with a record-breaking sensitivity of 136 Rs (5 ppm, NO2) and 100-fold selectivity for NO species over other substances with a fast response (~30 s) and recovery (~60 s). The exceptional features primarily depend on not only materials, dimensions, and design layouts but also temperatures and electrical operations. Large-scale sensor arrays in a mechanically pliable configuration exhibit negligible deterioration in performance under various modes of applied loads, consistent with mechanics modeling. In vitro evaluations demonstrate the capability and stability of integrated NOx devices in severe wet environments for biomedical applications. Biomedical electronics: Getting a whiff of bad health Degradable devices that monitor health by measuring gases emitted by the body have been developed by researchers in South Korea, the UK and the USA. Biodegradable electronics, devices that decay naturally over time, are potentially useful for medical devices. They can be used internally as implants that don't need to be surgically removed or externally as wearable health monitors. Chong-Yun Kang and Suk-Won Hwang from Korea University in Seoul and their colleagues have developed a biodegradable, flexible silicon nanomembrane to detect nitric oxide with a high sensitivity andselectivity and a fast response time. Nitric oxide sensors are important for health monitoring as the gas is associated with many physiological processes including regulation of the vascular system and blood flow. In vitro experiments in aqueous solutions demonstrated the feasibility of their devices for disposable medical implants. Soft, transient silicon-based gas sensing system capable of detecting nitrogen oxides with remarkable sensitivity and selectivity is presented in this report. The results provide materials, device layouts, manufacturing process, and theorectical modeling illlustrating the capabilities and operational aspects. In vitro experiments demonstrate the possibilities for disposable environmental monitors and temporary biomedical implants. [ABSTRACT FROM AUTHOR]

A K2-mNb2O6-m/2 single crystal with a pyrochlore phase formed when the Nb2O5 + x mol% KOH specimens with 0.6 ≤ x ≤ 1.2 were solvothermally heated at 230 °C for 24 h. They have an octahedral shape with a size of 100 μm, and the composition of this single crystal is close to K1.3Nb2O5.65. The single-crystal KNbO3 formed when the single-crystal K2-mNb2O6-m/2 was annealed at a temperature between 600 °C and 800 °C with K2CO3 powders. When annealing was conducted at 600 °C (or with a small amount of K2CO3), the KNbO3 single crystal has a rhombohedral structure that is stable at low temperatures (< − 10 °C). The formation of the rhombohedral KNbO3 structure can be explained by the presence of the K+ vacancies in the specimen. The KNbO3 single crystal with an orthorhombic structure formed when the K2-mNb2O6-m/2 single crystal was annealed at 800 °C with 20 wt% of K2CO3. [ABSTRACT FROM AUTHOR]

At present, the generation of heterostructures with two dimensional electron gas (2DEG) in amorphous LaAlO (a-LAO)/SrTiO (STO) has been achieved. Herein, we analysed thermal stability of 2DEG at a-LAO/STO interfaces in comparison with 2DEG at crystalline LaAlO (c-LAO)/STO interfaces. To create 2DEG at LAO/STO interface, regardless of growing temperature from 25 to 700 °C, we found that environment with oxygen deficient during the deposition of LAO overlayer is essentially required. That indicates that the oxygen-poor condition in the system is more essential than the crystalline nature of LAO layer. 2DEG at a-LAO/STO interface is depleted upon ex situ annealing at 300 °C under 300 Torr of oxygen pressure, while that in c-LAO/STO interface is still maintained. Our result suggests that the LAO overlayer crystallinity critically affects the thermal-annealing-induced depletion of 2DEG at a-LAO/STO interface rather than the generation of 2DEG. We clearly provide that amorphous TiO can efficiently prevent the thermal degradation of 2DEG at the a-LAO/STO interface, which gives a cornerstone for achieving thermal-stable 2DEG at a-LAO/STO interface. [ABSTRACT FROM AUTHOR]

Here we report comprehensive study of 2DEG at a-LAO/STO interfaces in comparison with 2DEG at crystalline LaAlO (c-LAO)/STO interfaces. We observe that the oxygen deficient environment during the deposition of LAO overlayer is essentially required to create 2DEG at LAO/STO interface regardless of growth temperature from 25°C to 700°C, indicating that the oxygen-poor condition in the system is more important than the crystallinity of LAO layer. The critical thickness (2.6 nm) of 2DEG formation at a-LAO/STO heterostructure is thicker than (1.6 nm) that at c-LAO/STO. Upon ex-situ annealing at 300°C under 300 mTorr of oxygen pressure, 2DEG at a-LAO/STO interface is annihilated, while that in c-LAO/STO interface is still maintained. With combing these findings and scanning transmission electron microscope (STEM) analysis, we suggest that oxygen vacancies at the LAO surface is attributed to the origin of 2DEG formation at the LAO/STO and the crystallinity of the LAO overlayer plays a critical role in the annihilation of 2DEG at a-LAO/STO interface rather than in the formation of 2DEG. This work provides a framework to understand the importance of prohibiting the LAO surface from being oxidized for achieving thermally stable 2DEG at a-LAO/STO interface. [Figure not available: see fulltext.] [ABSTRACT FROM AUTHOR]

Unlike bulk materials, many physical properties of thin-film materials depend on film thickness due to extrinsic effects such as residual stress and the dead layer. In this work, the effect of thickness on the electrocaloric properties of PbLa(ZrTi)O(10/65/35) (PLZT) films grown by the sol-gel method was studied experimentally. In the sol-gel synthesis, the annealing process results in residual stress and the metal-dielectric contact generates a dead layer. These extrinsic effects influence the dielectric and ferroelectric properties of the thin films, and their roles are film thickness dependent. For PLZT of nanometer thickness (from 420 nm to 1080 nm), the permittivity and polarization, and their temperature dependences, showed strong dependence on film thickness. In particular, in the temperature range from 70°C to 350°C, the electrocaloric temperature change showed threefold improvement (from 0.2°C to 0.6°C) as the thickness was increased from 420 nm to 840 nm. This work will aid development of polycrystalline thin films including PLZT for electrocaloric applications. [ABSTRACT FROM AUTHOR]

The performance of cantilever piezoelectric energy harvesters using three types of piezoelectric materials, relaxor ferroelectric 0.7Pb(MgNb)O-0.3PbTiO (PMN-PT) single crystals oriented along the 〈110〉 and 〈001〉 directions, and a PZT-based ceramic, were investigated. The 〈110〉 and 〈001〉 oriented PMN-PT single crystals, which have a rhombohedral phase and spontaneous polarization along the 〈111〉 direction, presented electromechanical coupling factor k's of 0.78 and 0.42, respectively. The cantilever-type energy harvester operated by 31 resonance mode generated a larger output power of 1.07 mW for the 〈110〉 oriented PMN-PT single crystal compared to those of the other materials. The effective electromechanical coupling factor of the piezoelectric energy harvester with the 〈110〉 oriented crystal also reached 0.25, not achievable with the other piezoelectric materials. These results demonstrate that the domain engineering of the piezoelectric single crystals can provide higher design flexibility for a tiny energy harvester. [ABSTRACT FROM AUTHOR]

The microwave dielectric properties of $$\left( {1 - x} \right)\left( {Al_{1/2} Ta_{1/2} } \right)O_2 - x\left( {Mg_{1/3} Ta_{2/3} } \right)O_2$$ (AMT) $$\left( {0 \leqslant x \leqslant 1.0} \right)$$ ceramics and the design of small coplanar waveguide fed antenna (CPWFA) have been investigated. ( $$\left( {Al_{1/2} Ta_{1/2} } \right)O_2$$ and ( $$\left( {Mg_{1/3} Ta_{2/3} } \right)O_2$$ have orthorhombic and tetragonal structure, respectively. As ( $$\left( {Mg_{1/3} Ta_{2/3} } \right)O_2$$ concentration increased, AMT ceramics transformed into the tetragonal structure. Specimens having tetragonal single phase could be obtained above x=0.6. As ( $$\left( {Mg_{1/3} Ta_{2/3} } \right)O_2$$ concentration increased, the grain size, dielectric constant $$\varepsilon _r$$ and quality factor (Q) significantly increased and the temperature coefficient of resonant frequency $$\tau _f$$ changed from negative to positive. The $$\tau _f$$ of $$0 ppm ^\circ C^{ - 1}$$ was realized at x=0.65 and the Q · fO value and $$\varepsilon _f$$ for this composition were 112 470 GHz and 26.1, respectively. Newly developed $$0.35\left( {Al_{1/2} Ta_{1/2} } \right)O_2 - 0.65\left( {Mg_{1/3} Ta_{2/3} } \right)O_2$$ dielectric materials were used for 1.5 GHz band CPWFA design and fabrication. The size of the CPWFA can be reduced by using high dielectric constant AMT ceramics, insetting slits into the patch, and fabricating CPW feed line in the ground plane. The slits play a role in not only lowering a center frequency but also fine tuning for the proposed antenna together with the open stub of CPW feed line. The CPWFA with slits has a lower center frequency than the conventional CPWFA, which suggests that the antenna size can be reduced by as much as 16.3%. The structure simulations of the CPWFAs have been performed to obtain impedance matching and to investigate the effects of slits. Experimental results of the fabricated device were in good agreement with the simulation. [ABSTRACT FROM AUTHOR]

The microwave dielectric properties of (Pb1-xCax){(Fe0.5Nb0.5)1-ySny}O3 ceramics (0.4 ≤ x ≤ 0.6, y = 0.05, 0.1) and design of 900 MHz band 2-pole monoblock band pass filter (BPF) have been investigated to fabricate BPF. Single-phase specimens having orthorhombic perovskite structure similar to CaTiO3 could be obtained in the compositions of Pb1-xCax){(Fe0.5Nb0.5)1-ySny}O3 (0.4 ≤ x ≤ 0.6, y = 0.05, 0.1). The substitution of Sn for Fe0.5Nb0.5) significantly increased the quality factor Q and slightly decreased the dielectric constant (ɛr). The temperature coefficient of the resonant frequency of 0 ppm °C−1 was realized at x = 0.55 and y = 0.1. The Q · f0 value and (ɛr) for this composition were found to be 8600 GHz and 86, respectively. A monoblock λ/4 dielectric BPF for 900 MHz band portable telephone terminal is presented. This BPF is a kind of combline filter. Computer-aided design (CAD) was used in the modeling procedure. The equivalent circuit of the monoblock BPF is represented by transmission lines and lumped elements based on Zoe and Zoo. A BPF model was designed for surface mounted device (SMD) types. The simulations of the equivalent circuit and BPF structure have been performed to optimize the filter design. Newly developed Pb0.45Ca0.55){(Fe0.5Nb0.5)0.9Sn0.1}O3 dielectric materials were used for BPF fabrication. Experimental results of the fabricated device were in good agreement with the simulation. [ABSTRACT FROM AUTHOR]

The stress inevitably imposed during electrochemical reactions is expected to fundamentally affect the electrochemistry, phase behavior and morphology of electrodes in service. Here, we show a strong stress-composition coupling in lithium binary alloys during the lithiation of tin-tin oxide core-shell nanoparticles. Using in situ graphene liquid cell electron microscopy imaging, we visualise the generation of a non-uniform composition field in the nanoparticles during lithiation. Stress models based on density functional theory calculations show that the composition gradient is proportional to the applied stress. Based on this coupling, we demonstrate that we can directionally control the lithium distribution by applying different stresses to lithium alloy materials. Our results provide insights into stress-lithium electrochemistry coupling at the nanoscale and suggest potential applications of lithium alloy nanoparticles. Electrochemical reactions can generate stresses that detrimentally affect battery electrodes. Here, the authors directly image the lithiation of core-shell tin-based nanoparticles and show that lithium can be redistributed by applying stress and change the nanoparticle composition. [ABSTRACT FROM AUTHOR]

Manipulation of electrons in a solid through transmitting, storing, and switching is the fundamental basis for the microelectronic devices. Recently, the electroresistance effect in the ferroelectric capacitors has provided a novel way to modulate the electron transport by polarization reversal. Here, we demonstrate a giant electroresistive ferroelectric diode integrating a ferroelectric capacitor into two-dimensional electron gas (2DEG) at oxide interface. As a model system, we fabricate an epitaxial Au/Pb(Zr0.2Ti0.8)O3/LaAlO3/SrTiO3 heterostructure, where 2DEG is formed at LaAlO3/SrTiO3 interface. This device functions as a two-terminal, non-volatile memory of 1 diode-1 resistor with a large I+/I− ratio (>108 at ±6 V) and Ion/Ioff ratio (>107). This is attributed to not only Schottky barrier modulation at metal/ferroelectric interface by polarization reversal but also the field-effect metal-insulator transition of 2DEG. Moreover, using this heterostructure, we can demonstrate a memristive behavior for an artificial synapse memory, where the resistance can be continuously tuned by partial polarization switching, and the electrons are only unidirectionally transmitted. Beyond non-volatile memory and logic devices, our results will provide new opportunities to emerging electronic devices such as multifunctional nanoelectronics and neuromorphic electronics. [ABSTRACT FROM AUTHOR]

Piezoelectric materials capable of converting between mechanical and electrical energy have a great range of potential applications in micro- and nano-scale smart devices; however, their performance tends to be greatly degraded when reduced to a thin film due to the large clamping force by the substrate and surrounding materials. Herein, we report an effective method for synthesizing isolated piezoelectric nano-materials as means to relax the clamping force and recover original piezoelectric properties of the materials. Using this, environmentally friendly single-crystalline NaxK1-xNbO3 (NKN) piezoelectric nano-rod arrays were successfully synthesized by conventional pulsed-laser deposition and demonstrated to have a remarkably enhanced piezoelectric performance. The shape of the nano-structure was also found to be easily manipulated by varying the energy conditions of the physical vapor. We anticipate that this work will provide a way to produce piezoelectric micro- and nano-devices suitable for practical application, and in doing so, open a new path for the development of complex metal-oxide nano-structures. [ABSTRACT FROM AUTHOR]

Recently, piezoelectric and triboelectric energy harvesting devices have been developed to convert mechanical energy into electrical energy. Especially, it is well known that triboelectric nanogenerators have a simple structure and a high output voltage. However, whereas nanostructures improve the output of triboelectric generators, its fabrication process is still complicated and unfavorable in term of the large scale and long-time durability of the device. Here, we demonstrate a hybrid generator which does not use nanostructure but generates much higher output power by a small mechanical force and integrates piezoelectric generator into triboelectric generator, derived from the simultaneous use of piezoelectric and triboelectric mechanisms in one press-and-release cycle. This hybrid generator combines high piezoelectric output current and triboelectric output voltage, which produces peak output voltage of ~370 V, current density of ~12 μA·cm−2, and average power density of ~4.44 mW·cm−2. The output power successfully lit up 600 LED bulbs by the application of a 0.2 N mechanical force and it charged a 10 μF capacitor to 10 V in 25 s. Beyond energy harvesting, this work will provide new opportunities for developing a small, built-in power source in self-powered electronics such as mobile electronics. [ABSTRACT FROM AUTHOR]