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There is a strong non-linearity between the field-emission current amplitude and field intensity. This nonlinearity degrades the dynamic range of digital signal processing in a mechanical oscillator composed of a cantilever. To solve this issue, we propose a linearization method by combining the harmonics of the field-emission current. The proposed method significantly increases the dynamic range. The nonlinearity error is $8.94\times 10^{-3}$ %FS for the proposed method, whereas it is 14.1%FS for the conventional method given by the 2nd harmonic current detection. In addition, the proposed method enables to rake up energy of the higher-order harmonics by utilizing our design framework for combining weights, thereby providing a constant derivative of the output current of the input electric field.

We experimentally evaluated the influence of stress on the Li chemical potential (μLi) and phase equilibrium in the two-phase battery electrode materials through the emf measurements while applying a mechanical load. In our measurements, we prepared an electrochemical cell by depositing a thin film of a two-phase electrode material (LiFePO4 or LiCoO2 in the two-phase region) on each of the solid electrolyte surfaces. Then we applied a mechanical load to the electrochemical cell through four-point bending, and the resulting μLi variation in the electrode material was measured as the emf between the two thin films. Our results indicated that μLi in the two-phase electrode materials immediately changed just after loading and then gradually changed while maintaining a constant mechanical load. Besides, the loading and unloading led to the μLi variation in the opposite direction. Such characteristic μLi variations could be explained by considering the change in the phase equilibrium between the two phases, which led to the Li content variation in the two phases and the stress relaxation due to the volume fraction variation of the two phases. Our results can provide valuable insights regarding the influence of stress on the performances of energy storage devices with two-phase electrode materials.

The field-emission phenomenon is exploited in a broad variety of applications and systems. Previous studies have reported that the current induced by field emission strongly and inherently depend on the temperature. This dependence enhances the noise in the current, which results in performance degradation in, for example, signal detection and communications in nanoscale receivers. In this paper, a mathematical model is presented for the suppression of the noise based on its probability density. Our experiment and analysis revealed that the density follows a Gaussian distribution, and the dependence on temperature is observed to be exponential. This result is intriguing because in the field of signal processing and communication, the influence of temperature is often considered with a noise-temperature model, namely, linear dependence. Using our derived model, we theoretically evaluated the communication performance of a nanoscale receiver; owing to the exponential dependence on temperature, severe performance degradation was found with increasing temperature. This means that, as field-emission technology continues to be developed, the temperature should be kept low, for example, at room temperature, to secure the reliability of nanoscale communication devices.

In field emission-based nanoelectromechanical systems (NEMSs), there is a strong nonlinearity between the amplitude of the field emission current signal and the field intensity of the incoming signal. This nonlinearity degrades the dynamic range and complicates the digital signal processing of NEMSs. To solve this issue, we propose a linearization method by combining the harmonics of the field emission current signal. We experimentally demonstrate this concept with a signal receiver based on carbon nanotubes. The experimental results show that the dynamic range significantly increases. Combining the harmonic current wave improves the nonlinearity error from 25.1 %FS to 8.63 × 10–3 %FS. This improvement is achieved by combining harmonics of field emission current with optimally controlled weights.

We propose and demonstrate a carbon nanotube (CNT)-based field emission nanoscale diode to realize a fully integrated nanoscale system, namely, a true nanosystem. To the best of our knowledge, this is the first time a nanodiode simultaneously achieves ease of fabrication and individual tunability of multiple CNT diodes on the nanoscale on the same substrate in a one-time process. A nanodiode comprises a single-wall CNT cathode placed on a substrate, layered insulator, and metal anode. The proposed nanodiode allows us to adjust the turn-on voltage from 1 to 2.4 V by varying the surface area of the anode. Furthermore, as an example of a basic nano-electronic system, nanodiode-based fundamental logic gates (OR and NAND) are demonstrated on a CNT. We propose a theoretical model that derives the theoretical I–V characteristics based on the image-charge method to design the nanodiode quickly. The results in this study contribute to the development of carbon-based nanoelectronic systems.

Change of the lithium chemical potential in a crystalline LiCoO 2 with the application of a mechanical stress was discussed based on the results of electromotive force ( emf ) measurements between preferentially-oriented LiCoO 2 films on Li 0.33 La 0.55 TiO 3 solid electrolytes under mechanical stress. [00 l ]-oriented LiCoO 2 films with different degrees of orientation were prepared, and it was investigated how the direction of mechanical stress to the crystal lattice affects emf . It is found that emf emerged when mechanical stress was applied. The magnitude of emf under stress was dependent not only on the magnitude of applied stress but also the degree of the film orientation. This clearly demonstrated that the crystal orientation, i.e. the direction of mechanical stress to the crystal, affects the lithium chemical potential.

Two LiCoO 2 dense film electrodes were prepared on both surfaces of a lithium ion-conducting glass ceramics, and electromotive force measurements were preformed between the film electrodes under mechanical compressive and tensile stresses by four-point bending tests. Electromotive force appeared immediately after applying the stress and disappeared after releasing the stress. The larger stress was applied, the larger electromotive force was observed. These results clearly demonstrated that the lithium chemical potential in the LiCoO 2 electrode varies under mechanical stress. The influence of the mechanical stress on the lithium chemical potential was discussed based on the relation between the CoO 2 interlayer distance and the lithium concentration in LiCoO 2 .

This work studies the enhancement factor associated with a current emitted from a multi-wall carbon nanotube to an extremely small counter electrode. The experimental data show that the field enhancement factor increases by 1.15 times when the width of the counter electrode increases from 50 to 200 nm. To better understand this enhancement effect, field intensities at the emitter surface are numerically simulated. The experimental work and simulations demonstrate that the observed field enhancement results from increases in the capacitance between the emitter and counter electrode. In addition, corrugated counter electrodes are found to greatly affect both the capacitance and enhancement factor. This is because the corrugation of the anode surface raises the capacitance and thus provides a higher current. We experimentally show that an effective surface area enlargement of 1.67 times due to the corrugation provides a 1.06-fold increase of the enhancement factor. These results should assist in the future development of field emission devices based on semiconductor fabrication processes.

All-solid state Li ion batteries are expected as one of next-generation rechargeable batteries since they have the potential to achieve high energy density and are free of risk of a flammable liquid electrolyte. The Li ion batteries cathodes, such as LiCoO 2 , change their volume during insertion or extraction of Li ions. Therefore, mechanical stress can be induced at the electrode/electrolyte interface. This mechanical stress can affect the thermodynamic and/or kinetic properties of electrodes and electrolytes. In this study, we aimed to understand the influence of the mechanical stress on Li chemical potential of LiCoO 2 . The variation of Li chemical potential in LiCoO 2 under mechanical stress was evaluated by electromotive force (emf) measurements. Positive emf was observed when the external mechanical stress was applied. This indicates that Li chemical potential in LiCoO 2 was changed by the mechanical stress. The relationship between Li chemical potential and the mechanical stress was discussed from thermodynamic point of view.

In solid-state ionic devices, such as all-solid-state lithium ion batteries (ASSLIBs) and solid oxide fuel cells (SOFCs), mechanical stress is introduced at the electrode/electrolyte hetrointerfaces due to differences in the crystal structures and the chemical/thermal expansion coefficients. A mechanical strain at the heterointerface might affect thermodynamic and kinetic properties of the electrodes and the electrolyte, resulting in the performance deterioration or improvement of the devices. Although such a so-called “mechano-electro-chemical coupling effect” has been empirically demonstrated by many researches, the origins of the effect are not fully understood so far. In this presentation, we will discuss the influence of mechanical stress on thermodynamic properties of solid-state ionic materials. As a model case, lithium chemical potential in electrode materials for ASSLIBs under mechanical stress was investigated. A dense thin film electrode of LiCoO2, Li2MnO4 or LiFePO4 was deposited on a plate of solid-state lithium ion conductors, and the variation of the lithium chemical potential in the electrode was evaluated by measuring electromotive force under compressively- and tensely-strained conditions. Electromotive force accompanied by mechanical strain could be clearly observed, demonstrating a “mechano-electro-chemical coupling effect”. The influence of mechanical stress was different depending on the kinds of electrode material. The observed change in the electromotive force could be thermodynamically related to the lithium partial molar volume of the electrodes.

In solid-state ionic devices, such as all-solid-state lithium ion batteries (LIBs) and solid oxide fuel cells (SOFCs), mechanical strain might be induced at the electrode/electrolyte hetrointerfaces during the cell fabrication process and the operation because of differences in the crystal structures and the chemical/thermal expansion coefficients. Such mechanical strain at the heterointerfaces might affect thermodynamic and kinetic properties of the electrodes and the electrolyte, resulting in deterioration or improvement of the devices’ performance. In this work, we investigated the influence of mechanical strain on lithium chemical potential in cathode materials for LIBs. Dense thin film electrodes, such as LiCoO2 and LiFePO4, were fabricated on a solid-state lithium ion conductor, such as Li0.29La0.57TiO3 (LLT) and Li7La3Zr2O12 (LLZ). The change in the lithium chemical potential in the electrode was evaluated by measuring electromotive force (EMF) between the electrode under compressively- or tensely-strained condition and one under stress-free condition. A clear EMF was generated when a mechanical strain was applied to the electrode. Typically, a positive and negative EMF was observed for a compressive and tensile stress, respectively. When the mechanical strain was released, EMF returned to zero. EMF seemed to increase proportionally with increasing the amount of mechanical strain. Such an EMF accompanied with the mechanical strain was discussed from thermodynamic points of view and, as results, could be related to the lithium partial molar volume of the electrode material. References [1] K. Funayama, T. Nakamura, N. Kuwata, J. Kawamura, T. Kawada, K. Amezawa, Electrochemistry, 83(10), 894-897 (2015). [2] K. Funayama, T. Nakamura, N. Kuwata, J. Kawamura, T. Kawada, K. Amezawa, Solid State Ionics, in press.

1. Introduction Recently, all-solid state Li ion batteries are widely investigated to establish more reliable and flexible battery systems [1, 2]. Compared to conventional batteries with liquid electrolytes, all-solid-state batteries can be suffered from undesired strains induced at hetrointerfaces between solids due to differences of crystal structures and chemical/thermal expansion coefficients. Such a strain may cause performance improvement/deterioration or failure of all-solid-state batteries. For example, it was reported that charge and discharge properties of an Al electrode is affected by the strain [3]. Therefore, it is important to understand the effect of strain on the electrochemical properties for the design and development of all-solid-state batteries. The purpose of this study is to reveal the effect of strain on electrochemical behaviors of cathode materials for all-solid-state Li batteries. For this aim, dense thin film LiCoO2 (LCO) electrodes were fabricated on an Li ion conducting glass ceramics (LICGC) by the PLD method, and the variation of the chemical potential of Li in the electrode due to external strain was evaluated by measuring electromotive force (EMF) between compressively and tensely strained LCO electrodes. 2. Experimental A schematic illustration of the specimen is shown in Fig.1. Dense thin film LCO electrodes were fabricated on both surfaces of an Li ion conducting glass ceramics LICGC (OHARA INC.) by the PLD method at 873 K with P(O2) of 20 Pa. Then, Al films as counter electrodes were also deposited next to the LCO electrodes by Ar ion sputtering at room temperature in Ar atmosphere of about 0.67 Pa. The Li contents of the LCO dense films were controlled by the electrochemical de-lithiation and estimated from the amount of the electricity passed through the cell. After the de-lithiation process, the Al electrode side was cut down. Two LCO electrodes were short circuited for about 24 hours to equilibrate the Li chemical potential. After the equilibration, the EMF between two LCO electrodes was measured with applying compressive and tensile strain to the upper and the lower LCO electrodes, respectively, by the four points bending method as shown in Fig.1. 3. Results and Discussion The obtained LCO electrode was oriented in the direction of (003) along the out of plane direction, i.e., the Li conductive plane was almost parallel to the substrate. Fig.2 shows the result of OCV measurements under different strain states. The EMF was generated when the strain was applied to the specimen. The compressively strained LCO electrode was negatively charged while the tensely strained LCO electrode was positively charged. The EMF emerged immediately after the application of the strain, was kept at an almost constant value while keeping the constant strain state, and became nearly zero after the release of the strain. The observed EMF value increased as the applied strain increased. Since the generation of EMF represents the difference of Li chemical potential between the compressively and tensely strained LCO electrodes, it is considered that the structural deformation due to the external strain induces the Li chemical potential variation. In the presentation, we will discuss the origin of the EMF from the thermodynamical points of views. References [1] V.A.Sethuraman, et al., J. Power Sources, 206 (2012) 334-342. [2] K.H. Kim, et al., J. Power Sources, 196 (2011) 764-767. [3] T. Ichitsubo, et al., J. Electrochem. Soc, 159(1) (2012) A14-A17.