There is, I think, something ethereal about i —the square root of minus one. I remember first hearing about it at school. It seemed an odd beast at that time—an intruder hovering on the edge of reality.

Usually familiarity dulls this sense of the bizarre, but in the case of i it was the reverse: over the years the sense of its surreal nature intensified. It seemed that it was impossible to write mathematics that described the real world in …

I and i

Solid-state electrolytes are attracting increasing interest for electrochemical energy storage technologies. In this Review, we provide a background overview and discuss the state of the art, ion-transport mechanisms and fundamental properties of solid-state electrolyte materials of interest for energy storage applications. We focus on recent advances in various classes of battery chemistries and systems that are enabled by solid electrolytes, including all-solid-state lithium-ion batteries and emerging solid-electrolyte lithium batteries that feature cathodes with liquid or gaseous active materials (for example, lithium–air, lithium–sulfur and lithium–bromine systems). A low-cost, safe, aqueous electrochemical energy storage concept with a ‘mediator-ion’ solid electrolyte is also discussed. Advanced battery systems based on solid electrolytes would revitalize the rechargeable battery field because of their safety, excellent stability, long cycle lives and low cost. However, great effort will be needed to implement solid-electrolyte batteries as viable energy storage systems. In this context, we discuss the main issues that must be addressed, such as achieving acceptable ionic conductivity, electrochemical stability and mechanical properties of the solid electrolytes, as well as a compatible electrolyte/electrode interface. This Review details recent advances in battery chemistries and systems enabled by solid electrolytes, including all-solid-state lithium-ion, lithium–air, lithium–sulfur and lithium–bromine batteries, as well as an aqueous battery concept with a mediator-ion solid electrolyte.

Lithium battery chemistries enabled by solid-state electrolytes

The science and technology of ultracapacitors are reviewed for a number of electrode materials, including carbon, mixed metal oxides, and conducting polymers. More work has been done using microporous carbons than with the other materials and most of the commercially available devices use carbon electrodes and an organic electrolytes. The energy density of these devices is 3¯5 Wh/kg with a power density of 300¯500 W/kg for high efficiency (90¯95%) charge/discharges. Projections of future developments using carbon indicate that energy densities of 10 Wh/kg or higher are likely with power densities of 1¯2 kW/kg. A key problem in the fabrication of these advanced devices is the bonding of the thin electrodes to a current collector such the contact resistance is less than 0.1 cm2. Special attention is given in the paper to comparing the power density characteristics of ultracapacitors and batteries. The comparisons should be made at the same charge/discharge efficiency.

Ultracapacitors: Why, How, and Where is the Technology

羟氨苄青霉素引起大疱性类天疱疮样疹

Note: Times Cited: 875 Reference EPFL-ARTICLE-206025doi:10.1021/cr0501846View record in Web of Science URL: ://WOS:000249839900009 Record created on 2015-03-03, modified on 2017-05-12

Complex Hydrides for Hydrogen Storage

A 1.5- μm polycrystalline diamond was deposited on the AlGaN/GaN heterojunction on the SiC substrate with a 20-nm SiN dielectric. A 4.9% increase in 2DEG density after the diamond growth due to the increase in tensile strain of the GaN layer is confirmed by micro-Raman measurements. The interfacial analysis through the transmission electron microscopy and electron energy loss spectroscopy shows a thickness reduction in the SiN layer of ∼1.7 nm, which converts to a thin SiC layer at the diamond/SiN interface, and no carbon diffusion is found in the SiN layer after the diamond growth. Device simulation using the thermal properties extracted by time domain thermoreflectance predicts a temperature drop of 17.1 °C when the diamond only covers the device access region and reveals that the improvement of thermal boundary resistance is much more effective than that of the diamond thermal conductivity for the top-side heat spreading, which is mainly due to the limited thickness of the top diamond film.

Structural and thermal analysis of polycrystalline diamond thin film grown on GaN-on-SiC with an interlayer of 20 nm PECVD-SiN

The electron traps in HfO2 are a major concern of the reliability of metal-oxide-semiconductor field effect transistors (MOSFETs) beyond the 30 nm technology generation. In this work, the principle of the discharge-based pulse I–V technique is demonstrated in detail. By using this technique, the thorough energy distribution of electron traps across the 4 nm HfO2 layer is identified, which overcomes the shortcomings of the current techniques. It is observed that there are two peaks in HfO2. The large peak is at around 1.0 eV below the HfO2 conduction band bottom. The small peak is at about 1.43 eV below the HfO2 conduction band bottom. The results provide valuable information for theoretical modeling establishment, fast material assessment and process optimization for MOSFETs with high-k gate dielectrics.

Electron Trap Energy Distribution in HfO 2 by the Discharge-Based Pulse I – V Technique

A systematic study of device structure on DC and small‐signal characteristics of millimeter‐wave AlGaN/GaN HEMT

This work presents the temperature-dependent characteristics of the thin-barrier Al0.45Ga0.55N/GaN high electron mobility transistor (HEMT), p-type CuO gate HEMT, and high-k HfO2 metal–insulator–semiconductor HEMT (MIS-HEMT). As the temperature rises from 20 to 300 °C, the maximum trans-conductance of the HfO2 MIS-HEMT and CuO gate HEMT reduces by 56.9% and 43.2%, respectively. The sub-threshold swing of the CuO gate HEMT is smaller than that of the HfO2 device when the temperature reaches 300 °C. According to the C–V test results from 20 to 300 °C, the relative dielectric constant of CuO increases from 18.1 to 47.4, whereas HfO2 has a relatively stable dielectric constant. The calculation models are presented to investigate the effect of the dielectric constant on the drain current and the trans-conductance. The calculated results show that the maximum transconductance of the HfO2 MIS-HEMT and CuO gate HEMT decreases by 52.3% and 38.9%, respectively, which is in good agreement with the experimental results.

Temperature-dependent characteristics for the p-type CuO gate HEMT and high-k HfO2 MIS-HEMT on the Si substrates

In this paper, we have investigated the mechanism of breakdown enhancement in AlGaN/GaN HEMTs using a high-k passivation layer. A group of depletion capacitance models are proposed to investigate the breakdown enhancement of the high-k passivation layer. With a passivation layer, the drain-side wall and top of the gate metal would form metal-insulator-semiconductor contacts with GaN-based heterojunction, which is the reason for the modulation of the high-k passivation layer on electric field.

https://ieeexplore.ieee.org/iel7/7580918/7589250/07589349.pdf

Xiaohua Ma

Papers

Structural and thermal analysis of polycrystalline diamond thin film grown on GaN-on-SiC with an interlayer of 20 nm PECVD-SiN

Electron Trap Energy Distribution in HfO 2 by the Discharge-Based Pulse I – V Technique

A systematic study of device structure on DC and small‐signal characteristics of millimeter‐wave AlGaN/GaN HEMT

Temperature-dependent characteristics for the p-type CuO gate HEMT and high-k HfO2 MIS-HEMT on the Si substrates

Mechanism of breakdown enhancement in AlGaN/GaN HEMTs using a high-k passivation layer