bluuebunny/crossref_metadata_2025 huggingface dataset:
(Invited) Hydrogen-Related Trap States Induced during Fabrication Process and Annealing Effects in Amorphous in-Ga-Zn-O Thin Film Transistors
Authors: Ochi Mototaka , Hino Aya , Goto Hiroshi , Hayashi Kazushi , Kugimiya Toshihiro
Published: February 2020

Transparent amorphous oxide semiconductors (TAOSs) such as amorphous In-Ga-Zn-O (a-IGZO) are superior to the conventional semiconducting materials used in flat-panel displays (FPDs) because they have the advantages of high electron mobility, good uniformity, and a simple manufacturing process based on matured sputtering techniques [1]. To apply TAOS thin-film transistors (TFTs) to the mass production of next-generation displays, the stress stability during the a-IGZO TFT operation is a crucial issue that must be resolved.

It has been reported that the concentration of the hydrogen atoms in the a-IGZO is huge and the diffusion coefficient of hydrogen is two orders of magnitude larger than that of oxygen [2]. It means that hydrogen atoms easily diffuse into the channel region of the a-IGZO TFTs from hydrogen-containing layers such as a passivation layer (PV) during the fabrication. Hydrogen atoms also easily absorb to the channel region during the fabrication. Therefore, clarification of the effect of hydrogen on the electronic properties of the a-IGZO is particularly important to improve the TFT performance such as various stress stabilities against negative bias thermal illumination stress (NBTIS), negative bias thermal stress (NBTS) and positive bias thermal stress (PBTS).

The hump-shaped variation of the transfer curves under the NBTIS test was observed in both a-IGZO etch-stop layer (ESL)-type and back channel etch (BCE)-type TFTs. According to the results of photo-induced transient spectroscopy (PITS) analysis, it was observed that the density of hydrogen-related traps in the a-IGZO thin film was changed with the increase and/or decrease of hydrogen incorporated by the TFT manufacturing process [3, 4]. In this presentation, the impact of hydrogen-related trap levels on stress reliability with humps will be reviewed. Furthermore, the parallel-shaped variation of the transfer curves under the NBTS and PBTS test changed depending on the temperature of post-process annealing. It is believed that these behaviors are caused by interface defects due to dissociation and diffusion of hydrogen atoms at the interface [5, 6].

[1] K. Nomura, H. Ohta, A. Takagi, T. Kamiya, M. Hirano, and H. Hosono, Nature Vol. 432, pp. 488-492 (2004).

[2] K. Nomura, T. Kamiya, and H. Hosono, ECS J. Solid State Sci. Technol. Vol. 2, No. 1, pp. 5-8 (2013).

[3] K. Hayashi, M. Ochi, A. Hino, H. Tao, H. Goto, and T. Kugimiya, Jpn. J. Appl. Phys. 56, 03BB02 (2017).

[4] M. Ochi, A. Hino, H. Goto, K. Hayashi, and T. Kugimiya, ECS J. Solid State Sci. Technol. 6, P247 (2017).

[5] K. Hayashi, M. Ochi, A. Hino, H. Tao, H. Goto, and T. Kugimiya, Proc. IDW ’17, pp. 320-323 (2017).

[6] M. Ochi, A. Hino, H. Goto, K. Hayashi, and T. Kugimiya, Jpn. J. Appl. Phys. 57, 02CB06 (2018).

Figure 1
(Invited) High Performance Amorphous In-W-Zn-O Thin Film Transistor with Ultra-Thin Active Channel for Low Voltage Operation
Authors: Liu Po-Tsun , Kuo Po-Yi , Hsu Shan-Ming
Published: February 2020

Amorphous indium tungsten zinc oxide (a-IWZO) ultra-thin film TFTs (UTFTs) have been successfully fabricated and demonstrated in this work. Tungsten oxide (WO3)-doped indium zinc oxide was developed because WO3 doping can form stable semiconducting films with various carrier mobilities and carrier concentration. The novel IWZO UTFTs with high-κ HfO2 gate insulator exhibit superior potential for the power-saving applications of flat panel displays (FPDs), flexible electronics, and large scale integration (LSI) technologies, owing to its outstanding characteristics of low threshold voltage ~ -0.072 V, high mobility ~ 23.8 cm2/V-s, excellent subthreshold swing ~ 72.6 mV/dec., low voltage operation (low power consumption), high electrical reliability, and small hysteresis.
Integrated Taste Sensor Circuit with Oxide TFT
Authors: Han Ye Lin , Kang In Hye , Hwang Sang Ho , Baek Yeong Jo , Bae Byung Seong
Published: February 2020

Among the sensors that imitating the human five senses, the visual sensors are commercialized as CIS (CMOS Image Sensor) and CCD (Charge Coupled Device), and tactile sensor are partly commercialized as a touch sensor. Also, auditory sensor is commercialized as a microphone. However, the smell and taste sensors are still under development.

If the taste is sensed electrically, it is possible to obtain standard taste information. For portable applications a small size taste sensor system is required and a suitable technology for manufacturing such a highly sensitive small-sized sensor is semiconductor technology. Conventional taste sensors require a large amount of test material because they are large in volume. Also require expensive equipment and not suitable for portable device.

Various types of biosensors have been developed to overcome these drawbacks. The FET-type biosensor has advantages of miniaturization and standardization by integrating the sensor and the circuit by utilizing the integrated circuit manufacturing process. Among the devices capable of integrated circuits, thin film transistors with oxide semiconductor materials are one of the candidates having a simpler process than the LTPS TFT and a higher field effect mobility than the a-Si TFT.

Depending on the taste substances, the emitter current in the FET sensor changes. Each taste solution and lipid sensing membrane have different sensing principles. For example, a sourness, saltiness, or sweetness solution are electrochemical reactions in which specific ions are assembled near the lipid sensing membrane by electrical attraction, the bitterness solution is hydrophobic and certain molecules are absorbed by the lipid sensing membrane Hydrophobic binding. Those reactions induce potential changes of the floating gate and changes the current of the device.

As the concentration of the taste substances increases, the current of the transistor increases. And each solution has different values depending on the lipid sensing membrane. In this paper, an oxide transistor-based amplifier is designed for a taste sensor. We designed an amplifier that works well even when the size of the transistor changes and the threshold voltage changes.

Usually amplifier circuit require the optimum operation bias, which make the circuit complicated. However, in this paper we proposed a cascaded Class A amplifier which uses self-bias unit instead of voltage divider by resistors as shown in figure. In this circuit, T3 is a taste sensing transistor. Sensing signal is amplified by supply the alternation voltage through capacitor. The alternative way is to use T4 as a taste sensor. The amplification gains for different location of the sensor were compared.

Figure 1
Vertical Channel a-IGZO Thin Film Transistors Using Thin Gate Dielectric
Authors: Baek Yeong Jo , Hwang Sang Ho , Lee Sang Min , Han Ye Lin , Kang In Hye , Bae Byung Seong
Published: February 2020

Oxide thin film transistors (TFTs) are widely used as backplane for displays such as active matrix organic light emitting diode display and active matrix liquid crystal display. And also, it can be used in many applications such as sensor and wearable devices which require small power consumption. For low power consumption, the operation voltage should be decreased and the vertical structure TFT is a candidate due to short channel length. In this study, we proposed a vertical structure TFTs using a thin gate dielectric.

In this experiment, a vertical structure TFTs with a channel formed on the vertical sidewall of the gate electrode and a channel length controlled by the thickness of the gate electrode is proposed. The channel length was adjusted by the thickness of the gate electrode in the vertical TFTs developed in this paper. Figure 1 shows the fabricated vertical a-IGZO TFT developed in this study.

This vertical TFTs has the feature of controlling the channel length by the thickness of the gate electrode and can achieve short channel length easily, which is useful for low driving voltage. To reduce the gate voltage also, the thin gate dielectric was used. Since the very thin gate insulator was used, low threshold voltage was obtained, and low voltage driving was possible.

Figure 1
(Invited) Synthesis of Novel Two-Dimensional Nanomaterials for Device Applications
Authors: Zhang Hua
Published: February 2020

In this talk, I will summarize the recent research on synthesis, characterization and applications of two-dimensional nanomaterials in my group. I will introduce the synthesis and characterization of novel low-dimensional nanomaterials, such as graphene, transition metal dichalcogenide nanosheets and other 2D nanomaterials. Then I will demonstrate the applications of these novel 2D nanomaterials in chemical and bio-sensors, solar cells, hydrogen evolution reaction, electric devices, memory devices, conductive electrodes, etc.
(Invited) Realizing the Electro(photo)Chemical Behavior in Liquid Electrolyte through in-Situ Methodology
Authors: Chen Hao Ming
Published: February 2020

Metal oxide of spinel family has performed great potential toward oxygen evolution reaction (OER), but the fundamental mechanism of spinel oxides is still far from being completely understood especially for the role of metal ions. Owing to various coordinated sites of divalent/trivalent metals ions and surface condition (morphology and defects), it’s a great challenge to have a fair assessment of electrocatalytic performance of spinel system. Herein, we demonstrated a series of MFe2O4 (M = Fe, Co, Ni, Zn) family with a well-controlled morphology to achieve comprehensive study of electrocatalytic activity toward OER, in which most of the divalent metals (M2+) of MFe2O4 were located at octahedral sites. By utilizing several analyses, we could conclude a universal rule toward the spinel metal oxide for oxygen evolution. The activities for OER in spinel metal oxide system were determined by the occurrence of phase transformation rather than electronic state of metal ions, and this structural transformation could work well in both crystallographic sites (Td and Oh sites). Additionally, the divalent metal ion significantly dominated the formation of oxyhydroxide through an epitaxial relationship which depended on the atomic arrangement in the interface of spinel and metal oxyhydroxide, while trivalent metal ions were likely to be hosts lattices. The metal oxyhydroxide was formed during redox occurrence rather than OER, while the redox occurrence with remarkable increase in resistance and capacitance might result from the structural transformation from spinel to metal oxyhydroxide. We believed that the approaching strategies and information obtained in present study can offer a guide to design a promising electrocatalytic system toward oxygen evolution reaction and other fields.
Au@Cu2o Core@Shell Nanocrystals for Remarkable Hydrogen Production from Ammonia Borane
Authors: Fang Mei Jing
Published: February 2020

With the increasing crisis on energy shortage, hydrogen has been considered as a clean, alternative energy source to replace fossil fuels. As a versatile hydrogen storage material, ammonia borane (AB) has drawn much attention especially for its capacity of producing three-equivalent hydrogen in the presence of suitable catalysts. Here, we demonstrated the use of Au@Cu2O core@shell nanocrystals with hollow Au particles as core for remarkable catalytic hydrogen production from AB. The hollow Au may provide interior, confined space for stimulating molecular interaction. Moreover, upon protected by the Cu2O shell, each of the Au core can participate in the catalytic reactions, attaining a homogeneous reaction environment to facilitate the hydrogen production. Under visible light illumination, the catalytic activity of Au@Cu2O towards AB dehydrogenation can be further enhanced as a result of the photocatalysis capacity of Cu2O, proven to be a green and economical method of producing hydrogen.
Optical Properties of Transition Metal Dichalcogenide MoS2thin Films Synthesized By Atomic Layer Deposition
Authors: Zeng Min , Lin Pengtao , McCleese Christopher , Kolodziej Charles , Zhang Kai , Burda Clemens , Li Qiliang , Baumgart Helmut
Published: February 2020

Transition metal dichalcogenides (TMDCs), such as MoS2, WS2, WSe2 and MoSe2, exhibit a special structure in which a transition metal layer sandwiched between two chalcogen atomic layers. The in-plane covalent bonds between neighboring layer are strong and interplane van der Waals forces which keep the layer together are relatively weak. Especially, the monolayers commonly called as two-dimensional (2D) materials, are highly attractive due to their unique and tunable material properties. Therefore, the 2D TMDCs has promising potentials for the application of sensors, filed effect transistors, opto-electronics, piezoelectric devices, energy storage and hydrogen generation.

Recently, monolayer or few-layer TMDC films have been fabricated by many techniques, such as exfoliation, pulsed laser deposition (PLD), chemical vapor deposition (CVD). However, very little is known about atomic layer deposition (ALD) synthesis of 2D films and there are very only few references. ALD technique exhibits self-limiting atomic layer reactions in each introduced ALD cycle. ALD is the ability to control film thickness at angstrom level. Therefore, it offers better control of parameters like the composition, stoichiometry, uniformity and sharp interface. Furthermore, ALD also can be used to deposit conformal film onto very complex structures.

For this study MoS2 thin films have been prepared on silicon with native oxide and quartz substrates by Atomic Layer Deposition using Molybdenum hexacarbonyl (Mo(CO)6) and dimethyldisulfide (CH3SSCH3, DMDS) as the chemical ALD precursors for Molybdenum and Sulfur, respectively. For our experiments, 20 sccm N2 was used as a carrier gas flow for the precursors. This carrier gas flow enabled proper transport of precursors from the precursor cylinder to the reaction chamber. The growth temperature was set at 200, 230 and 250 oC. The chamber base pressure was kept at 40 mTorr. The crystallinity of as-deposited MoS2 thin film could be improved by post-annealing under saturated sulfur vapor. The Raman spectroscopy analysis show the MoS2 thin films the characteristic of E12g and A1g Raman modes. Multilayered MoS2 films were investigated with femtosecond laser pump-probe spectroscopy for the effects of increasing layer thickness on the electronic relaxation dynamics. It was found that the decay processes and valence band splitting are in accord with the known energy scheme for MoS2 thin films. A band gap of about 1.8 eV of MoS2 thin film is in the range of 1.1 eV (bulk MoS2) to 1.9 eV (monolayer MoS2). The band gap of ALD MoS2 thin films is much closer to the monolayer limit than the bulk limit.
(Invited) Probing Electrochemical Reactions Under Operando Condition
Authors: Liu Bin
Published: February 2020

Semiconductor-based nanomaterials have been widely studied as promising electrocatalysts for energy conversion and storage. Understanding the reaction pathways and active sites on electrocatalysts are of critical importance for the development of highly active electrocatalysts made of earth abundant elements. In this talk, I will give a detailed summary about our approach using various in-situ and ex-situ techniques including X-ray absorption, X-ray diffraction, X-ray photoemission spectroscopy, electrochemical impedance spectroscopy, Rama spectroscopy, etc to study electrochemical reactions.
Au@Cd1-Xznxse Yolk@Shell Nanocrystals: Interfacial Charge Dynamics and Photocatalytic Hydrogen Generation
Authors: WU Jhenyang
Published: February 2020

Combining semiconductor nanocrystals with metal particles has proven as a useful approach of improving the photocatalytic activity. On the other hand, yolk@shell nanocrystals with interior, void space can provide large surface area and homogeneous environment for reactant molecules, both of which are favorable for catalytic applications. In this work, Au@Cd1-xZnxSe yolk@shell nanocrystals with tunable compositions (x values) were prepared and used for photocatalytic hydrogen generation. The enhanced photocatalytic activity of Au@Cd1-xZnxSe was attributed to the pronounced charge separation induced by the Au yolk as well as the abundant active sites endowed by the yolk@shell structures. The interfacial charge dynamics were examined with time-resolved photoluminescence spectroscopy, which revealed the effectiveness of the optimal composition in achieving the most significant charge separation in concert with the highest photocatalytic activity.
(Invited) Carbon Nanotube Transistors for Flat Panel Display Application
Authors: Liang Xuelei , Zhao Jie , Huang Qi , Liu Fang
Published: February 2020

Carbon nanotubes are promising materials which can provide more functions at low cost for macroelectronics application, such as backplane electronics for display, flexible electronics, bio-chemical sensors, solar cells and others. Among these macroelectronics applications, carbon nanotube thin film transistors (CNT-TFTs) are expected to be used soon for backplanes electronics in flat panel displays (FPDs). This is due to the performance of CNT-TFTs surpasses the current commercialized TFT technologies, e.g., high mobility, high on/off ratio and high on-current surpass. Moreover, the fabrication process of CNT-TFTs is regarded facile, scalable, and compatible with the current TFT manufacturing process. Prototype AMOLED devices driven by CNT-TFTs have been demonstrated. However, most of the efforts on the application of CNT-TFTs for the backplane electronics are in research laboratories, and there are still many challenges before it is commercialized. In this presentation, we will report our progress on CNT-TFTs for FPD application, which includes the following aspects: high efficient fabrication of highly uniform carbon nanotube films on large area substrates (from 4 inch silicon wafers to 2.5th generation backplane glasses (370mm × 470mm)), manufacturing compatible fabrication process of CNT-TFTs, contact effect on the performance and scaling behavior of CNT-TFTs, hysteresis and ambipolarity suppression. Our results indicate practical application of CNT-TFTs in FPD products is expectable in a near future.
(Invited) Growing Large Diameter 4H SiC Boules – Furnace, PVT Growth and Characterization
Authors: Dhanaraj Govindhan , Motepally Kishore , Hemstad Stan , Rowland Larry
Published: February 2020

Silicon carbide (SiC) is a semiconductor material which is replacing and outperforming the conventionally used silicon crystal in power applications. The wide bandgap of SiC results in a low leakage current even at high temperatures. SiC single crystals are also becoming popular as Mossanite gem stones competing with diamond because of their excellent brilliance and other properties. However, at present, the production of large size and high quality 4H SiC single crystals is limited to a few industrial entities worldwide. The seeded physical vapor transport (PVT), commonly known as the modified Lely method, which exploits the sublimation at above 1800°C is the only proven method for the industrial production of SiC boules. However, fabrication of the PVT system for the growth of SiC is highly instrumentation oriented, and also due to its commercial importance, the know-how, and technical details are scarcely available in the literature. The complexity is due to the fact that the operating temperatures are extreme (2100–2500°C) and monitoring and controls are difficult. The growth process occurs in a nearly air-tight graphite crucible and it is not feasible to observe the growing boule or determine experimentally the exact thermal conditions in the growth zone due to high operating temperatures and the opacity of the graphite crucible. Seed mounting technologies are critical, and it is still kept as the industry secret. It is difficult to control the radial gradients when the diameter reaches close to 6 inches or beyond. With full modeling knowledge as well as outstanding expertise in equipment and the process technology, Aymont has developed precisely controllable SiC growth systems and process for growing large boule with independently controllable axial as well as radial gradients. The technical details on the design and fabrication of the SiC PVT system, hot zone, modeling, crystal growth and characterization results are presented.
(Invited) Towards Smart and Connected Point of Care Molecular Diagnostics
Authors: Liu Changchun
Published: February 2020

In the area of healthcare, an Internet of Medical Things (IoMT), i.e., interconnected, networked medical devices, will offer new avenues of diagnosis, personalized therapy, epidemiology, and healthcare services in a timely, sustainable, individualized, and cost-effective mode of delivery. Today, smartphone technology has a growing and pervasive influence on our daily life. Especially, with the rapid development of microfluidics technology, the incorporation of microfluidics technology with smartphone-based detection technology will create a new paradigm shift towards affordable, mobile, personalized, health monitoring. In this talk, I will introduce our superhydrophobic plasma separator, molecular diagnostic chip, smart connected cup (SCC) and their applications in disease diagnostics (i.e., HIV, ZIKV, HPV virus) at the point of care.
Origami Microfluidic CD
Authors: Aeinehvand MohammadMahdi , Sosa Silva Patricia , Bosques Palomo Beatriz , Valencia Velarde Flor Helena , Diaz Armas Gladys , Caballero Saldivar Eduardo , Madou Marc J , Martinez-Chapa Sergio Omar
Published: February 2020

Employing the centrifugal force for liquid displacement in bioanalytical compact discs (CDs) is becoming more popular for academic and industry applications. Pseudo forces that are controlled by a low-cost spindle motor enables the simultaneous manipulation of several liquids on the microfluidic CD. For this reason, centrifugal microfluidic platforms are considered more robust for extreme point of care (ePOC) applications when compared to stationary microfluidic systems that work with mechanical liquids pumps (e.g., syringe pump). However, the fabrication of microfluidic CDs requires expensive and bulky equipment (e.g., router or laser CNC) that cannot be implemented at ePOC and point of need (PON). To cope with this limitation, we have introduced a rapid microfluidic CD fabrication technique using only a low-cost cutter plotter [1]. The CDs were made through assembly of thin PVC and double-sided pressure sensitive adhesive (PSA) layers that were cut by the plotter machine. However, the technique yet required careful assembly of several disc layers, and the double-sided PSA is an expensive material and not widely available. In this article, we introduce a new origami CD fabrication process using only one type of material, a cutter plotter and a laminating machine. The origami CDs fabrication process prevents the need for PSA film and the tedious/sensitive CD assembly procedure. Therefore, the origami CDs facilitates onsite development of automated diagnosis test at ePOC and PON with minimum and widely available material and equipment. In addition to the origami CD fabrication process, this study includes the characterization of different microchannels made by the cutter plotter blade. Finally, as an application of the CD fabrication technique we developed an origami CD for automated serial dilution that is required for a wide range of bioanalytical applications such as microbial counting and multiplexed assay.

[1] M.M. Aeinehvand, P. Magaña, M.S. Aeinehvand, O. Aguilar, M.J. Madou, S.O. Martinez-Chapa, Ultra-rapid and low-cost fabrication of centrifugal microfluidic platforms with active mechanical valves, RSC Adv. 7 (2017) 55400–55407. doi:10.1039/C7RA11532F.
(Invited) From Circulating Tumor Cells to Fetal Nucleated Red Blood Cells
Authors: Zhao Xing-Zhong
Published: February 2020

Fetal nucleated red blood cells are special cells only existed in the peripheral blood of pregnat woman and fetus. This talk start from brief introduction of microfluidics development, then summarizing the basic principle and procedure used in the FDA approved porduct CellSearchTM and its subsequent developments in circulating tumor cells isolation, and followed by the research in our group on the capturing, analyzing of the circulating tumor cells from cancer patients and fetal nucleated red blood cells from the peripheral blood of pregnant women and their immunofluorescent assay.
Carbon Iso-Dielectric Separation (CIDS) on Centrifugal Microfluidic Platforms
Authors: Aeinehvand MohammadMahdi , Ramírez Sánchez Edgar , Cárdenas Benítez Braulio , Martínez-Chapa Sergio Omar
Published: February 2020

Centrifugal microfluidic platforms employ pseudo forces controlled by a spindle motor to automate bioanalytical assays on a single fluidic disc with no need for several syringe pumps [1]. Recently, we employed a portable cutter-plotter to fabricate microfluidic discs with active valves at point of need [2]. To address a healthcare issue of global interest, we developed a microfluidic disc to automate a sTREM-1 immunoassay for the detection of sepsis at late stages of the disease. To enable sepsis detection and monitoring at early stages, recently a gold iso-dielectric separation (GIDS) chip is develop that separates activated and non-activated leukocytes from blood serum [3]. However, the GIDS chip requires several syringe pumps and an off-chip manual step for sample preparation i.e., blood serum separation. As an alternative to GIDS, in this study we have developed 3D carbon IDS (CIDS) chips to reduce the cost of device fabrication. To prevent the need for the syringe pumps and external piping networks, we have integrated the CIDS on a microfluidic disc to automate the whole bioanalytical process from sample preparation to characterization of thousands of particles and cells. The main objective of developing the integrated microfluidic platform is the separation of activated and non-activated leukocytes for automated early sepsis detection at point of care (POC). However, as an early proof of the practicality of CIDS-on-disc, in this study we employed the hybrid centrifugal microfluidic system for separating various sizes of polystyrene microbeads as well as different bacteria.

[1] M.M. Aeinehvand, F. Ibrahim, S.W. Harun, A. Kazemzadeh, H.A. Rothan, R. Yusof, M. Madou, Reversible thermo-pneumatic valves on centrifugal microfluidic platforms, Lab Chip. 15 (2015) 3358–3369. doi:10.1039/C5LC00634A.

[2] M.M. Aeinehvand, P. Magaña, M.S. Aeinehvand, O. Aguilar, M.J. Madou, S.O. Martinez-Chapa, Ultra-rapid and low-cost fabrication of centrifugal microfluidic platforms with active mechanical valves, RSC Adv. 7 (2017) 55400–55407. doi:10.1039/C7RA11532F.

[3] J.L. Prieto, H.-W. Su, H.W. Hou, M.P. Vera, B.D. Levy, R.M. Baron, J. Han, J. Voldman, Monitoring sepsis using electrical cell profiling, Lab Chip. 16 (2016) 4333–4340. doi:10.1039/C6LC00940A.
(Invited) Materials Design of High-Energy Cation/Anion Redox in Li-Rich Cathode Materials: Li5FeO4, Li4Mn2O5, and Li2MO3
Authors: Wolverton Chris
Published: February 2020

The energy density of many lithium metal oxide battery cathodes is limited by redox reactions associated with the transition metal alone. Anionic redox reactions are affording new opportunities to increase this energy density. Here, we present results from first-principles density functional theory (DFT) calculations aimed at understanding the combined cation/anion redox of Li-rich materials, and designing new materials that will enable high-capacity, reversible cycling with minimal oxygen evolution. We illustrate this approach on three Li-rich compounds: Li5FeO4, Li4Mn2O5, and Li2MnO3.

Li5FeO4: Initial removal of Li is accompanied by Fe migration to form a disordered rocksalt structure. A local Li6-O coordination of oxygen, identified by DFT calculations, raises the O 2p band and enables reversible O-/O2- redox behavior, previously unknown in this material. This insight leads to the prediction and subsequent experimental demonstration of anionic and cationic redox reactions with good reversibility and without any obvious O2 gas release.

Li4Mn2O5: We study the recently-reported, high-capacity, disordered rocksalt-type Li4Mn2O5 compound and also determine the ground state ordered structure of Li4Mn2O5 via a DFT-based enumeration method. DFT calculations show that the delithiation process occurs via a three-step reaction pathway involving the complex interplay of cation and anion redox reactions: i) Mn3+ ➝ Mn4+ (LixMn2O5, 4 > x > 2), ii) O2− ➝ O1− (2 > x > 1), and iii) Mn4+ ➝ Mn5+ (1 > x > 0) concomitant with Mn migration from the original octahedral site to the adjacent tetrahedral site. Finally, we predict that alloying with M = V and Cr in Li4(Mn,M)2O5 would produce new stable compounds with substantially improved electrochemical properties.

Li2
MO3: We catalog the family of Li2
MO3 compounds as active cathodes or inactive stabilizing agents using high-throughput density functional theory (HT-DFT). With an exhaustive search based on design rules that include phase stability, cell potential, resistance to oxygen evolution, and metal migration, we predict a number of new Li2MIO3–Li2MIIO3 active/inactive electrode pairs, in which MI and MII are transition- or post-transition metal ions, that can be tested experimentally for high-energy-density lithium-ion batteries.
(Invited) High-Energy Lithium-Ion Battery Using Substituted LiCoPO4: From Coin Type to 1Ah Cell
Authors: Zaghib Karim , Liu Dongqiang , Zhu Wen , Kim Chisu , Cho M , Guerfi A , Delp S. a , Allen Jan L , Jow T Richard
Published: February 2020

There is a constant drive to improve the specific energy and energy density of the state-of-the-art lithium-ion battery. High energy is achieved by either choosing a cathode material that operates at a higher potential or has a higher specific capacity. Compared with conventional 4-V cathodes such as LiCoO2 (LCO), LiNi
x
Co
y
Al
z
O2 (NCA), LiMn2O4 (LMO) and 3.5-V LiFePO4 (LFP), LiCoPO4 (LCP) operates at 4.8 V (vs. Li/Li+) with a theoretic capacity of 167 mAh g-1. The higher voltage of LCP results in specific energy of ~800 Wh kg-1, which is about 25% higher than that of conventional cathodes in lithium-ion batteries. Although Co is more expensive than the other transition metals, the energy cost of LCP is expected to be less than other commercialized lithium-ion batteries on the market [1] due to the improved energy density. LCP suffers from severe capacity fade due to the low intrinsic electronic/ionic conductivity, structural deterioration and electrolyte decomposition [2, 3]. A diverse range of synthesis strategies, such as planetary milling, microwave heating and spray-pyrolysis et al, were explored to yield smaller particles and/or composites, but the above-mentioned shortcomings and the electrochemical performance remain unsatisfied [4-6]. Deposition of carbon coatings or precipitation of Co2P under high-temperature annealing in inert atmosphere produced a significant increase of over 105 in the electrical conductivity of LCP [7]. In addition, electrolyte additives were also employed to improve the attractiveness of LCP [8, 9]. These two approaches, however, do little to stabilize the cathode material itself, or only protect the electrolyte from decomposition during cycling. In this work, substitution of Cr, Fe and Si, as well as the use of a carbon-coating, improved the performance of LiCoPO4. The structural analyses and electrochemical properties are discussed. Cr, Fe and Si were added to improve the performance of olivine LiCoPO4 in cathodes for lithium-ion batteries. A substituted-LiCoPO4 in a half cell delivered a reversible capacity of 125 mAh/g at C/3 rate, with no capacity loss after over 100 cycles at 25 °C. The well-known capacity fade of LiCoPO4-based cathodes was almost completely eliminated by substituting Cr, Fe and Si. The electrochemical data of coin type battery and 1 Ah laminate cell will be shown.

Acknowledgments

Financial support from Hydro-Quebec and the US Army Research Lab is gratefully acknowledged.
High Voltage Olivines As High Energy Li-Ion Cathodes
Authors: Allen Jan L , Delp Samuel A , Wolfenstine Jeff , Jow T Richard
Published: February 2020

High voltage olivine structured cathodes offer the potential for high energy dense storage. LiCoPO4 (LCP) has a theoretical discharge capacity of 167 mAhg-1 at 4.8 V. Its adoption has been limited by poor cycling owing to both structural instability of the de-lithiated material and electrolyte instability at 5 V. LiNiPO4 (LNP) with a similar discharge capacity has a discharge voltage of 5.1 V for an even greater energy storage potential. We have shown that ion substitution is a powerful method to stabilize the cycling of the LCP high voltage electrode material in its charged, fully de-lithiated state. A low level of Fe substitution for Co increases the electrical and ionic conductivity and stabilizes the structure through change in the electronic structure which shift the redox activity toward Fe/Co and away from oxygen. Substitution of Cr for Co further increases the redox activity of Co leading to higher discharge capacity than for Fe-only substituted LCP. This stabilization mechanism is confirmed through spectroscopic measurements, through DFT calculation and is evidenced by extremely reduced discharge capacity fade during electrochemical cycling. Addition of Si to the cathode reduces the reactivity with the electrolyte as evidenced by an increase in the coulombic efficiency. LNP is even more challenging with extremely low electrical conductivity and an unfavorable electronic structure. We will discuss attempts to improve its performance. Electrolyte stability has been addressed through sacrificial additives, changes in solvent composition and surface modification of LCP. This paper will touch upon the most recent results in the development of a stabilized high voltage olivines with high energy and excellent cycle life and the development of supporting electrolytes.
Elucidating Singlet Oxygen Production in Li-Ion and Metal-Air Batteries
Authors: Houchins Gregory , Pande Vikram , Khetan Abhishek , Viswanathan Venkatasubramanian
Published: February 2020

At high voltages, Li-ion and Li-air batteries undergo unwanted electrochemical reactions that can permanently decrease the performance of the battery. Recent experiments studying off-gassing from NMC cathodes have yielded different results for the trends of O2, CO2, and CO gas production with varying Ni composition. Studies also disagree on the origin of the elements in the gas. Very recently, it was suggested that not only is Li2CO3 on NMC cathodes responsible for the majority of CO2 production [1] but that singlet oxygen is produced when Li2CO3 is bias above 3.82 V [2]. This and other studies suggest singlet oxygen production as a common degradation pathway in Li-ion, Li-air [3,4], and Na-air [5].

With the use of first principles methods, we attempt to reconcile these experimental works and propose a universal mechanism of singlet oxygen production. We will also discuss a way to experimentally verify our mechanism by varying the electrolyte, which we claim will change the onset potential of singlet oxygen production in a predictable way.

[1] 1. Renfrew, S. E. & McCloskey, B. D. Residual Lithium Carbonate Predominantly Accounts for First Cycle CO2and CO Outgassing of Li-Stoichiometric and Li-Rich Layered Transition-Metal Oxides. J. Am. Chem. Soc. (2017). doi:10.1021/jacs.7b08461

[2] 1. Mahne, N., Renfrew, S. E., McCloskey, B. D. & Freunberger, S. A. Electrochemical Oxidation of Lithium Carbonate Generates Singlet Oxygen. Angew. Chemie Int. Ed. (2018). doi:10.1002/anie.201802277

[3] 1. Mahne, N. et al. Singlet oxygen generation as a major cause for parasitic reactions during cycling of aprotic lithium-oxygen batteries. Nat. Energy (2017). doi:10.1038/nenergy.2017.36

[4] 1. Wandt, J., Jakes, P., Granwehr, J., Gasteiger, H. A. & Eichel, R.-A. Lithium–Air Batteries Singlet Oxygen Formationduring the Charging Process of an Aprotic Lithium–Oxygen Battery.

[5] 1. Schafzahl, L. et al. Singlet Oxygen during Cycling of the Aprotic Na-O2 Battery. Angew. Chemie Int. Ed. (2017). doi:10.1002/anie.201709351
Metal Oxide Nanomaterial Network for Lithium-Ion Battery Anodes and Cathodes
Authors: Luo Hongmei
Published: February 2020

Lithium-ion batteries have been investigated for their promising applications in hybrid electric vehicles. A great effort has been made to synthesize a variety of electrode materials to improve the energy density, rate capability, and cycling stability. Nanostructured materials have received much attention as anodes and cathodes due to the short ion transport length, higher electrolyte- electrode contact area and better accommodation of the strain of lithium insertion/extraction. Here we report a facile polymer-assisted chemical solution method to synthesize metal oxides nanoparticle network for lithium-ion battery anodes, such as cobalt oxide, nickel oxide, bismuth oxide, and cathode materials, such as vanadium oxide and lithium manganese oxide. The carbon left from the decomposition of polymers is an effective binder between metal oxides and the current collector. The one step binder-free anodes show much better lithium storage properties with high capacities, stable cyclability, and rate capability, as compared with the electrodes from the conventional slurry-paste way by mixing the active material, polymer binder and carbon black. The good performances of these electrodes could be attributed to intimate contact between the active material and the nickel foam, the porosity of the current collector, and the network structure of the active materials.
Energy Transfer in Surface Anchored Metal-Organic Thin Films
Authors: Haldar Ritesh
Published: February 2020

To achieve high efficiency energy harvesting system, long range diffusion, reduced non-radiative paths, and directional transport are the key parameters to control. Organic polymers and organic-inorganic hybrids with certain nanostructures perform well in regard to diffusion length and directionality; however those often lack mesoscopic order. Hence, further investigations on long-range ordered crystalline structures are essential to improve exciton diffusion length and directionality. Here, I would like to demonstrate surface anchored metal-organic frameworks (SURMOFs) as a potential candidate to address anisotropic energy transport feature. These surface grown thin films possess following advantages over powder crystalline MOF structures/organic ordered films: a) These are highly crystalline and oriented; b) can be grown on any transparent conductive surface; c) films thickness and roughness can be controlled in a straight forward fashion; and d) heterostructures with organic-organic interface can be constructed; e.g. MOF-on-MOF structures [1-2]. A suitably constructed SURMOF-2, made of 4,4′-(anthracene-9,10-diyl)dibenzoicacid (ADB) linkers showed existence of two excited states, a monomer-like PLMon and an excimer-like PLExc. Both the excited states are found to be mobile and their diffusion and related anisotropy are studied using steady-state and time-resolved fluorescence spectroscopy. Constructing two different type of acceptor doped heterostructures, it is shown that the low energy excimer state (PLExc) transports energy anisotropically along the stacking direction of the linker chromophores, as shown in the below schematic [3]. Such directionality of the exciton motion is introduced by the structural organization of the SURMOF-2.
(Invited) MOFs: From Ideal Insulators to Metals
Authors: Dinca Mircea
Published: February 2020

Traditional applications of metal-organic frameworks (MOFs) are focused on gas storage and separation, which take advantage of the inherent porosity and high surface area of these materials. The MOFs’ use in technologies that require charge transport have lagged behind, however, because MOFs are poor conductors of electricity. We show that design principles honed from decades of previous research in molecular conductors can be employed to produce MOFs with remarkable charge mobility and conductivity values that rival or surpass those of common organic semiconductors and even graphite, some even showing metallic character. We further show that these, ordered, and crystalline conductors can be used for a variety of applications in energy storage, electrocatalysis, electrochromics, and selective chemiresistive sensing.
Fabrication and Investigation of Crystalline Non-Porous Conductive Coordination Network Compounds
Authors: Hosseini Pouya , Brand Izabella , Wittstock Gunther , Lenk Thorben , Redel Engelbert
Published: February 2020

During the last years, surface-bound coordination network compounds (CNCs) have found application for sensing purposes (electrical, optical, and magnetic read-out), charge storage, electrochromic and optoelectronic layers, transparent coatings, bipolar switches, thermoelectric materials, catalytic, photocatalytic and light harvesting applications [1]. However, most of these applications require electrically conductive coordination network compounds (CCNCs). This requirement severely limits the choice of CNCs for the above-mentioned applications. Hexacyanometallates are coordinative networks with high electrical and ion conductivity that possess interesting redox properties and tuneable electrochemical redox transitions associated with clear colour changes [2].

We developed and characterized CCNCs such as copper hexacyanoferrate as thin crystalline films and characterized their optical, magnetic, electrical and dielectric properties. Thin films of these compounds were fabricated on gold and silicon oxide coated by self-assembled, cyanide-terminated monolayers using alternating immersion in their precursor solutions. Atomic force microscopy (AFM) confirms the formation of copper hexacyanoferrate with cubic structure on the gold surface (Fig. 1).

Fig. 1: AFM image of copper hexacyanoferrate film on a cyanide-terminated self-assembled monolayer on gold surface via layer-by-layer method.

X-ray diffraction (XRD) analysis confirmed the crystalline nature of the films. The thin films can be switched by exploiting the redox chemistry of the metal centres. The modulation of the electrical transport properties provides great potential benefits for numerous future applications in microelectronic device technologies. Structural and electronic changes of the films were probed by X-ray photoelectron spectroscopy (XPS) and polarization modulation infrared reflection absorption spectroscopy (PM IRRAS) before and after electrochemical oxidation and reduction [3]. Results demonstrate the possibility for electrochemical switching of the material properties for each compound but also indicates the complications in those transitions originating in the existence of different structures and defects in which (mobile) alkali metal cations may or may not reside in the pores and provide charge compensation.

Acknowledgement(s) Financial supports from DFG priority programme (SPP1928, Wi1617/24) is gratefully acknowledged.

References:

[1] J. Liu, W. Zhou, J. Liu, I. Howard, G. Kilibarda, S. Schlabach, D. Coupry, M. Addicoat, S. Yoneda and Y. Tsutsui, Angew. Chem. Int. Ed., 7441, 54 (2015).

[2] J. J. Alexander and H. B. Gray, J. Am. Chem. Soc., 4260, 90 (1968).

[3] P. Hosseini, G. Wittstock and I. Brand, J. Electroanal. Chem.,
199, 812 (2017).

Figure 1
The Role of Defects in the semiconducting-metallic discrepancy in Metal-Organic Graphene Analogues
Authors: Allendorf Mark D. , Foster Michael E. , Sohlberg Karl , Stavila Vitalie , He Yuping , So Monica C. , Talin A. Alec
Published: February 2020

The Metal-Organic Framework Ni3(2,3,6,7,10,11-hexaiminotriphenylene)2, also known as a “Metal-Organic Graphene Analogue,” or MOG, is a two-dimensional layered structure with a topology and extended π-conjugation analogous to graphene. Recent experimental results indicate that this material is semiconducting, as indicated by a non-zero band gap and conductivity that increases with temperature. Intriguingly however, several theoretical studies predict that the bulk material should be metallic. Characterization data suggest that the morphology of the MOG films used for conductivity measurements could play a role in the charge transport properties. In particular, samples used for electrical measurements, both films and pressed pellets, had complex nanocrystalline microstructures. We hypothesized that the tendency for internal interfaces to introduce transport barriers could be the source of the theory-experiment discrepancy. Here, we discuss DFT calculations we performed to probe the influence of internal interface defects on the electronic structure of bulk Ni3(HITP)2. The results show that interface defects can introduce a transport barrier by breaking the π-conjugation, and/or by decreasing the dispersion of the electronic bands near the Fermi level. Both defect types cause a small band gap to form (in the range of 15-200 meV), which is consistent with the experimentally inferred hopping barrier. These results provide strong evidence supporting the ongoing speculation that the charge transport properties of MOFs are strongly influenced by defects, in much the same way as conventional inorganic and organic conducting materials.
Density Measurement of Small Samples of Metal-Organic Frameworks Using Confocal Microscopy
Authors: Walheim Stefan , Redel Engelbert , Schimmel Th.
Published: February 2020

A novel approach for precise density measurement of small samples with a weight in the mg-range has been developed recently [1]. Using this approach, a solid object is dropped into a semi-confined cylindrical cavity, which is filled with a nonvolatile liquid. To determine the volume of the sample the rise of the liquid meniscus is measured with confocal microscopy. During the development of new MOFs, the lack of an appropriate amount of material makes it often impossible to determine the bulk density of the new material. Here we demonstrate how the density of small MOF samples can be determined by this novel method. Even with samples in the range of 1.5 mg we can measure the density with an accuracy better than 1%. The effect of previous sorption of other liquids and the distinction of open and closed porosity will be addressed.

1.: Bulk Density Measurements of Small Solid Objects Using Laser Confocal Microscopy. A. Kilmametov, R. Gröger, H. Hahn, Th. Schimmel and S. Walheim: Advanced Materials Technology 2017, 2, 1600115
SURMOF Based "Designer Solids" for Microelectronic Devices and Thermoelectric Materials Characterization
Authors: Hassan Zeinab Mohamed , Linseis Vincent , Reith Heiko , Baumgart Helmut , Redel Engelbert
Published: February 2020

SURMOF based "Designer Solids" and Organic thin film materials will be presented as non-volatile RRAM Devices. Additionally a fully thermoelectric characterization have been performed on ZT Test Cips (from Linseins Messgeraete GmbH). Thermoeletric Properties and Seebeck measurements of pristine and loaded SURMOF thin films will be presented.
(Invited) Conductive Metal Dithiolene MOFs for Electrocatalytic Applications
Authors: Marinescu Smaranda C
Published: February 2020

The development of efficient and inexpensive catalysts capable of solar-to-fuel energy conversion is vital for mitigating the adverse effects of carbon-based fuels on the environment and meeting the rising global energy demand. Heterogenization of molecular catalysts onto electrodes is an attractive strategy to combine the advantageous properties of homogeneous and heterogeneous catalysis. MOFs have emerged as a promising class of materials; however, their insulating nature has limited their application as electrocatalysts. We have demonstrated the successful integration of metal dithiolene units into one and two-dimensional frameworks by using dinucleating and trinucleating thiolate-based ligand scaffolds. The developed metal dithiolene frameworks display remarkable activity for the electrocatalytic conversion of water into hydrogen and electrical conductivity that is switchable from semiconducting to metallic. We expect the design principles discovered in these studies to have a profound impact towards the development of advanced materials and sustainable technologies.