bluuebunny/crossref_metadata_2025_split huggingface dataset:
Precipitation of Molybdenum Oxides in Supersaturated Zinc Oxide Thin Films
Authors: Chen Yijia J , Zhu Shen-how , Lin Tien-Chai 
Published: May 2020

Zinc oxide thin films saturated with molybdenum were prepared by RF magnetron sputtering process using zinc oxide and molybdenum targets for the co-sputtering. The sputtering power for zinc oxide was kept constant while that for molybdenum was varied from 0 watt to 35 watt. We found that the molybdenum-doped zinc oxide thin film change their color from transparent to grayish color as molybdenum sputtering power increases. The color change of the zinc oxide film suggests that the molybdenum changes its valance state as the molybdenum sputtering power was varied.
A surprising finding about the study is the electrical conductivity increases and then decreases with molybdenum sputtering power. The increase of electrical conductivity should be attributed to the increase of donor concentration as more molybdenum atoms are incorporated. The decrease of conductivity, on the other hand, is not so well reported. Hall measurement study shows that the conductivity decrease is caused by decreased electron concentration. However, the electron mobility increases steadily with increased molybdenum sputtering power even though the electron concentration decreases. This is an indication that the electrical conduction no longer occurs through the molybdenum-doped ZnO grains.
We propose that the conduction changes from grains to grain boundaries as molybdenum sputtering power increases. It means molybdenum is precipitated at the grain boundaries and forms conducting channels besides zinc oxide grains. The high mobility conduction channel is desired for devices using electron transport layers in their structures. The electrochemical solar cells are one of the devices that may benefit from the finding of molybdenum-doped oxide. We would like to present the valance change of molybdenum along with the conduction behavior, and would also like to predict the band alignment between zinc oxide and molybdenum oxide in the molybdenum-doped zinc oxide thin films. X-ray diffraction, UV-vis spectrophotometry, and x-ray photoelectron spectroscopy will be presented to show the conclusion that the electron mobility increase was attributed to the grain boundary conduction.
MOF-Templated Metal Oxides Sensitized with Quantum Dots Heterojunction for Efficient Solar Fuels Generation
Authors: Shi Li , Daniele Benetti , Li Faying , Wei Qin , Rosei Federico 
Published: May 2020

The separation and transport of photogenerated charges carriers are two of the most crucial factors that determine the overall efficiency of photoelectrochemical (PEC) systems. Various strategies have been exploited for achieving efficient charge separation and transfer. Among them, the design of semiconductor heterojunction has been shown to be one of the most effective approaches. Metal oxides, such as TiO2, are the among the most common materials for water splitting. However, the control of phase alignment and the interface structure remains a challenge. A promising solution is to use a template approach by employing metal-organic frameworks (MOF) which are of broad interest as a new class of organic-inorganic hybrid materials and have been intensely exploited in various fields due to their unique physical and chemical properties. Furthermore, common metal oxides, such TiO2 or NiO have limited absorption of sunlight due to their large intrinsic band gap (i.e. TiO2 anatase: 3.2 eV) which hinders effective use in solar water splitting. To extend the absorption range of the MOF-templated metal oxides in the visible and near-infrared range, we employed metal chalcogenide QDs as sensitizers.
In this presentation, for example, we explore a simple metal organic framework (MOF)-derived synthesis to obtain a controlled mixed-phase (anatase and rutile) of TiO2 nanoparticles, which retain the MOF crystal morphology. After sensitization with core@shell CdSe@CdS QDs, the mixed-phase TiO2 film exhibited a remarkable photocurrent of 10.72 mA/cm2 and long-term stability, with a retained value of more than 78.1% after two hours. Compared with commercial TiO2 films, the MOF-derived TiO2 film sensitized by core-shell CdSe@CdS QDs, showed an enhanced PEC device stability of +42.1% and PEC performance of +47.6%. The enhanced performance is due to the presence of mixed rutile/anatase phases, that creates a favorable band energy alignment for the separation of the photogenerated charges. The proposed photoanode based on MOF-derived metal oxide is an efficient strategy to improve the efficiency of the heterojunction-based PEC system for hydrogen generation. Furthermore, the combined use of QDs can extend the absorption range exploiting a larger part of the sun spectrum.

Figure 1
(Invited) Electrical Performance Improvement in 300mm Ge-Based Devices
Authors: Tapily Kandabara , Nakamura Genji , Consiglio Steven , Clark Robert D. , Newman Daniel , Triyoso Dina , Niimi Hiroaki , Wajda Cory S. , Leusink Gert J. 
Published: May 2020

As device feature size continues to scale, new device architecture and dielectric materials with engineered properties are becoming essential in overcoming the issues in scaled CMOS devices such as short channel effects. Some of the recent innovations device makers are exploring for better electrostatic control and improved performance are the introduction of new device architecture such as gate all around devices (nanowires/nanosheets), and channel engineering such as high mobility channel materials (Ge and III-V). Ge is particularly attractive for use as a channel material for P-type MOSFETs due to its high hole mobility and Si VLSI high volume manufacturing (HVM) compatibility. However, there are couple significant remaining challenges to integrating Ge into 300mm Si VLSI HVM which are a stable gate-stack formation and integration of Ge on Si (1-5). In this talk, advances in Ge gate stack engineering will be discussed. Using Si compatible technologies we have demonstrated scaled EOT by engineering both the interface and high-k formation.
Reference
1. S. Swaminathan, Y. Oshima, M. Kelly, P.C. McIntyre, Appl. Phys. Lett.,
95, 032907 (2009).
2. L. Zhang, M. Gunji, S. Thombare, P.C. McIntyre, IEEE Electr. Device. L., 34, 736 (2013).
3. C.H Lee, T. Nishimura, C. Lu, S. Kabuyanagi, A. Toriumi, IEDM, 32.5.1 (2014).
4. P. S. Goley, M. K. Hudait, Materials, 2301 (2014).
5. Q. Xie, S. Deng, M. Shaekers, D. Lin, M. Caymax, A. Delabie, X-P Qu, Y-L. Jiang, D. Dedytsche, C. Detavernier, Semicond. Sci. Technol. 074012 (2012)
Optimized SrVO3/Ag/SrVO3 Multilayers As High Transparency Electrodes for UV Optoelectronic Devices
Authors: Kim Su-Kyung , Seong Tae-Yeon 
Published: May 2020

GaN-based ultraviolet(UV) LEDs are important for their use in various applications such as space-to-space communications, curing, sterilization, etc. For these applications, the development of high-efficiency UV LEDs is needed. However, UV LEDs show relatively lower external quantum efficiencies than visible LEDs. To enhance the performance of UV optoelectronic devices by increasing light extraction, it is essential to develop p-type transparent conducting electrodes (TCEs) with high transparency in the UV region. Sn-doped indium oxide (ITO) is typical material for transparent conducting electrodes (TCEs) because of its low resistivity (< 10-4 Ω·cm) and high transmittance (> 85%) in the visible range. However, ITO has large light absorption below 400 nm wavelength and the poor electrical properties when it is thinner than 50 nm. Thus, there is a need for alternative TCEs that have high transmittance in the UV light region (200 – 400 nm). Extensive studies have been conducted to develop TCEs such as graphene, CNT, metal nanowire, and oxide/metal/oxide (OMO) multilayer. Among them, the OMO structure can be a good candidate for TCEs, because the mid-metal layer acts as a conduction path and the oxide layers can lead to zero reflection conditions.
In this study, we used SrVO3 films to develop UV-transparent multilayer and investigated their structural, optical, and electrical properties as functions of SrVO3 and Ag thickness by means of UV-VIS spectrometer, Hall-measurement, and transmission electron microscopy. Unlike ITO film, SrVO3 films exhibited high transmittance (> 80%) up to 320 nm. It was shown that the SrVO3 film showed larger optical bandgap (4.3 eV) than that of ITO (3.7 eV). For the OMO structures with Ag thickness of 15 nm, the sheet resistance was in the range 2.76 – 3.15 Ω/sq, depending on the SrVO3 thickness. In particular, SrVO3 (25 nm)/Ag (15 nm)/SrVO3 (25 nm) sample exhibited the highest Haacke’s figure of merit (FOM) of 144.5 x 10-3 Ω-1 where the average transmittance of the OMO was 91.5% over the 360 – 400 nm wavelength. For the 25 nm-thick SrVO3-based OMO films, the transmittance and sheet resistance gradually decreased with increasing Ag thickness from 9 nm to 21 nm. For example, the sheet resistance of SrVO3/Ag/SrVO3 samples was in the range 1.97 – 6.48 Ω/sq and the transmittance varied from 82.6 to 95.5%. Among these samples, SrVO3/Ag (15 nm)/SVO sample showed the highest FOM value. Rigorous coupled-wave analysis (RCWA) simulations were performed to understand the measured transmittance behavior and zero reflection condition in the SrVO3/Ag/SrVO3 structure. These results imply that SrVO3-based OMO structure could be a potentially important TCEs for the fabrication of high-efficiency UV optoelectronic devices.
Mechanism of Reverse Leakage Current in Schottky Diode Fabricated on Large Bandgap Semiconductors like Ga2O3 or Diamond
Authors: Lau Wai Shing 
Published: May 2020

The bandgap of Ga2O3 (4.5-4.9 eV) is larger than the bandgap of GaN (3.4 eV). In addition, single crystal bulk Ga2O3 wafers can be more easily manufactured than GaN wafers. Therefore, Ga2O3 has strong potential for applications in high power semiconductor devices [1]. Schottky diodes fabricated on n-type Ga2O3 have strong potential as fast high-power switching devices. Similarly, the bandgap of diamond (5.5 eV) is very large and diamond Schottky diodes have good potential.
For example, Harada et al. published their work on Schottky diodes fabricated on n-type Ga2O3 with PdCoO2 as the metal [2]. They claimed that their Schottky diodes have a very large Schottky barrier height of 1.8 eV. Other scientists using metals like W, Au, Ir, Pd or Pt cannot achieve such a large value of the Schottky barrier height. However, they did not propose any physical mechanism regarding the reverse leakage current in their Schottky diodes. One possible mechanism of reverse leakage current in Schottky diodes fabricated on n-type Ga2O3 is image force barrier lowering at the metal-Ga2O3 interface. Historically, there were 2 theories regarding the image force barrier lowering effect. In 1953, Krömer published his theory that the image force dielectric constant in the equation for Schottky emission should be equal to 1 [3]. Subsequently in 1964, Sze et al. published their theory that the image force dielectric constant in the equation for Schottky emission should be equal to n2 [4], where n is the refractive index of the semiconductor in the infrared or visible light range. The theory of Sze et al. quickly became the dominating theory whereas Krömer’s theory essentially became a forgotten theory. For Ga2O3, n is approximately equal to 2 [5] and so n2 is about 4. The author performed an analysis on the experimental data published by Harada et al. [2] and found that Krömer’s theory fit the experimental data from Harada et al. much better than the theory of Sze et al. Similarly, the author noticed that Krömer’s theory is better than the theory of Sze et al. for diamond Schottky diodes.
In conclusion, the author pointed out that it is necessary to resurrect an old and forgotten theory from Krömer in order to explain the experimental data on the reverse leakage current of Schottky diodes fabricated on large bandgap semiconductors like Ga2O3 and diamond.
References
[1] M. Higashiwaki, H. Murakami, Y. Kumagai and A. Kuramata, Jpn. J. Appl. Phys., 55, 1202A1 (2016).
[2] T. Harada, S. Ito and A. Tsukazaki, Sci. Adv., 5, eaax5733 (2019).
[3] H. Krömer, Zeitschrift fur Physik, 134, 435 (1953).
[4] S.M. Sze, C.R. Crowell and D. Kahng, J. Appl. Phys., 35, 2534 (1964).
[5] T. Onuma, S. Saito, K. Sasaki, T. Matsui, T. Yamaguchi, T. Honda, A. Kuramata and M. Higashiwaki, Jpn. J. Appl. Phys., 55, 1202B2 (2016).
Inkjet Printing for Producing Li-Ion Secondary Batteries
Authors: Nakajima Satoshi , Kuriyama Hiromichi , Tanteitanton Porapon , Sagisaka Toshiya , Takeuchi Shigeo , Kanno Yusuke , Yanagita Hideo , Suzuki Eiko , Ushirogochi Toru 
Published: May 2020

Recently, emerging devices such as IoT (internet of things) sensors and wearable devices require lithium-ion batteries (LIBs) with flexibility, various forms in terms of shape and size, and high power density. As required of these points, we have developed a new approach to producing free-designed cathodes and anodes for LIBs using inkjet printing.
In this study, we mobilized all our accumulated technological expertise, including ceramic particle grinding technology and high dispersion technology to develop a new printable dispersion liquid for electrode materials. Most types of cathode and anode materials have been successfully used to demonstrate high concentration and low viscosity dispersion liquid for an inkjet printing with high productivity.
The thickness of an inkjet printed electrode can be controlled by the number of droplets landed on the current collector. Because of the digital tuning of the thickness, we can obtain a thinner electrode with high-power density than the one fabricated by the conventional coating methods.
In order to demonstrate the high-power usage of inkjet-printed electrodes, we fabricated a “R”-shaped prototype cell with capacity of 3mAh using common ceramic-type cathode and anode materials. As a result of the low impedance of inkjet-printed electrodes, the prototype cell can operate over 30C rate. This prototype cell had enough power to send data collected on temperature and humidity every five seconds via Bluetooth to a computer.
On the Importance of Incorporating Structural Heterogeneity of Porous Electrodes in LI-ION Battery Models: Pore Network Modelling a Way to MOVE Forward
Authors: Khan Zohaib Atiq , Gostick Jeff T. 
Published: May 2020

Image processing of 3D tomographic images to extract structural information of porous materials has become extremely important in porous media research with the commoditization of x-ray tomography equipment to the lab scale. Extracted pore networks from image analysis techniques enable transport properties calculation for bigger domains at a very low computational cost, allowing substantial investigation of porous media. Consequently, they are being increasingly used to model Multiphysics transport processes in various energy storage devices like fuel cells and batteries, where the geometrical structure plays a vital role in electrochemical performance, but true pore-scale modeling is computationally infeasible.
Traditionally, pore network modelling has been used to find electrochemical performance of Li Ion batteries by investigating pore phase interconnectivity in carbon electrodes. The actual lithium ion electrode, however, consists of active material, carbon binder and electrolyte filled pore phase. The interconnectivity of these phases influences the effective transport properties and hence electrochemical performance of cathode material. The presence of carbon binder phase not only reduces the SEI layer between active material and electrolyte phase but also influences tortuosity and effective electronic conductivity in the pore and solid phase respectively. The present work uses a pore network modelling frame work to investigate the effect of carbon binder phase on Lithium Ion battery cathode. We used actual three phase, X-ray tomography image of NMC-811 cathode material and studied its electrochemical performance with and without binder phase. Unlike previous models which compensate the importance of carbon binder as electrical conductor by assuming high electronic conductivity of active material, this study considers actual values of conductivities in all phases. Moreover, the impact of nanoporosity in the carbon binder phase was also explored and found to enhance the reaction rate compared to solid binder. The reduction in computational time achieved using the pore-network approach was so significant that adding additional physics and transient conditions could conceivably be included to increase the accuracy of the model, thereby providing more realistic simulations and point to the true limiting processes. The developed pore network model opens a new avenue for modelling complex electrochemical systems with less computational cost, enabling simulation of bigger electrode domains while keeping structural heterogeneities of material.
Study on the ‘Shape Change’ of Rechargeable Zinc Electrodes in Alkaline Electrolytes
Authors: Nakata Akiyoshi , Morita Masayuki , Ogumi Zempachi , Abe Takeshi 
Published: May 2020

Zinc, the most historical material for battery application, is one of the candidates for the high capacity electrodes of the next-generation secondary batteries, and has been applied in Zn/Air, Zn/NiOOH. These zinc-based batteries commonly employ aqueous alkaline electrolytes that have some advantages such as high ionic conductivity for high rate capability and non-flammability for high safety, which are particularly attractive for the mobile and EV applications. However, their insufficient cycle life due to the deterioration modes such as zinc dendrite formation, densification and shape change, has limited the widespread use of the zinc-based secondary batteries. In particular, the shape change is known to be a serious problem, in which the active material is gradually lost at the edge and agglomerates in the center of the electrode in the course of cycling, resulting in the capacity fade.
For suppressing this undesirable redistribution of the zinc electrode, it is essential to clarify the growth mechanism of the shape change phenomenon. So far the growth mechanism has been studied and analyzed, especially in the view point of the reaction (current) distribution, by various methods such as direct visual observation, tracing radioisotope, monitoring current distribution with the use of divided electrode, and calculating mathematical model. As the shape change proceeds dynamically with charging-discharging cycles causing electrode composition changes, the detailed observation of the composition change of zinc species during the cycling offer fruitful information on the reaction distribution to understand the growth mechanism of the shape change precisely and key to improve it. In this study, we evaluate the distribution of zinc species in Zn/NiOOH cells to elucidate the way the shape change occurs in the course of cell cycling.
References:
[1] A. Nakata
,
H. Arai
,
H. Murayama
,
K. Fukuda
,
T. Yamane
,
T. Hirai
,
Y. Uchimoto
,
J. i. Yamaki
, and Z. Ogumi,APL Materials 6, 047703 (2018); https://doi.org/10.1063/1.5011272.
Li2TiS3: Lithium Metal Sulphide Rocksalt As New Cathode Material for High Energy Batteries without Critical Materials
Authors: Peralta David , Celasun Yagmur , Benayad Anass , Colin Jean-Francois , Haon Cédric , Herlin Nathalie , Martinet Sebastien , Bloch Didier , Patoux Sebastien 
Published: May 2020

Most of the current Li-Ion cathodes use cobalt/nickel-based layered oxides as active materials. Due to the increasing demand of these critical and scarce elements in the coming years, it becomes urgent to develop new materials based on abundant elements. In 2014, Sakuda et al. introduce new sulphide rocksalt materials which can deliver a capacity higher than 400 mAh/g at 2.2 Volts.1

In 2019, a project named Spider funded by the European Union's Horizon 2020 research and innovation programme started with the objective to develop and use these materials in Li-Ion batteries. Several synthesis methods have been evaluated to produce Li2TiS3 materials. High capacities are obtained with these materials but they suffer from a poor cycle life.
Several characterizations and experiments have been performed in order to obtain a better understanding of the material evolution during cycling. Ex-situ XRD are in good agreement with previous results reported by Sakuda et al. and we completed the investigation thanks to Ex-situ SEM and XPS characterizations.2 We highlight that the material is partially oxidized during the cathode manufacturing process which lead to a loss of the lithium content in the materials structure. Our conclusions will be helpful to overcome these issues.
References
(1) Sakuda, A.; Takeuchi, T.; Okamura, K.; Kobayashi, H.; Sakaebe, H.; Tatsumi, K.; Ogumi, Z. Rock-Salt-Type Lithium Metal Sulphides as Novel Positive-Electrode Materials. Sci. Rep.
2014, 4, 4883. https://doi.org/10.1038/srep04883.
(2) Sakuda, A.; Ohara, K.; Kawaguchi, T.; Fukuda, K.; Nakanishi, K.; Arai, H.; Uchimoto, Y.; Ohta, T.; Matsubara, E.; Ogumi, Z.; et al. A Reversible Rocksalt to Amorphous Phase Transition Involving Anion Redox. Sci. Rep.
2018, 8 (1), 1–6. https://doi.org/10.1038/s41598-018-33518-4.

Figure 1
The Effect of 2,2,6,6-Tetramethylpiperidinyl-Oxide (TEMPO) As an Electrolyte Additive and Its SEI Formation on Mcmb-Electrode
Authors: Lin Shawn D. , Yohannes Yonas Beyene , Hwang Bing-Joe 
Published: May 2020

The stable radical molecule, 2,2,6,6-tetramethylpiperidinyl-oxide which is commonly known as TEMPO, is well known for its unusual stability as a neutral radical. (1, 2) The use of TEMPO and its derivatives have been examined in secondary batteries, since the year 2000. It is mainly used to enhance cycling performance, as a fire retardant, or as an additive in lithium sulfur batteries. (3) The TEMPO molecules are also used as liquid electrolyte. (4) It can also be used as redox shuttles in lithium-ion batteries. (5) In terms of the protection offered for a length of overcharge, TEMPO molecules are among the best shuttle molecules. (3-5) Recently, Dagger et al. (6) investigated an electrolyte combinations including both flame retardant (FRs) and film forming additives (FFAs) in order to generate synergetic effects and create electrolytes with enhancement in safety and electrochemical performance. The synergy of the FR and FFAs gives an effective SEI, diminishing the electrolyte ageing effect and also elevation of the life-time of the cycled cells at elevated C-rates. Incorporation of 2% TEMPO as an additive into STD + 5% FEC electrolyte results in a modification of the MCMB-electrode SEI. The direct in-situ DRIFTS analysis of the electrolyte additive; TEMPO, give a substantial insight into the nature SEI-formation of the negative electrode. The beneficial effect from the TEMPO additive might be the suppression of the solvent/additive decomposition by quenching the radicals formed. The positive effect of TEMPO was explained by the formation of polymeric species like, poly (VC), polycarbonate and also ROCOOLi, Li2CO3 and alkyl phosphorous fluorides. The studies described herein demonstrate that MCMB-electrodes in STD + 5% FEC solution containing TEMPO additive can be utilized together with high voltage cathode. The CV and in-situ DRIFTS for the electrolyte contribution with TEMPO additive is shown in Fig. 1. The possible reaction mechanism with the presence of TEMPO additive is discussed.
Fig. 1. CV (left) and in-situ DRIFTS (right) recorded on MCMB-electrode of the electrolyte containing STD+5%FEC+2%TEMPO.

References

1. J. T. Weil, J. Van der Veen and H. Olcott, Nature, 219, 168 (1968).
2. M. Taggougui, B. Carré, P. Willmann and D. Lemordant, J. Power Sources, 174, 643 (2007).
3. C. Buhrmester, L. Moshurchak, R. Wang and J. Dahn, J. Electrochem. Soc., 153, A1800 (2006).
4. L. M. Moshurchak, C. Buhrmester, R. L. Wang and J. R. Dahn, Electrochim. Acta, 52, 3779 (2007).
5. C. Buhrmester, L. Moshurchak, R. L. Wang and J. Dahn, J. Electrochem. Soc., 153, A288 (2006).
6. T. Dagger, M. Grützke, M. Reichert, J. Haetge, S. Nowak, M. Winter and F. M. Schappacher, J.Power Sources, 372, 276 (2017).

Figure 1