bluuebunny/crossref_metadata_2025 huggingface dataset:
Surface Modification Strategies of High Capacity Anodes Towards Exceptional Robust Cycling
Authors: Ma Yue
Published: February 2020

Pulverization of electrode materials and loss of electrical contact have been identified as the main causes for the performance deterioration of alloy anodes. In this talk, we describe the hierarchical arrangement of spatially confining silicon nanocrystals within several different physical insulting capsules for alleviating these issues. Firstly, an elastic, highly oriented graphene monolith was engineered to fully encapsulate the silicon nanoparticles, serving as a robust framework with the well-accessible thoroughfares for electrolyte percolation, as well as an electrolyte blocking layer to restrain Si from direct exposure to electrolyte without sacrificing the high-efficiency electron/Li ion transport channels; in return, the pillar effect of Si NPs prevents the graphene sheets from re-stacking. Secondly, we also attempted to develop a F-doped TiO2-x layer on the silicon surface with additional possibility of the in-situ etching of the native oxide layer into a hollow interior. When evaluated as binder-free anodes, both type of the electrodes exhibit a remarkable cycle life for more than 1000 cycles with average coulombic efficiency higher than 99.5%. Operando XRD and synchrotron-based XPS confirmed the formation of the most volume expanded lithiated phase Li15Si4, suggesting the effective buffering of the volume variation upon cycling. Furthermore, we also develop a GF/Si free-standing film through re-adjusting the pore size in GF/Si monolith. Thanks to electrical conductivity, the elasticity and structural integrity of GF monoliths, the as-developed GF/Si free-standing film showcases the potential use in the flexible electronic devices.
Laser Pyrolysed N-Doped SnOx Nanoparticles with Enhanced Conductivity and Stability As Anode in Li-Ion Batteries
Authors: Wang Luyuan Paul , Zhao Yi , Wei Chao , Leconte Yann , Srinivasan Madhavi , Xu ZhiChuan, Jason
Published: February 2020

A novel one-step laser induced pyrolysis method was utilized for the synthesis of pristine SnO2 and p-type conduction N-doped SnOx nanoparticles. Most reports on doping of SnO2 focuses on subtition of Sn with other metallic, while replacement of O is uncommon due to difficulty in synthesis. In particular, laser pyrolysis made the synthesis of N-doped SnO2 possible by the high thermal gradient between the reaction zone and chamber wall to limit particle growth, as well as a brief contact of N atoms and SnO2 under extermely high temperature. The presence of N atoms during the rapid synthesis process substitutes the O2- anion and is hypothesized to improve conductivity of the material. The sample with 3% of N-doping exhibited optimum performance, with high initial and reversible capacities of 1899 and 1241 mAh g-1 respectively. Even when tested at a current density of 10 A g-1, SnO2+N3% can deliver a specific capacity as high as 522 mAh g-1. Moreover, a capacity of 1192 mAh g-1 can be retained at end of the 500th cycle. The cyclability and rate performance of the carbon free SnO2 nanoparticles are by far one of the best reported thus far. Interestingly, SnO2+N8% demonstrated the worst rate capability, which indicates that there could be an optimum doping concentration. The superior performance in SnO2+N3% could be credited to the presence of hole donating N atoms directly situated within the structure of SnO2 and the small particle sizes which permits rapid ion diffusion while preventing pulverization and agglomeration. Ex-situ TEM and XAS will be utilized to further understand correlation between structural properties with enhancement in performance.

Figure 1
Solution Combustion Synthesis of Transition Metal Oxide-Carbon Composite for Li Ion Battery Anode
Authors: Zhu Chunyu , Aoki Yoshitaka , Habazaki Hiroki
Published: February 2020

Lithium ion batteries (LIBs) have attracted attentions as one of the most promising power sources for application in portable electronic devices and electric vehicles because of their high energy density and long life span. As for the pursuit of the next generation high-capacity LIBs, transition metal oxides (MOx, M = Fe, Mn, etc.) have been investigated as improved negative materials because of their higher theoretical capacities (>700 mA h g-1) than commercial graphite (372 mAh g-1). However, practical application of MOx in LIBs has been hindered by the poor cycling performance and low rate capability owing to its poor electrical conductivity and large volume expansion/shrinkage during the Li insertion/extraction processes. Compositing of the nanosized oxide with carbon materials can effectively enhance the cycling performance. The carbon matrix could effectively enhance the electrical conductivity of oxides and alleviate the change in volume arising from lithium insertion/extraction.

Solution combustion synthesis (SCS) is a highly exothermic and self-sustaining reaction process by heating a solution mixture of aqueous metal nitrates and organic fuels. A variety of functional oxides, such as perovskite oxide catalysts and cathode oxide materials for LIBs has been synthesized by this method. This method offers several benefits, such as (1) the utilization of an exothermic reaction requiring no additional energy during the combustion process, (2) larger surface areas of nanosized or porous products, (3) homogeneous doping of trace amounts of various elements in a single step. By controlling the combustion reaction conditions to avoid the complete combustion of the carbonaceous material, the remaining carbon material and metal oxides can form composites for advanced LIB anode materials. This can be achieved by (1) adding excess amount of fuel and (2) adding carbon additives and performing the SCS under inert atmosphere.

In this study, we present the facile production of MOx/carbon composites by SCS. The composition, phase structure and morphology of the composites are characterized by X-ray diffraction, X-ray photoelectron spectroscopy, Raman spectroscopy, and scanning and transmission electron microscopy. The results indicate that MOx nanocrystals are uniformly embedded in the carbon matrix. The composite materials exhibit high discharge/charge capacities, superior cycling performance, and good rate capability. The easy production and superior electrochemical properties enable the composites to be promising candidates as anode alternatives for high-performance LIBs.

References:

RSC Advances, 2015. 5(27): 21066-21073.

Journal of Alloys and Compounds, 2015. 633(0): 424-429.

International Journal of Hydrogen Energy, 2013. 38(30): 13238-13248.
Oxygen Containing Carbon Materials for High Capacity and Fast Chargeable Anode Materials of Lithium Ion Batteries
Authors: Cheng Qian , Okamoto Yasuharu , Murakami Tomoo , Tsuji Masayoshi , Matsuo Yoshiaki
Published: February 2020

The lithium-ion battery is the most promising energy storage devices for variety of applications from portable electronics to electric vehicles because of its high energy density, power density and cycle life. However, the upcoming boom for artificial intelligence (AI) assisted transportations, Internet of Things (IoT) or potential wireless financial technologies may require batteries with much higher energy density and fast chargeable capability. Silicon and silicon monoxide have been extensive investigated for high capacity anode for more than 10 years. However, they are still hard to be used in real practice because of large volumetric expansion, poor cycle life, and bad rate capability. On the other hand, graphite is the most popular commercialized anode material for Li-ion battery because of its excellent coulombic efficiency, long cycle life, low cost and ease of processing. However, the limited theoretical capacity (372 mAh/g) and small interlayer spaces (0.335 nm) made it difficult to be used in the application of Li-ion batteries with higher energy density and fast chargeable Li-ion batteries (Fig.1a). In this study, we have introduced a novel Graphene-Like-Graphite (GLG) anode material to be used in Li-ion batteries with higher capacity and good rate capability. According to the Li-NMR study, lithium ions can intercalate into graphene layers with oxygen at 0-1.2V (vs Li) with non-stage phenomenon and delivered a capacity more than 372mAh/g. Meanwhile, at a higher potential range from 1.2 to 2V (vs Li), lithium ions continuous react with oxygen containing functional groups reversibly on the basal plane of each graphene layer. As a result, the GLG could have an initial discharge capacity up to 608mAh/g which is much larger than conventional graphite (372mAh/g). It was investigated that the higher oxygen content offers a higher reversible capacity over 1.2V (vs Li) discharge. Atom resolution STEM is also carried out for the characterization of single layer graphene of the GLG. It was learned that the GLG graphene layer has pore structure with the size less than 2nm, moreover the oxygen containing functional groups were attached on both basal plane and pores` s edge. The GLG was also characterized with NCM111 cathode for full-cell rate capability and cyclability. The cell charged to 60% of the capacity up to 6C (10min) charge with 103wh/kg cell design, while have good cycle ability. XPS, HAXPES, C-NMR were also used for the characterization of the GLG materials. Finally, a structure model was proposed for the next generation high rate, high capacity carbon based anode materials.

Figure 1
Bismuth Thin Films As Anodes for Low Voltage All-Solid-State Li-Ion Batteries
Authors: Pecquenard Brigitte , Galipaud Jules , Cotte Stéphane , Le Cras Frédéric
Published: February 2020

The fast-growing market of portable electronic systems, generally battery-powered, has triggered the race for the development of high-performance microprocessors and Systems-on-a-Chip (SoCs) using low power consumption integrated circuits. As a consequence, the energy supply of such optimized components can also be ensured today by miniaturized power sources such as microbatteries (whose capacities range from 1 to 100 µAh). All-solid-state lithium microbatteries can interestingly be manufactured by vacuum deposition processes, also widely used in the microelectronics industry, and they do not to contain a liquid electrolyte, that is beneficial to safety [1]. The association of microelectronic components and microbatteries is going to give birth to new products within three main domains: back-up power for Dynamic Random Access Memory (DRAM) or Real-Time-Clocks (RTC), embedded energy and autonomous devices. Besides, the supply voltage required to operate electronic chips has steadily decreased during the last decades and is now lower than 2V. As a consequence, contrary to conventional Li-ion batteries, low to moderate voltages are preferred for lithium microbatteries. The latter can be achieved by using either a low voltage cathode [2] or a high voltage anode with an adapted Li-ion microbattery design [3].

Bismuth undergoes electrochemical alloying with lithium around 0.8 V/Li+/Li. The formation of LiBi, then of Li3Bi through biphasic reactions results in two perfectly defined voltage plateaus [4] and a theoretical volumetric capacity of 377 µAh.cm-2.µm-1. Thus, this electronically conductive and non-toxic element is an attractive anode material for Li-ion microbatteries. Nevertheless, until now, no sufficient reversibility of the reaction was ever achieved (in liquid electrolyte) [5] and the deposition of only rough Bi thin films incompatible with an integration in microbatteries was reported in the literature [6]. This presentation will therefore focus on the optimization of sputtering conditions to obtain pure and smooth Bi thin film electrodes (Ra ≈ 40nm), then on their electrochemical behavior in liquid electrolyte and for the first time on their final performance in all-solid-state Li/LiPON/Bi thin film batteries.

References:

[1] B. Fleutot, B. Pecquenard, F. Le Cras, B. Delis, H. Martinez, L. Dupont, D. Guy-Bouyssou, J. Power Sources, 196 (2011) 10289

[2] V. Pelé, F. Flamary, L. Bourgeois, B. Pecquenard, F. Le Cras, Electrochem. Comm., 51 (2015) 81

[3] F. Le Cras, B. Pecquenard, V. Dubois, V.P. Phan, D. Guy-Bouyssou, Adv. Energy Mater., 5 (2015) 1501061

[4] J. Wang, I. D. Raistrick, R.A. Huggins, J. Electrochem. Soc., 133 (1986) 457

[5] O. Crosnier, T. Brousse, X. Devaux, P. Fragnaud, D.M. Schleich, J. Power Sources, 94 (2001) 169

[6] D.H. Kim, S. H. Lee, J. K. Kim, G. H. Lee, Appl. Surf. Sci., 252 (2006) 3525
Effect of Iodination Temperature on the Polyvinyl Alcohol Based Carbon Nanofiber for Lithium Ion Battery Anodes
Authors: Serife Pampal Esra , Stojanovska Elena , Kucukkalfa Serra , Uzun Davut , Yilmaz Safak , Kilic Ali
Published: February 2020

Nanofibers has broad application areas including energy, filtration, biomedical and many other engineering fields due to their high porosity, high surface area to volume ratio. Researchers studied several materials and production methods in order to obtain different superior properties from nanofibers.

Recently, lithium ion batteries has achieved huge importance due to growing demand for portable electronics, electric vehicles and grid energy storage,etc. Batteries have different components among them anodes have crucial importance on the battery capacity, cycle life and rate capability. One of the promising 1D anode material as carbon nanofibers can provide fast electron transport, reduced lithium ion diffusion lenghts and enhanced surface area comparing to commercial electrodes.

There are several carbon nanofiber precursors, such as polyacrylonitril(PAN), lignin, pitch, polyimide(PI).. etc. among them polyvynil alcohol has important advantage because of their environmentally friendly, water soluble and low cost properties. Polyvinyl alcohol (PVA) is a water-soluble polyhydroxy polymer with a broad range of industrial and technical applications. It has been used as a carbon precursor or directly used as anode, cathode or separator in Li-ion batteries. PVA based carbon nanofibers can be easily obtained by electrospinning and subsequent carbonization PVA might be an environmentally friendly alternative material for PAN based carbon fibers. However rather than oxidative stabilization in PAN based precursors, linear PVA chains must be stabilized via other suitable processes. There are various routes that have been proposed to suppress the thermal degradation of PVA before carbonization step, such as using HCl, H2SO4, NH4 vapour or chemical impregnation into different salts. Stabilization of PVA under iodine vapour is a promising approach with high carbon yield for obtaining carbon nanofibers.

In this study, we investigated the effect of iodination temperature on the morphology, chemical structure, and electrical properties of carbon nanofiber webs fabricated from electrospun PVA nanofibers. Obtained nanofibers were subjected to different iodination temperature and then converted into carbon nanofibers. It was found that increasing the iodination temperature provides higher carbon yield. Carbon nanofibers were used as binder free, self- standing anode for lithium ion battery. Battery performances showed that PVA based carbon nanofibers are promising anode materials for lithium ion batteries.
Si-Based Ge and GeSn Material Epitaxy and Thermal Stability Characterization
Authors: Xue Chunlai , Zhang Xu , Cong Hui , Cheng Buwen , Wang Qiming
Published: February 2020

_In the past decade, Si photonics has become one of the hottest research topics in the world since it holds great promise for maintaining the performance roadmap known as Moore’s law. The application of silicon photonics technologies to requires the development of high quality Si-based materials for photonics devices monolithically integrated to a Si platform. Germanium (Ge), due to its large absorption coefficient at near-infrared frequencies, and its lower cost and compatibility of parallel processing with silicon compared to III-V semiconductors, is perceived as the best candidate for on-chip photodetectors. Meanwhile, Ge is a pseudo-direct bandgap material because its direct Γ-valley CB is just 136.5 meV above the lowest L-valley CB at room temperature . This energy difference can be effectively reduced by incorporating Sn, another group-IV element, into Ge to modulate the band structure. GeSn alloy has been proven to be another promising material for the Si-based laser and PDs covering all telecommunication windows.

In this presentation, Ge 、GeSn and GeSn/Ge MQW have been grown on Si, Ge/Si and Ge. The crystallinity and growth quality of the Ge and GeSn films were investigated through material characterization methods including x-ray diffraction, scanning electron microscopy, energy-dispersive x-ray spectroscopy, and transmission electron microscopy. In order to grow GeSn on Si and Ge subtrate,the growth is performed at low temperature, but the devices fabrication process will be carried out at high temperature, so the stability study is important. The effect of rapid thermal annealing on the conversion of metastable elastically strained GeSn layers into a plastically relaxed state is also examined. the results show that GeSn alloy have good thermal stability at 500℃if Sn contents are as low as ~3%. The stability of the GeSn/Ge MQW structure is temperature-dependentand and the temperature over 400℃ should be avoided to guarantee the structural integrity of the MQWs.
A Multimode SiGe BiCMOS 5–6 GHz Front-End IC that Enables 802.11ac Wave 2 and 802.11ax Wireless LAN Front-End Designs
Authors: Huang Chun-Wen Paul , Christainsen Kenny , Allum Justin , Lam Lui , Chen Andrew , Doherty Mark , McPartlin Mike , Vaillancourt Bill
Published: February 2020

A multimode 4.9–5.9 GHz ultra-linear single chip front-end integrated circuit (FEIC) for 802.11ac and emerging multi-gigabit per second (Gbps) wireless local area network (WLAN) applications is presented. The design is based on SiGe BiCMOS and realized in a 2.0 x 2.0 x 0.5 mm3 package. The FEIC design consists of both transmit (Tx) and receive (Rx) chains, which integrates a single-pole double-throw (SPDT) Tx/Rx CMOS switch, a SiGe power amplifier (PA), and a SiGe low noise amplifier (LNA) with a CMOS bypass attenuator. The SiGe PA in the transmit chain integrates input and output matching networks, harmonic filters, out-of-band rejection filters, supply voltage regulator and multi-mode bias circuits, temperature and voltage compensated power detector with on-chip directional coupler, and CMOS-compatible enable circuitry. The PA is controlled by the on-chip temperature and voltage compensated bias controller. With a 5 V supply, the transmit chain features 31 dB gain and excellent linearity. The transmit chain can deliver 19 dBm output power with current consumption 220 mA meeting below -40 dB Dynamic Mode Error Vector Magnitude (DEVM) for 1024 QAM signals and 20 dBm with current consumption 250 mA meeting below -35 dB DEVM for 256 QAM signals. The feature of ultra-low DEVM enables the emerging 1024-QAM applications. The harmonics emissions of the transmit chain can achieve below -50 dBm/MHz, greatly exceeding FCC out-of-band emission requirements. In addition, the linearity of the transmit chain output power is well scaled with the supply voltage from 3.0 V to 5.5V and insensitive to signal modulation bandwidths as well as duty cycles. The low linearity mode features 50 mA lower current consumption comparing to the high linearity mode. With the use of digital pre-distortion (DPD), it can achieve the similar linear power with 50 mA current reduction. The integrated log detector with an on-chip directional coupler ensures the accurate power control over 24 dB with less than 0.5 dB power control inaccuracy under VSWR 3:1 mismatch, which significantly increases the dynamic range and accurate power control for the transmit path. The Rx chain features noise figure (NF) below 2.5 dB with 15 dB gain and the current consumption of 8 mA as well as 8 dBm IIP3. The receive chain also integrates an 8 dB bypass attenuator having 25 dBm IIP3 with 3uA current consumption, which can prevent the WLAN radio from saturation under high field strength illuminations. All these unique features provide a turn-key solution for the single band or dual-band 802.11ac radio front-end circuits and emerging multiple gigabits per second high linearity WLAN radio designs.

Figure 1
Physics of Metal/Ge Interfaces; Interface Defects and Fermi-Level Depinning
Authors: Nakayama Takashi , Sasaki Shogo , Asayama Yoshihiro
Published: February 2020

Germanium (Ge) has high carrier mobility compared to Si and is expected again to work as a promising key material in next-generation high-speed energy-saving devices. With respect to metal/Ge interfaces, however, there still exist serious issues to be overcome for applications; one which is the control of interface disorders and Schottky-barrier height (SBH). In this work, we discuss this issue based on fundamental properties of metal/Ge interfaces evaluated by theoretical calculations.

It is well known that a variety of metal/Ge interfaces show a strong Fermi-level pinning (FLP); the Fermi energies of various metals are located at similar energy positions around the valence-band edge of Ge irrespective of the kind of metal, which induces the difficulty in controlling the SBH by simply changing the kind of metal. By the first-principles calculations, we found that this FLP is caused by the small band gap of Ge and the long penetration depth of metal-induced gap states (MIGS) into Ge layers even at clean interfaces [1]. Moreover, by evaluating the formation energies of various defects and dynamical atom motions around the interface, we showed that the MIGS are well hybridized with electronic states of defects and become the leading actors to increase the interface disorders (See Fig.1 in attached file for the case of vacancy defect in Ge layers). This result indicates important concept that the MIGS promote the disorder-induced gap states (DIGS). Correspondingly, even at weakly FL-depinned Fe3Si/Ge interface, the interface defects also promote the FLP [2].

One of recipes to release the FLP is to insert the third materials into the interfaces by the segregation of dopant atoms such as S and P, similar to the cases of metal/Si interfaces [3], and by the stacking of transition layers made of semiconductor/oxide. For example, we found that the appearance of ultrathin semiconducting α-Sn layers between metallic β-Sn and Ge layers works to increase the SBH for hole carriers, in agreement with recent experiments. Similarly, when GeO2 oxide is produced between metal and Ge layers, the MIGS penetration into Ge layers is prohibited and the SBH increases to the original position (See Fig.2 in attached file for the case of Al/Ge interfaces).

These results are discussed in details, together with reviewing recent experiments and focusing on the fundamental physics at metal/Ge interfaces.

 

[1] T. Hiramatsu et al., Jpn. J. Appl. Phys. 53, 058006 (2014).

[2] K. Kobinata and T. Nakayama, Jpn. J. Appl. Phys. 53, 035701 (2014).

[3] T. Nakayama and K. Kobinata, Thin Solid Films 520, 3374 (2012).

Figure 1
Thermoelectric Properties of Ge-Rich GeSn Films Grown on Insulators
Authors: Kurosawa Masashi , Liu Kun , Izawa Momoka , Tsunoda Isao , Zaima Shigeaki
Published: February 2020

Thermoelectric generator has attracted attention because of their ability to recover waste heat with converting it to electricity. The energy conversion efficiency is related to the thermoelectric figure of merit Z, expressed as Z = S2σ/κ, where σ and κ is electrical and thermal conductivities, respectively, and S is the Seebeck coefficient. Consequently, in order to achieve a high Z value, the material must possess a unique combination of electrical and thermal properties, i.e., metal-like high σ and glass-like low κ. In our previous study on electrical and thermal properties of a Ga-doped Ge0.929Sn0.071 thin film grown on Ge(001), it was revealed that simultaneous realization of a high σ (6.5×102 S/cm) and a low κ (2.0 Wm-1K-1) by the incorporations of the Sn and Ga atoms into Ge matrix [1]. Very recently, Uchida et al. [2] has reported heat transport property of polycrystalline GeSn (poly-GeSn) films on SiO2, together with the carrier transport property, to assess self-heating effect of the poly-GeSn channel thin-film transistors. Here, they showed a relatively lower κ of 5–9 Wm-1K-1 for poly-Ge1-xSnx (x<0.14) compared with that for bulk Ge (60 Wm-1K-1) [3]. These results are quite beneficial in the field of Ge-based thermoelectric generator. However, the thermoelectric properties of GeSn films have not been entirely understood. It is therefore, in the present study, we aim to reveal the thermoelectric properties of the Ge-rich poly-Ge1-xSnx films grown by solid phase crystallization. Doping effects in poly-Ge1-xSnxon the thermoelectric properties will be discussed.

 

Acknowledgments

The authors would like to thank Drs. Hiroshi Onoda and Yoshiki Nakashima of Nissin Ion Equipment Co., Ltd. for providing the opportunity to use ion implanters. This work was partially supported by a Grant-in-Aid for Scientific Research (S) (Grant No. 26220605) of the JSPS and PRESTO from JST.

 

References

[1] M. Kurosawa, M. Fukuda, K. Takahashi, M. Sakashita, O. Nakatsuka, and S. Zaima, “Thermophysical characterizations of Ge1-xSnx epitaxial layers aiming for thermoelectric device,” 9th International Conference on Silicon Epitaxy and Heterostructures (ICSI-9), Montreal, Canada, 4.4.1, May 21, 2015.

[2] N. Uchida, T. Maeda, R. R. Lieten, S. Okajima, Y. Ohishi, R. Takase, M. Ishimaru, and J.-P. Locquet, Appl. Phys. Lett. 107, 232105 (2015).

[3] C. J. Glassbrenner and G. A. Slack, Phys. Rev. 134, A1058 (1964).
Integration of High Quality III-V Materials on Si Using the Aspect-Ratio-Trapping Technique
Authors: Zhou Xuliang , Li Shiyan , Pan Jiaoqing
Published: February 2020

III-V compound semiconductor materials grown on elemental semiconductor substrates have attracted much attention due to their mobility and direct bandstructure. And the III-V/Si system could combine the advantages of both material systems. The growth of high quality III-V thin films on Si (or Ge) is the first crucial step for III-V high-mobility or optical devices. However, The large lattice mismatch between III-V materials and Si is the main challenge for its integration on large sized Si wafers. Recently, the aspect-ratio trapping (ART) technique offers an elegant and cost effective solution for integrating III-V materials on the Si wafer.

We report the selective area growth of III-V materials in “V-shaped” trenches on Si (001) substrates via metal-organic chemical vapor deposition (MOCVD).High quality GaAs thin films were achieved using a two-step growth process and the aspect ratio trapping method.In addition, high quality InP and InAs film was grown in trenches with a GaAs buffer layer. Material quality was confirmed by scanning electron microscope (SEM), transmission electron microscopy (TEM) and high resolution x-ray diffraction (HRXRD).This approach shows that these III-V materials could be high mobility channels for future CMOS technology node.

We also report a InGaAs/InP multi-quantum-well growth in nanoscale V-shaped trenches on Si (001) substrate was studied using the aspect ratio trapping method. A high quality GaAs/InP buffer layer with two convex {111} B facets was selectively grown to promote the highly uniform, single-crystal ridge InP/InGaAs multi-quantum-well structure growth. Material quality was confirmed by transmission electron microscopy and room temperature micro-photoluminescence measurements. This approach shows great promise for the fabrication of photonics devices like nanolasers on Si substrate.
Direct Wafer Bonding of SiC-SiC at Room Temperature by SAB Method
Authors: Mu Fengwen , Iguchi Kenichi , Nakazawa Haruo , Takahashi Yoshikazu , Fujino Masahisa , Suga Tadatomo
Published: February 2020

The efficiency improvement of power devices is of significance because the energy saving and prevention of global warming are urgent issues. However, it is difficult to realize further improvement by using the conventional silicon (Si) because of its limited physical properties. Silicon carbide (SiC) has attracted considerable attention owing to its superior properties such as wider band gap, higher dielectric breakdown field, higher thermal conductivity, higher stability in a harsh environment, and so on [1-3]. With successive breakthroughs in aspects of material technology and device fabrication such as 6-inch 4H-SiC wafer being and various devices becoming commercially available, SiC power devices will be widely used in the foreseeable future [4]. As a result, the fabrication and integration technologies of SiC power device in mass production will be very important. Wafer bonding is a widely used technology for device fabrication and integration, while studies about directly wafer bonding of SiC-SiC at low temperature are still hardly. Therefore, directly wafer bonding of SiC-SiC at room temperature by SAB method was investigated in this work.

In the directly wafer bonding process, the two SiC wafers surfaces were firstly activated by argon fast-atom-beam (Ar-FAB), followed by directly contacted in UHV bonding chamber under a certain pressure. After bonding, a scanning acoustic microscopy (SAM) was used to inspect the voids of the bonded wafer, followed by blade insertion method to test the bonding strength. In addition, the bonding interfaces were analyzed by high-resolution transmission electron microscopy (HR-TEM) and energy-dispersive X-ray spectroscopy (EDX).

References

M. B. J. Wijesundara, and R. G. Azevedo, Silicon carbide microsystems for harsh environments (Springer, New York, 2011), pp. 15.

Y. Hijikata, Physics and Technology of Silicon Carbide Devices, (InTech, Rijeka, 2012) pp. 181.

T. Kimoto, Symp. VLSI Technology, 2010, p. 9.

H. Okumura, MRS. Bull. 40, 439 (2015).
Novell Plating Processes for Silicon Based Pixel Detectors
Authors: Fritz Mathias , Nieland Sabine , Wittig Tobias , Bund Andreas
Published: February 2020

New generation silicon detectors produced in Thuringia (Germany) will play an important role in the future, during the upgrade phase of the Large Hadron Collider (LHC) at the CERN nuclear research center. Such detectors are used for monitoring radioactive reactions during the collision of highly accelerated positron radiations produced in large scale experiments like ATLAS (A
Toroidal LHC ApparatuS) or CMS (Compact-Muon-Solenoid).

The development of the new detectors aims at a functional improvement that will bring an enhanced resistance against radiation damage. At the same time, the surface reengineering for an increased active surface should address also important cost related aspects.

This paper will discuss recent results from the authors' labs on the development of such novel sensors. The aim is a full understanding and coverage of the complete production process for the sensor modules. An important challenge to be addressed is the development of low cost metallisation procedures for the silicon detectors that do not require lithographic steps. Especially promising are extreme small and round surfaces of about 10 µm diameter distributed over the entire detector surface with a contact pitch of 50 µm that would add up to several thousand contacts and a high contact density. Given the special structure of the detector surface, electric current can be generated by incoming electromagnetic radiation, e.g. light. This current can be used in a light-induced metallization process of the front side contacts. We will present results from a light-induced plating process involving nickel and tin. The suitability of this layer system for subsequent bonding processes will also be discussed.
Light Gated Zinc Tin Oxide Thin Film Transistor Fabricated Via Solution Process
Authors: Wang I-Wen , Li Jeng-Ting , Chen Jen-Sue
Published: February 2020

Zinc tin oxide (ZTO) is a transparent semiconductor based on earth-abundant elements. While most oxide semiconductor films were previously fabricated by vacuum-based deposition techniques, solution processes are increasingly popular due the lower cost and feasibility for large area deposition. In this work, ZTO films prepared by a solution route have been applied as the active semiconductor layer in a thin film transistor (TFT) with SiO2 or Al2O3 dielectrics. With thickness less than 10 nm, the ZTO film exhibits a good field-effect mobility of ~10 cm2/Vs, small subthreshold slope of ~0.5 V/decade and high on/off current ratio of ~107.

With light illumination of 405 nm wavelength and power density of 5 mW/cm2, the light sensitivity is in the order of 106 for the ID-off region and is less than 10 for the ID-on region. The light responsibility of ZTO TFT reaches around 2.5 and the maximum external quantum efficiency is 8.

Furthermore, to see the light gating effect, the ZTO TFT is operated without applying gate voltage but under light illumination (405 nm wavelength) of various power densities. At a drain voltage of 0.5 V, the drain current increases sharply from 0.3 μA to 12.1 μA when the light power density increases from 0.03 mW/cm2 to 0.25 mW/cm2. The increment of drain current becomes gradual for power intensity greater than 0.25 mW/cm2 (from 13.4 μA to 16.3 μA for light power density from 0.5 mW/cm2 to 5 mW/cm2). As a result, the solution-processed ZTO TFT can be gated with light illumination, in addition to the voltage gating mode. This finding will broaden the suitability of ZTO TFT in optoelectronic and optical communication applications.
(Invited) Low-Temperature Sol-Gel Derived Ultra-Flexible Metal-Oxide Thin-Film-Transistors and Their Applications
Authors: Jo Jeong-Wan , Heo Jae Sang , Kim Kyung-Tae , Kim Jaehyun , Kim Myung-Gil , Park Sung Kyu
Published: February 2020

Amorphous metal-oxide semiconductors have emerged as potential replacements for organic and silicon materials in thin-film electronics. The high carrier mobility in amorphous state and excellent large-area uniformity have extended their applications to active-matrix electronics including displays, sensor arrays, and X-ray detectors. Moreover, their solution processability and optical transparency have opened new horizons for low-cost printable and transparent electronics including wearable applications. However, metal oxide formation by sol-gel route requires a crucial annealing step at relatively-high temperature which impedes their incorporation onto the conventional polymeric substrates and thus high-performance flexible electronics. In this presentation, high performance solution-processed metal-oxide semiconductors as well as advancements in lowering processing temperature for thin-film-transistors (TFTs) and their applications for wearable electronics will be demonstrated. Additionally, the developments of advanced technologies for low-cost solution-processed metal-oxide TFT based sensor arrays and integrated circuits will be addressed.
The Oxide TFT By Anodic Oxidation
Authors: Shin Seong Min , Hong Min-Taek , Lee Jongmo , Yun Eui Jung , Bae Byung Seong
Published: February 2020

Oxide-TFTs (thin film transistors) have been studied and are being applied to the AMLCD and AMOLED. One advantage of the oxide TFT is higher mobility than amorphous silicon TFT. The oxide material such as IGZO (indium gallium zinc oxide) is sputtered for the active layer. In this experiment, we used anodic oxide instead of sputtered oxide layer. Anodizing is to oxidize the metal by applying the positive voltage to the metal in the electrolyte. Al and Ti metals were anodized and the anodization is possible even at room temperature. There are two ways of the anodization, one is the barrier type and the other is the porous type. For the electrical device application, a barrier type anodic oxidation is necessary. In the case of Al, thickness of the barrier type anodic oxide is proportional to the anodizing voltage in the electrolyte of citric acid. The oxidation starts at a constant current mode and changes to the constant voltage mode. The anodic oxide of Al was used for the gate insulator of the oxide TFTs. On a glass substrate, gate electrode was patterned after deposition of Al by DC-Sputtering. The Al was anodized to form an Aluminum oxide for the gate insulator. After deposition of Ti, it was patterned for the source/drain electrodes and an active region. After coating photoresist, it was opened on the region where the metal should be anodized to be an active region. The oxidized region of the Ti becomes the active region of the TFT. After removing the photoresist, it was annealed under the oxygen ambient to improve the TFT characteristics. During the anodization, the adhesion of the photoresist to the metal was deteriorated and the anodic oxidation occurred under the photoresist. To solve the problem, we deposited silicon oxide before coating the photoresist. After developing photoresist for the opening of the photoresist, the wet etching of the silicon oxide was performed, which made it possible to accomplish the anodic oxidation without the adhesion problem.
(Invited) 2D Material-like Ultrathin Single-Crystal Si Nanomebranes
Authors: Ahn Jong-Hyun
Published: February 2020

Ultrathin single crystal silicon with atomic scale like 2D materials offers the most promising route to create high performance electronic devices with good mechanical and optical properties. For the last decade, many examples of flexible, stretchable, and conformable electronic devices based on ultrathin silicon nanomembranes have been designed to overcome the limitations of conventional rigid semiconductor or 2D material based electronics. Ultrathin Si-based devices exhibit remarkable mechanical properties for integration onto soft substrates, and good optical transmittance in the visible range for use in transparent electronics. In this talk, I present the fabrication methods used to improve the optical and mechanical properties of single crystal Si based on a ‘top-down process’, and various kinds of transparent and foldable electronic devices enabled by ultra-thin Si nanomembranes.
(Invited) Diluted Magnetic Monolayer MoS2 Synthesis, Characterization and Device Applications
Authors: Xiang Bin , Zhao Benliang , Fan Yaohui , Wang Wenhui , Yang Lei
Published: February 2020

Keywords: Two dimensional; Monolayer; CVD; Spintronics; Spin injection

Recently, monolayer MoS2 has attracted intensive interests because of its special properties. MoS2-based field effect transistor exhibits a carrier mobility of 900 cm2 V-1 s-1 and an on/off ratio larger than 108.[1] However, its non-magnetic property has retarded its applications in the quantum devices. Diluted magnetic semiconductors have been extensively studied, as it bridges the ferromagnetic and semiconductor properties.[2] It shows a variety of new physical phenomena and functionalities.[3] There is few reports on diluted magnetic monolayer MoS2 semiconductors. In this paper, we design a rational synthesis of diluted magnetic monolayer MoS2 by a simple chemical vapor deposition method. By characterizing the structural, chemical composition, magnetic property, magnetic transport, we confirm the as-synthesized sample is single phase of diluted magnetic monolayer MoS2 with promising ferromagnetic property. We probe the mechanism of the ferromagnetic behavior observed in the as-grown diluted magnetic monolayer MoS2. The spin-injection efficiency is investigated by studying the injected relaxation and lift time. Our results would open up a new path way to develop the future flexible quantum devices and quantum computers.

References:

1. Radisavljevic, B. et al. Single-layer MoS2 transistors. Nature Nanotech. 2011, 6, 147-150.

2. Dietl, T., et al., Rev. Mod. Phys., 2014, 86, 187-251.

3. Dietl, T., Nat. Mater., 2010, 9, 965-974.
Low Temperature Grown Graphene on Ultra-Long Copper Nanowire By Carbon-Enclosed Chemical Vapor Deposition As Stable Transparent Conducting Electrodes in Harsh Environments
Authors: Manikandan Arumugam , Medina Henry , Chen Yu-Ze , Chueh Yu-Lun
Published: February 2020

Replacement of indium doped tin oxide (ITO) by metallic nanowires, metal mesh, CNT and graphene plays key role due to scarcity of indium and its brittleness for flexible optoelectronic devices. Copper nanowires synthesized by solution process are an attractive alternative to ITO due to the abundance of Cu and the low cost of solution process. However, it suffers oxidation and corrosion problems, which mainly affect the optoelectronic properties. Here, we proposed a new technique to achieve low temperature deposition of graphene to protect copper nanowire by carbon-enclosed chemical vapor deposition (CE-CVD) at 400 °C with a the low sheet resistance of 9 Ohms/sq and a transmittance of 85%. Graphene coted copper nanowire on glass show excellent oxidation resistance without sacrificing electrical conductivity even annealing at 240 °C in oxygen ambient more than 2 hr and also shows an excellent anti-corrosion in highly corrosive environments such as sea water, acidic and basic solutions. The highly stable non-corrosive and anti-oxidant graphene coated copper nanowire can be used as an alternative transparent conducting electrode (TCE) for emerging optoelectronic devices and applications working in harsh environments.
(Invited) Thermal Management of Metal Oxide Nanowire Sensor
Authors: Yanagida Takeshi
Published: February 2020

Here we report the thermal management of oxide nanowire sensor in both spatial and time domains by utilizing unique thermal properties of nanowires, which are (1) the short thermal relaxation time down to several micro-seconds and (2) the reduced thermal conductivity. Our method utilizes a pulsed self-Joule-heating of suspended SnO2 nanowire device to manage the thermal properties of nanowires. This thermal management of nanowire sensors enables not only the gigantic reduction of energy consumption down to ~ 102 pJ/s, but also enhancing the sensitivity when sensing NO2 (100 ppb). Furthermore, we demonstrate the applicability of the present methodology as sensors on flexible PEN substrate. Thus, this proposed thermal management of nanowires in both spatial and time domains offers a new strategy for various nanowire-based devices including sensors.
Individual-Particle Electron Tomography: A Method for Monitoring the 3D Structure of Low-Dimensional DNA-Based Nanodevice
Authors: Ren Gang (Gary)
Published: February 2020

DNA base-pairing has been used for many years to direct the arrangement of inorganic nanocrystals into small groupings and arrays with tailored optical and electrical properties. The control of DNA-mediated assembly depends crucially on a better understanding of the three-dimensional (3D) structure of the DNA-nanocrystal hybridized building blocks. Existing techniques do not allow for the structural determination of these flexible and heterogeneous samples. Here, we employed cryo-electron microscopy (cryo-EM) and negative-staining (NS) techniques to investigate the morphology of DNA-nanogold conjugates that were self-assembled from a mixture of an 84-base-pair double-stranded DNA (dsDNA) conjugated with two 5-nm nanogold particles for potential substrates in plasmon coupling experiments. Using NS electron tomography and the individual-particle electron tomography (IPET) reconstruction method, we obtained 3D reconstructed 14 electron density maps at a resolution of ~2 nm from each individual dsDNA-nanogold particle. Using these 3D density maps as constraints, we derived 14 conformations of dsDNA by projected a standard flexible dsDNA model onto the observed EM density maps using Molecular Dynamics (MD) simulations. The variation of the conformations was largely consistent with the variation from liquid solution. Moreover, the IPET approach provides the most complete experimental determination of the flexibility and fluctuation range of these directed nanocrystal assemblies to date. The general features revealed by these experiments can be expected to occur in a broad range of DNA-assembled nanostructures.
(Invited) Facile Horizontal GaAs Nanowire Schottky Solar Cells with Record High Efficiency
Authors: Han Ning , Ho Johnny C
Published: February 2020

Nowadays, it is still technological challenging to fabricate solar cells with the high efficiency and low cost aimed for the third generation photovoltaics as well as for powering nano-devices by smart power supply. In this study, highly crystalline, long and dense GaAs nanowires (NWs) are easily synthesized on amorphous SiO2/Si substrates in the solid source chemical vapor deposition (CVD) system. And the single GaAs NWs are fabricated into Au-Al asymmetric Schottky contact solar cells [2] by a simple ultraviolet photolithography process. The NW synthesis avoids the use of expensive single crystalline epitaxial substrates such as GaAs(111)B used in metal-organic (MO) CVD or molecular beam epitaxy (MBE) methods [1], and device fabrication gets rid of the complicated p-i-n structures complementation. Besides these low-cost advantages of the NW synthesis and device fabrication, the horizontal NW solar cell show a record high efficiency of ~17% under air mass 1.5 global (AM 1.5G) illumination as shown in Figure 1. This produces another record in addition to the vertically aligned p-i-n GaAs NW solar cells previously reported (40%), in which the superior photovoltaic performance is attributed to the light concentrating effect of NWs with diameter in the order of light wavelength [3]. Moreover, the GaAs NWs can be printed onto glass and plastics to enhance the output power as well as provide the transparent and flexible solar cells as shown in Figure 1. All these results show the promising prospect of the high quality GaAs NWs synthesis in low cost solid source CVD system, and the highly efficient photovoltaic applications in the simple Schottky contact configuration.

1          N. Han, J. J. Hou, F. Y. Wang, S. Yip, Y. T. Yen, Z. X. Yang, G. F. Dong, T. Hung, Y. L. Chueh and J. C. Ho, ACS Nano 7 (2013) 9138.

2          N. Han, Z. Yang, F. Wang, G. Dong, S. Yip, X. Liang, T. F. Hung, Y. Chen and J. C. Ho, ACS Appl. Mater. Interfaces 7 (2015) 20454.

3          P. Krogstrup, H. I. Jorgensen, M. Heiss, O. Demichel, J. V. Holm, M. Aagesen, J. Nygard and A. F. I. Morral, Nat. Photonics 7 (2013) 306.

Figure 1