bluuebunny/crossref_metadata_2025 huggingface dataset:
(Invited) Gel Electrolyte with Low Dielectric Loss for Electric Double Layer Capacitors
Authors: Su Yi-Han , Teng Hsisheng
Published: February 2020

This paper proposes a cyanide-containing polymer as the framework of gel electrolytes for electric double layer capacitors (EDLCs). Dielectric studies in a frequency range of 101-105 Hz demonstrate the fast polarization and low dielectric loss features of the gel electrolyte that entraps 1-M TEABF4/PC. The swift polarization of the gel electrolyte can be attributed to the high dipole moment of the contained cyanide functionality on the polymer chains. When supported with separator membranes, the ionic conductivity of the gel electrolyte is one order of magnitude higher than that of the 1-M TEMABF4/PC liquid electrolyte (10-2 S cm-2 vs. 10-3 S cm-2 at room temperature) owning to the presence of polarizable cyanide groups, which facilitate ion motion under the action of an applied electric field. In addition, the polymer framework improves the dissociation of ion-complexes to promote ion transport. Symmetric EDLCs assembled using the gel electrolyte exhibits specific capacitances of 199 and 130 F g -1 (within 0-2.7 V) at galvanostatic discharge rates of 0.5 and 100 A g-1, respectively, based on the carbon mass. The corresponding capacitances for liquid-electrolyte EDLCs are 172 and 109 F g-1. The gel EDLCs exhibit high stability, retaining ~95% of their initial capacitance after 20,000 cycles. An important feature of this gel electrolyte is its controllable gelling time. The electrolyte can be used in a manner similar to that of an ordinary liquid electrolyte during assembly and auto-gelation of the electrolyte subsequently takes place in the assembled EDLC. The implemented auto-gelation greatly enhances the durability of the resulting devices and is applicable in a wide range of energy storage systems.

Acknowledgments: This research was supported by the Ministry of Science and Technology, Taiwan (104-2221-E-006-231-MY3, 104-2221-E-006-234-MY3, and 106-3113-E-006-009) and by the Ministry of Education’s Aim for the Top University Project at National Cheng Kung University, Taiwan.
(Invited) Hybrid Electrodes and Materials for Hybrid Energy Storage
Authors: Gomez-Romero Pedro
Published: February 2020

Energy storage is increasingly recognized as a key technology to enable our ongoing transition to a sustainable energy model. Electrochemical energy storage will be key to this transition but is still far from optimal. That is why there is still plenty of room for new and novel types of materials for batteries and for supercapacitors. Hybrid materials offer opportunities for synergy and new properties with respect to their components.[1] Those formed by electroactive and conducting components are of particular interest for energy storage applications.[2, 3, 10]

We have developed a whole line of work dealing with hybrid electroactive (oxides[9], phosphates[4] polioxometalates[5-8]) and conductive materials (conducting polymers or carbons) for energy storage applications.[4-9] In this conference we will address the different approaches towards hybridizing energy storage by taking the hybridization concept to a chemical level and will discuss the several multifunctional synergies hybrids provide. In particular, in addition to conductive-electroactive combinations, we will show how hybrids can be designed to take advantage of dual energy storage mechanisms by combining the typical capacitive behavior of supercapacitors with the characteristic faradaic activities of batteries, thus, blurring the borderlines between these two types of devices.[10]

[1] P. Gomez-Romero Adv.Mater. 2001, 13(3), 163.

[2] P. Gomez-Romero et al. J.Solid State Electrochem. 2010 14(11), 1939

[3] Ait Salah et al. J.Electrochem.Soc. 2006, 153(9), A1692.

[4] A. Fedorkova et al. Electrochim.Acta 2010, 55(3), 943

[5] J. Vaillant et al. Progress in Solid State Chemistry, 2006, 34, 147.

[6] V. Ruiz, J. Suárez-Guevara, P. Gomez-Romero Electrochem. Communications 2012, 24, 35.

[7] J. Suarez-Guevara, V. Ruiz and P. Gomez-Romero J.Mat.Chem.A, 2014, 2, 1014.

[8] D P Dubal, et al. Journal of Materials Chemistry A 2015, 3(46), 23483

[9] D P. Dubal, R. Holze, P. Gomez-Romero. Scientific Reports 2014, 4 : 7349

[10] D.P. Dubal, V. Ruiz, O. Ayyad and P. Gomez-Romero Chem.Soc.Rev. 2015 44(7):1777-90
Synthesis and Characterization of Manganese (IV) and Cobalt (II/III) Oxides Based on Graphene for Supercapacitors Application
Authors: Jablonskienė Jolita , Šlopšnys Justinas , Pakštas Vidas , Vaičiūnienė Jūratė , Drabavičius Audrius , Jasulaitienė Vitalija , Tamašauskaitė-Tamašiūnaitė Loreta , Norkus Eugenijus
Published: February 2020

As an ideal electrochemical energy storage candidate, supercapacitors have gained increasing attention due to high power density, long cycle life and fast charge/discharge rate, which is more suitable for large power components. Conventional lithium-ion batteries are widely used in portable electronic equipment such as laptop computers, cell phones and electric vehicles.

In this study, the graphene supported manganese (IV) oxide (MnO2/GR), cobalt (II/III) oxide (Co3O4/GR) and manganese-cobalt oxide (MnO2-Co3O4/GR) nanocomposites were synthesized using the microwave irradiation method. The synthesized composites were characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM), Transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS). Electrochemical performance of the graphene supported MnO2, Co3O4 and MnO2-Co3O4 nanocomposites was evaluated using cyclic voltammetry (CV) and galvanostatic charge-discharge.

The graphene supported MnO2-Co3O4 nanocomposites have significant influence on the electrochemical performance as compared with that of the MnO2/GR and Co3O4/GR. The maximum specific capacitance of 152 F g-1 was achieved at the MnO2-Co3O4/GR in the 1 M Na2SO4 aqueous solution at the scan rate of 10 mV s-1.

Acknowledgement

This research is funded by the European Social Fund under the No. 09.3.3-LMT-K-712-02-0142 “Development of Competences of Scientists, other Researchers and Students through Practical Research Activities” measure.
Anodic TiO2 Nanotube Layers: Excellent Platform for Secondary Materials
Authors: Zazpe Raul , Krbal Milos , Prikryl Jan , Sopha Hanna , Dvorak Filip , Macak Jan M.
Published: February 2020

The self-organized TiO2 nanotube layers have attracted considerable scientific and technological interest over the past 10 years, which are motivated for their possible range of applications including photo-catalysis, solar cells, hydrogen generation and biomedical uses [1]. The synthesis of 1D TiO2 nanotube structure is carried out by a conventional electrochemical anodization of Ti sheet. The main drawback of TiO2 is its applicability in the UV light (wavelengths < 390 nm).

Atomic layer deposition (ALD) has been shown to be an effective technique to coat TiO2 nanotube layers homogenously with secondary materials. Ultrathin surface coating of TiO2 by secondary materials such as Al2O3 [2], ZnO [3] or MgO [4] annihilates electron traps at the TiO2 surface and thus increases the concentration of the photogenerated charge carriers.

This presentation will focus in detail on the coating of the nanotube layers with different (high) aspect ratios by various secondary materials using ALD. We will show initial photo-electrochemical results for anodic TiO2 nanotubes employed as highly ordered electron-conductive supports for host materials coated using ALD with secondary materials to enhance light absorbing capabilities of such hybrid systems. Experimental details and some very recent photocatalytic [5, 6], sensing [7] and solar cell [8] results will be presented and discussed.

References:

J. M. Macak et al., Curr.
Opin. Solid State Mater.
Sci.,
2007, 1-2, 3.

R. Zazpe et al., Langmuir, 2016, 41, 32.

A. Ghobadi et al., Sci. Rep.
2016, 6, 30587.

H. Park, et al., J. Electroceram.
2009, 23, 146.

H. Sopha et al., Appl. Mater. Today, 9 (2017) 104.

S. Ng et al.,
Adv. Mater. Interfaces
2017, 1701146.

S. Ng et al. Adv. Eng. Mater., 2017, 1700589

R. Zazpe et al., submitted.
(Invited) Layer Control of 2D-MoS2 by Atomic Layer Etching and Its Device Characteristics
Authors: Kim Ki Seok , Kim Ki Hyun , Ji You Jin , Yeom Geun Young
Published: February 2020

Molybdenum disulfide (MoS2) has been intensively investigated among the layered transition metal dichalcogenides (TMDs) due to its unique properties in various electronic and optoelectronic applications with different band gap energies from 1.29 to 1.9 eV as the number of layers is decreased. To control the MoS2 layers, atomic layer etching (ALE) composed of a Cl radical adsorption step and a reacted-compound desorption step via a low-energy Ar+-ion exposure can be a highly effective technique to avoid inducing damage and contamination that occur during the cyclic steps. In this presentation, MoS2 ALE is compared with conventional MoS2 plasma etching, and the MoS2-ALE mechanism is reported with the results of an experiment and a simulation. Especially, using the ALE method, mono-layer/bi-layer MoS2 field effect transistors (FETs) were fabricated their electrical characteristics were investigated and compared with the MoS2 FETs fabricated with pristine mono-layer/bi-layer MoS2. In addition, mono-/bi-layer lateral-heterojunction device was fabricated using ALE technique after PR patterning of bilayer MoS2.
(Invited) Precursor Innovations Directed Toward the Area Selective, Thermal Atomic Layer Deposition of Electropositive Metal Thin Films
Authors: Winter Charles H.
Published: February 2020

Our laboratory is developing new chemical precursors for the growth of electropositive metal and element thin films by atomic layer deposition (ALD). We are also interested in processes that exhibit area selective growth. ALD has many current applications in copper metallization, diffusion barriers, liners, and transistor fabrication. Thermal ALD is often preferred because plasmas can afford low conformal coverage due to radical recombination on the walls of deep and narrow features. There has been extensive progress in the thermal ALD of copper and noble metal films in recent years, because the positive electrochemical potentials allow relatively easy reduction of precursor ions to the metals. Thermal ALD approaches to most other metals and elements in the periodic table are not well developed, due to the negative electrochemical potentials of the ions and a current lack of ALD co-reagents that can convert the ions to the metals or elements. Herein, we will describe the thermal ALD growth of electropositive metals such as nickel, cobalt, aluminium, and others. The ALD of nickel and cobalt metal films has been achieved using precursors containing diazadienyl ligands (precursors 1 and 2). These precursors enable the deposition of cobalt and nickel metal films at temperatures below 200 °C and use alkylamines as benign co-reagents. Growth rates are high (0.60 Å/cycle for nickel, 0.98 Å/cycle for cobalt), high purity, low resistivity metal films are obtained, and the films have low rms roughnesses. The processes exhibit inherent selective growth on metal substrates such as platinum, ruthenium, and copper. By contrast, no growth is observed on insulating substrates. We will also overview a new thermal ALD process for the growth of aluminum metal films. This process entails treatment of surface-bound AlCl3 with a thermally stable, volatile aluminium hydride co-reagent. The growth rate for the aluminium metal ALD process is high, and high purity, low resistivity aluminium metal films are obtained. Prospects for the area selective growth of aluminum metal films will be presented. These examples demonstrate that ALD processes can be enabled for electropositive metals through careful design of precursors and chemistry. Moreover, many of the metal ALD processes exhibit area selective growth.

Figure 1
(Invited) Heterogeneous Integration of III-V Semiconductors on Si Photonics Platform
Authors: Hiraki Tatsurou , Aihara Takuma , Hasebe Koichi , Fujii Takuro , Takeda Koji , Nishi Hidetaka , Kakitsuka Takaaki , Tsuchizawa Tai , Fukuda Hiroshi , Matsuo Shinji
Published: February 2020

A silicon photonics platform is promising for manufacturing compact and low cost optical transceivers. Ge photodetectors have been developed by the epitaxial growth on Si. The next challenge is the on-silicon integration of group III-V semiconductors for laser diodes and high efficiency modulators. In this work, the III-V semiconductors are integrated on a silicon-on-insulator wafer by using the wafer bonding processes. We review the Ge-on-Si photodetectors and recently developed high efficiency III-V-on-Si metal-oxide-semiconductor capacitor Mach-Zehnder modulators.
Thermoelectric Properties of Synthesized P-Type Bi-Te-Sb Bulk Materials By Oxide Reduction Process
Authors: Park Min Soo , Ha Gook Hyun , Koo Hye Young
Published: February 2020

Bismuth telluride-based alloys have long been in the spotlight as they show promising ZT and high thermal stability near the room-temperature rigion. Although there are existing fabrication methods, but they all have problems like long processing time, lower sample thermoelectric property. Hence there exists a need to develop material of high thermoelectric properties in room temperature by simple method.

The present work consists of synthesis and characterization of Bi-Te-Sb nanocomposite. Nanocomposite in thermoelectric materials has been proven to be an effective paradigm for optimizing the high thermoelectric performance primarily by reducing the thermal conductivity. In addition, changes in thermal transport properties brought up by adding dopants,material nanostructuring and dispersed phase addition, in the Bi-Te−Sb material for this methodology are measured and discussed.

For the synthesis of p-typeBi-Te−Sb thermoelectric materials, reagent-grade raw materials (>99.99%) were used, and Bi2O3 (>99.99%), TeO2 (>99.99%), and Sb2O3 (>99.99%) powders were used. Bi-Te-Sb composites were fabricated by a high energy ball milling followed by spark plasma sintering process.

Bi-Te-Sb milled powders show agglomerated particles between 100nm and 300nm in size with almost faced or rounded shape. Reduction powders with irrelgularly facetted shape and about 500nm in size. As a field-assisted technique, spark plasma sintering (SPS) enables densification of specimens in a very short period of time compared to other sintering techniques. For high performance thermoelectric material synthesis, SPS is widely used to fabricate nanograin-structured thermoelectric materials by rapidly densifying the nanopowders suppressing grain growth. Phase of powders and bulk were analyzed by X-ray diffraction. The microstructures of powders and bulk were characterized by field emission scanning electron microscopy. Bi-Te-Sb bulk materials were analyzed electrical and thermal transport properties.

The achieved higher ZT value is attributed to the unique nanostructures which increase phonon scattering in the nanostructured materials to effectively reduce thermal conductivity..

Keyword Bi2Te3, Thermoelectric, nanostructure, SPS
Reduction of Thermal Stress in Copper TSV due to Annealing by Low TEC Copper
Authors: Dinh V Quy , Kondo Kazuo , Hirato Tetsuji
Published: February 2020

Introduction

Copper through-silicon via (TSV) is the key technology used in 3D packaging. However, the large mismatch in thermal expansion coefficient (TEC) between copper and silicon generates the thermomechanical stress inside and surround the TSV during fabrication process. This thermomechanical stress changes the carrier mobility1 and causes extrusion of copper2.

In this study, thermomechanical stress in copper TSV, as well as copper extrusion were reduced using low TEC copper. Moreover, conventional copper TSV was also studied as a comparison.

Results and Discussion

Fig. 1 shows TEC measurement results of conventional copper and copper electrodeposited with different concentrations of 2M5S leveler. The expansion length of conventional copper (line a) is linear with temperature. Copper pipes electrodeposited with 2M5S leveler (line b, c, and d) start to shrink at 120oC. The reason for the shrinkage of copper is the diffusion of carbon out of copper lattices3. Furthermore, at a 2M5S leveler concentration of 1 ppm, the expansion length of electrodeposited copper is lowest. Therefore, 1 ppm of 2M5S leveler is used for TSV filling for the next experiments.

Fig. 2 illustrates the cross-sectional views of copper TSVs after annealing at 500oC. Fig. 2a and 2b are conventional copper TSV. Fig. 2c is low TEC copper TSV (TSV filled with 1 ppm of 2M5S leveler). In Fig. 2a, cracks occur at the vias bottom. Wang found that the stress at the via bottom was very high by simulation using ANSYS4. That large stress is the cause of the cracks at the bottom of the TSV. In Fig. 2b, the extrusion height of conventional copper is about 1.5 µm. In Fig. 2c of low TEC copper TSV, no cracks are observed at the vias bottom. Moreover, the copper extrusion height is only 0.3 µm. Therefore, the stress as well as the extrusion of copper in TSV have been reduced by using low TEC copper.

References

S. E. Thompson, G. Sun, Y. S. Choi, and T. Nishida, IEEE Trans. Electron Devices, 53, 1010–1020 (2006).

A. Heryanto et al., J. Electron. Mater., 41, 2533–2542 (2012).

V. Q. Dinh and K. Kondo, ECS J. Solid State Sci. Technol., 6, P566–P569 (2017).

J.-S. Hwang, S.-H. Seo, and W.-J. Lee, J. Electron. Packag., 138, 31006 (2016).

Figure 1
What Happens to Low TCE Copper with Annealing
Authors: Kondo Kazuo
Published: February 2020

Introduction

Since the Copper resistivity is second lowest next to the Silver, the Copper electrodeposits have been very intensively used in the wiring for the semiconductor and the printed circuit board (PCB). The Copper problem is the thermal coefficient of expansion (TCE). The Silicon is 2.6x10-6 (1/K) and the copper is 17x10-6 (1/K). If the composite of the Silicon and the Copper (semiconductor and PCB), warpage, protrusion or delamination occurs. Warpage, protrusion or delamination resolution by low TCE copper examples are reported.

Results

TSV no pumping at 450oC. Crack and Copper extrusion occurs at bottom corner of conventional Copper TSV. No crack and no Copper extrusion occurs for our low TCE Copper (Fig.1).

No glass crack with 180oCx1hr for the glass interposer.

The Copper wiring for the IGBT wafer shows half warpage and no warpage at 350oC.

The coreless PCB warpage reduce to half.

No crack between the ceramics and the copper or Copper wire and IGBT chip in reliability test (Under examination).

No crack in via for via on via stacking for the buildup PCB (Under examination).

Reference

Q. Dinh and K. Kondo, ECS J. Solid State Sci. Technol., 6, P566–P569 (2017).

Figure 1
(Invited) Understanding Interfaces in Homoepitaxial GaN Growth
Authors: Hite Jennifer K. , Mastro Michael A , Luna Lunet E , Anderson Travis J.
Published: February 2020

The availability of high quality, free-standing GaN substrates opens windows for new device applications in III-nitrides, especially in vertical structures. With the introduction of these native substrates, the properties of nitrides are no longer dominated by defects introduced by heteroepitaxial growth. However, additional materials challenges are coming to the forefront that need to be understood and surmounted in order to allow homoepitaxial devices to achieve their full potential.

In order to enable device-quality epitaxial layers, a deeper understanding of substrate preparation and the effects of the substrate and growth initiation on the characteristics of the epitaxial layers is required for metal organic chemical vapor deposition (MOCVD) growth of homoepitaxial films. We investigate these effects on epi morphology, uniformity, and impurity incorporation at the interface and in the films. Although the initial substrate factors influencing the epi can be subtle, they can have far reaching impact on device performance. Additionally, the interface between substrate and epitaxy is examined to enable reduction of unintentional impurity incorporation, especially Si, at this surface. By studying these effects using wafers from several different vendors, with substrates from both hydride vapor phase epitaxy (HVPE) and ammonothermal techniques, an understanding of the requirements for device quality MOCVD homoepitaxy can be determined.
(Invited) Characterization of Phases and Defects in Compound Semiconductors
Authors: Rockett Angus A , Pogue Elizabeth , Pena-Martin Pamela
Published: February 2020

Defects in semiconductors can be difficult to characterize, especially in complex semiconductors such as the chalcogenides. This talk presents several different and relatively unusual methods for their study along with examples of results. The talk will focus on semiconductors used for photovoltaic applications but the talk should illustrate methods that would be of use with any semiconductor material. Specifically the talk will address the use of admittance spectroscopy, nuclear magnetic resonance (NMR), scanning microwave impedance microscopy (SMIM), scanning tunneling spectroscopy (STS) and others to study defects in CdTe, CuInSe2 (CIGS), and Cu2ZnSnS4 (CZTS), and related compounds. Examples of results include the identification of two defects in the energy gap of CIGS by admittance spectroscopy, band edge fluctuations in CIGS by STS and their impact on the ability to obtain atomic resolution images, organized point defect structures in CZTS by NMR, and grain and grain boundary behaviors in CdTe by SMIM. Other examples will be included as time permits.
(Invited) Antireflective and Sub-Band Pumped Photoconductive Solution Processed ZnO and Al:ZnO Quasi-Superlattice Films
Authors: Buckley Darragh , McCormack Robert , McNulty David , Zubialevich Vitaly Z. , Parbrook Peter J. , O'Dwyer Colm
Published: February 2020

Zinc oxide (ZnO) and Al-doped ZnO are important optoelectronic materials. ZnO in particular has a wide band gap (Eg
~ 3.3 eV at 300 K), large exciton binding energy (~66 meV) and especially for the variety of methods by which it can be processed. Moreover, ZnO is readily able to alloy with other metals in the oxide form and has a lattice that can facilitate interstitial doping using several metals, including Al and Sn. This gives ZnO a key role in optoelectronics, metal oxide thin films and thin film transistor (TFT) technologies.

We demonstrate that crystalline, epitaxial-like and highly ordered ZnO and Al:ZnO (AZO) quasisuperlattice thin films can be achieved from a precursor liquid at relatively low temperature via spin-coating, which crystallize with near epitaxy with a pronounced c-plane texture. We also show the visible and near-infra red (VIS-NIR) light spectroscopy of ZnO and Al:ZnO multi-layered thin film structures grown on oxidized silicon substrates and also define the growth conditions and processing to provide tunable antireflection coatings of ZnO and AZO.

Lastly, we show measurements demonstrating sub-band optical pumping of AZO QSLs that enable significant photoconductivity, whereas negligible photoconductance is observed in similarly grown ZnO QSLs. In AZO QSLs, conduction band electrons from valence band pumping at incident irradiation > Eg, are not required to initiate or enhance photoconductivity. The photoconductance scales with optical pump power and points to electron mobility possibly from transitions within the band gap of Al:ZnO or from localized photo-processes in Al-doped ZnO.

References

D. Buckley, D. McNulty, V. Z. Zubialevich, P. J. Parbrook and C. O'Dwyer, J. Vac. Sci. Technol. A, 35, 061517 (2017).

D. Buckley, D. McNulty, V. Z. Zubialevich, P. J. Parbrook and C. O'Dwyer, ECS Trans., 77, 99 (2017).

D. Buckley, R. McCormack and C. O'Dwyer, J. Phys. D: Appl. Phys., 50, 16TL01 (2017).

D. Buckley, R. McCormack, D. McNulty, V. Z. Zubialevich, P. J. Parbrook and C. O'Dwyer, ECS Trans., 77, 75 (2017).
(Invited) Impact of High Temperature Processing on Copper-Related Light-Induced-Degradation in Silicon Devices
Authors: Savin Hele
Published: February 2020

Copper (Cu) impurities are known to cause harmful light-induced degradation (Cu-LID) in p-type silicon, even when present in 1E10 cm-3 concentrations. Therefore, it is important to be able to control Cu impurities during device fabrication. In case Cu impurities cannot be fully avoided, the most obvious way to mitigate Cu-LID is gettering, i.e. relocation of Cu impurities from the active device areas to locations in which they are not harmful. Due to high diffusivity of copper, such relocation is expected to be relatively simple as compared to slow-diffusing impurities.

Here we report our experimental findings on the gettering of Cu and its impact on Cu-LID effects and demonstrate that e.g. the standard phosphorus gettering does not always prevent the occurrence of Cu-LID. Specifically, time-temperature profiles of the device process steps, copper contamination level as well as bulk micro defects present in the wafers play a critical role in the final gettering efficiency. For instance, we show that a typical rapid thermal anneal (RTA, a few seconds at 800 ºC) used commonly in the semiconductor and photovoltaic industries is sufficient to release significant amount of Cu impurities from the phosphorus-doped layer back to the wafer bulk in seemingly gettered wafers.

We also study the impact of Cu-LID on final device operation, namely silicon solar cells, which are processed in industrial environment. We carefully contaminate Cz-substrates of different quality with different amounts of copper and process the substrates into complete industrial Cz-Si solar cells. We demonstrate that copper can be present in significant concentrations in the bulk of the finished cells after being exposed to only trace surface contamination. Consequently, even a small local copper contamination area is sufficient to induce strong LID in the full-sized (8 inch) cell parameters, resulting e.g. in ~7% relative efficiency loss during illumination.
(Invited) Understanding the Correlation of Molecule Structure and Charge Transport Properties in Organic Thin-Film Transistors
Authors: Hu Yuanyuan , Liao Lei
Published: February 2020

Recent development of organic semiconductor materials has led to the remarkable enhancement of mobility over 10 cm2/Vs in organic thin-film transistors (OTFTs). Despite these achievements, a thorough understanding of the correlation between molecular structure and charge transport properties is still not achieved. It is essential that we have a comprehensive picture of the structure-property relationship for these materials to further improve the mobility. However, this is a very challenging task since the resulting effects of molecule structure changes can be so manifold. In this work, we investigated the structure-property correlation by finely tuning the molecule structure of organic semiconductors and comparing the performance of TFT devices, aiming to deepen our knowledge of the structure-property relationship and to provide guidance for optimizing the synthesis of high-mobility organic semiconductors. Specifically, we have studied how the molecule length and molecule symmetry affect the charge transport properties of small-molecule semiconductors. We have also researched the effect of the donor unit length on the charge transport properties of donor-acceptor (D-A) copolymers. The work has at least clarified how these factors such as molecule length, molecule symmetry and the length of donor units influence charge transport in organic semiconductors. Our work thus is enlightening for people to understand the charge transport physics in OTFTs and it is also instructive for chemists to optimize the synthesis of high-mobility organic semiconductors.
(Invited) Dual-Gate TFT for Chemical Detection
Authors: le Bihan France , Donero Laetitia , Le Borgne Brice , De Sagazan Olivier , Tessier Pierre-Yves , El Mel Abdel-Aziz , Kovacevic Eva , Le Brizoual Laurent
Published: February 2020

Field effect transistors possesses many advantages for chemical detection. As their electrical characteristics strongly depend on electrical charges located on their surface, they are able to measure with good sensitivity and very precisely any variation of charges concentration of the surrounded media. They can be easily integrated, are low-cost and provide a rapid and reliable result. The main application developed here is the pH measurement. In this case, the gate contact is removed and replaced by a liquid polarized by a reference electrode, leading to the ISFET technology. Those structures can also be developed by using a thin-film technology. The technology we developed is based on LPCVD polysilicon, silicon oxide and nitride deposited by CVD.

The sensitivity of ISFET or ISTFT is limited by Nernst equation, but can be enhanced by using dual-gate structures. In this technology, capacitive enhancement can be optimized by choosing specific thicknesses and materials for back and top gates. In this case, the sensitivity enhancement is theoretically given by the ratio of the top gate capacitance to the back-gate capacitance. This technology has been developed also by using thin-film transistors from polysilicon material.

Several structures have been developed in order to obtain good electrical performances for field-effect transistors, as low threshold voltage and good electrical characterization for back and top gates. Those characteristics are controlled by a good choice of insulator, and a thickness optimization.

Transistors are characterized with different polarizations; in back-gate, top-gate and dual-gate operating modes. Capacitive enhancement in determined for the different cases and compared to theory.

Transistors are then used for chemical detection, especially with measurement of pH. ISFET is already highly used for pH measurement, but its sensitivity is limited to 59 mV/pH. By using a dual-gate structure, this sensitivity can be substantially enhanced. The developed structures, based on previous studies of dual-gate TFTs, includes a back-gate contact, and an integrated electrode at the surface for the top-gate liquid polarization. Threshold voltage are measured and optimized. A slight doping of the active layer induces a decrease of the threshold voltage, necessary in the case of measurement in liquids. Sensitivities for pH measurement are compared with theory and show the capacitance enhancement.

Figure 1
Low Power Consumption Oxide Thin Film Transistor
Authors: Hwang Sang Ho , Lee Sang Min , Baek Yeong Jo , Kang In Hye , Han Ye Lin , Bae Byung Seong
Published: February 2020

Oxide thin film transistors (TFTs) have attracted much attention for potential applications in active- matrix organic light emitting displays(AMOLED) and liquid crystal displays (LCDs) due to the advantages of higher mobility than amorphous silicon TFT. Currently, oxide TFTs are being used in OLED TV and efforts are focused on improving electrical stability and process reliability. For mobile applications such as biosensors and wearable applications, low power consumption is required.

Much research is underway to realize biosensors and wearable devices with low power consumption, and very thin insulating films are needed. A thin insulating film can be formed by several ways and much more simple process is required.

With thin gate insulator it’s possible to reduce the operation voltages, which reduces the power consumption. The thin gate insulator was applied to the top gate amorphous oxide TFT as shown in Fig. 1. An IGZO active layer was deposited by RF sputtering and patterned. After gate pattern with thin gate insulator, source/drain region of IGZO layer was doped by oxygen plasma. The source/drain metal was deposited by DC magnetron sputtering and patterned. The operation voltage below 0.5 V was accomplished.

Figure 1
Electroformation and Collection of Giant Liposomes on a Microchip
Authors: Wang Zhenyu , Fan Ting , Zhang Xiaoling , Cao Hua , Hu Ning , Yang Jun , Li Faqi
Published: February 2020

Due to its micrometer scale and similar membrane structure as the cell membrane, the giant liposome becomes an important lipid structure and is widely used in many research fields as a cell or cell membrane model, microreactor, carrier, and so on.

Electroformation is an important preparing method for giant liposomes. However, it’s a complex process and may be influenced by numerous factors, so its efficiency, size homogeneity and repeatability are still required to be improved.

In this work, all main steps of the giant liposome electroformation were analyzed. For several different kinds of lipid molecules, the lipid concentration, lipid film formation style, and the electrical signals were discussed for higher efficiency and repeatability. Furthermore, a collection method was proposed, in which the formed giant liposomes could be sorted and collected. Finally, a microchip integrated the electroformation and collection parts was developed, in which the preparation and collection of conforming to the requirements giant liposomes can be done simply and efficiently.
Investigation of Li0.6FePO4 Phase Separation Kinetics Starting from Solid Solution
Authors: Savignac Laurence , Polcari David , Schougaard Steen Brian
Published: February 2020

The major contribution of lithium ion batteries towards sustainable energy originates in their use as energy vectors. In this context, lithium iron phosphate represents a safe, stable and environmental benign cathode material. The phase transition process during charge and discharge leads to questions regarding reactions rates, as the deintercalation/intercalation process via a phase transition mechanism is expected to strongly affect ionic and electronic transport. In order to study intrinsic properties of partially lithiated lithium iron phosphate, this study reports on factors that affect the transformation of the metastable Li0.6FePO4 solid solution prepared using both physical and chemical means.

The stability of the solid solution was examined using a series of diverse experimental conditions. Crystal structure effects were examined via X-ray diffraction (XRD) while more localized changes were revealed by attenuated total reflectance infrared spectroscopy (ATR-IR). Specifically, the internal vibrations of the phosphate group were used with the aim of detecting lithium rich and lithium poor phases. These two techniques corroborate to distinguish the metastable solid solution phase relative to the olivine and heterosite phases which emerge over time. Particles morphologies and size distribution were analysed by field-emission gun scanning electron microscopy (FEG-SEM) and dynamic light scattering (DLS) respectively. In addition, lithium content was confirmed by flame emission spectrometry (AES). The developed techniques and results relative to the solid solution metastability will serve as the basis for upcoming kinetics studies. These studies will rely on imposing a uniform reaction environment on the entire particle population, in contrast to kinetics derived from electrochemical analysis using composite electrodes.
Unveiling Polymeric Binder Distribution within Electrodes for High-Energy-Density Li-Ion Batteries By Measuring Adhesion Properties As a Function of Depth
Authors: Lee Yong Min , Byun Seoungwoo , Roh Youngjoon , Jin Dahee , Ryou Myung-Hyun
Published: February 2020

To improve the energy density of state-of-the-art lithium-ion batteries (LIBs), there are still extensive efforts to find new materials to deliver higher capacity. However, it takes a long time to put some candidates into a practical usage. Along with it, to optimize the electrode or cell design is in parallel and continuously upgraded by increasing loading level of electrodes or decreasing inactive material content within the cell. For this purpose, it is very important to analyze the polymeric binder distribution within the electrode carefully. However, due to limited analysis tools, it is too time-consuming process to get informative data. Fortunately, a new tool, surface and interfacial cutting analysis system (SAICAS), was developed and being used to reveal the adhesion properties of composite electrodes for LIBs [1-5]. Herein, we report the possibility to unveil the polymeric binder distribution with the electrode by correlating the adhesion strength to relative polymeric binder content. Totally different binder distribution within the electrode was built by controlling the drying temperature and confirmed by an EDX mapping technique. In addition, their electrochemical performance is also compared by changing operation conditions [6].

References

[1] B. Son, M.-H. Ryou, Y. M. Lee et al., ACS Applied Materials & Interfaces, 6 (2014) 526-531

[2] J. Choi, M.-H. Ryou, Y. M. Lee et al., Journal of Power Sources, 252 (2014) 138-143

[3] J. Choi, M.-H. Ryou, Y. M. Lee et al., ACS Applied Materials & Interfaces, 7 (2015) 14851-14858

[4] D. Song, M.-H. Ryou, Y. M. Lee et al., Advanced Materials Interfaces, 3 (2016) 1600270

[5] K. Kim, M.-H. Ryou, Y. M. Lee et al., ACS Applied Materials and Interfaces, 8 (2016) 23688-23695

[6] K. Kim, S. Byun, J. Choi, M.-H. Ryou, Y. M. Lee et al., ChemPhysChem, Accepted in 2018

Figure 1
A New High Performance Lithium-Ion Battery: Development of 3D Architecture
Authors: Guerin Camille , Gebel Gerard , Picard Lionel
Published: February 2020

The increasing energy storage demands of portable electronic devices and electric vehicles leads to the development of high performance lithium-ion batteries. Current technologies cannot reach the power and energy density requirements. More attention has been paid to the development of new electrode materials and electrolytes but performance continues to be limited. The strategy is to develop a 3D battery architecture. The planar configuration is locally reproduced within a 3D matrix. The surface area is increased and the distance between electrodes is reduced. Prieto, a start-up based in Colorado, proposed this new architecture in 2013. They have obtained a 3D anode/electrolyte configuration. However, complete integrated 3D battery shows fast cyclability failure due to the cathode configuration.

Our strategy is to start by the cathode. A metallic foam is used as the current collector and as the 3D matrix. A new synthesis to produce an optimized Li-ion cathode for this new battery configuration is presented. Either native metal, or the corresponding oxides, can be used as precursors for the synthesis of the lithiated transition metal oxides. The metallic surface is first oxidised and then lithiated. Alternatively, the metal surface can be directly lithiated. In both cases, the current collector, is directly furnished with active material without the need of either binders or conductive additives. Structural characterization was coupled with morphological analysis to understand the influence of oxide morphology on the synthesis and the lithiation mechanism. In addition, electrochemical characterizations will be presented.

A polymer electrolyte was then grafted directly to the cathode surface using electrochemical polymerisation. Electrochemical grafting enables the formation of a uniform, thin polymer electrolyte. A better electrode/electrolyte interface is obtained and ionic resistance are minimised. Furthermore, the porosity of the foam is available for anode materials. The effect of polymerization parameters of monomer concentration, solvent, applied potential and scanning rate were studied.

The foam porosity was filled with a low melting point metal that is used both as the anode and the current collector. Electrochemical characterization of this new configuration allows the assessment of the performance gain of this new architecture for lithium-ion batteries. Analysis of the battery interfaces (electrode/electrolyte, electrode/current collector) provide further insight into their influence on battery performance.
Criteria for Lithium “Dendrite” Propagation Evaluated in Single Crystal Solid Electrolytes
Authors: Park Richard , Swamy Tushar , Sheldon Brian W. , Rettenwander Daniel , Porz Lukas , Berendts Stefan , Uecker Reinhard , Carter W. Craig , Chiang Yet-Ming
Published: February 2020

Lithium is both the most electropositive and lightest metal, making it the ideal anode material. Non-flammable ceramic electrolytes paired with Li metal anodes could potentially result in safe, energy dense batteries surpassing state-of-the-art lithium ion batteries. Oxide solid electrolytes typically have high shear moduli, far beyond that of Li metal, which one criterion [1] suggests should suppress lithium metal dendrites. However, our group has recently shown that fracture of the solid electrolyte initiating at surface defects can create pathways for dendritic growth of metallic Li that short-circuit the device. [2]

In this work, in-situ optical microscopy has been conducted to characterize the propagation of Li dendrites through single crystal solid electrolytes under a variety of electrochemical conditions. The complete absence of grain boundaries excludes that class of internal defects as paths for propagation. A unique morphological structure of the lithium dendrite observed within the single crystal support a Griffith flaw based fracture model, and in addition, suggest a local field-intensification mechanism of dendrite growth within the solid. Results for the single crystals compared to those from polycrystalline solid electrolytes, in literature and from our own work.

Additionally, it is shown that the initiation of Li propagation through single crystals may be affected by the electrode geometry. Under certain circumstances, Li infiltration is observed to initiate at the perimeter of the electronic conductor contact with the electrolyte – especially at corners with high local curvature. This behavior suggests that localized field and current concentration is also important, and may determine which supercritical surface sites dominate Li metal propagation during electrodeposition.

Reference
s
:

[1] Monroe, C. & Newman, J. The Impact of Elastic Deformation on Deposition Kinetics at Lithium/Polymer Interfaces. J. Electrochem. Soc. 152, 396–404 (2005).

[2] Porz, L. et al. Mechanism of Lithium Metal Penetration through Inorganic Solid Electrolytes. Adv. Energy Mater. 1701003, 1–12 (2017).

Figure 1
Wire-Shaped Li-Ion Battery Based on Iron Sulfide Nanostructures on Carbon Based Electrode
Authors: Gibertini Eugenio , Panzeri Gabriele , Accogli Alessandra , Magagnin Luca
Published: February 2020

In recent years, the development of new materials, electrode architectures and manufacturing strategies has opened Li-ion batteries to new application areas. In particular, the implementation of high-performances and reliable energy storage devices is a challenging task in the sector of smart-fabrics and wearable electronics. Wire-shaped batteries (WSBs) are one of the most active and rapidly growing research fields, because of their flexibility and easy integration in fabrics. The development of a suitable technique for the production of graphene fibers as electrodes boosted the interest in WSBs [1]. Typically, Li-ion WSBs rely on self-supported all-carbon electrodes made of reduced graphene oxide (RGO) and/or carbon nanotubes (CNTs) fibers [2], synthesized through the wet-spinning process. The incorporation of higher capacity active materials in carbon fibers like TiO2 nanosheets [3], SiO2 [4] and S nanoparticles [5,6] has already been demonstrated as a successful strategy to further increase battery performances. However, the incorporation of active material during the wet-spinning of the carbon-based fibers limits this technique to 2D materials only. Here, we propose Li-ion WSB based on RGO fibers electrode and iron sulfide. Iron nanostructures have been deposited on RGO fibers by an easy electrochemical route and converted in iron sulfide as active material through sulfurization process by thermal treatment in presence of sulfur. Half-cell configuration with Li wire as cathode has been evaluated as well as a full-cell configuration. Electrochemical stability of the active materials were investigated through cyclic voltammetries while capacity, efficiency and cycle stability were evaluated for both half-cell and full-cell configurations. Morphological and structural investigations were performed on the electrodes by means of SEM, XRD and Raman analysis.

References

[1] Z. Xu, C. Gao, Nat. Commun. 2 (2011) 571

[2] Zhang, Ye, et al. "Super-stretchy lithium-ion battery based on carbon nanotube fiber." Journal of Materials Chemistry A 2.29 (2014): 11054-11059.

[3] Hoshide, Tatsumasa, et al. "Flexible Lithium-Ion Fiber Battery by the Regular Stacking of Two-Dimensional Titanium Oxide Nanosheets Hybridized with Reduced Graphene Oxide." Nano letters 17.6 (2017): 3543-3549.

[4] Rao, Jiangyu, et al. "A high performance wire-shaped flexible lithium-ion battery based on silicon nanoparticles within polypyrrole/twisted carbon fibers." RSC Advances 7.43 (2017): 26601-26607.

[5] Liu, Ruiqing, et al. "Flexible wire-shaped lithium-sulfur batteries with fibrous cathodes assembled via capillary action." Nano Energy 33 (2017): 325-333.

[6] Chong, Woon Gie, et al. "Lithium–Sulfur Battery Cable Made from Ultralight, Flexible Graphene/Carbon Nanotube/Sulfur Composite Fibers." Advanced Functional Materials 27.4 (2017).
In-Situ AFM Measurements on Lithium Metal Anodes
Authors: Benning Svenja , Hausen Florian
Published: February 2020

Using lithium metal electrode for the next generation of Lithium Ion Batteries (LIB) possesses the advantage of high energy around 300 Wh/kg coupled with progressed cathode material [1]. However, the formation of lithium dendrites and mossy lithium under electrochemical load (cycling) are currently the major hindrance of a wider use of such material and commercialization of the concept. Recently, the aforementioned challenges have been analyzed by means of nuclear magnetic resonance and found [2]. Those formations lead to degradation processes which are not yet understood at the micro- and nanometer scale. Therefore, experiments with high spatial resolution under realistic conditions gaining a better understanding of such phenomena are of utmost importance. Based on the practical significance for various applications the in-situ atomic force microscopy (AFM) characterization under electrochemical load is a key to develop new devices with improved functionality. Within this contribution we present combined atomic force microscopy and cyclic voltammetry (CV) measurements of the electrode-electrolyte interface between lithium anode and LP 30 (LiPF6 in EC/DMC), a common electrolyte in conventional energy storage. Therefore, the simultaneous investigation of structural, electrochemical and mechanical properties under electrochemical conditions is demonstrated. We will discuss the formation of mossy lithium as well as the formation of dendrites within the in-situ AFM results. Our results shed light onto the small scale processes on lithium metal anodes for LIBs and path the way towards applicability of bare lithium as anode material.

References:

[1] J. Wandt et al, Energy Environ. Sci., 2015, 8, 1358

[2] S. Kayser et al., arXiv: 1710.02577, 2017

https://arxiv.org/ftp/arxiv/papers/1710/1710.02577.pdf