bluuebunny/crossref_metadata_2025_split huggingface dataset:
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
(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) 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) 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.