bluuebunny/crossref_metadata_2025_split huggingface dataset:
Pd-Pt Catalyst Layer Formation Based on Porous Si
Authors: Hayase Masanori 
Published: February 2020

Our group proposed a Si based miniature fuel cell that has both fuel channel and catalyst layer on a Si substrate[1]. Maximum power density reached 500 mW/cm2 at 313 K with H2-O2 supply, which is comparable to conventional state-of-the-art fuel cells. In the fabrication process, initially porous Si is formed by anodization in a HF solution, then the Si is replaced by Pt in a wet plating process, and a porous Pt catalyst layer is formed on a Si chip. The catalyst layer consists of Pt, and amount Pt is estimated to be 3.6 mg/cm2, while typical conventional fuel cells use only 0.1 mg/cm2. We have to reduce the amount of Pt for practical use of the miniature fuel cell.
We found that porous Pd layer can be also made with almost identical process to the porous Pt formation, and have discussed Pd-Pt catalyst for reduction of the Pt usage in our miniature fuel cells. In this study, slight Pt was deposited on the porous Pd, and prototype fuel cells showed increase of power output by only 0.01mg/cm2Pt deposition. Furthermore, the Pd-Pt catalyst showed promissing result to CO poisoning.
[1] M. Hayase, T. Fujii, J. G. A. Brito-Neto, J
. Electrochem
. Soc
., 158(4), B355-359 (2011)
Low Stress and High Ductility Copper Electroplating Additive Development
Authors: Wei Lingyun , Kao Yu Hua , Hazebrouck Rebecca , Corona Robert , Lieb Bryan , Wang Ying , Lowe Michael A. , Lefebvre Mark , Pyo Sung-Ho , Tachikawa Wataru , Calvert Jeffrey 
Published: February 2020

Copper electroplating is one of the most important metallization technologies to produce metal contacts in the fabrication of crystalline silicon solar cells. It has been adopted in three areas, including: Interdigited Back Contact cell (IBC); Heterojunction with Intrinsic Thin layer (HIT); and Fully Plated Front Contact solar cells. Due to cost concerns, significant changes have been made in the silicon manufacturing process leading to thinner Si wafers. This change brings many challenges for copper metallization. One of the biggest challenges is to maintain a low internal stress of the copper deposit. This is key to avoid solar wafer warpage and maintain good adhesion. Copper deposits with high ductility are also desired to prevent or reduce the potential for the copper deposit to crack under stress over time. Ideal copper deposits exhibit low internal stress and high ductility. However, development of this plating chemistry is a challenge for the material supplier, as improvement in one attribute typically comes at the expense of another. Accordingly, there is need to develop organic additives for copper electroplating baths that alleviate internal stress in copper deposits as well as providing good ductility. In this paper, the performance of new acid copper electroplating bath capable of achieving both low internal stress and good ductility will be highlighted. Additive impact on copper deposit material properties and correlation between these properties and performance will be discussed
Electrical Studies on Parylene-C Columnar Microfibrous Thin Films
Authors: Khawaji Ibrahim H , Chindam Chandraprakash , Orfali Wasim , Awadelkarim Osama Osman , Lakhtakia Akhlesh 
Published: February 2020

Future advances in solid-state device technology are dependent on innovations in multifunctional materials and novel deposition processes and, hence, a wide spectrum of new material compositions and morphologies are being explored. For this study, microfibrous thin films (µFTFs) of Parylene C [1,2] were deposited on top of p-type Si substrates using physicochemical vapor deposition in a PDS2010 Labcoater to form metal-insulator–semiconductor (MIS) and metal–insulator–metal (MIM) capacitor structures utilizing the Parylene-C µFTF as the gate dielectric. Each µFTF was deposited with a collimated vapor flux of Parylene-C monomers inclined at 60° to the substrate plane and had a thickness of about 100 µm. The Parylene-C µFTFs were characterized for electrical properties and dielectric integrity using leakage current, equivalent series resistance and reactance, capacitance measurements at temperatures ranging from –40 °C to 125 °C and frequencies ranging from 1 kHz to 1 MHz, as well as field-emission scanning electron microscopy. The observed variations in leakage current can be explained in terms of transport mechanisms involving thermionic emission and electron hopping. Capacitance and dielectric loss data were analyzed. We found that higher leakage current does not allow for a reliable estimation of the dielectric constant.
[1] Pursel, S., Horn, M. W., Demirel, M. C., & Lakhtakia, A. (2005). Growth of sculptured polymer submicronwire assemblies by vapor deposition, Polymer, 46(23), 9544–9548.
[2] Chindam, C., Wonderling, N. M., Lakhtakia, A., Awadelkarim, O. O., & Orfali, W. (2015). Microfiber inclination, crystallinity, and water wettability of microfibrous thin-film substrates of Parylene C in relation to the direction of the monomer vapor during fabrication, Applied Surface Science, 345(1), 145–155.
Electroless Deposition of Ferromagnetic CoxFe1-x alloys Using Metal Ion Reducing Agent
Authors: Joi Aniruddha , Chen Ernest , Dordi Yezdi 
Published: February 2020

21st century computing applications such as big-data analytics, cloud-based computing, etc., require enormous memory capacity. Shuttling large amounts of information between numerous levels of interconnects and memory hierarchies that are necessary for these kind of applications incurs substantial latency and energy costs which is not suitable for today’s low-power, high performance devices. A different approach that is being considered involves inserting low-power non-volatile memory cells closer to logic/processor for faster and more efficient processing1 in so-called ‘monolithic integration’. Due to its low power and high endurance, spin-based (spin-torque transfer, spin Hall effect) 2, 3 memories have recently gained attention. In spin-torque transfer memories, information is stored in the spin orientation of a soft ferromagnetic layer, typically a CoFe or CoFeB alloy. A spin-polarized current is used to change the spin orientation in the ferromagnetic layer either ‘up’ or ‘down’, providing the binary states. This memory stack is usually formed by a subtractive process. Individual stacks are deposited by physical vapor deposition followed by reactive ion etching to obtain the memory cells. Alternatively, an additive process where the ferromagnetic layers are selectively deposited can be proposed. The additive scheme does not have some of the negative consequences associated with subtractive processes such as non-uniform profile, re-deposition of etch by-products and difficulties in scaling. Here, we demonstrate a selective deposition process for CoxFe1-x (x=0-1) ferromagnetic alloy enabled by electroless deposition. Trivalent TiCl3 is used as a reducing agent which facilitates growth of crystalline and contaminant-free (such as B or P) film even at room temperature. Electrochemical characterization of the oxidation and reduction half-reactions are presented and are used to rationally design the electrolyte. X-ray photoelectron spectroscopy (XPS) characterization indicates the presence of metallic Co and Fe in the bulk of the deposit. Finally, the magnetic properties of the CoFe film are investigated using vibrating sample magnetometer (VSM). Electroless deposited CoFe thin films demonstrate magneto-crystalline anisotropy with distinct easy and hard axes and high saturation moment. Effect of heat treatment and surface capping on magnetic properties are also discussed. Finally, some challenges involving integration of such an additive process is highlighted along with possible solutions.
Figure 1: XPS characterization of the CoFe film deposited on a PVD Cu substrate. Carbon and oxygen are mainly present at the surface and not shown for clarity. Chemical state analysis indicates presence of metallic Co and Fe in the bulk film.
References:

H.-S. P. Wong and S. Salahuddin, Nat. Nanotech. 10 (2015)

S. Ikeda, K. Miura, H. Yamamoto et al, Nat. Mater. 9 (2010)

L. Liu, C-F. Pai, Y. Li et al, Science 336 (2012)

Figure 1
Non-Thermal Equilibrium Formation of Ge1-xSnx (0≤x≤0.2) Crystals on Insulator by Pulsed Laser Annealing
Authors: Moto Kenta , Matsumura Ryo , Chikita Hironori , Sadoh Taizoh , Ikenoue Hiroshi , Miyao Masanobu 
Published: February 2020

Introduction

Formation of crystalline GeSn film on insulator with high Sn concentration exceeding thermal equilibrium solid-solubility is strongly expected to realize high-speed thin film transistors. To explore non-thermal equilibrium processing [1], we examined crystallization of amorphous-GeSn (a-GeSn) with various modulated Sn concentration by pulsed laser annealing (PLA). In the present study, we focus on the influence of the Sn concentration on crystallization of a-GeSn by PLA.

Experimental Procedure

Schematic sample structure and PLA conditions are shown in Fig.1. A-Ge1-xSnx (0≦x≦0.2) films (thickness: 100 nm) were deposited on quartz substrates by a molecular beam technique. These samples were irradiated with a pulsed laser (energy : 10 - 230 mJ/cm2, pulse period : 1 sec, pulse number : 100 shot). The laser annealed regions were analyzed by Nomarski microscopy and Raman scattering spectroscopy.

Results and Discussion

Nomarski micrograph and Raman spectra of Ge0.8Sn0.2 samples before and after PLA with various energy are summarized in Fig. 2. In the samples after PLA, the contrast-changed regions were observed, compared with the as-deposited sample. Here, the contrast becomes stronger with increasing energy from 50 mJ/cm2 to 170 mJ/cm2, and finally the GeSn layer was damaged for energy of 230 mJ/cm2. Raman spectra reveales that Ge0.8Sn0.2 is crystallized on insulating substrates by 50 - 170 mJ/cm2 PLA.
The process-window to achieve crystalline GeSn is summarized in Fig. 3(a), where the energy for starting crystallization and the energy just before damaging are indicated as Ecryst. and Edamage , respectively. Substitutional Sn concentration estimated from shift of Ge-Ge peak obtained by Raman measurements is shown in Fig. 3(b). The process window necessary for crystallization is significantly expanded by introducing Sn, i.e. 16 mJ/cm2 for Ge, ~ 130 mJ/cm2 for GeSn.
High Sn concentration exceeding thermal equilibrium solid-solubility is obtained by PLA, for all GeSn samples. Interestingly, for samples with initial Sn concentration of 5 % and 10 %, almost all Sn atoms are incorporated into substitutional site, while for 20 % sample, only half of Sn atoms are incorporated into substitutional site. The detailed physics will be discussed in the presentation.

References

[1] M. Kurosawa, et al., Appl. Phys. Lett. 104, 061901 (2014).

Figure 1
A Study on Chamber Contamination Control of Rapid Thermal Nitridation Process By Applying Quartz Liner
Authors: Yun Jin Hyuk , Park Se Geun , Kang Byung Je , Lee Young Ho , An Jung Su , Cho In Su 
Published: February 2020

To improve the characteristics of barrier wall in DRAM plug contact via, the rapid thermal nitridation(RTN) process has been widely used via rapid thermal process chamber. With combination of high temperature heat, process gas such as NH3 and wafer being processed, the Ammonium Chloride(NH4Cl) is generated as a byproduct of this process and chamber is contaminated by NH4Cl depositing on the reflector. This contaminant diffracts the thermal energy which comes into pyrometers and degrades process quality. To prevent this chamber contamination from the byproduct such as NH4Cl, the transparent quartz liner on reflector plate is adopted.
In this study, the influence of quartz liner on reflector plate, the improvement of chamber contamination and pyrometer sensitivity were investigated.
In RTN process, TiSix or CoSix is formed in Si contract area as an ohmic contact and improves the adhesion with tungsten by transducing Ti to TiN.[1]
Eq.1 shows how Ammonium Chloride (NH4Cl(s)) is generated during RTN process as a byproduct.
NH4Cl sublimes at 337.6°C and the reflector plate increases no more than 225.3°C at 1000°C, 90sec process condition. Therefore NH4Cl is deposited on the chamber wall as well as reflector plate. Fig.1 shows the diagram of NH4Cl deposition on reflector plate as a contaminant. This contaminant diffracts the thermal energy which comes into pyrometers and degrades the silicide uniformity.
In Fig.2, device “A” at target temperature has more uniform shape than device “B” which has been processed in lower temperature than target of “A”.
Fig.3 shows transparent quartz in RTP chamber to prevent reflector plate from the contaminant.
Fig.4 shows presence of quartz liner has very stable halogen lamps power dissipation than without quartz.
Fig.5 shows temperature error against target value with quartz liner is much lower than without quartz.
In this paper, the influence of quartz liner on reflector plate, the improvement of chamber contamination and pyrometer sensitivity were investigated. From experimental result, presence of quartz liner protects reflector plate from contamination and keeps power dissipation of halogen lamps in stable. As a result, it means that more accurate heat control is possible in RTN process which could affect the quality of plug contacts of semiconductor device.
Reference
[1] ] Zhao Wenbin, Chen Haifeng, XiaoZhiqiang, Li leilei, Yu Zongguang, Journal of Semiconductors (2009) 056001

Figure 1
Atomic Structure Evolution during First Charge of Layered-Layered Composite Lithium Ion Battery Cathode Materials
Authors: Iddir Hakim , Croy Jason R. , Gallagher Kevin G. , Johnson Christopher , Benedek Roy , Balasubramanian Mahalingam 
Published: February 2020

Layered-layered composites with composition xLi2MnO3•(1-x)LiMO2 enable high capacity and energy density Li-ion batteries, but suffer from degradation with cycling. Evidence of atomic instabilities during the first charge are addressed in this work with X-ray absorption spectroscopy, first principles simulation at the GGA+U level, and existing literature. The pristine material of composition xLi2MnO3•(1-x)LiMn0.5Ni0.5O2 is assumed in the simulations to have the form of LiMn2 stripes, alternating with NiMn stripes, in the metal layers. The charged state is simulated by removing Li from the Li layer, relaxing the resultant system by steepest descents, then allowing the structure to evolve by molecular dynamics at 1000 K, and finally relaxing the evolved system by steepest descents. The simulations show that about ¼ of the oxygen ions in the Li2MnO3 domains are displaced from their original lattice sites, and form oxygen-oxygen bonds, which significantly lowers the energy, relative to that of the starting structure in which the oxygen sublattice is intact. The oxygen displacement facilitates the displacement of about (1/3) of the (Li2MnO3 domain) Mn ions to migrate to the delithiated Li layers.
(Invited) A Mesoscale Approach Toward Elucidating Microstructure-Transport-Performance Interaction in Li-S Battery Electrodes
Authors: Mukherjee Partha P. , Liu Zhixiao , Chen Chien-Fan , Mistry Aashutosh 
Published: February 2020

Lithium-sulfur (Li-S) battery is a promising energy storage technology, which offers improved performance in terms of higher energy density and material sustainability owing to the abundance of sulfur (S) as the active material. However, one of the key challenges centers on insoluble discharge product formation in the cathode and concomitant internal shuttle effect [1-5]. The polysulfide (such as Li2S) formation poses a deleterious consequence on the electrode microstructural change, thereby impacting the transport and electrochemical properties and ultimately resulting in capacity fade.
In this regard, the cathode architecture plays an important role in determining the Li-S battery performance. A desirable electrode microstructure should effectively deter the dissolution of polysulfide, and facilitate lithium ion transport. This warrants a fundamental understanding of the physicochemical interplay resulting from the underlying microstructure-transport-performance interaction.
In this work, a mesoscale computational model, shown schematically in Fig.1, will be presented in order to fundamentally investigate the morphology evolution due to Li2S precipitation and the resulting influence on the electrode microstructural and performance attributes.

Acknowledgement:

Financial support from the U.S. Department of Energy, Office of Energy Efficiency and Renewable Energy, grant DE-EE0006832 (Program manager: Dr. Tien Duong) is gratefully acknowledged.

References:

1. P. G. Bruce, S. A. Freunberger, L. J. Hardwick, and J.-M. Tarascon, Nat Mater,
11(1), 19-29 (2012).
2. Y. Yang, G. Y. Zheng, and Y. Cui, Chem Soc Rev,
42(7), 3018-3032 (2013).
3. X. Ji, K. T. Lee, and L. F. Nazar, Nat Mater,
8(6), 500-506 (2009).
4. X. Ji, S. Evers, R. Black, and L. F. Nazar, Nat Commun,
2, 325 (2011).
5. Z. Liu, D. Hubble, P. B. Balbuena, and P. P. Mukherjee, Phys Chem Chem Phys, 17, 9032 (2015).

Figure 1
Thermal-Electrochemical Lithium-Ion Battery Simulations on Microstructure and Porous Electrode Scale
Authors: Latz Arnulf , Zausch Jochen 
Published: February 2020

Heat production within a battery cell is governed by local fluxes of ions and electrical currents in the microstructure of the battery electrodes. These fluxes on the other hand are strongly coupled with thermal transport, leading to a fully coupled reaction transport model for batteries [1]. It describes ion, charge and heat transport on the length scale of the microscopic active particles that build up an electrode. The implementation of the model in our simulation software BEST [2] allows simulations of transport and reactions in three-dimensionally fully resolved electrode structures. Ion concentration, potential and temperature are obtained in each spatial point of the simulation domain. Thus the dependence of battery performance, heat production and heat distribution in the electrode microstructure can be studied.
Due to its geometric complexity this approach is not viable for a simulation on cell scale. To this end effective or homogenized models are commonly employed [3]. By applying the volume-averaging technique to our thermal-electrochemical microscopic theory the corresponding thermal-electrochemical porous electrode theory can be derived [4]. Since volume-averaging neglects the details of the electrode structure it is obvious that ion fluxes and electrical currents cannot be recovered in detail. However, many heat sources of our model depend on the magnitude and distribution of these fluxes (e.g. Joule heating) and are strongly localized on the interfaces between electrolyte and active particles. It is therefore a priory not clear whether upscaled models of this type are at all useful for predictive cell scale simulations if heat production and temperature distribution is of interest.
In our contribution we will present the fully coupled thermal battery models for both micro and cell scale. We focus on a simulation study where we compare micro- with equivalent cell scale simulations based on the derived porous electrode theory. Whereas the numerically averaged results agree very well with the results of porous electrode theory, strong fluctuations around this average (e.g. of the overpotential) are observed in microstructures. Especially for the prediction of degradation phenomena, these fluctuations are crucial and cannot be recovered in porous electrode theory. Our results raise the question to which extent porous electrode theory can be used to predict degradation phenomena in batteries.
[1] A. Latz and J. Zausch, Journal of Power Sources 196 (2011) 3296.
[2] www.itwm.fraunhofer.de/best
[3] J. Newman and W. Tiedemann, AIChE 21, (1975) 25.
[4] A. Latz, J. Zausch, Multiscale modeling of lithium ion batteries : thermal aspects, Beilstein J. Nanotechnol. 6 (2015) 987–1007. doi:10.3762/bjnano.6.102.
A Computational Model for Sodium Sulfur Battery Analysis
Authors: Sezer Hayri , Aygun Mehmet , Mason Jerry Hunter , Baran Engin , Celik Ismail Bektas 
Published: February 2020

Energy storage from the renewable energy sources is one of the challenging issue of clean energy technologies. Recently, sodium sulfur (Na-S) battery has gained considerable attention as a viable candidate of energy storage application. However, Na-S battery technology comes with the disadvantages of relatively high temperature operating conditions, brittle insulator and safety concern with regarded to temperature management. In this study, a two-dimensional heat transfer model is integrated with a zero-dimensional, transient electrochemical model for Na-S batteries to predict the temperature distribution inside the Na-S battery under cell operating conditions. Properties required for solving the heat transfer governing equation and electrochemical model, such as electronic and ionic conductivity, species concentrations and heat conductivity are calculated and updated as a function of time. Additionally, the instant outputs of these combined computational tool for single sodium sulfur battery, temperature, open circuit voltage, polarization and ohmic losses are used as input values for a designed Simulink model to analyze a stack of Na-S batteries. These computational tools aim to enable the thermal management and to complete design procedure of storage systems made of Na-S batteries. The present model is tested against experimental results found in literature. Good agreement is achieved between current model and the available experiment in the literature. Validated model is used to perform a parametric study.