bluuebunny/crossref_metadata_2025_split huggingface dataset:
(Invited) High-K Dielectrics: A Perspective on Applications from Silicon to 2D Materials
Authors: Wallace Robert M 
Published: February 2020

In the 1990’s, research accelerated on addressing the limits of the industry standard gate dielectric: SiO2. With the most aggressive integrated circuit scaling, it became clear that standby power for MOSFETs required the insertion of a gate dielectric material that reduced tunneling leakage while enabling performance expectations. Leveraging prior dielectric research and after exploring several dielectric material candidates, [1,2] Hf-based dielectrics became the dominant choice and were established in commercial Si technology fabrication processes in 2007 after at least a decade of research. [3] Although perhaps forgotten among today’s 3D FET technologies, the introduction of a new gate dielectric, simultaneously with metal gate materials, was considered quite revolutionary in its day, and this development, in conjunction with other device engineering aspects like strain, enabled the continued march of industry along Moore’s original predictions. Since that time, the research on incorporating high-k dielectrics has expanded to address alternative channel materials including Ge, III-V, wide band gap semiconductors, and, most recently, perhaps the ultimate limit in channel scaling – atomically thin 2D materials. This talk, from the author’s perspective, will review some of these developments, many presented at the annual ECS high-k gate dielectric symposia led by Prof. Kar, and provide some context on the resilience of the materials research as well as the challenges and opportunities that lie ahead.
This work is supported in part by: (i) the SWAN Center, a SRC center sponsored by the Nanoelectronics Research Initiative and NIST, (ii) the Center for Low Energy Systems Technology (LEAST), one of six centers supported by the STARnet phase of the Focus Center Research Program (FCRP), a Semiconductor Research Corporation program sponsored by MARCO and DARPA, (iii) the US/Ireland R&D Partnership (UNITE) under the NSF award ECCS-1407765, and (iv) the Erik Jonsson Distinguished Chair in the Erik Jonson School of Engineering and Computer Science at the University of Texas at Dallas.
[1] J. Robertson and R.M.Wallace, “High-K materials and metal gates for CMOS applications,” Materials Science and Engineering R, 88, 1-41 (2015)
[2] G.D.Wilk, R.M.Wallace, and J.M.Anthony, “High-k Gate Dielectrics: Current Status and Materials Properties Considerations”, Journal of Applied Physics
895243 (2001)
[3] M.T. Bohr, R.S. Chau, T. Ghani, K. Mistry, “The High-k Solution,” IEEE Spectrum. 44 (29) (2007).
Effect of Cu-Doped Switching Layer of Amorphous Carbon-Oxide Based Reram on Non-Volatile Memory Characteristics for Forming-Free Operation
Authors: Park Jea-Gun , Kim Hea-Jee , Song Myung-JIn , Kwon Ki-Hyun , Kim Dong-Won , Jin Soo-Min , Kim Do Jun , Yang Hun-Mo 
Published: February 2020

Resistive random access memory (ReRAM) is one of the candidates to alternate NAND flash memory due to its potential scalability, fast switching speed and low operating power [1]. However, for ReRAM in general, high-voltage forming process is needed to initiate the switching, which normally lead to high power consumption and operational complexity [2]. Therefore, the forming-free operation of ReRAM has been researched globally. In this work, to overcome this high voltage forming operation, the effect of Cu-doping on switching layer of amorphous carbon-oxide ReRAM was studied. ReRAM was fabricated with the structure of tungsten (W) / Cu-doped amorphous carbon oxide / hafnium oxide (HfO2) / platinum (Pt). The buffer layer, hafnium oxide, was inserted to decrease the current level increased excessively due to Cu-doping. It was confirmed that Cu-doping decreased forming voltage and increased memory margin. As comparing the characteristics of the ReRAM with and without Cu-doping at 34-nm pattern size, the forming voltage of Cu-doped ReRAM decreased from 2.7 to 1.95 V and also set voltage of that decreased a little from 1.8 to 1.65 V. From I-V characteristic graph, Cu-doped ReRAM demonstrated that the forming voltage was similar to the set voltage, indicating for the possibility of forming free operation. In addition, the memory margin of that was enlarged from 1.62×102 to 2.64×103. Besides, both of the devices had 106AC endurance cycles, which were excellent performance compared with other ReRAM devices. In our presentation, we report the effect of Cu-doping on electrical characteristics and the switching mechanism by using various analysis tools such as transmission electron microscopy (TEM).

* This material is based upon work supported by the Ministry of Trade, Industry & Energy (MOTIE, Korea) under Industrial Technology Innovation Program (10068055).

[1] Li Ji; Integrated one diode-one resister architecture in nanopillar SiOxresistive switching memory by nanosphere lithography. Nano Lett. 2014, 14, 813-818
[2] Ruomeng Huang; Forming-free resistive switching of tunable ZnO films grown by atomic layer deposition. Microelectron. Eng. 2016, 161, 7-12

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Investigation of Degradation of Organometal Halide Perovskite Film and Solar Cell
Authors: Al Mamun Abdullah , Mohammed Yousuf , Ava Tanzila Tasnim , Baumgart Helmut , Elmustafa A A , Namkoong Gon 
Published: February 2020

Organometal hybrid perovskite material has emerged as an attractive competitor in the field of photovoltaics due to its promising potential of low-cost and high-efficiency photovoltaic applications. Although organometal halide perovskite solar cell shows great potential to meet future energy needs, the degradation raises serious questions about its commercialization viability. At present, the stability of perovskite solar cells has been studied in various environmental conditions. Nonetheless, an understanding of the degradation and its performance of CH3NH3PbI3-xClx perovskite solar cell is limited.
Herein, we report the mechanical and structural degradation of CH3NH3PbI3-xClx perovskite films at room temperature as a function of time and thermal instability of perovskite solar cells during the heating and cooling processes. For mechanical degradation measurement, we used nanoindentation for CH3NH3PbI3-xClx perovskite films fabricated on FTO/PEDOT:PSS substrate. The hardness and elastic modulus of perovskite films were measured as a function of time. In addition, the mechanical degradation of perovskite thin films was correlated with X-ray diffraction, steady-state and time-resolved photoluminescence (PL). We also investigated the thermal instability of perovskite thin films and the irreversible performance of perovskite solar cells. Particularly, the irreversible performance of CH3NH3PbI3-xClx was analyzed by measuring the development of crystallinity, charge trapping/detrapping, trap depth, and PbI- phase while varying the temperature of perovskite films and solar cells between room temperature and 82 °C. Surprisingly, we found that the degradation of both perovskite films and solar cells occurred at ~70°C. Remarkably, even after the perovskite solar cell temperature cooled down to room temperature, the performance of solar cells continuously degraded. The underlying mechanism of irreversibly degraded performance of perovskite films and solar cells were explained in terms of the development of phase separation, increased trapping rates and deep trap depth of defect states of perovskite films.
Development of Sputter Processed Perovskite Films Toward Tandem Solar Cells
Authors: Raifuku Itaru , Ishikawa Yasuaki , Bourgeteau Tiphaine , Ito Seigo , Bonnassieux Yvan , Cabarrocas Pere Roca i , Uraoka Yukiharu 
Published: February 2020

Tandem solar cells which combines several solar cells in series have been investigated to achieve high efficiency solar cells. Recently, perovskite/crystalline silicon tandem solar cells have attracted much attention as promising tandem structure because these solar cells have high external quantum efficiency in different wavelength range. There is a report on simulated efficiency of two terminal perovskite/crystalline silicon tandem solar cells. In that report, projected efficiency of over 30% is suggested by using inverted pyramid structure. However, most of perovskite solar cells are fabricated by solution process which is not suitable way for textured substrates, indicating that it is difficult to achieve such structured tandem solar cells in current conventional process. To overcome this problem, we focused on sputtering process. Sputtering can achieve homogeneous films even the substrate has large roughness such as textured substrates. Therefore, it is expected that sputtering is suitable method to achieve high efficient tandem solar cells. In addition, there are no reports on sputtered perovskite films which are used for solar cells. In this work, we fabricated perovskite films by sputtering and investigated the characteristics.
In this work, we tried to fabricate CH3NH3PbI3 perovskite films which is commonly used as light absorber. The perovskite films were obtained from sputtered PbI2 films. PbI2 sputtering target was fabricated from PbI2 powder using a pressing under 10 MPa on stainless plate. Then, PbI2 films were deposited on glass substrates by RF sputtering using the PbI2 target. The sputtering condition was Ar atmosphere, under 1 Pa at room temperature. Perovskite films were obtained by reacting sputtered the PbI2 films and CH3NH3I gas in petri dish. The obtained perovskite films were characterized by X-ray diffraction (XRD) measurement and scanning electron microscopy (SEM) observation.
Figure 1 shows XRD pattern of a perovskite film obtained from sputtered PbI2 film. Sputter processed perovskite films showed typical diffraction patterns of CH3NH3PbI3 perovskite films and had similar peaks to solution processed perovskite films.
Figure 2 shows a cross sectional SEM image of a PbI2 film sputtered on fluorine-doped tin oxide (FTO) and TiO2 coated glass substrate. This image clearly indicates that homogeneous PbI2 and/or perovskite films could be fabricated by sputtering even if the substrates have large roughness. This result suggested sputtering is promising process to achieve high efficiency tandem solar cells.

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Ni Alloy Monolayer Electrodeposition
Authors: Allongue Philippe , Maroun Fouad , Damian Alexis , LeCadre Florian 
Published: February 2020

The morphology and the microstructure of alloys grown by co-electrodeposition generally result from kinetics and depart from equilibrium. On the atomic scale key parameters include binding energies (e.g. adatom – surface, adatom – adatom etc.) and also on adatom mobility.
In this presentation we will examine the impact of above parameters on Ni alloy monolayers electrodeposition. An unreconstructed AuPd(111) substrate is used to co-deposit Ni and Ag, Au [1] and Pd [2]. These elements were chosen because they present different bulk mixing enthalpies with Ni, from phase separation (Ag) to perfect mixing (Pd). These three elements present also quite different surface mobility. Complementary experiments in which the two metals are sequentially deposited [3] [4] as well as dealloying experiments (selective dissolution of Ni) [5] will be presented in support of discussion. References :
[1] F. Lecadre et al. AuNi alloy monolayer films electrodeposited on Au(111): An in situ STM study, Surf. Sci. 607, 25 (2013).
[2] A. Damian et al. Electrodeposition of NiPd monolayer on Au(111): An in situ scanning tunneling microscopy study, Electrochim. Acta 112, 824 (2013).
[3] A. Damian et al. Selective Growth and Dissolution of Ni on a PdAu Bimetallic Surface by In Situ STM: Determining the Relative Adsorbate-Substrate Interaction Energy, Phys. Rev. Lett. 102, 196101 (2009).
[4] F. Lecadre et al. Electrodeposition of Ag, Pd and Au on Ni monolayer islands on (1 × 1)-Au(111) by in-situ scanning tunneling microscopy, Electrochim. Acta 197, 241 (2016).
[5] A. Damian et al. Electrochemical de-alloying in two dimensions: role of the local atomic environment, Nanoscale 8, 13985 (2016).
Electrodeposition of Nickel on Titanium in Aqueous Acidic Electrolytes
Authors: Jensen Mats , Haarberg Geir Martin , Seland Frode , Sunde Svein , Ratvik Arne Petter 
Published: February 2020

Nickel may be produced in acidic chloride-sulfate based electrolytes. Nickel is initially deposited on stainless steel or titanium cathodes to produce starting sheets while chlorine gas is evolved on DSA anodes. Stress in the nickel deposit may cause bending of the cathode sheet. In addition, irregular growth such as dendrite formation may occur. In extreme cases, short-circuiting of electrodes will happen. Fundamental electrochemical studies of the initial stages of the electrodeposition process may give valuable information for obtaining smooth nickel deposits.
Electrochemical experiments of nickel deposition were carried out on titanium substrates using cyclic voltammetry and potential step, and examined with SEM imaging. The measurements were performed at different deposition potentials and times to get an overall picture of the nucleation and growth of nickel on titanium substrates. Further deposition studies have been performed using in situ AFM to study the whole process from single nickel nuclei to a cohesive layer, and determine the nucleation mode and characteristics. The effects of electrolyte composition and pH will be presented.
The pre-treatment of the substrate is important for the nucleation and properties of the nickel deposit. The figure illustrates the different nucleation overpotential for a smooth and rough titanium substrate.

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Aging Mechanisms in Electrodeposited Cobalt-Hardened Gold Coatings
Authors: Banga Dhego 
Published: February 2020

Electrodeposited cobalt-hardened gold (Au(Co)) coatings are used on electrical connectors and contacts requiring resistance to mechanical wear as well as low electrical contact resistance. However, conventionally electrodeposited Au(Co) films grown using direct current (DC) electroplating method possess complex, porous microstructures. An open question is how this porosity affects the susceptibility of these coatings to potential electrical and mechanical failure. To test the hypothesis that microstructural voids degrade the coating stability, we conducted an elevated temperature aging study to compare Au(Co) grown with a void microstructure, using conventional deposition processes, with Au(Co) grown without a void microstructure, using a new pulsed-plating process developed at Sandia national laboratories. Using characterization techniques including scanning electron microscopy, transmission electron microscopy, transmission Kikuchi diffraction, atomic force microscopy, sheet resistance measurements, nanoindentation, and atom-probe tomography, we will demonstrate how porous coatings degrade by coarsening of voids, reactions of coatings with substrates, and diffusion of the hardening agent Co from the film to the substrate/coating interface with increased annealing temperature which in turn negatively affect the coatings’ structural integrity and the stability of electrical and mechanical properties. In contrast, we will show that non-porous Au(Co) coatings display stable low resistance, surface morphology, interface with substrates, and no development of voids or diffusion of Co in the microstructure with increased annealing temperature.

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The Effect of Levelers on Plating through Holes of a PCB By Using Reduced Graphene Oxide (rGO) As a Conducting Layer
Authors: Chang I-Hsuan , Dow Wei-Ping 
Published: February 2020

Electroless (ELS) copper plating process has been commonly used in the metallization process of printed circuit boards (PCBs), because the sidewalls of the through holes (THs) of PCBs are composited of resin and glass fiber, which are not conductive materials. Hence, before plating these THs, their sidewalls have to be metallized by ELS copper plating. The process causes harmful influence to environment because it contains precious metal (i.e., Pd as a catalyst), formaldehyde and chelating agents. However, reduced graphene oxide (rGO) grafting process, proposed in this work, is environment-friendly and can replace the ELS copper plating process to make the sidewall of the TH of a PCB be conductive for copper electroplating. The rGO grafting process has less steps and an environment-friendly formulation. In this work, the rGO is grafted on the sidewalls of THs of a PCB with a high aspect ratio (AR). We observed that the copper nucleation mechanism of electrochemical deposition on a PCB is progressive. In addition, we studied the suppression of various levelers on copper electrodeposition in order to control the copper to be less deposited at the hole opening but much more deposited at the hole center. Finally, the throwing power (TP) of the copper electrodeposition in the TH can be significantly enhanced.
In our research, the effects of electroplating baths, operating parameters and electroplating additives, especially levelers, were investigated for obtaining a high TP of THs. On the other hand, the suppression of various levelers was evaluated by electrochemical analysis, such as linear sweep voltammetry (LSV) and galvanostatic measurements. The results indicate that the electroplating bath containing the leveler with stronger suppression can control the copper to be specifically deposited at the hole opening. Hence, a high TP of plating TH was achieved by using the rGO process. Moreover, the plated TH can pass thermal shock test. That means, a brand-new and promising rGO process can replace the ELS copper plating in the future for producing advanced electronic products.
Electrochemical Formation of Dy and Nd Alloys Using Liquid Metal Electrodes in Molten LiCl-KCl Systems
Authors: Konishi Hirokazu , Ono Hideki , Nohira Toshiyuki , Oishi Tetsuo 
Published: February 2020

We proposed new separation and recovery process for RE metals from Nd magnet scraps using molten salt electrolysis and an alloy diaphragm. This new process was first applied to chloride melts, and the separation of Dy and Nd were investigated using Ni cathodic electrodes in molten LiCl-KCl-DyCl3-NdCl3 systems. The highest mass ratio of Dy/Nd in Dy-Nd-Ni alloy samples was found to be 72.
We focused on the liquid metals as the alloy diaphragms. Liquid metals have higher diffusion rates of elements than those of solid metals during the electrolysis. In this work, Bi, Sn and Zn electrodes were used as liquid metal electrodes. The alloy samples were prepared by potentiostatic electrolysis using liquid Bi, Sn and Zn electrodes in molten LiCl-KCl added DyCl3(0.50 mol%) and NdCl3(0.50 mol%) at 723 K.
Layered-to-Spinel Phase Transformation of Li2MnO3 during the Initial Charge
Authors: Shimoda Keiji , Matsunaga Toshiyuki , Murakami Miwa , Arai Hajime , Uchimoto Yoshiharu , Matsubara Eiichiro , Ogumi Zempachi 
Published: February 2020

Lithium- and Manganese-Rich layered oxides (LMRs) are one of the promising candidates of positive electrode materials for the advanced LIB due to their high reversible capacities. The chemical formula is often described as xLi2MnO3•(1–x)LiMO2 that consists of Li2MnO3- and LiMO2-rich nano-domains. The LMR-based electrodes show a voltage plateau at ca. 4.5 V in the initial charge process, which leads to an irreversible capacity. This plateau is understood to appear for the activation of Li2MnO3.[1,2] This activation process is not thoroughly understood yet and the elucidation of this reaction would lead to the practical use of this material. Some groups have reported that the charge compensation on the delithiation from Li2MnO3 is associated with the oxidation of oxide ion including O2release from the structure.[3,4] The present work focuses on clarifying the structural changes taking place inside LMR bulk at the initial delithiation (charge) using SR-X ray diffraction, STEM, and solid-state NMR.[5]
SR-XRD profiles showed that all the diffraction intensities were gradually decreased and broadened during the initial charge up to 4.8 V, which indicated that the initial delithiation caused the change to highly disordered material. The high-resolution 6Li MAS NMR spectra showed that Li+ was monotonously extracted from both the Li and TM layers. EELS mapping by STEM suggested that the Li+extraction from the sample of 50% SOC occurred in a biphasic manner inside a single particle. The lattice structures of the active material after charge-discharge cycle was also examined on samples at the 20th discharged and 21stcharged states.
This work was supported by the Research and Development Initiative for Scientific Innovation of New Generation Batteries (RISING) and the Research and Development Initiative for Scientific Innovation of New Generation Batteries II (RISING II) projects from the New Energy and Industrial Technology Development Organization (NEDO), Japan.
[1] Thackeray et al., J. Mater. Chem., 2007, 17, 3112.
[2] Yu & Zhou, J. Phys. Chem. Lett., 2013, 4, 1268.
[3] Yu et al., J. Electrochem. Soc., 2009, 156, A417.
[4] Oishi et al., J. Mater. Chem. A, 2016, 4, 9293.
[5] Shimoda et al., J. Mater. Chem. A, 2017, 5, 6695.
(Invited) Wetting, Adhesion and Stiction of 2D Materials
Authors: Mertens Stijn F. L. 
Published: February 2020

The wetting properties of surfaces, including the adhesion and stiction (static friction) of liquid drops, are critical for processing materials and post-production problems such as fouling. With the emergence of 2D materials such as graphene and hexagonal boron nitride, the interaction of liquids with one-atom-thick matter and its support poses new challenges in our understanding of wetting.
In my talk, I shall present an overview of recent research in this area, ranging from wetting transparency and translucency of graphene [1,2] to electrochemically switchable wetting and adhesion of hexagonal boron nitride [3].
[1] J. Rafiee, X. Mi, H. Gullapalli, A.V. Thomas, F. Yavari, Y.F. Shi, P.M. Ajayan, N.A. Koratkar, Nat. Mater. 11 (2012) 217–222.
[2] C.J. Shih, M.S. Strano, D. Blankschtein, Nat. Mater. 11 (2013) 866–869.
[3] S.F.L. Mertens, A. Hemmi, S. Muff, O. Gröning, S. De Feyter, J. Osterwalder, T. Greber, Nature 534 (2016) 676–679.

Figure: Electrochemical hydrogen intercalation flattens a monolayer of hexagonal boron nitride on Rh(111) and changes advancing (1) and receding (2) contact angles

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