bluuebunny/crossref_metadata_2025_split huggingface dataset:
(Invited) Relationship between Ferroelectricity and Electrical Breakdown in Hf-Zr-O Thin Films
Authors: Migita Shinji 
Published: February 2020

Hafnium oxide ferroelectrics are expected in the applications of high-density memories and ferroelectric-gate FETs integrated on LSI. A distinct feature of hafnium oxide ferroelectric is the large coercive field, as large as 1 MV/cm. It is more than tenfold larger than those of conventional perovskite oxide ferroelectrics. This large coercive field is beneficial to preserve a wide memory window in ultrathin films, e.g. 2 V in 10-nm-thickness film. At the same time, it brings a concern of dielectric breakdown during operation because of the high electric field applied in the film. Thus we studied the relationship between the coercive field and breakdown field in ferroelectric Hf-Zr-O thin films.
Metal-ferroelectric-metal (MFM) capacitors were prepared on heavily doped Si substrates. Metal layers were made of TaN film prepared by sputtering the Ta target in Ar and N2 mixture gas. Hf-Zr-O films were prepared by sputtering the HfO2 and ZrO2 targets simultaneously. The metal composition was controlled by shuttering the targets frequently within 0.5-nm-thick of deposition cycle. Following to the deposition of bottom TaN (10 nm), Hf-Zr-O, and top TaN (10 nm) films in sequence, the samples were annealed in a vacuum condition between 600 and 800 degrees Celsius. Device fabrication was finished by photolithography and dry etching.
A result of electrical characteristics of an MFM capacitor, made of 10-nm-thick Hf-Zr-O film (Hf:Zr=50:50), is shown in the figure. Polarization-voltage characters (blue curves) are shown with the left axis. Polarization becomes prominent when the voltage swing exceeds +1 and -1 V. The maximum voltage reaches +3 and -3 V in order to obtain a fully saturated behavior. The remnant polarization and the coercive field are calculated to be 21.9 μC/cm2 and 0.97 MV/cm. These values are reasonable with the results in preceding reports. Current-voltage characters (red curves) shown with the right axis were measured using another die on the same wafer. The leakage current increases gradually with the applied voltage, and the breakdown occurs at around 4 V. The breakdown voltage is larger than the maximum voltage for the saturated polarization, but it is not large enough for the stable operation. In the application of this ferroelectric oxide, we must pay attention with this balance.
Hafnium oxide ferroelectric films are not single crystal and single phase, but are poly crystals and contain ferroelectric and dielectric phases. Thus leakage current and dielectric breakdown might be strongly correlated with the natures of grain boundaries and low-k grains in the films. These issues were not focused when the high-k films were applied in an amorphous phase. The application of new properties in crystalline films has brought us a new challenge of engineering the microstructures.
This work was supported by JST CREST Grant Number JPMJCR14F2, Japan.

Figure 1
Effect of SiO2 Coating Layer on CCTO Particles on Properties of CCTO/PVDF Composites
Authors: Talebinezhad Hossein , Tong Yang , Lu Xu , Li Liangxi , Cheng Zhongyang 
Published: February 2020

The ceramic-polymer composites are attracted many researchers attention to using as energy storage. The purpose to get both high breakdown field and high polarization. It is very important to use the high dielectric material as a filler in the polymer matrix to obtain both properties. In many research, ferroelectric fillers like BaTiO3, PbZrO3, BaSrTiO3 have been widely used due to their high dielectric performance [1]. One of the promising materials in this area is CCTO due to showing dielectric constant up to 105 [2-3] The CCTO performance as an energy storage is limited due to low breakdown field and high energy loss. One of the acceptable ways to address this problem is making a composite with a polymer to enhance breakdown field. The ferroelectric polymer like PVDF exhibits high dielectric constant while keep breakdown field high [4-5].
The effect of the SiO2 coating layer and CCTO concentration mixed with PVDF has been studied. The polymer based composites of PVDF/SiO2/CCTO were made by a spin coating process, in which DMF was used as the solvent. The CCTO powders were coated by SiO2 using sol-gel method. The P-E loop test was conducted to measure the energy storage of different composites. The results show an increase in breakdown field while the P-E loop becomes slimmer by making a composite with SiO2. The polarization increased, due to enhancement in the dielectric constant of the composites because of a good connection between matrix and filler made by the additive. The microstructure was studied by using SEM pictures, which shows a better connection between fillers and matrix. The XRD has been used to illustrate the change in the crystallization. The improvement in both polarization and breakdown field make the composite suitable for energy storage usage.
Fig. 1. P-E loop of polymer composites
Refrences:
1- Ke Yu, Hong Wang, Yongcun Zhou, Yuanyuan Bai, and Yujuan Niu, Enhanced dielectric properties of BaTiO3/poly(vinylidene fluoride) nanocomposites for energy storage applications, J. Appl. Phys. 113, 034105 (2013).
2- Laijun Liu, Yanmin Huang, Yunhua Li, Danping Shi, Shaoying Zheng, Shuangshuang Wu, Liang Fang, Changzheng Hu. Dielectric and non-Ohmic properties of CaCu3Ti4O12 ceramics modified with NiO, SnO2, SiO2, and Al2O3 additives. J Mater Sci (2012) 47:2294–2299
3- Qiaoli Zhang, Tao Li, Zhenping Chen, Renzhong Xue, Yongqiang Wang, The non-ohmic and dielectric behavior evolution of CaCu3Ti4O12 after heat treatments in oxygen-rich atmosphere. Materials Science and Engineering B 177 (2012) 168–172
4- Mojtaba Rahimabady, Shuting Chen, Kui Yao, Francis Eng Hock Tay, and Li Lu, High electric breakdown strength and energy density in vinylidene fluorideoligomer/poly(vinylidene fluoride) blend thin films, Appl. Phys. Lett. 99, 142901 (2011)
5- M. Mohammadi, P. Alizadeh, F.J. Clemens, Effect of SiO2 on sintering and dielectric properties of CaCu3Ti4O12 nanofibers, Journal of Alloys and Compounds 688 (2016) 270e279

Figure 1
(Invited) Ab Initio Study of Carrier Transport in Low-Dimensionality Materials
Authors: Fischetti Massimo V , Vandenberghe William G , Gaddemane Gautam , Chen Shanmeng , Ong Zhun-Yong , Chen Edward , Narayanan Sudarshan , Suarez Negreira Ana , Aboud Shela 
Published: February 2020

In the past couple of decades, the theoretical study of two-dimensional (2D) materials that could (hopefully) extend the miniaturization of semiconductor devices beyond the perceived limits of the Si CMOS technology has been affected by two major changes. On the one hand, these new materials are poorly known, so that one must rely almost exclusively on ‘basic’ physics (ab initio or ‘first principles”) to assess their properties. On the other hand, density functional theory (DFT) has reached the mature stage of being predictive, thus compensating for the poor practical and experimental knowledge we have of these materials. Sadly, however, a look at the literature shows that, in many cases, predictions made on carrier-transport properties of 2D materials are wildly inconsistent.
Starting from this consideration, here we will consider various groups of 2D materials: 1. Non-van der Waals (vdW) material, such as phosphorene; 2. ‘Pure’ van der Waals (vdW) planar (sp
2) 2D materials, such as graphene; and 3. Non mirror-symmetric 2D crystals, such as silicene, germanene, and stanene. As an example of the first group, the problem of calculating the low-field carrier mobility in monolayer phosphorene will be reviewed and critically discussed, since values for the mobility reported in the literature span almost three orders of magnitude and clarifications are needed. Therefore, we shall pay attention to the drawbacks and advantages of various ab initio models that can be used to calculate charge-transport properties. Regarding planar vdW materials, we will consider the specific case of graphene (and its nanoribbons) as an example in which the supporting substrate plays the beneficial role of stabilizing the crystal and damping the out-of-plane vibrational modes, but also has the detrimental effect of reducing the carrier mobility via scattering with interface hybrid optical-phonon/plasmon modes. In addition, we shall discuss the strong effect that line-edge roughness has on electron transport in armchair-edge graphene nanoribbons (AGNRs). For non-mirror-symmetric crystals, the strong coupling of electrons with acoustic flexural modes (ZA-phonons) causes major concerns, often ignored. We will discussed this, showing that the problem regarding thermodynamic stability of 2D crystals (the ‘Mermin-Wagner theorem’) can bear strong consequences also on electronic transport.
Pseudopotential-based quantum-transport simulations of 5 nm-long field-effect transistors (FETs) will also be shown, comparing devices based on graphene and phosphorene nanoribbons to Si nanowire-FETs.
Finally, the intriguing properties of 2D topological insulators will be discussed, considering the cases of monolayer tin and bismuth and their potential applications in spintronics and low-power high-performance devices.
(Invited) 3D Dirac Semimetal Cd3As2 Thin Films
Authors: Stemmer Susanne , Schumann Timo , Goyal Manik , Kealhofer David , Shoron Omor 
Published: February 2020

Three-dimension (3D) Dirac semimetals are a newly discovered class of topological materials that have attracted significant interest. Their electronic structure exhibits a linear dispersion relation around the Fermi energy, making them a three-dimensional analogue of graphene. Epitaxial heterostructures of these materials open a path for the manipulation of topological electronic states by strain engineering, electron confinement, or electrostatic gating, all of which may enable new electronic devices.
Here, we discuss the growth of epitaxial thin films of Cd3As2, a 3D Dirac semimetal, by molecular beam epitaxy. We report on their structure, magnetotansport properties, and field gating experiments using high-k dielectrics. The films are shown to grow in the low-temperature, vacancy ordered, tetragonal Dirac semimetal phase. Extremely high room temperature mobilities (~20,000 cm2/Vs) are achieved in epitaxial layers on III-V substrates. Unusual transport characteristics are observed, such as a negative longitudinal magnetoresistance, i.e., when the magnetic field is applied parallel to the direction of electric current. We vary the film parameters and study their influence on the magnetotransport to distinguish between ‘classical’ phenomena and effects originating from the unique electronic structure.
(Invited) Room Temperature Aging Effect Improvement for Device Stability and Manufacturability of FinFET Technologies
Authors: He Xiaoli , Triyoso Dina , Uppal Suresh , Fu Bianzhu , Zhang Xing , Yamaguchi Shimpei , Yong Chloe , Liu Bingwu , Joshi Manoj , Samavedam Srikanth 
Published: February 2020

In CMOS manufacturing industry, device threshold voltage (Vt) stability is a pre-requisite for volume manufacturing. Device architectural elements, process parameters and room temperature aging (Q-time) are the main source of Vt instability. In FinFET technology with metal/high-K gate, device Vt is controlled through effective work function engineering by optimal metal layer thickness as well as controlled Aluminum (Al) doping/diffusion within the gate stack [1-4]. The device Vtcan also be influenced by its architectural elements and process parameters [5] which should be well controlled during the volume manufacturing. However, room-temperature Q-time effects at several stages of the manufacturing process are practically unavoidable.
This work demonstrates post n-work function (WF) deposition Q-time impact on device Vt instability. Longer Q-time induced Vt shifts that are independent of gate length and number of fins, as seen in Figure 1. The root cause investigations were performed using device characterization followed by elemental analysis of the gate stack (Figure 2). It was found that, the content of oxygen (O2) and Al in the gate stack is well correlated to post n-WF deposition Q-time. The device Vt instability can be explained by oxygen incorporation due to n-WF layer oxidation during the Q-time post n-WF deposition and the corresponding reduction of Al diffusion into the high-K capping layer [2, 6]. In this work, n-WF layer thickness/composition was optimized to enable immunity to a larger Q-time limit for volume manufacturing, as demonstrated in Figure 3 from n-WF layer recipe group A to group C. The reliability impact of the gate stack was also assessed. Device benefits such as Tinv scaling and thereby Ion-Ioffperformance improvement was also demonstrated without compromising the reliability.

Reference

[1] L.P.B. Lima et al, J. Appl. Phys., 115, 074504, 2014
[2] A. Veloso et al, Jpn. J. Appl. Phys.52. 04CA02, 2013
[3] L. Kornblum et al, Appl. Phys. Lett., 100, 062907, 2012
[4] C.L. Hinkle et al, Appl. Phys. Lett.,96, 103502, 2010
[5] M. Togo et al, VLSI tech.
Symp. Dig.pp. 140-141, 2014
[6] A. Veloso et al, VLSI Tech.
Symp. Dig. pp. 34-35, 2011.

Figure 1
(Invited) Electrochemical Deposition of Ag- or Au-Based Alloy Films
Authors: Zangari Giovanni 
Published: February 2020

Precious metal-based alloy coatings are of interest for both decorative and technological applications, the latter including electrocatalysis, electrical contacts, and plasmonic devices among others [1,2]. The ternary system Au-Ag-Cu in particular provides a playground to finely tune optical and other functional properties. Synthesis of these alloys by electrodeposition further enhances the ability to tune these properties, since metastable phase configurations can be realized by varying the deposition kinetics.
Au-Cu alloys have been deposited by simple and complexing electrolytes; alloy composition could be predicted based on the alloy enthalpy of mixing and the microstructure could be controlled through electrolyte chemistry. In particular, the relative nobility of the two components could be switched via selective complexation, resulting in distinct atomic configurations.
Ag-Cu alloys were also electrodeposited from a simple and a thiourea complexing electrolyte. Deposition from the non-complexing solution shows a lack of luster; the two metals are reduced independently, resulting in phase separation, with limited or no mutual solubility. The thiourea electrolyte on the other hand is capable to form shiny films. The crystal structure in this case shows a gradual variation of lattice constant, suggesting the formation of a continuous series of solid solutions. Electron microscopy however was unable to distinguish between a solid solution or eutectic formation. Metal complexation and tuning of the deposition rate in this case results in a kinetically induced metastable structure.
Finally, Au or Ag alloys with Ni exhibit in the bulk a miscibility gap; electrodeposited films in contrast form apparent solid solutions that are generated by various kinetic phenomena, including kinetic trapping, spinodal decomposition and growth instabilities [3].

References

[1] A.D. Nilekar, et al. "Bimetallic and ternary alloys for improved oxygen reduction catalysis." Topics in Catalysis 46.3-4 (2007): 276-284.
[2] M.G. Blaber, M.D. Arnold, and M.J. Ford. "A review of the optical properties of alloys and intermetallics for plasmonics." Journal of Physics: Condensed Matter 22.14 (2010): 143201.
[3] D. Liang, et al. "Nanoscale Structuring in Au–Ni Films Grown by Electrochemical Underpotential Co‐deposition." ChemElectroChem 1.4 (2014): 787-792.
Electrodeposition of Cobalt-Ruthenium Alloys from Acidic Bath
Authors: Kutyla Dawid , Kolczyk Karolina , Kowalik Remigiusz , Zabinski Piotr 
Published: February 2020

The article presents results of tests on potentiostatic electrodeposition of ruthenium and Co-Ru alloys. The tests applying the method of cyclic voltammetry with the use of gold disk electrode (RDE) allowed to define a potentials range in which it is possible to obtain ruthenium and its alloys with cobalt from acid chloride electrolytes.
The influence of electrodeposition parameters and the electrolyte composition on the composition, morphology and structure of the obtained deposits was determined. Co-Ru alloys underwent XRD tests, an analysis with the XRF method and observations using scanning electron microscopy (SEM). Hydrogen evolution tests have been also performed.
Acknowledgment
The authors would like to thank Polish National Science Centre for the financial support provided by the grants: No UMO-2013/09/B/ST8/00211.
(Invited) Stress in Electrodeposited Ni and Cu: Understanding the Effects of Deposition Conditions and Microstructure
Authors: Chason Eric , Rao Zhaoxia , Engwall Alison 
Published: February 2020

Residual stresses are a persistent problem in electrodeposited thin films. Stress can lead to cracking or delamination and limit the performance of protective coatings that are grown by electrodeposition. The deposition conditions can greatly modify the stress, so it would be useful to understand how they effect the stress in order to better predict and control it. Therefore, we have performed systematic experiments to measure the dependence of stress on the growth rate and electrolyte composition in electrodeposited Ni and Cu films. Because the microstructure of the film can change with thickness, we have also characterized the grain size evolution for correlation with the stress. This leads to some surprising behavior. For films that grow with tensile stress (high growth rate), the stress becomes less tensile for larger grain size. For films that grow with compressive stress (low growth rate), the stress becomes less compressive/more tensile for larger grain size. These results are interpreted in terms of a kinetic model that focuses on stress-generating processes occurring at the boundary between adjacent grains as the film grows.
A Novel Electrochemical Method for Analysis of Thin Metal Films and Bilayers for Application in the PCB Industry
Authors: Palin Emma J.R. , Ryder Karl Scott , Hillman A Robert , Smith Emma L. , Ferreira Virginia , Sapstead Rachel , Steinke Nina-Juliane , Barker Robert , Dalgliesh Robert 
Published: February 2020

The fabrication and assembly of printed circuit boards (PCBs) involves the layering of metals onto an insulating substrate prior to the addition of electronic components. The interfaces between these metal layers are often subject to metal-metal interdiffusion, formation of brittle intermetallics and corrosion, compromising the integrity of the PCB-component solder joints. We have recently developed environmentally sustainable, non-toxic methodologies for application of metal PCB finishes using Deep Eutectic Solvents (DESs) as a novel solvent medium.1-3

Here we focus on the characterisation of metal-metal interfaces in DES media quantifying interfacial structure, layer thickness and morphology using a range of electrochemical and microscopy techniques, including chronoamperometry, cyclic voltammetry (CV) and novel simultaneous thickness electrochemical potential (STEP) measurements coupled with neutron reflectivity (NR.) We have developed the STEP methodology to ascertain some, if not all, of the same information that NR provides.
Deposition of Ag and Cu layers has been carried out in different configurations onto Au substrates and characteristic STEP traces are presented for each upon galvanostatic stripping. The STEP methodology facilitates the identification and quantification of each metal layer by galvanostatic dissolution, which is comparable with time resolved NR measurements. The characteristic features of the STEP measurements are discussed including the shape and potential of the dissolution trace. The degree of mixing between the layers is qualitatively determined from E vs. t traces, along with the layer composition and thickness for systems in which layers remain discrete.
In summary, we present a new, accessible and inexpensive technique, which probes the thickness, composition and interfacial mixing between layers in PCB metal systems using DES electrolytes and galvanostatic stripping methodologies.
[1] A. D. Ballantyne, G. Forrest, M. Goosey, A. Griguceviciene, J. Juodkazyte, R. Kellner, A. Kosenko, R. Ramanauskas, K. S. Ryder, A. Selskis, R. Tarozaite and E. Veninga, Circuit World, 2012, 38(1), 21-29.
[2] K. S. Ryder, A. D. Ballantyne, D. Price and T. Perrett, The PCB Magazine, February 2012, 22-30.
[3] A. P. Abbott, S. Nandhra, S. Postlethwaite, E. L. Smith, and K. S. Ryder, Phys. Chem. Chem. Phys., 2007, 9, 3735–3743.

Figure 1
Tailored Shapes of Fe-Ni-Co Nanowires
Authors: Podlaha Elizabeth , Li Deyang , Geng Xiaohua 
Published: February 2020

Template-assisted, electrodeposited Fe-Ni-Co nanowires are reported targeting an Invar-like composition (e.g. Fe-rich, with < = 5 wt % Co) of interest for the materials low thermal expansion property and its ability to be magnetically aligned. The morphology of the nanowires is controlled by pulse and DC deposition conditions, and the electrolyte pH. Not only are nanotubes and solid wires fabricated, but also novel porous structures. The porous nanowires utilize the gas evolving side reaction as a dynamic template. Post treatment of nanowires via chemical etching, can also be used to shape the nanostructures. Two different approaches are examined, 1) creating dissimilar crystalline structure within the nanowire by the choice of the deposition operating conditions followed by a select etch in structure, and 2) introducing a sacrificial element, such as Cu, to selectively etch it in a passivating Fe-Ni-Co environment. Unique thinned nanowires and nanotips were designed.
The authors acknowledge the NIH and Roche Diagnostics for support of this project.
(Invited) Electrodeposition in Tailored Nanochannels: A Rich Plattform to Study Nanowire Growth in Confinement and to Develop Stable Functional 3D Nanowire Architectures
Authors: Toimil-Molares Maria Eugenia 
Published: February 2020

The implementation of nanowires and nanotubes for applications such as thermoelectrics, catalysis, plasmonics, or photoelectrochemical water splitting for hydrogen generation requires both, an excellent control on geometry, crystallinity and composition of the individual nanostructures, as well as its successful assembly into 2-D and 3-D architectures. Fabrication of 3-D nanowire superstructures by vapour–liquid–solid processes has been reported; however, it reveals a limited tunability of the relevant parameters.
This talk will illustrate how the unique combination of electrodeposition and tailored nanochannel templates provides an excellent platform (i) to study and control the nanowire growth, and (ii) to synthesize 3-D nanostructure assemblies and investigate their size-dependent properties.
Membranes with parallel nanochannels are fabricated by swift heavy ion irradiation and subsequent chemical etching. In addition, templates with interconnected tilted nanochannels are obtained by applying ion irradiation at several incident angles in consecutive steps. Nanochannel density and orientation, as well as diameter and geometry, are adjusted by the irradiation and etching conditions, respectively. Subsequent electrodeposition in the channels results in nanowire arrays and highly ordered 3-D nanowire ensembles of various materials. Recent developments achieved on the electrodeposition of metal (Au1-xAgx), semiconductor (ZnO and p-Cu2O) and semimetal (Sb) nanowire arrays and nanowire networks will be presented. Special emphasis will be given to the implementation of the nanowire assemblies in photoelectrochemical and thermoelectric devices, which is possible thanks to the flexibility and control offered by electrodeposition.