bluuebunny/crossref_metadata_2025_split huggingface dataset:
Broadband Spectroscopic Characterization of Hybrid Low-k Dielectric Thin Films for Micro- and Nanoelectronic Applications
Authors: Obeng Yaw S. , Okoro Chukwudi A. , Montgomery Karl R. , Amoah Papa K. , You Lin , Kopanski Joseph J. , Obrzut Jan 
Published: February 2020

Broadband Spectroscopic Characterization Of Organic and Hybrid Dielectrics Thin Films for Micro- and Nanoelectronic Applications

Yaw S. Obeng*, Chukwudi A., Okoro, Karl R. Montgomery, Papa K. Amoah, Lin You, Joseph Kopanski, Jan Obrzut
Engineering Physics Division, Physical Measurement Laboratory, National Institute of Standards and Technology, 100 Bureau Drive, Gaithersburg, MD 20899
Micro- and nanoelectronic devices use materials of varying dielectric constants for specific applications1, 2, as in electrical insulation and isolation; however the matching of materials to applications has is frequently guided by intuition3. The electrical performance of the materials, e.g., dielectric constant, is frequently evaluated by measuring the metric such as impedance measurements on metal-insulator-metal (MIM) capacitors, and by assuming that the MIM devices are ideal4. However, as we have shown elsewhere, these devices are imperfect, and the chemistry and physics of the materials also play crucial roles in their application utility, especially in low operating voltage devices5, 6. Thus, material selection based on such characterization frequently result in sub-optimal choices.
In this paper, we discuss the use of broadband microwaves (MW) (up to 20 GHz) characterize organic and hybrid silicon-organic thin films meant for insulation applications in micro- and nanoelectronic devices. Specifically, we will take advantage of MW propagation characteristics7, to extract and examine the relationships between electrical and mechanical properties, and the chemistry of prototypical materials. The impact of moisture on the electrical behavior of any material defects will be evaluated from the impact of thermal anneal at modest temperatures on the samples. These studies will shed light on the chemical changes that occur within the dielectric films that could impact the performance and reliability, as well as provide basis for rational selection of organic dielectrics for integrated device.
1. R. P. Ortiz, A. Facchetti and T. J. Marks, Chemical Reviews 110(1), 205-239 (2010).
2. W. Volksen, R. D. Miller and G. Dubois, Chemical Reviews 110(1), 56-110 (2010).
3. V. Sharma, C. Wang, R. G. Lorenzini, R. Ma, Q. Zhu, D. W. Sinkovits, G. Pilania, A. R. Oganov, S. Kumar, G. A. Sotzing, S. A. Boggs and R. Ramprasad, Nat Commun 5(2014).
4. E. Verrelli, N. Kemp, M. O'Neill, F. Cheng, F. A. Alharti and S. M. Kelly, SID Symposium Digest of Technical Papers 44, 108-111 (2013).
5. Y. S. Obeng, C. A. Okoro, P. K. Amoah, R. R. Franklin and P. Kabos, ECS Journal of Solid State Science and Technology 5(4), P3025-P3030 (2016).
6. C. A. Okoro and Y. S. Obeng, Thin Solid Films 520(15), 5060-5063 (2012).
7. J. Obrzut, ACTA IMEKO 4 (3), 42-46 (2015).
ALD for Functional Devices Based on TiO2 Nanotube Arrays
Authors: Zazpe Raul , Prikryl Jan , Sopha Hanna , Macak Jan M. 
Published: February 2020

Synthesis of highly-ordered nanostructures of valve metal oxides has recently attracted huge scientific and technological interest motivated by their possible use in many applications.
It is the nanotubular TiO2 that has received the highest attention after porous Al2O3, motivated by its wide range of applications, including photo-catalysis, solar cells and biomedical uses. However, the TiO2 nanotube potential for a range of advanced devices, in particular when considering all possible shapes and geometries, has not at all been exploited. One of the major issues to extend the functional range of nanotubes is to coat homogenously tube interiors by a secondary material, potentially until the complete tube filling. Efforts based on electrochemical deposition, chemical deposition and spin-coating led only to limited success with a narrow range of materials.
The presentation will therefore focus in detail on the coating of secondary materials inside the nanotubes by means of ALD. The deposited materials influence strongly optical, electrical and mechanical properties of nanotubes. Experimental details and some very recent results demonstrating unprecedented ability of nanotube functionalization by ALD will be presented and discussed [1-3].

References:

1] J.M. Macak, Chapter 3: Self-organized anodic TiO2 nanotubes: functionalities and applications due to a secondary material in monograph Electrochemically Engineered Nanoporous Materials: Methods, Properties and Applications. Editors: A.Santos, D. Losic. Springer, 2015. ISBN: 978-3-319-20345-4, Vol. 220.

2] J. M. Macak, J. Prikryl, H. Sopha, and L. Strizik, Phys. Status Solidi RRL, 9, 516 (2015).
3] R. Zazpe, J.M. Macak et al. Adv. Mater. Interf., under review

Figure 1
Improved Activity and Stability of TiO2-Coated Co/C Catalysts for Electrochemical Application
Authors: Kim Hyung Ju , Jackson David H. K. , Kuech Thomas F. , Huber George W. 
Published: February 2020

In this work we demonstrate the preparation, characterization and testing of a highly active and stable TiO2 coated Co/C catalyst for the electrochemical water oxidation. This non-precious metal catalyst is over 3 times more active than the traditionally used Pt based catalyst. The TiO2 coating was added by atomic layer deposition (ALD). The TiO2 overcoat increased the stability of the cobalt particles and the catalytic activity of the cobalt metal. The improved activity for water oxidation of these catalysts is probably associated with the role of ALD(TiO2) in promoting the oxidation of surface Co oxide. The formation of Co-O-Ti configuration on the ALD(TiO2)-Co/C catalysts may also change the surface binding energy of O or OH species on the catalyst surface. Therefore, the ALD(TiO2) overcoating on Co/C could change the nature of the active sites, thereby facilitating the formation of O-OH (known as the rate-limiting step for the reaction) more effectively, which could improve the water oxidation activity. In addition, the stability of the ALD(TiO2)-Co/C catalyst was enhanced compared to the Co/C catalyst. This work shows how the ALD synthesis technique can be used to improve the catalytic activity and stability of non-precious metal based catalysts like Co/C for electrochemical water oxidation.
High Aspect Ratio through Silicon Via Filling By Nickel-Tungsten Alloy Using Graphene As a Conducting and Barrier Layer
Authors: Huang Yen-Cheng , Zeng Wei-Yang , Chang Shih-Cheng , Dow Wei-Ping 
Published: February 2020

Recently, three-dimensional (3D) chip stacking becomes more and more important because of “More than Moore” story. Through silicon via (TSV) technology is one approach to achieve the target of “more than Moore”. However, the coefficient of thermal expansion (CTE) of copper filled in the TSV may lead to failure of the TSV interconnects because the copper CTE is much higher than that of silicon. The packaging materials with different CTEs will induce large stress at interfaces of materials. To overcome this problem, we choose nickel to substitute copper as a filling material of TSV since the nickel CTE is lower than copper CTE. To further decrease the CTE of the filling material, a few tungsten whose CTE is similar to that of silicon is codeposited during filling plating.
Graphene has drawn extensive attention due to its outstanding electrical and thermal properties. In addition, graphene can be used as a barrier layer of copper diffusion. Also, the CTE of graphene is similar to that of silicon. Hence, we use graphene to replace the TiN barrier layer and the copper seed layer, which was used in the traditional TSV process.
The filling performance is evaluated by examining vertical cross-sections and top-down cross-section of the filled TSVs by using optical microscope (OM). The Ni-W pillar is examined by scanning electron microscopy (SEM). The thermal reliability of the fully filled TSV is evaluated after a thermal annealing process. The CTE of the filled Ni-W is measured by thermomechanical analysis.
Using Reduced Graphene Oxide (rGO) As a Conducting Layer on a Polyimide Flim for Cu Metallization
Authors: Zhang Yu- Zhen , Dow Wei-Ping 
Published: February 2020

Polyimide (PI) film is an insulator and has been commonly used as a dielectric layer of a flexible printed circuit board (FPCB) due to its high thermal stability, well mechanical strength and excellent chemical resistance. For FPCB fabrication, the dielectric layer surface, PI surface, has to be metallized. Herein, we proposed an all-wet process to fabricate a copper diffusion barrier layer, avoiding Cu diffusion into the PI and a conducting layer, that is, a reduced graphene oxide (rGO) grafted on the PI surface. For a copper diffusion barrier layer, rGO has great electrical and thermal properties, and easy process than Ni barrier deposited by electroless plating. Owing to graphene oxide has a lot of carboxyl functional groups that forms carboxylate anions, it can ligand with the cations on the PI surface after the PI went through a chemical grafting process step. In this work, we successfully utilized rGO as a conducting layer on the PI surface, which can conduct copper plating on the PI surface. Furthermore, we demonstrated that rGO changed PI surface roughness by using an atomic force microscope (AFM).

Keywords

Reduced Graphene Oxide, Polyimide, Copper Electroplating

References

[1] Wei-Ping Dow, Guo-Liang Liao, Shang-En Huang and Sinn-Wen Chen, “Modification of Cu nanoparticles with a disulfide for polyimide metallization”, J. Mater. Chem.
(2010) 20, 3600-3609
[2] T. Osaka, S. Wakatsuki, T. Masuda, M. Yoshino, N. Yamachika, J. Sasano, I. Matsuda, Y. Okinaka, “A Wet Process for Forming an Adhesive Copper Layer on Polyimide Film”, Electrochemistry, 76, 191 (2008).
[3] Songfeng Pei, Hui-Ming Cheng, “The Reduction of Graphene oxide”, Carbon, 2012, 50, 3210-3228
Using Reduced Graphene Oxide As Conducting Layer of Plating through Holes of a Printed Circuit Board
Authors: Chang Shuo-Wen , Zeng Wei-Yang , Dow Wei-Ping 
Published: February 2020

Graphene is a popular material because of its unique two-dimensional (2D) structure and intrigued physical and chemical properties. Graphene materials, including single layer and multi-layer graphene sheets, have recently drawn extensive attention due to their outstanding electrical and thermal properties. In the traditional metallization process of through holes of printed circuit boards (PCBs), copper electroless deposition process has been commonly used. It has environmentally unfriendly characteristics because it contains precious metal (i.e., Pd), formaldehyde and chelating agents. In contrast, reduced graphene oxide (rGO) has no these issues and can replace the copper electroless deposition of PCBs because the rGO process for copper metallization is simpler than that of copper electroless deposition. Herein, we used rGO process to replace the copper electroless deposition process in order to achieve a green fabrication process.
In this study, the effect of different conditioners for uniform adsorption of graphene oxide (GO) on the sidewalls of through holes of a PCB was investigated. We used different conditioners to chemically modify the substrate surfacefor uniform adsorption of GO. Following the GO adsorption, the adsorbed GO was reduced to rGO on the substrate surface. Then, the rGO-coated sidewall becomes conductive to replace the copper seed layer by electroless deposition. Finally, the rGO-coated through holes were successfully plated in an acidic copper bath with a high throwing power and these through holes could pass thermal shock reliability test.
A Copper Plating Formula Development for through-Hole Filling without a Dimple on Top of the Hole Opening
Authors: Geng Hong-Jyun , Wen Shih-I , Dow Wei-Ping 
Published: February 2020

In recent years, the butterfly technique (BFT1) was developed to achieve through-hole (TH) filling of a printed circuit board (PCB) by copper electroplating.1It not only can operate in direct current plating but also perform a void-free TH filling. However, a thick copper layer is plated on the surface of a PCB to cause a dimple issue on the TH opening. The dimple on the TH opening has to be leveled off, otherwise the following build-up process cannot be performed because there are a lot of dimples on the inner copper layer. In this work, we adjusted the plating formula to overcome the dimple issue of BFT for TH filling. The plating result shows that a thin copper layer plated on the PCB surface is obtained and the dimple is significantly improved. The enhancement in the TH copper filling performance is beneficial to the build-up process of advanced PCB. Keywords: Through-hole filling, Printed circuit board, Dimple, Copper Electroplating

Reference

W. P. Dow, H. H. Chen, M. Y. Yen, W. H. Chen, K. H. Hsu, P. Y. Chuang, H. Ishizuka, N. Sakagawa, R. Kimizuka, “Through-Hole Filling by Copper Electroplating”, Journal of The Electrochemical Society, 2008, 155, D750-D757.

Figure 1
3D Printed Porous Dielectric Layers for Low Dielectric Applications
Authors: Oh Ji Young , Lee Kyu-Sung , Kim Kyung-Hyun , Yang Yong Suk , Lee Chang-Woo 
Published: February 2020

3D printing is an additive manufacturing (AM) technique that constructs successive layers of materials to create three-dimensional architectures. Due to the possibility to build rapid prototypes in almost any geometry and internal structure, 3D printing has drawn much attention for development of advanced materials and equipment for a wide range of applications including biotechnology, microfluidics, aerospace, energy, and electronics.
Among the recently developed 3D printing applications, electronics fabricated by 3D printing are becoming increasingly attractive due to simple manufacturing process and more complicated 3D structures compared with electronics fabricated by traditional mechanical manufacturing process such as drilling and milling. In 3D printing electronics, material properties are directly related to performance of 3D designed electronics. Thus, it is important to develop good printable materials for 3D printing electronics such as high conductive material and low dielectric constant material. Especially, for the dielectrics, the low dielectric constant material can solve the electric drawbacks such as interconnection or signal delay for high performance devices. Introducing-porous structures into a polymer matrix is attractive approach to decreasing the dielectric constant by providing an architecture containing embedded air pockets (with a dielectric constant of 1).
In this work, we employed azodicarbonamide as a forming agent in 3D printable dielectric material to control the porosity of the dielectric film. The printed dielectric film was heated to 210 oC. As a result, a microporous structure was developed in the film and the morphologies was studied by SEM images. The details of the porous structures of our films, together with the dielectric properties of the 3D printed layer evaluated, will be presented at the session.
Acknowledgements: This work was supported by the National Research Council of Science & Technology (NST) grant by the Korea government (MSIP) (No. CRC-15-03-KIMM).
(Keynote) Solid Electrolytes and Metallic Lithium Anodes
Authors: Goodenough John B. 
Published: February 2020

The development of oxide cathodes enabled the Li-ion rechargeable battery of the wireless revolution, but the extension to large-battery applications has been hampered by safety concerns and the assumption that it is not possible to plate an alkali-metal anode on charge without dendrite formation. The development of a glass from which metallic lithium or sodium can be plated without dendrites and that has a Li+ or Na+ conductivity greater than 10-2 S/cm at room temperature with an activation energy less than 0.1 eV for cation mobility offers a safe, long-cycle-life promise for large rechargeable alkali-metal batteries.
Controlled Deposition of Li Metal
Authors: Li Yejing , Wang Xuefeng , Wang Zhaoxiang , Chen Liquan 
Published: February 2020

The increasing demand for higher density of energy storage requires breakthroughs in secondary battery techniques and systems. Metallic lithium (Li0) is attractive because it can be a common anode material for the lithium-sulfur (Li-S), lithium-oxygen (Li-O2 or Li-air) and all-solid lithium batteries due to its low electrode potential (-3.04 V vs. SHE) and high specific capacity (3860 mA h g-1) among the known anode materials. However, it is not viable in commercial secondary batteries at present because of its high activity towards the liquid electrolytes, and safety issues associated with the growth and fracture of Li dendrites during cycling. These issues have been obsessing the scientists and hindering the commercialization of secondary lithium batteries for decades.
Herein, controlled deposition of Li metal was realized on specially designed micro-/nano-architectured Si wafer and ZnO nanowires array, on the basis of preferential deposition of Li in the grooves of micro-patterned Ti foil, all showing the confining or guiding effect of the porous structure on Li metal deposition. The preferential deposition (and sometimes the growth) of lithium in the defected grooves of inactive Ti foil, in the micro-wells of active Si, and in the nanopores formed by bunches of active ZnO nanowires, indicate that the Li-storage activity of the material becomes less important in some particular cases but their appropriately designed micro- or nano-architectures become the dominating factor, to determine where the lithium will be deposited. These findings enrich our understanding on the intercalation and deposition properties of lithium and provide important revelations on effectively controlling the intercalation, deposition and growth of lithium, and suppressing the growth of lithium dendrites. The hetero-epitaxial growth of lithium on ZnO nanowires further demonstrates that the crystallographic structure of the electrode material can even affect the growth direction of the lithium nanowires.
We expect that the concept of designing micro-/nano-architectured electrodes be a promising strategy to tackle some of the obsessing issues of the Li metal anode and promote the commercialization of the secondary lithium batteries.
Acknowledgements
This work was financially supported by the National 973 Program of China (No. 2015CB251100).

Figure 1
Core-Shell Structure in Li-Battery Application: Phase Control and Electrochemical Property
Authors: Hu Linhua , Freeland John W , Cabana Jordi 
Published: February 2020

Architectures based on core-shell structures have been employed in different approaches for materials design in order to tune physical characteristics and chemical function. In the case of batteries, using active cathode materials as core and non-active metal oxide shells is a prevailing strategy to decrease chemical degradation at electrode/electrolyte interfaces. The main challenge becomes to balance the need for high Li ion diffusion while enable electronic insulation to avoid secondary redox processes that degrade the electrolyte or induce the loss of the active transition metals into solution. Traditional synthetic methods based on high temperature treatments induce compositional inhomogeneity in core-shell structures due to excessive diffusion, resulting in difficulties to form uniform, yet ultrathin shells. Further, any synthetic strategy must enable the tuning of the chemical species in the surface inactive oxide shell is important to influence the protective function of the inner active oxide core.
Herein, we report a new strategy to synthesize well-defined LiCoO2 nanocrystals with ultrathin shells based on Al. Through variations in Al loading and post-synthetic treatment, the specific phase and durability were tailored. The progression between amorphous Al2O3 and LiAlxCo1-xO2 with temperature was evaluated by XRD and EDX line-scan analysis. Soft X-ray was used to probe the changes in chemical bonding both at the surface and bulk of the material. The electrochemical properties were found to vary depending on these compositional parameters. Compared to bare LiCoO2 nanocrystals, amorphous Al2O3 led to higher capacity and average stability, with LiAlxCo1-xO2 providing much higher stability but lower capacity. A tailored compromise between these two end situations will be discussed.
Enhancing Surface Diffusion in Battery Electrodes Using Solvent Adsorbates
Authors: Li Yiyang , Chen Hungru , Guan Zixuan , Attia Peter , Lim Jongwoo , Bazant Martin Z. , Islam M. Saiful , Chueh William C 
Published: February 2020

LiFePO4 is one of the most well-studied positive electrode materials. A well-established doctrine is that Li only diffuses within one-dimensional channels, with negligible diffusivities in the other directions, and almost no movement of Li between channels. However, existing experimental measurements and density functional theory calculations have generally been conducted for bulk LiFePO4, and have largely neglected surface diffusion at the solid/liquid interface. In our work, we directly study the ambipolar Li diffusion along these nominally slow directions perpendicular to the fast conduction channels.
Because ambipolar transport of Li is controlled by the slow species, it is difficult to quantify using standard electrical measurements, which generally probe the fast species. To overcome this challenge, we measure the time for a solid solution Li0.5FePO4 electrode to separate into Li-rich and Li-poor phases. Because phase separation necessitates the movement of Li within a particle between the fast conduction channels, this technique directly provides the ambipolar transport of Li. Our results show that phase separation is extremely slow under dry, inert conditions. However, when placed in an organic solvent containing ethylene carbonate but no electrolyte salt, the rate of phase separation is enhanced by more than two order of magnitude. Because the ethylene carbonate only interacts with the surface of the LiFePO4 particles, the enhancement in Li transport demonstrate that surface diffusion is many orders of magnitude faster than bulk diffusion. Additionally, the rate of surface diffusion can be tuned by environmental adsorbates. We confirm our findings through density functional theory calculations, which show a significant reduction in migration enthalpy in the presence of a solvent adsorbate.
Our results show that surfaces diffusion enhances the conductivity of Li along the nominally slow directions by several orders of magnitude, and thus reduces the anisotropy of Li diffusion in LiFePO4. Additionally, by demonstrating that the conductivity can be tuned using environmental adsorbates, we offer a novel approach towards enhancing the conductivity of electrode materials. By choosing the correct adsorbates to activate surface diffusion, nominally insulating materials can be conductive at the solid/liquid interface. This introduces a new paradigm in interfacial engineering of electrodes, and could significantly expand the class of insulating materials which are suitable as electrodes in Li-ion batteries.