bluuebunny/crossref_metadata_2025 huggingface dataset:
Integrated CMOS-MEMS Technology and Its Applications
Authors: Machida Katsuyuki , Konishi Toshifumi , Yamane Daisuke , Toshiyoshi Hiroshi , Masu Kazuya
Published: February 2020

Fusion of microelectromechanical systems (MEMS) with CMOS LSI technologies is a promising way to develop high functional devices. We have been developing the integrated CMOS-MEMS technology that fabricates MEMS devices on CMOS LSI[1-2]. Thetechnology has the features ofhigh-functionality, high-accuracy, and mass-production.

In this paper, first, MEMS technology trends and the concept of the integrated CMOS-MEMS technology are described. Next, we present the multi-physics simulation for the CMOS-MEMS technology[3-4]. Finally, as the examples, we demonstrate the arrayed CMOS-MEMS accelerometer[5-7].

Prospects and challenges of the integrated CMOS-MEMS technology are described from the view point of CMOS-LSI (Fig.1). It indicates that this technology gives the solution of developing high functional devices.

We have developed the multi-physics simulation platform to analyze the electromechanical behaviors of MEMS and CMOS simultaneously. Based on the analytical model, the equivalent circuit was proposed to simulate the above behavior on a Verilog-A compatible hardware description language (Fig.2).

Small size and wide range accelerometers are increasingly in demand in the various system. Figure 3 shows the proposed arrayed CMOS-MEMS accelerometer that was capable of detecting a wide range of acceleration. The MEMS accelerometer was fabricated by gold electroplating with post-CMOS process. We can obtain the 3-by-3 arrayed MEMS accelerometer with the sensing range from 1.7G to 20G(Fig. 4). Also, using the simulation results obtained by the above multi-physics platform, we can realize the CMOS-MEMS accelerometer.

In conclusion, it is confirmed that the integrated CMOS-MEMS technology will pave the way for the More than Moore technology.

References

[1] K. Machida, et al., IEEE Trans. Electron Devices
48, 2273 (2001).

[2]K. Machida, et al., SSDM2010, Tokyo, Sep. 24, p.818(2010).

[3]H. Toshiyoshi, et al., IEDM 2012, USA, p. 6.3.1(2012).

[4]T. Konishi,
et al., IEEE/ASME
J. Microelectromech. Syst., vol. 22, no. 3, Jun. p.755 (2013).

[5]D. Yamane, et al., Transducers 2013, Spain, p.22 (2013).

[6]T. Konishi, et al., Jpn. J. Appl. Phys., vol. 52, p. 06GL04(2013). [7]T. Konishi, et al., SSDM 2013, Sept. 24-27, Fukuoka, Japan. p.844(2013).
(Invited) Metrology for 3D Integration
Authors: Allen Richard A , Vartanian Victor , Read David , Baylies Winthrop
Published: February 2020

Three-dimensional stacked integrated circuits (3DS-IC) fabrication requires complex technologies such as high-aspect ratio through-silicon vias (TSVs), wafer thinning, thin wafer handling and processing, and bonding of thin wafers with complex patterned surfaces. The implementation 3DS-IC also presents significant metrology challenges. This talk will give an overview of the metrology needs for 3DS-IC, identify solutions, and describe work towards the development of standards to support the 3D ecosystem.

One of these standards under development is investigating methods for identifying and characterizing voids between bonded wafers. Wafer bonding in a 3DS-IC process is typically an intermediate step. After bonding, one or both of the wafers will undergo processes such as thinning, thin film deposition, lithography, and patterning. The presence of voids between the wafers will cause significant stack thickness variation, which can lead to failure at one or more of these steps. A number of tools can be used to identify and/or characterize voids; this standard will provide members of the 3DS-IC community with guidance for choosing the tool or tools that will best address the specific need.

Preliminary results from a round robin experiment, involving approximately 20 laboratories, will be shown. This experiment uses as a test structure a bonded wafer pair with a number of voids patterned into one of the wafers before bonding. The sizes of the programmed voids range from 0.5 μm to 300 μm with depths of 15 nm to 1200 nm and are placed in isolated, semi-dense, and dense patterns. A scanning acoustic microscope image of one instance of the test chip with patterned voids is shown in the figure.
(Invited) Framework for Structural, Processing, and Environmental Assessment of Micro to Nano Scaled Integrated Circuit Structures
Authors: Thomas Sylvia , Bell Brian , Alcantar Norma , Durham Delcie , Perez Samuel
Published: February 2020

Micro to nano-scaled structures are progressively being integrated into semiconductor architecture and will have a global impact on filtration, biosensing, and energy storage. These structures include micro and nano sized fiber membranes for electrodes, nanolaminates for trenched capacitors, or nanofiber membranes for sensing and actuating. For integrated circuit innovations, the ultimate thrust is to provide superior functionality and structural durability without adversely impacting the environment. As micro to nano-scaled structures rapidly progress toward scalable manufacturing, it is critical and timely to conduct fundamental investigations on assessing material composition impacts on functional failures and environmental sustainability. This research uses a failure and life cycle assessment (FLCA) process to understand material composition influence on micro and nano structure 1) properties, 2) performance limiting defects (failure), and 3) environmental impacts The FLCA integrates multiple characterization stages, performance testing, and environmental assessments of fiber membranes. This work will have a long-term impact on the integration of nanoscaled structures into emerging electronic materials per the International Technology Roadmap for Semiconductors (ITRS) and identifying a transferable process for a FLCA to evaluate polymer nanofiber technology for ICs.
Study of HKMG Stack Interface Engineer Applicable to 22nm/16nm Finfet Mosfet
Authors: Xiong WenJuan , Wang DaiHai , Yin Huaxiang , Zhang Yongkui , Cui Hushan , Luo Ying , Li Tingting , Jiang Haojie , Zhu Huilong , Li Junfeng , Yan Jiang , Zhao Chao
Published: February 2020

Since Intel announced that they had made a great breakthrough in 22nm node[1][2]on May 4, 2011, FinFET Transistor structures had almost controlled CMOS technology beyond 22nm node. In this node, with the development of lithography, silicide process was switched to the back end. This huge change bring benefit to the formation of HKMG stack interface engineer. Before the silicide step switched, limited by the already formed silicide, the growth temperature of interfacial oxide layer couldn’t be higher than 600°C for NiSi unstability at high temperature, but now 800°C or 850°C will also be allowed. So we could adopt thermal oxide as HKMG stack interface layer.

In this paper, as interface layer of HKMG stack, chemical and thermal oxide were all studied. In 32nm/22nm node Bulk Planar CMOS technology, chemical oxide was grown through spraying DI water diluted Ozone on bare silicon substrate which was generally used in industry. It’s advantage was low thermal budget and the disadvantage was thermal unstability of Chemical ox during ALD HfOX growth. ChemOX would diffuse into HK dielectric, referred to Fig 1(b). It could also be observed very clearly at Si/ChemOX/RTCVD SIN structure , referred to Fig 2(b). From Fig 1(a) and Fig 2(a) , we had no doubt about the stability of thermal oxide interface layer. In this article, We chose three different thermal oxidation methods which were RTO, ISSG alone, ISSG with plasma nitridation[3][4]respectively. Considering the state of silicon substrate surface would severely affect the quality of ultrathin interface oxide layer, we also chose two different cleaning process which were HF 100:1 and BOE 100:1 last.

In conclusion, in order to improve HKMG stack characteristic in FinFET Transistor structures, different interface layer and cleaning process had been studied. Considering the thermal unstability of Chemical oxidation method currently used in industry, we plan to take high quality thermal ultrathin interface oxide into 22nm node and beyond.

References

[1] “Intel Reinvents Transistors Using New 3-D Structure”, http://ewsroom.intel.com/community /intel_newsroom/blog.

[2] “Roadmap for 22 nm and beyond” , H.Iwai, Volume 86, Issues 7–9, Microelectronic Engineering, 2009 .

[3] “Ultrathin DPN STI SiON liner for 40 nm low-power CMOS technology” Chan-Yuan Hu etc. Volume 54, Issue 5, Solid-State Electronics 2010 .

[4]“Plasma nitridation optimization of sub-15Å gate dielectrics” F.N. CUBAYNES etc. International Symposium on Silicon Nitride and Silicon Dioxide Thin Insulating Films, 28 April - 2 May 2003, Paris, France.
Perspectives of Group III-Nitride Material for Photoelectrocatalysis
Authors: Dietz Nikolaus
Published: February 2020

The potential and the physical properties of group III-nitride compound semiconductors will be discussed in the context of photoelectrocatalytic solar fuel structures. The band alignments in the ternary InGaN alloy system with respect to potential catalysts HOMO and LUMO states are assessed regarding the efficient charge transfer in photoelectrochemical cell structures. The presentation will also present the current status in group III-nitride materials fabrication and ternary alloy formation, their stabilization and integration into envisioned materials structures, together with challenges that have to be addressed to enable the full potential of group III-nitrides to contribute to high-efficient energy conversion.
Analysis of V-Shaped Pits Originated from Threading Dislocation in III-Nitrides Compound for Light Emitting Diodes
Authors: Ok Yulho , Kim Sunwoon , Kim In , Cho Hyungkoun
Published: February 2020

Light emitting devices (LEDs) made with III-nitrides compound on c-plane sapphire substrate using metal organic chemical vapor deposition (MOCVD) have so many threading dislocation defects due to the lattice mismatch. [1, 2] Threading dislocations were caused some problems such as poor luminescence and leakage current. In order to reduce the problems from threading dislocation defects, v-shaped pit initiated from threading dislocations used to construct in III-nitrides compound of LEDs. [3] V-shaped pits were made using different growth rate of etch lattice plane at specific growth temperature. (called mid-temp GaN in Figure 1) Furthermore v-shaped pits grown this method were served as insulator due to a lack of magnesium doping density in pGaN layer. Therefore leakage current through the threading dislocation defects can be prevented by characteristic of v-shaped pits. However some v-shaped pits still have a problem of leakage current. In this paper, dimension and electrical properties of v-shaped pits were separated for identify the causes of leakage current. Figure 1 shows a diagram of v-shaped pit originated from threading dislocation which has an open hexagonal inverted pyramid. The ‘g’ samples show lower current at reverse bias voltage than that of ‘ng’ samples which shown in Figure 2. It means the ‘ng’ samples are acting like leakage source at reverse voltage. Although the ‘g’ samples go to saturation around 5 reverse voltage, the ‘ng’ samples cannot be saturated even at 15 reverse voltage. (Figure 3) It means the ‘ng’ samples have higher carrier concentrations than ‘g’ samples. SEM images are shown in Figure 4(a)-4(d). The mean diameter and depth of the ‘g’ samples are 330.4nm and 306.7nm, respectively. (Figure 4(a), 4(c)) On the other hand, the mean diameter and depth of ‘ng’ samples are 417.7nm and 387.1nm, respectively. (Figure 4(b), 4(d)) As can be seen, the pits of ‘g’ samples are smaller than that of ‘ng’ samples. It means etch samples had a different starting point to making the v-shaped pits. The ‘g’ samples were started to make the v-shaped pits during the mid-temperature GaN growth. However the v-shaped pits of the ‘ng’ sample were made as soon as began of the mid-temperature GaN growth. Some of threading dislocation defects were subjected to tensile stress due to heat budget during high-temperature GaN growth, after that v-shaped pits began to form immediately due to the lower growth temperature. As a result, leakage current was expected to occur the v-shaped pits enlarged by the tunneling effect. In order to solve this problem, evaluation was conducted the step by step decreasing the growth temperature during high-temperature GaN growth. Eventually, a advanced result was obtained to control the dimension of v-shaped pits.
Correlation Between Temperature Dependent Photoluminescence and Origin of Room Temperature Ferromagnetism in Li Doped ZnO Nano-Flowers
Authors: Sahoo Satyaprakash , Revira Adrina , Misra Pankaj , Chatterjee Ratnamala , Katiyar Ram S.
Published: February 2020

Nanostructured ZnO is one of the most important dilute magnetic semiconductor materials (DMS) where room temperature ferromagnetism has been achieved by the doping of transition metals. However, transition metal doped ZnO are predominantly n-type materials. ZnO nanomaterial based DMS with p-type majority charge carrier are of great research interest as one can make use of both the magnetic as well as the optical proprieties for opto-electronic and spintronics applications. Recently, it has been reported that nonmagnetic Li doping in ZnO thin films show stable p-type characteristics with room temperature ferromagnetism. Thus there is a great need to understand both the optical and the magnetic properties in Li doped ZnO nanomaterials and a correlation between them. Here we report on the synthesis and studies of room temperature ferromagnetism and optical properties of Li doped ZnO nano-flowers (NFs). The room and low temperature SQUID measurement confirms the ferromagnetism in Li doped ZnO NFs. The temperature dependent photoluminescence measurements shed light on the origin of ferromagnetism. The comparison of the low temperature PL spectra with those of Li doped ZnO NFs shows appearance of distinct new peaks related to acceptor bound exciton and Zn vacancy in Li doped ZnO. Based on these findings from the optical studies we have correlated the origin of room temperature ferromagnetism with stable Zn vacancy in Li doped ZnO NFs. We also discuss the role of Li in stabilizing the Zn vacancy in particular lowering of the formation energy of the latter.
Zinc Oxide/Samaria Nanowires with Intense Photoluminescence
Authors: Enculescu Ionut , Matei Elena , Florica Camelia , Enculescu Monica , Costas Andrea , Evanghelidis Alexandru
Published: February 2020

Zinc Oxide is a very interesting material for its luminescent and electroluminescent properties. Electrodeposition allows one to prepare ZnO with desired morphology, structural and optical characteristics. Zinc Oxide can be doped with impurities in order to tune its electrical, optical or magnetic properties. When depositiong from a bath containing both zinc and samarium ions one deposits a bilayer of nanostructured ZnO/Sm2O3 with extremely interesting properties. The luminescence of the film is at least one order of magnitude higher than for a ZnO film deposited in similar conditions. When using a nanoporous membrane as template one can deposit nanowires containing both zinc oxide and samaria and exhibiting similar unusual high photoluminescence. Such nanowires can be easily used as building blocks for fabricating ultraminiaturised optic and optoelectronic devices.
Bright and Stable Quantum Dot Structures and Their Application to Display
Authors: Jang Eunjoo
Published: February 2020

The synthetic methods to prepare high quality quantum dots (QDs) in the colloidal phase have been developed, and it has been proposed that the advantages of the QDs can be practically realized in various optoelectronic devices in the near future. In particular, red light emitting CdSe-based QDs have been significantly optimized in terms of the emission wavelengths, quantum efficiency, and the tolerance against fabrication conditions such as high temperature curing or chemical treatments. However, QE and stability diminish rapidly as the size of QDs are reduced, because the density of the surface defects are more easily generated by the large ratio of surface to volume and the steric hindrance of capping ligands. Here, we present the novel structure of QD consisting of the alloy core and multi shells (AC/MS) of which the emission could be tuned especially in green region (502 nm ~ 563 nm). For the alloy core, the previously reported CdSe//ZnS interfused gradient alloy structure was used as a blue core (PL=458 nm). And, additional crystalline layer was grown on the surface of the blue light emitting alloy core to build CdSZnS multi shells. Since the CdS has smaller energy band gap than the alloy core and excitons can be delocalized all over the CdSe//ZnS/CdS crystalline structure, the emission of the CdSe//ZnS/CdSZnS QDs shifts to lower energy depending on the thickness of the CdS layer. The CdSe//ZnS/CdSZnS AC/MS QDs showed 100% of quantum efficiency and narrow spectrum width. The AC/MS QDs also have strong stability against intense radiation and thermal process so that they showed 70 % of external quantum efficiency as a green color converter on a blue light emitting diode. A white LED made with optimized red and green QDs showed high efficacy of 45lm/W and about 96 % of color reproducibility compared to the NTSC color space.
Lifting Defect Improvement of Plasma Enhanced Nitride
Authors: Yu Hyunkwan , Shin Dong Suk , Kang Sangkoo , Park Moonhan , Lee Nea-In , Ku Ja-Hm , Roh Yonghan
Published: February 2020

ABSTRACT

Plasma enhanced nitride (PESiN) has been applied for various layers in semiconductor device such as spacer, etch stopping layer, strain layer, hard mask. In order to match with each function of PESiN, process condition should be well optimized in terms of etch rate, stress, uniformity. In addition, defects which might be caused during process should be controlled for manufacturability. In this paper, Bubble shaped lifting defects that were observed open by PESiN were investigated. According to study for various cases of PESiN lifting defect, methods to control lifting defect were defined.

Lifting defects were observed after compressive PESiN deposition which is one of the strain technologies [1] that tensile PESiN is applied for nMOS and compressive PESiN is for pMOS as a contact etch stop layer to improve device performance in figure 1. Lifting defects were detected in wide pattern and wafer edge region on nickel silicide by compressive stress of PESiN and low adhesion between PESiN and nickel silicide. Buffer oxide, tensile SiN and compressive stress were split to reduce lifting defect, which led to lifting defect free in the sum condition of buffer oxide 150°Ê, tensile SiN 100°Ê and 2.5GPa compressive stress in figure 2. However, since buffer layer caused degradation of stress effect, bevel etch was processed before compressive PESiN. It showed lifting defect free due to adhesion increase between PESiN and nickel silicide in figure 3. The other lifting defects were observed after processing high density plasma inter layer dielectric (HDPILD) on stopper PESiN. Hydrogen radicals were generated during HDPILD process and these hydrogen radicals could be captured between SiN and silicon, which caused lifting defect. According to split of SiN thickness, lifting defects were shown in the range of 30°Ê~40°Ê SiN thickness. In the other hands, thicker SiN than this range prevented hydrogen trapping to SiN sub and thinner SiN than this led to hydrogen passing out through SiN in figure 4. According to study of HDPILD dependency, high deposition rate without hydrogen condition showed lifting defect reduction in figure 5. Since initial HDPILD layer was thicker in high deposition rate, hydrogen trapping could be prevented more.

In this paper, lifting defects by compressive stress and hydrogen trapping were introduced. According to analysis of lifting defect mechanism, several reduction methods were investigated such as buffer layer, pre bevel etch, SiN thickness dependency, post hydrogen effect. These various methods will be helpful to solve this kind of lifting defect for manufacturability.

References

[1] ] J. Huang et al., Thin Solid Films., (2009), P. 5
Boosting Supercapacitor Performance of Carbon Fibres Using Electrochemically Reduced Graphene Oxide Additives. (Oral; The Main Work Has Been Published Online On Physical Chemistry Chemical Physics Lately)
Authors: Cao Yachang
Published: February 2020

A kind of hybrid fibres as supercapacitor electrodes based on carbon fibres and graphene additives by a synchronous electrochemical reduction and deposition method was demonstrated. The electrochemically reduced graphene oxide coated carbon fibres (ERGO@CF) with only a small amount addition (~1 wt. %) of ERGO displayed excellent electrochemical performance in both aqueous and gel electrolytes. The superior capacitive performance could be attributed to the synergistic effect between wrinkled and porous ERGO sheets and highly conductive CFs.

Fig. 1(A) Schematic diagram of ERGO@CF. (B) Digital photograph of a home-made setup for continuous preparation of long ERGO@CFs. (C) (D) SEM image of ERGO@CF with gully-like porous structure of ERGO on the surface of CF.

In the electrochemically deposition process, GO sheets were gradually coated on the surface of CFs, meanwhile most of oxygen containing functional groups on GO sheets were removed, indicating that GO sheets were electrochemically reduced. The chemical structures of GO and ERGO were verified by Raman spectra and X-ray photoelectron spectroscopy (XPS).

The specific capacitance of an optimized single hybrid ERGO@CF fibre was measured to be as high as 22.6 µF cm-1 (10.3 µF cm-2) in 1 M Na2SO4 aqueous electrolyte at a scan rate of 10 mV s-1, which was around three orders of magnitude enhanced compared to pure CF. The hybrid fibre electrodes showed excellent capacitive stability after thousands of charge-discharge cycles.

Fig. 2(A) Cyclic voltammetry (CV) curves of a single ERGO@CF at different scan rates in aqueous electrolyte. (B) Galvanostatic charge-discharge curves of ERGO@CF at different current densities in aqueous electrolyte. (C) Ragone plot of a solid supercapacitor indicates that the energy density does not decrease significantly when the power density increases.

Solid supercapacitor that combined two ~250 hybrid ERGO@CF fibres together coated with gel electrolyte (PVA-H3PO4) was studied to possess a specific capacitance of up to 13.5 mF cm-1 (307 mF cm-2) at a current density of 0.05 mA cm-1. Meanwhile, the energy density did not decrease notably as the power density increased. The maximum power density of such a solid supercapacitor could reach 0.74 mW cm-1 (8.5 mW cm-2) and the maximum energy density was measured to be 1.9 µWh cm-1 (21.4 µWh cm-2), representing a relatively high values compared with similar fibre-like ones.

This fibre electrode material also offered advantages such as easy operation, mass production capability, mechanical flexibility and robustness, and could be easily mass-produced with the possibility to overcome the major hurdle in the development of large scale applications of graphene.
The Evolution of 3-Fold Symmetry Hexagon in Si Nanowire As a Function of Oxidation Time
Authors: Bae Jung Min , Lee Woo-Jung , Ma Jin Won , Kim Jung Hun , Cho Mann-Ho , Oh Seung Hun , Kang Chul
Published: February 2020

The advantage of Si over other semiconductor materials is that its thermally grown oxide, SiO2, provides a nearly ideal surface passivation layer. Recently, Si nanowires (NWs) and oxidized Si NWs have also received considerable attention as building blocks for nanoelectronic devices, and chemical and biological sensors. Numerous researches on electrical properties of the Si/SiO2 core/shell structure have been studied to utilize the Si NW into the Si based devices for past decades. Herein, we investigated the morphological characteristics of cross-sectional shape of Si NW core as a function of oxidation time, which is closely related in SiO2 shell thickness. In as-grown Si NW, cross sectional shape of Si core revealed 3-fold symmetry hexagon, not 6-fold symmetry hexagon. While thermal oxidation continued, 3-fold symmetry hexagon was transformed into triangular shape with roundish edge up to thermal oxidation of 2 hrs. The changing in the shape of the Si core during oxidation process can be understood by equilibrium crystal shapes lowering the surface free energy. In our oxidation system, we suggested the schematic modeling to calculate the initial diameter of the Si core NW before oxidation process. This is in good agreement with our experimental results. Furthermore, we found the distinguishable defect states formed into native oxide (broad peak near the 522 nm) and thermal oxide (sharp peak around 400 nm) from the low-PL spectra. The defects state of native oxide is attributed to neutral oxygen vacancy and that of thermal oxide is ascribed to the emission band of defects near Si direct band gap.
Improved Performance and Pt Reduction Technology in the Manufacturing of the MEA By Electro Spraying Process
Authors: Oh JI-Won , Na Hyunwoong , Nahm Sahn , Kim Yonghwan , Choi Hanshin
Published: February 2020

The purpose of this study is reduction of platinum consumption without loss of performance. Electro-spraying process was selected owing to practicable mass production, direct deposition of catalyst electrode on membrane, and without Pt loss during manufacturing process. It was optimized experiments for the asymmetric MEA to Pt reduction having regard to the reaction kinetics, functional layer was applied as to do decreasing of the mass transport, and heat treatment was practiced for the stability of the electrode. That was applied to the asymmetrically MEA by electro spraying.

Using JM 40wt%. catalyst, distilled water, nafion ionomer, and isopropyl alcohol, catalyst ink was prepared with an appropriate combination ratio. Cathode was fixed Pt loading amount to 0.4mg/cm2 and then asymmetric MEA was experimented by placing anode variable in 0.4, 0.3, 0.2 and 0.15mg/cm2 respectively. Performance evaluation was compared with an atmospheric pressure conditions and an additional fuel pressure of 0.5bar. Experimental results from Anode 0.15/Cathode 0.4mg/cm2 loading amount at 0.7V was measured power density of the 580 mW/cm2 and maxpower was measured the 644mW/cm2.
Electrochemical Characterization of an Electroactive Ureidopyrimidinone Derivative, a Four Hydrogen Bond Array Containing a Dimethylaminophenylurea
Authors: Clare Laurie A. , Smith Diane K.
Published: February 2020

Electron transfer reactions can be used to perturb the strength of hydrogen bonding interactions between organic molecules. When molecular redox centers are integrated onto hydrogen bond arrays, this combination can become a powerful tool for controlling binding strength in supramolecular complexes. Whether used for sensing devices, molecular machines or self-assembly, the strength of a hydrogen bond can also be enhanced simply by arrangement of hydrogen donor interactions (D) versus hydrogen acceptor interactions (A). Indeed, because of secondary interactions, dimerization constants of the DDAA 4 H-Bond array typically exceed that of the DADA 4 H-Bond array.1 By combining a DDAA 4 H-bond array such as Meijer’s ureidopyrimidinone1with an electroactive center such as the dimethylaminophenylurea, the strength of hydrogen bonding becomes tunable.

Cyclic voltammetry investigation, in nonaqueous solvents, of dimethylaminophenylurea (UHH), a DD 2H-bond array, show that without a guest present, there is one reversible oxidation wave in methylene chloride of one electron height. CV Digital simulations as well as UV-vis spectroelectrochemistry indicate a proton transfer from the radical species to the reduced U(H)H, followed by another electron transfer due to potential inversion to give the quinoidal cation, Scheme 1. With the integration of the dimethylphenylamino redox center, this mechanism would certainly complicate the dimerization of Meijer’s DDAA array.

Scheme 1. Proposed oxidation mechanism of UHH undergoing an overall one electron transfer due to proton transfer.

Due to the acidity of the urea NH that is part of the electroactive center, proton transfer could also occur as part of the electrochemistry associated with the DDAA dimer. We hypothesize that depending on the ratio of arrays substituted with an electroactive center versus those without, the DDAA sequence could change to a DDAD array. With all arrays containing an electroactive center the hydrogen bonding array would form an ADDA homodimer.

This presentation will cover cyclic voltammetry studies that includes concentration and scan rate dependence investigations on Meijier’ DDAA dimer equipped with a dimethyphenylurea electroactive center. Digital CV simulations and spectroelectrochemistry will be used to analyze experimental CV ‘s.

Figure 1. Meijer’s ureidopyrimidinone (Upy) 4 H-bond system without redox functionality as a DDAA homodimer.

Figure 2. Structure of the proposed heterodimer, DDAD array, as a result of half the concentration with an electroactive center and the other half without.

References

1.Beijer, F. H.; Sijbesma, R. P.; Kooijman, H.; Spek, A. L.; Meijer, E. W., Strong Dimerization of

Ureidopyrimidones via Quadruple Hydrogen Bonding. Journal of the American Chemical Society
1998, 120,

(27), 6761-6769.
Electrical Properties of Nano Aluminum-Polymer Composite
Authors: Grossman Kevin Daniel , Reid David , Saraf Shashank , Seal Sudipta
Published: February 2020

Conducting polymers have attracted a large amount of attention since 1970 for being lightweight, flexible, durable alternatives to current conducting systems. When certain conditions are met, insulating polymers can be made to conduct electricity with the addition of electrically conductive nanoparticles. The factors that influence a polymer composite’s conductivity include the concentration, size and inter-particle spacing between conducting nanoparticles. Metal nanoparticles are also well known for the enhanced conductive and optical properties compared to their bulk material counterparts. Metal nanoparticle-polymer composites show promise of great thermal, electrical and optical properties with potential applications as biosensors, electronics, thin film solar cells and other areas. Work was done to form a composite of polymer and aluminum nanoparticles to form a conducting polymer. With a synthesis process that allows precise control of particle size, concentration and dispersion of particles within a polymer solution, we are able to tailor thin film structures and measure electrical properties. Characterization of this material included electrical measurements such resistivity at different temperatures, dielectric relaxation spectroscopy, dielectric breakdown measurements, and impedance spectroscopy.
Quantifying the Active Sites on Single Redox Active Nanoparticle
Authors: Seal Sudipta , Ortiz Julian , Barkam Swetha , Das Soumen
Published: February 2020

Superoxide dismutases (SODs) are metalloenzymes which actively participate in cellular defense against oxidative stress mediated damage. SOD is a naturally existing enzyme in our body which scavenges the superoxide radical (O2−.) to form oxygen and hydrogen peroxide. The enzyme goes through an electrochemical single electron transfer process and contains only one active site per molecule. Cerium oxide nanoparticles (CNPs) are versatile nano-constructs which have the ability to switch in and out of 3+ and 4+ oxidation states exhibiting redox nature. This alteration of oxidation states leading to electrochemical reactions allows CNPs to mimic SOD enzyme and act as efficient antioxidants owing to multiple active sites for scavenging superoxide radicals. CNPs have been established owing to their unique regenerative antioxidant property and tested in vivo and in vitro in different areas of biotechnology and medicine involving excessive oxidative stress disorders. The simultaneous presence of two different oxidation states on the surface of CNPs gives rise to oxygen vacancies which act as hot spots for catalytic reactions. Understanding the antioxidant efficiency of CNPs is one of the crucial issues concerning its dosage. In this study we shall compare the efficacy of different single nanoparticles with different surface chemistry. The enzymatic kinetics are keenly studied to quantify the SOD mimetic efficiency in terms of electrochemical rate constants and turnover numbers as compared to the natural SOD. This study assist in proficient selection of nanoparticles for oxidative stress disorders.
Cerium Oxide Nanoparticles Decorated SAM Modified Gold Electrode for ROS Biosensing
Authors: Neal Craig J. , Saraf Shashank , Park Sanghoon , Das Soumen , Cho Hyoung J. , Seal Sudipta
Published: February 2020

Informatics is a new and flourishing sector in biomedical engineering with biosensors playing a crucial, central role. Self-Assembled monolayer (SAM) based biosensors constitute a large portion of these due to their simplistic design and broad application. Herein we present a cerium oxide nanoparticle (CNPs) functionalized SAM biosensor for amperometric reactive oxygen species (ROS) detection. SAM-based biosensors often times employ enzymes to detect analytes. These sensors are limited to particular pH, salt concentration, and temperature conditions specific to normal conditions for the enzyme. Operation outside these conditions can cause irreversible protein denature and loss of sensation. It is well established that CNPs has unique oxidase like activity.[1, 2] Therefore, by using inorganic CNPs, this sensor is able to operate at adverse conditions without loss of sensitivity. The inorganic material also prevents phase interactions which could result in bio-fouling. The presented sensor is able to detect extremely low concentrations for H2O2 and with high selectivity. Bare gold electrode was used as a substrate and coated with an SAM of mercaptododecanoic acid (MDDA), a well-established SAM polymer. The carboxylic terminus of MDDA was used for CNPs conjugation. Cyclic voltammetry and chronoamperometric testing was performed in phosphate-buffered saline and potassium hexacyanoferrate, a well-known redox couple. Hydrogen peroxide was infused in micromolar concentrations for sensing. Comparison to bare gold electrodes shows orders of magnitude greater sensitivity to [H2O2] and significantly more defined analyte selectivity.

References:

1. Hirst, S.M., et al., Anti inflammatory Properties of Cerium Oxide Nanoparticles. Small, 2009. 5(24): p. 2848-2856.

2. Gaynor, J.D., et al., Enzyme-free Detection of Hydrogen Peroxide from Cerium Oxide Nanoparticles Immobilized on Poly (4-vinylpyridine) Self–Assembled Monolayers. J. Mater. Chem. B, 2013.
Catalytic Activity of PrNixCo1-XO3 - Graphene nanocomposites for Sustainable Energy Application
Authors: Schrandt Matthew , Kolla Praveen , Smirnova Alevtina
Published: February 2020

Cobalt-containing perovskites ABO3 with praseodymium in A-site have been investigated as a possible candidate for cathode material for intermediate temperature solid oxide fuel cells. It was found that the conductivity of these compounds does not change significantly with temperature. At close to room temperatures they have conductivity similar to that at high temperatures (1580 S∙cm−1 at 50°C and 1031 S∙cm−1 at 1000°C).1 This could be favorable for the oxygen reduction reaction/oxygen evolution reaction (ORR/HER) catalytic activity while considering energy storage and generating devices, such as fuel cells or metal air batteries.

Pt catalysts are the leading catalysts for use in ORR.2 However, Pt is an expensive catalyst and with limited supply can not be considered a sustainable material for feasible application that is scalable in the economy. This calls for new solutions for catalyst materials that either mitigate the amount of Pt used in catalysts by developing hybrid catalysts, or to replace Pt altogether with a material with similar or better catalytic activity.

Praseodymium based pyrochlores (PrNixCo1-xO3-
d) with three concentration of Co ranging from x=0.1, 0.5, and 0.9 have been synthesized using a modified nitrate-glycine Pechini method and sintered at different temperatures, specifically 900°C and 1200°C. The XRD data shown in figure 1 indicates that the peaks responsible for the PrNixCo1-xO3-
d perovskite structure are present in the materials.1

The electrochemical performance of the perovskites sintered at 1200°C and tested in KOH (0.1M) demonstrated that PrNi0.9Co0.1O3-
d has the highest ORR activity in comparison to the two other perovskites. This activity gradually increases with an increasing ratio of cobalt to nickel at the B site.

The electrochemical performance for the samples with and without graphene in acidic (HClO4) and basic (KOH) solutions will be presented and discussed in terms of mass and catalytic activity in comparison to Pt/graphene as a baseline.

Fig. 1: XRD data PrNi0.5Co0.5O3-
d after 1200°C sintering.

Fig. 2: Cyclic voltammetry of PrNixCo1-xO3-
dfor x = 0.1 (solid line), 0.5 (dotted line), 0.9 (dashed line) in an oxygen purged KOH (0.1 M) solution.

REFERENCES:

1 S. Huang, Q. Lu, S. Feng, G. Li, C. Wang, J. of Power Sources
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2 W. Vielstich, H. Okokawa, and H.A. Gasteiger, Handbook of Fuel Cells: Fundamentals, Technology, and Applications, Wiley (2009).
Conductivity of Co-Ionic Composite electrolytes based on Oxygen-Ion and Proton Conductors
Authors: Park Jun-Young , Park Ka-Young
Published: February 2020

Solid oxide fuel cells (SOFCs) have attracted as clean power sources because of their have high energy conversion and fuel flexibility. In particular, the operation of SOFCs at intermediate temperature (IT) has lots of advantages such as fast start-up, reduced fabrication cost, extensive materials choice, and extended durability. IT-SOFC operations can be accomplished with highly ionic conductive SOEs at the IT.

Recently, SOFCs employ oxygen-ion or proton conductors as solid oxide electrolytes (SOEs). SOFCs based on oxygen-ion conductors such as yttria-stabilized zirconia (YSZ) and rare-earth doped ceria (RDC) have extensively researched. Until now, the most widely used SOE is YSZ. The YSZ SOEs present sufficient oxygen ionic conductivity at high temperature of about 1000°C. On the other hand, RDC SOEs present high ionic conductivity of the same order of magnitude at the IT. However, RDC SOEs exhibits mixed ionic-electronic conduction behaviors due to the reduction of Ce4+ to Ce3+at reducing atmospheres. This causes electronic transport within the SOE, resulting in significant decreasing cell voltage.

Compared to oxygen conductors, SOFCs based on proton conductor such as yttrium-doped barium zirconate (BZY) and yttrium-doped barium cerate (BCY) have received attention as alternative IT-SOEs, lately. These perovskite-type oxides have high proton conductivity in humid hydrogen atmospheres at IT. In addition, the activation energy for ionic conduction is much smaller than the oxide ion conductor. However, BZY is hard to be sintered with low grain boundary conductivity. And BCY show poor chemical stability in atmospheres containing H2O and CO2.

Hence, in this work, composite SOEs, mixed with the oxygen-ion (e.g. RDC) and proton conductors (e.g.BZY), are studied for decreasing SOFC operating temperature. The conductivity of composite SOEs can be enhanced due to highly interfacial energy between oxygen-ion and proton conductors with extra defects by heterointerfaces of two materials.

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* Corresponding authors: jyoung@sejong.ac.kr (J.-Y. Park)
Use of Langmuir Blodgett Thin Films for Rectification in Energy Harvesting Applications
Authors: Sharma Saumya , Stefanakos Elias , Ram Manoj
Published: February 2020

Tunnel diodes have been found suitable for use in high frequency rectification for energy harvesting applications in a rectenna. For tunneling to take place in a metal insulator metal diode for rectification at THz frequencies, an ultrathin pinhole free insulating layer must be deposited between the metal layers for the diode to operate with small turn on voltages.

Langmuir Blodgett (LB) thin film deposition is a useful technique that allows the deposition of conformal, uniform monomolecular layers with a precise control of thickness. Organic compounds such as Vinyl Stearate, 10-12 Pentacosadiynoic Acid and Porphyrin were considered for deposition onto a Nickel film and were later topped with a small metal contact to complete the metal insulator metal diode assembly.

Several characterization techniques were used to check the quality of deposition of the thin insulator film and to analyze its material properties. UV spectroscopy, atomic force microscopy and infrared spectroscopy techniques were utilized for this purpose. An electrochemical study was performed with 10-12 Pentacosadiynoic acid deposited using the LB method on an Indium Tin Oxide coated glass substrate. Along with these characterization results, the current voltage characteristics of the diode behavior as well as its suitability for detection or energy harvesting will also be reported.
An Extensive Computational Study of the Adsorption of Thiophene on Transition Metal Surfaces: Role of Van Der Waals
Authors: Rojas Tomas , Kara Abdelkader
Published: February 2020

Van der Waals (vdWs) interactions play a significant role in the determination of the adsorption characteristics at the interface between a molecule and a substrate. In this study, self-consistent inclusion of vdW interactions in density functional theory provides a good perspective to understand the interaction between organic adsorbates and inorganic interfaces. We present the results of adsorption of thiophene (C4H4S) on various transition metal surfaces with the goal of comparing the performance of five different vdW functionals (optB86, optB88, optPBE, revPBE, rPW86). Seven metallic substrates (100) are used for our study; three coinage metals (Au, Ag, Cu) and four reactive metals (Pt, Pd, Rh, Ni). The results show that vdWs inclusion enhances the interaction for Ag ( 0.08 to 0.73 eV), Au (0.14 to 0.86 eV), Cu (0.12 eV to 0.77 eV), Ni(1.56 to 2.34 eV), Pt (1.6 to 2.51 eV), Pd (1.67 to 2.54), Rh (1.74 to 2.96 eV). In addition, we performed calculations for adsorption heights along with analysis of the electronic changes (charge transfer, changes in the d-band of the substrate, and change in the work function) to complement our understanding of these systems.

This work is funded by the U.S. Department of Energy Basic Energy Science under Contract No DE-FG02-11ER16243
Cerium Nanomaterials on Cell Membrane Mechanical Property for Drug Delivery Studies
Authors: Ly Anh , Das Soumen , Barkam Swetha , Seal Sudipta
Published: February 2020

The use of nanotechnology in cancer treatment has been raising as one of the most important discoveries in science and technology. With nanomaterial as the new drug delivery system, scientists nowadays are able to find new ways to deal with cancer.

Cerium dioxide nanoparticles is a well-known functional rare earth material. Due to its unique properties, it has a wide range of applications in fields spanning: catalysis, electrochemistry, and biology (1). CNPs has been reported having excellent therapeutic potential, specifically abnormalities associated with oxidative stress. However, in order to have better understanding and development of the biomedical applications based on those nanomaterial, the impacts of CNPs on living organism needs to be fully studied.

In our research, CNPs with different sizes and shapes were selected. Specifically, nano-rods (~30-200nm), nano-cubes (~20-30nm) and nanoparticles (~3-20nm) fabricated by hydrothermal treatment were being chosen as the model nanoparticles for the studies. The normal skin cancer cells have been used as the living organism.

The mechanical property and the adhesion energy of cells’ membranes were analyzed with and without CNPs by using the Atomic Force Microscopy (AFM). From the Force-Distance spectroscopy mode and Hertz's model caculation, we were able to estimate the the elasticity of the cells membranes. Different concentrations (50μM, 125μM, and 250μM) of CNPs were added to the cells and then incubated for different time period (0, 15, 30 and 60 minutes). The results showed that with low concentration (50μM), the cell elasticity maintained around 20kPA. In those cells with 250μM of CNPs added, we noticed that there was a significant change in cell elasticity observed. The result also showed that by increasing incubation time, the cell elasticity has been increasing significantly and at 1hr incubated the changing in cell elasticity is maximum. However, there was no significant change in cell elasticity was observed over 1hr time period for 0.1μM and 50μM of CNPs. This result indicates that the elasticity of cell membranes depends on different nanostructures and nanoceria interaction/internalization to cell and can change significantly at high concentration but makes no effect to the mechanical property of cell at low concentration.

(1) A. Karakoti, S. Singh, J. M. Dowding, S. Seal, W. T. Self,,
39
, 4422-4432;(2010)