bluuebunny/crossref_metadata_2025 huggingface dataset:
Predictive Engineering of Coating Adhesion on a Molecular Basis
Authors: Utzig Thomas , Stock Philipp , Valtiner Markus
Published: February 2020

Molecular design of polymer/metal interfaces relies on understanding single molecular interactions and their scaling towards integral interactions at the meso- and macroscopic scale. Here, we will discuss how one can measure the interaction free energy of single interacting functional groups and polymers with electrified and corroding surfaces for predicting the stability of macroscopic polymer/metals bondings. In particular, we will show how single interactions scale with the number density towards the macroscopic level [1, 2], where a large number of single bonds interact simultaneously and in parallel. For this, we developed a synergistic experimental approach combining electrochemical Surface Forces Apparatus (SFA) experiments and single molecule force spectroscopy (SMFS) in an electrochemical Atomic Force Microscope.

First, in model experiments we can demonstate how macroscopic measurements scale linearly with the number density of a gold-amine bond at an electrified interface, providing gold-amine interaction energies of ~35 ± 2 kT at OCP. Using Bell-Evans theory together with non-equilibrium thermodynamics, we can show how a set of single molecule interaction forces measured by SMFS similarly converges to an interaction energy of 36 ± 3 kT. This demonstrates excellent predictive power of our newly developed scaling approach.

Second, and in addition to gold-amine interactions, we now tested a number of different bonds including hydrophobic, electro-active mussel-peptide/surface and metal/polymer [2] bonds with our model and find that our model is widely applicable, in particular also to electrified and corroding interfaces. In this context, we will discuss in detail how single molecule unbinding energy landscapes can be measured and utilized to predict scenarios where a large number of molecules simultaneously interact, giving rise to adhesive failure and coating delamination under corrosive and wet conditions. Our experimental strategy provides a unique framework for the molecular design of novel functional coatings through predicting of large-scale properties such as adhesion and molecular interactions in electrochemical systems based on experimentally determined single molecule energy landscapes.

[1] S. Raman et al. in
Nature Communications
, 5
(2014), 5539.

[2] T. Utzig et al. in Langmuir, 31(9) (2015), 2722.
A Novel, Highly Effective, Chrome-Free, Smart-Release, Economically Viable Corrosion Inhibitor- from Lab Kinetics through to Industrial Coating Incorporation
Authors: Dodds Patrick Charles , Williams Geraint , Ansell Phil , Glover Carol Frances
Published: February 2020

Novel, smart-release in-coating corrosion-inhibiting pigments for hot dip galvanised (HDG) steel, were investigated as a low cost replacements for hexavalent chromate. Organic anions were exchanged into the smart-release divynl benzene resin based pigment, dispersed in a model coating and analysed using an in-situ scanning kelvin probe (SKP) technique, for their effectiveness at preventing cathodic delamination. SKP allows rapid screening of the inhibitor-containing pigment when dispersed in a model organic polyvinyl butyral (PVB) coating. Each experiment lasts 24 hours, enabling a larger experimental through-put in comparison to traditional screening techniques, such as EIS or salt spray (ASTM-B117). SKP gives spacially resolved corrosion potential (Ecorr) profiles enabling identification of the delamination front and subsequent measurement of its progression and rate kinetics. Figure 1 shows plots of delamination distance vs. time for the anions screened in these experiments. Results indicate that a benzotriazolate-containing pigment system is the most effective, where delamination rates were reduced by 95% and the onset of cathodic delamination was increased by ca. 2160 hours from the point of initiation with an external electrolyte. It has been reported previously that benzotriazole is an effective corrosion inhibitor for a range of metals when in solution (1-5), the divynl benzene matrix allows benzotriazolate to be stored and released only when the coating encounters a corrosive electrolyte, via ion exchange mechanisms. Open circuit potential measurements show an increase in Ecorr measurements where benzotriazole is present in the experimental electrolyte suggesting anodic inhibition. Results from salt-spray testing carried out on a commercial coil coating are also presented where benzotriazole is shown to be effective after a period of 1000 hours. The current study suggests that a benzotriazolate-containing pigment system is a strong, environmentally friendly, contender to replace chromate for the inhibition of corrosion on hot dip galvanised steel.

1. Finšgar M, Milošev I (2010) Corros Sci 52:2737–2749.

2. Kosec T, Merl DK, Milošev I (2008) Corros Sci 50:1987–1997.

3. Aramaki K (2001) Corros Sci 43:1985–2000.

4. Müller B, Imblo G (1996) Corros Sci 38:293–300.

5. LEROY RL (1978) Corrosion 34:98–110.

Figure 1
(Invited) Atmospheric Corrosion of Zinc Magnesium Aluminum Coated Steel
Authors: Thierry Dominique , Persson Dan , Luckeneder Gerald , Stellnberger Karl-Heinz
Published: February 2020

Hot dip galvanized steel and zinc alloyed coated steel such as ZnAl and ZnAlMg (ZM) are used in the building industry and in the automotive industry. However, In the case of zinc coated steel with Al and Mg, there is still relatively scarce information on the long term performance under atmospheric weathering conditions. Although large efforts have been made to study the corrosion products formed on zinc under atmospheric weathering conditions (see for instance reference 1 and 2), very few data exist on HDG and zinc alloyed coated steel [5]

This work is a part of a larger research program were steel with different zinc coatings are exposed on a worldwide basis on well characterized exposure sites in Europe, Asia and North America, see table 1. Corrosion rates of hot dip galvanized steel and zinc magnesium aluminum (e.g. 2% w% of Al and 2w% of Mg) coated steel were determined after 1, 2 and 4 years of exposure under different climatic conditions.

The formation and development of corrosion products was followed by detailed analysis of samples exposed 0.5, 1, 2 and 4 years using XRD, FTIR-spectroscopy and SEM-EDS. For HDG the sulphate/carbonate ratio was highly dependent on the exposure site (with low values at marine sites and high values at industrial sites). A model of initiation and propagation of local corrosion on HDG has been proposed. The analyses of corrosion products on ZM coated steel revealed higher sulphate/carbonate ratio compared to HDG. This may be linked to the corrosion rate of the coating with less formation of hydrozincite.

The data are discussed in view of current knowledge in atmospheric corrosion of zinc, HDG and ZM coated steel materials [1-6]

 

Table 1. Test sites in the exposure program

Code

Name

Country

Distance to Sea(m)

A

Brest
France
<5

B

Bohus-Malmön (I)
Sweden
<5

C

Bohus-Malmön (II)
Sweden
300

D

Ijmuiden
Netherlands
2600

E

Cadiz
Spain
750

F

Jiangjin
China
̴900 km

G

Ostrawa
Czech Republic
̴500 km

H

Dubai
UAE
2000

I

Daytona Beach
USA
100

J

Quindao
China
10

K

Wanning
China
100

L

Bangkok
Thailand
35 km

M

Sattahip
Thailand
10

N

Singapore
SIngapore
10

 

 

 

References

1-I. Odnevall, C. Leygraf, Corros. Sci. 34 (1993) 1213–1229.

2- I. Odnevall, C. Leygraf, Corros. Sci. 36 (1994) 1551–1567.

3- N. Le Bozec, D. Thierry, M. Rohwerder, Dan Persson, G. Luckeneder and L. Luxem, Effect of CO2 on the atmospheric corrosion of ZnMgAl coated steel, Corrosion Science, 74, pp 379-386, 2013

4- E. Diller, B. Lescop, S. Rioual, G Nguyen, D. Thierry and B. Rouvello, Initial formation of corrosion products on pure zinc and MgZn2 examined by XPS: Corrosion Science 79, pp 83-88, 2014.

5- D. Persson, N. Le Bozec, T. Prosek, D. Thierry, G. Luckenader , Corrosion Science Vol 90, pp 276-283, 2015.

6- D. Persson, D. Thierry, N. Le Bozec: Corrosion products formation on Zn55Al upon exposure in marine atmosphere, Corrosion Science, 720, 2011.
Characterization of Ti-Based Foams for Biomaterials Applications
Authors: Sancy Mamié , Aguilar Claudio , Lascano Sheila , Guerra Carolina , Vejar Nelson
Published: February 2020

Development of titanium foams with low elastic modulus has increased its scientific and technological relevance due to the evident need to avoid the stress shielding problems related to stiffness mismatch with respect to bone. In this work we studied the synthesis and characterization of foams of pure Ti which present high potential for biomedical applications. Foams were obtained using NaCl (40, 50 and 60 %v/v), with particle size ranging from 150 to 350 mm, as space-holder. Powders and space-holder were mixed together and compacted under 200 to 800 MPa stress. NaCl particles were removed from the green compacts by submerging samples in distilled water at 60 °C (5 cycles of 4h). The green compacts were sintered at 1300 °C for 3 h in Ar atmosphere. Ti-based foams were characterized by X-ray diffraction, scanning electron microscopy, transmission electron microscopy, optical microscopy. In addition, electrochemical impedance spectroscopy (EIS) measurements were performed under potentiostatic conditions at the corrosion potential in Ringer solution. Results showed that Ti-based foams with tailored heterogeneous pore distribution may be obtained using space holder method. Using theoretical models the elastic modulus of foams was estimated between 10 and 25 GPa. The experimental EIS data revealed a CPE behavior of the foams for all exposure time studied. Not significant effect was observed in the impedance modulus at low frequency range (|Z|LF) for low compaction stress. However, the |Z|LF decreased markedly for higher compaction stress, which could be related to the increase of the stress raiser. From our results, we conclude that foams with 50 and 60 % of porosity are potential bone replacement materials due to their stiffness closer to human bone value.

Ackowledgements: The authors are grateful to Fondecyt Grant 1160604 and 1161444
Evaluation of Titanium Carbide Thin Film Coatings on Surface Microstructure Controlled WC-Co
Authors: Tanaka Chihiro , Saito Takeyasu , Okamoto Naoki , Suzuki Soichiro , Kitajima Akira , Higuchi Koji
Published: February 2020

Chemical vapor deposited (CVD) or physical vapor deposited (PVD) hard coating technique is widely used the cemented-tungsten carbide (WC-Co) for molds and cutting tools, which plays an important role in a lot of manufacturing industry. For example, titanium carbide (TiC), titanium nitride (TiN) and titanium carbonitride (TiCN) is one of the candidates to control surface properties in order to increase lifetime or to decrease friction coefficient of molds, tools and so on.

The film prepared by thermal CVD carried out around 1000°C has good uniformity and mechanical properties, which restricts substrates having low melting points, and also causes deformation of substrates. High temperature sometimes results in decarbonization of WC-Co surface which causes a significant decrease in toughness and transverse rupture strength. Plasma enhanced chemical vapor deposition (PECVD) or PVD has some merits as lower deposition temperature (< 500°C) than thermal CVD and high through-put, however, the film usually has low adhesion strength. Then, life of molds and cutting tools obtained PVD are sometimes shorter than that with CVD.

In this study, Several surface pretreatment methods were investigated to remove Co from the WC-Co surface and to increase surface roughness to enhance adhesion strength. The procedure include, Dry etching by CF4 plasma for 15 to 120min in the substrate temperature range from R.T. to 500°C. Chemical treatment with aqua regia (3HCl:HNO3) for 5 min at 25 to 60°C. After pretreatment, TiC coatings were formed by sputtering with TiC target or by PECVD from TiCl4/CH4. Surface roughness was evaluated by AFM. Crystallographic structure of WC-Co and TiC was evaluated by XRD. Hardness was evaluated by dynamic nanoindenter. Atomic concentration was determined by XPS.

Figure 1 shows maximum height roughness (Rz) and arithmetic average roughness (Ra) of WC-Co substrates after pretreatment. Rz and Ra got larger as increasing temperature of treatment conditions. In particular, substrate surface with aqua regia treatment at 60°C disappear Co peak.

Scratch test for PVD TiC coating on pretreated substrate revealed that critical load was larger than that with the film on non-pretreated substrate. When Ra was 150 nm, critical load was over 30N. The pretreated substrates surface by CF4 plasma and aqua regia have similar Ra value as 150 nm, however, the film with CF4 plasma exhibited no delamination and the film aqua regia exhibited delamination. The opposite trend could be due to the micro-level morphologies. The differences between PVD and CVD films will be discussed.

Figure 1
Study of Anti-Corrosion Coating Effects with the Preceramic Materials and Active Fillers
Authors: Bang Jung Won , Nguyen Minh Dat , Kim Younghee , Kim Soo-Ryong , Kim Byung-Ik , Kwon Woo-Teck
Published: February 2020

The ceramic materials have received attention as anti-corrosion coating materials due to their good chemical stability, the resistance of high temperature and pressure. However, the general ceramic materials have different coefficient of thermal expansion from metal substrates. We applied polycarbosilane (PCS) and polysiloxane as the preceramic materials for anti-corrosion coating on the carbon steel substrate (SA-210). The degree of shrinkage cracking of the preceramic materials can be modulated by the addition of active fillers and other composites. We also studied the anti-corrosion effects of the preceramic materials, alumina, sintering additives and active fillers by the various measurement methods: scanning electron microscope (SEM), energy dispersive spectrometer (EDS), X-ray diffraction (XRD), BET method, inductively coupled plasma – optical emission spectrometry (ICP-OES) analysis and thermal conductivity. The results revealed that the preceramic materials and active fillers had critical roles for anti-corrosion coating under high temperature oxidation conditions. Also, the results indicated that the combinations of the materials could be the strong potential as anti-corrosion coating materials in various industrial systems.
Substitutionally-Doped Intermediate Band Absorbers of Readily Tunable Composition
Authors: McCarthy Robert , Weimer Matthew S. , Haasch Richard , Schaller Richard D , Adam Hock S. , Martinson Alex B. F.
Published: February 2020

Intermediate band photovoltaics (IBPV) attempt to significantly increase photovoltaic efficiency by absorbing more photons to produce additional photocurrent without sacrificing significant photovoltage. Through creation of a density of states within the parent semiconductor gap, a partially filled intermediate band (IB) may be used as a stepping stone to allow photons with sub-band gap energy to be absorbed and generate extractable charge carriers in a two-part absorption process. Sandwiching the IB material between selective n- and p-type contacts (or the parent semiconductor) excludes this Fermi level from the contacts, thereby theoretically preserving the full photovoltage of the parent material. This design theoretcially increases the maximum efficiency of a solar cell from 40.7 to 63.2% (assuming a large concentration factor).

Substitution of V into In2S3 to form V0.25In1.75S3.00 is predicted to produce nearly ideal properties to maximize efficiency under concentrated sunlight, with a band gap of 2.1 eV, and an intermediate band 0.70 eV above the valence band. While powders of this material have been fabricated previously, we report the V
x
In(2–x)S3 thin films. Atomic layer deposition (ALD) is ideally suited to its fabrication as compositional doping/substitution can often be simply and reproducibly achieved with simple precursor pulse sequence control. This is in contrast to many physical deposition methods in which the source composition is fixed by the target allow for composition changes when the deposition rate of each element is nonequal. We utilize an oxygen-free process for growing In2S3 but periodically incorporate a novel vanadium precursor in place of the indium precursor to achieve continuous compositional control over V and In. The physical, optical, and electrical intermediate band properties as well as photoelectrochemical performance of the V
x
In(2–x)S3 films will be presented.

The figure shows the absorption coefficients for VxIn(2–x)S3 films as a function of the doping level x.

Figure 1
A Novel Poly(acrylonitrile)-Based Quasi-Solid-State Electrolyte for Dye-Sensitized Solar Cells
Authors: Su Yi-Han , Teng Hsisheng
Published: February 2020

The use of volatile liquid electrolytes limits the practical application of dye-sensitized solar cells (DSSCs) because of stability issues. Gel-type electrolytes have shown promising results in terms of cell stability and efficiency. Poly(acrylonitrile) has been known for its high ion solvation ability and structural stability.1 Herein, we report a quasi-solid-state DSSCs (QS-DSSCs) using gel polymer electrolyte (GPE) based on poly( acrylonitrile-co-methyl acrylate) (i.e. P(AN-co-MA)) dissolving a iodide-acetonitrile solution. The MA group rotates freely on the polymer chain to effectively coordinate the electrolyte solution into the polymer matrix.2By adjusting the polymer content, we can control the gelation time of the GPE for smooth electrolyte injection into the cells. No filler is needed to expedite the gelation process.

The QS-DSSCs exhibit higher short-circuit currents than liquid-state DSSCs (L-DSSCs). The polymer chains may have adhered to the TiO2films in the QS-DSSCs to suppress charge leakage and promote the photocurrent. However, the QS-DSSCs have smaller fill factors than the L-DSSCs, likely due to lower ionic conductivity of the GPE relative to the liquid electrolyte. Using the N719 dye as the sensitizer, the QS-DSSCs have a power conversion efficiency of 9.5 % whereas the L-DSSCs show a similar efficiency of 9.6 %.

Importantly, the proposed QS-DSSCs presented considerable improvements in long-term stability when subjected to accelerated aging. This developed GPE has presented a promising potential to replace liquid-state electrolytes used in DSSCs.

References

1. C. L. Chen, H. S. Teng, Y. L. Lee, J. Mater. Chem. 21 (2011) 628.

2. C. W. Tu, K. Y. Liu, A. T. Chien, C. H. Lee, K. C. Ho, K. F. Lin, Eur. Polym. J. 44 (2008) 608.

Acknowledgments: This research was supported by the Ministry of Science and Technology, Taiwan (104-2221-E-006-231-MY3, 104-2221-E-006-234-MY3, 105-3113-E-006-005, and 104-3113-E-006-011-CC2), and by the Ministry of Education, Taiwan, The Aim for the Top University Project to the National Cheng Kung University.
Thermal Stability of CuInSe2 solar Cell with Sputter-Zn(O,S) Buffer Layer As a Bottom Cell
Authors: Yu Hye-Jung , Wi Jae-Hyung , Lee Woo-Jung , Cho Dae-Hyung , Han Won Seok , Kim Seong-Yeon , Kim Jun-Ho , Chung Yong-Duck
Published: February 2020

The power conversion efficiency of solar cells with multiple sub-cells in a tandem device can be extended beyond the Shockley-Queisser limit for a single-junction device, shifting the absorption onset to longer wavelengths and reducing thermalization losses. Theoretical calculations have been reported that the optimum band-gaps of absorber materials for a series-connected two-junction are 1.72 eV for the top cell and 1.14 eV for the bottom cell, respectively. The CuInSe2 (CIS) solar cells are well suited to be used as bottom cell in tandem solar cells. In case of monolithic tandem solar cell, Cu(In,Ga)Se2 based-cells with CdS buffer layer are quite vulnerable to high temperatures above 200oC, destroying the p-n junction by the diffusion of Cd atoms. Thus, the thermal stability of buffer layer prepared on the absorber of bottom cell should be important factor in solar cell performance.

In this study, we fabricated CIS solar cell with sputtered-Zn(O,S) buffer layer as a bottom cell because Zn-based buffer layer has a higher thermal stability as compared with CdS buffer layer. The completed solar cells were heated up to temperatures of 200 - 400oC for 60 min under vacuum in order to trace the degradation of cell performances. To investigate the interface quality and degradation mechanism after post-annealing process, the drive-level capacitance profiling and admittance spectroscopy have being applied as an analytic tool, which gives an information on bulk defect states, carrier density and defect energy at p-n junction. The temperature dependent current density-voltage measurements were also performed in the dark, red and white light from a solar simulator. These results clearly present that there is clear correlation between thermal stability and solar cell performance.
Enhanced Photovoltaic Effect in Single-Wall Carbon Nanotube/BiFeO3 Heterostructure
Authors: Lee Ho Jin , Kim Hyo-Sun , Seo Young-soo , Choi Taekjib
Published: February 2020

Photovoltaic effect in ferroelectric materials have been revisited with energy applications because of visible-light-absorbing ferroelectrics and an anomalous photovoltaic effect, such as extremely large, above-band-gap voltages and polarization-induced electron-hole separation. BiFeO3, having a relatively low band-gap (~2.7 eV) is a potential visible-light-absorbing photoferroelectric materials. However, it is still limited to further enhancing photovoltaic efficiency due to a low photocurrent. In this work, we report an enhanced photovoltaic effect in single-wall carbon nanotubes (SWCNTs)/BiFeO3 photovoltaic heterostructures. High-purity metallic (M)- and semiconducting (S)-SWCNTs were seperated by using gel chromatography method and BiFeO3 thin films were grown on Nb:SrTiO3 substrate by pulsed laser deposition. M- and S-SWCNTs thick films are incorporated onto BiFeO3 for photovoltaic devices. For single BiFeO3/Nb:SrTiO3, we observed clear switchable diode and photovoltaic effects depending on ferroelectric polarizatioin directions. The S-SWCNTs/BiFeO3/Nb:SrTiO3 heterostructrues exhibited a large enhancement of photovoltaic performance compared with those of BiFeO3/Nb:SrTiO3 or M-SWCNTs/BiFeO3/Nb:SrTiO3. This heterostructure allowed a strong built-in field to be generated at the interface or the ferroelectric layer to efficiently separate photogenerated charge carriers and a wide range-light absorption due to near infrared-light absorbing S-SWCNTs and visible-light-absorbing BiFeO3. Under light illumination, this junction showed short-circuit current density of 1.73 mA/cm2 and open-circuit voltage of 0.21 V. Furthermore photovoltaic response was influenced by BiFeO3 thickness and SWCNT’s character. Our result implied that the heterostructure of high purity S-SWCNTs and high quality ferroelectric thin films could provide a route to highly efficient Photovoltaic devices.
(Invited) Green Solutions for Next Generation Photovoltaics: Using Wood, Glass, and Aluminum
Authors: Munday Jeremy
Published: February 2020

To address the terawatt energy challenge, a focus is usually placed on improving the cost-per-Watt of solar generated power. However, as the scale of photovoltaic energy production increases, so do concerns about material availability, environmental impact, and recyclability. Here I will present an overview of technologies that we have been developing to address these issues based on two concepts: (i) inexpensive renewable materials (e.g. wood pulp and glass) to make effective light trapping and scattering structures and (ii) the possibility of using hot carrier injection in aluminum nanostructures to convert sunlight to power. In the first part, I will discuss how cellulose fibers can be transformed into a transparent thin-film anti-reflection coating that can be applied to virtually any solar cell technology. I will give two examples of solar cells that have efficiency improvements >20% as a result of these coatings. In the second part, I will discuss loss mechanisms that are found in typical solar cells and will specifically address ways to capture energy that is usually lost as heat due to the cooling of excited carriers prior to collection. I will present trade-offs for these different schemes and future directions for high efficiency, green photovoltaics.
(Invited) Innovation and Challenges of 3-D NAND Flash Technology
Authors: Kim Ki-Seog , Kim Jin Woong , Jin Kyo-Won
Published: February 2020

NAND Flash has been improved by increasing the bit cost competitiveness and performance and enlarged its range of applications. Especially this cost reduction and performance improvement let the NAND Flash demand be increasing rapidly in the SSD applications. Needs of the market is demanding a high capacity and high speed of the NAND Flash for the information increase and exchange. Needs of these markets could be satisfied by implementation of a continuous scale down and multi bit. But 2D NAND Flash is not only faced with the difficulty of the scale down in a confined space, showing even marginal situations quality and performance secured in accordance with the scale down. 3D NAND Flash was able to break through the limit of the two-dimensional space by the vertical arrangement of cells in three-dimensional space. In this paper, we look at the critical technical elements for the vertical arrangement of 3D NAND Flash Cell and consider innovation and technology challenges of those elements.

3D NAND Flash meets the demand of the high density memory of the market by increasing the cell number per unit area with the increase of vertical stacks. This paper reviews the necessary stack number to meet the needs of the market and considers increasing the difficulty of the pattern formation increase with the high aspect ratio by increasing the stack height. . It also reviews some attempts to overcome the difficulty of the pattern formation for an effective bit cost reduction.

3D NAND Flash is there a big difference in electrical characteristics of 2D NAND Flash. First, we will compare the difference of the main characteristics of 3D NAND Flash and 2D NAND Flash. And we will look at the changes and challenges of the main electrical characteristics depending on the Stack increase for increased bit Cost reduction.
Double Layers-Stacked 3D 1D1R Crossbar Rram Integrating a Diode Selector with Rectification Ratio of ~109
Authors: Yoon Kyung Jean , Yoo Si Jung , Park Tae Hyung , Kwon Yeong Jae , Kwon Dae Eun , Hwang C. S.
Published: February 2020

The F2-cell sized 1diode-1resistive switching memory (1D1R) crossbar accompanied by excellent rectifying characteristics is presented. Each diode and memory comprising the 1D1R is fabricated at room temperature, which is optimized for the integration of stacked layers excluding the thermal disruption issues over repetitive stacking procedures. The maximum rectifying ratio of 1.4x109 (at the reading voltage 2V) in the low resistance state of RS memory was achieved in a planar 2x2 um2 crossbar, which is the highest value for the rectifying ratio obtained in the RS memory devices reported to date, and enough to apply in ultra-high density CBA of up to 1Gb. A reliable memory operation with the window of ~103 - 104 based on unipolar RS phenomenon in the TiO2 switching layer is observed from operation current of a few hundred μA for set and a few mA for reset process, respectively, which means relatively lower operation power compared to those in the previously reported TiO2 URS system.The structural and chemical analysis for such low power, highly rectifying property based on SEM, TEM, EDS, XRD was also provided. Furthermore, Resistive switching random access memory (RRAM) operation of erasing, programming, and reading a selected cell not being interrupted by sneak currents from neighboring cells was demonstrated in a 4x4 crossbar array with double-layers 3D stakced device structure.
The Origin of Traps Responsible for Localization and Charge Transport in Memory Devices
Authors: Gritsenko Vladimir A.
Published: February 2020

High-κ dielectrics are used now in ReRAM, FeRAM and charge trap (TANOS) flash devises. In present report the nature of deep traps responsible for the charge transport in the most important high-κ dielectrics of flash devices is considered [K.A. Nasyrov and V.A. Gritsenko, J. Appl. Phys.
109, 097705 (2011); V.A. Gritsenko, T.V. Perevalov and D.R. Islamov, Physics Reports
613, 1-20 (2016)].

The charge transport in high-κ dielectrics is controlled by electron and hole traps. In HfO2 charge transport is controlled by trap assisted tunneling between traps [D.R. Islamov, V.A. Gritsenko, C.H. Cheng and A. Chin, Appl. Phys. Lett.
105, 222901 (2014)] (Fig.1). Thermal trap energy in HfO2 is equal to 1.25 eV. The trap nature in HfO2 was studied with luminescence experiments. Blue luminescence band near 2.7 eV has excitation energy at 5.2 eV (Fig.2). Absorption peak of oxygen vacancy in HfO2 has equal energy as blue band excitation. Hence, the 5.2 eV excitation peak and 2.7 eV luminescence band are related to oxygen vacancies [T.V. Perevalov, V.Sh. Aliev, V.A. Gritsenko et al., Appl. Phys. Lett.
104, 071904 (2014)]. The photoluminescence Stokes shift (5.2-2.7)/2=1.25 eV is equal to thermal trap energy (Fig.3). So, the oxygen vacancy in HfO2 is the electron trap [V.A. Gritsenko, T.V. Perevalov and D.R. Islamov, Physics Reports
613, 1-20 (2016)].

Similar experiments were made for Al2O3, ZrO2, Hf0.5Zr0.5O2, Si3N4. It was concluded that in HfO2, Al2O3, ZrO2, HfZrO2 the oxygen vacancies are electron and hole traps. In Si3N4 the Si-Si bond is responsible for electron and hole localization and the charge transport [V.A. Gritsenko, Electronic structure of traps in silicon nitride for flash memory devices, chapter in book“Thin Films on Si: Electronic and Photonic Applications”, accepted for publication by “World Scientific Press”, 2016].

Figure 1
Magnetic Conductive Filament Formed in the Reram Device with Ferromagnetic Electrode
Authors: Yoshida Hayato , Shimizu Tomohiro , Ito Takeshi , Shingubara Shoso
Published: February 2020

We have studied electrical transport properties of the ReRAM device with ferromagnetic electrode, in order to understand origin of the nano-conductive filament (NCF) which was formed in the low resistance state (LRS). We observed anisotropic magnetoresistance (AMR) in the device having ferromagnetic electrode at one or both sides of electrodes. [1, 2] The device structure is Ni(40 nm)/HfO2(3.8 nm)/FeNi(40 nm). The size of the cross-point device area is 1×1 μm2. The HfO2 layer was deposited by reactive sputtering using Ar and O2mixture gases.

Figure 1 shows the resistance switching characteristics of the ReRAM device with two ferromagnetic electrodes. The bipolar operation was observed. We measured magnetic conduction property of the LRS, as shown in Figure 2. Direction of the magnetic field is in-plane and parallel to the Ni top electrode. The structures of the devices in Figure 2-a and 2-b are same, but the shapes of magnetoresistance were quite different. Negative magnetoresistance appeared in the sample #1 (Fig.2-a), however, positive magnetoresistance appeared in the sample #2 (Fig.2-b). Both cases showed hysteresis property against change in the magnetic field, and there are abrupt changes in MR ratio around 200 mT. These magnetoresistance properties are considered to be anisotropic magnetoresistance. Positive MR appears when magnetic field is parallel to current, and negative MR appears when the magnetic field is perpendicular to the current. It is suggested that NCF is parallel to the field for #2, and perpendicular to the field for #1. In our samples, dielectric layer of HfO2surrounds the bottom Ni electrode, and NCF formation occur either at the top or at the sidewall of the bottom electrode. The abrupt MR jump may be related to single domain switching in the narrow magnetic NCF, and detailed discussion based on micro-magnetic simulation is in progress.

References

[1] S. Otsuka, D.Ito, Y.Hamada, T.Shimizu, and S.Shingubara, Jpn. J. Appl. Phys. 54, (2015) 05ED02.

[2] S.Otsuka, Y.Hamada, T.Shimizu, and S.Shingubara, Applied Physics A, 118 (2015) 613-619.

Figure 1
Reversible Phase Transition in Gete through Resonance Bond Swiching
Authors: Cho Mannho , Yang Wonjun , Kim Dasol , Park Seungjong , Ahn Min , Han JeongHwa , Jung Hoon
Published: February 2020

Phase change materials, especially those along the GeTe-Sb2Te3 tie-line (GST), have been widely used in applications of memory devices. Using these materials, information can be stored as optical and electrical change contrast arising from thermally induced structural transitions between the crystalline and amorphous phases. Amorphous phase is obtained by heating the material of crystalline phase upon melting temperature and cooling it fast enough so that it solidify in the amorphous phase. On the other hand, crystalline phase is obtained by heating the material of amorphous phase during relative longer time (a few ns) than amorphization time within appropriate temperature range between crystallization temperature and melting temperature. Contrary to this relatively small difference of heating condition, their physical properties are extremely different from each other. Besides, their fast switching properties and rather good reversibility show promising characteristics for phase change materials as a candidate material for universal memory as well as a most intriguing topic in material society. Despite of these specific material properties, the fundamental reasons for this reversible and fast transition are still in a debate and needs to be understood more considerably as a view point of local structure and orbital environment. Many of the previous studies for understanding phase change mechanism concentrated in comparison of orbital structure between the crystalline phase and amorphous phase. However, the investigation on the modified crystalline phases which is weakly perturbed by thermal variation or external stress could show possible phase transition path.

In this study, using uni-axial stress (bending stress), the crystalline GeTe is modulated to have reversible structure deformation which gives rise to drastic change on optical property with resonance bond breaking. Modulated GeTe also shows reversible electrical change caused by orbital rearrangement and irreversible electrical change caused by defect formation. A stress which is relatively smaller thermodynamic perturbation than heat also can be an important variable in phase change mechanism and it might support the reason why both of set and reset state in phase change memory contain various of chemical states.
Hopping Conduction in Intermediate Resistance State of Tantalum Oxide Resistive Switching Memory
Authors: Huang Jiu-Xing , Chen Jen-Sue
Published: February 2020

Resistive switching memory with a simple MIM (metal-insulator-metal) structure has the characteristics of high operation speed, high retention time, low operation voltage. Generally, the resistance switching mechanism is strongly related to defect states in oxide and the electrode/oxide interface. Based on I-V sweeping curves, Ta/TaOx/Pt device can be operated in bipolar mode, with writing at positive bias and erasing at negative bias. Different resistance states are achieved in the device by controlling the reset stop voltage under bipolar mode operation. According to the I-V measurement at various temperatures, it is observed that conduction mechanisms are different in three resistance states of the device. The low resistance state (LRS) shows ohmic conduction with a semiconductor-like behavior. This situation can be interpreted by the existence of the oxygen vacancy filament connecting the top and bottom electrodes. The high resistance state (HRS) is governed by Schottky emission conduction. The intermediate resistance state (IRS) shows hopping conduction. It can be regarded as changing of interior state of the active layer between HRS and IRS.

To characterize separate contribution to the total resistance from individual component, complex impedance spectroscopy is used to study three resistance states of the device. It is shown that HRS and IRS can be described with an equivalent circuit consisting of the major components R
1, R
2, R3, C1and C
2, and LRS can be characterized with an equivalent circuit consisting of the major components R
1, R
2, R3, C1. These components show a strong dependence on the reset stop voltage, which can be explained in the framework of oxygen vacancy model and conductive filament concept.

According to results of temperature-dependent I-V measurement and complex impedance analysis, different current conduction mechanisms and values of major components in equivalent circuit in three resistance states can be attributed to changing of the filament structure and the oxygen vacancy distribution.
(Invited) Two-Terminal Selectors Enables Non-Volatile Memory and Neuromorphic Computing Applications
Authors: Yang J. Joshua , Wang Zhongrui , Joshi Saumil
Published: February 2020

Sneak current path issue is a critical challenge in memristor crossbar arrays used for non-volatile memory and neuromorphic computing, which can be mitigated by utilizing a selector device in series with each memristor. For this purpose, the selector needs to possess a highly nonlinear current-voltage characteristic. In addition, for neuromorphic computing applications, dynamics originated from cation diffusion process is crucial for the functions of synapses in intelligent bio-systems. Memristor has been a leading candidate to emulate synapse for neuromorphic computing. Due to the lack of such dynamics in a typical memristor, the emulation of memristor to a synapse has been function-specific and cumbersome.These dynamics can be readily incorporated into some selector devices that operates based on cation motion. The highly nonlinear current-voltage characteristic of the selectors enables a large scale crossbar array. Meanwhile, its dynamics with the same physical origin of its bio-counterpart lead to a natural, direct and comprehensive emulation of a variety of important synaptic functions.
(Invited) Electrostatic Field and Non-Thermal Plasma for Handling and Processing Bio-Molecules and Cells
Authors: Mizuno Akira
Published: February 2020

Electrostatic field is an important tool for handling fine objects such as biological molecules and cells. Non-thermal plasma generates reactive radicals. Long life-time radicals can migrate in liquids to penetrate membranes of cells and tissues. Electrophoresis, or Coulombic force has been widely used in biology for separation of cells and molecules. Dielectrophoresis in non-uniform AC-field uses gradient force. Since AC voltage can be applied to conductive liquid with minimum generation of bubbles, dielectrophoresis is an important tool for handling living cells and micro-organisms. Due to polarization, gradient force appears on particles of neutral charge, and magnitude and direction of the gradient force depend on the frequency response of the objects. Gradient force can be generated using a focused laser without using fixed electrodes. Biological cells are pulled into the laser focus where E-field is high, and they are trapped. This is called laser tweezers, and is a convenient tool for handling microbes and fine objects with diameter range between 0.2 – 5 micro-meter. Laser tweezers cannot hold DNA molecules of random-coiled shape, because they are too thin (2 nm diameter). The globule transition of DNA molecules can be used to fold random-coiled DNA into a solid globule DNA. This transition is reversible, controlled by concentration of counter ions in medium. Globule DNAs, therefore, can be stretched again. Globule DNAs are manipulated by laser tweezers. Droplet-in-oil emulsion is a suitable container to be manipulated using electrostatic force or laser tweezers. This emulsion system can be used to conduct PCR amplification starting from single fragment of DNA. High electric field causes reversible or irreversible puncture of membrane of cells. This phenomenon can be used for cell fusion, infection of genes and chemicals, cell fusion, or sterilization. To punctuate cell membranes, reactive radicals are also effective. Radicals are generated in NTP and injected into liquid. Certain long-lived radicals migrate in the liquid and penetrate into cells through membrane or protein shell. 
E.coli or B. subtilis spore in liquid was exposed to NTP, either DBD(dielectric barrier discharge) or a plasma jet with Ar or He. Analysis using decay of GFP (green fluorescent protein) fluorescence proved that oxidative radicals are penetrating through the membrane into cells. Exposure of NTP to Bacteriophages indicated that protein shells are damaged at first, and that double stranded DNA is stronger than that of single stranded genes of the phages. In conclusion, electrostatic force and NTP are effective tools for handling and for processing biological particles including cells, viruses and molecules. Wide range of applications are still to be developed. Several examples will be reported of the application of electrostatic field and NTP in handling and processing of cells and single DNA molecules.
(Invited) Plasma Assisted Preparation of Low Pt Content Proton Exchange Membrane Fuel Cell Anode Catalysts
Authors: Matolin Vladimir , Dubau Martin , Ostroverkh Anna , Lavkova Jaroslava , Matolinova Iva
Published: February 2020

Pt doped cerium oxide thin films with a nano-porous structure was prepared by reactive rf magnetron deposition on a fuel cell gas diffusion layer (GDL) coated with nitrogenated amorphous carbon films (CNx) as an interlayer. We show that the structure and morphology of the cerium oxide-CNx composites depend on the oxygen and nitrogen concentration in working gas used for catalyst deposition. Considerable plasma erosion of the carbonaceous interlayer accompanied by the formation of highly porous carbon/cerium oxide bilayer systems is reported. Oxygen plasma etching of the carbon interlayer occurring simultaneously with cerium oxide film growth is considered to be the driving force for the formation of cerium oxide film nanoporosity with large active surface.

Thin film techniques permits to grow the catalyst film characterized by highly dispersed platinum showing high hydrogen oxidation activity and stability. These new materials may help to substantially reduce the demand for expensive noble-metals in proton exchange membrane fuel cell (PEMFC) catalytic applications.

We measured Pt-CeOx thin film anode catalyst activity in hydrogen PEMFC and compared it with performance of a standard reference cell. We showed that membrane electrode assembly (MEA) made by assembling Pt-CeOx/CNx anode, containing 2-4 μg per cm2 only, and a reference standard cathode can deliver 1.2 W/cm2 power density.
IR Laser Modifications of Anodic Tantalum Pentoxide for Photonic Applications
Authors: Kulpa Alina
Published: February 2020

Making waveguides requires modification of material along a waveguide path in such a way that conditions for light propagation are advantageous along the waveguide but not so much in surrounding material. Usually, waveguides are produced with micro or nano photolitographic techniques that later require some wet chemistry, and wet or dry etching processes, or in-diffusion processes.  Here we are presenting our experiments on non photolitographic modification of electrochemically prepared tantalum pentoxide, Ta2O5, for possible photonic applications. The e-beam evaporated thin tantalum layers on glass were anodized at 23◦C in the 0.5% H2SO4 electrolyte. After anodization samples were rinsed with deionized water and blow dried with nitrogen gas. Laser material modifications were performed in an OPTOMEC, Inc. Aerosol Jet Printer, Model AJ300CE that was equipped not only with a pneumatic and an ultrasonic jet printing set ups, but also with a UV source and with a IR laser. The laser was static over a platen where a sample was located. The laser beam was perpendicular to the platen. Laser writing was done by moving the platen. The platen motion (+/- 1um) was computer controlled and that practically allowed any design. Any *.dxf design files were transformed into the program files that run the system. Straight lines were tested for various laser powers. The width of lines was laser power depended. The circular designs and random designs were generated at the constant laser power and at the constant platen speed. Zeiss optical microscope images of samples were collected without a filter. The microscope light was perpendicular to the surface of the samples. All laser inscribed patterns were very bright compared to the rest of the samples - Figure 1. Figure 1. The IR laser inscribed pattern in anodic Ta2O5 sample. The line with is ~115um. * Electrochemical Society Active Member

Figure 1
Metallization of Three Dimensional Microstructure Using Electroless Plating
Authors: Liao Ying-Chih , Huang Kuan-Ming , Chen Yung-Jian , Chung Tien-Tung
Published: February 2020

We report a method for metal coating over complex three dimensional cured ormocomp structures. Complex three dimensional micro structures are fabricated by two photon polymerization technique. We use an electroless plating method to coat a thin silver particle film onto the sample surface while leaving the relatively hydrophobic substrate surface uncoated. Our technique demonstrates a simple, direct approach to produce 3D metallic micro structures with arbitrary shapes and can be applied to metamaterials fabrication.

Figure 1
Influence of Cooling Rate on Coercivity and Microstructures in Hot-Deformed Nd-Fe-B Magnets By Nd-Cu Electrochemical/Electroless Deposition
Authors: Kwon Jeehye , Yoo Dayoung , Park Jieun , Lee Dongyun
Published: February 2020

In order to produce a high performing Dy free NdFeB permanent magnet for use at high temperature, control of grain size and interfaces is a significant factor: fabrication of magnetic domain-sized grains aligned in a specific direction and well-separated interfaces by non-magnetic materials. In this study, we used a melt spun powder of several tens of nanometer to produce domain-sized grains and then hot-pressing and dye-upsetting processes were performed to form anisotropic-grained NdFeB magnets. Now, we focused on to coat thin layers in between grains to produce well-separated interfaces by non-magnetic species. For that purpose, we used a well-known grain boundary diffusion process, GBDP. Nd-Cu system was chosen because of making lower melting eutectic alloys, and electrochemical and electroless deposition methods were adopted for mass production.

Nd and Cu were deposited by electrochemical and electroless methods, respectively followed by heat treatment in vacuum at 600°C for 25 min. And then they were cooled down in three different ways; furnace cooling, oil cooling at room temperature, and frozen oil cooling. By controlling the microstructures of the interfaces, we can restrict the reverse of magnetic domain mostly generated by defects and grain growth of the NdFeB raw materials. Interfacial microstructures could be controlled by heat treatment especially on cooling rate after GBDP. As a result, it was found that the Nd-rich phases were well distributed in the grain boundaries with the cooling rate. It was confirmed that the change of interfacial microstructure influenced on the magnetic properties, e.g. coercivity, remanence. In case of room temperature oil cooling, coercivity was increased 15.65kOe to16.37kOe, while the coercivity was reduced by frozen oil cooling. Presumably, α-Fe phase decreased with increasing cooling rate which induced increase of coercivity. On the other hand, main phase of NdFeB might be transformed to amorphous phase with further increase of cooling rate that caused decrease of coercivity. In order to identify the phases during GBDP and cooling process, an intensive TEM work will be presented in this presentation.