bluuebunny/crossref_metadata_2025 huggingface dataset:
(Invited) Atmospheric Pressure Microplasma Jet: Properties and Applications in Synthesis of Nanoparticles
Authors: Zhong Xiao-Xia
Published: February 2020

Atmospheric pressure microplasma jet: properties and applications in syntheses of nanoparticles (invited)

Xiao-Xia Zhong

State Key Laboratory of Advanced Optical Communication Systems and Networks and key Laboratory for Laser Plasmas (Ministry of Education), Department of Physics and Astronomy, Shanghai Jiao Tong University, Shanghai 200240, China. Atmospheric pressure microplasma jets are usually characterized with vacuum free, high electron temperature (several eV), and low gas temperature (room temperature). Being with the clear advantages such as clean or environmental friendly, fast, more and more attentions have been paid on atmospheric pressure microplasma assisted electrochemistry and its application in nanofabrication. In this talk, non-equilibrium properties, instability and nonlinearity of atmospheric microplasma jet are presented. [1-6] The non-equilibrium state of microplasma was studied as a function of capillary size, gas distance, gas flux and composition, etc. The unstability and nonlinearity of microplasma was discussed with water acting as anode and cathode respectively. The understanding of the thermodynamics and the nonlinearity of the plasma will help us to get an atmospheric pressure microplasma jet with controllable plasma density and temperature. Ecofriendly syntheses of Au Nps, Ag Nps, Au-Ag nanoalloys, carbon nanodots are also presented. [7-10] Experimental parameters such as plasma power, solution composition, process time, etc. play an important role in the syntheses of nanoparticles and deep investigations are still under way.References: [1] Y. Lu, S. F. Xu, X. X. Zhong et al., Europhys. Lett. 102(2013) 15002 [2] S. F. Xu, X. X. Zhong, Appl. Phys. Lett. 103 (2013) 024101 [3] S. F. Xu, X. X. Zhong, Phys Plasma 22 (2015) 103519 [4] S. F. Xu, X. X. Zhong, Phys Plasma 22 (2015) 033502 [5] S. F. Xu, X. X. Zhong, Phys Plasma 22 (2015) 103519 [6] A. Majeed, X. X. Zhong, S. F. Xu et al., Plasma Process. Polym. 2016, DOI: 10.1002/ppap.201500199. [7] X. Z. Huang, X. X. Zhong et al., Nanotechnol. 24 (2013) 095604 [8] X. Z. Huang, Y. S. Li, X. X. Zhong et al., Nanoscale Res. Lett. 9 (2014) 572 [9] T. T. Yan, X. X. Zhong et al., Chem. Commun. 50 (2014) 3144 [10] X. Z. Huang, Y. S. Li, X. X. Zhong et al., Plasma Process. Polym. 12 (2015) 59
Plasma-Assisted Deposition of Carbon Nanowalls for Detection of Organic Vapours
Authors: Cvelbar Uros , Slobodian Petr , Kondo Hiroki , Sekine Makoto , Hori Masaru
Published: February 2020

One of the grand challenges in material science is to develop the efficient and low-cost sensors for quick detection of various toxic and carcinogenic molecules, which require rather lengthy procedures or costly techniques for detection. These challenges can be tasked with carbon nanowall-based sensors, where the thin film maze-like structures are deposited on silicon substrates with plasma-enhanced chemical vapour depositions. These sensors demonstrate the high sensitivity in response, selectivity and reversibility for the vapour detection of volatile organic compounds, when tested by an electrical resistance method during adsorption and desorption cycles. The maze-like structures of carbon are composed of several layers of vertically aligned sheets - mostly graphene.[1,2] The structures are deposited from two different plasma gas mixtures generated either in CH4 or C2F6 with H2. [3] Herein the neutral H atoms are generated in surface wave plasma region driven by a 2.45 GHz microwave power supply and then mixed with CH4 / C2F6 and deposited in capacitively coupled plasma region operating at 100 MHz. By variating plasma processing parameters, we are able to achieve even different wall-to-wall distances ranging from 50 nm and 300 nm when prepared on silicon wafer substrate. [4] Further these structures are subjected to different organic vapours of: DMA; urea; iso-pentane; diethyl ether; acetone; methanol; different hydrocarbons; etc. in order to evaluate the relationship between the change in resistance, molecular weight of the adsorbent, the polarity and the bonding/interaction type. [4] For assessment and unravelling the detection mechanisms different surface analyses methods (XPS, Raman, FTIR, SIMS, UV-Vis) are applied prior, between and at the end of molecule detection. The properties of carbon nanowalls are then linked, and will be discussed in respect to the properties of detected molecules.

References:

[1] M. Hiramatsu, M. Hori, Carbon Nanowalls: Synthesis and Emerging Applications, Springer, Wien, 2010.

[2] M. Ito, K. Murata, K. Aiso, M. Hori and T. Goto, Appl. Phys. Lett., 1997, 70, 2141.

[3] M H.J. Cho, H. Kondo, K. Ishikawa, M. Sekine, M. Hiramatsu and M. Hori, Carbon, 2014, 68, 380.

[4] P. Slobodian, U. Cvelbar, P. Riha, R. Olejnik, J. Matyas, G. Filipič, H. Watanabe, S. Tajima, H. Kondo, M. Sekine and M. Hori, RCS Advances, 2015, 5, 90515-90520.
Low Temperature Electroless Deposition of Hard Magnetic Alloys for the Metallization of Additive Manufactured Functional Microstructures
Authors: Bernasconi Roberto , Credi Caterina , Levi Marinella , Magagnin Luca
Published: February 2020

In the last few decades additive manufacturing is finding applications in the field of microdevices production. Techniques like sterolithography (SLA), two photons lithography (TPL) and others [1] have the potential to reach the micrometric scale required for the realization of devices like polymeric based microelectromechanical systems (MEMS) or magnetically actuated microdevices. The most precise and versatile additive technologies however use polymers as materials. For this reason a fundamental step of the manufacturing process is the application of a metallic layer to provide conductivity, essential for MEMS, or to make sensitive the device to the presence of a magnetic field.

Many different metallization methods can be applied, but one of the most attractive in terms of cost and flexibility is electroless deposition [2]. The use of this all-wet technique introduce however some major issues when plating on the resins usually employed in SLA or TPL. The main problem is in particular related to the temperatures typical of some electroless baths, which makes them incompatible with polymers that in some cases present reversible transition temperatures as low as 40 °C. To successfully metallize SLA and TPL resins a great attention must be devoted to the choice and optimization of compatible electroless processes.

Between the possible metallic layers that can be applied in relation to the type of microstructure produced, hard magnetic alloys are of great interest. Such materials, and in particular their ability to retain magnetization, can be used to actuate or manipulate different classes of devices. Examples may include magnetically actuated microswitches, sensors or others [3].

In the present work two processes to deposit hard magnetic CoNiP, operating at two different temperatures, are presented and applied to the plating of microsized functional structures. The main advantages or disadvantages of using one temperature with respect to the other are discussed as a function of the target application. Some general problems related to the plating of stereolithography printed small structures are analyzed as well. These include difficulties coming from the chemical and physical properties of the resins, from the activation step or from the solution itself.

[1] M. Vaezi, H. Seitz, S. Yang; Int. J. Adv. Manuf . Technol. (2013) 67, 1721–1754

[2] Y. Yan, A. A. Bettiol, Photonics Global Conference (PGC), 2010, pp. 1 – 4

[3] S. Kim et al.; Adv. Mater. 2013, DOI: 10.1002/adma.201301484
Comparative Study of Electroless Platinum Deposition Using Multivalent Metal Ions or Hydrazine As Reducing Agents
Authors: Norkus Eugenijus , Stankeviciene Ina , Jagminiene Aldona , Tamasauskaite-Tamasiunaite Loreta , Naujokaitis Arnas , Buzas Vytenis , Maciulis Laurynas , Tumonis Liudas
Published: February 2020

Two new type electroless plating processes for deposition of continuous platinum layer are proposed and compared with known process of electroless platinum daeposition using hydrazine as reducing agent.

In this study investigation of the kinetics of electroless Pt deposition, using reducing agents such as Co(II)/Co(III) and Ti(III)/Ti(IV) redox systems, is presented. The Pt layers were deposited on the copper or nickel surfaces. The morphology of Pt layers deposited using different reducing agents was investigated by means of Field Emission Scanning Electron Microscopy (FESEM). Kinetics of deposition rate of Pt was investigated by means of the Electrochemical Quartz Crystal Microgravimetry (EQCM).

It was found that the deaeration of the electroless Pt plating solutions with argon, using Co(II)/Co(III) or Ti(III)/Ti(IV) redox systems as reducing agents, results in higher deposition rates of Pt. When using Co(II)/Co(III) redox system as a reducing agent, the rate of electroless deposition of Pt is ca. 0.3 µg cm-2 min-1 when using Ar-deaerated plating solution, whereas the one in non-deaerated plating solution is significantly lower, e.g. 0.02 µg cm-2 min-1. When, using the Ti(III)/Ti(IV) redox system as reducing agent, the Pt deposition rate in Ar-deaerated plating solution is higher compared with that using CoII)/Co(III) redox couple.

It should be noted that the obtained Pt layers deposited on the surface of Cu using Co(II)/Co(III) or Ti(III)/Ti(IV) redox pairs as reducing agents are continuous and compact.

The kinetic data of the mentioned reactions is discussed and compared with that obtained using hydrazine as reducing agent.

 

Acknowledgment

This research was funded by a Grant (No. TEC-06/2015) from the Research Council of Lithuania.
Superconformal Bottom-up Nickel Deposition in High Aspect Ratio through Silicon Vias
Authors: Josell Daniel , Moffat Thomas P.
Published: February 2020

This work demonstrates void-free nickel filling of 56 μm tall, annular Through Silicon Vias (TSVs) using a mechanism that couples suppression breakdown and surface topography to achieve controlled superconformal, void-free deposition. The chemistry, a Watts electrolyte containing a dilute suppressing additive, and processes are fully detailed. The impact of deposition potential and additive concentration on the filling of the patterned features is presented. Voltammetric measurements on planar substrates, including the impact of rotation rate and suppressor concentration on the rate of metal deposition and potential of suppression breakdown, are used to quantify the interplay between metal deposition and suppressor adsorption. The derived kinetics are then used to quantitatively predict the observed bottom-up filling in the TSVs using the S-shaped negative differential resistance (S-NDR) mechanism for superconformal deposition; the predictions capture the experimental observations. This work extends understanding and application of the additive-derived S-NDR mechanism developed with non-ferrous metals.

Figure 1
(Invited) A Single-Molecule Spin-Based Transistor
Authors: Schwarzacher W. , Brooke Richard , Szumski Doug , Nichols Richard , Mao Bing-Wei , Jin Chengjun , Thygesen Kristian
Published: February 2020

Single molecule devices are of great interest for what they reveal about fundamental aspects of electron transport and metal-molecule interactions. They represent the ultimate level of miniaturization in molecular electronics and are also of potential interest in sensor applications. We have used an electrochemical approach to realize a single molecule transistor based on 4,4′-bipyridine contacted by Ni. The top and bottom Ni contacts are an insulated Ni STM tip and an electrodeposited Ni film respectively, which are maintained free of oxide by being held in an aqueous electrolyte under potential control. The 4,4′-bipyridine molecules are initially present in the electrolyte and contacted using the STM break junction method. From numerous repeated experiments we build up a histogram of the measured conductance. This conductance depends strongly on the potential of tip and substrate relative to the reference electrode. This is a manifestation of electrostatic gating and shows that the device functions as a transistor. Remarkably, it shows a significantly higher gain than a similar transistor with Au electrodes. Calculations show that the current in the Ni-4,4′-bipyridine-Ni transistor is highly spin-polarized and therefore the device represents a true spin-based single molecule transistor.
A Novel Approach to Coal Processing - Electrochemical Solutions to Pollution Reduction and Material Synthesis
Authors: Yazdani Aliakbar , Botte Gerardine G , Vijapur Santosh H. , Wang Dan , Wang Yuxuan , Sheets Ben
Published: February 2020

Several scientific research have shown that the coal industry is responsible for a large array of pollution including small particle pollution near populated areas, toxic heavy metals and acid rains1. In 2011, EPA estimated that power plants are responsible for half of the mercury air pollutant in the U.S.2 These environmental concerns garnered the interest of both the general public and governments to find new ways to effectively reduce the pollution related to coal power plants. Furthermore, the current worldwide electricity generation is heavily reliant on coal comprising 41.3% accentuating the need for clean coal energy3.

For decades coal has been seen as a mere inexpensive fuel for generating energy in power plants. However, a closer look at coal reveals that coal is a heterogeneous and complex mixture of hydrocarbons, rich with minerals4. It has been reported that electrolyzing a slurry of fine coal particles in acidic media can produce hydrogen, consuming less energy than water-electrolysis5. The hydrogen produced by this method is pure enough to be used directly in a commercially available hydrogen fuel-cell.

Our research group have successfully electrolyzed coal to synthesize graphene by chemical vapor deposition method (CVD)6. Extensive optimization and control of process parameters was required to produce the graphene structure. The findings from the graphene synthesis process motivated the development of a comprehensive process to generate clean energy and produce high value materials from inexpensive coal.

The main advantages of the new process proposed in this study to process coal via electrochemical methods are (i) easy adaptation to the existing infrastructure of the coal industry to facilitate quicker and low-cost integration of the new process, (ii) decreasing the sulfur content of coal after each step to reduce pollution, and (iii) retrieving the metallic content leached from coal to the slurry to avoid toxic and heavy metals such as mercury poisoning of the air and also generate revenue to reduce operating cost.

Figure 1 represents a brief comparison between the current coal process and the new coal process proposed in this study. Various optimizations in every step of this coal process such as increasing hydrogen generation during electrolysis, decreasing energy consumption during pyrolysis and CVD, and electrochemical-recovery of minerals will be done with the focus on the process economy.

 

References

1. https://www3.epa.gov/radtown/docs/coal-fired-power-plants.pdf.

2. O. of A. and R. US EPA, https://www3.epa.gov/mats/.

3. http://www.iea.org/publications/freepublications/publication/KeyWorld_Statistics_2015.pdf.

4. Y. De Abreu, P. Patil, A. I. Marquez, and G. G. Botte, Fuel, 86, 573–584 (2007).

5. X. Jin and G. G. Botte, J. Power Sources, 171, 826–834 (2007).

6. S. H. Vijapur, D. Wang, and G. G. Botte, ECS Solid State Lett., 2, M45–M47 (2013).

Figure 1
Plasma-Enhanced Atomic Layer Deposition of Iron and Titanium Phosphates as Electrode Materials for 3D-Structured Lithium-Ion Microbatteries
Authors: Dobbelaere Thomas , Mattelaer Felix , Dendooven Jolien , Vereecken Philippe M. , Detavernier Christophe
Published: February 2020

Iron phosphates are widely used as polyanion-based positive electrode materials for lithium-ion batteries. In light of the considerable academic and industrial interest in the development of solid-state 3D-structured thin-film lithium-ion batteries, where the conformal deposition of very thin and pinhole-free electrode films on complex structures is an essential requirement, we have developed a plasma-enhanced ALD process to deposit amorphous iron phosphate at an unusually high growth rate of 1.1 nm/cycle.

Our deposition process is based on alternating exposures to trimethyl phosphate (TMP, Me3PO4) plasma, O2 plasma, and tert-Butylferrocene (TBF) vapor. The main novelty of the process lies in the use of a TMP plasma as the phosphorus source, according to a mechanism which we recently reported for the deposition of aluminum phosphate (Dobbelaere et al., Chem. Mater. 2014, 26, 6863−6871).

Firstly, we performed a detailed characterization of the deposition process of iron phosphate, including in-situ growth monitoring by spectroscopic ellipsometry and an investigation of temperature and pulse time dependency. Linear growth was observed without nucleation delay, proceeding optimally at 300°C. Saturation behavior could be demonstrated for all exposure steps, confirming a PE-ALD process.

Secondly, we studied the properties of the deposited films. The as-deposited amorphous films had a density of 3.1 g/cm3 and ERD analysis revealed an empirical stoichiometry of FeP1.5O4.7 with 0.9% hydrogen and no detectable carbon residue (fig. 1a). Post-deposition annealing in air resulted in the formation of trigonal FePO4, while the same anneal in helium resulted in the formation of elemental phosphorus.

Finally, we investigated the electrochemical behavior of the as-deposited iron phosphate in lithium-ion test cells. Cyclic voltammetry measurements showed lithiation and delithiation around 3V vs. Li/Li+, albeit reaching only 8% of the theoretical capacity. However, by reduction below 0.5V and subsequent oxidation back to 3V, we observed a drastic capacity increase to 60% of the theoretical capacity, resulting in an active 3V cathode material. Long-term charge/discharge cycling of a 33 nm planar film revealed that the capacity decreases over the first 10 cycles, and then stabilizes to 0.7 μAh/cm2. On a 3D micropillar substrate, the capacity increased from 7 μAh/cm2 to 22 μAh/cm2 over the first 150 cycles, and then remained constant at 22 μAh/cm2. Rate testing (fig. 1b) showed that both electrodes can be used at high C-rates, proving that the capacity is greatly enhanced by 3D structuring without sacrificing kinetics.

Figure 1: (a) depth profile of a 55 nm iron phosphate film on a silicon substrate; (b) comparison of charge/discharge capacity and rate capability between planar and 3D-structured electrodes.

Figure 1
Effects of SiO2 and TiO2 Combination Coating on TiO2 Nanoparticle Electrodes in Dye Sensitized Solar Cells
Authors: Kanomata Kensaku , Kato Yuki , Imai Takahiro , Miura Masanori , Ahmmad Bashir , Kubota Shigeru , Hirose Fumihiko
Published: February 2020

Dye sensitized solar cells (DSCs) have attracted much attention since the DSCs have cost advantages compared with the conventional Si solar cells. To achieve the high power conversion efficiency in the DSC, it is necessary to enhance the dye adsorption on the TiO2 nanoparticles. To achieve the high-density adsorption, we examined the TiO2 coating on the TiO2 nanoparticles since it might play a role for over-coating on naturally contaminated impurities on the nanoparticle surface. In addition, to obtain high power conversion efficiency in the DSCs, it is necessary to prevent carrier recombination between the electrolyte and TiO2 nanoparticle electrode. It is assumed that the recombination can be prevented by an energetic barrier of SiO2 between TiO2 / electrolyte. To deposit TiO2 on the nanoparticle, we used a plasma enhanced atomic layer deposition (ALD). The precursor was tetrakis(dimethylamino) titanium (TDMAT). The oxidizing agent was plasma-excited humidified argon. The growth per cycle of TiO2 is estimated as 0.15 nm/cycle. To deposit SiO2 on the TiO2 coated nanoparticles, we used the same ALD system. The precursor was tris(dimethylamino)silane (TDMAS). The oxidizing agent was the same oxidizer as that in case of TiO2. The growth per cycle of SiO2 is estimated as 0.066 nm/cycle. In this experiment, we used N719 as the sensitizing dye. We show J-V characteristics of the DSCs with the SiO2 and TiO2 combination coating in figure 1. The short circuit current density is improved from 10.04 mA/cm2 to 13.16 mA/cm2 while the open circuit voltage remains unchanged around 0.74 V. With the 10 cycle ALD of TiO2 and one cycle ALD of SiO2, the power conversion efficiency is improved from 5.41 % to 7.03 %. We consider that the combination coating prevents the carrier recombination between the electrolyte and ALD-TiO2 coated nanoparticle electrode.

Acknowledgement; This work was partly supported by JST-CREST, JSPS KAKENHI Grant Numbers 15H03536 and 15K13299.

Figure 1
Synthesis of Cerium-Oxide Coated Platinum Core-Shell Structure Catalysts with Enhanced Stability and Activity via Atomic Layer Deposition
Authors: Cao Kun , Shi Lu , Cai Jiaming , Shan Bin , Chen Rong
Published: February 2020

Platinum nanoparticles (NPs) play an important role in the catalytic applications such as conversion of automotive exhaust, fuel cells, nano sensing and so on. For many of catalytic applications, agglomeration of Pt NPs is undesired because the coalescence results in a decrease of surface active sites.1 Many approaches have been explored to prevent agglomeration, the formation of core shell structures to encapsulate the noble metal nanoparticles seems to be a viable way.2,3

Herein we report the utilization of active oxide layers to encapsulate Pt NPs through atomic layer deposition. Besides the outstanding sintering resistance by physical anchoring, the active oxide decorated composite catalysts have additional metal-oxide interfaces that may further enhance the catalytic activity. HRTEM characterizations and DFT simulations have shown that oxide layers initially preferred to deposit on Pt (111) to form an incontinuous coating layer. The Pt-oxides model catalysts were prepared on planar Al2O3 supports to obtain a molecular level understanding of the catalytic process. It is found that Pt nanoparticles with all kinds of oxide coating layers have demonstrated not only the good sintering resistance under atmosphere condition, but also the lower CO oxidation conversion temperature than bare Pt nanoparticles.

References:

K. Hayashi, T. Horiuchi, K. Suzuki, Catalysis Letters, 78, 2002

K. Cao, B. Huang, Y.H. Zhang et al. ECS Transactions, 64(9), 159-166, 2014

J. Lu, B. Liu, J. P. Greeley, Chemistry of Materials, 24, 2047-2055, 2012
High Performance Asymmetric V2O5-SnO2 Nanopore Battery By ALD
Authors: Liu Chanyuan , Lee Sang Bok , Rubloff Gary W
Published: February 2020

An array of nanobatteries, each self-aligned and fully confined within a single nanopore, provides an effective testbed for the rate performance and cyclability limits of nanostructured storage devices. With atomic layer deposition (ALD), we have previously synthesized and evaluated such structures in a symmetric configuration, comprised of nanotubular V2O5 electrodes as both anode and cathode and electrolyte confined within anodic aluminum oxide (AAO) nanopores. Each nanopore battery has ultra-small volume (~1fL) and shows superior performance when tested as massively parallel device (~2billion/cm2).
[i]
However, an asymmetric full cell configuration with a low voltage anode material has not been explored yet.

Here we report an asymmetric full cell nanopore battery, comprised of V2O5 as cathode and prelithiated SnO2 as anode, with integrated nanotubular Pt current collectors underneath each nanotubular storage electrode. Also enabled by ALD, this coaxial nanotube full cell is fully confined within the high aspect ratio nanopore (150nm in diameter, 50um in length). By controlling the amount of lithium ion prelithiated into SnO2 anode, we can tune full cell output voltage in the range of 0.3V and 3V. This asymmetric nanopore battery array displays exceptional rate performance and cyclability. When cycled between 1V and 3V, it has capacity retention of approximately 73% at 200C rate compared to 1C, with only 2% capacity loss after more than 500 charge/discharge cycles. With increased full cell output potential, the asymmetric V2O5-SnO2 nanopore battery shows significantly improved energy and power density. This configuration presents a more realistic test - through its asymmetric (vs symmetric) configuration – of performance and cyclability in nanoconfined environment.

[i] Liu, C.; Gillette, E. I.; Chen, X.; Pearse, A. J.; Kozen, A. C.; Schroeder, M. A.; Gregorczyk, K. E.; Lee, S. B.; Rubloff, G. W., An all-in-one nanopore battery array. Nature Nanotechnology
2014,
9 (12), 1031-1039.
Core-Shelled Low-Oxidation State Oxides@Reduced Graphene Oxides Cubes Via Pressurized Reduction for Highly Stable Lithium Ion Storage
Authors: Li Ping , Park Jong Hyeok
Published: February 2020

Metal oxides have been regarded as promising next-generation anode materials for rechargeable lithium ion batteries; however, their poor stability, which is caused by large volume changes during repeated lithiation/delithiation, remains a challenge. Here, conformally encapsulated low-oxidation state oxide cubes with reduced graphene oxide (RGO) obtained via a new pressurized reduction consisting of external mechanical compression and internal thermokinetic reduction from highly porous metal oxides/RGO aerogel (RGOA) are reported. Using single crystalline (SC) cobalt oxides and iron oxide cubes as model systems, the SC-Co3O4 or Fe2O3 cube/RGOA are pressurized into compacted xerogel along with a uniform thermokinetic reduction, which result in topotactic transformation to core-shelled CoO/RGO or Fe3O4@RGO cubes. The SC-CoO and SC-Fe3O4 cubes isolated perfectly in the RGO shells have dramatically improved their cycling stabilities for lithium ion storage to hundreds of times.
Synthesis and Electrode Performance of Li3NbO4 - LiVO2 Binary System for Li Batteries
Authors: Yabuuchi Naoaki , Nakajima Mizuki
Published: February 2020

Rechargeable lithium batteries are used for electric vehicles, and the demand for high-energy and long-cycle-life positive electrodes is growing. Recently, Li1.3Nb0.3V0.4O2 with a cation-disordered rocksalt structure has been reported as a positive electrode material, which delivers high reversible capacity of >200 mAh g-1 with V3+/V5+ two-electron redox.[1] However, for Li1.3Nb0.3V0.4O2, 0.5 mole of Li+ remains in the crystal lattice after fully charge, and therefore further increase in the energy density is anticipated through the optimization of chemical compositions. In this study, we systematically examine crystal structure and electrochemical properties of x Li3NbO4 – (1 – x) LiVO2 binary system as positive electrode materials for rechargeable lithium batteries.

Li-Nb-V-O samples were prepared by a solid-state reaction from stoichiometric amounts of Li2CO3, V2O3 and Nb2O5. The mixtures of precursors were calcined at 950 oC for 12 h in inert atmosphere. Thus prepared samples were mixed with acetylene black by mechanical ball-milling. The samples were characterized by XRD and SEM. Electrochemical properties as positive electrode materials were examined using two-electrode electrochemical cells.

X-ray diffraction patterns of the binary system of x Li3NbO4 – (1 – x) LiVO2 with different compositions are shown in Figure 1 (a). Li1.3Nb0.3V0.4O2 (x = 0.43) crystallizes into cation-disordered rocksalt phase whereas partially cation-ordered rocksalt phase is found for Li1.25Nb0.25V0.5O2 (x = 0.33) and Li1.2Nb0.2V0.6O2 (x = 0.25). Electrochemical properties of the samples are also shown in Figure 1 (b). The cells were galvanostatically cycled at a rate of 10 mA g-1 in the voltage range of 1.5 – 4.8 V at room temperature. Among three samples (x = 0.25, 0.33, and 0.43), the highest reversible capacity of >250 mAh g-1 is obtained for Li1.25Nb0.25V0.5O2 (x = 0.33). Moreover, electrode performance is further increased by heat treatment of the samples.

From these results, we will discuss the possibility of x Li3NbO4 – (1 – x) LiVO2 binary system with V3+/V5+ two-electron redox as high-capacity and long-cycle-life positive electrode materials for rechargeable lithium batteries.

(1) N. Yabuuchi et al., Chem. Commun.,
52, 2051 (2016).

Figure 1
Co3O4 quantum Dots Uniformly Confined into Sheet-like SWCNT Matrix for Highly Reversible Lithium Storage
Authors: Xie Zhiqiang , Jiang Chengmin , Martí Angel A , Wang Ying
Published: February 2020

To effectively address fundamental problems in using transition metal oxides as high-performance anode materials for lithium ion batteries (LIBs), we prepare Co3O4 QDs@SWCNT heterostructures composed of well-dispersed ultrafine cobalt oxide (Co3O4) encapsulated within flexible sheet-like single-walled carbon nanotubes (SWCNTs) matrix for the first time, through a facile and controllable method via evaporation-induced self-assembly (EISA) of single-walled carbon nanotubides (SWCNTDs). By varying the loading amount of Co3O4 content in the heterostructure, the optimized sample containing Co3O4 QDs as high as 83.3 wt% exhibits a very high specific capacity of 1198 mAh g-1 after 50 cycles at a specific current of 100 mA g-1 and a superior rate capability with high capacities of 1080, 944, 833, 648 and 423 mAh g-1 at specific currents of 100, 500, 1000, 2000 and 5000 mA g-1, respectively. When the specific current returns to 100 mA g-1, the optimized Co3O4 QDs@SWCNT heterostructure still delivers a very high capacity of ~1300 mAh g-1 after 40 extended cycles, demonstrating outstanding electrochemical reversibility. Moreover, the optimal Co3O4 QDs@SWCNT heterostructure demonstrates superior prolonged cycling stability for over 200 and 600 cycles at extremely high specific currents of 1000 and 2000 mA g-1, respectively. Such superior electrochemical performances are ascribed to the synergic effect of ultrafine Co3O4 nanoparticles and SWCNTs in the heterostructure, in which the robust SWCNTs not only offer excellent strain accommodation of the encapsulated Co3O4upon long-term cycling, but also significantly enhance overall electrical conductivity and mechanical stability of the electrodes. The facile and effective strategy in this work can be extended to design various nanoparticles@SWCNTs heterostructures for potential applications in LIBs, supercapacitors, catalysts, sensors and other fields.

Keywords: Co3O4 QDs; Sheet-like SWCNTs; Evaporation-induced self-assembly; Rate capability; Prolonged cycling stability; Lithium ion battery
In-Situ Boron Doped SiGe Epitaxy Optimization for FinFET Source/Drain
Authors: Qi Yi , Peng Jianwei , Lo Hsien-Ching , Holt Judson Robert , Willemann Michael , Gaire Churamani , Evans Sarah , Flanagan Patrick , Yu Hong , Hu Owen , Kennett Michael
Published: February 2020

In-situ Boron doped embedded SiGe epitaxy has been widely used for CMOS source/drain in advanced technology nodes, from its introduction in planar devices to its more recent application in FinFETs. Compared to planar technology, FinFETs have the benefit of improved short channel effect, which allows for significantly higher in-situ doping level for lower contact resistance.

This work explores the source/drain expitaxy design differences between planar and FinFET transistors, and how the in-situ doped epitaxy process can be optimized to address the call for a higher doping level in the FinFET source/drain. In particular, we observe a competing relationship between Germanium and Boron incorporation -- increasing Ge incorporation generally lowers boron doping, and increased boron incorporation generally lowers Ge. However, our work shows that the limit of Boron doping can be boosted by increasing Ge percentage, and furthermore we propose a Si-Ge-B phase diagram based on this experimental data. Outside of the soluble area of the phase diagram defective epitaxy is observed, featuring Boron-rich incoherent phase or Boron segregation. Finally, we present device data that show the performance benefit when Ge% and Boron is optimized according to the phase diagram, characterized by lower Ron and higher drive current.
Annihilation of Threading Dislocations in Strain-Relaxed Si1-XGex Layer By Hydrogen Ion Implantation
Authors: Park Jun-Seong , Kim Il-Hwan , Shin Hyeon-Ju , Shim Tae-Hun , Lee Gon-Sub , Park Jea-Gun
Published: February 2020

According to the international technology roadmap for semiconductor (ITRS), the development of MOSFETs based on the strain technology is necessary for the next generation technology beyond 10-nm C-MOSFETs. By being applied the strain in the channel of MOSFET, the electron mobility can be enhanced results in the higher current in MOS channel at the fixed gate voltage and oxide thickness. However, due to the lattice mismatch of 4.2 % between Si and Ge, many threading dislocations are generated during the epitaxial growth, resulted in increasing the leakage current of the C-MOSFETs. Currently, the threading dislocation density of 3-µm-thick X-at% (>30-at%) graded Si1-xGex layer is higher than 105 cm-2, which is too high level to be applied in mass production because of degrading the productivity and the performance of the C-MOSFETs.

 In this study, for that reason, to reduce threading dislocations in the strain-relaxed Si1-xGex layer, we investigated how the hydrogen ion implantation annihilated the threading dislocations in strain-relaxed Si1-xGex layer/Si (100) substrate. First, a relaxed Si1-xGex layer was grown on a Si (100) substrate by epitaxial growth. Second, hydrogen ions were implanted onto the interface between the strain-relaxed Si1-xGex layer and the Si substrate. After ion implantation, the sample was annealed at 800oC for 30 min in a nitrogen ambient. For the case of hydrogen ion implantation with a dose of 5ⅹ1015 cm-2, it was confirmed that the cross-hatch pattern density and the surface roughness was decreased and threading dislocations near the interface were not observed in hydrogen ion-implanted Si1-xGex/Si wafer as shown in Fig. 1. In addition, as shown in Fig. 2, by using in-situ real-time high-resolution TEM, it was confirmed that a threading dislocation in hydrogen ion-implanted Si0.7Ge0.3 layer/Si substrate was annihilated with hydrogen-related defect while the TEM specimen was being annealed at 600oC for 30 min in the heating holder.

 Therefore, we present the formation mechanism of threading dislocations in a strain-relaxed Si1-xGex layer/Si (100) substrate and the annihilation mechanism of how the threading dislocations are annihilated by hydrogen ion implantation.

* This work was financially supported by the Brain Korea 21 Plus Program in 2016 and SiWEDS (Silicon Wafer Engineering and Defect Science).

Reference

[1] J. G. Park et al., Mat. Sci. Eng. B
134 142-153 (2006)

[2] S. Takagi, Strained-Si CMOS Technology in Advanced Gate Stacks for High-Mobility Semiconductors, Springer Berlin Heidelberg 1 (2007)

Figure 1
Conductive Semiconductor Interfaces Fabricated by Room Temperature Covalent Wafer Bonding
Authors: Flötgen Christoph , Razek Nasser , Dragoi Viorel , Wimplinger Markus
Published: February 2020

Low temperature fusion wafer bonding technology is nowadays fully adopted by semiconductor industry as it is used in various process flows (e.g. for bonding CMOS wafers for fabrication of backside illuminated CMOS image sensors). The development of the low temperature fusion wafer bonding processes (maximum 400°C) constituted a breakthrough for the technology as such process allows not only for maintaining a high post-bonding precise wafer-to-wafer alignment (current performance in the 50 – 100 nm alignment accuracy) but also for decreasing the stress levels developed during thermal annealing of wafers with different thermal expansion coefficients. Some new categories of applications were triggering new developments in fusion bonding, with two main targets in terms of applications: room temperature covalent bonding (no thermal annealing at all) and fabrication of oxide-free, conductive bonded interfaces. The development of a new direct bonding technology based on EVG580®ComBond® allowed in the first step for fabricating room temperature covalent bonds with bond strength comparable to the bulk fracture strength of substrates (first results for Si-Si bonding were reported elsewhere). However, after reaching the first target of room temperature bonding, the technology was further developed in order to allow for fabrication of bonded interfaces with good electrical functionality. First, equipment hardware had to be further optimized in order to reach compatibility with front end of line (FEOL) processes (critical metal ions levels <1010 atoms/cm2). Experimental data will be presented to illustrate the development work in this direction and proving CMOS compatibility. On the process side, the early process work was revealing that an amorphous layer was developing at substrate surface after the specific surface preparation using the ComBond® process. As the presence of the thin amorphous layer on the surfaces impacts on the electrical performance of the bonded interface, the possibility to control the thickness of this layer was subject of an optimization study. This work reports process results on amorphous layer thickness reduction and presents very promising experimental data on electrical characterization of various bonded materials (Si-Si, Si-GaAs).
Optical Isolator with Si Guiding Layer Fabricated by Photosensitive Adhesive Bonding
Authors: Yokoi Hideki , Choowitsakunlert Salinee , Kobayashi Kouya , Takagiwa Kenji
Published: February 2020

INTRODUCTION

  In optical communication systems, an optical isolator is indispensable in protecting active photonic devices from unwanted reflected light. An optical isolator with a Si guiding layer is a significant device for silicon photonic integrated circuits. In this paper, the authors report on an optical isolator with the Si guiding layer fabricated by photosensitive adhesive bonding.

DEVICE STRUCTURE

  Figure 1 shows an optical isolator with a Si guiding layer employing a nonreciprocal guided-radiation mode conversion [1]. A magnetic garnet cladding layer is bonded with the Si guiding layer by photosensitive adhesives. A cerium-substituted yttrium iron garnet (Ce:YIG) is used as the magnetic-garnet cladding layer [2]. The optical isolator is comprised of a straight rib waveguide with a Ce:YIG/Si/SiO2 structure. An external magnetic field is applied to the magneto-optic waveguide in film plane. TM modes travelling in the magneto-optic waveguide have distinct propagation constants for the forward- and the backward-travelling waves owing to a nonreciprocal phase shift. By adjusting waveguide parameters, the following relationship is satisfied:

                    β

b

y
  < β

c

x
<  β

f

y
           (1)

where β

f

y
 and β

b

y
denote the propagation constants of the forward- and the backward-traveling TM modes and β

c

x
  denotes the cutoff of TE modes. Only the backward-traveling TM modes can couple to the TE radiation modes so that the device acts as a TM-mode optical isolator.

  The optical isolator employing the nonreciprocal guided-radiation mode conversion was designed at 1.55 μm. The nonreciprocal phase shifts in the magneto-optic waveguides with various gap widths were calculated. It was confirmed that the nonreciprocal phase shift was reduced with increasing the gap width. The relationship of the waveguide parameters that satisfies equation (1) was investigated. Once the rib height was set, the range of the rib width for the isolator operation, which means that the propagation constants satisfy the relationship denoted by expression (1), was given. It was found that smaller gap width was desired for large tolerance of the waveguide parameters.

ACKNOWLEDGMENT

  This work was partially supported by the SIT Research Center for Green Innovation. 

REFERENCES

1. H. Yokoi, K. Sasaki and T. Aiba, Jpn. J. Appl. Phys., 48, 062202 (2009).

2. T. Shintaku, T. Uno and M. Kobayashi, J. Appl .Phys., 74, 4877 (1993).

Figure 1
Decreased Surface Porosity and Roughness of InP for Epitaxially Grown Thin-Film Devices: A Path to Integration of High Performance Electronics
Authors: Gervasoni Michael , Machness Ariella , Goorsky Mark
Published: February 2020

Devices based on III-V semiconductors have generated widespread interest due to their superior performance over conventional semiconductors such as silicon. However, III-Vs are inhibited from mass commercialization because of high costs. Thus, there is a motivation to develop affordable, high-quality thin film III-V devices, which has been realized through exfoliation techniques. In this work, a porous InP structure with optimal morphology was fabricated for exfoliation. A relationship between surface porosity and current density was determined and utilized for obtaining a desirable porous structure. Surface porosities as low as 2% were achieved, as determined by scanning electron microscopy (SEM). Moreover, surface roughness measured by atomic force microscopy (AFM) found that reducing the porosity lowered the surface roughness. Thus, porous layer with surface roughnesses approaching that of a InP polished surface were demonstrated. The porosities and surface roughness obtained are lower than previously reported and more ideal for growing a low-defect epitaxial film. By growing higher quality epitaxial films on a reusable seed wafer, high performance and cost effective III-V devices are made possible.
Transfer of Ultra-Thin Semi-Conductor Films onto Flexible Substrates
Authors: Montméat Pierre , De Nigris Brandolisi Isadora , Tardif Samuel , Enot Thierry , Enyedi Gregory , Kachtouli Riadh , Besson Pascal , Rieutord François , Fournel Frank
Published: February 2020

Applying tensile strain on an undirect band gap semiconductor crystal is a very promising way to tune it into a direct band gap 
[1]
,
[2]
. This basic feature can be an outstanding progress for the use of classical semiconductor as silicon or germanium in interesting optoelectronic applications
[3]
. One way to apply a tensile strain is to transfer an ultra-thin of semiconductor onto a flexible substrate
[4]
(erg: an organic polymer). The goal of this paper is to propose a simple way to obtain an ultra-thin silicon film (<200 nm) onto an expendable polymer. It consists in transferring an Unibond™ SOI silicon thin film onto a classical tape maintain by a dicing frame. This process is mainly based on classical temporary bonding process.

As shown on figure, a first process is carried out onto 200 mm wafer with a SOI silicon film of 200nm and a buried oxide box of 400nm. No default is observed on the full stack after the grinding and etching steps used to remove the SOI backside substrate. No SiO2trace is also observed after the last dioxide etching. The thin silicon film is then characterized and no crack is observed. The stack is then laminated onto a frame with a Furukawa SP-537T-230 adhesive tape. The demounting of the carrier is easy and no default appears on the silicon film. The last process consists in removing the glue from the silicon. We obtain a 200 nm silicon film bonded onto the tape. Nevertheless, this glue removal leads to the appearance of some cracks ono the silicon thin film. A second process will then be presented in order to avoid the last glue removal steps and improving the final thin film quality. XRR characterizations of the transfered thin film will be presented as well as potential amount of tensile stress achievable with this unique structure.

[1] Ju Li et al., MRS Bulletin, 39, pp 108-114, 2014

[2] Feng Zhang et al., Phys. Rev. Lett. 102, 2009

[3] Diode Lasers and Photonic Integrated Circuits, Second Edition, 2012 John Wiley & Sons, chap 4

[4]& Salvatore Giovanni A.et al., ACS NANO Volume 7, Issue: 10, P8809-8815, 2013

Figure 1
Bond Strength of 3D-stacked Monocrystalline Silicon X-ray Mirrors
Authors: Girou David , Landgraf Boris , Gunther Ramses , Collon Max
Published: February 2020

In view of high-performance light-weight X-ray optics, we developed a unique technology and assembly tool to stack structured and bend monocrystalline silicon plates resulting in a matrix-like pore structure, the so-called Silicon Pore Optics (SPO). The fully automated assembly robot is specifically developed to stack SPO of various sizes and is a combination of standard semiconductor systems and newly developed tools. The complete system has a footprint of a few square meters only and is installed in a particle free environment. The robot selects a plate for stacking and inspects it for particles. The plate is then handed over to the actual stacking tool, which will elastically bend it into a cylindrical or conical shape. After two bend and structured silicon plates have been hydrophilically bonded to each other, the figure and interfacial particular contamination is investigated with a Fringe Reflection Technique (FRT) machine. The process of stacking is getting repeated by the assembly tool till the stack reaches a height of up to 45 plates forming a stiff self supporting structure.

In this presentation, we will give account of the production of SPO with different radii. We will mainly focus on our investigations of the bond strength of the directly bonded structured silicon mirror plates. The investigation of the mechanical strength of bonds of structured plates is of high importance as the bond strength is difficult to estimate in FE modeling, but is a critical point in the overall mechanical stability of the SPO. We performed tensile testing measurements to quantify the bond strength of two different types of samples, flat and curved direct bonded structuredmonocrystalline silicon plates. The failure modes found during this tests are either separation of the bond or failure of the structured silicon plates. Thereby, the tensile test results show clearly what failure mode it is. Furthermore, we post-annealed the samples at various temperatures and for different times in order to increase the bond strength and thus improve the stability of the stacks.