bluuebunny/crossref_metadata_2025 huggingface dataset:
Pt-Lanthanide Alloys for Oxygen Reduction: Relating Active Surface Phase and Catalytic Performance
Authors: Malacrida Paolo , Escudero-Escribano Maria , Verdaguer-Casdevall Arnau , Vej-Hansen Ulrik Grønbjerg , Rossmeisl Jan , Stephens Ifan E. L. , Chorkendorff Ib
Published: February 2020

The development of economically viable and efficient low temperature fuel cells requires a substantial improvement of the oxygen reduction reaction (ORR) catalysts at the cathode. Alloys of Pt and late transition metals have exhibited high activities, but typically suffer from a fast degradation due to dealloying [1-2]. Not only do polycrystalline alloys of Pt and a lanthanide metal (La, Ce, Gd) exhibit very high catalytic activity, but they should also be inherently more stable than alloys of Pt and late transition metals, due to their very negative heat of alloy formation [3-5]. In this work, sputter-cleaned Pt5La and Pt5Ce present more than a 3-fold activity enhancement compared to polycrystalline Pt with only minor losses after accelerated stability tests (Fig. A). The extensive combination of electrochemical and physical techniques, including Angle Resolved X-Ray Photoelectron Spectroscopy (AR-XPS) and Low Energy Electron Spectroscopy (LEIS) makes these polycrystalline samples excellent model systems towards the design of cathode catalysts. The active chemical phases, which are still largely debated, have been elucidated by AR-XPS (Fig. B). La and Ce oxides are formed on the surface of the alloy under air-exposure but they are readily removed by acid leaching during ORR activity testing. A ~3 monolayer thick Pt overlayer is formed and provides kinetic stability against further dealloying during cycling (Fig. C). Investigating the nanoscale properties of these overlayers is a fundamental step towards understanding their catalytic performance. The level of strain relative to pure Pt is responsible for the enhanced activity. It turns out that the thickness of the overlayer defines the level of strain relaxation and provides details about the dealloying mechanism.

[1] H. A. Gasteiger, et al. Appl. Catal. B
2005, 56, 9. [2] I. E. L. Stephens, et al. Energy Environ. Sci. 2012, 5, 6744. [3] M. Escudero-Escribano, et al. J. Am. Chem. Soc. 2012, 130, 16476. [4] P. Malacrida, et al. J. Mater. Chem. A
2014, 2, 4234. [5] S. J. Yoo, et al. Energy Environ.
Sci. 2012, 5, 7521.

Fig. (A) Kinetic current density measured at 0.9 V of Pt5Ce, Pt5La and Pt before and after a stability test consisting of 10 000 cycles between 0.6 and 1.0 V vs. RHE at 100 mV s−1. (B) Ce 3d XPS spectra of Pt5Ce after electrochemical measurements showing only metallic components. (C) AR-XPS depth profile of Pt5Ce after ORR testing (solid line) and after stability test (dashed line). In the inset, illustrative structure of acid leached Pt5Ce.
Coupling Chemo-Mechanical Oscillators
Authors: Parmananda Punit
Published: February 2020

The dynamics of a chemo-mechanical

Mercury Beating Heart (MBH) system is

analyzed experimentally.

It is observed that different

shapes of the mercury drop could be

obtained. The redox potential timeseries

for this MBH system, corresponding to these different

shapes were also recorded.

Subsequently, two and three such oscillators were coupled

and the resultant synchronization phenomena studied.
Invited: Non-Equilibrium Effects of Non-Equilibrium Plasmas: From Nanoscale Synthesis to Applications in Energy and Medicine
Authors: Ostrikov Kostya (Ken)
Published: February 2020

Several examples of the effects of non-equilibrium “extreme” conditions of low-temperature plasmas on the formation and processing of advanced nanomaterials and nanostructures [1,2] and also on the responses of living cells to the plasma exposure [3,4], are presented. The plasma-produced or functionalized nano-materials considered are aimed at next-generation energy, sensing, environmental and several other applications that are of critical importance to the sustainable future of humankind. Plasma-specific effects that lead to these interesting properties and superior performance in the envisaged applications are discussed.

This presentation explains why low-temperature plasmas represent a unique way of producing and arranging a variety of atomic, radical, cluster, etc. building units into a variety of nanoscale objects. It also discusses the effects of atmospheric-pressure plasma treatments on a variety of living cells and tissues and explores some relevant mechanisms that lead to the specific responses. The examples include effective apoptotic pathways of killing various cancer cells, inactivation of various microorganisms and biofilms, as well as agitation of stem cells to achieve selective differentiation.

The nanotechnology-related examples mostly include (but are not limited to) plasma-produced or functionalized nano-carbon materials that are aimed at next-generation in energy, sensing, environmental and several other applications that are of critical importance to the sustainable future of humankind. Plasma-specific effects that lead to these interesting properties and superior performance in the envisaged applications are examined and where possible are related to the non-equilibrium, to some extent “extreme” properties of the plasmas.

[1] K. Ostrikov, Rev. Mod. Phys. 77(2005) 489.

[2] K. Ostrikov, E. C. Neyts, M. Meyyappan, Advances in Physics 62(2013) 113.

[3] M. Ishaq, M. Evans, K. Ostrikov, Int. J. Cancer 134(2014) 1517.

[4] Z. Xiong, S. Zhao, X. Mao, X. Lu, G. He, G. Yang, M. Chen, M. Ishaq, K. Ostrikov, Stem Cell Research 12 (2014) 387.
The Role of Carbon Functionalities in the Incorporation of Pseudocapacitive Inorganic Phases for Improved Capacitance
Authors: Cuentas-Gallegos ANA Karina , Adan Marino , Brousse Thierry , Martinez-Casillas Diana Cristina , Mosqueda Hugo Armando
Published: February 2020

Supercapacitors based on carbon materials have shown high power densities compared to rechargeable batteries, but lower energy densities. The introduction of pseudocapacitive materials, such as conducting polymers and/or different inorganic phases, in different carbons have open the possibility to improve the intrinsic capacitance of the electrode materials, and by consequence the energy densities of the assembled devices. One of the main drawbacks of most inorganic materials is their low electric conductivity, which is somehow compensated when they are incorporated into a carbon matrix. Another strategy has been the introduction of certain functional groups in carbon to promote an intimate interaction with the inorganic compounds, resulting in improved electrochemical properties of the electrode materials for supercapacitors. In these sense, different carbon materials have been modified with different functional groups (-OH, -COOH, -CHO, NH2) to evaluate their effect with different inorganic phases, such as polyoxometalate (POM) or vanadyl phosphate (VOPO4). The resulting nanocomposite materials (C-POM, C-VOPO4) have been characterized by XRD, FTIR, N2 and CO2 isotherms, and most importantly in acidic or neutral aqueous electrolyte where their improved capacitance values have been calculated.
Hybrids of 2D-Nanomaterials for Supercapacitor/Battery Applications
Authors: Mendoza Sanchez Beatriz , Coelho Joao , O'Brien Sean , Pettersson Henrik , Nicolosi Valeria
Published: February 2020

Supercapacitors and batteries are energy storage systems, the former offering a high power density and a high degree of cyclability, and the latter being mainly a high energy density device. Batteries and supercapacitors store energy electrochemically by interaction of an electrode material and an electrolyte. The energy stored is proportional to the surface area of the electrochemically active material and therefore high surface area 2D-nanomaterials are suitable for this application. In this work, we present the manufacture of thin-film supercapacitor/battery electrodes using cost-effective and scalable methods: solvent-exfoliation followed by spray deposition. A variety of 2D-nanomaterials that can be grouped in two categories, carbon-based and metal oxides, were synthesized, characterized and evaluated. We have exploited the concept of hybridization to combine the properties of two 2D materials in a "hybrid" synthesized by a single step liquid-phase exfoliation method. First synthesized metal oxide-graphene hybrids showed an improved charge storage capacity. This work constitutes the proof-of-concept work for future investigation on rational design of functional 2D hybrid nanomaterials.
Nanostructured Multilayer Manganese Dioxide/Nickel/Copper Sulfite (MnO2/Ni/CuS) Composite Films for Electrochemical Applications
Authors: Pang Suh Cem , Awangku Metosen Awangku Nabil Syafig , Chin Suk Fun
Published: February 2020

Nanostructured multilayer manganese dioxide/nickel/copper sulfite (MnO2/Ni/CuS) composite films were successfully deposited on supporting polyethylene terephathalate (PET) substrate through the sequential deposition of CuS, Ni and MnO2 thin films by chemical bath deposition, electrodeposition, and horizontal submersion deposition techniques, respectively. Deposition of each thin-film layer was optimized through varying deposition parameters and conditions associated with specific deposition technique. Both CuS and Ni thin films were optimized for their electrical conductivity whereas MnO2 thin film was optimized for its microstructure and charge capacity. The electrochemical properties of nanostructured multilayer MnO2/Ni/CuS composite films were evaluated by cyclic voltammetry as electrode materials of electrochemical capacitor prototype in a dual planar device configuration. Cyclic voltammograms in mild Na2SO4 aqueous electrolyte exhibited a featureless and almost rectangular shape which was indicative of ideal capacitive behavior and high cycling reversibility for prolonged cycling up to 1,500 cycles. Nanostructured multilayer MnO2/Ni/CuS composite films on supporting polyethylene terephathalate (PET) substrate could potentially be utilized as electrode materials for the fabrication of high performance electrochemical capacitors.
Development of Li2FeSiO4/Activated Carbon Composited Cathodes for Li-Ion Capacitors
Authors: Li Chun-Lung , Chao Chung-Hsiang , Lee Ying-Hui , Lin Yu-Wei , Hwang Jenn-Yeu , Tsai Li-Duan , Fang Jason
Published: February 2020

The hybrid supercapacitors are electrochemical energy storage devices that combine the advantages of both Li-ion batteries and supercapacitors. The lithium ion capacitors (LICs), one of the hybrid capacitors under development, has a speciﬁc energy and energy density of around 30 Wh/kg and 20 Wh/L, respectively. These values are more than three times higher than the values of a conventional EDLC.They are expected to bridge the gap between Li-ion cells and supercapacitors and be used to power electric and hybrid vehicles. They can deliver high energy and power densities for short periods with long cycle lives, while operating over a wide range of temperatures with low maintenance costs.

The Li2FeSiO4 is attractive as it not only displays outstanding electrochemical behavior, but it is also the basis for the explosion of substituted derivatives with improved properties. However, Li2FeSiO4 has low electronic and ionic conductivity. Carbon coating is an efﬁcient way to enhance the charge transfer. In this study, carbon coating was carried out by mixing Li2FeSiO4 with a carbon source followed by calcination at high temperature and atmospheric conditions. The Li2FeSiO4/carbon composites are denominated as LFSC1, LFSC2 and LFSC3. The pristine capacities of Li2FeSiO4/carbon composites are measure at different C rate. The LFSC2 shows the best performance at each C rate. The LICs are fabricated with lithium ion battery type anode and LFSC/activated carbon cathode. The performances are measured by battery test equipment with CC-CV charge/CC discharge procedure. The charge/discharge plots show the traditional diagram of supercapacitor. This work is studying by some other approach to achieve high power performance.
Polyanilene-Coated Porous Carbon Nanofiber Electrodes for Supercapacitors
Authors: Kalra Vibha
Published: February 2020

We report the development of three-dimensional hybrid supercapacitor electrodes combining pseudocapacitive polyanilene and porous carbon nanofibers. The porous carbon nanofibers with specific surface area of >1500 m2/g were first fabricated via electrospinning of a blend of carbon precursor and sacrificial polymer followed by high temperature pyrolysis. The pyrolysis step converted the carbon precursor (polyacrylonitrile-PAN) to carbon and decomposed out the sacrificial polymer forming micro/mesopores within carbon nanofibers. Figure 1 shows the SEM images of porous carbon nanofibers fabricated using different PAN concentrations. Figure 2 shows the CV curves (in 1M H2SO4) of porous carbon nanofibers fabricated using 40 wt% PAN at various scan rates exhibiting ideal rectangular shape indicative of fast ion transport and high power handling capability. Polyanilene was conformally coated on porous carbon nanofiber substrates via electropolymerization of aniline monomer in 1 M H2SO4to develop device-ready freestanding hybrid electrodes. Electropolymerization was carried out in a three-electrode setup using the potentiodynamic method with Ag/AgCl as the reference electrode and platinum mesh as the counter electrode. Figure 3 provides an SEM image showing conformal coating of polyanilene over porous carbon nanofibers. Electrochemical characterization of the hybrid polyanilene/porous carbon nanofiber samples was conducted. Figure 4 shows the CV curve of the hybrid electrodes with 10 wt% polyanilene. CV shows clear polyanilene redox peaks exhibiting transformation from fully reduced leucoemeraldine to half oxidized emeraldine form. CV shows clear retention of electric double layer capacitance in the hybrid electrodes resulting in a total specific capacitance of over 250 F/g based on the weight of the complete electrode (porous carbon substrate and polyanilene).

Figure Captions

Figure 1: SEM images of mesoporous carbon nanofibers fabricated via high temperature calcination of the nanofibers electrospun using different material compositions generating different intra-fiber pore sizes. Scale bars = 500 nm. All samples exhibit >1500 m2/g specific surface area as measured using nitrogen physisorption (not shown).

Figure 2. Cyclic voltammetry curve of porous carbon nanofibers at various scan rates in 1M H2SO4.

Figure 3. SEM image of 10 wt% polyanilene conformally coated over porous carbon nanofibers.

Figure 4. Cyclic voltammetry curve of 10 wt% polyanilene coated over porous carbon nanofibers at 20 mV/s in 1M H2SO4.
Invited: New Generation Supercapacitors in Synergy with Li-Ion Technology
Authors: Naoi Katsuhiko , Naoi Wako
Published: February 2020

To meet growing demands for electric automotive and regenerative energy storage applications, researchers all over the world have sought to increase the energy density of electrochemical capacitors. Hybridizing battery and capacitor electrodes can overcome the energy density limitation of the conventional electrochemical capacitors because they employ both the system of a battery-like (redox) and a capacitor-like (double-layer) electrode, producing a larger working voltage and capacitance. However, to balance such asymmetric systems, the rates for the redox portion must be substantially increased to the levels of double-layer process, which presents a significant challenge.

An in situ material processing technology called “ultracentrifuging (UC) treatment” has been used to prepare a novel ultrafast Li4Ti5O12 (LTO) nanocrystal electrode for capacitive energy storage. In the present paper, the author will describe an extremely high performance supercapacitor that utilizes highly optimized “nano-nano-LTO/carbon composites” prepared via the UC treatment. The UC-treated LTO nanocrystals are grown as either nanosheets or nanoparticles, and both have hyperlinks to two types of nanocarbons: carbon nanofibers and supergrowth (single-walled) carbon nanotubes. The spinel structured LTO has been prepared with two types of hyperdispersed carbons. The UC treatment at 75000G stoichiometrically accelerates the in situ sol-gel reaction, hydrolysis followed by polycondensation, and further forms, anchors, and grafts the nanoscale LTO precursors onto the carbon matrices. The mechano-chemical sol-gel reaction is followed by a short heat-treatment process in vacuo. This immediate treatment with heat is very important for achieving optimal crystallization, inhibiting oxidative decomposition of carbon matrices, and suppressing agglomeration.

Such nanocrystal composites can store and deliver energy at the highest rate attained to this date. The charge-discharge profiles indicate a very high-sustained capacity of 80 mAh/g at an extremely high rate of 1200 C. Using this ultrafast material, we assembled a hybrid device called a “Nanohybrid capacitor” that consists of a Faradaic Li- intercalating LTO electrode and a non- Faradaic AC electrode employing an ion adsorption-desorption process. The “nanohybrid capacitor” cell has demonstrated remarkable energy, power, and cycleability performance as an electrochemical capacitor electrode. It also exhibits the same ion adsorption-desorption process rates as those of standard activated carbon electrodes in electrochemical capacitors.

The new-generation “Nanohybrid capacitor” technology produced more than triple the energy density of a conventional electrochemical capacitor. Moreover, the synthetic simplicity of the high-performance nanostructures makes it possible to scale them up for large-volume material production and further applications in many other electrochemical energy storage devices.
Study of Y2O3 Thin Film Prepared by Plasma Enhanced Atomic Layer Deposition
Authors: Cho Gu Young , Noh Seungtak , Lee Yoon Ho , Ji Sanghoon , Cha Suk Won
Published: February 2020

Atomic layer deposition (ALD) is a promised thin film deposition technique to fabricate nanometer scale thin films. Unlike chemical vapor depositions (CVDs), one cycle of ALD process is composed of separated precursor pulsing step, purging step and reactant pulsing step. Due to separated steps in an ALD process, precise thickness control of thin films is available. Step coverage, uniformity and conformality of thin films are also superior compared with other thin film techniques, such as sputter, pulsed laser deposition (PLD).

Plasma enhanced atomic layer deposition (PEALD) is energy reinforced ALD technique by inserting plasma. In case of a direct PEALD, plasma is induced during the reactant step to improve reactivity of reactant. The ALD window of PEALD is expanded especially at lower temperature due to high reactivity of plasma species. Better quality of thin films is available due to decreased contaminations within thin films and improved stoichiometry of thin films.

Y2O3 has wide band gap, good thermal stability, and high dielectric constant. Due to these characteristics, Y2O3 is used for various applications, such as, replacement of SiO2 in complementary metal oxide semiconductor (CMOS) devices, protective coatings, and buffer layers for ferroelectrics and superconductors. Y2O3 is also used to fabricate Yttria-stabilized zirconia (YSZ) which is the most typical electrolyte material for solid oxide fuel cells (SOFCs).

In this study, we prepared Y2O3 thin films by direct PEALD. Tris (methylcyclopentadienyl) yttrium ((MeCp3)3Y) precursor is used as a precursor of Y2O3 and high purity oxygen gas with O2 plasma is used as the reactant. The growth rate of Y2O3 thin films are measured by ellipsometer as a function of deposition temperature. Physical and chemical characteristics of Y2O3 thin films are also investigated which is deposited at different temperature.
Nanomechanical Properties of Tungsten Oxide (WO3) Grown by Atomic Layer Deposition
Authors: Mamun M A , Zhang Kai , Baumgart Helmut , Elmustafa A A
Published: February 2020

Tungsten oxide (WO3) films exhibit interesting properties, making them useful in various thin-film applications, such as smart windows or flat-panel displays [1], in electrochromic devices [2], gas sensors [3], and photocatalysis/photoconductivity [4]. Many of these applications are strongly dependent on tungsten oxide’s crystal morphology, microstructure, and mechanical properties. WO3 films of 200 and 600 ALD cycles were deposited on p-type Si (100) substrate using atomic layer deposition (ALD) technique and annealed at different temperatures. The 600 ALD cycle samples were annealed at 150, 250, and 300 °C, whereas the 200 ALD cycles sample was annealed at 250 °C. We tested these films for structural, surface morphology, and nanomechanical properties using nanoindentation. The structural and surface properties were explored using X-ray diffraction (XRD), scanning electron microscopy (SEM) and atomic force microscopy (AFM). We discuss the influence of the deposition technique on the structure and properties of the films citing the superiority of the ALD technique that is particularly used in the fabrication of the films that are presented in this study. The results in Figures 1 and 2 depict no significant difference in the hardness among the different films and annealing temperatures. The SEM image of Figure 3 shows radial cracks in the 600 ALD cycles annealed sample at 150 ˚C as an example. All other samples depict similar radial cracks.

References:

C.-G. Granqvist, Handbook of Inorganic Electrochromic Materials, Elsevier, Amsterdam (1995).

K. Bange, Sol. Energy Mater. Sol. Cells 58 (1999) 1.

M. Boulova, A. Gaskov, G. Lacazeau, Sens. Actuators, B, Chem. 81 (2001) 99.

F.B. Li, G.B. Gu, X.J. Li, H.F.Wan, Acta Phys. Chim. Sin. 16 (2000) 997.
Electrical and Structural Properties of W-Capped Er Ohmic Contact to n-Type in0.53Ga0.47As Channel
Authors: Leem Chang-Hyun , Kang Min-Sung , Lee Ye-Ji , Lim Yi-Rang , Shim Kyu-Hwan , Choi Chel-Jong
Published: February 2020

We have investigated electrical and microstructural properties of W-capped Er Ohmic contact to n-type In0.53Ga0.47As channel using (I-V) current-voltage characteristics, transmission electron microscopy (TEM) and X-ray diffraction (XRD). The interfacial reaction between Er and In0.53Ga0.47As driven by rapid thermal annealing (RTA) process led to the formation of Er-InGaAs alloy. The increase in the RTA temperature resulted in the degradation of surface and interface morphologies of Er-InGaAs alloy film, which could be associated with the reduction of its surface energy combined with intense interfacial reaction between Er and In0.53Ga0.47As. The specific contact resistivity of Er-InGaAs alloy film extracted using four-point (Kelvin) probe technique was investigated as a function of RTA temperature. The specific contact resistivity was found to vary with the variation in RTA temperature. Such a dependency of specific contact resistivity on RTA temperature could be attributed to the phase evolution surface/interface morphologies of Er-InGaAs alloy film. A minimum specific contact resistivity of ~ 10-6 Ωcm2 was achieved after RTA process at 400 °C.
Impurity in the Electroplated Sub-50nm Cu Lines
Authors: Huang Qiang , Avekians Alex , Ahmed Shafaat , Parks Christopher , Baker-O'Neal Brett , Kitayaporn Sathana , Sahin Asli , Sun Ying , Cheng Tien
Published: February 2020

Electroplated Cu lines has been successfully used in the back-end-of-the-line (BEOL) interconnects in the IC industry for more than a decades. As the devices continue to scale in the nanometer regime, the Cu interconnects face serious challenges in achieving the resistivity required for the performance. The reason why the Cu resistivity in narrow lines departs from its bulk value is believed to include surface scattering, impurity scattering and grain boundary scattering. Among them grain boundary scattering was believed to be one of the main mechanisms.[1,2]

While the Cu grains in the plated thick films or wide lines were found to grow at room temperature, this grain growth becomes more and more difficult as the lines width decreases. In the state-of-the-art BEOL structures, fine grained Cu has been typically observed at the bottom of the lines even after annealing at elevated temperature. One of the main reasons for this hindered grain growth is believed to relate to the much higher impurity in the plated Cu narrow lines.[3-9]

This study is focused on the effects of different plating additives on the impurity incorporation into the 40-nm wide Cu lines. For example, figure 1 shows the impurity profiles for the Cu lines plated with two different levelers. The impurity concentrations in the overburden can be lower or higher than the impurity concentrations in the narrow lines depending on the types and concentrations of leveler in the plating solutions. However, the impurity concentrations in the narrow lines are the same for all the cases in this study regardless of the types and concentrations of leveler. The impacts from suppressor, accelerator and chloride were also investigated. In addition, the effects of plating current density on impurity concentration will be discussed in the talk as well.

REFERENCES

1 W. Steinhögl et al., Physical Review B 66 (7), 075414 (2002).

2 W. Wu et al., Applied physics letters 84 (15), 2838 (2004).

3 S. H. Brongersma et al., Journal of materials research 17 (3), 582 (2002).

4 J. Sukamto and J. Reid, Proceedings of 205th ECS Meeting - International Symposium on Electrochemical Processing in ULSI and MEMS, San Antonio, TX, (2005).

5 W. Zhang et al., Electrochemical and Solid-State Letters 8, C95 (2005).

6 W. Zhang et al., Journal of The Electrochemical Society 152, C832 (2005).

7 M. Stangl et al., Microelectronic Engineering 85 (3), 534 (2008).

8 Q. Huang et al., Journal of The Electrochemical Society 159 (9), D526 (2012).

9 J. Kelly et al., Journal of The Electrochemical Society 159 (10), D563 (2012).

Fig. 1: IV characterization of Si solar cells after annealing at 300C for different time. The solar cells comprises (upper figure) Ni silicide and (bottom figure) NiCo-alloy silicide as the contact layer.
Comparison of Cu-Sn Compound Formation Between Snag and Pure Sn Solder Bumps by EBSD
Authors: Lee Ui-Hyoung , Lee Hyo-Jong , Kim Sang-Hyuk , Park Chae-Min , Shin Han Kyun , Bae Jong-yong , Won Jaihyung
Published: February 2020

Anisotropic behavior of Sn based solder during electromigration has been studied by many researchers, and it is very important to control the microstructure for more reliable bump joints[1]. Here, we prepared various SnAg bumps with different Ag concentrations including pure Sn[2]. Unary electroplating has various advantages such as easy handling bath, negligible bump composition and maintaining equipment with securing about environmental health and safety issue.

Figure 1 shows our preliminary experiments for the cross-sectional EBSD and EDS measurement of Cu pillar with pure Sn bump, and it is reflowed at 235°C for 6 min. In this study, we will report comparison of Sn microstructures according to various Ag inclusions by using cross-sectional EBSD(electron backscattered diffraction) analysis and EDS(energy dispersive spectroscopy) measurement. We carried out multiple reflows at various atmosphere how this impact IMC(intermetallic compound) growth along with microstructures. Through this crystallographic aspect approach, we will present optimum condition for resistance of electro migration and void formation.

[1] Yiwei Wang, Kuan H. Lu, Vikas Gupta, Leon Stiborek, Dwayne Shirley, Seung-Hyun Chae, Jay Im, Paul S. Ho, J. Mater. Res., 27, 1131 (2008)

[2] Ui-Hyoung Lee, Moongi Cho, Woojin Choi, Ha-Young You, Jinho Choi and Jaihyung Won, 224th ECS meeting, San Francisco, Oct. (2013)
Nanomechanical Properties of Standard and Strained SOI Films Fabricated by Wafer Bonding and Layer Splitting
Authors: Mamun M A , Zhang Kai , Baumgart Helmut , Elmustafa A A
Published: February 2020

High demands for improved performance, better power consumption, and miniaturized devices prompted the migration to SOI technology. SOI fabrication process helps in achieving greater performance and offers less power consumption compared to the Bulk Si Process. In SOI fabrication technology, transistors are built on a Si layer grown on SiO2 (145 nm) insulating layer. The SOI is fabricated using the SMART CUT wafer bonding and layer splitting technology. The strained Si on insulator (sSOI) technology has recently been developed for high mobility channel devices [1-3]. Biaxial tensile strained Si layers grown on SiGe have attracted great attention for high performance CMOS devices. Strain engineering for mobility enhancement is an attractive option to improve CMOS device performance by introducing lattice strain into the Si channel. Epitaxial Si1-xGex and most recently Ge-free bi-axially strained sSOI are among the leading candidates for higher mobility channel material.

In this paper, we have analyzed how the fabrication of very thin single crystal Si device films by wafer bonding and SMART CUTTM film exfoliation technique is affecting their nanomechanical properties in comparison to bulk Si. Although both the handle wafer and the bonded thin device layer are single crystal Si, it turns out that their nanomechanical properties differ considerably. Using nanoindentation, we measured the properties of (SOI-88nm) and bi-axially tensile strained Silicon-on-Insulator (sSOI 15, 70, and 100 nm) and benchmarked the results against bulk Si.

The results of Figure 1 indicate that the hardness of these films vary significantly. The field emission scanning electron microscopy (FE-SEM) image of Figure 2 represents an sSOI film of 100 nm thick.

References

C. Mazure and A.J. Auberton-Herve, Proc. of 35th
European Solid-State Device Research Conf. ESSDERC, p. 29 (2005)

T. A. Langdo, M. T. Currie, Z.-Y. Cheng, J.G. Fiorenza, M. Erdtmann, G. Braithwaite, C.W. Leitz, C.J. Vineis, J. A. Carlin, A. Lochtefeld, M. T. Bulsara, I. Lauer, D.A. Antoniadis, M. Somerville, Solid-State Electronics,
48 , 1357 (2004).

I. Cayrefourcq, A. Boussagol and G. Celler, in SiGe and Ge: Materials, Processing, and Devices
, ECS Trans. 3, (7), 399 (2006)
Epitaxial Growth and Layer Transfer of InP through Electrochemically Etched and Annealed Porous Buried Layers
Authors: Chen Douglas , Kou Xiaolu , Sareminaeini Sahar , Goorsky M. S.
Published: February 2020

Heterogeneous material integration, especially for III-V semiconductors, has enabled more possibilities in designing optoelectronic and electronic devices, and the ability to exfoliate the bonded devices layers and reuse the expensive substrates makes it economically advantageous. In our case, we propose a method using easily fractured porous layer to transfer an InP thin film from an InP substrate to an alternate substrate; e.g., glass or a flexible structure such as PDMS. Here, we demonstrate the formation of such a porous InP layer which exhibits a surface that is nearly fully dense as well as the ability to grow InP overlayers with low (< 106 cm-2) threading dislocation density. Also, we were able to transfer large area (> 1 cm2) InP layers onto PDMS substrates and glass slides.

In our studies on (001) InP, we have demonstrated that the pore formation can be controlled as a function of depth during electrochemical etching. For as-etched porous layers, AFM scans on a 40 X 40 μm2 area show the lowest surface r.m.s. less than 40 Å despite of the pore features. In order to achieve both high-quality epitaxial growth and facile layer fracture, a dual porous layer structure with a more porous (mechanically weaker) under-layer was designed and fabricated by either adjusting the etching current density or changing the switching electrolyte concentration.

The structures were annealed to understand the morphological evolution of the pore structure and to test the structural stability under simulated epitaxial growth condition. Under N2-purged environments, we observed that the surface remains stable (no change in surface pore morphology) with even slight improvement on roughness up to 550 °C and the layer maintained its porous structure at 650 °C. Large voids were observed after annealing at the interface between the high porosity buried layer and substrate, which is consistent with the ease by which it is to remove top layers from the substrate after annealing. Epitaxial layers were grown about 2 μm thick on porous surfaces with different porosities and both a cross-section TEM sample and a plan-view sample (> 35 μm2) were used to characterize the epitaxial growth. Since no observable threading dislocations were found in the plan-view sample, it sets a limit on the threading dislocation density in the mid-106 cm-2 range.

Samples with dual porous layers were bonded to flexible PDMS substrates and easily peeled off due to the fracture at the high porosity layer. Another set of samples were bonded to glass slides with epoxy glue and the fractured surface was characterized under SEM.
Chemical Mechanical Polishing of III-V Materials for Wafer Bonding Applications
Authors: McKay Jeffrey , Goorsky M. S. , Chen Douglas , Sareminaeini Sahar
Published: February 2020

ABSTRACT

Wafer bonding of III-V cells offers opportunities to integrate materials with different bandgaps and different lattice parameters without forming high defect densities. However, growth conditions that produce the best cells do not necessarily produce epitaxial layer surfaces that are suitable for wafer bonding. The chemical mechanical polishing of III-V materials including GaAs, InP, InAs, and alloy layers used in high efficiency III-V solar cell structures is investigated with sodium hypochlorite and citric acid solutions. It is found that the surfaces can be polished to below 0.5 nm RMS surface roughness without the induction of crystalline damage using similar abrasive-free polishing solutions for all the materials with controlled polishing rates of 10 nm / min. The low removal rate is key for applications that include epitaxial layers that must be subsequently polished without l=excessive loss of material. The actual composition of the slurry is adjusted for the particular alloy composition. A balance between reduced sub-surface mechanical damage and smooth surface morphology is obtained by adjusting the amount of citric acid similar to Br-methanol polishing. However, the damage-free planarization in these cases may be aided by an oxide formation as predicted by Pourbaix diagrams. Subsequent bonding suing sulfur passivation on the CMP surface shows excellent electrical characteristics with low resistivity as well as high strength bonding after annealing at 400 °C. Additionally, triple axis x-ray diffraction is found to be an extremely sensitive, non-destructive method for evaluating damage induced by the CMP process.
Invited: Wafer-Bonding for MEMS – Status and Trends
Authors: Hausner Ralf
Published: February 2020

The current sensor portfolio at Bosch is covering a large variety of different MEMS-based sensor products for automotive and consumer applications. Examples for automotive applications are pressure sensors for engine control, side impact detection and inertial sensors for airbag systems, navigation and vehicle-dynamics control (ESP). Examples for consumer applications are inertial sensors for gaming, freefall detection in laptops, switching in mobile-phones and pressure sensors used as altimeter, barometer and indoor navigation. Among the different wafer bonding techniques for wafer-level packaging that are shown in figure 1, anodic bonding, glass-frit and eutectic bonding are state-of the-art for MEMS sensors and the metallic bonding processes thermo-compression and solid-liquid interdiffusion (SLID) bonding have a high potential for future applications.

The basic features that wafer bonding technologies for MEMS must fulfil for a successful wafer-level packaging process are hermeticity, high bond strength and high temperature stability. Glass-frit and anodic bonding are well and long-term established standard technologies used for hermetic packaging of MEMS on wafer-level. But both technologies require comparatively large chip sizes that are not compatible with the requirements for miniaturization and cost reduction of new consumer sensors. Therefore metallic bonding processes like eutectic bonding with aluminium-germanium were used for new consumer sensors. Typically, the bond frame size with the eutectic bond can be reduced by a factor of 2 in combination with a frame that stops the liquid eutectic material in lateral extent. With eutectic bonding very small chip sizes are possible resulting in shrinking the size of Bosch accelerometers as shown in figure 2. One step further is the realization of hermetic encapsulation and electrical interconnection, if an ASIC wafer serves as a functionalized cap. Cu-Cu thermo-compression and Cu / Sn SLID bonding are promising techniques that are of high interest for MEMS products of the future.

The wafer bonding processes used and under development at Bosch, examples, advantages, disadvantages and challenges will be described.

Figure 1: Overview of waferbonding technologies.

Figure 2: Shrinking the chip-size for smaller accelerometers was promoted by the change from glass-frit to eutectic wafer bonding.
Detection of Ge and Si Intermixing in Ge/Si Using Multiwavelength Micro-Raman Spectroscopy
Authors: Yoo Woo Sik , Kang Kitaek , Ueda Takeshi , Ishigaki Toshikazu , Nishigaki Hiroshi , Hasuike Noriyuki , Harima Hiroshi , Yoshimoto Masahiro , Tan Chuan Seng
Published: February 2020

To meet various physical property requirements of materials for advanced application specific devices, combinations of Si/Ge, Ge/Si, Si1-xGex/Si are frequently introduced in the device fabrication process. Epitaxy, condensation and annealing processes are commonly used. Since a small variation in composition, strain and crystallinity can result in reduced device performance or failure, the composition, strain and crystallinity must be carefully monitored and controlled throughout the manufacturing process.

In this study, we report the detection of Ge and Si intermixing in epitaxially grown Ge/Si after successive thermal anneals using multiwavelength Raman spectroscopy. We have studied dependence of Ge and Si intermixing on annealing temperature and Raman on excitation wavelength. Very strong excitation wavelength and film structure dependence of signal-to-noise (S/N) ratio of measurements was observed. Suitable excitation wavelengths must be chosen to properly detect and characterize Si and Ge intermixing, based on the stacking order of epitaxial films and thicknesses.

Figure 1 shows 514.5nm excited Raman spectra from reference Si, reference Ge and epitaxially grown Ge/Si wafers before and after thermal annealing. As grown Ge/Si wafers showed very distinct Ge and Si Raman peaks. Si and Ge intermixing was found in one annealing condition. Ge epitaxial was converted to Si1-xGexafter annealing.

S/N ratio of measurements and their dependence on excitation wavelength and film structure dependence will be discussed. Excitation wavelength selection guidelines will be proposed.
Paintable Thermoelectric Materials from Polymer Blends of Exfoliated 2D Nanosheets
Authors: Carroll Elaine , Buckley Darragh , Collins Gillian , O'Dwyer Colm
Published: February 2020

In bulk form the thermoelectric material bismuth telluride (Bi2Te3) has a high figure of merit (ZT) at room temperature. When bulk Bi2Te3 is exfoliated to smaller dimensions, such as its 2D form (nanosheets), its thermoelectric effects are improved by reduction in thermal conductivity due to phonon confinement and scattering, thus increasing the ZT. The difficulty involved in incorporating nanosheets into energy harvesting systems motivated the search for a form of Bi2Te3 that retains the high ZT apparent at the nanoscale with the capability of being deposited or painted onto device infrastructures.

This work highlights a method whereby solvent exfoliation of Bi2Te3 into solution-dispersible 2D nanosheets can form a practical thin film that can be distributed across a surface. Optical transmission measurements quantify the relationship between efficient and stable exfoliation and the reduction in optical density. Optimized exfoliated suspension are also shown to form smooth, uniform blends when mixed with poly ethylene glycol and other polymers to produce a paintable Bi2Te3film that can be applied to surfaces using an innovative painting technique.

Atomic force microscopy, transmission electron spectroscopy, Raman spectroscopy and scanning electron spectroscopy are used to examine the structure of the 2D nanosheets and the highly reproducible Bi2Te3 thin films. Electrical transport studies show that the films have conductive pathways over a range of surfaces and various structural formations, linking the conductivity to the percolating conduction through the nanosheet ensemble. The combination of the facile preparation method and the scope for diverse surface coating as a cohesive and conductive thin film offers a methods for integration with heat producing devices for energy harvesting applications.

References

K. M. F. Shahil, M. Z. Hossain, D. Teweldebrhan and A. A. Balandin, Applied Physics Letters, 96 (2010).

B. Poudel, Q. Hao, Y. Ma, Y. Lan, A. Minnich, B. Yu, X. Yan, D. Wang, A. Muto, D. Vashaee, X. Chen, J. Liu, M. S. Dresselhaus, G. Chen and Z. Ren, Science, 320, 634 (2008).

M. Saleemi, M. S. Toprak, S. Li, M. Johnsson and M. Muhammed, Journal of Materials Chemistry, 22, 725 (2012).

L. E. Bell, Science, 321, 1457 (2008).

S. Li, M. S. Toprak, H. M. A. Soliman, J. Zhou, M. Muhammed, D. Platzek and E. Müller, Chemistry of Materials, 18, 3627 (2006).

Y. Hernandez, N. Valeria, L. Mustafa, B. F. M., S. Zhenyu, S. De, M. T., B. Holland, M. Byrne, Y. K. Gun'Ko, J. J. Boland, P. Niraj, G. Duesberg, S. Krishnamurthy, R. Goodhue, J. Hutchison, V. Scardaci, A. C. Ferrari and J. N. Coleman, Nature Nanotechnology, 3, 1748 (2008).

V. Nicolosi, M. Chhowalla, M. G. Kanatzidis, M. S. Strano and J. N. Coleman, Science, 340 (2013).

L. D. Hicks and M. S. Dresselhaus, Physical Review B, 47, 12727 (1993).
Thermal and Thermoelectric Transport in Semiconductor Nanostructures
Authors: Chen Renkun
Published: February 2020

During the last decade or so we have witnessed tremendous advancement in characterization and understanding of thermal transport in nanostructures, particularly in the ‘phonon boundary scattering’ regime where the characteristic size of nanostructures ranges from tens to hundreds nanometers and is comparable to phonon mean free path. This understanding is the key underlying reason for improved performance observed in nanostructured thermoelectric materials. However, it is increasingly clear that the boundary scattering mechanism may soon reach its limit and new mechanisms for improving thermoelectric performance need to be explored. One of the opportunities may arise from the study of thermal transport in the so-called ‘confinement’ regime, where the characteristic size of nanostructures is below 10-20 nanometers and is comparable to phonon wavelength. In this work, we will discuss our recent work on using rationally designed nanostructures to study nanoscale thermal and thermoelectric transport phenomena in this regime. We will describe the instrumentation we have been developing that enables the characterization of thermal transport and related properties of these nanostructures and discuss and interpret the measurement results.
Graded Index Transparent Conducting Materials with Enhanced Optical Functionality
Authors: O'Dwyer Colm
Published: February 2020

Transparent conducting oxides (TCO) have been extensively used in various technologically important applications including solar cells, flat panel displays, antireflective coatings, (organic)light emitting diodes and many other uses as advanced optical materials. Nanoporous and nanostructured films, assemblies and arrangements are important from an applied point of view in microelectronics, photonics and optical materials.

The ability to minimize reflection, control light output and use contrast and variation of the refractive index to modify photonic characteristics can provide routes to enhanced photonic crystal devices, omnidirectional reflectors, antireflection coatings and broadband absorbing materials.

This work demonstrates very high quality epitaxially grown (MBE) indium oxide, and indium tin oxide nanostructures and nanowires that are defect free and grown using homogeneous ITO seeds from glass or semiconducting surfaces. These branched and graded porosity layers grown directly on LEDs, glass coatings and other devices are shown to significantly enhance transparency or absorbance, depending on the visible wavelength range of interest and suppress Fresnel reflections for antireflection coatings. The benefit of controlling optical properties of nanoporous transparency conducting materials are shown for SiGe MQW LEDs, transparent Li-ion battery electrodes, antireflection coatings, and selective frequency absorbers across the visible range, and also demonstrates control over IR transmission without adversely affecting electronic conductivity.

References

C. M. Eliason and M. D. Shawkey, Optics Express,
22 A642 (2014).

C. O'Dwyer, M. Szachowicz, G. Visimberga, V. Lavayen, S. B. Newcomb and C. M. S. Torres, Nature Nanotech., 4, 239 (2009).

C. O'Dwyer and C. M. S. Torres, Front. Physics, 1, 18 (2013).

M. Osiak, W. Khunsin, E. Armstrong, T. Kennedy, C. M. S. Torres, K. M. Ryan and C. O'Dwyer, Nanotechnology, 24, 065401 (2013).

M. Osiak, E. Armstrong, T. Kennedy, C. M. S. Torres, K. M. Ryan and C. O'Dwyer, ACS Appl. Mater. Interfaces, 5, 8195 (2013).

P. D. C. King, T. D. Veal, J. Phys.
23, 334214 (2011).

J. Q. Xi, M. F. Schubert, J. K. Kim, E. F. Schubert, M. Chen, S. Y. Lin, W. Liu and J. A. Smart, Nature Photonics, 1, 176 (2007).
Metal Decorated Carbon-Based Materials for Transparent Conductive Thin Films
Authors: Wang Po-Hsuan , Chiang Wei-Hung , Liao Ying-Chih
Published: February 2020

A facile approach to decorate carbon-based materials, such as graphene oxides (GOx) and carbon nanotubes (CNTs), with metal nanoparticles was developed to enhance the electrical conductivity of coated thin films. CNTs were first surface-functionalized with hydroxyl, carbonyl, and carboxyl functional groups using a simple and green method without strong acid. The as-prepared CNTs were then dispersed in solvents and coated on PET or glass substrates to form conductive thin films. Copper or silver nanoparticles were then decorated on the functionalized CNT films using formaldehyde as a reduction agent. The microstructures of metallized thin films were characterized by FESEM, XRD, and UV measurements. The electrical and mechanical properties of the composite thin films were measured and compared with regular CNT films. The results showed that electrical conductivity of CNT thin films were greatly enhanced after the metallization process. This simple method can be also applied to two-dimensional nanostructured GOx materials to provide thin films with both good transparency and conductivity.