bluuebunny/crossref_metadata_2025 huggingface dataset:
Anodic-like Wafer Bonding of Copper/Silicon Done at Room Temperature by Schottky Barrier Structure
Authors: Lee Benjamin T. -H. , Cheng Lin
Published: February 2020

Metal, e.g. copper or aluminum, is difficult to be firmly bonded with silicon if only thermally treated at room temperature, because the surface status of the silicon substrate is usually in covalent bonds.

However, the low temerature Cu/Si bonding structure is usually achieved by pre-depositing Cu layer on the surfaces of the silicon at relative high temperature prior to bonding. In practice, this bonding is one type of copper-to-copper bonding. In this kind of bonding case, annealing temperature is normally at several hundred °C as well. Another way is to employ a so-called “low temperature” (400°C or below) thermo-compression bonding technique to create the Si/Cu structure. The first step is to deposit a Cu layer on the surface of blanket silicon wafer. Then, in practice, the two Cu surfaces were joined together with mechanical pressing and heating simultaneously for tens of minutes.

In the study, we demonstrated the copper-silicon bonding pair formed via an electrochemical processing at room temperature. The silicon substrates were double-side polished, phosphorus- doped, N-type (100) silicon wafer with resistivity of 1−10 Ω cm. The surface of copper plate was also polished. Prior to electrochemical processing, all the silicon specimens were cleaned at 80 °C in the following solutions: NH4OH:H2O2:H2O = 1:1:5 and HCl:H2O2:H2O = 1:1:6. Then silicon specimens were dipped in 0.5% HF solution for 30 seconds to remove all native oxide layer. Via a hydrophobic wafer bonding processing with HF dipping, the silicon specimen was bonded with the polished copper plate which is also as an anode electrode. The electrochemical anodization was performed in darkroom at a constant current density of 50 mA/cm2 with a platinum cathode in the electrolyte. After the electrochemical processing, we found copper was teared off and then firmly attached on the silicon surface when we tried to separate the bonded pair. We proposed that the carrier-mediated rectification through the Schottky junction of metal-semiconductor contact allows electrons drain to the copper electrode, thereby greatly increasing the hole density at the interface on the side of silicon substrate, i.e. activating the silicon dangling bonds. Once the electrons drained off to the copper electrode from silicon surface, the bonds formed on the Cu surface were also greatly activated to be bonded to silicon bonds. This kind of bonding technique of copper/silicon or metal/ceramic materials may be applied to the additive manufacturing for 3-D microstructure.

Figure 1: The copper layer was directly teared from bulk copper and then transferred onto silicon after electrochemical processing at room temperature for two hours. It appears the bonding strength between copper and silicon is stronger than the bond strength of copper.

Figure 1
Influence of Composition of SiCN Film for Surface Activated Bonding
Authors: Inoue Fumihiro , Peng Lan , Iacovo Serena , Phommahaxay Alain , Visker Jakob , Verdonck Patrick , Meersschaut Johan , Dara Praveen , Sleeckx Erik , Miller Andy , Beyne Eric
Published: February 2020

Surface activated dielectric bonding is more and more attractive as a key technology to achieve further high-performance CMOS based devices independent on scaling. The major challenge of dielectric bonding is to decrease the process temperature in order to be compatible with CMOS processing. Although the conventional SiO2-SiO2 bonding has already been comprehensively investigated, there might be some limitations in terms of thermal budget. In the past, we have demonstrated low temperature bonding using PECVD-SiCN as interfacial layer, where we have obtained more than 2200 mJ/m2 of adhesion energy at 250 oC of post annealing temperature [1].

In this work, the composition of SiCN has been tuned aiming at the identification of the key elements taking part in the bonding mechanism and to further increase the adhesion energy.

The SiCN composition was successfully controlled by tuning the CVD deposition process, as it is proven by elastic recoil detection (ERD) measurements which enable us to monitor the ratio of the different elements (C,N,H,O, Si) in the different films. A table with ERD results is reported below. Also, the film densities are determined by using the mass differences of the processed wafers. The density becomes lower with increasing carbon concentration. The density variation impacts the CMP removal rate, which is critical for actual hybrid bonding process. On the other hand, no difference on the roughness is seen for all SiCN films.

After film planarization by CMP, wafer bonding test were done on 300 mm wafers by combining a pair of the same films as interfacial layer. Prior to bonding, N2 plasmas were applied on the both surfaces. No voids were observed for all the pairs, even after post bond annealing. The highest bonding strength is obtained from the carbon rich SiCN (SiCN #2). This indicates that the higher adhesion by SiCN may be attributed to the carbon dangling bond formed by plasma activation, rather than hydrogen or nitrogen.

Further mechanisms are discussed to understand the present low-temperature bonding technique.

[1] E. Beyne et.al., “Scalable, sub 2µm Pitch, Cu/SiCN to Cu/SiCN Hybrid Wafer-to-Wafer Bonding Technology” IEEE IEDM 2017, 32.4.1 (2017)

Figure 1
Pseudocapacitive Behavior of Polycationic Oxides for Electrochemical Capacitors
Authors: Crosnier Olivier , Goubard Nicolas , Buvat Gaëtan , Favier Frederic , Douard Camille , Brousse Thierry
Published: February 2020

Electrochemical double-layer capacitors (EDLCs) represent the most important family of today’s commercially available Electrochemical Capacitors (ECs). Such systems can store charges electrostatically in the electrochemical double-layer that arises from the separation of charges at the electrode / organic electrolyte interfaces when polarizing the electrodes, and exhibit an excellent cycling stability combined with fair gravimetric and volumetric energy densities. Other types of ECs use “pseudocapacitive” materials, i.e. materials that use fast and reversible surface redox (faradaic) reactions to store energy. To combine the advantages of both organic EDLCs and aqueous symmetric systems, the design of aqueous asymmetric supercapacitors was proposed. These devices comprise either two pseudocapacitive materials, or a pseudocapacitive and a capacitive carbon-based material which exhibit complementary electroactive windows. As a result, operating cell voltages approaching 2 V can be obtained, leading to competitive energy densities without the disadvantages of using an organic electrolyte.

Both specific energy and power densities have to be increased and improving the volumetric capacitance of supercapacitors, which is one of the limiting factors of today’s stationary applications, is essential. In order to meet these requirements, solid state chemistry is an powerful tool to design new materials. Our strategy was based on the study of polycationic oxide materials. They can combine transition metals such as Fe or Mn, that are known to be electrochemically active in aqueous media, with dense elements such as W, Bi,… The Fe/W/O has a peculiar interest since our recent studies have shown that FeWO4 exhibit excellent electrochemical properties [1,2]. Its pseudocapacitive behaviour has been demonstrated by operando XAS experiments with the use of a special cell designed in our lab [3].

The use of low-temperature synthesis methods in order to get nanosized particles with high specific surface areas is also required. Synthesis conditions and materials characterizations of the electrodes and also of full devices will be detailed in the presentation, highlighting the crucial role of the electroactive elements, the crystallographic structure, and the morphology of the synthesized materials on their electrochemical performance.

[1] N. Goubard-Bretesché, O. Crosnier, C. Payen, F. Favier, T. Brousse, Electrochem.
Commun. 57 (2015) 61.

[2] N. Goubard-Bretesché, O. Crosnier, F. Favier, T. Brousse, Electrochim. Acta 206 (2016), 458.

[3] N. Goubard-Bretesché, O. Crosnier, C. Douard, A. Iadecola, R. Retoux, C. Payen, F. Favier, M.-L. Doublet, T. Brousse, in preparation.
(Invited) Deconvolution of Double-Layer, Pseudocapacitance, and Battery-like Contributions to Charge Storage in MnOx@Carbon Electrode Architectures and Interfaces
Authors: Long Jeffrey W. , Ko Jesse S. , Sassin Megan B. , Parker Joseph F. , Rolison Debra R.
Published: February 2020

Manganese oxides (MnOx) are a well-established class of active materials for electrochemical energy-storage technologies ranging from primary alkaline cells to rechargeable Li-ion batteries. More recently, the use of manganese oxides has extended to aqueous-electrolyte electrochemical capacitors (ECs) in which nanostructured forms of MnOx exhibit pseudocapacitive charge-storage behavior that can be tapped for pulse-power applications. The ability of MnOx to alternately express battery-like and capacitor-like functionality offers intriguing prospects to design electrode materials and corresponding devices that deliver both high energy content and rapid charge/discharge response. We are exploring such opportunities with electrode architectures comprising nanoscale MnOx coatings affixed to porous carbon frameworks [1,2,3]. The battery- and capacitor-like character of these materials can be tuned by varying such factors as the oxide crystal structure (layered birnessite-MnOx vs. cubic spinel LiMn2O4) and the composition of the contacting electrolyte (mixtures of Na+, Li+, and/or Zn2+) [4]. To deconvolve the complex electrochemical response of such systems, we apply a suite of electroanalytical methods that are based on voltammetry and impedance. The 3D projection of Bode-plot parameters has proven particularly useful in mapping frequency-dependent capacitance contributions onto the potential scale, revealing mechanisms that deliver/store charge at high rates. In parallel with investigations of macroscale electrode architectures, we also examine simplified 2D MnOx//carbon interfaces where surface-sensitive characterization methods (X-ray photoelectron spectroscopy, scanning-probe microscopy) provide insights on the impact of the carbon substrate on charge-transfer kinetics, charge-storage mechanisms, and stability.

E. Fischer, K.A. Pettigrew, D.R. Rolison, R.M. Stroud, and J.W. Long, Nano Letters
2007, 7, 281–286.

W. Long, M.B. Sassin, A.E. Fischer, and D.R. Rolison, J. Phys. Chem. C
2009, 113, 17595–17598.

B. Sassin, S.G. Greenbaum, P.E. Stallworth, A.N. Mansour, B.P. Hahn, K.A. Pettigrew, D.R. Rolison, and J.W. Long, J. Mater. Chem. A
2013, 1, 2431–2440.

S. Ko, M.B. Sassin, J.F. Parker, D.R. Rolison, and J.W. Long, Sustainable Energy Fuels, 2018, 2, 626–636.
Impact of Carbon Structure over the Pseudocapacitive K-Ion Storage in New Cobalt-Manganese Oxides Derived from Coordination Compounds
Authors: Vazquez Juvencio , Ramírez Guadalupe , Acevedo-Peña Prospero , Oliver-Tolentino Miguel Angel , Guzmán-Vargas Ariel
Published: February 2020

The rapidly growing use of intermittent energy sources such as solar and wind power to generate electricity requires the development of reliable, affordable, and efficient electric energy storage systems [1]. Electrochemical capacitors are excellent devices that have a high power (>10 kW kg-1), high rate capability and long cycle life (>1 000 000 cycles) [2]. A great diversity of materials has been widely investigated as supercapacitor electrodes, such as carbon materials, graphene-based composites metal hydroxides and metal oxides. In this work, a new pseudocapacitive materials were obtained by thermal descomposition of cyanometalates formed by precipitation over different carbon structures (graphene oxide, carbon nanotubes and mesoporous carbon). The materials were thoroughly characterized using XRD, FRX, Raman, ATR-FTIR, SEM, TEM and XPS. Furthermore, the electrochemical performance of the materials was tested by cyclic voltammetry, step potential electrochemical spectroscopy, electrochemical impedance spectroscopy and charge-discharge curves at different current rates in 1 M NaOH. The material formed in presence of graphene oxide exhibited the best electrochemical behavior, maintaining 98% of its initial capacitance after 500 cycles at 1 Ag-1.

References

Yang, J. Zhang, M. C.W. Kintner-Meyer, X. Lu, D. Choi, J. P. Lemmon, J. Liu, Chem. Rev. Electrochemical Energy Storage for Green Grid. 2011, 111, 3577 – 3613.

S. Aric, P. Bruce, B. Scrosati, J.-M. Tarascon, W. V. Schalkwijk, Nanostructured materials for advanced energy conversion and storage devices. Nat. Mater. 2005, 4, 366 – 377
(Invited) One Dimensional Nanomaterials for Emerging Energy Storage
Authors: Mai Liqiang
Published: February 2020

One-dimensional nanomaterials can offer large surface area, facile strain relaxation upon cycling and efficient electron transport pathway to achieve high electrochemical performance. Hence, nanowires have attracted increasing interest in energy related fields. We designed the single nanowire electrochemical device for in situ probing the direct relationship between electrical transport, structure, and electrochemical properties of the single nanowire electrode to understand intrinsic reason of capacity fading. The results show that during the electrochemical reaction, conductivity of the nanowire electrode decreased, which limits the cycle life of the devices. We have developed a facile and high-yield strategy for the oriented formation of CNTs from metal−organic frameworks (MOFs). The appropriate graphitic N doping and the confined metal nanoparticles in CNTs both increase the densities of states near the Fermi level and reduce the work function, hence efficiently enhancing its oxygen reduction activity. Then, we fabricated a field-tuned hydrogen evolution reaction (HER) device with an individual MoS2 nanosheet to explore the impact of field effect on catalysis. In addition, we demonstrated the critical role of structural H2O on Zn2+ intercalation into bilayer V2O5·nH2O. The results suggest that the H2O-solvated Zn2+ possesses largely reduced effective charge and thus reduced electrostatic interactions with the V2O5 framework, effectively promoting its diffusion. We also identified the exciting electrochemical properties (including high electric conductivity, small volume change and self-preserving effect) and superior sodium storage performance of alkaline earth metal vanadates through preparing CaV4O9 nanowires. Our work presented here can inspire new thought in constructing novel one-dimensional structures and accelerate the development of energy storage applications.

L. Q. Mai, Y. J. Dong, L. Xu and C. H. Han. Nano Lett. 10, 4273 (2010).

L. Q. Mai, M. Y. Yan and Y. L. Zhao, Nature. 546, 469(2017).

J. S. Meng, C. J. Niu, L. H. Xu, J. T. Li, X. Liu, X. P. Wang, Y. Z. Wu, X. M. Xu, W. Y. Chen,Q. Li, Z. Z. Zhu, D. Y. Zhao and L.Q. Mai. J. Am. Chem. Soc. 139, 8212 (2017).

J. H. Wang, M. Y. Yan, K. N. Zhao, X. B. Liao, P. Y. Wang, X. L. Pan, W. Yang, L. Q. Mai. Adv. Mater.
29 (2016 ).

M. Y. Yan, P. He, Y. Chen, S. Y. Wang, Q. L. Wei, K. N. Zhao, X. Xu, Q. Y. An, Y. Shuang, Y. Y. Shao, K. T. Mueller, L. Q. Mai, J. Liu, and J. H. Yang. Adv. Mater. 1703725 (2017).

X. M. Xu, C. J. Niu, M. Y. Duan, X. P. Wang, L. Huang, J. H. Wang, L. T. Pu, W. H. Ren, C. W. Shi, J. S. Meng, B. Song and L. Q. Mai. Nature Commun. 8, 460 (2017).
Surface-Controlled Charge Storage Mechanism of Graphene for Alkali Metal Ion Storage
Authors: Lee Byeongyong , Kwon Seok Joon , Kim Sunkyung , Jang Hee Dong , Lee Seung Woo
Published: February 2020

Lithium-ion batteries (LIBs) have been dominant power sources for portable electronics and electric vehicles (EVs). However, the shortage of the natural abundance and biased global distribution of lithium (Li) resources may present unavoidable challenges in the future. As such, Na- and K-ion batteries (NIBs and KIBs) have attracted attention to diversify the power sources. Graphite is the most widely used anode material for commercial LIBs based on the Li-ion intercalation mechanism. However, the capacities of graphite as Na- and K-ion insertion host is limited than that of Li. In this study, we show that graphene is a promising candidate to store Na and K-ions through a surface-controlled charge mechanism. We correlate the charge storage capacity for alkali metal ions with their binding energy on the graphene surface. We systematically modify the structure of graphene to improve the charge storage capacity for Na- and K-ion storage. Finally, we reveal that graphene can efficiently store Na and K ions through the surface-controlled capacitive mechanism, exhibiting the enhanced rate-capability and excellent cycling stability.
A New Type of Tetragonal LixMn2O4 Electrode Exhibiting Combined Pseudocapacitance and Battery Behaviors and Self-Healing Cycle Stability in Aqueous Electrolytes
Authors: Abdollahifar Mozaffar , Wu Nae-Lih
Published: February 2020

Among several energy storage technologies, supercapacitors have achieved considerable attention because of their rapid charge-discharge rates, high power density, and excellent cycling stability, but low energy density and fast self-discharge are some of serious disadvantages for the supercapacitors. Electrodes with combination of battery and pseudocapacitance behaviors offer the advantages of both supercapacitors and the advanced batteries, it shows higher energy density and the same time maintains the extended cycle life and fast charge capability. In this study, a new type of tetragonal LixMn2O4 (LMO) electrode exhibiting combined pseudocapacitance and battery behaviors in aqueous electrolytes has been synthesized by electrochemical cation-exchange conversion from ZnMn2O4 (ZMO) [1]. It is shown that the Zn+ ion in ZMO can be replaced by the Li+ ion, resulting in the formation of LMO in aqueous Li2SO4 electrolytes by cyclic voltammetry. The resulting LMO electrode is in tetragonal structure but yet exhibits redox potentials essentially the same as those of the cubic LMO (Fig. a), delivering a redox capacity over 100 mAh/g under low current rate or a specific capacitance of nearly 300 F/g when behaving as a pseudocapacitor at higher current rates. Despite its tetragonal structure, the electrode shows outstanding cycle stability, exhibiting an interesting self-healing structure transformation process to the cubic structure and retaining 100% capacity after 40, 000 cycles. Using the high-concentration LiTFSI electrolyte enables the expansion of operating potential window to 1.55 V. The material synthesis process and charge-transfer mechanism are characterized in detail.

[1] M. Abdollahifar, S.S. Huang, Y.H. Lin, Y.C. Lin, B.Y. Shih, H.S. Sheu, Y.F. Liao, N.L. Wu, J. Power Sources 378, 90, 2018.

Figure 1
Rationally Selecting Manganese Oxide Electrodes for Salinity Gradient Energy Production
Authors: Fortunato Jenelle , Kim Taeyoung , Gorski Christopher A
Published: February 2020

Electricity can be generated from the controlled mixing of salinity gradients (i.e., two waters with different salt concentrations). Capturing salinity gradient energy using existing technologies such as Pressure Retarded Osmosis and Reverse Electrodialysis are limited by membrane fouling and costs. Capacitive electrode technologies, like capacitive mixing, may be used to overcome the limitations of membrane-based technologies by taking advantage of capacitive double layer expansion (CDLE) at the electrode surface to generate power. However, due to intrinsically low charge storage capacities, researchers have begun to explore pseudo-capacitive electrode materials, such manganese oxides. The charge-storage capabilities of pseudo-capacitive materials differs from purely capacitive materials in that that they can store charge via faradaic, redox reactions between the cations and the oxide crystal structure (MnOO + Na+ + e- = MnOONa). Presently, the exact charging mechanisms involved when manganese oxide electrodes harness salinity gradient energy are poorly understood. The goal of this study is to optimize the performance of a salinity gradient flow cell using MnO2 electrodes by determining the charge-discharge mechanism of manganese oxide structures, which will facilitate rational material selection in the future. Material characterization tests, cyclic voltammetry analysis, and galvannostatic charge-discharge tests were used to characterize and compare a suite of manganese oxide powders that varied by crystal structure (amorphous, δ, γ, α, and β) and morphology (nanorod, sphere, urchin, and plate-like). Subsequently, flow cell experiments were performed with varying solution chemistries to obtain information on power production, stability, and cyclability. Preliminary flow cell experiments show that open circuit voltage window and power production for MnO2 structures decreases in the order of amorphous, α, β, which follows the trend for BET surface area (amorphous > α > β). Additionally, electrochemical tests indicate the material is stable over multiple cycles and CV deconstruction shows that charge storage capabilities of MnO2 may be largely attributed to surface reactions; suggesting that BET surface area may potentially be used as an indicator of performance for harnessing salinity gradient energy.
Solid State Electrochemical Capacitors
Authors: Bélanger Daniel , Bordjiba Tarik
Published: February 2020

Solid-state electrochemical capacitors were prepared by combining composite electrodes based on a carbon paper/carbon nanotubes assembly coated with a layer of a pseudocapacitive electrode materials such as manganese dioxide or ruthenium dioxide separated by a solid state membrane to support the electrolyte. The composite electrodes were prepared by using a simple slow filtration technique. The electrolytes consist of ion-exchange membranes (such as Nafion or CMX from Neosepta) that are impregnated with an appropriate electrolyte. Acidic and neutral electrolytes were investigated in this work. Symmetrical electrochemical capacitors were prepared with two similar electrodes. Different combinations of electrode and membrane were assembled and characterized electrochemically by cyclic voltammetry and constant current charge/discharge cycling. The effect of cycling rate and temperature (from – 60 to + 60 °C) on the electrochemical performance of the solid-state electrochemical capacitors was evaluated.
(Invited) Atomic Layer Processing from an Etching Perspective
Authors: Lill Thorsten , Berry Ivan , Fischer Andreas , Shen Meihua , Vahedi Vahid
Published: February 2020

Atomic Layer Etching (ALE) transitioned to manufacturing because of unique performance benefits which come from self-saturation of the steps and the use of very low ion energies or just thermal means to remove material. The former property gives uniformity across all lengths scales on the wafer. Reduced aspect ratio dependent etching (ARDE) and surface smoothness are very attractive benefits. Low level removal energies deliver selectivity which is a key requirement for etching with atomic scale fidelity.

In this talk, a conceptual framework for directional and isotropic ALE will be compared to other etching technologies for semiconductor devices. Recent experimental and theoretical results as well as applications examples will be presented to illustrate the concepts.
(Invited) Atomic Layer Deposition in Life Science Applications
Authors: Sundaram Ganesh
Published: February 2020

The increasing adoption of Atomic Layer Deposition (ALD) to grow thin films that take advantage of its salient properties such as conformality, uniformity, and stoichiometric control, has paved the way for its use in a number of emerging applications. Among these, the area of life sciences can potentially benefit from the use of ALD. In this paper we will examine an in-vitro case study of the use of ALD as a means of enhancing osteoblast functions, and simultaneously inhibiting microbial growth on the in-body implant materials, Ti, and PEEK.

Figure 1
(Invited) Atomic Layer Deposition of Tungsten-Rich Tungsten Carbide Films Using WCl6 and AlH2(tBuNCH2CH2NMe2) as Precursors
Authors: Blakeney Kyle J. , Ward Cassandra L. , Winter Charles H.
Published: February 2020

Atomic layer deposition (ALD) is a thin film deposition procedure where growth occurs in a layer-by-layer fashion. Growth of a binary material AB occurs first by passing a gaseous stream of a precursor containing element A over the substrate, to afford a monolayer of the precursor on the surface. Then, an inert gas purge is carried out to remove excess precursor and any reaction products. Next, a gaseous stream of a precursor containing element B is passed over the substrate. This precursor reacts with the monolayer on the surface containing element A to afford the desired material AB. Finally, a second inert gas purge is conducted to remove any excess precursor and reaction products. These four steps constitute a growth cycle. A key feature of ALD is its self-limiting nature, in which the precursor containing element A reacts with surface reactive sites until they are all consumed. At this point, growth ceases, to afford a monolayer of the precursor on the substrate surface. Self-limiting growth gives excellent conformal coverage of high aspect ratio features because the growth is controlled by surface reactive sites, and also allows sub-nanometer control of film thicknesses by adjusting the number of growth cycles. The success of ALD is directly related to the chemical precursors that are used to deliver the desired elements for a given material. ALD precursors must combine good volatility, thermal stability at the deposition temperature, as well as high reactivity toward a second precursor to afford the desired material. The reaction products must be volatile so that they are not incorporated into the growing film. Moreover, chemical precursors must have chemical reaction paths built into them so that the desired materials are obtained. These properties are difficult to incorporate into molecules, and lack of appropriate precursors represents a major bottleneck for the wider applications of ALD. This tutorial will review ALD precursors that have been reported for a variety of materials. Emphasis will be focused on obtaining volatility, high thermal stability, and high reactivity toward a second precursor. Examples will be chosen where chemical reactivity is designed into the precursors to obtain desired materials with high purities. Difficult current challenges in ALD include design of precursors for the growth of electropositive element films, integration of appropriate ALD precursor chemistry into manufacturing processes, and the possibility of precursor design to achieve inherent area-selective deposition. Additional future challenges related to ALD precursors and chemistry encompass the emerging atomic layer etching (ALE) and atomic layer clean (ALC) techniques. The importance of precursors and chemistry in future ALD, ALE, and ALC processes will be highlighted.
(Invited) Atomic/Molecular Layer Deposition for Thin-Film Lithium-Ion Batteries
Authors: Nisula Mikko
Published: February 2020

All-solid-state thin-film batteries are seen as viable technologies for powering a wide variety of miniature electronic devices, for instance microelectronics, medical implants, and radio-frequency identification tags, due to their safety, and flexibility in size and design. In order to increase the energy density while preserving the power density of the cells, increasing the effective surface area through microstructuring of the substrate is seen as a promising option. This concept of all-solid-state 3D-microbattery places an apparent need for a thin-film deposition method capable of manufacturing the electrode and electrolyte materials on high aspect ratio substrates; a formidable challenge given the limitations of the currently used thin-film deposition methods. A strong candidate for the task is the atomic layer deposition (ALD) technique, which is based on sequential surface reactions of gaseous precursors. The surface saturation limited growth results in excellent conformality over complex surface features. As the basic research on new ALD processes for Li-containing thin films is only in early stage, the true impact of the ALD technique in the Li-ion battery field is yet to be demonstrated.

This talk focuses on the use of ALD on depositing lithium-containing materials and on the aspects of manufacturing an all-ALD thin-film battery. As the all-solid-state thin-film layout enables unconventional approaches, a special emphasis is placed on fully organic electrode materials. Conjugated carbonyls are a promising group of redox active materials that in conventional bulk-format batteries suffer from solubility issues as well as from their inherently poor electronic conductivity. Here, the all-solid-state thin-film setup should mitigate both issues allowing for the full utilization of their perceived high redox reaction kinetics. The deposition of both positive and negative electrode materials is demonstrated by utilizing the combined atomic/molecular layer deposition (ALD/MLD) technique. In comparison to the conventional inorganic materials, this approach allows for simple, binary deposition processes, low deposition temperatures, and environmentally benign constituents. As well as enabling ultrafast redox kinetics, the thin-film approach might provide new information on the conduction mechanisms of the conjugated carbonyl based materials.
(Invited) Design and Modeling of Sigesn Lasers: From Modeling Experiments to Future Device Concepts
Authors: Witzens Jeremy , Marzban Bahareh , Stange Daniela , von den Driesch Nils , Buca Dan , Ikonic Zoran
Published: February 2020

We will present modeling of experimentally demonstrated SiGeSn multi-quantum well lasers. In particular, the impact of radiative recombination lifetime reduction in multi-quantum wells as well as temperature dependent L-valley electron concentrations will be shown to yield adequate modeling of these devices. Models will be further extrapolated to yield performance requirements for electrically pumped and room temperature lasing operation.
(Invited) Hybrid III-V/Si CMOS Technology Platform: From Materials for Logic to Integrated RF and Photonics
Authors: Czornomaz Lukas
Published: February 2020

In the past few years, tremendous progress has been achieved in the integration of III-V compound semiconductors on a Si CMOS platform as high-mobility channel materials are foreseen as potential candidates to replace Si channels in advanced CMOS technology nodes. Beyond CMOS scaling, the integration of III-V materials and devices on a Si CMOS platform enables bringing their traditional enhanced functionalities to the chip level: high-speed low-noise RF as well as lasers and sensitive photodetectors.

In this presentation, we will review the technologies that we developed to monolithically integrate III-V materials on Si by direct epitaxy in empty oxide cavities or by direct wafer bonding. We will show that record logic n-MOSFET performance can be achieved for ultra-scaled gate lengths (Lg = 13nm), that hybrid III-V/Si(Ge) CMOS functionality can be obtained (inverters, 6T-SRAMs). We will then highlight how 3D monolithic integration enables seamless integration of III-V functionalities on top of Si CMOS front-end for logic as well as for RF and Photonics.
IR-Photodetector Fabrication on Suspended Gesn Thin Layers
Authors: Abedin Ahmad , Garidis Konstantinos , Hellström Per-Erik , Ostling Mikael
Published: February 2020

The energy bandgap (Eg) of Ge effectively shifts toward lower energies by alloying with Sn atoms. Strain-relaxed (SR) GeSn layers with more than 8% Sn content assumes a direct bandgap and can be potentially used for highly-sensitive photodetectors for the short-wavelength infrared (SWIR) region (Eg<0.6 eV). However, the epitaxial growth of SR GeSn alloys with high crystalline quality is challenging due to the large lattice mismatch with both Si and SR Ge [1]. One method for fabricating SR GeSn is based on the growth of compressively strained GeSn layers on SR Ge and releasing the strain by selective Ge under-etching [2]. In this study, a suspended IR-photodetector was fabricated using strain-relaxed Ge0.9Sn0.1 layer through microstructuring and Ge under-etching.

The GeSn layers were grown on a Ge-buffered Si wafer [3] in a reduced pressure chemical vapor deposition tool using digermane and tin tetrachloride as Ge and Sn precursors. Two batches of detectors were fabricated; one based on GeSn on Ge and the other one based on suspended GeSn layers. Photolithography and ICP dry etching were used for patterning the detectors and the Ge underneath were removed by anisotropic selective etching using CF4 gas. XRD and RBS measurements indicate Sn contents of more than 10% without any Sn out diffusion. Raman spectroscopy shows the strain relaxation through Ge under-etching and layer release. The temperature dependence dependent photoluminescence spectra shown in Fig. 1 is in accordance with a direct band gap transitions of the GeSn layers around 0.5 eV. The effects of layer suspension on the absorption spectra and the photo response of the detectors will be discussed in the presentation.

Fig. 1) Temperature dependence photoluminescence spectra of GeSn layer with 12% Sn content

Acknowledgements:

This work was supported by the Swedish Foundation for Strategic Research (SSF) and Vetenskapsrådet (VR).

References:

[1] S. Wirths, R. Geiger, N. von den Driesch, G. Mussler, T. Stoica, S. Mantl, Z. Ikonic, M. Luysberg, S. Chiussi, J.M.Hartmann, H. Sigg, J. Faist, D. Buca & D. Grützmacher, Nature Photonics volume 9, pages 88–92 (2015).

[2] S. Gupta, R. Chen, Y. Huang, Y. Kim, E. Sanchez, J. S. Harris, and K. C. Saraswat, Nano Letters 13 (8), 3783-3790 (2013).

[3] A. Abedin, A. Asadollahi, K. Garidis, P.-E. Hellström and M. Östling, ECS Trans. volume 75, issue 8, 615-621 (2016).

Figure 1
Improving the Performance of the Optical Antenna for Integrated LIDAR with Optical Phased Arrays through High Contrast Grating Structure on SOI Substrate
Authors: Wang Pengfei , Li Zhaosong , Yu Hongyan , Li Yajie , Tang Qiang , Zhao Wu , Zhou Xuliang , Chen Weixi , Zhang Yejin , Pan Jiaoqing
Published: February 2020

With the development of automatic driving and remote sensing technology, light detection and ranging (LIDAR) has attracted more attentions. The optical phased arrays in silicon photonics have became one of the major solutions of LIDAR due to its low material cost, high integration, and compatibility with CMOS technology. However, most of the optical antennas used by LIDAR are directly etched second-order gratings on the array waveguides, which makes the emission efficiency very low, and a large part of the energy is wasted by the side lobes and grating lobes. Therefore, improving the antenna emission efficiency and its energy utilization has become the key solution to improve the performance of phased-array LIDAR systems.

In this paper, a novel optical antenna for integrated LIDAR with optical phased arrays is proposed and simulated. The high contrast grating (HCG) structure is used to achieve extremely efficient emission. The basic structure of the optical antenna consists of a 220nm Si plane waveguide at the top-Si layer of SOI substrate, a 110nm SiO2 gap layer, and a 463nm Polysilicon layer. The HCG period is 1.228μm and duty cycle is 0.388, and it is etched at the Polysilicon layer.

The proposed optical antenna has improved emission efficiency, energy utilization, and achievable scanning range. It is possible to increase emission efficiency significantly by the resonance properties of the HCG. 81.6% emission efficiency of the optical antenna is obtained with background suppression of 28.4 dB at 1550 nm. Moreover, the optical antenna can achieve more than 50% emission efficiency in the wavelength range of 1484 nm to 1609 nm. ±34.82°×18.99° scanning range was realized in lateral direction and longitudinal direction, respectively, by changing the phase difference between adjacent waveguides and the wavelength from 1480 nm to 1580 nm. In lateral direction, the scanning range achieved by the proposed optical antenna is 1.54 times larger than that of an arrayed waveguide grating with the same size. In longitudinal direction, the proposed optical antenna can achieve substantially the same scanning range as the arrayed waveguide grating.

Figure 1
Effect of Si/Sige Buried Gate with Strained Layers on N-Type Channel Properties
Authors: Lee Byoungseok , Song Seung-Hyun , Kim Il-Hwan , Park Jea-Gun
Published: February 2020

As the scaling down limit is approaching, the effect of structural and material specific limitations on the device characteristics was significantly increased. In terms of structure, formation of parasitic capacitors in the word line must be restricted in order to secure the sensing margin of the DRAM and the channel length must be secured for effective channel control. The buried gate is currently being applied in these two aspects. In terms of channel materials, as one of the possible candidates for mass-production, it is permissible to form strained silicon on the fully relaxed SiGe layer to improve the electron mobility. However, when growing SiGe without gradually increasing the concentration of Ge on Silicon substrate, the threading dislocation occur due to the lattice mismatch between the silicon substrate and silicon germanium layer. In this study, the process were investigated to form defect free and fully relaxed SiGe layer on silicon substrates by using hydrogen implantation and then growing strained silicon on the SiGe layer. The buried gate formed from the strained silicon surface to the top of the relaxed silicon germanium layer and the effect of strained Si and SiGe n-type channel characteristics on the device was investigated. We present a review on defect-free SiGe layer formation and device characteristics including the electron mobility of the strained Si/SiGe buried gate.
(Invited) High-Performance Optoelectronic Devices Based on Silicon Nanocrystals
Authors: Pi Xiaodong
Published: February 2020

Given the abundance and nontoxicity of silicon (Si) and their compatibility with conventional Si technologies, Si nanocrystals (NCs) hold great promise to improve existing Si-based technologies and advance the use of Si toward new fields such as wearable and biointegrable electronics. We have recently found that heavy boron (B) doping causes the surface region of Si NCs to be negatively charged. The resulting electrostatic effect enables the ready formation of stable B-doped Si-NC colloids. High-performance photodetectors and synaptic devices have been fabricated by using these colloids to take advantage of the novel optical properties (e. g., broadband absorption and localized surface plasmon resonance) of B-doped Si NCs. In addition, we have fabricated a series of high-performance near-infrared light-emitting diodes based on Si NCs by either engineering the ligands at the NC surface or incorporating functional interlayers into the device structures.
(Invited) Evaporation and Degradation Models for Prediction Long Term Behavior of Thermoelectric PbTe-Based Couples
Authors: Sadia Yatir , Ben-Ayoun Dana , Gelbstien Yaniv
Published: February 2020

Thermoelectric materials can show high performance of energy conversion. Many models predict this behavior, however in long term operation many problems arise such as degradation due to sublimation. This might mean that long term operation at high temperature needs to be modeled with real numbers representation degradation in order to predict long term efficiency. In the current research a model was developed using both the evaporation rates at the high temperatures and the material degradation at high temperature to model the long term operation of such a device. The device was modeled for 60°C cold side to 600°C hot side operation using PbTe based materials showing the differences between 0 hour degradation to 456 hour degradation. This was investigated both experimentally and theoretically. Surprisingly to the opposite nature of some of the effects only small degradation to the maximal electrical power and efficiency was observed. This shows that degradation is only a moderate effect in such devices.
Thermal Transport across a Semiconductor/Semiconductor Interface: A First-Principles-Based Approach
Authors: Maassen Jesse , Askarpour Vahid
Published: February 2020

Controlling heat flow across material heterojunctions is important for thermoelectrics and thermal management of electronic devices. A clear physical understanding of what transport mechanism dominates near an interface can help benefit technology. We present a theoretical investigation of phonon transport across a semiconductor/semiconductor interface, specifically Si/Ge, and demonstrate how inelastic scattering and non-equilibrium effects play a key role.

We treat phonon transport with the McKelvey-Shockley flux method, which is efficient, captures ballistic and non-equilibrium effects, inelastic scattering, and has shown excellent agreement with the more computationally-demanding Boltzmann equation. The Si and Ge phonon dispersions and 3-phonon scattering rates, serving as input for the transport modeling, are calculated from first-principles. The results show that, while the maximum phonon frequency in Si is nearly double that of Ge, significant heat currents are carried by the high-frequency Si phonons above the Ge cutoff. When approaching the interface, inelastic scattering redistributes energy to the phonon frequencies that can transfer elastically across the Si/Ge junction. We explain how this collective reorganization of phonons is driven by non-equilibrium effects near the interface. We also include a model for the contact resistance of an ideal interface, that depends on both phonon dispersions, which provides a lower limit for a given material combination. These results help provide clear physical insights into what controls phonon transport at semiconductor/semiconductor interfaces.
Wet Etching Method for the Electroless Ni–P Plating of Bi2-Te3 Thermoelectric Elements
Authors: Bae Sung Hwa , Son Injoon , Kim Kyung Tae
Published: February 2020

In this study, a method for electroless Ni–P plating with excellent adhesion via chemical wet etching to fabricate a Bi2Te3 thermoelectric module is proposed. The electroless Ni–P plating formed through the proposed process showed excellent adherence and did not desquamate, even under heat treatment at 200 °C for 24 h. Wet etching and electroless Ni–P plating was performed on a Bi2Te3 thermoelectric module, which showed excellent bond strength at approximately 10 MPa. The surface roughness of the Bi2Te3 thermoelectric element increased largely due to wet etching, and the adherence of the Ni–P plating could be secured by means of the anchor (surface roughness) effect.
(Invited) Chemical Design for Transparent Bipolar Semiconductors
Authors: Iimura Soshi , Hosono Hideo
Published: February 2020

Transparent bipolar semiconductors (TBSCs) are in demand for transparent electronics to serve as the basis for next generation optoelectronic devices. However, the poor carrier controllability in wide-bandgap materials makes the realization of a bipolar nature difficult. Only two materials, CuInO2 and SnO, have been reported as TBSCs. To satisfy demand for the coexistence of transparency and bipolarity, we propose a design concept with three strategies; choice of early transition metals (eTM) such as Y3+ and Zr4+ for improving controllability of carrier doping, design of chemical bonds to obtain an appropriate band structure for bipolar doping, and use of a forbidden band-edge transition to retain transparency. This approach is verified through a practical examination of a candidate material, tetragonal ZrOS, which is chosen by following the criteria [1]. ZrOS exhibits an excellent controllability of the electrical conductivity (10−7 -10−2 S cm−1), p- or n-type nature with ∼10−2 S cm−1 by Y or F doping, respectively, and optically wide gap (below 10−4 cm−1 up to ∼2.5 eV). This concept provides a new kind of TBSC based on eTM ionic compounds. In this talk, we also show an interesting phenomenon of other eTM semiconductor: carrier polarity inversion via doping-induced polymorph change in LaSeF [2].

References

[1] T. Arai, S. Iimura, J. Kim, Y. Toda, S. Ueda, and H. Hosono, J. Am. Chem. Soc.
139, 17175-17180 (2017).

[2] T. Arai, S. Iimura, and H. Hosono, Chem. Matter.
30, 597-601 (2018).

Figure 1
(Invited) High-Performance Thin-Film Transistors Based on Metal Oxynitride Semiconductors
Authors: Kim Hyoung-Do , Kim Hyun-Suk
Published: February 2020

In this study, indium oxynitride (InON) semiconductor is studied by both experimental and theoretical calculations to evaluate as a channel layer for display backplane for the first time. InON thin-films were deposited by reactively RF sputtering using In metal and reactive O2, N2 gas. It is found that InON thin-film and the resulting thin-film transistor (TFT) have a superior air and illumination stability compared to In2O3 TFT and ZnON thin-films. X-ray photoelectron spectroscopy (XPS) analyses of the oxygen 1s peaks in In2O3 and InON suggest that as the nitrogen incorporated, the relative fraction oxygen vacancy bonds is significantly decreased by increasing valence band maxima (VBM). In addition, density functional theory (DFT) calculation revealed that the formation energy of InN is much lower than Zn3N2.