bluuebunny/crossref_metadata_2025_split huggingface dataset:
(Invited) Crystalline Oxide Semiconductor Applicable to Low-Power Consumption Edge AI
Authors: Kunitake Hitoshi , Baba Haruyuki , Okuno Naoki , Ito Yuki , Takahashi Masahiro , Jimbo Yasuhiro , Hodo Ryota , Kurokawa Yoshiyuki , Onuki Tatsuya , Sasagawa Shinya , Yamane Yasumasa , Yamazaki Shunpei 
Published: July 2021

Scaling of Si MOSFETs has proceeded based on scaling law reported by R. H. Dennard in 1974[1], and technologies scaled down to 5 nm node are currently incorporated in ICs in production. Meanwhile, according to an IEEE semiconductor roadmap[2], the 5-nm node device has a gate length of 18 nm, suggesting that scaling is reaching its limit.
FETs using crystalline oxide semiconductor (OS), especially, c-axis-aligned crystalline (CAAC)-IGZO, are highly compatible with BEOL process of CMOS because OSFETs can be fabricated at 450°C or lower. Unlike bulk Si, OSFETs can adopt a trench-gate-self-aligned (TGSA) structure[3] enabling isolation from the substrate and accommodating chip bonding technologies. Crystalline oxide semiconductor process contributes to vertical integration required in the future technology.
FETs using CAAC-IGZO is preferred to have a charge accumulation structure such as n-i(n-)-n junction (FIG. 1) in which its channel region, especially the region direct below the gate, has to be adjusted to have an i(n-)-type conductivity. Such a junction structure enables threshold voltage control and a reduction in leakage current of the FET. The leakage current of the CAAC-IGZO FET is extremely low, yA (10-24 A)/mm measured at the transistor level at 85°C, which is lower by 10 digits than that of a CMOS device[3].
A variety of applications using crystalline OS have been studied, including AI accelerators, high-resolution displays, nonvolatile memories and combination with sensors. Among them, an AI accelerator using crystalline OS has attracted attention[4]. Using crystalline OS enables memory to be placed near compute units. It can also be driven with low current; accordingly, improvement in computational efficiency is expected.
Crystalline oxide semiconductor process is a promising technology enabling both high integration and lower power consumption of ICs with CMOS devices.

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Reference
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[1] R. H. Dennard et al., “Design of Ion-Implanted MOSFET’s with Very Small Physical Dimensions,” IEEE Journal of Solid-State Circuits, vol 9, Issue 5, pp.256-268, 1974.
[2] International Roadmap for Devices and Systems (IRDS™) 2020 Edition, 2020.
[3] H. Kunitake et al., “A c -Axis-Aligned Crystalline In-Ga-Zn Oxide FET With a Gate Length of 21 nm Suitable for Memory Applications,” IEEE J-EDS, vol. 7, pp. 495-502, 2019.

Yamazaki et al., “Crystalline IGZO ceramics (crystalline oxide semiconductor)–based devices for artificial intelligence,” Ceramic Engineering & Science, vol. 1, Issue 1, pp.6-20, 2019.

[4] D. Saito et al., “IGZO-Based Compute Cell for Analog In-Memory Computing—DTCO Analysis to Enable Ultralow-Power AI at Edge,” IEEE Transactions on Electron Devices, vol. 67, Issue 11, pp.4616-4620, 2020.
FIG. 1: Electron holography analysis result of sample using crystalline OS.

Figure 1
(Invited) Memristive Devices based on Two-Dimensional Materials
Authors: Lemme Max C. 
Published: July 2021

Two-dimensional layered materials are emerging as candidates for neuromorphic switches. So far, several different phenomena have been proposed as device switching mechanisms. These include the lateral movement of ions, either in van der Waals gaps [1] or grain boundary mediated [2], phase changes in 2D materials [3], defect mediated resistive switching [4], or vertical ion movement and subsequent modulation of electronic barriers [5].
In this talk, vertically aligned molybdenum disulfide (MoS2) will be discussed as a memristive material that allows ionic transport along its van der Waals gaps. These ions contribute to the electron transport properties across the vertical device structures [6]. In addition, the motion of ions can be used to tune energy barriers at MoS2/semiconductor Schottky junctions [5]. We have identified hydroxyl (OH-) ions that likely originate from catalytic splitting of water molecules in the devices [7]. In addition, vacancies are present in the 2D films that manifest as absorbers for infrared radiation, i.e. wavelengths beyond what is expected from a semiconductor with a bandgap of approximately 1.2 eV [8], [9].
Acknowledgements
The authors acknowledge funding by the European Commission in the Horizon 2020 grant agreements 881603 (Graphene Flagship) and 829035 (QUEFORMAL), the German BMBF grant NEUROTEC (16ES1134) and the DFG projects MOSTFLEX (407080863) and ULTIMOS2 (412113712).
References
[1] X. Zhu, D. Li, X. Liang, and W. D. Lu, “Ionic modulation and ionic coupling effects in MoS 2 devices for neuromorphic computing,” Nat. Mater., vol. 18, no. 2, Art. no. 2, Feb. 2019.
[2] V. K. Sangwan et al., “Gate-tunable memristive phenomena mediated by grain boundaries in single-layer MoS2,” Nat. Nanotechnol., vol. 10, no. 5, pp. 403–406, May 2015.
[3] F. Zhang et al., “Electric-field induced structural transition in vertical MoTe 2 - and Mo 1–x W x Te 2 -based resistive memories,” Nat. Mater., vol. 18, no. 1, p. 55, Jan. 2019.
[4] S. M. Hus et al., “Observation of single-defect memristor in an MoS 2 atomic sheet,” Nat. Nanotechnol., pp. 1–5, Nov. 2020.
[5] M. Belete et al., “Nonvolatile Resistive Switching in Nanocrystalline Molybdenum Disulfide with Ion-Based Plasticity,” Adv. Electron. Mater., p. 1900892, 2020.
[6] M. Belete et al., “Dielectric Properties and Ion Transport in Layered MoS2 Grown by Vapor-Phase Sulfurization for Potential Applications in Nanoelectronics,” ACS Appl. Nano Mater., vol. 1, no. 11, pp. 6197–6204, Nov. 2018.
[7] S. Li et al., “Edge-Enriched 2D MoS2 Thin Films Grown by Chemical Vapor Deposition for Enhanced Catalytic Performance,” ACS Catal., vol. 7, no. 1, pp. 877–886, Jan. 2017.
[8] A. Bablich et al., “Few-Layer MoS2/a-Si:H Heterojunction Pin-Photodiodes for Extended Infrared Detection,” ACS Photonics, vol. 6, no. 6, pp. 1372–1378, Jun. 2019.
[9] D. S. Schneider et al., “Highly Responsive Flexible Photodetectors Based on MOVPE Grown Uniform Few-Layer MoS2,” ACS Photonics, vol. 7, no. 6, pp. 1388–1395, Jun. 2020.
(Invited) Binary Stochastic Neurons and Compound Synapses from Nano-Magnets
Authors: Appenzeller Joerg 
Published: July 2021

In this presentation I will introduce the nCORE center CAPSL’s activities towards a probabilistic spin logic for Boolean and Non-Boolean computing. While magnetic materials in storage devices are part of our electronic world since many decades and are explored more recently by the semiconductor industry for memory applications such as Spin-transfer torque magnetic random-access memory (STT-RAM), spin based devices for logic applications are still in their infancies. Mimicking a CMOS type logic with magnets requires a “Write” and a “Read” unit as well as proper input/output isolation. Based on this, a device concept in which i) charge-to-spin conversion occurs through the Giant Spin Hall Effect (GSHE) [1], ii) dipolar coupling mediates the information transfer from a magnet in the Write unit to another one in the Read unit, and iii) a magnetic tunnel junction (MTJ) is used as the Read unit was proposed in 2012 under the name charge spin logic (CSL) [2]. Next, I will explain in how far the use of low-barrier magnets cannot only help to reduce power consumption of CSL devices but introduces a conceptually new way of computing through the introduction of “tunable randomness”. This idea, that is also known as probabilistic spin logic (PSL), was introduced in 2017 [3] and uses a counterintuitive aspect of magnets, namely their capability of creating a truly random magnetic signal if low-barrier circular nano-magnets are used. In particular, I will connect PSL with activities in the realm of quantum computing as well as neural networks.
[1] L. Liu, C.-F. Pai, Y. Li, H. W. Tseng, D. C. Ralph, and R. a. Buhrman, Science 336, 555 (2012).
[2] S. Datta, S. Salahuddin, and B. Behin-Aein, Applied Physics Letters 101, 252411 (2012).
[3] K. Y. Camsari, R. Faria, B. Sutton and S. Datta. Physical Review X 7, 031014 (2017).
Characterization of InP Surfaces Perturbations after Ar+ Bombardment By Combining Electrochemistry and X-Ray Photoemission Spectroscopy
Authors: Bechu Solene , Aureau Damien , Bouttemy Muriel , Fregnaux Mathieu , Goncalves Anne-Marie , Etcheberry Arnaud 
Published: July 2021

Over the past decades, the perturbations induced by ionic bombardment on semi-conductors have been explored, raising questions such as the deepness affected inside the material. Here, we focus on one well-known semi-conductor: InP, under Ar bombardment induced by an ionic sputtering performed directly inside the X-Ray photoemission spectroscopy (XPS) chamber using an ion gun. We already proved that, after a bombardment by Ar ions, InP surfaces suffer from several perturbations, degrading the initial properties of this semi-conductor: chemical ones (oxidation degree, atomic network organization and stoichiometry) [1], but also morphological and optical ones [2]... To get a better insight on the damages induced on the surfaces of InP semi-conductors, we present a study where electrochemistry is coupled to XPS analysis. Electrochemistry is indeed a very efficient probe to detect modification of the electrical and electrochemical properties of the materials but also a quantitative tool to provide information bulk and surface properties of any electrode material.
In our approach, n- & p- type samples were investigated toward their modified electrochemical responses. We observed that, on p-type InP, after bombardment, the surface modification is evidenced by a lower dark open circuit potential compared to the one measured on pristine surface. Moreover, cyclic voltammetry performed at pH 10 shows initial cathodic features on the surface, related to an oxidized metallic In-enriched layer onto InP surface. This feature agrees with XPS analysis. By continuing the cyclic voltammetry, a more pronounced In rich overlayer formation is observed, due to specific oxidation /reduction phenomenon.[3] This behavior is very similar to the one obtained by cathodic decomposition onto InP surface. We will also explore the response of a n-type InP surface under similar conditions.
In conclusion, we will discuss how the XPS and electrochemical characterizations combination is able to provide complete and complementary diagnostic of the stoichiometry loss and its electrochemical reactivity.
[1] Aureau et al., SIA, 2018, 50 (11) 1163-1167 ; D. Aureau et al., ECS Trans., 2019, 89, 9
[2] Béchu et al., JVST B, 2019, 27, 062902
[3] Béchu et al., Electrochem. Comm., 2020, 117, 106766
Resolving Mixed Electrical-Ionic Transport at Nanometer Length Scales in Polymer Electrochemical Cells Using Color Impedance Spectroscopies
Authors: Chen Zhiting , Ratcliff Erin 
Published: July 2021

The mechanical flexibility of conductive polymer electrodes coupled with their hybrid electronic-ionic transport properties enables a wide range of technologies from biology to energy conversion, including biosensors, flow batteries, and photo-electrochemical cells. Herein, we focus on a prototypical material to better understand hybrid transport properties - poly(3-hexylthiophene) (P3HT) - which has been widely studied in organic semiconductors and photovoltaics. In solid-state studies, the electronic transport within P3HT is limited by localized states induced by disordered regions and the mechanism is described by the multiple trapping and release (MTR) model. Recent electrochemical impedance spectroscopy (EIS) results have demonstrated anomalous diffusion of ions in regioregular and regiorandom P3HT films, indicative of ionic trapping. However, EIS has been historically equated with ambiguity, as interpretation is limited to equivalent circuit models to extract chemical parameters of interest.
Herein we combine EIS and color impedance spectroscopy (CIS) to further understand the hybrid transport mechanism. Specifically, electrochemical doping of conductive polymers results in the formation of polarons – electronic free carriers that can be observed spectroscopically due to the reorganization of chemical bonds to support the radical cations. Thus, CIS allows us to combine the sensitivity of chemical phenomena attributed to optical signatures with the in operando control afforded by application of electrochemical potential. In particular, this approach allows us to resolve mixed transport properties in subpopulations (i.e. crystallites versus aggregates) that exist at nanometer length scales.
Exploring the Structure-Function-Performance Relationship of Carbon Electrodes Toward Rational Design of High-Performance Redox Flow Cells
Authors: Nourani Mahnaz , Aravamuthan Sundar Rajan , Pezeshki Alan , Goulart James , Gallaway Joshua W , Agar Ertan 
Published: July 2021

Redox flow batteries (RFBs) are a promising grid-scale energy storage technology for the integration of intermittent renewable sources, such as wind and solar, into the electrical grid due to their modularity, flexible design, and cost-effectiveness in long-duration storage [1]. Unlike traditional batteries, for RFBs, electrolytes are stored in external tanks and are circulated through the flow cell. In the flow cell, electrical energy is stored via the electrochemical reactions of the redox active species dissolved in liquid electrolytes. While this new archetype provides unique benefits, the flow-assisted nature of RFBs presents many challenging issues, including but not limited to significant transport losses due to the poor electrode and cell design, and the related low power density [2-3]. It can be hypothesized that many of these challenges are primarily related to the concept of electrolyte utilization [4]. In this regard, porous electrode is the key component, which is responsible for multiple critical functions including delivery of liquid electrolytes as well as facilitating ion/charge transfer and providing sites for electrochemical reactions [4]. Despite its importance, the required fundamental knowledge on how to systematically design effective electrodes specifically tailored for RFB applications has not received much attention [5].
In this talk, the recent efforts on establishing the structure-function-performance linkages for commercially available carbon electrodes will be presented. The results of the experiments utilizing an electrochemical protocol that combines symmetric flow cell cycling with electrochemical impedance spectroscopy (EIS) and polarization curve (PC) measurements will be discussed. The impedance data is fitted into a mathematical model, and key physicochemical properties of carbon electrodes and the correlated performance losses are quantified. Additionally, we will share our perspective on manufacturing high-performance carbon electrodes using a high-throughput screening platform.

References:

X. Ke, J. M Prahl, J. I. D. Alexander, J. S. Wainright, T. A. Zawodzisnki, R. F. Savinell, Chem. Soc. Rev., 2018, 47 (23), 8721-8743.

P. A. Garcia-Salaberri, T. C. Gokoglan, S. E. Ibanez, E. Agar, M. Vera. Processes, 2020, 8, 775.

M. Nourani, B. I. Zackin, D. C. Sabarirajan, R. Taspinar, K. Artyushkova, F. Liu, I. V. Zenyuk, E. Agar. J. Electrochem. Soc., 2019, 166 (2), A353-A363.

B. Akuzum, Y. C. Alparslan, N. C. Robinson, E. Agar, E. C. Kumbur, J. Appl. Electrochem., 2019, 49 (6), 551-561.

A. Forner-Cuenca, F. R. Brushett, Curr. Opin. Electrochem., 2019, 18, 113-122.
A Mediated Lithium-Sulfur Flow Battery
Authors: Meyerson Melissa , Small Leo 
Published: July 2021

With the growth of intermittent renewable power sources, such as solar and wind energy, there is an increasing need for inexpensive, high capacity, grid-scale energy storage. The high capacity (1675 mAh/g) and low cost (~0.1 $/kg) of sulfur make Li-S batteries an ideal candidate to fill this need. However, sulfur has poor electrical conductivity and Li-S batteries are prone to polysulfide shuttling that decreases the battery life. In an effort to address these problems, we are developing a highly-scalable mediated Li-S flow battery using a lithium metal anode, solid state Li ion conductor separator, sulfur cathode, and a redox mediator. During discharge, the Li metal is oxidized to Li+ and the redox mediator (RM) is reduced. The RM will then react with the S returning to its oxidized form and enabling the formation of Li2S without the need for electrical contact between the S and counter electrode. The oxidized RM is then reduced again, and the process is repeated until all available S has reacted. A second RM with a potential lower than that of the Li-S reaction is used to enable the charge process. Two such mediators are decamethylferrocene (2.86 V vs Li/Li+) and cobaltocene (2.06 V vs. Li/Li+), Figure 1. The flow battery design has multiple benefits. First, the use of a solid state Li ion conductor mitigates polysulfide shuttling, thereby increasing the cycle life. Second, the issue of sulfur conductivity is addressed through use of the redox mediator, where the mediator can easily diffuse through the electrolyte reaching the sulfur and eliminating the need for excess conductive carbon additives. Third, the flow battery design enables physical separation of the anode and cathode, mitigating the potential for short circuiting and thermal runaway even if the Li does puncture the solid state electrolyte. Using this cell design, we examine the role of the solvent, anion, and polysulfide concentration on Li+ transport across the solid electrolyte interphase as well as the role of the mediation potential and interactions between the polysulfide and mediator.
Sandia National Laboratories is a multi-mission laboratory managed and operated by National Technology and Engineering Solutions of Sandia, LLC., a wholly owned subsidiary of Honeywell International, Inc., for the U.S. Department of Energy’s National Nuclear Security Administration under contract DE-NA0003525.

Figure 1
(Invited) III-Nitrides for Vacuum Nanoelectronics
Authors: Pavlidis Dimitris , Bellotti Enrico , Graham Samuel , Mohammadi Saeed , Rajan Siddharth , Redwing Joan 
Published: July 2021

Vacuum Field Effect Transistors (VFETs) are explored using wide-bandgap (III-Nitrides), VFETs avoid high power consumption caused by cathode heating in thermionic emission devices and have small turn-on voltage with potential for millimeter-wave operation. Special attention is placed on emitter design, growth of high-quality materials and evaluation of thermal properties
Progress in Si- and III-V-based electronic devices allowed operation at high-frequencies extending well into the millimeter-wave range. Device performance is limited by carrier transport properties and parasitics which have been addressed using different semiconductor materials, shrinking of device dimensions and advanced design approaches, permitting in this way to achieve operation at several hundred GHz. Further performance advances continue to be reported but start reaching a limit. The advances made in nanotechnology together with the possibility of utilizing field- rather than thermionic-emission offer, however, the possibility of revisiting the principle of vacuum tubes. Nanoelectronic devices utilizing such approaches offer the possibility of operating at millimeter-wave frequencies. Materials used for their realization are semiconductors i.e. II-Nitrides that can be processed using well-developed technologies and nanofabrication techniques, providing therefore ways of shrinking dimensions in critical parts of the device such as for example the gap between the emitter and cathode.
The paper addresses device approaches for vacuum nanoelectronics using wide-bandgap i.e. III-Nitride semiconductors. The studies rely on appropriate emitter design, growth of high-quality materials and evaluation of thermal properties that can play a critical role in device performance.
AlGaN/AlN/SiC Metal-Oxide-Semiconductor Heterostructure Field-Effect Transistors with Al2O3 Gate-Oxide and Step-Graded AlGaN Channel
Authors: Lee Ching-Sung , Lin Yun-Jung , Hsu Wei-Chou , Huang Yi-Ping , You Cheng-Yang , Lee Kuan-Tin , Lee Jia-Luen , Cheng Chih-Chung , Jian-Hong Ke 
Published: July 2021

Al0.75Ga0.25N/n-AlxGa1-xN/Al0.75Ga0.25N/AlN metal-oxide-semiconductor heterostructure field-effect transistors (MOS-HFETs), grown on a SiC substrate, with step-graded Si-doped (n = 3 × 1018 cm-3) widegap AlxGa1-xN channel and Al2O3 gate-dielectric are investigated. Increased Al-compositions with x = 0.25, 0.5, and 0.75 towards the buffer were devised in the composite widegap channel. The high-k Al2O3 dielectric/passivation layer was grown by using a non-vacuum ultrasonic spray pyrolysis deposition (USPD) method. Experimental comparisons were made with respect to a conventional Schottky-gate HFET.
The epitaxial structure of the studied Al2O3-dielectric Al0.75Ga0.25N/n-AlxGa1-xN/Al0.75Ga0.25N/AlN MOS-HFET (sample A) and Schottky-gate HFET (sample B). Both devices have the identical epitaxial structure grown on a SiC substrate by using a low-pressure metal-organic chemical vapor deposition (LP-MOCVD) system. The layer structure includes an undoped AlN buffer, a 20-nm undoped Al0.75Ga0.25N barrier, a 150-nm step-graded Si-doped (n = 3 × 1018 cm-3) AlxGa1-xN channel (x = 0.25, 0.5, and 0.75), and a 20-nm undoped Al0.75Ga0.25N barrier. Standard photolithography and lift-off techniques were used for device processing. For sample B, mesa etching was performed with respect to a 100-nm thick Ni barrier by using an inductively coupled-plasma reactive ion etcher (ICP-RIE). Flow rates were tuned and set at 10 sccm and 20 sccm for the mixed etching gases of BCl3 and Cl2, respectively. The 20-nm undoped Al0.75Ga0.25N barrier was etched away before deposition of source/drain electrodes. Ti (10 nm)/Al (50 nm)/Ni (10 nm)/Au (50 nm) were evaporated. The source/drain ohmic contacts were formed by annealing the sample for 25 seconds at 900°C by using a rapid thermal annealing (RTA) system (ULVAC MILA-5000). Then, 30-nm thick Al2O3 layer was deposited on the Al0.75Ga0.25N barrier by using the USPD technique. Finally, gate electrode of Ni (100 nm)/Au (50 nm) was evaporated after gate photolithography. As for sample A, the gate electrode was formed directly on the surface of Al0.75Ga0.25N barrier without oxide deposition.
Improved device performance of the present MOS-HFET design have been obtained, including maximum drain-source current density (IDS, max
) of 130.1 A/mm at VGS
= 10 V and VDS
= 20 V, IDS
at VGS
= 0 V (IDSS0
) of 83.1 mA/mm, on/off-current ratio (Ion
/Ioff
) of 1.4 × 107, maximum extrinsic transconductance (gm, max
) of 11.8 mS/mm, two-terminal off-state gate-drain breakdown voltage (BVGD
) of -404 V, and three-terminal on-state drain-source breakdown voltage (BVDS
) of 364 V at 300 K. The present MOS-HFET design has also shown high spectral responsivity (SR) of 737 A/W under 250-nm deep-UV radiation at 300 K.