bluuebunny/crossref_metadata_2025_split huggingface dataset:
(Invited) Applying Energy Storage to Tune the Magnetism of Large-Pore Ordered Mesoporous Metal Oxide Thin Films
Authors: Brezesinski Torsten 
Published: February 2020

Polymer-templated mesostructured non-silicate oxide thin films have received much attention in the past on account of their potential for future device applications. However, despite the overall progress made in the synthesis of such materials, “complex” metal oxides are more often than not ill-defined from a structural point of view. The primary reasons are the lack of control over the hydrolysis and condensation reactions of the inorganic precursors used, and the fact that the crystallization of the nanoscale walls is difficult to control. In this talk I will describe the evaporation-induced self-assembly synthesis of cubic mesoporous La1–xCaxMnO3 (LCMO), La1–ySryMnO3 (LSMO) and LiFe5O8 (LFO) thin films using a polyisobutylene-block-poly(ethylene oxide) diblock copolymer as the structure-directing agent. Electron microscopy, GISAXS, XRD, XPS, RBS and SQUID magnetometry all show that these materials are of high quality and thermally stable to over 600 °C. More importantly, they can store charge by topotactic lithium insertion reaction (LFO) and via double-layer capacitance (LCMO/LSMO), which allows for the intriguing possibility of reversibly tuning the magnetization [1, 2]. Collectively, I will show that both approaches provide a method to exert fine control over magnetism in situ, and further might help to better understand (Faradaic) surface charge storage processes.
[1] C. Reitz, P. M. Leufke, R. Schneider, H. Hahn, T. Brezesinski, Chem. Mater. 26 (2014) 5745.
[2] C. Reitz, C. Suchomski, D. Wang, H. Hahn, T. Brezesinski, J. Mater. Chem. C 4 (2016) 8889.
Highly-Ordered Growth of Solution-Processable ZnO for Thin Film Transistors
Authors: Buckley Darragh , McNulty David , Zubialevich V.Z. , Parbrook Peter J. , O'Dwyer Colm 
Published: February 2020

Zinc oxide is an important optoelectronic material, of particular interest due to its wide band gap (Eg
~ 3.3 eV at 300 K), large exciton binding energy (~66 meV) and especially for the variety of methods by which it can be processed. Moreover, ZnO is readily able to alloy with other metals in the oxide form and has a lattice that can facilitate interstitial doping. This gives ZnO a key role in the area of optoelectronics, metal oxide thin films and thin film transistor (TFT) technologies.
We demonstrate that crystalline, epitaxial-like and highly ordered ZnO thin films can be achieved from a precursor liquid at relatively low temperature via spin-coating. The synthesised films are smooth, stoichiometric ZnO with controllable thickness. An iterative layer-by-layer coating schematic is employed to demonstrate the effects of film thickness on structure, morphology as well as the surface and internal defects. Characterisation of the crystallinity, morphology, O-vacancy formation, stoichiometry, surface roughness and thickness variation was determined through X-ray diffraction, scanning and transmission electron and atomic force microscopy, X-ray photoelectron and photoluminescence spectroscopy, and the data of multi-layered ZnO correlated to defect formation and electrical conductivity.
It is imperative that high crystal quality epitaxial-like thin films can be formed from solution processing to compete with physical deposition methods. We demonstrate that iterative spin-coating of deposited ZnO films results in a transition in crystal texture with increasing thickness (number of layers) from the [] m-plane to the [] c-plane. The films attain a c-axis preferential orientation, with no other crystalline peaks present. Results show that the film’s surface morphology was very smooth, with average rms roughness <0.15 nm. Examination of these films also shows the consistency of the surface composition and defect level while highlighting the
(Invited) Ethanol Photoreaction over Anatase TiO2(101) and Rutile TiO2(110) Single Crystals. A Combined STM and Online Mass Spectrometry
Authors: Idriss Hicham , Thornton Geoff , Harison George , Katsiev Habib , Algamdi Hamdan 
Published: February 2020

The reactions of ethanol have been investigated over anatase TiO2(101) and rutile TiO2 (110) single crystals by STM and on-line mass spectrometry to determine the adsorbate species in the dark and post UV illumination, in the presence and absence of O2 or Au nanoclusters, in order to extract initial reaction parameters under photo-excitation. On anatase (101) TiO2 single crystal the reaction rate for the photo-oxidation of ethanol to acetaldehyde is found to be strongly dependent on O2 partial pressures and surface coverage with an order of the reaction for O2 close to 0.15. Carbon-carbon bond dissociation leading to CH3 radicals in the gas phase was found to be a minor pathway, which is contrary to the case of TiO2 rutile (110) single crystal, as previously reported by our group and others. Our STM images distinguished two types of surface adsorbates upon ethanol exposure that can be attributed to its molecular and dissociative modes. Upon UV exposure at (and above) 3×10-8 mbar O2, a third species is identified as a reaction end-product, which can be tentatively attributed to acetate/formate species, in line with XPS C1s measurements. The room temperature photo-oxidation of ethanol has also been investigated over a rutile TiO2(110) single crystal by STM and on-line mass spectrometry, in the presence of O2 to determine adsorbate species remaining post UV exposure and emitted gas phase products. In addition to acetaldehyde, methyl radical was detected in the mass spectrometry resulting from the photo-fragmentation of an acetaldehyde-O complex. Formic acid species bound to Ti5c in a bi-dentate mode were identified by STM on the surface after the reaction. The effect of O2 partial pressure on the reaction selectivity demonstrated a dominance of the photo-fragmentation process with increasing pressure unlike the case of anatase TiO2(101) single crystal. In addition the effect of Au particles on the reaction of the TiO2(110 rutile has been investigated for hydrogen production under photo-irradiation in UHV conditions. It was found that particle size in the range 4 to 8 nm do not change the reaction rate yet particle density does. Detailed reaction mechanism for both reduction and oxidation reactions are addressed based on structural and kinetic information from the UHV systems and compared to those of their corresponding powder forms in liquid-solid photocatalytic reactions conditions.
(Invited) Phase Transition and Related Energy Applications of (Hf,Zr)O2 Films
Authors: Park Min Hyuk , Hwang C. S. 
Published: February 2020

A new ferroelectric phase (space group: Pca21) in (Hf,Zr)O2 thin film and doped/undoped HfO2 has been intensively studied since 2011.[1,2] The films could show large remanent polarizations (They are generally ~20 μC/cm2 and can be even larger than 40 μC/cm2 for La-doped HfO2) with extremely small film thickness (It is generally ~10 nm and can be even as thin as ~2.5 nm).[3,4] Moreover, they could endure more than 109 times of switching with the electric field of 2.5 MV/cm.[2] The Curie temperature of (Hf,Zr)O2 could be controlled by changing Zr:Hf ratio, and the (Hf,Zr)O2 films showed first-order like phase transition.[5] Interestingly, the two-step polarization switching could be observed in rather wide temperature range near room temperature for Hf0.4Zr0.6O2 film,[5] which could be observed in a very narrow temperature range for BaTiO3in a previous study.[6]
The phase transition involved with the new ferroelectric phase is believed to be highly promising for various applications such as electrostatic supercapacitor, energy harvester, and electrocaloric cooler.[7-9] The Hf0.3Zr0.7O2 thin film could store electrostatic energy up to 46 J/cm3.[7] The temperature dependent change of polarization of Hf0.2Zr0.8O2 thin film could harvest electrical energy of 11.6 J/cm3 cycle from heat using Olsen cycle.[8] This also can be used for solid state cooling based on electrocaloric effect (The adiabatic temperature change was 13.4 K) when the inverse Olsen cycle is used.[8] It was suggested that a monolithic device with aforementioned various functions can be achieved on Si substrate.[8] In 2016, the giant negative electrocaloric effect (The adiabatic temperature change was -10.8 K.) in Hf0.5Zr0.5O2 film was also reported based on the abnormal pyroelectric properties.[9] It is expected that the combination of giant positive and negative electrocaloric effect in (Hf,Zr)O2films can make the solid state cooling device more efficient.[10]
In this presentation, the fundamentals for phase transition in (Hf,Zr)O2films will be discussed based on the first-­order phase transition model involving the orthorhombic and tetragonal phases. The application of the phase transition behaviors for the various energy applications including energy storage/harvesting and solid state cooling will be presented in detail.
[1] T. Boescke et al. Appl. Phys. Lett. 99, 102903 (2011).
[2] M. H. Park et al. Adv. Mater. 27, 1811 (2015).
[3] J. Meuller et al. IEEE International Electron Devices Meeting (IEDM) (2013).
[4] A. Chernikova et al. ACS Appl. Mater. Interfaces 8, 7232 (2016).
[5] M. H. Park and H. J. Kim et al. Nanoscale 8, 13898 (2016).
[6] W. J. Merz, Phys. Rev. 91, 513–517 (1953).
[7] M. H. Park et al. Adv. Electron. Mater. 4, 1400610 (2014).
[8] M. H. Park et al. Nano Energy 12, 131 (2015).
[9] M. H. Park et al. Adv. Mater. 28, 7956 (2016).
[10] Li et al. Europhys. Lett. 102, 47004 (2013).
Study of Seed-Layer Stability on Copper Electrolytic Bath
Authors: Delbos Elise , Setoain Imanol , Frégnaux Mathieu , Gonçalves Anne-Marie , Etcheberry Arnaud 
Published: February 2020

For years, the effectiveness of the Damascene process has allowed the semiconductor industry to successfully keep the pace with the aggressive scaling of Moore’s law. However, ever increasing costs have raised the need for alternative technologies bringing advantages in terms of performance gain, time to market and cost competitiveness. Thus, 3D chip stacking technologies have now become a field of extensive research [1-2]. The today improvements are mainly devoted on the current process optimization or the development of new methods to elaborate barriers, seed-layers and fillings compatible with technological advances and the more and more aggressive via aspect-ratio [3]. Generally made in copper by CVD, PVD, ALD or electrografted technics, the seed-layer plays an important role during the via filling. Its principal criteria are to be uniform in term of thickness and continuous to ensure a good electrical contact during the electrochemical process [4]. During the filling process, the wafers and thus the seed-layer are first pre-wetted using DI water or etching solutions and then immerged in the copper bath. Traditionally an idle time is maintain before applying the current density, to favour the species exchange.
However, few studies have an interest for the reaction during this idle time and in more general consideration for the copper seed-layer stability on the copper electrolytic bath. Hence, the copper seed-layer is dissolved in the plating bath due to electrochemical reaction with the oxygen dissolved in the bath [5-7]. In this research work, the stability of the seed-layer and its dissolution rate are studied combining in-situ and ex-situ technics (figure 1). Open circuit potential versus time is an interesting approach for this study, allowing direct information on the surface modification during the idle time. Quartz microbalance measurements complete the analyses, giving direct information of weigh lost resulting from dissolution. As ex-situ characterization technics, SEM-EDS, XPS and RBS measurement were performed to characterize the surface states and the chemical composition after the idle time. Several parameters are particularly highlighted as the bath composition and its concentration and the rotation rate of the substrate.
[1] T.P. Moffat, D. Wheeler et al., IBM J. Res. Dev., 49, 19 (2005)
[2] P.M. Vereecken, R.A. Binstead, H. Deligianni, P.C. Andricacos, IBM J. Res. Dev, 49, 3 (2005)
[3] M. Datta, Electrochemical processing technologies and their impact in microelectronic packaging in Microelectronic Packaging, edited by M. Datta, T. Osaka and J.W. Schultze, CRC Press edition (2005)
[4] Part II Chip metallization in Microelectronic Packaging, edited by M. Datta, T. Osaka and J.W. Schultze, CRC Press edition (2005)
[5] R. Schumacher et al, J. Electroanal. Chem. 219 (1987) 311-3174
[6] K.Y. Electrochimica Acta, 38, 14 (1993) 2121-2127
[7] A.G. Zelinsky et al, Corrosion Science 46 (2004) 1083–1093

Figure 1
(Invited) 2D/3D Tunnel-FET: Toward Green Transistors and Sensors
Authors: Cao W. , Kang J , Banerjee Kaustav 
Published: February 2020

MOSFETs have been the workhorse of the worldwide semiconductor industry and the primary building blocks of most electronic products of everyday use since the 1970’s. However, continuous miniaturization of MOSFETs, well beyond 100 nanometers, to sustain the ever growing need for increased transistor densities has given rise to a daunting power dissipation challenge during the past decade due to increasing leakage power arising from a fundamental limitation of their turn-on characteristics. This talk will examine the genesis of this challenge, and provide an overview of our recently demonstrated atomically-thin 2D layered semiconducting channel tunnel-FET (Nature 2015) that overcomes this challenge and is a new class of transistors in which electrons move in an extremely thin interface layer between a conventional 3D semiconductor (Germanium, as the source) and a thin film of atomically layered barrier material (molybdenum disulphide or MoS2, as the channel). The materials allow the electrons that carry the signal current to be injected through quantum mechanical band-to-band tunneling.
At present, our 2D/3D heterostructure TFET is the thinnest-channel subthermionic transistor ever made and exhibits unprecedented low leakage currents, high ON/OFF ratio, 2X higher ON current (w.r.t other experimental TFETs at 0.1 V), very low average subthreshold swing (SS) over four decades of drain current, and lowers power dissipation by over 90% compared to the state-of-the-art MOSFETs. Rigorous analysis of the physics of band-tails in 2D semiconductors and their various heterostructures, accomplished in our group (IEDM 2016), support the experimentally demonstrated minimum SS values. Moreover, we have also shown that 2D-material (such as MoS2) based conventional FETs provide an excellent platform for biosensing (ACS Nano 2014). Hence, 2D-TFETs that combine the advantages of an atomically-thin channel and the unprecedented sensitivity of a tunnel-FET (APL 2012), owing to their steep turn-on characteristics, can be employed for building a revolutionary new class of ultra-low power bio/gas sensors (Physics Today, Sept 2016).
The Virtual Diode with Electrostatic Doping
Authors: Lee K. , Bawedin Maryline , Parihar M. , Park H.-J. , Cristoloveanu Sorin 
Published: February 2020

The ‘electrostatic’ doping is a fascinating feature of FD-SOI technology. In an ultrathin SOI device, the electron population induced by a positive gate bias spreads into the entire body (volume inversion or accumulation). The body behaves as an N-doped region albeit it was originally undoped. Reciprocally, negative gate bias turns the body into a P-type region. Such doping metamorphosis has been used for conceiving novel devices containing reconfigurable P-N junctions.
We investigate the virtual P-N junction constructed with electrostatic doping. The primary question is whether and to what extent it behaves as a regular diode with physical doping. Our test devices are PIN diodes with large gate underlap. The doping in the gated and ungated regions is induced by the bias on the front gate and on the back gate (ground plane), such as to emulate a fictive junction at mid-distance from anode to cathode. The devices have been processed with 28nm FDSOI technology including HKMG gate stack, 7 nm SOI film and 25 nm thick BOX.
The experimental I‒V curves look familiar to a diode but without complying with the conventional theory. First, the doping level is adjustable by the gates in a wide range, which offers the possibility to modulate the leakage current and the breakdown voltage. Second, the junction depletion region is no longer defined by the lateral field because the gate action leads to a 2D effect documented by simulations. Third, the virtual doping varies dynamically with the anode/cathode voltage. Finally, the junction position can be selected by appropriate gate biasing from the mid-body to the physical junctions. We show that this intriguing diode is very versatile and enables various applications. In particular, a unique characterization technique for carrier lifetime extraction in ultrathin films will be presented.
Recovery of Bias-Stress Ionized Igzo/SiO2 Interface States Via Cryogenic Relaxation
Authors: Mudgal Tarun , Bharadwaj Anish , Ganesh Prashant , Powell Eli , Manley Robert G. , Hirschman Karl D 
Published: February 2020

Indium gallium zinc oxide (IGZO) has been considered a potential replacement for hydrogenated amorphous silicon in TFT applications due to process compatibility and an order of magnitude improvement in electron channel mobility. However the mechanisms responsible for instability under bias-stress remain an active research topic. Silicon dioxide serving as the gate dielectric and back-channel passivation layer in bottom-gate IGZO TFTs results in high quality interfaces. Applied bias-stress conditions demonstrate a voltage shift that can be attributed to ionization and/or alteration of oxygen-related defects at these IGZO/SiO2interfaces.
Bottom-gate IGZO TFTs with SiO2 gate dielectric and passivation layers were fabricated and tested under rigorous positive bias-stress (PBS) and negative bias-stress (NBS) conditions. The devices demonstrate good stability under PBS (t > 104 s), with minor distortion in the subthreshold region and a slight characteristic left-shift from an initial pre-stress state. This PBS-shift is attributed to a change in the energy distribution of defect states at the front-channel interface. During NBS the devices exhibited a significant left-shift (ΔV ~ 1-2 V), which is attributed to the transformation of neutral oxygen vacancies to ionized donor states at the back-channel interface. This transformation appears to improve the electrical homogeneity of the back-channel interface, inferred by a suppression of DIBL-like behavior. The NBS-shift was found to be reversible over long recovery times at room temperature. The recovery time was dramatically reduced when samples were subjected to cryogenic temperature (77 K), which represents an accelerated return to the pre-stress condition. TCAD simulation provides additional support to the interpretation of bias-induced stress on IGZO TFTs.
(Invited) High-Mobility Complex Oxide Films By MBE
Authors: Stemmer Susanne , Raghavan Santosh , Schumann Timo , Shoron Omor 
Published: February 2020

Functional perovskite oxides may enable entirely new electronic device concepts, ranging from negative capacitance to charge amplification in phase change devices. A major challenge is the intrinsically poor charge carrier mobility of most perovskite oxides, typically no better than 1 - 10 cm2V-1s-1 at room temperature. Recent reports of room temperature mobilities of ~300 cm2 V-1s-1 in single crystals of La-doped BaSnO3 have therefore generated significant excitement. In addition, BaSnO3has a wide band gap (~ 3 eV), which makes it of interest as a new transparent conducting oxide and as a wide band gap semiconductor for power electronics. Furthermore, it would allow for integration of functional perovskite oxides on a lattice- and symmetry-matched, high-mobility, semiconducting channel.
Electronic devices require the growth of high-quality films with low defect densities. High-mobility BaSnO3 thin films have been challenging to grow. Molecular beam epitaxy (MBE) is a low energetic deposition technique and routinely produces the highest mobility semiconductor and functional oxide films. However, stoichiometry control in MBE of perovskite oxides can be challenging. We show that in the MBE of perovskite stannates using a Sn metal source, volatile SnO consumes all active oxygen in the growth environment, leaving behind only Sn droplets at low growth temperatures. No film growth occurs at high temperatures. We discuss a modified MBE approach, which supplies pre-oxidized SnO
x
. This technique addresses issues in the stoichiometry controls in MBE of ternary stannates related to volatile SnO formation and enables growth of epitaxial, stoichiometric BaSnO3. A second challenge is the lack of lattice-matched substrates. We discuss the effect of lattice mismatch on the growth and transport properties of BaSnO3 by comparing the properties of films grown on SrTiO3 and PrScO3 substrates. We show that the carrier mobility doubles as the lattice mismatch is reduced by a factor of two, indicating that high misfit dislocation densities are the main limiting factor in further improving carrier mobilities. We demonstrate room temperature electron mobilities of 150 cm2 V-1s-1 at carrier densities of 7×1019 cm-3 in BaSnO3 films grown on PrScO3 using the modified MBE technique. We will discuss the prospects for further improving the carrier mobilities and reducing the carrier densities.
(Invited) Investigation of Phosphorene in Electrochemical Energy Storage Devices
Authors: Koratkar Nikhil 
Published: February 2020

Among the family of atomically thin two-dimensional (2D) materials, phosphorene (a monolayer of black phosphorus) has special significance since it offers a direct band gap that lies in-between the zero gap graphene and various large band gap 2D transitional metal dichalcogenides. Phosphorene is an atomically thin sheet in which each phosphorus atom bonds with three neighboring atoms forming a puckered honeycomb structure. So far the research community has mainly focused on the electronic and opto-electronic applications of phosphorene such as logic transistors and photo-detectors. The exploration of this unique material in electrochemical energy storage is still very much in its infancy. In my talk, I will show that incorporation of few-layer nanosheets of phosphorene into a porous carbon nanofiber network (cathode matrix) can significantly improve the cycle life of Lithium-Sulfur (Li-S) batteries. After 500 continuous cycles of charge-discharge, the specific capacity of the Li-S battery with phosphorene is retained above 660 mAh g−1 with only ~0.053% capacity decay per cycle, much better than the baseline battery (without phosphorene) which shows ~0.25% capacity fade per cycle in only 200 cycles under the same test condition. First-principles density functional theory calculations indicate that this improvement is related to phosphorene’s ability to immobilize lithium polysulfides. The binding energy of various lithium polysulfides to phosphorene ranges from 1-2.5 eV, which is significantly greater than a carbon hexatom network (~0.5 eV). Our results also indicate that the presence of phosphorene lowers the polarization, accelerates the redox reaction and improves sulfur utilization in the battery. Such work indicates the promise of phosphorene and will give further impetus to the research community to explore the fundamental science and applications of phosphorene in the context of electrochemical energy storage.