bluuebunny/crossref_metadata_2025_split huggingface dataset:
Silicides and Novel Alloys with Open Tetrahedral Framework Structures Hosting Lithium Atoms
Authors: Fässler Thomas Friedrich 
Published: February 2020

Alloys and intermetallic compounds are emerging as new generation anode materials with high lithium storage capacity [1].Due to the higher density of alloys Li insertion results in a higher energy density . Further is the operating voltage of alloy anodes well above the potential of metallic Li and there are less solvent intercalations for alloys.
It is well known that (semi)metals and alloys undergo several phase changes during the intercalation process. For example, the lithitation/delithiation process of Si is highly complex, involving crystalline-to-amorphous phase transitions and various amorphous phases. For a long time Li3.75Si (78.9 atom % Li) had been considered to be the fully lithiated state in a typical electrochemical reaction. Depending on the applied discharge voltage and the design of the Si anode amorphous Li3.75Si can undergo a transition to a crystalline but metastable phase Li15Si4. During our re-investigation of the Li-Si phase diagram we established Li4.25Si as the Li-richest phase, and found the novel high-temperature phase Li4.11Si. Further we report that the metastable Li3.75Si transforms to a stable phase through addition of Al [2].
In the course of our studies we searches for alternatives to pure silicon and have now synthesized novel framework structures consisting of boron and silicon, Zn and Sn, Zn and Ge as well as Ag and Ge which offer all tetrahedral framework structures that host Lithium atoms [3,4].
[1] W. J. Zhang, J. Power Sources 196 (2011) 13. M. N. Obrovac, L. Christensen, Electrochem. Solid-State Lett. 7 (2004) A93.
[2] M.Zeilinger, D. Benson, U. Häussermann, T. F. Fässler, Chem. Mater. 25 (2013) 1960−1967
[3] M. Zeilinger, L. van Wüllen, D. Benson, V. F. Kranak, S. Konar, T. F. Fässler, U. Häussermann, Angew. Chem. Int. Ed. 52 (2013) 5978 –5982
[4] S. Stegmaier, T. F. Fässler, Inorg. Chem. 52 (2013) 2809-2816.
A Novel Li-Battery Cathode Material: Synthesis and Characterization of Li(Mn1-xCox)BO3
Authors: Le Roux Barbara , Bourbon Carole , Colin Jean François , Lebedev Oleg , Pralong Valérie 
Published: February 2020

LiFePO4 is very attractive as positive electrode material for lithium-ion batteries especially for its safety and low cost. However, its specific capacity is limited to 170 mAh/g. LiMBO3 (M=Fe, Mn, Co) could be good alternatives to phosphates by having a higher theoretical specific capacity (>210 mAh/g) keeping the advantage of safety [1]. Moreover, borate compounds are expected to suffer from very low volume change upon cycling which is very interesting for the cycle life of the battery.
Nevertheless, the lithium intercalation potentials in borate compounds are lower than in phosphates which will limit their energy density [2]. Theoretically, LiCoBO3 is the most interesting borate compound in term of operating voltage and specific capacity; however, approaching its theoretical capacity seems difficult due to the structural/chemical instability of fully delithiated LiCoBO3 [3].
In order to have both reversible capacity and relatively high voltage, new Li(Mn1-xCox)BO3 have been explored. These materials have been synthesized for the first time by a multiple-step process. This one includes the synthesis of two intermediates essential to prevent the formation of metallic cobalt and Mn3+during the heat treatment.
Powders X-Ray diffraction patterns of Li(Mn1-xCox)BO3 and the evolution of lattice parameters with the cobalt content will be presented. TEM and neutron powder diffraction were carried out on these materials. Interestingly, ED patterns indicate that the C2/c space group previously reported for m-LiMnBO3 [4] and LiCoBO3 [5] cannot describe Li(Mn1-xCox)BO3 compounds. Neutron diffraction helps with the complete resolution of the structure and will be discussed during the presentation.
Electrochemical characterizations were also carried out on Li(Mn1-xCox)BO3 (0 ≤ x ≤ 1). Each material shows electrochemical activity, without in situ carbon coating. In order to improve performances of these compounds, an optimized synthesis has been developed and will be presented.
References:
[1] V. Legagneur et al., Solid State Ionics 139 (2001) 37
[2] D-H. Seo et al., Physical Review B 83, 205127 (2011)
[3] Y. Yamashita et al., ECS Electrochemistry Letters, 2 (8) A75-A77 (2013)
[4] O.S. Bondareva et al., Sov. Phys. Crystallogr. 23 (1978) 269
[5] Y. Piffard et al., Acta Cryst. (1998) C54, 1561-1563

Figure 1
Optical Impedance Spectroscopy - a Technique for Characterizing the Lithium Intercalation Process in a Porous Graphite Electrode
Authors: Manka Daniel , Schindler Stefan , Berg Philipp , Ivers-Tiffée Ellen 
Published: February 2020

Graphite is the most commonly used anode material in Lithium-ion batteries. It allows high energy and power densities (depending on material parameters). Lithium intercalation losses can be reduced by fine-tuning anode design. In previous literature, several electrochemical models (1-4) were proposed to better understand and simulate this process.
The challenge is to parameterize and unambiguously validate these models. This would require electrochemical investigations e.g. electrochemical impedance spectroscopy (EIS) in half cell setups under a variation of boundary conditions, namely state of charge (SOC) or temperature (1,5). However, it can be difficult to get sufficient information for parameterization. Some parameters, e.g. electrical and ionic conductivity, show similar dependencies in their physical equations.
Lithium intercalation decreases the electrode potential and changes the diffusive reflectance. This is due to SOC dependent photo-molecular interactions, e.g. intraband transitions (6). In this work we present a new optical cell setup with a Lithium ring reference electrode. This innovation allows simultaneous in-situ optical and electrical measurements. We can now observe the dynamic behavior of the macroscopic anode surface reflectance. We demonstrate the excitation by using a modulated voltage signal to measure the reflectance as a response signal. With this new measurement method, we mapped an optical impedance spectrum (OIS), revealing further information about the Lithium intercalation process.
Conventional electrochemical models usually only contain electrical measurement figures. The most appropriate model assumption for porous graphite electrodes is based on a transmission line (1,7). In this study, the transmission line model is extended so that it reproduces both the EIS and OIS measurements. It is thereby possible to investigate different model assumptions using a combined electro-optical parameterization (Fig. 1). It becomes apparent that combined electro-optical parameterization can reduce ambiguities in the electrochemical model. It will be demonstrated that the OIS is highly sensitive to changes in ionic and electronic conductivities; ergo, these parameters can be reliably determined.

Figure 1
Geometrical Magnetoresistance in Multi-Gate FDSOI Structures
Authors: Navarro Carlos , Chang Sung-Jae , Bawedin Maryline , Andrieu François , Sagnes Bruno , Cristoloveanu Sorin 
Published: February 2020

Mobility characterization is very challenging on SOI multi-gate transistors where several channels coexist and interact [1-3]. Among all mobility determination procedures, only the geometrical magnetoresistance yields accurate values free of any assumption (channel length, oxide and film thickness, doping, strain, etc).
Magnetoresistance is a direct consequence of carrier deflection by a magnetic field. When carriers do not follow the shortest path from source to drain, the channel resistance increases. The relation between the resistances obtained when the magnetic field is present or not yields:
RB = R0 ( 1 + μMR
2 B2 )
The carrier deviation by the Lorentz force is shown in Fig. 1a. The deviation is modulated by the device geometry. If the transistor is long and narrow (W/L < 1) the Hall field opposes to the Lorentz force and the magnetoresistance is weak. However, when the sample is wide and short (W/L >> 1) the Hall field is short-circuited by the end contacts and the Lorentz force is not compensated. Hence, carriers are deviated and the magnetoresistance is maximum. Fig. 2 illustrates the simulated electron mobility against the aspect ratio (W/L) for several magnetic field orientations. The magnetoresistance is much higher for normal magnetic fields (and W/L > 5) than for transversal fields as fully documented by experimental data [4].
On the other hand, in double-gate FinFETs (Fig. 1b), the magnetoresistance is high even in narrow samples (W ~ L). This surprising result was explained by the lateral gate action which cancels the Hall voltage so preventing the compensation of the Lorentz force and resulting in the magnetoresistance [4].
TCAD numerical simulations [5] were carried out to clarify the carrier deflection and magnetoresistance mobility in FinFETs. The impact of the device architecture, thicknesses, gate biasing scheme, and magnetic field orientation is documented and explained.
References
[1] S. Cristoloveanu and S. S. Li, Electrical characterization of silicon-on-insulator materials and devices, Kluwer Academic Publishers, 1995.
[2] L. Pham-Nguyen, C. Fenouillet-Beranger, A. Vandooren, T. Skotnicki, G. Ghibaudo and S. Cristoloveanu, “In-situ comparison of Si/High-K and Si/SiO2 channels properties in SOI MOSFETs,” IEEE Electron Device Letts., vol. 30 (10), pp. 1075-1077, 2004.
[3] F. Dauge, J. Pretet, S. Cristoloveanu, A. Vandooren, L. Mathew, J. Jomaah and B.-Y. Nguyen, “Coupling effects and channels separation in FinFETs,” Solid-State Electron., vol. 48, pp. 535-542, 2004.
[4] S.-J. Chang, M. Bawedin and S. Cristoloveanu, “Mobility Investigation by Geometrical Magnetoresistance in Fully Depleted MOSFETs and FinFETs,” Electron Devices, IEEE Transactions on , vol.61(6), pp.1979-1986, 2014.
[5] Synopsys TCAD, Sentaurus Workbench Advanced, Version H-2013.10, Synopsys, Inc.

Figure 1
Influence of Substrate on Hafnium Silicate Metal-Insulator-Metal Capacitors Grown by Atomic Layer Deposition
Authors: Hutchinson B J , Teodorescu V S , Negrea R , Sheehan B , Carolan P , O'Brien S , Modreanu M , Pemble M E , Povey I. M 
Published: February 2020

Metal insulator metal (MIM) capacitors are fundamental components of the electronic circuitry commonly found in many devices in areas such as analogue to digital conversion, micro-electromechanical systems, medical, automotive and memory applications [1-4]. Current MIMCAPS generally employ optimised low dielectric constant (k) materials (k~3.9 - 7) to attain the target electrical properties of high breakdown field and low current leakage. However, device scaling is limited due to the low k value of these materials and this presents a significant challenge to the future development of these technologies [5]. Many high k materials are under investigation to replace these lower k dielectrics to substantially increase the maximum capacitance density and reduce the area associated with the integration of MIM structures.
In this work we investigate the growth of hafnium silicate films by plasma assisted atomic layer deposition on a metal electrode. The hafnium silicate film was deposited using Tetrakis(dimethylamino)hafnium (TDMAHf) and Tetrakis(dimethylamino)silane (TDMASi) precursors at 250oC with a remote oxygen plasma (300 W). From HR-TEM analysis and Raman spectroscopy it has been observed that the main crystalline phase is monoclinic HfO2. This crystallographic phase appears to be templated by the underlying titanium adhesion (10 nm) layer through the platinum electrode (200 nm).
The HR TEM analysis also reveals the presence of nanoparticles, located primarily towards the lower platinum metal layer. Based on electron energy loss spectroscopy (EELS) analysis the nanoparticles are consistent with silicon oxide inclusions, located at HfO2 grain boundaries. In addition, the presence of additional phases was detected; these included a super-cell structure within the bulk and an amorphous phase. No hysteresis was observed in the capacitance voltage measurements and the material was observed to exhibit a k value of ~18.
References
[1] C. Zhu et al., IEDM Tech. Dig., 879–882 (2003).
[2] S. J. Kim et al., IEEE Elec. Dev. Lett., 25 (8), 538–540 (2006).
[3] F. El Kamel et al., Appl. Phys. Lett., 91 (17), 172 909 (2007).
[4] A. Hastings, “The Art of Analog Layout”, Prentice Hall, New Jersey, 2001.
[5] C. H. Ng et al., IEEE Elec. Dev. Lett. 24 (8), 506 (2003).
Electrochemical Transfer Doping: A Novel Phenomenon Seen in Diamond, Gallium Nitride, and Carbon Nanotubes
Authors: Chakrapani Vidhya 
Published: February 2020

Intrinsic diamond with its band gap of 5.5 eV is an extremely good insulator. However, for undoped, hydrogen-terminated diamond exposed to air, a p-type conductive surface layer appears that is mediated by adsorbates from the ambient atmosphere.1 Since its discovery, several explanations of this effect have been proposed, none has received wide acceptance and the mechanism remained controversial.
Recent studies have shown indisputably that the conductivity arises as result of electron exchange between atmospheric oxygen and diamond through an electrochemical redox reaction occurring in an adsorbed water layer:
4H+ + 4e- + O2 = 2H2O
This results in the formation of a hole accumulation layer on the surface.2,3 This novel phenomenon, referred to as “surface transfer doping” depends only on the band line up of the semiconductor with respect to the ambient. For diamond, the Fermi level is higher than the electron chemical potential of oxygen redox couple, which results in electron transfer into water layer and generation of p-type surface conductivity. See Figure 1. The electron chemical potential (Fermi energy) of the redox couple, which can be estimated from the Nernst equation.
Since water layers form spontaneously on surfaces exposed to humid air, electrochemical transfer doping is a very general phenomenon that has been unrecognized so far. Since its discovery in diamond, the effect has been observed in other technologically important materials such as in single-walled semiconducting carbon nanotubes, graphene, gallium nitride and zinc oxide.4 The process not only affects the electrical properties but also optical properties of the semiconductor. For example, in both GaN and ZnO, electron exchange between oxygen redox couple and mid-gap states results in dramatic changes in the ubiquitous yellow and green luminescence respectively. This phenomenon opens the door to novel and robust class of devices and processes.
1. M. I. Landstrass, and K. V. Ravi, Appl. Phys. Lett., 55 (1989) 975.
2. F. Maier, M. Riedel, B. Mantel, J. Ristein, L. Ley, Phys. Rev. Lett.
85, 3472 (2000)
3. V. Chakrapani, J. C. Angus, A. B. Anderson, S. D. Wolter, B. R. Stoner and G. U. Sumanasekera, Science
318, 1424 (2007)
4. V. Chakrapani, C. Pendyala, K. Kash, A. B. Anderson, M. K. Sunkara, J. C. Angus, J. Am. Chem. Soc.
130, 12944 (2008)

Figure 1
(Invited) The Effect of Thermally Induced Piezoelectricity on GaN HEMT Device Characteristics
Authors: Sengupta Jonah , McCluskey Patrick , Khanna Sumeer 
Published: February 2020

Wide bandgap semiconductor-based High Electron Mobility Transistor (HEMT) power amplifier devices are coming into widespread use in a variety of applications, including hybrid electric vehicles. These devices dissipate considerable power, which, when combined with shrinking package size, leads to high densities of heat flux. To remove this heat, novel cooling approaches are used which can create significant thermal gradients. This study will discuss these packaging and thermal management approaches focusing on the piezoelectric defect generation in AlGaN/GaN high electron mobility transistors’ (HEMTs) resulting from thermomechanical stresses produced by these thermal gradients and the effect on electrical reliability. Two different multiphysics modeling software packages were used to determine the thermal gradients in a model of a HEMT device, convert them to thermomechanical stresses and then voltage gradients, and then assess defect creation resulting from the voltage gradient. First a thermal gradient of between 30°C to 50°C was imposed across the device. For this condition, a principal stress of 0.73GN/m2 was seen in the device along with a 9V drop across the AlGaN/GaN barrier. Next, devices were probe tested at a power density of 6.9W/mm in the GaN and a baseline temperature of 120°C in the substrate. Evident drain and gate current and on-resistance degradation were observed after 30 minutes.
(Invited) Plasmonic Terahertz Detectors
Authors: Shur Michael 
Published: February 2020

We review the achieved and potential performance of plasmonic terahertz detectors implemented in III-N, III-V, Si, and graphene materials systems and operating in the overdamped and resonant regimes. Such detectors have been using single transistors and transistor arrays. They operated in a wide temperature range – from cryogenic to elevated temperatures – and in the frequency range from 0.2 THz to 5 THz with Noise Equivalent Powers as low as 1 pW/Hz1/2. The modulation frequency over 10 GHz has been achieved. The predicted modulation frequencies reach into the THz range. Each materials system (III-N, III-V, and Si) has its optimum frequency range of operation. High mobility InGaAs plasmonic HEMT detectors are expected to operate efficiently up to 10 THz and higher. For the III-N plasmonic transistors, the operation range could reach or exceed 1 or 2 THz. Si CMOS could work as efficient plasmonic THz detectors up to 1 THz or higher. The optimum channel length for each frequency range depends on the materials system. The device responsivity peaks near or slightly below the threshold voltage and is greatly enhanced by driving drain or gate currents due to the increased non-linearity (in the case of the drain current) and due to the induced phase shift (in the case of the gate current). The detection of single THz pules with plasmonic detectors has also been achieved. These THz detectors are expected to find numerous applications in sensing, imaging, wireless communications, and security systems.
Early Detection of Lung Cancer Using High Electron Mobility Transistors
Authors: Sarangadharan Indu , Chu Chia Ho , Hsu Chen-Pin , Wang Yu-Lin 
Published: February 2020

Lung cancer is the leading cause of cancer deaths in the world, among both men and women. It claims more lives each year than do colon, prostate, ovarian and breast cancers combined. Currently, diagnosis of lung cancer in stages I and II is very difficult and hence prognosis is delayed, leading to increased mortality rate. Carcinoembryonic antigen (CEA), is a common cancer biomarker and the expression of CEA above 5 ng/mL is suggestive of the presence of cancer. In this study, we utilize immunology, which is antibody/antigen reaction, with the combination of High Electron Mobility Transistor (HEMT) as the transducer, to develop a biosensor for detecting lung cancer biomarkers, electronically, as opposed to traditional ELISA techniques. HEMTs have already been demonstrated in gas, ion and biomolecule sensing purpose. When analytes accumulate on the gate area, the net charge on the HEMT surface changes. This electrical detection technique is simple, fast, and convenient. The detecting signal from the gate is amplified through the drain-source current, making the sensor very sensitive.
Figure 1 (a) and (b) show the schematic of AlGaN/GaN HEMT and the top-view of the device. To create a high quality HEMT device, a 3 μm-thick undoped GaN buffer layer and a 150 Å-thick undoped Al0.25Ga0.75N layer were deposited by metal-organic chemical vapor deposition (MOCVD) on the substrate. Mesa isolation was formed by Inductively Coupled Plasma (ICP) etching system for 28 seconds. Ti, Al, Ni and Au were deposited by Electron Beam Evaporation and were annealed at 850 °C for 45 seconds under N2 flowing to form ohmic contacts. Passivation was provided by encapsulating the device with photoresist, with only the gate region open for antibody immobilization using photolithography.
After sensor fabrication, surface functionalization is carried out by thiol binding on gold. We mixed bi-functional thio-carboxylate with the CEA antibody and let the antibody bind with the carboxyl functional group by EDC-sulfo NHS coupling reaction. Then the device is incubated in this solution for 12 hours at 4 ºC. BSA is used for surface blocking and as a protein dilution buffer. For the sensor measurement, source-drain bias is fixed at 0.5 V and the current change induced by binding of CEA was measured by applying a 0.5 V gate voltage.
Figure 1 (c) shows the total charge accumulated for various concentrations of CEA. This can be used as an index to quantify the amount of CEA present in sample as it can distinguish various protein concentrations even in the physiological blood/serum concentration (1x PBS). The change in total charge with varying concentration of CEA can thus represent sensor calibration curve. Comparing to the conventional methods, the electronic detection of CEA using HEMT has the advantages of high sensitivity and low response time. We believe this method has the potential to further the research in the field of electronic biosensors.

Figure 1