bluuebunny/crossref_metadata_2025 huggingface dataset:
Local State-of-Charge Inhomogeneities in Charged and Cycled High Capacity Lithium-Manganese-Rich Composite Cathodes
Authors: Nanda Jagjit , Ruther Rose Emily , Callender Andrew F , Zhou Hui
Published: February 2020

Materials for electrochemical energy storage often exhibit significant chemical and structural inhomogeneity at the particle and even sub-particle level. Understanding how these mesoscale variations in the state of charge and local phase transformations impact electrochemical performance is critical to developing improved electrode materials. Raman microscopy is an excellent technique for studying inhomogeneity and interfacial phenomena in batteries, because it can measure subtle changes in chemical composition and structure at sub-micron resolution. By monitoring changes in the spectroscopic signatures, we can infer information about ion and electron transport across interfaces and through particles. In this study we use ex situ Raman mapping to study layered-layered lithium-rich manganese-rich cathode material Li1.2Mn0.525Ni0.175Co0.1O2 (LMR-NMC) as a function of the average charge. We show that variations in the microstructure and local state of charge occur at the level of individual particles within electrodes prepared from a commercial sample. Micro-Raman mapping provides both high-resolution and large field of view, but the full potential of this technique to analyze complex electrochemical systems is rarely realized, in part due to the challenge of processing the inherently large data sets. Here we take advantage of cluster analysis and other statistical methods to directly visualize interfaces and charge inhomogeneity in cathode particles.

Acknowledgment This research at Oak Ridge National Laboratory, managed by UT Battelle, LLC, for the U.S. Department of Energy under contract DE-AC05-00OR22725, is sponsored by the Vehicle Technologies Program for the Office of Energy Efficiency and Renewable Energy.

References:

Nanda, J.; Remillard, J.; O'Neill, A.; Bernardi, D.; Ro, T.; Nietering, K. E.; Go, J. Y.; Miller, T. J., Local State-of-Charge Mapping of Lithium-Ion Battery Electrodes. Adv. Funct. Mater.
2011,
21 (17), 3282-3290.

Ruther, R. E., et al., Raman Mapping Study of Inhomogeneity in Lithium-Manganese-Rich Cathode Particles, to be submitted 2014
Digital Control of DC-DC Converters Employing Wide Band Gap (WBG) Power Devices
Authors: Guo Liping , Pozo Arribas Alejandro , Krishnamurthy Mahesh , Shenai Krishna , Wang Ju
Published: February 2020

DC-DC converters are used at the Advanced Photon Source (APS) at Argonne National Laboratory to power electromagnets. The electromagnets guide the photon beams, therefore the control system of the DC-DC converters should be highly accurate to provide minimum spatial spread of the beam. Currently the converters have all been regulated by analog control systems. An upgrade to digital control system is being evaluated to resolve the aging and obsolescence issues.

This paper describes the design and evaluation of a digital control system to regulate the output current and reduce noise coupled in the system. A digital controller is first designed based on the small signal model of the converter. Experimental data of the output current is analyzed. Digital filters are then designed to reduce the noise in the output current. The complete control system is then simulated and results are evaluated. Wide Band Gap (WBG) power devices enable the development of smaller and more durable power converters with higher performance and less power consumptions than traditional silicon devices. Performance of the digital controlled DC-DC converters using WBG power switching devices including silicon carbide (SiC) power MOSFETs and gallium nitride (GaN) power transistorswill be evaluated, in comparison with the converters using traditional silicon power switching devices.
High-Heat-Resistance Polymers for SiC Power Modules
Authors: Takahashi Akio
Published: February 2020

Power semiconductor devices are critical to CO2-reduction technology. In this study, we focus on a silicon carbide (SiC) device with a wide bandgap (WBG), which operates with low loss and high efficiency at temperatures up to 300°C. Conventional isolation/sealing technologies are unable to cope with such high operating temperatures; therefore, new advanced materials are necessary. In this report, we introduce SiC power module platforms to evaluate an alternative technology involving various encapsulating materials, bonding materials, and techniques for assembly. We attempted to produce four types of platforms, PT-1 through PT-4. Fig. 1 presents the cross section and a photograph of the platform PT-3, which was assembled from a Si insulated-gate bipolar transistor (IGBT) and a SiC diode. A simulation analysis was performed to evaluate the optimum properties of the platforms from the viewpoint of their reliabilities. The purpose of this project is to accelerate the development of high-heat-resistance materials and bonding technologies through the abovementioned evaluation platforms. We identify this project as “KAMOME-PJ (Kanagawa Advanced Module for Material Evaluation).” As a pertinent example, we report a novel polymer alloy having both high heat resistance and low thermal expansion (CTE). This alloy was prepared by melt mixing of two compounds,bismaleimide diphenyl methane (BMI) and 3,3’-(methylen-1,4-diphenylen) -bis(3,4-dihydro-2H-1,3-benzoxazine) (P-d). The resin comprising BMI 1.0 vs. P-d 0.3 exhibited superior thermal properties and processability. When cured at only 200°C for 4 h, the glass transition temperature of the resulting product was above 300°C. An encapsulation material was prepared using this polymer alloy, whose properties are described in Table 1 and are compared to those of conventional epoxy materials.
Generalized Self-Assembly of Two-Dimensional Transition Metal Oxide Nanosheets on Flexible Graphene
Authors: Kim Jung Ho
Published: February 2020

Two-dimensional (2D) transition metal oxide systems present exotic electronic properties and high specific surface areas, and also demonstrate promising applications ranging from electronics to energy storage. Yet, in contrast to other types of nanostructures, the question as to whether we could assemble 2D nanomaterials with an atomic thickness from molecules in a general way, which would give them some amazing properties such as those of graphene, still remains unresolved. Herein, we report a generalized and fundamental approach to molecular self-assembly synthesis of ultrathin 2D nanosheets of transition metal oxides by rationally employing lamellar reverse micelles. It is worth emphasizing that the synthesized crystallized ultrathin transition metal oxide nanosheets possess confined thickness, high specific surface area, and chemically reactive facets, so that they could have promising applications in nanostructured electronics, photonics, sensors, and energy conversion and storage devices.
Fast Responsive of Ultraviolet-Light VO2 Flexible Photodetector
Authors: Wu Jyh Ming
Published: February 2020

Vanadium dioxide (VO2) is a useful and promising material for the applications in electrical, tunable photonic crystals, field effect transistor (FET), temperature-sensing device, and optical switching device because the material possesses unique electrical and optical properties. In this work, the single crystal VO2 nanorods/microrods were grown on SiO2/Si(100) substrate at 850oC. The SiO2 layer was acted as self-catalysts. A high-resolution transmission electron microscopy (HRTEM) image indicates that the nanorods grew along the [100] axis as a single crystal. An individual VO2 microrod was bonded at its ends on a flexible polystyrene substrate as a flexible photodetector, which exhibited an excellent optical switching property for the detection of ultraviolet-light radiation. The external quantum efficiency (EQE) and detectivity are 2E^7 and 1.2E^12 Jones, respectively. The response time was 0.2 second.
Fast Sensitive Ultra-Low Power Micro Thermal Conductivity Gas Sensor
Authors: Mahdavifar Alireza , Hesketh Peter , Findlay Melvin W , Stetter Joseph R
Published: February 2020

Abstract

A miniature, ultra-low power, sensitive, microbridge-based thermal conductivity gas sensor has been developed. The batch fabrication of the sensors was realized by CMOS compatible processes and surface micromachining techniques. Doped polysilicon was used as the structural material of the suspended sensing element with critical dimension of 500 nm.

To understand the design of the sensors, a model of the suspended element was simulated in COMSOL that couples electrical and thermal physics together and includes minimal simplifications. Modeling results coincide with experimental data in predicting resistance changes. The sensor was tested with nitrogen, carbon dioxide, helium and methane.

An electronic circuit was developed to measure very fine changes in the signal output and to keep the signal to noise ratio such that ppm detection is possible, while exciting the sensor at minimal power levels. The sensor was able to detect ppm levels of helium, methane, or carbon dioxide in nitrogen at room temperature. The sensor can make a measurement in less than 2 ms consuming only 5 nJ or power per reading.

The transient as well as steady state response was investigated as potential indicator of gas thermal capacity; as thermal conductivity and thermal capacity are independent properties of a gas, this new approach may enable MicroTCD sensors to make detections in gas mixtures by thermal analysis [1].

[1]U.S. Patent 8,426,932 B2, April 23, 2013, Apparatus and Method for Microfabricated Multidimensional Sensors and Sensing Systems, Joseph R. Stetter.
Study of 1/f Noise in Graphene Based Field-Effect-Transistors
Authors: Zhang Yuegang
Published: February 2020

Novel two-dimensional semiconducting nanomaterials have attracted tremendous interest due to their unique structure and properties. Different from the traditional silicon-based semiconductor, two-dimensional nanomaterials have a thickness as thin as a single atomic layer; their electrical properties are influenced by many factors, and the mechanism of their 1/f noise becomes more complicated. In this study, two-dimensional nanomaterials, such as graphene and its nanoribbons are chosen as the channel materials of field-effect-transistors (FETs). A systematic investigation was performed on the low frequency 1/f noise behaviors in these devices under different variability factors, such as surrounding environment and device structures (including channel thickness, width and edge structure of channels). The physical mechanisms of the 1/f noise will be analyzed. This study should help us to understand the basic 1/f generation mechanism in low-dimensional nanomaterials, and to provide critical rules for better design of low-dimensional semiconducting devices.
Direct CVD Growth of High Quality Single Layer Graphene on Dielectric Substrates
Authors: Choi Hee Cheul
Published: February 2020

Many applications of graphene especially for the fabrication of electrical devices require physical placement of graphene on dielectric substrates. Several strategies developed for the graphene device fabrication include 1) mechanical exfoliation of graphene on a dielectric substrate followed by fabrication, 2) graphene growth on metal catalysts by chemical vapor deposition (CVD) process followed by transferring it onto dielectric substrates and fabrication, 3) dispersion of reduced graphene oxides (RGOs) on dielectric substrates followed by fabrication, etc. To utilize the intrinsic high charge carrier mobility of graphene, however, a direct synthesis of graphene by CVD on dielectric substrates is highly demanding. In this presentation, I will introduce our recent experimental results demonstrating successful direct growth of graphene on various dielectric substrates, such as hexagonal boron nitride (h-BN), sapphire, quartz, and amorphous SiO2/Si, thus excluding complex transfer process to secure the quality of graphene by excluding impurities that are accompanied during the transfer process. The detailed growth mechanism involved in graphene nucleation and growth propagation on various substrates will be also discussed.

References

1. Kim, H.; Son, Y.; Park, C.; Cho, J.; Choi, H. C. Angew. Chem. Int. Ed.
2013, 52, 5997-6001. Catalyst-free Direct Growth of a Single to a Few Layers of Graphene on a Germanium Nanowire for the Anode Material of a Lithium Battery

2. Song, H. J.; Son, M.; Park, C.; Lim, H.; Levendorf, M. P.; Tsen, A. W.; Park, J.; Choi, H. C. Nanoscale
2012, 4, 3050-3054. Large scale metal-free synthesis of graphene on sapphire and transfer-free device fabrication.

3. Son, M.; Lim, H.; Hong, M.; Choi, H. C. Nanoscale,
2011, 3, 3089-3093. Direct Growth of Graphene Pad on Exfoliated Hexagonal Boron Nitride Surface.
Pushing the Limits of Plasmonic Nanoantenna Design Using New Materials and Nanofabrication Tools
Authors: Muskens Otto L.
Published: February 2020

Plasmonic nanoantennas are of interest for their capacity of controlling light on the nanoscale [1]. In particular, precise control of plasmonic near-field interactions on sub-nanometer scales is of interest for achieving strongly enhanced local fields as well as for exploring the fundamental limits of nonlocal and quantum plasmonic effect [2]. Such applications require pushing the limits of nanofabrication to new levels of precision and control.

Helium ion microscopy (HIM) is a surface imaging technique which involves scanning a helium ion beam across a sample surface and forming an image from secondary electron emission which is similar to an SEM. The larger mass and therefore smaller de Broglie wavelength of a helium ion compared to that of an electron enables the HIM to focus the charged beam to a smaller spot on a sample. The latest commercially available version of the HIM are rated at an edge resolution of 0.35nm[3]. The helium ion microscope is also a patterning tool which can be used to pattern resist like electron beam lithography or can be used for direct writing on a substrate like a focused ion beam.

In our recent work, we have demonstrated the ultrafine control of milling partial antenna gaps and narrow conducting bridges with nanometer precision using a helium ion beam microscope (HIM) [4]. A conducting bridge of nanometer height is found sufficient to shift the antenna from the capacitive to conductive coupling regime, in agree with the circuit theory.

In addition to new fabrication tools, we are developing new materials systems to combine plasmonics in electrically and optically controlled environments. I will present recent results showing how we can use new hybrid nonlinearities to achieve tunable and reconfigurable plasmonic devices.

[1] Novotny, L.; van Hulst, N. Nat. Photonics 2011, (5) 83-90

[2] Savage, K. J.; Hawkeye, M. M.; Esteban, R.; Borisov, A. G.; Aizpurua, J.; Baumberg, J. J. Nature 2012, (491) 574-577.

[3] Bell, D. C.; Lemme, M. C.; Stern, L. A.; Williams, J. R. and Marcus, C. M. 2009 Nanotechnology (20) 455301

[4] Wang, Y.; Abb, M.; Boden, S. A.; Aizpurua, J.; de Groot, C. H.; Muskens, O. L. Nano Lett. 2013, 13(11), 5647-5653

Figure 1 (left panel) Illustration showing analogy between radiowave antenna and plasmonic nanoantenna. Bottom: SEM image of antenna fabricated using e-beam lithography. (right panel) SEM image showing nano-gap obtained by helium ion beam milling.
Atomic-Level Tailoring Lithium-Intercalation Hosts for Stable Rechargeable Magnesium Ion Cathodes
Authors: Yao Yan
Published: February 2020

Batteries based on multivalent metal cations, such as rechargeable magnesium batteries, are promising for the pursuit of ultra-high-density energy storage which will deliver over four times higher volumetric energy densities than those of state-of-the-art lithium-ion batteries. Since multivalent cations are typically highly polarizing, they form large complex ions with solvent molecules and have strong electronic interaction with intercalation host materials, leading to inferior electrode performance. In this presentation, I will present a general method of tailoring established lithium-intercalation hosts for magnesium cations. By combining theoretical modeling, chemical engineering, and electrochemical characterization, we demonstrated that the ion intercalation and diffusion kinetics could be effectively improved by atomic-level manipulation of intercalation materials. This strategy enables a family of electrode materials for intercalation of multivalent cations, which are previously perceived as not suitable for such a purpose.
Ovonic Threshold Switching Selection Device Based on Chalcogenide ZnTe for Cross-Point ReRAM Device
Authors: Kim Youngjae , Min Yoonki , Lee Jimin , Sohn Hyunchul
Published: February 2020

Cross-point array structure has attracted increasing attention for high-density ReRAM, owing to the development of ReRAM with promising scalability. Cross-point array of only resistors(1R) cannot function because of sneak current through unselected devices, which can be reduced by integrating resistive memory elements with bidirectional nonlinear selection devices(1S1R). Namely, the high value of Kw in ON states, which is the writing current @ Vwrite / the current @ 1/2Vwrite, was required in cross-point ReRAM memory industry.

In this study, the high current density non-linear IV curve of Ovonic threshold switching(OTS) selection device based on Chalcogenide ZnTe was shown and the ALD HfO2 switching device has the linear properties of ON states and the compliance current of 100uA. In 1S1R unit cells based on ZnTe OTS selection device of low off current (< 400nA) and HfO2 switching device, excellent non-linear characteristics of ON states such as Kw of 522, Kr (reading current @Vread / current @ 1/2Vread) of 1430 and on/off ratio of 43 were shown. OTS behaviors with ZnTe film thickness, device area and annealing temperatures were investigated. Initial current during electro-forming process was decreased but OTS characteristics were not changed with increasing ZnTe thickness and decreasing device area. Initial current in electro-forming process and OTS characteristics at annealing temperature of below 200°C was not changed, but initial current and off current was rapidly increased and threshold voltage (Vth) in OTS was decreased at above 250°C because of Te diffusion in ZnTe film. To suppress the diffusion of Te atoms, the reactive N2during deposition which can improve the thermal stability of the chalcogenide glass was performed. And chemical compositions of ZnTe thin films were analyzed by Rutherford backscattering spectrometry(RBS). Also, crystallinity as a function of annealing temperature was investigated by Raman spectroscopy, X-ray diffraction (XRD) and plan-view transmission electron microscopy (TEM).
Kinetics and Structure of Nickelide Contact Formation to Ingaas Fin Channels
Authors: Chen Renjie , Dayeh Shadi A
Published: February 2020

The InGaAs high mobility channels are vowed as serious candidates for alternative channel materials for sub-10 nm technology nodes urging studies for analogous contacts to the dominant silicide contacts in the Si technology mainstream. The Ni-InGaAs (nickelide) contact technology has been demonstrated as a suitable self-aligned contact technology for InGaAs channels with record small specific contact resistivity. However, the majority studies on nickelide contact formation were conducted on planar InGaAs films and little studies focused on the contact metallurgy specific in nanoscale InGaAs nanowire or Fin channels. Here, we utilized a novel wafer bonding technique to transfer thin (50 nm) In0.53Ga0.47As layers onto SiO2/Si substrates and Si transmission electron microscopy (TEM) frames. InGaAs Fins with variable widths, lengths, and orientations were fabricated through a combination of electron-beam lithography and top-down dry etching steps, followed by Ni contact deposition. Rapid thermal annealing and in-situ TEM thermal heating cycles were conducted to react Ni with the InGaAs channel and deduce the reaction kinetics, dynamics, and resultant nickelide and interface structures. We observed sharp and abrupt nickelide-InGaAs interfaces for Fin channels narrower than 250 nm whereas for wider Fins, multiple interfaces evolve due to multiple nickelide layer nucleation event per interface. A faster reaction rate for [100] oriented Fins was observed when compared with [110] oriented ones. When a simple analytical treatment is applied to the Fin geometry, the nickelide length was found to have a square root dependence of inverse channel width and inverse channel height, in excellent agreement with experimental data. From this dependency, we extracted a surface diffusion coefficient of 1.2x10-15 ~ 2.6x10-15 m2/s at a reaction temperature of 250 °C, which is 4-5 times larger than the extracted Fin ‘body’ diffusion coefficient. These results will be contrasted with those obtained for silicide reaction with Si nanowires, and the detailed structure, interface and reaction dynamics will be discussed.
Synthesis of MoS2 Thin Film
Authors: Mun Jihun , Kim Dongbin , Shin Yonghyeon , Yun Juyoung , Kang Sangwoo , Kim Taesung
Published: February 2020

The two dimensional materials such as graphene, and thin films of transition metal dichalcogenides are became alternative and attracted for use in next generation nanoelectronic devices due to their planar nature and mechanical flexibility. Especially, graphene is promising and most widely studied two-dimensional material for use in flexible and transparent devices. Despite of all these excellent electrical properties, it is difficult to fabricate on/off and logic devices using grapheme because of zero band gap. In contrast, molybdenum disulfide (MoS2) has the band gap between 1.2 and 1.8 eV as a function of the number of layers (band gap of monolayer MoS2is 1.8eV) (K. F. Mak, et al., 2010).

Many researchers have been used various methods such as mechanical exfoliation (B. Radisavljevic, et al., 2011), sulfurization (Y. Zhan, et al., 2012), chemical vapor deposition (CVD)(Y. H. Lee, et al., 2012; Y. Shi, et al., 2012) to grow MoS2 thin film. In the case of mechanical exfoliation, excellent electrical properties were shown. However, there is limitation of mass production. CVD method is a typical method and there are many reports. However, the method for large area MoS2growth on dielectric substrate at the relatively low temperature is not reported.

In this work, we successfully have grown a few layer MoS2 thin film (Fig. 1) on a SiO2 substrate using molybdenum hexacarbonyl (Mo(CO)6) and hydrogen disulfide (H2S) by a CVD method. The large area MoS2 thin film was grown by optimization of the Mo and S precursor ratio and growth conditions such as process pressure and temperature. The properties of the films were analyzed using atomic force microscope (AFM), transmission electron microscope (TEM), and Raman spectroscopy.

References

K. F. Mak, C. Lee, J. Hone, J. Shan, and T. F. Heinz, Atomically thin MoS2: a new direct-gap semiconductor, Phys. Rev. Lett., 105, 136805 (2010).

B. Radisavljevic, A. Radenovic, J. Brivio, V. Giacometti, and A. Kis, Single-layer MoS2 transistors, nature nanotechnology, 6, 147-150 (2011).

Y. Zhan, Z. Liu, S. Najmaei, P. M. Ajayan, and J. Lou, Large-Arae Vapor-Phase Growth and Characterization of MoS2 Atomic Layers on a SiO2 substrate, small, 8, 7, 966-971 (2012).

Y. H. Lee, X. Q. Zhang, W. Zhang, M. T. Chang, C. T. Lin, K. D. Chang, Y. C. Yu, J. T. Wang, C. S. Chang, L. J. Li, and T. W. Lin, Synthesis of Large-Area MoS2 Atomic Layers with Chemical Vapor Deposition, Advanced Materials, 24, 17, 2320-2325 (2012).

Y. Ishikawa and K. Kawakami, Structure and Infrared Spectroscopy of Group 6 Transition-Metal Carbonyls in the Gas Phase: DFT Studies on M(CO)n (M = Cr, Mo, and W; n = 6, 5, 4, and 3), J. Phys. Chem. A, 111, 9940-9944 (2007)

W. K. Hofmann, Thin films of molybdenum and tungsten disulphides by metal organic chemical vapour deposition, J. Mater. Sci., 23, 11, 3981-3986 (1988)
Enhanced Energy Harvesting Scheme Utilizing Hierarchical Nanostructures
Authors: Chueh Yu-Lun
Published: February 2020

Solar energy is mainly a daytime energy source, a possible candidate for renewable energy. Energy harvesting from solar energy can be divided into two parts, namely energy harvesting from photo energy (photo-solar) and energy harvesting thermal heating from solar energy (thermal-solar). The photo-solar means that the energy harvesting is based on collection of photo energy collected by solar cell while the thermal-solar means storage of the solar energy as thermal energy by solar-thermal power plant. In this talk, hierarchical nanostructures were used to enhance the energy harvesting based on photo-solar and thermal-solar in my group. In the first part of my talk, I will report fabrication of a large area Cu(In,Ga)Se2 nanotip arrays (CIGS NTRs) by using one step Ar+ milling process without template. By controlling milling time and incident angles, the length of CIGS NTRs with adjustable tilting orientations can be precisely controlled. The CIGS NTRs have very low reflectance < 0.1 % at incident wavelengths between 300 nm to 1200 nm. Open circuit voltage and short circuit current of CIGS NTRs solar cell were measured to be ~390 mV and ~22.56 mA/cm2, yielding the filling factor and the efficiency of 59 % and 5.2 %, respectively. In contrast to CIGS thin film solar cell with efficiency of 3.2 %, the nanostructured CIGS NTRs can have efficiency enhancement of ~160 % due to the higher light absorption ability because of the nanostructure. In the secondary part of my talk, an enhanced heat capacity of modified HITEC molten salt by doping of metal NPs will be reported. We encapsulate the Tin alloy into Sn/SiOx core-shell NPs to prevent mixture with salt when operation temperature is higher than the melting point of Tin. The SiOx shell layer can protect the Sn NPs to be oxidized and maintains a melted status during the heat cycles, providing a stable leant heat value of 28.36 J/g. Besides, effective heat capacity of HITEC salt with Sn/SiOx core-shell NPs can be enhanced to be 30 % a mixture percentage of 5 wt%. The merits of this approach show a low-cost and easy way to enhance the thermal properties of current molten salt without complicated manufacturing.
High Quality Low-k Spacer Deposited at Low Temperatures
Authors: Varadarajan Bhadri N , Gong Bo
Published: February 2020

Obtaining films with lower k (< 5) while still maintaining excellent etch properties and thermal stability has been a critical requirement for future nodes. A high quality low-k spacer deposited at low temperatures has been developed. The film has a low-k with very high break-down voltage which is maintained even after a RTA at 1000C. The film shows excellent resistance to typical wet etch chemistries, while also providing very good selectivity to Silicon Oxide dring dry etch. Another key aspect of spacer integration is that it must prevent underlying substrate oxidation upon exposure to an oxidative enviroment. This feature, and also the films own resistance to oxidation has been demonstrated. Films deposited using PECVD typically show varying film composiiton and quality on side-wall of features, on account of the direcionality of the deposting species and ions in the plasma. The current film shows good step coverage along with uniform film composiiton everywhere in a feature, which is a key feature for integration.
Novel Cholesterol Sensor Based on Ultra-Low Detection Limit Hydrogen Peroxide Sensor
Authors: Chu Chia Ho , Fang Kuan Chung , Hsu Chen-Pin , Kang Yen-Wen , Fang Jung-Ying , Hsu Chia-Hsien , Huang Yu-Fen , Chen Chih-Chen , Li Sheng-Shian , Yeh J. Andrew , Yao Da-Jeng , Wang Yu-Lin
Published: February 2020

Hydrogen peroxide attracts a great interest due to its important role in food, pharmaceutical, and clinical applications. Hydrogen peroxide is also a by-product in many enzyme catalytic reactions, such as glucose oxidase, lactate oxidase, cholesterol oxidase, alcohol oxidase, urate oxidase, aldehyde oxidase, and oxalate oxidase, which are implemented to detect glucose, lactic acid, cholesterol, ethanol, urea, formaldehyde, and oxalate, respectively. These biomolecules are significant markers in many biologically metabolic reactions. In our study, we present a cholesterol sensor based on a high sensitivity hydrogen peroxide sensor with ultra-low detection limit. The sensor can directly test the sample and only need very small amount of sample. And because of the simple structural design and fabrication, the sensor can be used as a cheap, efficient, and portable sensor system.

The HRP-modified resistive sensors based on n-alkylated polyaniline(PANI) detect hydrogen peroxide in solution with very high sensitivity, ultra-low limit, and short response time. The sensitivity is higher than that of other sensing methods, such as electrochemical sensors or transistor sensors. The detection limit of PANI sensor is 0.7 nM. It is three orders smaller than that of other common methods with detection limit around 1 μM. To the best of our knowledge, it is the lowest detection limit that has ever been reported. And we combine the hydrogen peroxide sensor with cholesterol oxidase to build up the cholesterol sensor.

In our study, the PANI layer and gold electrodes were deposited on silicon nitride substrate, and the PANI was applied to fabricate a thin film between two electrodes. Then the PANI layer was sultonated by propane sultone and modified with HRP. After that, the device was combined with dialysis membrane which was modified with cholesterol oxidase. During the measurement, the sensor was operated at 100mV and different concentrations of cholesterol PBS solutions (pH=7.0) were dropped on it. The cholesterol reacted with the cholesterol oxidase and created hydrogen peroxide on the PANI thin film (Figure 1).

The current change was measured when the hydrogen peroxide reacted with the HRP immobilized PANI thin film. According to regular cholesterol level in human blood, we tested the cholesterol solution from 100 mg/dl to 400 mg/dl ,and we get a very good linear result (Figure 2).

In summary, the cholesterol sensor can provide a more exact cholesterol concentration detection. The simple process for the sensor fabrication also allows the sensor to be cheap, disposable and combinable with other sensors to build up sensing system.

This work was partially supported by National Science Council grant (No.99B20495A & 101-2221-E-007-102-MY3) and by the research grant (100N2049E1) at National Tsing Hua University.
CMOS Inverters and P-N Junction Diodes Based on Transition Metal Dichalcogenide Monolayers
Authors: Takenobu Taishi
Published: February 2020

The atomically thickness and emerging large bandgap of two dimensional transition metal dichalcogenides (TMDCs) offer a high degree of electrostatic control than those of bulk forms, which provide potential applications to electronics and optoelectronics. Recent progresses of exfoliated-TMDC-based n-type or p-type transistors allow widespread device applications such as circuits, diodes and sensors [1]. However, limited sample size and efficient carrier doping system are still remained, which consequently hamper the practical utility of TMDCs for complementary devices. Towards further advances, establishing scalable preparation techniques of various TMDCs and controlling their electronic properties are highly required. One of the most powerful methods to modulate the carrier density of semiconductors is electrostatic doping by using electrolyte to form electric double layer [2]. The huge specific capacitance of electric double layer transistors (EDLTs) enables the strong depletion of donor carriers and the continuous band filling, resulting in tuning material polarities.

In this study, we fabricated ion-gel-gated EDLTs using large-area TMDC monolayers, MoS2, MoSe2 and WSe2, grown by chemical vapor deposition [3-6]. The Fermi level of TMDCs can be continuously shifted by applying gate voltage, and we can induce both hole and electron transport in these devices. The hole mobility of WSe2 can be enhanced up to 90 cm2/Vs at high carrier density of 1014 cm-2, whereas the MoS2 showed electron mobility of 60 cm2/Vs. By combining MoS2 and WSe2, we demonstrated complementary logic inverters, which yielded extremely high voltage gain of 110 that is the highest value in atomically thin 2D materials. We also introduce unique techniques to form stable pn junctions in ambipolar TMDC EDLTs and investigate its optoelectronic properties.

[1] Q. H. Wang, et al., Nat. Nanotechnol. 7, 699 (2012).

[2] J. T. Ye, et al., Science. 338, 1193 (2012).

[3] J. Pu, L.-J. Li, T. Takenobu, et al., Nano Lett. 12, 4013 (2012).

[4] J.-K. Huang, T. Takenobu, L.-J. Li, et al., ACS Nano. 8, 923 (2014).

[5] J. Pu, L.-J. Li, T. Takenobu, et al., Appl. Phys. Lett., 103, 23505 (2013).

[6] J. Pu, L.-J. Li and T. Takenobu, Phys. Chem. Chem. Phys., 10.1039/C3CP55270E (2014).
Optical Properties and Defect Formation in Gallium Phosphide/Gallium Nitrogen Phosphide Core/Shell Nanowires
Authors: Dobrovolsky A. , Stehr J E , Kuang Y J , Sukrittanon S , Tu C W , Chen W M , Buyanova I A
Published: February 2020

III-V semiconductor nanowires (NWs) have recently attracted increasing attention due to their potential applications in optoelectronic and photonic devices. Among all III-V compounds, GaP-based materials have the smallest lattice mismatch to Si are, therefore, among the best candidates for growth of III-V core/shell NWs on silicon. Adding a small amount of N in GaP allows one to further minimize this mismatch and also leads to transformation of the band gap character from an indirect one in GaP to a direct-like one in the GaNP alloys, leading to improvements in efficiency of light emission.

In this work we evaluate radiative efficiency of novel GaP/GaNP core/shell NWs grown on Si substrates by using comprehensive optical characterization techniques, including cw- and time-resolved photoluminescence (PL) spectroscopies and optically detected magnetic resonance (ODMR). Superior optical quality of the structures is demonstrated from the observation of intense PL emission from a single NW at room temperature (RT). This emission is concluded to originate from radiative transitions within N-related localized states, based on the results from the temperature dependent cw- and time-resolved PL studies. In spite of the high optical quality, the RT carrier lifetime in the structures is still found to be governed by non-radiative recombination processes as evident from the results of the time-resolved PL measurements. ODMR studies identified a defect complex involving a P atom at its core as a non-radiative recombination center in the GaNP shell, most likely located at the GaP/GaNP interface.
Compound Semiconductor Nanowires for Optoelectronic Device Applications
Authors: Tan Hoe
Published: February 2020

The excitement of nanowire research is due to the unique electronic and optical properties of these nanostructures. Both axial and radial heterostructure nanowires have been proposed as nano-building blocks for the next generation devices, which are expected to revolutionise our technological world. The unique properties stem from their large surface area-to-volume ratio, very high aspect ratio, and carrier and photon confinement in two dimensions. These nanowires are usually grown by the so-called vapor-liquid-solid mechanism, which relies on a metal nanoparticle to catalyze and seed the growth. An alternative technique to grow the nanowires is by selective area growth technique, where a dielectric mask is first patterned on the substrate prior to growth.

In this talk, I will present an overview of compound semiconductor nanowire research activities at The Australian National University. The optical and structural properties of binary and ternary III-V nanowires including GaAs, InGaAs, InP and GaAsSb nanowires grown by metal-organic vapour phase epitaxy will be presented. Various issues such as tapering of the nanowires, compositional non-uniformity along nanowires, crystal structure, carrier lifetime and polarization effect will be discussed. I will also present our results of III-V nanowires grown on Si substrate which are of great interests for the integration of nano-optoelectronic devices on Si platforms. Our results of enhancing the quantum efficiency of nanowires by using plasmonics are promising to improve the performance of nanowire devices. Finally, the results from our nanowire lasers and solar cells will be presented.
Solution Processed Oxide Thin Film Transistors
Authors: Avis Christophe , Jang Jin
Published: February 2020

We have developed thin-film-transistors (TFTs) manufactured by a solution processing of the gate insulators and the active material. Oxide insulators, such as aluminum oxide, hafnium oxide, or zirconium doped aluminum oxide represent a method to achieve high performance and low power consuming TFTs. Along with amorphous indium gallium zinc oxide ( a-IGZO), other oxide semiconductors have been studied. Solution processing offers the opportunity to test various materials quickly with low capital investment. We studied poly-crystalline materials, such as indium oxide (In2O3), and tin oxide (SnO2), or amorphous oxides such as indium zinc tin oxide (IZTO).

We have developed inket-printed TFTs at the maximum process temperature of 300oC. Inkjet-printed polycrystalline InOx TFTs have mobilities of 60cm2/Vs, and were used in unipolar inverters. SnOx TFTs, show a dependence on the solution concentration, and the mobility can reach ~70cm2/Vs. On the other hand, amorphous IZTO TFTs showed the highest mobility of ~100cm2/Vs by the careful control of the inkjet process.

References

C. Avis and J. Jang, J. Mater. Chem., 21, 10649-10652, 2011

C. Avis and J. Jang, Jap.
J. Appl. Phys., 2011, 50, 01BG03, 2011

C. Avis and Jin Jang, Electrochem. Solid-State Lett., 4, J9-J11, , 2011

Y. G. Kim, C. Avis and J. Jang, ECS Solid-State Lett., 1, Q23-Q25, 2012

C. Avis, Y. G. Kim, and J. Jang, J. Mater. Chem., 22, 17415–17420, 2012

Y. G. Kim, C. Avis, and J. Jang, J. Disp. Tech., accepted, 2014

Figure 1: transfer characteristics of IZTO TFT.
Flash Lamp Annealing Effect on Stability of Oxide TFT
Authors: Moon Seung Jae , Yu Kyeong Min , Jeong So Hyun , Kim Ju Yeon , Kim Byung Kuk , Kim Hyoung June , Yun Eui Jung , Bae Byung Seong
Published: February 2020

Flash-lamp annealing (FLA) of a millisecond time scale has been shown to be a promising tool in the preparation of high-quality semiconducting materials. The flash lamp anneal pulse width is so small that thermal stresses becomes small. A combined thermal and optical model has been developed to predict the substrate temperature distribution and this model is related to a structural model to compute stresses and deflections. We used flash-lamp annealing to improve the quality of oxide material for the TFT application. We investigated the flash lamp annealing to improve the stability of Oxide TFT. The IGZO (Indium Gallium Zinc Oxide) was deposited on a glass for the characterization of a single layer. And next, The Oxide TFT was fabricated on the P-type wafer with thermal SiO2 of 3000 Ǻ. The IGZO was deposited on the substrate by the RF Sputter. And then, the sample was annealed at 430 ℃ in a furnace. We have investigated Xenon (Xe) FLA effect on the stability of each IGZO single layer and Oxide TFT. We investigated the effect of the FLA as varying the power of the lamp. And also, we investigated the effect of the substrate temperature and shot numbers of the flash lamp. A metal layer for source and drain electrode was deposited after FLA by the thermal evaporation. We measured the bias stress and light illumination effect on the transfer curves. For the structural analysis, we used the Raman spectroscopy, X-ray Diffraction (XRD), X-ray Photoelectron Spectroscopy (XPS).
Single-Component White Emitting Silicate Glass Triply Activated by Ce3+/Tb3+/Mn2+ for Organic-Resin-Free White LEDs
Authors: Zhang Xuejie , Wang Jing , Su Qiang
Published: February 2020

Thermal management is still a great challenge for high-power phosphor-converted white-light-emitting diodes (pc-WLEDs) intended for future general lighting. Luminescent glass based WLEDs (LG-WLEDs) are strongly expected to be an interesting and excellent alternative approach to traditional pc-WLEDs fabricated by combining InGaN based LED chips, with phosphor and organic resin. In the past years, many efforts have been made to develop luminescent glasses for LG-WLEDs. However, some of these glasses are poor in mechanical and chemical stability, some cannot be excited effectively owing to weak f-f absorption, and others are not very suitable for UV-LED chips ascribed to their maximum excitation wavelengths in deep UV. [1]

In this paper, a series of single-component white emitting silicate SiO2–Li2O–SrO–Al2O3–K2O–P2O5: Ce3+, Tb3+, Mn2+(SLSAKP: Ce3+, Tb3+, Mn2+) glasses that simultaneously play key roles as a luminescent convertor and an encapsulating material for WLEDs were prepared via the conventional melt-quenching method. The as-synthesized SLSAKP: 0.3%Ce3+, 2.0%Tb3+, 2.0%Mn2+ glass shows good thermal stability, inconspicuous chromaticity shift, better high-temperature resistance, and higher thermal conductivity. These are rare but desirable characteristics that are not present in the phosphors used as luminescent convertor and the epoxy resin used as the encapsulating material in pc-WLEDs. Luminescent glass (LG-) WLEDs based on SLSAKP: 0.3%Ce3+, 2.0%Tb3+, 2.0%Mn2+glass and UV-COB was successfully fabricated. These results indicate that SLSAKP: Ce3+, Tb3+, Mn2+ glass may serve as a potential bifunctional white-light-emitting materialfor LG-WLEDs pumped by UV-LED chips, especially high-power UV-COB.

Fig. 1. Photographic images of the mirror-polished (left) and rough-polished (right) SLSAKP: Ce3+, Tb3+, Mn2+glasses: (a) under white-emitting fluorescent lamp; (b) under 365 nm UV lamp. (c) The conceptual and actual fabrication process

References:

Xuejie Zhang, Lin Huang, Fengjuan Pan, Mingmei Wu, Jing Wang*,Yan Chen, Qiang Su, ACS Appl. Mater. Inter. 2014, 6 (4), 2709–2717.
A Universal Approach to the Fast Discovery of New Nitride Phosphors
Authors: Xie Rong-Jun , Takeda Takashi , Funahashi Shiro , Suehiro Takayuki , Hirosaki Naoto
Published: February 2020

Discoveries of novel luminescent materials are of fundamental importance in the advancement of lighting and display technologies. Current routine methods for this purpose inevitably involve the initial preparation of a high quality single crystal or a single-phase compound, which are known as time-consuming and labor intensive one-by-one processes. In this presentation, we introduce a simple single-particle-diagnosis method for rapid discovery of totally new nitride luminescent materials, just through determining the crystal structure, composition and photoluminescence properties of a single luminescent particle. The luminescent particle was distinguished and captured directly from the synthesized powder mixture containing different crystalline phases, on the basis of its characteristic emission color and morphology. The crystal structure of the single particle was determined by a fine-focus single-crystal X-ray diffractometer, and the photoluminescence properties (i.e., luminescence spectra, thermal quenching and quantum efficiency) were measured on a single phosphor using home-built fluorescence microspectroscopy. This method has enabled us to discover new yellow and blue phosphors in the Si3N4-Ba3N2-AlN ternary system, and a additional 48 in other systems.
Emission of White Light from Doped and Undoped Oxide Nanopowders
Authors: Bilir Gokhan , Ozen Gonul , Collins John , Di Bartolo Baldassare
Published: February 2020

We have obtained white light (WL) with very high efficiency and CRI approaching the theoretical limit with an alternative approach. We report the production of a broad band (ranging from 400 to 900 nm) WL following the monochromatic infrared light (803.5 and 975 nm) excitation of both nominally un-doped and rare earth and transition metal ions-doped oxide nano-powders. Experimental results indicate that such emission feature is a nano-scale phenomenon, cannot be ascribed to an overlap of sharp emission bands in the un-doped case and, even if assisted by the dopant presence, is a host matrix-related process.The spectral distributionof the detected WL resembles very closely that of an incandescent lamp, which in turn is the most comfortable light to human eyes. Our experimental results make our WL emission very interesting at both the fundamental and the applicative level and may open the way to an alternative route with respect to incandescent lamps.
CdSe Nanorods Synthesis By Chemical Bath Deposition
Authors: Rojas Hernández Armando Gregorio , Leal Cruz Ana Lilia , Velázquez Mendoza Carlos Villa , Marquina Alicia Vera , Fuentes Roberto Gomez , Mendoza Dainet Berman , Juárez Alejandro Garcia , Zaldívar Huerta Ignacio Enrique , Garcia Delgado Luis Arturo , Piters Droog Thomas M
Published: February 2020

CdSe thin ﬁlms were prepared by a chemical bath deposition on glass substrates during the growing process at 70◦C.Nine different films were obtained depending of the conditions of growing. The optical characterization shown bandgap upper than 1.74 reported for the CdSe at ambient temperature. This is common in luminescent materials due to the size of the nanoparticles. In our case, we found nanorods of different sizes in the range of 10 nm at 60 nm depending of the growing conditions. We observed fotoluminescent peaks near to 600 and 800 nm, indicating that this thin film is good for infrared applications.
Electrodeposition of Co-Pd Alloys from Chloride Solutions
Authors: Mech Krzysztof , Zabinski Piotr , Kowalik Remigiusz
Published: February 2020

A lot of attention has been devoted to synthesis of Co-Pd alloys mainly due to their electrocatalytic properties. Catalytic properties of these alloys for a 4-electron oxygen reduction reaction (ORR) are comparable to the properties of pure platinum. They also demonstrate high resistance to methanol activity, therefore, they can be successfully used in direct methanol fuel cells (DMFC). Significantly lower costs connected with the use of the alloys for electrodes applied in fuel cells in comparison to pure platinum make them an interesting alternative. The alloys play also an important role in magnetic data storage and microelectromechanical systems. The work presents results of the tests over the synthesis of Co-Pd alloys from acid chloride electrolytes. The main aim of the tests was to identify reactions responsible for alloy formation and to determine an influence of the electrolysis parameters i.e. working electrode potential, electrolyte composition and temperature on the composition of the resulted alloy coatings. Electrochemical investigations were performed by applying cyclic voltammetry (CV) combined with Electrochemical Quartz Crystal Microbalance (EQCM). The electrolyte composition was selected based on a thermodynamic analysis and spectrophotometric tests which were described in our previous papers [1, 2]. They allowed determination of equilibrium composition of the metals complex forms and a stability analysis of the electrolyte. The alloys were synthesized within the potentials from - 0.7 V to - 1.1 V. The tests indicate a possibility of alloys synthesis already at the potential range < - 0.5 V. The alloys composition was analysed with the use of the EDS technique. The obtained alloys featured Pd content from 0.84 to 71.37 at.%.

1. Mech K, Żabiński P, Kowalik R (2013) Co-Reduction of Electrochemically Active [Co(H2O)6]2+ and [CoCl(H2O)5]+Complexes onto Gold Electrode. J Electrochem Soc 160 (6):D246 - D250

2. Mech K, Żabiński P, Kowalik R, Fitzner K (2013) Kinetics and Mechanism of [PdCl
x
(H2O)4−x
]2−x
(x = 3, 4) Complexes Electro-Reduction. J Electrochem Soc 160 (10):H770-H774