bluuebunny/crossref_metadata_2025_split huggingface dataset:
Investigation of SiC Polytypes for PVT Process Control Using Ultraviolet Fluorescence Technique
Authors: Jeong Seong Min , Yoon Ji-Young , Choi Hyoung-Seuk , Byeon Dae-Seop , Jung Eunjin , Kwon Yong Jin , Kim Jungyu , Kim Younghee , Seo Won Seon , Lee Myung Hyun 
Published: February 2020

Silicon carbide (SiC) is a wide-bandgap semiconductor with high saturation velocity and thermal conductivity. So, It is well-known as a potential substrate for high-power, high-temperature and high-frequency devices. Commercial 4H- and 6H-SiC wafers are commonly grown by physical vapor transport (PVT) method and some emerging techniques such as high temperature chemical vapor deposition (HTCVD) and top seeded solution growth (TSSG) is still under developing.
Because SiC has large number of polytypes determined by their stacking order during crystal growth, the polytype inclusion has been a common issue during SiC growth, especially at the early stage of development of new process or new equipments. When photon is incident on the surface of SiC crystal and the energy of photon is larger than the band gap of SiC (2.9 ~ 3.3eV in the UV range), the photon excites the electron in the valence band to the conduction band. Excited electron goes to the lower states emitting heat and relaxes to the valence band emitting photon that has longer wavelength that the incident light. The phenomena that wavelength is shifted to the longer wavelength by material is called fluorescence. Thus, polytypes with different energy band gap can be identified with the fluorescence color if UV ray is incident ray with sufficient energy for excite electron in the valence band.
In this study, we observed the fluorescent color of various SiC polytypes with a lab-developed UV fluorescence equipment. The UV fluorescence is non-destructive technique to characterize the grown sample without any further sample preparations, so that this technique is applied to develop a new PVT process in the early stages. SIMS, Photoluminescence and Raman spectroscopy were used for identify the fluorescence color considering polytypes, dopants and defects. Stress mapping using high resolution X-ray diffraction and Raman spectroscopy were used for analyzing the effect of polytype formation on residual stress distribution on the grown crystal. Glazing-incidence X-ray topography using white beam were conducted for evaluating the grown SiC crystals at Pohang accelerator laboratory.
(Invited) Why Are Nanowire BioFETs More Sensitive than Their Large-Scale Counterparts?
Authors: Shoorideh Kaveh , Chui Chi On 
Published: February 2020

FET-based biosensors (bioFETs) are transistors that can detect and quantify charged molecules, such as DNA, RNA, or proteins, in an aqueous environment. The detection is via the electric charge that such molecules intrinsically carry in aqueous environments, so extra labeling molecules and techniques are not required. As such, these devices hold promise for a rapid, portable, and cheap method for measuring biomolecule concentrations in liquid human samples at very low concentrations.
BioFETs have been around for a long time, but they really captured the attention of the scientific community in 2001, when a nanowire-shaped bioFET demonstrated protein detection at concentrations much lower than what had been demonstrated before. The invention was hailed as a breakthrough, and the extreme sensitivity of the nanowire bioFET compared to its non-nanoscale ancestors was attributed to the high surface-area-to volume ratio of the nanowire structure.
The surface-area-to-volume ratio argument has been put into very simple mathematical terms using basic electrostatic arguments. These arguments show that nanowire bioFETs become ever more sensitive as the size of the nanowire shrinks. This result has been widely accepted by the scientific community. Almost every new paper published on the topic cites the surface-area-to-volume ratio argument in its introduction as the justification for using a bioFET with a nanowire structure.
These mathematical equations fail to take into account the effect of Debye screening, which is detrimental to sensor performance because it screens the electric field emanating from the charged biomolecules. Using basic electrostatic arguments, and including the effect of Debye screening, we prove that when a nanowire is surrounded from all sides by the aqueous medium, its sensitivity actually decreases as its diameter shrinks, even while its surface-area-to-volume ratio increases. This result effectively disproves the justification given for the enhanced sensitivity of the nanowires.
We go a bit further, and use simulations to study nanowires that are placed on insulating substrates, as is more commonly encountered in experimental works. We show that within the concave corners created between the sides of the nanowire and the surface on which it sits, Debye screening is significantly weakened, so much so that the majority of the response of the nanowire bioFET is due to the detection of electric charges in these corners. In our simulations, the sensitivity of nanowires decreases with decreasing size when the nanowire is suspended in, and surrounded by, the aqueous medium, in agreement with analytical calculations. However, the trend is reversed for nanowires placed on insulating substrates, in qualitative agreement with experimental results reported in the literature.
These results disprove the surface-area-to-volume ratio argument as the cause of the enhanced sensitivity seen in nanowire bioFETs, and suggest that the concave corners are responsible instead.
(Invited) Oxide Neuron Transistor for High-Performance Biochemical Sensors
Authors: Wan Qing , Liu Ning , Shi Yi 
Published: February 2020

Synergic integration of presynaptic inputs from the dendrites plays an important role for sensory information process and cognitive computation, and the idea of building bio-inspired solid-state devices has been around for decades. In 1992, Shibata et al proposed the Si-based neuron transistors with multiple input gates that are capacitively coupled to a floating gate . The “on” or “off” state of the neuron transistors depends on the integrated effect of the multiple input gates. One of the unique features of the neuron transistors is the ultralow power dissipation during the calculation due to the gate-level sum operation in a voltage mode. From then on, Si-based neuron transistors have attracted much attention for chemical and biological detection due to the easy adjustment of threshold voltage. But, up to now, electrolyte-gated neuron transistors with amorphous oxide channel layers for biochemical sensing applications are not reported. For portable applications, low-voltage operation is preferred. Electrolyte gated electric-double-layer (EDL) transistors can act as potential candidates with a low operation voltage due to the strong EDL modulation at the electrolyte/channel interface. Recently, oxide-based EDL transistors gated by solid-state inorganic electrolytes were proposed by our group. At the same time, artificial synapses and neuron transistors with low power consumption and fundamental biological functions were mimicked in individual device. The sensitivity of a standard ion-sensitive field-effect transistor is limited to be 59.2 mV/pH (Nernst limit) at room temperature. Here, inspired by the dendritic integration and spiking operation of a biological neuron, oxide-based neuron transistors with multiple input gates are fabricated on flexible plastic substrates for pH sensor applications. When the neuron transistor sensor is operated in a quasi-static dual-gate synergic sensing mode, it shows a high pH sensitivity of ~105 mV/pH, which is higher than the Nernst limit. Our results also demonstrate that single-spike dynamic mode can remarkably improve pH sensitivity and reduce response/recover time and power consumption. At last, we find that appropriate depression applied on the sensing gate electrode can further enhance the pH sensitivity and reduce the power consumption. Our flexible neuron transistors provide a new-concept sensory platform for biochemical detection with high sensitivity, rapid response and ultralow power consumption.
(Invited) A Soft Approach to Electronics: From Stretchable Systems to 3D Structures
Authors: Xu Sheng 
Published: February 2020

Wearable device that matches the soft human body represents an important trend for bio-integration; the resulting search for pliable electronic materials calls for strategies to bridge the gap between hard and soft – among which advanced engineering of the geometry and architecture of materials presents unique opportunities. A prominent example of materials engineering is that the compressive straining of an elastic substrate can be used to fabricate previously inaccessible classes of 3D structures in monocrystalline materials. Conversely, rationally designed 2D geometries can buckle to form 3D layouts to accommodate tensile strain, resulting in unprecedented stretchability. This enables a series of device possibilities in stretchable electronics, including lithium ion batteries with record stretchability and integrated soft health monitoring systems.
Interpenetrated Graphene/WSe2 Lateral Heterostructures for Barrierless Ohmic-Contacted p-FETs
Authors: Tang Hao-Ling , Chiu Ming-Hui , Tseng Chien-Chih , Lien Chen-Hsin , Li Lain-Jong 
Published: February 2020

High contact resistance between TMDs and metals has been identified as an outstanding issue. TMDs tend to form a substantial Schottky barrier (SB) with commonly used metals. Air-stable graphene electrodes stacked on the WSe2 by transfer technique have been reported. However, unipolar conduction has not been achieved in FETs based on TMD materials and graphene electrodes. Here we report a synthetic process to directly grow WSe2 monolayers along the edge of patterned few-layered graphene, forming the lateral heterojunction between the graphene and monolayer WSe2. The few-layered WSe2 bridges the few-layer graphene and monolayer WSe2, and an interpenetrating layered structure is formed between graphene and WSe2. As a result, the WSe2 monolayer channel and the junction to the graphene can be formed at the same time by the synthesis method, where graphene serves as source and drain. Graphene is in-situ heavily p-doped by H2 with covent bond during WSe2 growing process. Such a unique junction structure leads to a barrier less ohmic contact between doped graphene and WSe2. Unipolar WSe2 PFET with laterally contacted p-doped graphene source/drain (p-G/WSe2 PFET) can be achieved for the first time. With Pd contacted source/drain metal, the unipolar PFET perform Ion/Ioff > 105 and field effect mobility ~20 cm2/Vˑs. Moreover we can still have unipolar PFET with Ti source/drain metal exceeds 103 Ion/Ioff ratio even Ti work function is low (4.3 eV) and close to the conduction band edge of WSe2 (electron affinity of WSe2~ 4.03 eV).
Pseudocapacitive Electrodes Produced By Oxidant-Free Polymerization of Pyrrole Between the Layers of 2D Titanium Carbide (MXene)
Authors: Boota Muhammad , Anasori Babak , Voigt Cooper , Zhao Meng-Qiang , Barsoum Michel W. , Gogotsi Yury 
Published: February 2020

Pseudocapacitive electrodes based on electrochemically active organic materials are emerging for the energy storage applications.1 Organic materials are renewable, relatively inexpensive, lightweight, and their electrochemical properties can be tuned by changing their functional groups. Despite aforementioned advantages, they tend to degrade rapidly upon cycling mainly due to their poor conductivity. One option to improve their cycling performance is to graft/deposit them onto conductive carbon particles.2 Two-dimensional carbides and carbonitirides called MXenes, which generally offer metallic conductivity, may become a suitable option to replace carbon in pseudocapacitve electrodes to improve the electrochemical performance of the organic materials.3,4

Herein, we present simultaneous intercalation, alignment and oxidant-free polymerization of the pyrrole between the Ti3C2Tx MXene layers by mixing pyrrole monomer with the Ti3C2Tx colloidal solution. The optimized composition of the resulting composite yielded high volumetric and gravimetric capacitances of 1000 F/cm3and 416 F/g, respectively, at 5 mV/s. Furthermore, excellent capacitance retention of 92% was observed after 25,000 cycles at 100 mV/s.
1. M. Boota et al., Adv. Mater. (2015). DOI: 10.1002/adma.201504705
2. M. Boota et al., ChemSusChem, 8, 3576–3581 (2015)
3. M. R. Lukatskaya et al., Science., 341, 1502–1505 (2013)
4. M. Ghidiu, M. R. Lukatskaya, M.-Q. Zhao, Y. Gogotsi, and M. W. Barsoum, Nature, 516, 78–81 (2014)
(Invited) Interesting 1-D and 2-D Phases of MoS2
Authors: Loh Kian Ping 
Published: February 2020

Tailoring the dimension of nanomaterials to achieve precise tuning of optical, electronic and catalytic properties have been the major goals of researchers for decades. Two dimensional metal chalcogenides of the MX2 (M=Mo, W and Ti, X= Se, Te) family represent the ultimate control of material dimension in the vertical direction, and exhbits unique quantum confined optoelectronic properties. At the 1-D level, MoS2 quantum wires display quasi one-dimensional metallic state and novel ferromagnetic behavior that is tunable by its width and edge configurations. Unlike graphene nanoribbons which have been successfully synthesized using bottom–up molecular techniques, there are scant reports on the growth of MoS2 nanoribbons. Herein, we report two novel phases of sub-stochiometric MoS2 (MoSx) grown on Au (111) and Cu (111), respectively. We performed the templated growth of well-aligned, sub-stoichiometric MoSx molecular wire on Au(111) vicinal surface. Interestingly, we observed the dynamic assembly of MoSx molecular wires and its phase transition into stoichiometric MoS2 nanoribbon. On Cu (111) surfaces, we studied the growth of a novel MoSx 2-D phase which shows catalytic activities for the oligomerization of small molecules on its basal planes. Due to the in-plane rotational freedom and greater diversity of bonding arrangements in MoS2, a plethoras of different polytypes may be possible when the structural assembly is mediated by metal substrate. Thus a whole new class of alternative 2D structures, uniquely different to the classical chalcogenides in terms of electronic and physical properties, may be possible.
Photocatalytic Hydrogen Production Via Water Splitting Using Different Gold-Based Catalysts
Authors: Arango Juan C. , Machín Abniel , Márquez Francisco 
Published: February 2020

In order to avoid serious environmental and economic damages from energy use, humans must stop using fossil fuels altogether, as soon as possible. One possible strategy to cut the dependence of fossil fuels and, at the same time create a new economic force, is to develop a hydrogen based energy economy. A potentially viable way forward is to produce H2 from water by combining solar energy and heterogeneous photocatalysts. For these reasons the objectives of this investigation were: 1) synthesize a high surface area TiO2 nanowires (NWs) catalyst in the rutile phase, 2) incorporate different amount of gold nanoparticles into the as-synthesized catalyst and into the commercial form of TiO2 (Degussa P-25) using a chemical reduction method, 3) produce hydrogen via water splitting using visible and ultraviolet light. The hypotheses of the study were: a) The catalyst with the biggest surface are will produce the biggest amount of hydrogen, and b) The gold nanoparticles will enhance the hydrogen production and will allow the use of visible light, diminishing the semiconductor’s band gap and working as an electron trap. Interestingly, the incorporation of gold nanoparticles into the titania surface enhanced the surface area in both P25 and TiO2 NWs. The hydrogen production obtained by using Au/P25 catalysts was measured to be 800 μmolg-1h-1 under irradiation at 400 nm and 1,436 μmolg-1h-1 using Au/TiO2 NWs at the same wavelength. Both of the hypotheses were correct and all the objectives achieved. The characterization of the synthetized compounds were performed with: 1) X-ray diffraction (XRD) to confirm the crystalline form of the TiO2 synthetized nanowires. 2) Field emission Scanning Electron Microscopy (FESEM), to confirm the morphology of the synthetized compound. 3) Brunauer, Emmett and Teller (BET) instrument to measure the surface area of the gold based nanowires and the commercial TiO2 form P-25. 4) The hydrogen production was measured using a Gas Chromatographer with a Thermal Conductive detector (GC-TCD) attached to a solar simulator. 5) Ultra Violet Visible spectroscopy (UV-VIS) was used to obtain the absorption spectrums of the synthetized TiO2 rutile phase nanowires before and after the gold deposition. Finding renewable sources of energy is one of the biggest challenges of the 21st century and this investigation contributes into that.
(Invited) Heterogonous Mixed Ion and Electron Conducting Membranes for Efficient Electrochemical CO2 Capture and Conversion
Authors: Huang Kevin 
Published: February 2020

Cost competitive and easily accessible fossil fuels are the dominant energy source powering our society. However, burning fossil fuels emits significant amount of CO2, a greenhouse gas that can cause global warming and climate change. Therefore, mitigating CO2 emissions from the use of fossil fuels is imperative. Among all the options, carbon capture and storage (CCS) is considered the best near-term solution.
The CO2 capture technologies currently being developed are targeting three point sources related combustion and gasification processes: post-combustion, oxyfuel combustion and pre-combustion. The state-of-the-art CO2 capture methods are primarily based on reversible chemical/physical absorptions/ adsorptions principles. A grand challenge to these technologies is the high cost and energy penalty. Developing advanced cost-effective and energy-efficient carbon capture technologies is therefore highly desirable.
In this presentation, we show by extensive experimental data and theoretical analysis that two classes of mixed ion and electron conductors are promising candidate membranes for high-flux, high-selectivity, cost-effective and energy-efficient carbon capture based on the electrochemical principles. By combining these membranes with proper conversion mechanisms, the captured CO2 can be instantly converted back to a fuel form, making the overall process carbon neutral.
Transition Metal Phosphides As CO2 Reduction Catalysts
Authors: Calvinho Karin U. D. , Laursen Anders B. , Goetjen Timothy A. , Garlapati Avinash B. , Dismukes Gerard Charles 
Published: February 2020

The development of efficient catalysts for converting water and CO2 selectively to hydrocarbons using renewable (electrical) energy is considered the “holy grail” of a sustainable energy economy. Electrochemical CO2 reduction has been demonstrated to form CO, HCOOH, C1 and C2 alcohols on noble metals,1,2 and alkanes on copper.3 These technologies are still pre-commercial and limited by three main problems: 1) atom efficiency: significant H2 production at the expense of the desired product; 2) selectivity: low for a single hydrocarbon product, and 3) electrical efficiency: high overpotential for the reaction. Among the proposed mechanisms on copper, two steps have been postulated as rate-limiting: 1) reductive binding to form adsorbed CO2
-* and, 2) hydrogen addition to adsorbed CO* forming HCO*4.
To overcome these barriers, we used three strategies which involve use of catalyst surfaces comprised of binary solids (MxPy) in which: 1) phosphorous is chosen for its high P-O bond energy needed to stabilize side-on binding of the HCO* and CO2
-* intermediates via O atom; 2) the M-C bond energy is controlled (choice of M); and 3) an adjustable M-P interatomic spacing that allows C to adopt its favored trigonal binding geometry (ideal sp2 C hybridized orbitals). We have synthesized four distinct binary transition metal phosphides, having pure and stable crystalline phases and evaluated their performance as catalysts for CO2 reduction using low surface area (flat) electrodes. This allows for direct observation of catalytic activity on the most stable crystal termination and is directly comparable to Cu-foils reported in the literature. Herein we present results that show CO2 reduction to CH4 at -0.6 V, the lowest potential seen thus far to our knowledge. Furthermore, using metal phosphides there is no formation of carbon monoxide, a poisonous gas that is produced in large quantities when copper is employed as catalyst.
Supported by Rutgers University and the Science Without Borders CAPES fellowship.
(1) Cole, E. B.; Lakkaraju, P. S.; Rampulla, D. M.; Morris, A. J.; Abelev, E.; Bocarsly, A. B. J. Am. Chem. Soc.
2010, 132 (33), 11539–11551.
(2) Barton, E. E.; Rampulla, D. M.; Bocarsly, A. B. J. Am. Chem. Soc.
2008, 130 (20), 6342–6344.
(3) Hori, Y.; Kikuchi, K.; Suzuki, S. Chem. Lett.
1985, No. 11, 1695–1698.
(4) Peterson, A. a.; Abild-Pedersen, F.; Studt, F.; Rossmeisl, J.; Nørskov, J. K. Energy Environ. Sci.
2010, 3 (9), 1311.
Electrochemical Microfluidic Immunoarray for Assessment of Aggressive Vs Indolent Forms of Prostate Cancer
Authors: Otieno Brunah A , Mercer Conan P , Jones Abby L , Krause Colleen E , Sherafeldin Mohammed , Joshi Amit A , Leech Dónal , Rusling James F 
Published: February 2020

Prostate cancer is the most common cause of cancer-related death in men in the US and throughout the world. Current practices for detection and staging of prostate cancer often fall short in terms of sensitivity, specificity and inability to distinguish between aggressive and indolent forms of prostate cancer. These limitations lead to unnecessary treatments that adversely affect the patients’ quality of life with minimal or no gain. Measurement of small panels of molecular signature biomarkers in serum holds tremendous potential for cancer diagnostics and personalized therapy. Here we describe a simple, low-cost, modular microfluidic system for on-line capture and detection of prostate cancer protein biomarkers. The protein panel includes PSA, CD-14, ERG, GOLM-1, PEDF-1, IGF-1, VEGF-D and IGFBP-3, many of which are thought to be specific for aggressive prostate cancer. The system features a small chamber for on-line protein capture from serum by magnetic beads labeled with many copies of analyte-specific antibodies and signal-transducing enzyme labels, positioned upstream of a detection chamber housing a nanostructured 8-electrode sensor array. Gold immunoarrays fabricated by ink-jet printing ($0.2) or commercial screen printed carbon arrays ($5) are fitted into the microfluidic detection chamber to achieve high sensitivity. Ultralow detection limit in the low fM range was achieved for multiplexed detection of the cancer biomarker proteins from as little as 5 uL. Measurements of this panel of selected biomarkers will be tested with prostate cancer patient samples in future to assess its diagnostic capability.

Figure 1