bluuebunny/crossref_metadata_2025_split huggingface dataset:
Novel Sensing System for in-Situ Monitoring Soil Water Content
Authors: Zhang Lin , Cheng Z.-Y. 
Published: February 2020

Water shortage is a world-wide issue and currently 70% of global freshwater consumption is agriculture. Unfortunately, the water use in agriculture is often inefficient with only a fraction of the water diverted for agriculture effectively used in plant growth, with the rest lost via soil drainage, evaporation, or transpiration. Water efficiency in agriculture has been extensively researched. Conversion from traditional furrow irrigation to micro-irrigation methods has been shown to reduce irrigation needs for about 50% while improving yields. Universally applied micro-irrigation solutions many not realize improved yields due to different crop requirements and the high specificity of agriculture practices. Improving the efficient use of water still demands the development of new technologies that cost less and save energy by accurately assessing crop status for a given location, climate and soil condition. To reach this, it is critical to monitor the soil water content (SWC) or soil moisture in a real-time manner.
Many technologies have been developed and are currently widely used to determine the SWC. Most of these technologies are stationary. That is, the soil samples have to be collected in the field and it is, then, immediately stored in a special bag to keep the moisture and delivered to a laboratory for the test. This is time consuming process and adds additional cost to the characterization of SWC. Technologies, such as time domain reflectometry, have the capability to determine the in-situ SWC in a real-time manner, but it is only for a localized spot. Therefore, it is very critical to find a right spot to perform the characterization/analysis, which is somehow arbitrary and requires trained personnel. For a farm land, many spots have to be analyzed to determine the average SWC for the farm land.
This work is designed to develop a rationally new technology that can monitor the average SWC over a farm land. The technology is for in-situ analysis and has the potential to be developed as a wireless network. A sensing system is designed and built to determine the average SWC over a farm land, as illustrated in Figure 1. A few spots (i.e., the corners and center of a farm land) are selected as the nodes, as shown in Figure 1 (a). At each node, an electrical pole (i.e., probe) will be installed as illustrated in Figure 1(b). Each probe contains a few electrodes which are located at different depths underground. The part of the electrical pole outside of soil is either an electronic deliver or electronic receiver. Two probes form a measuring sensor/system, such as contacting with a lock-in amplifier, which determines the average SWC over the area, as shown in Figure 2 (c and d). The system is tested in real farm land to determine the maximum area can be analyzed. Other commercial sensors are used to validate the sensor system for SWC determination.

Figure 1 (a) Schematic of sensor networks for measuring SWC, (b) electrical pole, and two probes to form a measuring sensor: (c) top view and (d) side view.

Figure 1
ZnO Nanostructures with Different Morphologies and Their Combinatorial Optimization with Graphene Oxide for Gas Sensor Properties
Authors: Lee Eunji 
Published: February 2020

Consumer concerns on food safety and quality are increasing worldwide. Without opening the package of food products, collecting information about freshness of the product is desirable. Therefore, an electronic nose device consisting of multiple gas sensors can be utilized for rapid monitoring of food quality and freshness at low cost. Such multiple gas sensors, i.e array structure can provide selective detection and identification of various compounds by linking gas responses to signal process. Gas sensors based on chemical reaction on the surface of semiconducting metal oxides are readily available commercially. Common material of the metal oxide sensor is tin oxide doped with a small amount of a catalytic metal such as palladium or platinum. The improvement of gas sensing performance such as low operating temperature as well as selective and sensitive detection can be obtained by investigating potential oxides with controlled morphologies at the nanoscale and their composite structures.
Among various semiconducting materials, ZnO is an excellent candidate for gas sensor applications. In addition, many methods can be utilized to fabricate various ZnO nanostructures. Solution process can be simple and effective bottom-up path to construct hierarchical ZnO nanostructures on various substrates. Therefore, we investigated a solution method as controlling the morphology of ZnO nanostructures by applying DC and AC bias and by selecting different precursors. ZnO nanorods structure was synthesized using zinc nitrate hexahydrate and HMT (hexamethylenetetramine) in aqueous solution. The use of zinc chloride instead of zinc nitrate hexahydrate for zinc precursor, nanoflake structure was successfully fabricated where zinc chloride serves as a capping ion to prevent isotropic growth. With applying external voltage during solution growth, ZnO nanorods became agglomerate structures and the degree of agglomerates varies depending on the range of external bias.
Various ZnO nanostructures have been analyzed with SEM, XRD and UV-visible. Figure 1 shows one example of morphological control of ZnO nanostructures according to applying bias and precursors. The change of morphologies showed different degree of orientation of the structures by XRD result. Gas sensing response was measured to extract characteristic feature at different ZnO morphologies. Elevated operating temperature approaching 200 – 300°C from ZnO gas sensor can be lowered by combining graphene oxide (GO). Various combinatorial structures from ZnO and GO were explored. Detailed discussion on gas sensing properties and their mechanisms will be given.

Figure 1
The Role of Pre Hydrogen Flow in Nucleation of Graphene on Silicon Nitride
Authors: Park Segeun , Kang Doyeon , Roh Yonghan 
Published: February 2020

Graphene has been considered as one of most attractive materials in nano-scaled electronic devices. Graphene film has been mainly grown on many metal (eg., Ni , Cu, Fe) by chemical vapor deposition (CVD) process and transferred on dielectric substrate. However, the complicated transfer techniques for metal-catalyzed graphene inevitably have resulted in wrinkles, holes, and metal etching residues. Thus, there is a substantial need to develop a scalable method for reliable production of large-area graphene directly on insulating substrates.
We synthesized the nucleation of graphene on silicon nitride (Si3N4) substrate and report the influence of pre hydrogen flow during CVD process on silicon nitride which is the stable dielectric and suitable for carbon diffusion barrier. Test wafer was cleaned in 10:1 HF solution and nucleation of graphene was synthesized by CVD process using CH4, Ar, H2gas at 1000°C.
We evaluated the graphene nucleation with and without pre hydrogen flow on silicon nitride film as shown in Fig.1. Although amorphous carbon cluster was formed on silicon nitride without pre hydrogen flow as shown in Fig. 2(a), Raman shift peak related graphene was obtained with pre hydrogen flow condition as shown in Fig. 2(b). It is assumed that hydrogen ions are bonded with silicon atom on silicon nitride surface during pre hydrogen process and then chemisorptions of carbon precursors on the H-terminated surface are easily made. Fig.3 shows the role of hydrogen [1]. To synthesize the graphene film on silicon nitride, it is essential to be terminated with hydrogen at silicon nitride surface.
Reference
[1] Jae-Hyun Lee et al, “Wafer-Scale Growth of Single-Crystal Monolayer Graphene on Reusable Hydrogen-Terminated Germanium”, Science, Vol. 344, 2014

Figure 1
Focused Ion Beam Milling Technique for Plan-View TEM Sampling of DRAM Capacitor
Authors: Lee Sungho , Kang Jonghyuk , Yang Cheol-Woong 
Published: February 2020

As the semiconductor device feature size becomes smaller, the aspect ratio of DRAM capacitor gets higher. The higher the height of capacitor, the more storage node bent. Therefore, we adopt the Mechanically Enhanced Storage node for virtually unlimited Height (MESH) [1] process to prevent storage node’s bending nowadays. Nevertheless, the bending failure still exists, and thus we need to make a sample for physical failure analysis (PFA). Normally PFA needs a site specific transmission electron microscopy (TEM) sample which is vertically cross-sectioned by using focused ion beam (FIB) , but sometimes a plan-view TEM sample is also required to clarify the exact cause of failure.
Figure 1-(a) shows the vertical TEM result of two bits failure caused by DRAM storage node’s bending. In the conventional plan-view TEM sampling process, the target height for plan-view TEM sampling is marked with ‘l’ shape marker [2] after realizing the height of node bridge as shown in figure 1-(b). It is important to know the end point during FIB milling [3]. And then, the top (red area) and bottom (yellow area) parts are removed to get the plan-view TEM sample. Figure 1-(c) is a TEM image after this plan-view TEM sampling process. The nodes do not stand in a line as you see in figure 1-(c). The nodes seem to move during the 3rd step milling (mill a bottom part) because of the void between nodes. The node may fall off a TEM thin foil sample in the worst case. In order to overcome this problem, we add a carbon deposition step right after the 2nd step of the top part milling as shown in figure 2-(a). As a result, we are able to get a plan-view TEM image where the nodes stand in a line as shown in figure 2-(b). Four major steps are,
Step 1 : ‘1’ shape marking at the target height
Step 2 : milling a top part of capacitor
Step 3 : carbon deposition to fill the space between nodes
Step 4 : milling a bottom part of capacitor
We adopted this modified milling method to the TEM sampling of a real failure case and obtained a PFA result of a 2 bit failure using plan-view TEM image as shown in figure 2-(c). The new modified milling method turned out to be very effective and can be adopted in a mass production.
References
[1] D. Kim, J. Kim, M. Huh, Y. Hwang, J. Park, D. Han, D. Kim, M. Cho, B. Lee and H. Hwang, in Electron Devices Meeting, 2004. IEDM Technical Digest. IEEE International, p. 69 (2004).
[2] Moon-Yee Wang, S.X. Lee, S. Peri, “The Effect of FIB Technology on Design Methodology”, Circuits and Systems, 1993, 725-728 vol1.
[3] S. Lee, C.-W. Yang, T. J. Park, J. K. Kim, J. H. Ahn, J. Choi and G. Y. Song, in Meeting Abstracts, p. 1608 (2014).

Figure 1
Reaction Energies for Electrode Surface Atom Insertion into R-H Bonds and Their Dependence on Electrode Potential: Application to Pt(111)
Authors: Zhao Meng , Anderson Alfred B. 
Published: February 2020

Electrochemistry is not ordinarily expected to be a tool for measuring bond strengths. Our work shows how to determine R─H bond strengths from reversible potentials, U
rev, for outer sphere and surface oxidation reactions:
R-Haq ⇌ Raq + H+
aq + e- (1)
and
R-Hads ⇌ Rads + H+
aq + e- (2)
The electrode considered for this work is the close-packed Pt(111) surface.
The R─H oxidation reactions addressed are those that occur during ethanol oxidation at the anode in a fuel cell. The reversible potentials for the reactions taking place on the electrode surface are significant to understanding the mechanism of the 12 electron oxidation reactions and the limitations of platinum as an electrocatalyst. They were determined previously for reaction (2). However, there is another mechanism for an R─H bond oxidation, and that is dissociation of the bond on the surface by metal atom insertion or by H atom abstraction prior to aqueous proton formation. Our work addresses the insertion mechanism.
We show that R─H bond strengths in R─Haq and R─Hads are functions of reversible potentials for their oxidations. We find that underpotential deposited (UPD) hydrogen on Pt(111) electrodes makes the R─Hads bond strengths zero for reactions that have reversible potentials in the range from 0.0 V (vs. SHE) to 0.35 V (vs. SHE). For R─Hads reactions with reversible potentials in the double layer region (U
rev > 0.35 V), the dissociation bond strengths are greater than zero and increase linearly with increasing reversible potentials. When the reversible potentials of R─Hads oxidation are above the double layer potential region (U
rev > 0.6 V), Oads and OHads form which block R-Hads dissociation. The R-Hads dissociation is also blocked in the potential region of H2 evolution(U
rev < 0.0 V).
Fabrication of Ag-Deposited Silicon Nanoparticles for a Lithium Ion Battery Anode Prepared By Alkaline Immersion Plating
Authors: Sugawara Yu , Arai Susumu 
Published: February 2020

INTRODUCTION
Lithium ion batteries (LIBs) with greater energy density are required for use in energy-demanding applications such as electric cars and electronic devices. Silicon is an attractive candidate anode material for use in LIBs due to its high theoretical capacity (4200 mAh/g) compared to carbon (372 mAh/g) currently used in commercially available lithium ion batteries.
The commercial use of Si-based powders in anodes remains hindered by the low electrical conductivity of silicon and its huge volume change during lithiation and delithiation.
Many studies have been conducted to alleviate the pulverization of silicon during the charge/discharge process and to increase the conductivity of silicon materials. Recently, several approaches for synthesizing 3D porous Si-based anode materials that exhibit good cycling characteristics have been developed. Several approaches employ a wet-chemical etching process using hydrofluoric acid (HF) and silver nitrate (AgNO3). The fabrication process consists of two steps. First, Ag is deposited on silicon nanoparticles using HF and AgNO3. Subsequently, the particles are immersed into HF and hydrogen peroxide (H2O2), resulting in the generation of 3D porous silicon nanoparticles. However, HF is a dangerous chemical and thus a process not requiring HF for the fabrication of Ag-deposited silicon particles is required.1,2,3)

Herein, we present Ag-deposited silicon nanoparticles
fabricated using an alkaline method and describe their charge/discharge properties as a LIB anode material.
EXPERIMENTAL
We used planetary ball milling silicon nanoparticles. An immersion plating bath containing 2 g/L Si, 0.005 M AgNO3 and 0.010 M EDTA-2Na was prepared, and KOH was then added to adjust to pH 9~12. The silicon nanoparticles were dispersed using ultrasonic irradiation for 30 min. The reaction was conducted in a water bath to maintain the temperature at 25, 30 40, 50, 60, 70, 80°C, respectively for 2 hours. The silicon nanoparticles were then collected on a filter by suction filtration and dried in vacuum at 110 °C for 2 hours.
The microstructures of the samples were observed using field-emission scanning electron microscopy (FE-SEM) and scanning-transmission electron microscopy (STEM). Charge-discharge cycle tests of the prepared samples were performed. A coin cell (Model CR2032) was used as the test cell and lithium metal foil was used as the counter electrode. The cut-off potentials for the charge/discharge processes were 0.02 V and 1.5 V (vs. Li/Li+).
RESULTS AND DISCUSSION
Ag-deposited silicon nanoparticles were fabricated using an alkaline immersion plating method in the absence of HF.
REFERENCES
1) Jung-In Lee, Soojin Park Nano Energy (2013) 2, 146-152
2) Satoshi Uchida, Megumi Mihashi, Masaki Yamagata, Masashi Ishikawa, Journal of Power Sources 273 (2015) 118-122
3) Chunli Li, Ping Zhang, Zhiyu Jiang Electrochemica Acta 161 (2015) 408-412

Figure 1
Specimen Preparation Method to Dual-Axis TEM Analysis Technique
Authors: Park Sang Gul , Lee Sungho 
Published: February 2020

We usually do Physical Failure Analysis (PFA) to visualize the failure in the semiconductor process. First, we find the site-specific target (or failed cell). And then, we should do de-processing which contains lapping and chemical etch. As the semiconductor gets more complex and multi-layer, we should do multi-de-processing steps. If the failure has the oxide-material, we cannot know the cause of failure. Because the oxide can be removed by Hydrogen Fluoride (HF) chemical, which means the failure will be gone during de-processing step. We should use Focused Ion Beam (FIB) which can make a thin sample to exclude chemical step. High-resolution analytical tools such as Transmission Electron Microscopy (TEM) have become indispensable in PFA. We make a Dual-Axis TEM (DAT) method for PFA. We make a Plan-view TEM (PTEM) sample with FIB first, we can find an exact location of failure through the first step. And then, we make cross-sectional TEM (XTEM) sample with a site-specific target in PTEM sample. Below summarizes the four major steps and its precautions;
1. Making a Planar lamella by FIB
2. Observing a PTEM specimen with TEM
(Precaution : zone axis should be adjusted exactly)
3. Making a cross-section lamella by FIB
(Precaution : Protection layer should be deposited on both sides)
4. Observing a XTEM specimen with TEM
We propose DAT method to improve the problem of artifact in de-processing step. The TEM result with DAT method is shown in figure 4. We can know the exact location of failure with observing a PTEM sample. We can know the cause of failure with observing a XTEM sample. Moreover, we can analysis the chemical and physical information through DAT method. This method is very effective and has a high success rate in analysis.

REFERENCE

[1] A.E.M. De Veirman, “3-Dimensional’ TEM silicon-device analysis by combining plan-view and FIB sample preparation”, Materials Science and Engineering: B, 102(1-3), pp. 63-69, 2003.
[2] Jon C. Lee, David Su, J.H. Chuang, “A Novel Application of the FIB Lift-out Technique for 3-D TEM Analysis”, Microelectronics Reliability Asset, 41(9-11), pp. 1551-1556, 2001.

Figure 1
Surface Functionalized Carbon Nanofiber Supports for Alkaline ORR Catalysts
Authors: Huang Wenjiao , Ahlfield John M. , Kohl Paul A , Zhang Xinsheng 
Published: February 2020

Fuel cells are attractive because they provide clean and efficient energy for stationary and portable applications. Among the various types of fuel cells, the proton-exchange membrane fuel cells (PEMFC) have a high energy density and a fast start-up, but the cost of noble-metal catalysts and perfluorinated membranes is high. Anion-exchange membrane fuel cells (AEMFC) are attractive because they have enhanced the oxygen reduction and methanol oxidation kinetics at high pH, which makes the use of non-noble catalysts possible.
Carbon nanofibers (CNFs) have outstanding structural, mechanical and electrical properties, and are widely used as catalyst supports in fuel cells. CNFs are also considered to be good material for the oxygen reduction reaction catalysts in alkaline fuel cells because of their high surface area, thermal stability and electrical conductivity.
In this work, we use CNFs as the support for fuel cell catalysts in hybrid fuel cells, which combine alkaline and acidic conditions at the different electrodes. Functional groups were added onto the CNFs, including carboxyl groups (CNF-OX), carbonyl groups (CNF-CO), hydroxyl groups (CNF-OH) and nitrogen-containing groups (CNF-ON). In previous studies, they were tested them in half-cell experiments and it was found that the catalysts supported on CNF-ON have high ORR activity. The CNF-ON electrodes can change the ORR from the two-electron pathway to the four-electron pathway. Pt/CNFs have been tested in hybrid fuel cell and compared with Pt/C.
C-Doped TiO2-B Nanowires Derived from TiC As an Anode Materials for Lithium Ion Batteries with High Rate Performance
Authors: Goriparti Subrahmanyam , Zaccaria Remo Proietti , Capiglia Claudio 
Published: February 2020

In the recent past nanostructured materials have been attracting much interest owing to their physical and chemical characteristics, which make them extremely suitable for a number of applications. In particular, one of the most promising applications is their use as electrode materials for rechargeable lithium ion batteries (LIB)1-2.
Among the anode materials, Titanium dioxide (TiO2) has been deeply investigated for lithium intercalation/de-intercalation due to high rate capability, very good reversible capacity, low volume expansion ( <2% ) upon cycling and furthermore lost cost, high abundant and very safe lithium reaction potential ~ 1.5 V vs Li/Li+, owing to these characteristics, TiO2 anodes have been considered to target in EVs and HEVs application1-3. Recently, the various polymorphs of TiO2 (anatase, rutle, brookite and bronze) have been explored as efficient anodes for LIB3. In particular, TiO2-Bronze (TiO2-B) has been receiving significant interest due to its theoretical capacity of 335 mAh g-1. Importantly, TiO2-B manifests the major advantages of fast charging-discharging through a pseudo-capacitive mechanism in addition to the bulk diffusion, whereas other polymorphs of TiO2 mostly show intercalation of Li-ion through bulk diffusion controlled mechanism3. However, the low electronic conductivity and low rate of Li-ion diffusivity of TiO2 are key issues for a high rate capable anode. To overcome these issues, we report synthesis of carbon-doped TiO2-B nanowires by facile and inexpensive method without using external carbon source. The carbon doping was verified by UV–visible and X-ray photoelectron spectroscopy and further structure and morphology was investigated with X-ray diffraction, Raman spectroscopy and Scanning and Transmission microscopies. The electrochemical performances of the C doped and undoped TiO2-B nanowires were tested by galvanostatic charge/discharge cycling, cyclic voltammetry, and electrochemical impedance spectroscopy. This novel C-doped materials presented high capacities and higher rate capability in electrochemical cycling experiments with respective to undoped material. This is attributed to the reduction of Li-ion diffusion path lengths along with improving electrical conductivity of TiO2-B nanowires. The electrochemical experiments demonstrated that C-TiO2-B nanowires electrodes exhibited superior lithium storage capacity of ~306 mAh g-1 at current rate of 0.1C as well as excellent rate ability of ~160 mAh g-1even at high current rate of 10C after 1000 cycle in lithium-ion batteries.

References:

S.Goriparti, E. Miele, F. D. Angelis, E.D. Fabrizio, R. P. Zaccaria, C. Capiglia, J. Power Sources, 257 (2014) 421

G. Zhu, Y. G. Wang and Y. Y. Xia, Energy Environ. Sci., 5 (2012) 6652

A. G. Dylla, G. Henkelman and K. J. Stevenson, Acc. Chem. Res, 46 (2013) 1104

Figure 1