Volume 9, Issue 3, March 2018

Effect of Mg content in Ag/Zn1-XMgXO/Cu structure for bipolar resistive switching performances

Dibyaranjan Mallick; Ravi Prakash;Davinder Kaur; Rahul Barman; Kirandeep Singh

Advanced Materials Letters, 2018, Volume 9, Issue 3, Pages 153-157
DOI: 10.5185/amlett.2018.6952

In this study, the bipolar resistive switching behavior of Pulsed Laser Deposited Zn1-xMgxO (x= 0, 0.1) thin films in Ag/Zn1-XMgxO/Cu structure has been investigated. The XRD pattern of Zn1-XMgxO exhibits the presence of (002) and (103) reflection. The cross-sectional field emission scanning electron microscopy (FE-SEM) studies were further carried out to examine the thickness of the film. In order to analyze the bipolar resistive switching behavior of the Zn1-xMgxO thin films, an I-V measurement was performed at room temperature. The memory cell Ag/Zn0.9Mg0.1O/Cu exhibits set voltage (ON state) at 2.57V and reset voltage (OFF state) at -3.15 V, excellent OFF to ON resistance ratio (~10 5 ) for 200 DC sweep cycles and exhibits good retention (>10 3 s). The physical mechanism responsible for exhibiting switching behavior in the Zn1-xMgxO thin films was explained by formation and rupture of the nano-scale conduction filament due to Oxygen vacancies. Ohmic conduction and Poole-Frenkel emission are responsible for current conduction in Low Resistance State (LRS) and High Resistance State (HRS) regions respectively. Enhanced switching behavior is observed by substitution of Mg in ZnO thin film. Nonvolatile two resistance states of the Zn1-XMgxO thin film could prove useful in future power efficient memory devices. 

Corrosion protection of mild steel by environment friendly Polypyrrole/Gum Acacia Composite Coatings

Gazala Ruhi; Haritma Chopra;Sundeep K. Dhawan; Pradeep Sambyal; Hema Bhandari

Advanced Materials Letters, 2018, Volume 9, Issue 3, Pages 158-168
DOI: 10.5185/amlett.2018.7007

In a novel approach, Polypyrrole/Gum Acacia composites (PPy/GA) were synthesized by in-situ oxidative polymerization of pyrrole on the Gum Acacia (GA) surface by using FeCl3 as oxidant. The 1 HNMR and FTIR confirms the presence of peaks of Polyprrole and Gum Acacia in the composite. The microstructural analysis of the composite reveals uniform layer of Polypyrrole on the surface of GA particles. The X-ray Diffraction pattern reveals the amorphous nature of the composite. Powder coating technique was used to design the composite coatings. The electrochemical studies like Open Circuit Potential (OCP) variation with time, Potentiodynamic Polarization and Electrochemical Impedance Spectroscopy (EIS) were conducted in 3.5% NaCl solution to evaluate the corrosion resistance of the coatings. The composite coatings demonstrated superior corrosion resistance in salt spray fog of 5.0% NaCl (under accelerated test conditions in salt spray chamber). The synergistic combination of the corrosion inhibition properties of Gum Acacia and the redox properties of Polypyrrole is the reason for the occurrence of high corrosion resistance of the composite coatings. The present coating composition has shown excellent corrosion resistance and can be a potential coating formulation for mild steel substrate used in various applications under saline conditions.

Effect of residual stress in Pb (Zr0.52Ti0.48) O3 – BiFeO3 multilayer cantilever structure

Shankar Dutta; Ramjay Pal;Ratnamala Chatterjee

Advanced Materials Letters, 2018, Volume 9, Issue 3, Pages 169-174
DOI: 10.5185/amlett.2018.6973

This paper discussed about the integration issues of Pb (Zr0.52Ti0.48) O3 – BiFeO3 (PZT - BFO) multilayer thin film deposited on silicon substrate for possible application in future micro-electro-mechanical system (MEMS) devices. The PZT - BFO multilayer thin film is deposited on silicon wafer by sol-gel technique. The multilayer film is annealed at 650 °C in air for 60 min. The deposited multilayer film is found to be polycrystalline in nature. The PZT-BFO multilayer exhibited room temperature multiferroic properties (remnant polarization of 37 mC/ cm 2 and remnant magnetization of 3.1 emu / cm 3 ). To fabricate the PZT - BFO multiferroic cantilever structures, a two-mask process flow is developed. Etch rates of the PZT - BFO multilayer (180 nm/ min), ZrO2 buffer layer (35 nm/ min) and SiO2 layer (350 nm/ min) are optimized in CHF3 plasma. The multiferroic cantilever structures are released by isotropic etching of silicon using SF6 plasma. Bending and cracks are observed in the released cantilever structures due to the generation of residual stress in the multilayer thin film. Effect of residual stress on the PZT - BFO cantilever structure is also verified by simulation. 

Magnetic and dielectric properties of divalent Ca2+ and Ba2+ ions co-doped BiFeO3 nanoparticles

N. Manjula; S. Ramu; K. Sunil Kumar; R. P. Vijayalakshmi

Advanced Materials Letters, 2018, Volume 9, Issue 3, Pages 175-181
DOI: 10.5185/amlett.2018.1411

Pristine BiFeO3 (BFO) and Ca doped BiFeO3: Ba nanoparticles (NPs) were synthesized in aqueous solution by sol-gel method with Tartaric Acid as a chelating agent. EDAX measurements confirmed the presence of Ca, Ba in the BiFeO3 host lattice. X-ray diffraction analysis showed that the average grain size of the prepared samples was in the range of 09–28 nm. The lattice structure of the nanoparticles transformed from rhombohedral to tetragonal phase with Ca 2+ ions substitution increased. TEM images indicated that sphere and square shape of nanoparticles through a size ranging from 10 to 15 nm. Diffusion reflectance spectra of BiFeO3 NPs showed a substantial blue shift of ~100 nm (630 nm -> 530 nm) on Ca, Ba co-doping which corresponds to increase in band gap by 0.47 eV. Dielectric constant (ε’) and dielectric loss (ε’’) were measured in the frequency range 1 Hz to 1 MHz at room temperature. Dielectric constant and loss are increased with Ca concentration except for Ca (4 at. %). The bulk conductivity (σ) increases from 3.07 x 10 -6 S/m to 1.64 x 10 -5 S/m as the Ca concentration increased from 0.00 to 0.03. Magnetic measurements revealed the ferromagnetic character of Pristine BFO and Ca doped BiFeO3: Ba samples. It is observed that by increasing the Ca concentration the value of Mr and magnetization are varied irregularly upto Ca (4 at. %). But for x = 0.01 Mr and magnetization are highest. The values of magnetization and Mr for 1% Ca doped BiFeO3: Ba NPs are 2.99 emu/g, 1.54 emu/g, respectively, which are quite significant at room temperature. These materials have potential applications in data storage, switching devices, spintronics, sensors and microelectronic. 

Highly sensitive hydrogen gas sensor based on Al-doped SnO2/Polyaniline composite nanofibers

Hemlata J. Sharma; Bhaskar M. Bahirwar; Subhash B. Kondawar

Advanced Materials Letters, 2018, Volume 9, Issue 3, Pages 182-187
DOI: 10.5185/amlett.2018.1591

Metal oxide nanofibers showed keen interest in chemical gas sensing due to their unique chemical and electrical properties at operating temperature more than 200 o C. Their sensitivity can be improved at low operating temperature closed to room temperature by using conducting polymers. In this paper, Al doped tin oxide/polyaniline composite nanofibers detected H2 molecules at room temperature. A simple versatile electrospinning technique is used for the fabrication of Aluminium (Al) doped (tin oxide) SnO2 nanofibers and polyaniline was encapsulated using chemical oxidative polymerization (COP) of aniline monomer using ammonium persulfate as redox initiator. The structure and morphology of Al-doped SnO2/PANI composite nanofibers were investigated by SEM-EDX, UV-VIS and XRD spectroscopy. Structural changes of SnO2/PANI crystal due to the incorporation of Al 3+ ions have been explained. Al-doped SnO2/PANI composite nanofiber is very much selective towards H2 gas molecules in terms of high sensitivity, rapid response and recovery around room temperature compared to that of Al-doped SnO2. The present sensing mechanism systematically explained the existence of PN junction which is formed by p-type and n-type semiconductors in Al-doped SnO2/PANI hybrid composite material.

Three-dimensional Bi2WO6/graphene aerogel electrode for high-performance supercapacitor

Xun Xu; Fangwang Ming; Jinqing Hong; Zhoucheng Wang

Advanced Materials Letters, 2018, Volume 9, Issue 3, Pages 188-191
DOI: 10.5185/amlett.2018.1719

Graphene-based aerogels with porous structure and three-dimensional (3D) network have attracted plentiful interests recently because they could exhibit as an excellent matrix for various kinds of nanoparticles, thus providing a potential prospect in a variety of applications. In this report, 3D composite aerogel with poriferous structure assembly of bismuth tungstate sheets and graphene nanosheets has been prepared by a simple hydrothermal process. The 3D multihole structure of the hybrid aerogel could not only provide enormous surface area, but also facilitate electron transfer and ion transmission which could decrease the electrode internal resistance and consequently improve the capacitive property. As a result, the Bi2WO6/graphene hybrid aerogel achieves a large specific capacitance of 714 F g -1 at the current density of 4 A g -1 . The hybrid aerogel could provide a new method for developing high-performance energy storage materials.

Effect of deposition temperature on the electrochromic properties of WO3 grown by LPCVD

D. Louloudakis; D. Davazoglou;E. Koudoumas; D. Vernardou; G. Papadimitropoulos

Advanced Materials Letters, 2018, Volume 9, Issue 3, Pages 192-198
DOI: 10.5185/amlett.2018.1823

Monoclinic electrochromic tungsten trioxide (WO3) layers were grown on FTO substrates using a Low-Pressure Chemical Vapor Deposition (LPCVD) system. The effect of the deposition temperature on the structural and morphological characteristics as well as the electrochromic response of the layers was examined. It was found that increasing deposition temperature improves the crystallinity of the layers which affects their electrochemical/electrochromic behavior. 

Textile triboelectric nanogenerator for wearable electronics

Youfan Hu; Zhizhen Zhao; Zhaoxian Liu

Advanced Materials Letters, 2018, Volume 9, Issue 3, Pages 199-204
DOI: 10.5185/amlett.2018.1853

Textile-based electronics have attracted increasing interests due to the huge demand for wearable technologies. Working as the energy harvesting devices, textile triboelectric nanogenerators (t-TENGs) have exhibited remarkable superiority in mechanical energy harvesting for the future lightweight, portable, flexible, and green energy supply in wearable system. Here, a brief review will be given focusing on the recent progress of t-TENG, including the evolution of device structure, demonstrations of various self-powered systems, further integration capability with other kinds of energy devices, etc. All of these progresses reveal the power of this mechanical energy harvesting technology as a very appealing part in wearable electronics. 

Stacking patterns and carrier mobilities of GeS bilayer

Fazel Shojaei; Hong Seok Kang

Advanced Materials Letters, 2018, Volume 9, Issue 3, Pages 205-210
DOI: 10.5185/amlett.2018.1858

Based on the first-principles calculations, we identify four stacking patterns of the GeS bilayer, in which two most stable ones are almost equally stable. The most stable one corresponds to the experimental pattern in bulk GeS.  Its interlayer binding is stronger than those in a-phosphorene and graphene, indicating that the material will rather exist in the form of bilayers or multilayers. Our HSE06 band structure calculations show that both patterns are semiconductors with indirect band gaps in the visible region, which are slightly smaller than that of the monolayer. For the monolayer, our refined calculation based on the deformation potential approximation indicates that the electron mobility along the armchair direction amounts to 4.62×10 4 cm 2 V -1 s -1 , which is ~40 times larger than that of the a-phosphorene. The electron mobility of the bilayer is dependent on the stacking pattern. The most stable pattern is expected to exhibit the mobility of 1.69×10 4 cm 2 V -1 s -1 , which is still ~30 times larger than that of the bilayer a-phosphorene. A detailed comparison of the carrier mobilities suggests that both of the mono- and bi-layer will be useful for n-type electronics.

Stability of graphene suspensions in an aqueous based multi-component medium

Evgenyi Yakimchuk; Regina Soots; Irina Antonova

Advanced Materials Letters, 2018, Volume 9, Issue 3, Pages 211-215
DOI: 10.5185/amlett.2018.1885

The stability of multi-component graphene-based ink solutions for its optimization and alignment with complex requirements of inkjet printing technologies is considered in the present study. Stable compositions of a four-component suspension (graphene, water, ethanol, and ethylene glycol) were analyzed with the use of Hansen solubility parameters and their experimental corrections. Realization of a set of the stable suspension composition showed that the droplet forming conditions at inkjet printing were fulfilled in all cases. From the point of view of printed layer drying and suppression of the coffee ring effect, it was found that the ethylene glycol concentration has to be lower than 20%. Printing by inks, which fit the optimal composition in all respects, has demonstrated good electrical characteristics, namely, the layer resistance of  3 – 15 kΩ/gama for lines with a 20-40 nm thickness. 

Study of the properties of La-doped ZnS thin Films synthesized by Sol-gel method

Amel Tounsi; Djahida Talantikite-Touati; Hamid Merzouk; Hadjira Haddad; Roumaïssa Khalfi

Advanced Materials Letters, 2018, Volume 9, Issue 3, Pages 216-219
DOI: 10.5185/amlett.2018.1963

The thin layers of undoped ZnS and ZnS doped La with different concentrations (2, 4, 6, 8 and 10%) were deposited on glass substrates using sol-gel and dip-coating methods. The structural characterization of these samples was carried out by the  X-rays diffraction (XRD), scanning electron microscopy (SEM) and atomic force microscopy (AFM). UV-visible and Fourier Transform Infrared spectroscopy (FTIR) have been used to study the effect of dopant on the optical properties of ZnS doped La thin films. Atomic force microscopy images of the films have revealed homogeneous and granular structure and the SEM micrographies show deposit films with uniform and porous structure. The optical transmission spectra in the UV - visible range have shown that all the doped films present a good optical transmission in the visible domain.

Glucose detection via Ru-mediated catalytic reaction of glucose dehydrogenase

Won-Yong Jeon; Chang-Jun Lee;Hyug-Han Kim; Young-Bong Choi; Bo-Hee Lee; Ho-Jin Jo; Soo-Yeon Jeon

Advanced Materials Letters, 2018, Volume 9, Issue 3, Pages 220-224
DOI: 10.5185/amlett.2018.1947

In the electrochemical glucose sensor field, glucose dehydrogenase (GDH) has attracted attention as an enzyme alternative to glucose oxidase (GOD), which suffers performance issues due to variability in oxygen concentrations. The typical mediator used with GOD in electrochemical glucose sensors, hexamine ([Ru(dmo-bpy)2Cl2]), was synthesized and applied to facilitate electron transfer between GDH and the electrode. The prepared [Ru(dmo-bpy)2Cl2] was examined physicochemically by NMR, UV-vis, and XPS spectroscopy, and electrochemically by CV. Then, GDH and a cross linker, poly (ethylene glycol) diglycidyl ether, were adsorbed with [Ru(dmo-bpy)2Cl2] onto a screen-printed carbon electrode. The glucose response of [Ru(dmo-bpy)2Cl2] with GDH as an electron-transfer mediator was investigated by potentiostat. The resulting electrical currents were well correlated (R 2 = 0.9984) with glucose concentration (5.0, 10.0, 15.0, and 30.0 mM). Therefore, this ruthenium complex can be used for glucose detection with GDH as a good substitute mediator.