Charge Transfer Induced Molecular Hole Doping into Thin Film of Metal-Organic-Frameworks

Despite the highly porous nature with significantly large surface area, metal organic frameworks (MOFs) can be hardly used in electronic, and optoelectronic devices due to their extremely poor electrical conductivity. Therefore, the study of MOF thin films that require electron transport or conductivity in combination with the everlasting porosity is highly desirable. In the present work, thin films of Co3(NDC)3DMF4 MOFs with improved electronic conductivity are synthesized using layer-by-layer and doctor blade coating techniques followed by iodine doping. The as-prepared and doped films are characterized using FE-SEM, EDX, UV/Visible spectroscopy, XPS, current-voltage measurement, photoluminescence spectroscopy, cyclic voltammetry, and incident photon to current efficiency measurements. In addition, the electronic and semiconductor property of the MOF films are characterized using Hall Effect measurement, which reveals that in contrast to the insulator behavior of the as-prepared MOFs, the iodine doped MOFs behave as a p-type semiconductor. This is caused by charge transfer induced hole doping into the frameworks. The observed charge transfer induced hole doping phenomenon is also confirmed by calculating the densities of states of the as-prepared and iodine doped MOFs based on density functional theory. Photoluminescence spectroscopy demonstrate an efficient interfacial charge transfer between TiO2 and iodine doped MOFs, which can be applied to harvest solar radiations.Comment: Main paper (19 pages, 6 figures) and supplementary information (15 pages, 10 figures), accepted in ACS Appl. Materials & Interface

A Large Bandgap Shift in InGaAs(P)/InP Multi-Quantum Well Structure Obtained by Impurity-Free Vacancy Diffusion Using SiO2 Capping and its Application to Photodetectors

In this paper, we have investigated the bandgap tuning in the InGaAs (P)/ InP multiquantum well (MQW) structure obtained by impurity-free vacancy diffusion (IFVD) using low temperature photoluminescence (PL). The MQW intermixing was performed in a rapid thermal annealer (RTA) using the dielectric capping materials, Si02 and SiNX. The Si02 capping was successfully used with InGaAs cap layer to cause a large bandgap tuning effect in the InGaAs/InP MQW material. The blue shift of bandgap energy after RTA treatment was as much as 185 and 230 meV at 750 t and 850 t, respectively, with its value controllable using annealing time and temperature. Samples with Si02-InP or SiN-InGaAs cap layer combinations, on the other hand, did not show any significant energy shifts. The absorption spectra taken from the same samples confimed the energy shifts obtained using PL. The process developed can be readily applied to fabrication of photodetectors that are sensitive to wavelength and/or polarization.This work was fmancially supported in part by OERC(Opto-Electronic Research Center) through the grant # 97K3-0809- 02-06-1 and by the SPRC (Semiconductor Physics Research Center) of Korea. The authors thank U. H. Lee and Prof. D. Lee of Chung Nam National Univ. for their help with the absorption measurement

Plasma etching and surface characteristics depending on the crystallinity of the BaTiO3 thin film

Due to its high dielectric constant (κ), the BaTiO3 (BTO) thin film has significant potential as a next-generation dielectric material for metal oxide semiconductor field-effect transistors (MOSFETs). Hence, the evaluation of the BTO thin film etching process is required for such nanoscale device applications. Herein, the etching characteristics and surface properties are examined according to the crystallinity of the BTO thin film. The results demonstrate that the etching rate is low in the high-crystallinity thin film, and the surface residues are much lower than in the low-crystallinity thin film. In particular, the accelerated Cl radicals in the plasma are shown to penetrate more easily into the low-crystallinity thin film than the high-crystallinity thin film. After the etching process, the surface roughness is significantly lower in the high-crystallinity thin film than in the low-crystallinity thin film. This result is expected to provide useful information for the process design of high-performance electronic devices

Transition metal chalcogenides, MXene, and their hybrids : An emerging electrochemical capacitor electrodes

The amelioration of the human population and their reliance on energy-consuming devices have increased the global energy thirst, as well as the need for new, cleaner energy storage technology. Generally, storage devices are associated with batteries and fuel cells, but nowadays, supercapacitors are being used in laptops, cameras, cellphones, vehicles, and even airbuses, as they can quickly store a large number of charges and also have a long-life cycle and a large power density. However, they have a comparably lower energy density, which pragmatically binds their applications. Herein, we present a forward-looking review of 2D (two dimensional) TMDs (transition metal dichalcogenides) and MXene-based materials for their promising properties like unique electronics and tunable surface chemistry with their synthesis protocol, fundamental properties, and state-of-the-art electrochemical activity in supercapacitors. Finally, we discuss the challenges that restrict the electrochemical properties of pristine TMDs and MXene. And these problems have led to progress by encouraging the development of various derivatives and compositions of these materials to address these issues and improve their performance in emerging energy storage technologies

Resistive Switching Memory Properties of Electrodeposited Cu2O Thin Films

The Cu2O thin film was developed using an electrodeposition approach for resistive memory application. The impact of the deposition voltage (1V, 2V, 3V, and 4V) on resistive switching (RS)/memristive properties of Cu2O thin films was studied. The XRD spectrum reveals that deposited Cu2O has a cubic crystal structure. The bipolar RS in Al/Cu2O/FTO device was clearly observed during the current-voltage (I-V) measurement. The basic memristive properties were calculated from I-V data. The charge transport studies suggested that the SCLC mechanism was responsible for device conduction, and RS was due to filamentary effect. The result suggested that the electrodeposition technique is useful to fabricate a memristive device for various applications

Resistive Switching Characteristics of Electrochemically Anodized Sub-stoichiometric Ti6O Phase

We have developed Ti6O thin film using the electrochemical anodization approach for resistive switching (RS) application. The effect of anodization time (1 h, 2 h and 3 h) on the RS/memristive properties was investigated. The structural analysis was carried out by using the XRD technique, which reveals that the formation of the sub-stoichiometric Ti6O phase. The scanning electron microscopy image reveals that the thin film has compact and porous surface morphology. The electrical results clearly show bipolar RS in Al/Ti6O/Ti device. The boost in the RS properties was achieved by increasing the anodization time. The basic memristive properties were calculated using experimental I-V data. The Schottky, Hopping and Ohmic charge transport mechanisms contribute to the conduction, whereas the filamentary effect controls the RS process of the Al/Ti6O/Ti memristive devices

Bipolar Resistive Switching Characteristics of Ex-situ Synthesized TiO2-ZnO Nanocomposite

In this present article, we have reported a simple and cost-effective ex-situ synthesis of TiO2-ZnO (TZ) nanocomposite thin film by utilizing sol-gel, hydrothermal and solid-state reaction methods. The Ag/TZ/FTO nanocomposite device was developed and demonstrated the bipolar resistive switching (RS) characteristics for resistive memory applications. The result of XRD analysis confirms that the nanocomposite has mixed tetragonal and hexagonal crystal structures of TiO2 and ZnO, respectively. The hysteresis loop is an essential criterion for recognizing memristive devices and similar characteristic was noticed for the developed nanocomposite device. Besides, basic memristive properties were calculated from the I-V data. The charge transportation of Ag/TZ/FTO nanocomposite device takes place because of Ohmic and space charge limited current. The collective effect of oxygen vacancies and Ag ions was a basis of RS effect in the Ag/TZ/FTO nanocomposite device

Effect of Conductive Filament Temperature on ZrO2 based Resistive Random Access Memory Devices

In the present work, the effect of reset voltage, filament radius, filament resistivity, and oxide membrane thickness on the nanoscale ZrO2 RRAM devices was reported. The present investigation is based on the thermal reaction model of RRAM. The outcomes show a decline in saturated temperature with a rise in the radius and resistivity of filament. Furthermore, increases in saturated temperature with an increase in oxide membrane thickness were observed for the ZrO2 based RRAM device. The saturated temperature of the device was mainly influenced by reset voltage, oxide layer thickness, filament size, and filament resistivity. The simulation results of the present investigation can be beneficial for the optimization of RRAM devices

Resistive Switching Property of Bmim(Br) Ionic Liquid under the Influence of ZnO Nanorods

The majority of the research work in the area of resistive switching has been carried out with the help of organic, inorganic and hybrid materials. Only a few reports investigate resistive switching properties of ionic liquid and soft materials. In this report, we have synthesized ZnO nanorods (NRs) and Bmim(Br) ionic liquid using simple and low-temperature chemical route i.e., hydrothermal and reflux method, respectively. The structural study of ZnO NRs indicates that the formation of hexagonal crystal structure, evident from the XRD pattern. The FESEM image suggested the formation of nanorods like morphology. The effect of dispersed ZnO NRs on the resistive switching behavior of Bmim(Br) ionic liquid was studied. The study explains the change in switching behavior by dispersing the different concentrations of ZnO NRs in ionic liquid. The results demonstrated that the dispersed ZnO NRs in ionic liquid plays a vital role and will be a potential active switching material for resistive switching applications

Korea-U.S. trade negotiation on market access: dispute over the Korean shelf-life regulations for food products

This study questions the salient variables in the settlement of trade disputes arising from the market access problem between Korea and the United States. An examination of previous research on Korea-U.S. trade disputes finds that no single research approach provided a complete explanation of them. Examination of the bilateral negotiations left some unexplained 'black boxes.' This study therefore develops a synthesised framework for analysis that combines distinct levels of analysis: state power (structural); institutional frameworks (the state); and lobby groups (public choice). Furthermore, it operationalises the new framework for analysis by identifying the following three variables within the trade dispute between the two countries: negotiation power, government trade agencies, and interest groups. Part I outlines the historical evolution of the economic relations of the two countries in the context of the way in which the relations have changed over the years. This section provides the theoretical framework for the following case study. * Part II traces the negotiation process of the case in greater detail. It begins with a brief account of the case. It shows the basic positions of the four actors involved in the case: the two main interest groups and the two governments. Subsequent chapters respectively trace the negotiations under the informal diplomatic process, Section 301 procedure, and the WTO dispute settlement procedure. Particular attention is given to the interactions between the actors in the bilateral negotiation process as well as in the domestic process of each country. The deadlocks and success of the negotiations are analysed in the context of the three variables. The case analysis finds that all the three variables influenced the process and outcomes of the negotiations, and further shows the basic mechanism of the interrelationship of the variables. This study concludes that in order to gain a clearer picture of Korea-U.S. market access disputes, it is necessary to see them at least through the different angles of the three variables. Based on this conclusion, this study proposes some policy alternatives to strengthen the negotiation power of Korea