Resistive switching (RS) is an interesting property shown by some materials systems that, especially during the last decade, has gained a lot of interest for the fabrication of electronic devices, with electronic nonvolatile memories being those that have received the most attention. The presence and quality of the RS phenomenon in a materials system can be studied using different prototype cells, performing different experiments, displaying different figures of merit, and developing different computational analyses. Therefore, the real usefulness and impact of the findings presented in each study for the RS technology will be also different. This manuscript describes the most recommendable methodologies for the fabrication, characterization, and simulation of RS devices, as well as the proper methods to display the data obtained. The idea is to help the scientific community to evaluate the real usefulness and impact of an RS study for the development of RS technology. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

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Recommended Methods to Study Resistive Switching Devices

The electrochemistry of graphene and its derivatives has been extensively researched in recent years. In the aspect of graphene preparation methods, the efficiencies of the top-down electrochemical exfoliation of graphite, the electrochemical reduction of graphene oxide and the electrochemical delamination of CVD grown graphene, are currently on par with conventional procedures. Electrochemical analysis of graphene oxide has revealed an unexpected inherent redox activity with, in some cases, an astonishing chemical reversibility. Furthermore, graphene modified with p-block elements has shown impressive electrocatalytic performances in processes which have been historically dominated by metal-based catalysts. Further progress has also been achieved in the practical usage of graphene in sensing and biosensing applications. This review is an update of our previous article in Chem. Soc. Rev. 2010, 39, 4146–4157, with special focus on the developments over the past two years.

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Graphene and its electrochemistry – an update

A method of etching a substrate is provided. The method of etching a substrate includes transferring a pattern into the substrate using a double patterned amorphous carbon layer on the substrate as a hardmask. Optionally, a non-carbon based layer is deposited on the amorphous carbon layer as a capping layer before the pattern is transferred into the substrate.

Techniques for the use of amorphous carbon (APF) for various etch and litho integration scheme

Top-down methods are of key importance for large-scale graphene and graphene oxide preparation. Electrochemical exfoliation of graphite has lately gained much interest because of the simplicity of execution, the short process time, and the good quality of graphene that can be obtained. Here, we test three different electrolytes, that is, H2 SO4 , Na2 SO4 , and LiClO4 , with a common exfoliation procedure to evaluate the difference in structural and chemical properties that result for the graphene. The properties are analyzed by means of scanning transmission electron microscopy (STEM), Raman spectroscopy, and X-ray photoelectron spectroscopy. We then tested the graphene materials for electrochemical applications, measuring the heterogeneous electron transfer (HET) rates with a Fe(CN)6 (3-/4-) redox probe, and their capacitive behavior in alkaline solutions. We correlate the electrochemical features with the presence of structural defects and oxygen functionalities on the graphene materials. In particular, the use of LiClO4 during the electrochemical exfoliation of graphite allowed the formation of highly oxidized graphene with a C/O ratio close to 4.0 and represents a possible avenue for the mass production of graphene oxide as valid alternative to the current laborious and dangerous chemical procedures, which also have limited scalability.

Electrochemically Exfoliated Graphene and Graphene Oxide for Energy Storage and Electrochemistry Applications.

Graphene is considered as one of the most promising materials in a wide range of applications because of its outstanding electronic, optical, thermal, and mechanical properties. Given its large specific surface area, two-dimensional structure, facile decoration, and high adsorption capacity, numerous graphene-based nanomaterials with unprecedented characteristics have been designed, prepared, and applied in catalysis. In this article, we first reviewed common synthetic methods to prepare graphene-based catalysts followed by critical comments and possible solutions. We then briefly summarized the characterization techniques that were relevant to catalysis applications and their applications in energy conversion, environmental protection, and several other typical fields. Finally, we discussed the challenges and opportunities for the future development of graphene-based nanomaterials in sustainable catalysis. This review provides key information to the catalysis community to design and fabricate graphene-ba...

Graphene-Based Nanomaterials for Catalysis

Integration of graphene with Si microelectronics is very appealing by offering a potentially broad range of new functionalities. New materials to be integrated with the Si platform must conform to stringent purity standards. Here, we investigate graphene layers grown on copper foils by chemical vapor deposition and transferred to silicon wafers by wet etching and electrochemical delamination methods with respect to residual submonolayer metallic contaminations. Regardless of the transfer method and associated cleaning scheme, time-of-flight secondary ion mass spectrometry and total reflection X-ray fluorescence measurements indicate that the graphene sheets are contaminated with residual metals (copper, iron) with a concentration exceeding 1013 atoms/cm2. These metal impurities appear to be partially mobile upon thermal treatment, as shown by depth profiling and reduction of the minority charge carrier diffusion length in the silicon substrate. As residual metallic impurities can significantly alter elect...

https://pubs.acs.org/doi/pdf/10.1021/acsnano.5b01261

Residual Metallic Contamination of Transferred Chemical Vapor Deposited Graphene

A MEMS acoustic transducer includes a substrate having a cavity therethrough, and a conductive back plate unit including a plurality of conductive perforated back plate portions which extend over the substrate cavity. A dielectric spacer arranged on the back plate unit between adjacent conductive perforated back plate portions, and one or more graphene membranes are supported by the dielectric spacer and extend over the conductive perforated back plate portions.

MEMS Acoustic Transducer, MEMS Microphone, MEMS Microspeaker, Array of Speakers and Method for Manufacturing an Acoustic Transducer

According to an embodiment, a composite wafer includes a carrier substrate having a graphite layer and a monocrystalline semiconductor layer attached to the carrier substrate.

Method for manufacturing a composite wafer having a graphite core, and composite wafer having a graphite core

Since 2004 the field of graphene research has attracted increasing interest worldwide Especially the integration of graphene into microelectronic devices has the potential for numerous applications Therefore, we summarize the current knowledge on this aspect Surveys show that considerable progress was made in the field of graphene synthesis However, the central issue consists of the availability of techniques suitable for production for the deposition of graphene on dielectric substrates Besides, the encapsulation of graphene for further processing while maintaining its properties poses a challenge Regarding the graphene/metal contact intensive research was done and recently substantial advancements were made towards contact resistances applicable for electronic devices Generally speaking the crucial issues for graphene integration are identified today and the corresponding research tasks can be clearly defined

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The integration of graphene into microelectronic devices.

Reduced graphene oxide (rGO) was investigated as a material for use in chemiresistive gas sensors. The carbon nanomaterial was transferred onto a silicon wafer with interdigital gold electrodes. Spin coating turned out to be the most reliable transfer technique, resulting in consistent rGO layers of reproducible quality. Fast changes in the electrical resistance at a low operating temperature of 85 °C could be detected for the gases NO2, CH4 and H2. Especially upon adsorption of NO2 the high signal changes allowed a minimum detection of 0.3 ppm (S/N = 3). To overcome the poor selectivity, rGO was chemically functionalized with octadecylamine, or modified by doping with metal nanoparticles such as Pd and Pt, and also metal oxides such as MnO2, and TiO2. The different response patterns for six different materials allowed the discrimination of all of the test gases by pattern recognition based on principal component analysis.

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Guenther Ruhl

Papers

Residual Metallic Contamination of Transferred Chemical Vapor Deposited Graphene

MEMS Acoustic Transducer, MEMS Microphone, MEMS Microspeaker, Array of Speakers and Method for Manufacturing an Acoustic Transducer

Method for manufacturing a composite wafer having a graphite core, and composite wafer having a graphite core

The integration of graphene into microelectronic devices.

Reduced graphene oxide and graphene composite materials for improved gas sensing at low temperature