Optimization of Bilayer Lift-Off Process to Enable the Gap Size of 1μm Using LOR 3A and S1813

Bilayer lift-off process for 1μm feature size is demonstrated using LOR 3A and S1813 photoresist. The thickness of photoresists was fixed, whereas development time is varied. The process was further investigated by measuring the undercut depth and undercut rate by scanning electron microscopy. An optimized and reproducible recipe is provided

Inkjet Printing of Graphene

The optimization of inkjet printing graphene using a Fujifilm Dimatix Inkjet printer, is described in this study. The number of printing passes were varied, and relatively uniform lines were obtained. The printing parameter considerations and optimized printing parameters for graphene are also discussed

Ultrahigh-strength multi-layer graphene-coated Ni film with interface-induced hardening

Graphene-reinforced metal matrix composites exhibit excellent mechanical properties owing to dislocation impedance at the metal-graphene interface. Graphene coated on metal with composites fabricated using powder sintering can be applied as high-strength thin films across various fields (e.g., microelectromechanical systems, flexible electronics). In this study, a bilayer composite of multilayer graphene (MLG)-coated Ni is synthesized using the chemical vapor deposition (CVD) and transfer methods; mechanical properties are investigated using nanoindentation methods. MLG-coated Ni synthesized by CVD exhibits 195% and 470% increases in hardness and Young's modulus, respectively, compared with single-layer Ni. In contrast, the Young modulus and hardness of MLG-coated Ni synthesized via the transfer method can be estimated using the rule of mixture for composite materials. Transmission electron microscopy (TEM) shows that in MLG-coated Ni synthesized by CVD, dislocations are dense and evenly distributed compared with that synthesized by the transfer method, leading to its high mechanical strength. Molecular dynamics (MD) simulations demonstrate that interface-induced hardening is effective in graphene-coated Ni(111) with a strongly coupled interface. Therefore, ultrahigh-strength MLG-coated metal films can be obtained by manipulating the interface property between the MLG and metal, offering the potential for use as a thin film resistor against external force. (C) 2021 Elsevier Ltd. All rights reserved.

Confocal laser scanning microscopy as a real-time quality-assessment tool for industrial graphene synthesis

For the industrial quality control (QC) of the chemical vapor deposition (CVD) graphene, it is essential to develop a method to screen out unsatisfactory graphene films as efficiently as possible. However, previously proposed methods based on Raman spectroscopy or optical imaging after chemical etching are unable to provide non-invasive and fast analysis of large-area graphene films as grown on Cu foil substrates. Here we report that the reflection mode of confocal laser scanning microscopy (CLSM) provides a high-contrast image of graphene on Cu, enabling the real-time evaluation of the coverage and quality of graphene. The reflectance contrast,Rc, was found to be dependent on the incident laser wavelength, of which the maximum was obtained at 405 nm. In addition,Rcdecreases with increasing defect density of graphene. The dependence ofRcon the graphene's quality and laser wavelengths were explained by the tight-binding model calculation based on the Fresnel's interference formula. Thus, we believe that the reflection mode CLSM would be a very powerful quality-assessment tool for the mass production of CVD graphene films grown on Cu.

Graphene Quantum Dots from Carbonized Coffee Bean Wastes for Biomedical Applications

Recent studies concerning graphene quantum dots (GQDs) focus extensively on their application in biomedicine, exploiting their modifiable optical properties and ability to complex with various molecules via pi-pi or covalent interactions. Among these nascent findings, the potential therapeutic efficacy of GQDs was reported against Parkinson's disease, which has to date remained incurable. Herein, we present an environmentally friendly approach for synthesizing GQDs through a waste-to-treasure method, specifically from coffee waste to nanodrug. Consistent with the previous findings with carbon fiber-derived GQDs, the inhibitory effects of coffee bean-derived GQDs demonstrated similar effectiveness against abnormal alpha-synuclein fibrillation and the protection of neurons from relevant subcellular damages. The fact that a GQDs-based nanodrug can be prepared from a non-reusable yet edible source illustrates a potential approach to convert such waste materials into novel therapeutic agents with minimal psychological rejection by patients.

Stacking-Specific Reversible Oxidation of Bilayer Graphene

We report, for the first time, that the oxidation of bilayer graphene (BLG) can be reversibly and stacking-specifically controlled. The infrared (IR) absorption, IR nanoscopy, and Raman spectroscopy measurements on BLG consistently show reversible changes in the spectra and images upon exposure to O-2 and H-2 at elevated temperatures. We also obtain spectroscopic and theoretical evidence that stacking orders of graphene layers have a profound influence on the oxide structures: AB-BLG reacting with singlet and triplet oxygen results in endoperoxides (-C-O-O-C-), whereas AA'-BLG reacting with oxygen generates both the epoxides (singlet, -C-O-C-) and endoperoxides (triplet). We believe that our result provides deeper understanding on the layer-dependent catalytic activities of graphene, which is crucial for the design of high-performance graphene-based catalysts needed for various electrochemical, biological, and environmental applications.11Nsciescopu