scholarly journals Adhesion Behavior between Multilayer Graphene and Semiconductor Substrates

2018 ◽  
Vol 8 (11) ◽  
pp. 2107 ◽  
Author(s):  
Qi Zhang ◽  
Xin Ma ◽  
Yulong Zhao
Keyword(s):  
Critical Velocity ◽  
Bonding Strength ◽  
Energy Levels ◽  
Mechanical Systems ◽  
Semiconductor Surface ◽  
Multilayer Graphene ◽  
Adhesion Forces ◽  
Micro Electro Mechanical Systems ◽  
Graphene Layers ◽  
Topmost Layer

A high bonding strength between graphene and a semiconductor surface is significant to the performance of graphene-based Micro-Electro Mechanical Systems/Nano-Electro Mechanical Systems (MEMS/NEMS) devices. In this paper, by applying a series of constant vertical upward velocities (Vup) to the topmost layer of graphene, the exfoliation processes of multilayer graphene (one to ten layers) from an Si semiconductor substrate were simulated using the molecular dynamics method, and the bonding strength was calculated. The critical exfoliation velocities, adhesion forces, and adhesion energies to exfoliate graphene were obtained. In a system where the number of graphene layers is two or three, there are two critical exfoliation velocities. Graphene cannot be exfoliated when the Vup is lower than the first critical velocity, although the total number of graphene layers can be exfoliated when the Vup is in the range between the first critical velocity and second critical velocity. Only the topmost layer can be exfoliated to be free from the Si surface if the applied Vup is greater than the second critical velocity. In systems where the number of graphene layers is four to ten, only the topmost layer can be free and exfoliated if the exfoliation velocity is greater than the critical velocity. It was found that a relatively low applied Vup resulted in entire graphene layers peeling off from the substrate. The adhesion forces of one-layer to ten-layer graphene systems were in the range of 25.04 nN–74.75 nN, and the adhesion energy levels were in the range of 73.5 mJ/m2–188.45 mJ/m2. These values are consistent with previous experimental results, indicating a reliable bond strength between graphene and Si semiconductor surfaces.

scholarly journals Effect of the External Velocity on the Exfoliation Properties of Graphene from Amorphous SiO2 Surface

Crystals ◽  
2021 ◽  
Vol 11 (4) ◽  
pp. 454
Author(s):  
Qi Zhang ◽  
Xing Pang ◽  
Yulong Zhao
Keyword(s):  
External Action ◽  
Atomic Scale ◽  
Monolayer Graphene ◽  
Multilayer Graphene ◽  
Amorphous Sio2 ◽  
Sio2 Substrate ◽  
Graphene Layers ◽  
Upward Velocity ◽  
Topmost Layer ◽  
Critical Velocities

External action has a significant influence on the formation of high-quality graphene and the adhesion of graphene on the surface of the MEMS/NEMS device. The atomic-scale simulation and calculation can further study the exfoliation process of graphene by external actions. In multilayer graphene systems where graphene layers were simulated weakly contacted with SiO2 substrate, a constant vertical upward velocity (Vup) was applied to the topmost layer. Then two critical velocities were found, and three kinds of distinct exfoliation processes determined by critical upward velocities were observed in multilayer graphene systems. The first critical velocities are in the range of 0.5 Å/ps–3.18 Å/ps, and the second critical velocities are in the range of 9.5 Å/ps–12.1 Å/ps. When the Vup is less than the first critical velocity, all graphene layers will not be exfoliated. When Vup is between the first and second critical Vup, all layers can be exfoliated almost synchronously at last. When Vup is larger than the second critical Vup, the topmost layer can be exfoliated alone, transferring energy to the underlying layers, and the underlying layers are slowly exfoliated. The maximum exfoliation force to exfoliate the topmost layer of graphene is 3200 times larger than that of all graphene layers. Moreover, it is required 149.26 mJ/m2 to get monolayer graphene from multilayers, while peeling off all layers without effort. This study explains the difficulty to get monolayer graphene and why graphene falls off easily during the transfer process.

Relations of Microstructure, Piezoelectricity, and Surface Forces at Nanoscale

2007 ◽  
Author(s):  
Hyungoo Lee ◽  
Rodrigo Cooper ◽  
Bartosz Mika ◽  
Hong Liang
Keyword(s):  
Polyvinylidene Fluoride ◽  
Polymer Surface ◽  
Electrical Potential ◽  
Mechanical Systems ◽  
Adhesion Forces ◽  
Surface Adhesion ◽  
Micro Electro Mechanical Systems ◽  
Friction Forces ◽  
Β Phase ◽  
Dipole Structure

In small devices such as micro-electro-mechanical systems (MEMS) and nano-electro-mechanical systems (NEMS), adhesion and friction forces make them less reliable with unacceptable performance [1]. These forces need to be completely understood to make advances in the systems. In our previous research, it has been proven that using a functional material, polyvinylidene fluoride (PVDF), both stiction and friction could be modified or turned on-off. The phase of the polymer affects the adhesion and friction forces. β phase contents reduced the adhesion forces due to its less electrostatic forces. With higher phase difference, higher roughness of the polymer surface got higher friction forces. In this research, we continue our investigation in understanding microstructure aspects of the PVDF, its dipole structure, and piezoelectricity on surface adhesion and friction. Doing so, we used an atomic force microscope (AFM) with an external potential to study the piezeoelectrical behavior. The effects of the electrical potential on adhesion and friction force were tested. It was shown that when the electrical potential increases, the surface roughness increases under the AFM, however not with a profilometer. Changes were also found in adhesion. This paper discusses the mechanisms of nanoscale adhesion and friction of the PVDF with an AFM tip along with the microstructures and dipole structures. This article contributes to understanding in fundamental adhesion and friction forces at a nanometer length scale.

Optical phase modulators using deformable waveguides actuated by micro-electro-mechanical systems

2011 ◽  
Vol 36 (7) ◽  
pp. 1089 ◽  
Author(s):  
Wei-Chao Chiu ◽  
Chun-Che Chang ◽  
Jiun-Ming Wu ◽  
Ming-Chang M. Lee ◽  
Jia-Min Shieh
Keyword(s):  
Mechanical Systems ◽  
Micro Electro Mechanical Systems ◽  
Optical Phase ◽  
Phase Modulators ◽  
Optical Phase Modulators

scholarly journals Wash Testing of Electronic Yarn

Materials ◽  
2020 ◽  
Vol 13 (5) ◽  
pp. 1228 ◽  
Author(s):  
Dorothy Anne Hardy ◽  
Zahra Rahemtulla ◽  
Achala Satharasinghe ◽  
Arash Shahidi ◽  
Carlos Oliveira ◽  
...  
Keyword(s):  
Research Group ◽  
Copper Wire ◽  
Mechanical Systems ◽  
Consumer Products ◽  
Temperature Sensing ◽  
Micro Electro Mechanical Systems ◽  
Acoustic Sensing ◽  
Protective Polymer ◽  
Wash Durability

Electronically active yarn (E-yarn) pioneered by the Advanced Textiles Research Group of Nottingham Trent University contains a fine conductive copper wire soldered onto a package die, micro-electro-mechanical systems device or flexible circuit. The die or circuit is then held within a protective polymer packaging (micro-pod) and the ensemble is inserted into a textile sheath, forming a flexible yarn with electronic functionality such as sensing or illumination. It is vital to be able to wash E-yarns, so that the textiles into which they are incorporated can be treated as normal consumer products. The wash durability of E-yarns is summarized in this publication. Wash tests followed a modified version of BS EN ISO 6330:2012 procedure 4N. It was observed that E-yarns containing only a fine multi-strand copper wire survived 25 cycles of machine washing and line drying; and between 5 and 15 cycles of machine washing followed by tumble-drying. Four out of five temperature sensing E-yarns (crafted with thermistors) and single pairs of LEDs within E-yarns functioned correctly after 25 cycles of machine washing and line drying. E-yarns that required larger micro-pods (i.e., 4 mm diameter or 9 mm length) were less resilient to washing. Only one out of five acoustic sensing E-yarns (4 mm diameter micro-pod) operated correctly after 20 cycles of washing with either line drying or tumble-drying. Creating an E-yarn with an embedded flexible circuit populated with components also required a relatively large micro-pod (diameter 0.93 mm, length 9.23 mm). Only one embedded circuit functioned after 25 cycles of washing and line drying. The tests showed that E-yarns are suitable for inclusion in textiles that require washing, with some limitations when larger micro-pods were used. Reduction in the circuit’s size and therefore the size of the micro-pod, may increase wash resilience.

Micro-spectrophotometer based on micro electro-mechanical systems technology

2008 ◽  
Vol 3 (1) ◽  
pp. 37-43
Author(s):  
Lianqun Zhou ◽  
Yihui Wu ◽  
Ping Zhang ◽  
Ming Xuan ◽  
Zhenggang Li ◽  
...  
Keyword(s):  
Mechanical Systems ◽  
Micro Electro Mechanical Systems

Load Monitoring of Aerospace Structures Using Micro-Electro-Mechanical Systems (MEMS)

2012 ◽  
Author(s):  
M. Martinez ◽  
B. Rocha ◽  
M. Li ◽  
G. Shi ◽  
A. Beltempo ◽  
...  
Keyword(s):  
Least Squares ◽  
Mechanical Systems ◽  
National Research Council ◽  
Micro Electro Mechanical Systems ◽  
Displacement Estimation ◽  
Polynomial Fit ◽  
Load Monitoring ◽  
Variable Displacement ◽  
Displacement Transducers ◽  
Spatial Locations

The National Research Council of Canada has developed Structural Health Monitoring (SHM) test platforms for load and damage monitoring, sensor system testing and validation. One of the SHM platform consists of two 2.25 meter long, simple cantilever aluminium beams that provide a perfect scenario for evaluating the capability of a load monitoring system to measure bending, torsion and shear loads. In addition to static and quasi-static loading procedures, these structures can be fatigue loaded using a realistic aircraft usage spectrum while SHM and load monitoring systems are assessed for their performance and accuracy. In this study, Micro-Electro-Mechanical Systems (MEMS), consisting of triads of gyroscopes, accelerometers and magnetometers, were used to compute changes in angles at discrete stations along the structure. A Least Squares based algorithm was developed for polynomial fitting of the different data obtained from the MEMS installed in several spatial locations of the structure. The angles obtained from the MEMS sensors were fitted with a second, third and/or fourth order degree polynomial surface, enabling the calculation of displacements at every point. The use of a novel Kalman filter architecture was evaluated for an accurate angle and subsequent displacement estimation. The outputs of the newly developed algorithms were then compared to the displacements obtained from the Linear Variable Displacement Transducers (LVDT) connected to the structures. The determination of the best Least Squares based polynomial fit order enabled the application of derivative operators with enough accuracy to permit the calculation of strains along the structure. The calculated strain values were subsequently compared to the measurements obtained from reference strain gauges installed at different locations on the structure. This new approach for load monitoring was able to provide accurate estimates of applied strains and loads.

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