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Impact of Substrate Characteristics on Stretchable Polymer Semiconductor Behavior
摘要： Stretchable conductive polymer films are required to survive not only large tensile strain but also stay functional after the reduction in applied strain. In the deformation process, the elastomer substrate that is typically employed plays a critical role in the response of the polymer film. In this study, we examine the role of a PDMS elastomer substrate on the ability to achieve stretchable PDPP-4T films. Specifically, we consider the adhesion and near surface modulus of the PDMS tuned through UV/ozone treatment on the competition between film wrinkling and plastic deformation. We also consider the role of PDMS tension on the stability of films under cyclic strain. We find that increasing the near-surface modulus of the PDMS and maintaining the PDMS in tension throughout the cyclic strain process promotes plastic deformation over film wrinkling. In addition, the UV/ozone treatment increases film adhesion to the PDMS resulting in significantly reduced film folding and delamination. For 20 min UV/ozone treated PDMS, we show that a PDPP-4T film RMS roughness is consistently below 3 nm for up to 100 strain cycles with a strain range of 40 %. In addition, while the film is plastically deforming, the microstructural order is largely stable as probed with grazing incidence X-ray scattering and UV-visible spectroscopy. These results highlight the importance of the neighboring elastomer characteristics on the ability to achieve stretchable polymer semiconductors.
关键词： Yield strain,Stretchable electronics,Deformability,Polymer semiconductors,Adhesion energy
更新于2025-09-23 15:23:52
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Adhesion Behavior between Multilayer Graphene and Semiconductor Substrates
摘要： 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.
关键词： adhesion force,bonding mechanism,adhesion energy,exfoliation behavior,MEMS/NEMS,molecular dynamics,graphene
更新于2025-09-23 15:19:57
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Adhesion of Single-walled Carbon Nanotube Thin Films with Different Materials
摘要： Single-walled carbon nanotubes (SWCNTs) possess extraordinary physical and chemical properties. Thin films of randomly oriented SWCNTs have great potential in many opto-electro-mechanical applications. However, good adhesion of SWCNT films with a substrate material is pivotal for their practical use. Here, for the first time we systematically investigate the adhesion properties of SWCNT thin films with commonly used substrates such as glass (SiO2), indium tin oxide (ITO), crystalline silicon (C-Si), amorphous silicon (a-Si:H), zirconium oxide (ZrO2), platinum (Pt), polydimethylsiloxane (PDMS), and SWCNTs for self-adhesion using atomic force microscopy. By comparing the results obtained in air and inert Ar atmospheres we observed a great contribution of the surface state of the materials on their adhesion properties. We found that the SWCNT thin films have higher adhesion in an inert atmosphere. The adhesion in the air can be greatly improved by a fluorination process. Experimental and theoretical analyses suggest that adhesion depends on the atmospheric conditions and surface functionalization.
关键词： adhesion energy,inert atmosphere,Single-walled carbon nanotubes,fluorination,ambient conditions,thin films
更新于2025-09-12 10:27:22