Biomorph actuators composed of two layers with asymmetric thermal expansion properties are widely explored owing to their high mechanical adaptability. Electrothermal nanomaterials are employed as the Joule heating components in them for controlled thermal expansion, while their large integration thickness often limits resulting actuation performances. This study reports high‐performance ultrathin soft biomorph actuators enabled by near atom‐thickness 2D platinum ditelluride (PtTe2) layers—a new class of emergent metallic 2D transition metal dichalcogenides. The actuators employ wafer‐scale 2D PtTe2layers sandwiched in between two polymer films of largely mismatched thermal expansion coefficients, which are electrically biased to generate Joule heating. This electrical‐to‐thermal conversion causes the asymmetric expansion of the polymers achieving outstanding actuation motions; i.e., large bending curvature, fast responsiveness, as well as high reversibility and endurance, which surpass the performances of previously explored graphene‐based actuators with much smaller dimensions. Furthermore, the 2D PtTe2layers‐enabled actuators are demonstrated to function as soft grippers in lifting and relocating heavier objects, implying the great potential of near atom‐thickness materials in biomimetic devices.
- Award ID(s):
- 1728309
- NSF-PAR ID:
- 10274631
- Date Published:
- Journal Name:
- Nanoscale
- Volume:
- 12
- Issue:
- 19
- ISSN:
- 2040-3364
- Page Range / eLocation ID:
- 10647 to 10655
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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Abstract -
null (Ed.)2D PtTe 2 layers, a relatively new class of 2D crystals, have unique band structure and remarkably high electrical conductivity promising for emergent opto-electronics. This intrinsic superiority can be further leveraged toward practical device applications by merging them with mature 3D semiconductors, which has remained largely unexplored. Herein, we explored 2D/3D heterojunction devices by directly growing large-area (>cm 2 ) 2D PtTe 2 layers on Si wafers using a low-temperature CVD method and unveiled their superior opto-electrical characteristics. The devices exhibited excellent Schottky transport characteristics essential for high-performance photovoltaics and photodetection, i.e. , well-balanced combination of high photodetectivity (>10 13 Jones), small photo-responsiveness time (∼1 μs), high current rectification ratio (>10 5 ), and water super-hydrophobicity driven photovoltaic improvement (>300%). These performances were identified to be superior to those of previously explored 2D/3D or 2D layer-based devices with much smaller junction areas, and their underlying principles were confirmed by DFT calculations.more » « less
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Abstract Two-dimensional (2D) transition metal dichalcogenide (2D TMD) layers present an unusually ideal combination of excellent opto-electrical properties and mechanical tolerance projecting high promise for a wide range of emerging applications, particularly in flexible and stretchable devices. The prerequisite for realizing such opportunities is to reliably integrate large-area 2D TMDs of well-defined dimensions on mechanically pliable materials with targeted functionalities by transferring them from rigid growth substrates. Conventional approaches to overcome this challenge have been limited as they often suffer from the non-scalable integration of 2D TMDs whose structural and chemical integrity are altered through toxic chemicals-involved processes. Herein, we report a generic and reliable strategy to achieve the layer-by-layer integration of large-area 2D TMDs and their heterostructure variations onto a variety of unconventional substrates. This new 2D layer integration method employs water only without involving any other chemicals, thus renders distinguishable advantages over conventional approaches in terms of material property preservation and integration size scalability. We have demonstrated the generality of this method by integrating a variety of 2D TMDs and their heterogeneously-assembled vertical layers on exotic substrates such as plastics and papers. Moreover, we have verified its technological versatility by demonstrating centimeter-scale 2D TMDs-based flexible photodetectors and pressure sensors which are difficult to fabricate with conventional approaches. Fundamental principles for the water-assisted spontaneous separation of 2D TMD layers are also discussed.
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Two dimensional (2D) materials such as graphene and transition metal dichalcogenides (TMDs) are promising for optical modulation, detection, and light emission since their material properties can be tuned on-demand via electrostatic doping1–21. The optical properties of TMDs have been shown to change drastically with doping in the wavelength range near the excitonic resonances22–26. However, little is known about the effect of doping on the optical properties of TMDs away from these resonances, where the material is transparent and therefore could be leveraged in photonic circuits. Here, we probe the electro-optic response of monolayer TMDs at near infrared (NIR) wavelengths (i.e. deep in the transparency regime), by integrating them on silicon nitride (SiN) photonic structures to induce strong light -matter interaction with the monolayer. We dope the monolayer to carrier densities of (7.2 ± 0.8) × 1013 cm-2, by electrically gating the TMD using an ionic liquid [P14+] [FAP-]. We show strong electro-refractive response in monolayer tungsten disulphide (WS2) at NIR wavelengths by measuring a large change in the real part of refractive index ∆n = 0.53, with only a minimal change in the imaginary part ∆k = 0.004. We demonstrate photonic devices based on electrostatically gated SiN-WS2 phase modulator with high efficiency ( ) of 0.8 V · cm. We show that the induced phase change relative to the change in absorption (i.e. ∆n/∆k) is approximately 125, that is significantly higher than the ones achieved in 2D materials at different spectral ranges and in bulk materials, commonly employed for silicon photonic modulators such as Si and III-V on Si, while accompanied by negligible insertion loss. Efficient phase modulators are critical for enabling large-scale photonic systems for applications such as Light Detection and Ranging (LIDAR), phased arrays, optical switching, coherent optical communication and quantum and optical neural networks27–30.more » « less
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Abstract 2D transition metal dichalcogenide (TMD) layered materials are promising for future electronic and optoelectronic applications. The realization of large‐area electronics and circuits strongly relies on wafer‐scale, selective growth of quality 2D TMDs. Here, a scalable method, namely, metal‐guided selective growth (MGSG), is reported. The success of control over the transition‐metal‐precursor vapor pressure, the first concurrent growth of two dissimilar monolayer TMDs, is demonstrated in conjunction with lateral or vertical TMD heterojunctions at precisely desired locations over the entire wafer in a single chemical vapor deposition (VCD) process. Owing to the location selectivity, MGSG allows the growth of p‐ and n‐type TMDs with spatial homogeneity and uniform electrical performance for circuit applications. As a demonstration, the first bottom‐up complementary metal‐oxide‐semiconductor inverter based on p‐type WSe2and n‐type MoSe2is achieved, which exhibits a high and reproducible voltage gain of 23 with little dependence on position.
- Free Publicly Accessible Full Text
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Accepted Manuscript1.0
- Journal Article:
- https://doi.org/10.1039/D0NR01845G
