| 1. |
- Han, Sang Sub, et al.
(author)
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Reversible Transition of Semiconducting PtSe2 and Metallic PtTe2 for Scalable All-2D Edge-Contacted FETs
- 2024
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In: Nano Letters. - : American Chemical Society (ACS). - 1530-6984 .- 1530-6992. ; 24:6, s. 1891-1900
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Journal article (peer-reviewed)abstract
- Two-dimensional (2D) transition metal dichalcogenide (TMD) layers are highly promising as field-effect transistor (FET) channels in the atomic-scale limit. However, accomplishing this superiority in scaled-up FETs remains challenging due to their van der Waals (vdW) bonding nature with respect to conventional metal electrodes. Herein, we report a scalable approach to fabricate centimeter-scale all-2D FET arrays of platinum diselenide (PtSe2) with in-plane platinum ditelluride (PtTe2) edge contacts, mitigating the aforementioned challenges. We realized a reversible transition between semiconducting PtSe2 and metallic PtTe2 via a low-temperature anion exchange reaction compatible with the back-end-of-line (BEOL) processes. All-2D PtSe2 FETs seamlessly edge-contacted with transited metallic PtTe2 exhibited significant performance improvements compared to those with surface-contacted gold electrodes, e.g., an increase of carrier mobility and on/off ratio by over an order of magnitude, achieving a maximum hole mobility of similar to 50.30 cm(2) V-1 s(-1) at room temperature. This study opens up new opportunities toward atomically thin 2D-TMD-based circuitries with extraordinary functionalities.
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| 2. |
- Han, Sang Sub, et al.
(author)
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Wafer-Scale Anion Exchange Conversion of Nonlayered PtS Films to van der Waals Two-Dimensional PtTe2 Layers with Negative Photoresponsiveness
- 2022
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In: Chemistry of Materials. - : American Chemical Society (ACS). - 0897-4756 .- 1520-5002. ; 34:15, s. 6996-7005
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Journal article (peer-reviewed)abstract
- This study reports on the controlled vapor-phase anion exchange conversion of three-dimensional (3D) platinum(II) sulfide (PtS) thin films to two-dimensional platinum ditelluride (2D PtTe2) van der Waals (vdW) layers. The low temperature (i.e., 400 ?) thermal tellurization of chemical vapor deposition (CVD)-grown PtS thin films leads to the formation of 2D PtTe2 vdW layers with a modulated crystallographic orientation, i.e., a mixture of horizontally and vertically oriented 2D layers. This chemical conversion enables the tunable electrical transport accompanying semiconducting-to-metallic transition as well as negative photoresponsiveness in the 2D PtTe2 layers. Density functional theory (DFT) calculations verify the thermodynamic principle for the conversion in the frame of free energy landscapes. The present work suggests a new chemical route for controlling the atomic and chemical structures of 2D transition metal dichalcogenides (TMDs) toward their wafer-scale modulation of electrical and opto-electrical properties.
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| 3. |
- Han, Sang Sub, et al.
(author)
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Peel-and-Stick Integration of Atomically Thin Nonlayered PtS Semiconductors for Multidimensionally Stretchable Electronic Devices
- 2022
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In: ACS Applied Materials and Interfaces. - : American Chemical Society (ACS). - 1944-8244 .- 1944-8252. ; 14:17, s. 20268-20279
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Journal article (peer-reviewed)abstract
- van der Waals (vdW) crystals with unparalleled electromechanical properties have been explored for transformative devices. Currently, the availability of 2D vdW crystals is rather limited in nature as they are only obtained from certain mother crystals with intrinsically possessed layered crystallinity and anisotropic molecular bonding. Recent efforts to transform conventionally non-vdW three-dimensional (3D) crystals into ultrathin 2D-like structures have seen rapid developments to explore device building blocks of unique form factors. Herein, we explore a "peel-and-stick" approach, where a nonlayered 3D platinum sulfide (PtS) crystal, traditionally known as a cooperate mineral material, is transformed into a freestanding 2D-like membrane for electromechanical applications. The ultrathin (???10 nm) 3D PtS films grown on large-area (>cm2) silicon dioxide/silicon (SiO2/Si) wafers are precisely "peeled" inside water retaining desired geometries via a capillary-force-driven surface wettability control. Subsequently, they are "sticked" on strain-engineered patterned substrates presenting prominent semiconducting properties, i.e., p-type transport with an optical band gap of ∼1.24 eV. A variety of mechanically deformable strain-invariant electronic devices have been demonstrated by this peel-and-stick method, including biaxially stretchable photodetectors and respiratory sensing face masks. This study offers new opportunities of 2D-like nonlayered semiconducting crystals for emerging mechanically reconfigurable and stretchable device technologies.
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| 4. |
- Wang, Mengjing, et al.
(author)
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Wafer-Scale Growth of 2D PtTe2 with Layer Orientation Tunable High Electrical Conductivity and Superior Hydrophobicity
- 2020
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In: ACS Applied Materials and Interfaces. - : American Chemical Society (ACS). - 1944-8244 .- 1944-8252. ; 12:9, s. 10839-10851
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Journal article (peer-reviewed)abstract
- Platinum ditelluride (PtTe2) is an emerging semimetallic two-dimensional (2D) transition-metal dichalcogenide (TMDC) crystal with intriguing band structures and unusual topological properties. Despite much devoted efforts, scalable and controllable synthesis of large-area 2D PtTe2 with well-defined layer orientation has not been established, leaving its projected structure–property relationship largely unclarified. Herein, we report a scalable low-temperature growth of 2D PtTe2 layers on an area greater than a few square centimeters by reacting Pt thin films of controlled thickness with vaporized tellurium at 400 °C. We systematically investigated their thickness-dependent 2D layer orientation as well as its correlated electrical conductivity and surface property. We unveil that 2D PtTe2 layers undergo three distinct growth mode transitions, i.e., horizontally aligned holey layers, continuous layer-by-layer lateral growth, and horizontal-to-vertical layer transition. This growth transition is a consequence of competing thermodynamic and kinetic factors dictated by accumulating internal strain, analogous to the transition of Frank–van der Merwe (FM) to Stranski–Krastanov (SK) growth in epitaxial thin-film models. The exclusive role of the strain on dictating 2D layer orientation has been quantitatively verified by the transmission electron microscopy (TEM) strain mapping analysis. These centimeter-scale 2D PtTe2 layers exhibit layer orientation tunable metallic transports yielding the highest value of ∼1.7 × 106 S/m at a certain critical thickness, supported by a combined verification of density functional theory (DFT) and electrical measurements. Moreover, they show intrinsically high hydrophobicity manifested by the water contact angle (WCA) value up to ∼117°, which is the highest among all reported 2D TMDCs of comparable dimensions and geometries. Accordingly, this study confirms the high material quality of these emerging large-area 2D PtTe2 layers, projecting vast opportunities employing their tunable layer morphology and semimetallic properties from investigations of novel quantum phenomena to applications in electrocatalysis.
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