We report a combined experimental and theoretical study on the formation of dumbbell silicene structures on Ag(110). High-resolution scanning tunneling microscopy (STM) reveals a rich tapestry of adatom-free and -decorated bidimensional silicene phases covering the whole Ag(110) surface. The most thermodynamically stable silicene models obtained from densityfunctional theory (DFT) perfectly reproduce all features observed by STM. These phases correspond to different Si buckled honeycomb reconstructions ((13´4), c(18´4) and c(8´4)) composed of two periodic motifs common to all structural models. DFT calculations show that these reconstructions are stabilized by the presence of ordered arrays of Si adatoms adsorbed on top of silicene in a dumbbell configuration. Grazing incidence X-ray diffraction (GIXD) measurements confirm the growth of a dumbbell silicene layer. The structure factor values are well reproduced by a (13´4) model with 4 Si adatoms per unit cell and a slight distortion of the hexagonal unit cell. Our STM-DFT-GIXD study demonstrates the formation of dumbbell silicene, a theoretically predicted two-dimensional Si allotrope. This opens up perspectives for tuning the peculiar properties of silicene.
for converting ionic signals into electronic ones thanks to the unique property of organic mixed ionic-electronic conductors (OMIECs). [4] Ionic concentration from an analyte or ionic currents from electroactive cells can be efficiently sensed/probed and amplified, thus making OECTs attractive sensors. [5] In the perspective of neuromorphic engineering, the same devices are capitalizing on the possibility to engineer devices where ion-electron coupling can be used to implement various synaptic plasticities, from short-term to long-term memory effects. [3,[6][7][8][9] These two aspects have been so far mostly developed independently from each other. In contrast, synapses in biology are combining sensing capabilities with plastic properties to provide some essential aspects of biocomputing. Through their adaptation properties, synapses are enhancing/depressing relevant/irrelevant signals from neurons. They also provide a rich set of non-linear operations to process the spike signals from neural cells. [10] As sensors, synapses are converting chemical signals from sensed neurotransmitters into transduced post-synaptic electric signals as ionic concentration modulation. Such ambivalence existing in biology is the natural example of a non-Von Neumann computing architecture that embeds highly complex biochemical sensing at all nodes in its network, and demonstrates reciprocally the power of the local adaptation of a sensing array that programs according to its environment.In this paper, we show how OECTs can combine these two important features for bio-signal sensing and processing. The corner stone of OECTs behavior is the transconductance, which couples ionic signals to electronic ones. [11] Transconductance can be well described by the coupling between: i) volumetric ionic capacitance allowing for a very large effective surface of interaction between the analyte and the polymer; and ii) efficient electronic transport along the π-conjugated organic chains. Several works have demonstrated routes for optimizing transconductance through either volumetric capacitance or electronic mobility tuning. [12,13] Notably, side-chain engineering on the conductive backbone of the polymer have been recently proposed as a promising chemical engineering route. [14] Here, we show how electropolymerization can be used to adapt post-fabrication of these two intrinsic parameters of OECTs (i.e., volumetric capacitance and electronic mobility) and how this technique Organic electrochemical transistors are considered today as a key technology to interact with a biological medium through their intrinsic ionic-electronic coupling. In this paper, the authors show how this coupling can be finely tuned (in operando) post-microfabrication via the electropolymerization technique. This strategy exploits the concept of adaptive sensing where both transconductance and impedance are tunable and can be modified on-demand to match different sensing requirements. Material investigation through Raman spectroscopy, atomic force microscopy, and scanning ele...
Hybrid van der Waals heterostructures based on 2D materials and/or organic thin films are being evaluated as potential functional devices for a variety of applications. In this context, the graphene/organic semiconductor (Gr/OSC) heterostructure could represent the core element to build future vertical organic transistors based on two back-to-back Gr/OSC diodes sharing a common graphene sheet, which functions as the base electrode. However, the assessment of the Gr/OSC potential still requires a deeper understanding of the charge carrier transport across the interface as well as the development of wafer-scale fabrication methods. This work investigates the charge injection and transport across Au/OSC/Gr vertical heterostructures, focusing on poly(3-hexylthiophen-2,5-diyl) as the OSC, where the PMMA-free graphene layer functions as the top electrode. The structures are fabricated using a combination of processes widely exploited in semiconductor manufacturing and therefore are suited for industrial upscaling. Temperature-dependent current−voltage measurements and impedance spectroscopy show that the charge transport across both device interfaces is injection-limited by thermionic emission at high bias, while it is space charge limited at low bias, and that the P3HT can be assumed fully depleted in the high bias regime. From the space charge limited model, the out-of-plane charge carrier mobility in P3HT is found to be equal to μ ≈ 2.8 × 10 −4 cm 2 V −1 s −1 , similar to the in-plane mobility reported in previous works, while the charge carrier density is N 0 ≈ 1.16 × 10 15 cm −3 , also in agreement with previously reported values. From the thermionic emission model, the energy barriers at the Gr/P3HT and Au/P3HT interfaces result in 0.30 eV and 0.25 eV, respectively. Based on the measured barriers heights, the energy band diagram of the vertical heterostructure is proposed under the hypothesis that P3HT is fully depleted.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.