Tuning the ambipolar behavior in charge carrier transport via defect-engineering is crucial for achieving high mobility transistors for nonlinear logic circuits. Here, we present the electric-field ...tunable electron and hole transport in a microchannel device consisting of highly air-stable van der Waals (vdW) noble metal dichalcogenide (NMDC), PdSe2, as an active layer. Pristine bulk PdSe2 constitutes Se surface vacancy defects created during the growth or exfoliation process and offers ambipolar transfer characteristics with a slight electron dominance recorded in field-effect transistor (FET) characteristics showing an ON/OFF ratio <10 and electron mobility ∼21 cm2/(V·s). However, transfer characteristics of PdSe2 can be tuned to a hole-dominated transport while using hydrochloric acid (HCl) as a p-type dopant. On the other hand, the chelating agent EDTA, being a strong electron donor, enhances the electron-dominance in PdSe2 channel. In addition, p-type behavior with a 100 times higher ON/OFF ratio is obtained while cooling the sample down to 10 K. Low-temperature angle-resolved photoemission spectroscopy resembles the p-type band structure of PdSe2 single crystal. Also, first principle density functional theory calculations justify the tunability observed in PdSe2 as a result of defect-engineering. Such a defect-sensitive ambipolar vdW architecture may open up new possibilities toward future CMOS (Complementary Metal-Oxide-Semiconductor) device fabrications and high performance integrated circuits.
Herein, the anisotropic magnetic properties of 2D van der Waals (vdW) insulator, chromium oxychloride (CrOCl), are presented. Temperature‐dependent bulk magnetization reveals a paramagnetic to ...antiferromagnetic phase transition at ≈14 K (Néel temperature, TN) while cooling. From the magnetic field‐dependent magnetization study (M–H) at low temperature, a first‐order field‐induced (at or above 40 kOe) metamagnetic transition from antiferromagnetic to ferrimagnetic state has been observed. Noticeably, switching of the easy plane (ab‐plane) of the magnetization to the c‐axis can be identified above 29 kOe. Moreover, in the vicinity of TN, under an applied magnetic field, magnetic entropy change (ΔSM) can be estimated as 4.31 J kg−1 K−1 for H//c. The results evoke further experiments on charge/spin transport properties of few‐layer CrOCl in the nanoelectronic circuit framework for understanding the connection between crystallographic deformation and metamagnetism.
2D van der Waals (vdW) magnetic insulator, chromium oxychloride (CrOCl), reveals a paramagnetic to antiferromagnetic phase transition at ≈14 K (Néel temperature, TN) while cooling. A first‐order field‐induced (at or above 40 kOe) metamagnetic transition along with switching of the easy plane (ab‐plane) of the magnetization to the c‐axis can be identified above 29 kOe.
Abstract Induced magnetic order in a topological insulator (TI) can be realized either by depositing magnetic adatoms on the surface of a TI or engineering the interface with epitaxial thin film or ...stacked assembly of 2D van der Waals (vdW) materials. Herein, the observation of spin‐phonon coupling in the otherwise non‐magnetic TI Bi 2 Te 3 is reported, due to the proximity of FePS 3 (an antiferromagnet (AFM), T N ≈ 120 K), in a vdW heterostructure framework. Temperature‐dependent Raman spectroscopic studies reveal deviation from the usual phonon anharmonicity originated from spin‐lattice coupling at the Bi 2 Te 3 /FePS 3 interface at/below 60 K in the peak position (self‐energy) and linewidth (lifetime) of the characteristic phonon modes of Bi 2 Te 3 (106 and 138 cm −1 ) in the stacked heterostructure. The Ginzburg‐Landau (GL) formalism, where the respective phonon frequencies of Bi 2 Te 3 couple to phonons of similar frequencies of FePS 3 in the AFM phase, is adopted to understand the origin of the hybrid magneto‐elastic modes. At the same time, the reduction of characteristic T N of FePS 3 from 120 K in isolated flakes to 65 K in the heterostructure, possibly due to the interfacial strain, which leads to smaller Fe‐S‐Fe bond angles as corroborated by computational studies using density functional theory (DFT). Besides, inserting hexagonal boron nitride within Bi 2 Te 3 /FePS 3 stacking regains the anharmonicity in Bi 2 Te 3 . Controlling interfacial spin‐phonon coupling in stacked heterostructure can have potential application in surface code spin logic devices.
The emergence of organic-inorganic hybrid perovskites (OHPs) has revolutionised the potential performance of optoelectronic devices; most perovskites are opaque and hence incompatible with ...transparent optoelectronics and sensitive to environmental degradation. Here, we have reported a single-step fabrication of ultra-long MAPbI
3
perovskite microwire arrays over a large area using stencil lithography based on sequential vacuum sublimation. The environmental stability of MAPbI
3
is empowered with a newly designed and synthesized transparent supramolecular self-assembly based on a mixture of two tripodal
l
-Phe-C
11
H
23
/C
7
F
15
molecules, which showed a contact angle of 105° and served as ultra-hydrophobic passivation layers for more than 45 days in an ambient atmosphere. The MAPbI
3
microwire arrays passivated with the supramolecular self-assembly demonstrated for the first time both excellent transparency of ∼89% at 550 nm and a remarkable photoresponse with a photo-switching ratio of ∼10
4
, responsivity of 789 A W
−1
, detectivity of 10
14
Jones, linear dynamic range of ∼122 dB, and rise time of 432 μs. Furthermore, the photodetector fabricated on a flexible PET substrate demonstrated robust mechanical flexibility even beyond 1200 bending cycles. Therefore, the scalable stencil lithography and supramolecular passivation approaches have the potential to deliver next-generation transparent, flexible, and stable optoelectronic devices.
Fully transparent perovskite microwire arrays passivated with supramolecular assembly for stable and high-performance photodetectors.
Manipulation of long-range order in 2D van der Waals (vdW) magnetic materials (e.g., CrI
, CrSiTe
,etc.), exfoliated in few-atomic layer, can be achieved via application of electric field, ...mechanical-constraint, interface engineering, or even by chemical substitution/doping. Usually, active surface oxidation due to the exposure in the ambient condition and hydrolysis in the presence of water/moisture causes degradation in magnetic nanosheets that, in turn, affects the nanoelectronic /spintronic device performance. Counterintuitively, the current study reveals that exposure to the air at ambient atmosphere results in advent of a stable nonlayered secondary ferromagnetic phase in the form of Cr
Te
(T
≈160 K) in the parent vdW magnetic semiconductor Cr
Ge
Te
(T
≈69 K). The coexistence of the two ferromagnetic phases in the time elapsed bulk crystal is confirmed through systematic investigation of crystal structure along with detailed dc/ac magnetic susceptibility, specific heat, and magneto-transport measurement. To capture the concurrence of the two ferromagnetic phases in a single material, Ginzburg-Landau theory with two independent order parameters (as magnetization) with a coupling term can be introduced. In contrast to the rather common poor environmental stability of the vdW magnets, the results open possibilities of finding air-stable novel materials having multiple magnetic phases.
We map spatially correlated electrical current on the stacking boundaries of pristine and doped hexagonal boron nitride (hBN) to distinguish from its insulating bulk via conductive atomic force ...microscopy (CAFM). While the pristine edges of hBN show an insulating nature, the O-doped edges reveal a current 2 orders of higher even for bulk layers where the direct transmission through tunnel barrier is implausible. Instead, the nonlinear current–voltage characteristics (I–V) at the edges of O-doped hBN can be explained by trap-assisted lowering of the tunnel barrier by adopting a Poole–Frenkel (PF) model. However, in the stacked heterostructure with multilayer graphene (MLG) on top, the buried edge of pristine hBN shows a signature of electron conduction in the scanning mode which contradicts the first-principle calculation of spatial distribution of local density of states (LDOS) data. Enhancement of friction between the Pt-tip and MLG at the step-edge of the heterostructure while scanning in the contact mode has prompted us to construct a phenomenological model where the localization of opposite surface charges on two conducting plates (MLG and Si substrate) containing a dielectric film (hBN) with negatively charged defects creates an internal electric field opposite to the external electric field due to the applied voltage bias in the CAFM setup. An equivalent circuit with a parallel resistor network based on a vertical conducting channel through the MLG/hBN edge and an in-plane surface carrier transport through MLG can successfully analyze the current maps on pristine/doped hBN and the related heterostructures. These results yield fundamental insight into the emerging field of insulatronics in which defect-induced electron transport along the edge can be manipulated in an 1D–2D synergized insulator.
The emergence of organic-inorganic hybrid perovskites (OHPs) has revolutionised the potential performance of optoelectronic devices; most perovskites are opaque and hence incompatible with ...transparent optoelectronics and sensitive to environmental degradation. Here, we have reported a single-step fabrication of ultra-long MAPbI3 perovskite microwire arrays over a large area using stencil lithography based on sequential vacuum sublimation. The environmental stability of MAPbI3 is empowered with a newly designed and synthesized transparent supramolecular self-assembly based on a mixture of two tripodal l-Phe-C11H23/C7F15 molecules, which showed a contact angle of 105° and served as ultra-hydrophobic passivation layers for more than 45 days in an ambient atmosphere. The MAPbI3 microwire arrays passivated with the supramolecular self-assembly demonstrated for the first time both excellent transparency of ∼89% at 550 nm and a remarkable photoresponse with a photo-switching ratio of ∼104, responsivity of 789 A W-1, detectivity of 1014 Jones, linear dynamic range of ∼122 dB, and rise time of 432 μs. Furthermore, the photodetector fabricated on a flexible PET substrate demonstrated robust mechanical flexibility even beyond 1200 bending cycles. Therefore, the scalable stencil lithography and supramolecular passivation approaches have the potential to deliver next-generation transparent, flexible, and stable optoelectronic devices.
The emergence of organic–inorganic hybrid perovskites (OHPs) has revolutionised the potential performance of optoelectronic devices; most perovskites are opaque and hence incompatible with ...transparent optoelectronics and sensitive to environmental degradation. Here, we have reported a single-step fabrication of ultra-long MAPbI3 perovskite microwire arrays over a large area using stencil lithography based on sequential vacuum sublimation. The environmental stability of MAPbI3 is empowered with a newly designed and synthesized transparent supramolecular self-assembly based on a mixture of two tripodal l-Phe-C11H23/C7F15 molecules, which showed a contact angle of 105° and served as ultra-hydrophobic passivation layers for more than 45 days in an ambient atmosphere. The MAPbI3 microwire arrays passivated with the supramolecular self-assembly demonstrated for the first time both excellent transparency of ∼89% at 550 nm and a remarkable photoresponse with a photo-switching ratio of ∼104, responsivity of 789 A W−1, detectivity of 1014 Jones, linear dynamic range of ∼122 dB, and rise time of 432 μs. Furthermore, the photodetector fabricated on a flexible PET substrate demonstrated robust mechanical flexibility even beyond 1200 bending cycles. Therefore, the scalable stencil lithography and supramolecular passivation approaches have the potential to deliver next-generation transparent, flexible, and stable optoelectronic devices.
One-dimensional (1D) van der Waals (vdW) materials offer nearly defect-free
strands as channel material in the field-effect transistor (FET) devices and
probably, a better interconnect than ...conventional copper with higher current
density and resistance to electro-migration with sustainable down-scaling. We
report a new halide based "truly" 1D few-chain atomic thread, PdBr$_2$,
isolable from its bulk which crystallizes in a monoclinic space group C2/c.
Liquid phase exfoliated nanowires with mean length (20$\pm$1)$\mu$m transferred
onto SiO$_2$/Si wafer with a maximum aspect ratio of 5000 confirms the lower
cleavage energy perpendicular to chain direction. Moreover, an isolated
nanowire can also sustain current density of 200 MA/cm$^\mathrm{2}$ which is
atleast one-order higher than typical copper interconnects. However, local
transport measurement via conducting atomic force microscopy (CAFM) tip along
the cross direction of the single chain records a much lower current density
due to the anisotropic electronic band structure. While 1D nature of the
nanoobject can be linked with non-trivial collective quantum behavior, vdW
nature could be beneficial for the new pathways in interconnect fabrication
strategy with better control of placement in an integrated circuit (IC).
