We have grown vertically ZnO nanorods (NRs) doped with Cu and Ni to modulate their electronic properties. The wurtzite structure of the ZnO NRs was confirmed from the top-view field emission scanning ...electron microscopy (FESEM) and atomic force microscopy (AFM) images as well as X-ray diffraction (XRD) spectra, and the phase purity was confirmed by Raman spectroscopy. The NRs exhibit high texture orientation in the (002) and (100) directions of the Ni- and Cu-doped ZnO NRs, respectively. This structural modification significantly modulates their electronic properties. Scanning tunneling spectroscopy (STS) and corresponding density of states (DOS) measurements were employed to determine the electronic band gap and band-edge shift of the doped ZnO NRs. Ambient-processed semitransparent CsPbBr3 perovskite solar cells (PSCs) were fabricated with the device structure (FTO/ZnO seed layer/ZnO NRs:CsPbBr3/Spiro-MeOTAD/ITO) using these NRs as the electron transport layer (ETL). The Ni-doped ZnO NR samples were found to be very good in electrical conductivity with a low electronic band gap, which yielded a device power conversion efficiency (PCE) of 4.94% under ambient conditions. Thus, Ni-doped ZnO NRs could be used as an efficient low-cost and ambient-processed one-dimensional ETL in the fabrication of optoelectronic devices.
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.
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.
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).
Two-dimensional (2D) van der Waals (vdW) materials with lower symmetry (triclinic, monoclinic or orthorhombic) exhibit intrinsic anisotropic in-plane structure desirable for future optoelectronic ...surface operating devices. Herein, we report one such material, 2D \(p\)-type semiconductor germanium sulfide (GeS), a group IV monochalcogenide with puckered orthorhombic morphology, in which in-plane optical and transport properties can be correlated with its electronic structure. We systematically investigate the electronic band structure of the bulk GeS with micro-focused angle-resolved photoemission spectroscopy (\(\mu\)-ARPES) and correspond the charge transport properties using the field-effect transistor (FET) device architecture, and optical anisotropy \(via\) angle-resolved polarization dependent Raman spectroscopy (ARPRS) on a micron-sized rectangle-shaped exfoliated bulk flake. The experimental valence band dispersion along the two high symmetry directions indicate highly anisotropic in-plane behavior of the charge carrier that agrees well with the density functional theory (DFT) calculations. In addition, we demonstrate the variation of the in-plane hole mobility (ratio \(\sim\) 3.4) from the electrical conductivity with gate-sweep in a GeS-on-SiO\(_2\) FET. Moreover, we use the angle-resolved fluctuation of the Raman intensity of the characteristic phonon modes to precisely determine the armchair and zigzag edges of the particular flake. The unique structural motif of GeS with correlated electronic and optical properties are of great interest both for the physical understanding of the all-optical switch and their applications in memory devices.
The study investigates the influence of negative capacitance on the transfer characteristics of vdW FETs on the heterophase of CIPS ferroelectric. Notably, a less pronounced NC resulting from the ...spatial distribution of the ferroelectric and paraelectric phases plays crucial role in stabilizing of n-channel-conductance. This results into the emergence of a non-volatile logic state, between the two binary states of TFETs. Concerned study proposed NC-TFETs based on ferroionic crystals as promising devices for generating a stable logic state below Vth.
