ZnO Nanoribbons Research Articles

Deep-Level Transient Spectroscopy Studies on Four Different Zinc Oxide Morphologies

In this work, we described the variations in the defect energy levels of four different ZnO morphologies, namely nanoribbons, nanorods, nanoparticles, and nanoshuttles. All the ZnO morphologies were grown on a seeded 4% Boron-doped p-type silicon (p-Si) wafer by using two different synthesis techniques, which are chemical bath deposition and microwave-assisted methods. The defect energy levels were analyzed by using the Deep-Level Transient Spectroscopy (DLTS) characterization method. The DLTS measurements were performed in the 123 K to 423 K temperature range. From the DLTS spectra, we found the presence of different trap-related defects in the synthesized ZnO nanostructures. We labeled all the traps related to the four different ZnO nanostructures as P1, P2, P3, P4, and P5. We discussed the presence of defects by measuring the activation energy (Ea) and capture cross-section (α). The lowest number of defect energy levels was exhibited by the ZnO nanorods at 0.27 eV, 0.18 eV, and 0.75 eV. Both the ZnO nanoribbons and nanoparticles show four traps, which have energies of 0.31 eV, 0.23 eV, 0.87 eV, and 0.44 eV and 0.27 eV, 0.22 eV, 0.88 eV, and 0.51 eV, respectively. From the DLTS spectrum of the nanoshuttles, we observe five traps with different activation energies of 0.13 eV, 0.28 eV, 0.25 eV, 0.94 eV, and 0.50 eV. The DLTS analysis revealed that the origin of the nanostructure defect energy levels can be attributed to Zinc vacancies (Vzn), Oxygen vacancies (Vo), Zinc interstitials (Zni), Oxygen interstitials (Oi), and Zinc antisites (Zno). Based on our analysis, the ZnO nanorods showed the lowest number of defect energy levels compared to the other ZnO morphologies.

Design and analysis of ZnO nanoribbon for sodium ion batteries (SIBs)

Design and analysis of ZnO nanoribbon for sodium ion batteries (SIBs)

Adjustable electronic structure and magnetism of ZnO nanoribbons by applying an electric field

The electronic characteristics and magnetism of nitrogen passivated armchair ZnO nanoribbons (NA8ZnONRs) by applying an electric field were analyzed using the DFT method at the LDA+U level. The outcomes suggest that intrinsic armchair ZnO nanoribbons (A8ZnONRs) are nonmagnetic semiconductors. After nitrogen passivation, NA8ZnONRs display ferromagnetism, whose magnetism (3.21 μB) primarily derives from spin polarization of p orbital electrons of passivated N atoms (2.56 μB) and boundary O atoms (0.69 μB). By applying X-axis electric field, A8ZnONRs still exhibit ferromagnetism, and magnetism primarily derives from the spin-splitting polarization of p orbital electrons of boundary O atoms and passivated N atoms.

Selective edge hydrogenated armchair ZnO nanoribbons for negative differential resistance based nanoelectronic devices

Selective edge hydrogenated armchair ZnO nanoribbons for negative differential resistance based nanoelectronic devices

Electronic, magnetic and optical properties of zigzag ZnO nanoribbons under the coupling action of electric field and strains

The electronic, magnetic and optical properties of zigzag ZnO nanoribbons under electric field and strains are calculated using density functional theory. The results show that Z8-ZnONRs have ferromagnetism, which is mainly caused by the spin polarization of O atoms of O-terminated edge. Under the action of Y-axial electric field, the system has ferromagnetism, which is mainly contributed by O-2p and Zn-3d orbital electrons. Z8-ZnONRs have the characteristics of high-energy storage and low loss. The application of Y-axial electric field can enhance the absorption of visible light. The application of strains can adjust the electronic structures of Z8-ZnONRs and the system remains magnetic. Which mainly comes from the contribution of O atoms of O-terminated edge. The results show that the coupling of electric field and strains makes the system change from ferromagnetic metal to magnetic semiconductor.

Planar Quasi-1D Nano-Interconnects Based on Selective Edge Passivated ZnO Nanoribbons

Planar Quasi-1D Nano-Interconnects Based on Selective Edge Passivated ZnO Nanoribbons

Carcinogenic Heavy Metals Detection Based on ZnO Nanoribbons

The theoretical investigation of zigzag ZnONRs for the detection of carcinogenic heavy metal atoms is reported in the current manuscript. The sensing characteristics of the ZnONRs towards toxic heavy metal atoms are examined by deploying the density functional theory (DFT) calculations together with non-equilibrium Green’s function (NEGF). The variation in the structural, electronic, and transport properties of the ZnONRs post passivation with heavy metal atoms at the edges are considered for the detection. Pristine ZnONR is a semiconductor with an energy bandgap of 0.49 eV and the ZnONRs become metallic after exposure to heavy metal atoms. The quantum transport calculations reveal the enhanced current conductivity in the heavy metal atom exposed ZnONR devices relative to the pristine ZnONR due to the induced metallicity. The local device density of states (LDOS) calculations reveal the major transmission of the carriers occurs through the edges. The ZnONR devices are highly sensitive to Sb and As as compared to the Pb atom. The ZnONR exhibit the highest sensitivity towards the Sb atoms with the sensor response around 3.57 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\times \,\,{10}^{{7}}$ </tex-math></inline-formula> %. The sensor sensitivity towards the As and Pb is slightly lower with the sensor responses measured to be 3.52 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\times \,\,10^{{7}}$ </tex-math></inline-formula> % and 2.86 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\times \,\,10^{{7}}$ </tex-math></inline-formula> %, respectively. Further, FET devices exhibit high sensitivity at zero gate bias voltage of the order of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$10^{{10}}$ </tex-math></inline-formula> for Sb-ZnO-Sb, As-ZnO-As, and <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$10^{{9}}$ </tex-math></inline-formula> for Pb-ZnO-Pb devices. The obtained findings suggest that ZnONRs can effectively be used for the detection of carcinogenic heavy metal atoms.

Detection of carcinogenic heavy metals using ZnO nanoribbons (ZnONRs): Ab-initio analysis

The present work investigates the behaviour of ZnO nanoribbons (ZnONRs) for the detection of carcinogenic heavy metals. Density functional theory along with non-equilibrium Green’s function are used to analyse the ZnO nanoribbons sensing behaviour towards the heavy metal atoms. The heavy metal atoms are passivated at the edges of the ZnO nanoribbons and the change in the structural, electronic, and transport properties are examined for the detection of such heavy metals. Heavy metal passivation at O-rich edge changes the electronic bandgap while the passivation at Zn-rich edge changes the structure behaviour from semiconducting to metallic. The electronic transport results reveal the current magnitude is enhanced upon the heavy metal atom passivation. The current starts conducting after a certain bias voltage irrespective of the device configuration due to semiconducting electrodes . Transmission eigenstates report the electron transport in the passivated devices is mainly from the opposite edge. Zn-rich edge passivated devices have higher magnitudes of current as more carriers are flowing through the O-rich edge due to higher electronegativity of oxygen. From the sensitivity calculations, the Zn-rich passivated devices are reported to exhibit higher sensitivity towards the heavy metal atoms. The obtained results define the efficiency of the ZnONRs towards the design of heavy metal sensors. • Carcinogenic heavy metal atoms detection using ZnO nanoribbons (ZnONRs) is presented. • O-rich edge passivation changes the electronic bandgap. • Zn-rich edge passivation changes the structure from semiconducting to metallic. • Zn-rich edge passivated devices have higher magnitudes of current. • Zn-rich edge passivated devices have higher sensitivity towards the heavy metal atoms.

Spin dependent Electronic properties of NO-adsorbed zigzag ZnO nanoribbons: A DFT Study

Exploring novel nano-materials for designing the robust and efficient sensors is an area of immense potential. In the present work, we study the adsorption of NO molecules at the edges of zigzag ZnO nanoribbons (zZnONR). The adsorption of NO molecules was modelled at the edges of zZnONR in different possibilities. It is well known that pristine (H-passivated) zZnONR is a semi-conducting material. Present calculations reveal that NO-adsorption takes place via N-side and a semiconductor to metallic-transition is also witnessed in all configurations. The obtained adsorption energies are found to vary between -4.10 eV to -7.04 eV ensuring the exothermic nature of the adsorption process and energetic feasibility of the considered configurations. Interestingly, all the considered structures (with NO adsorption) prefer magnetic ground state in contrast to previously reported non-magnetic behaviour of pristine zZnONR. Furthermore, NO adsorption at both the edges makes the structure half-metallic. In contrast, rest of the two-configurations are pure metallic. Present findings indicate that zZnONR could play a vital role towards NO detection as well realizing the spintronic properties for other various other technological applications.

First-principles study of CO adsorption on zigzag ZnO nanoribbons towards nanosensor application

The efficient detection of toxic gases and development of compact, low dimensional sensors is the center of research activities in the past two decades. In this direction, here we gauged the potential of monatomic thick zigzag ZnO (zZnO) nanoribbons towards the sensing of most abundant toxic gas i.e. CO. The adsorption of CO molecules on zZnO nanoribbons (zZnONR) has been studied in different possible ways. It is revealed that electronic and transport properties of zZnONR are affected by the interaction of CO molecules. Moreover, it is noticed that CO molecules always bond with the nanoribbons edges through the C-side and adsorption takes place via formation of a stable chemical bond. The transport properties reveal a peculiar behavior that the current magnitude is significantly higher when CO adsorption happens at O-edge. Furthermore, the maximum current is obtained when CO is adsorbed at both the edges of ribbon. Our findings show that selective configurations of CO adsorption are helpful for the designing of nano sensors with considerably lower recovery time.

Biosensing Properties of Zinc Oxide Nanoribbons Toward Creatine: A First-Principles Study

In this paper, a nanostructured solid-state biosensor is proposed for the non-enzymatic detection of creatine as a possible stimulus for skeletal/cardiac muscle hypertrophy. Phonon dispersion curve reveals that two-dimensional honeycomb-like ZnO nanostructure applied here has true local minima. Sensing properties of the device toward creatine are theoretically studied by employing first-principles density functional theory associated with non-equilibrium Green&#x2019;s function formalism. For this purpose, a two-probe configuration has been constructed based on ZnO nanoribbon to calculate and assess the adsorption energy, charge transfer, electron transmission probability, current through the sensing device, and its sensitivity taking pristine and creatine-adsorbed ZnO nanoribbon into account. Representation of total and local density of states substantiates strong chemisorption of the carboxyl/imine-ended creatine with the nanoribbon edge/center through n/p-type conduction in conjunction with the adsorption energy of -2.424 eV/-2.292 eV and charge transfer of <inline-formula> <tex-math notation="LaTeX">$0.521 \vert \text{e}\vert $ </tex-math></inline-formula>/-<inline-formula> <tex-math notation="LaTeX">$0.011 \vert \text{e}\vert $ </tex-math></inline-formula>, respectively. The adsorption strength of 1&#x00B0; and 3&#x00B0; amine-ended creatine directed toward the nanoribbon surface is intermediate, with slightly more incline to its center. The current flow is calculated by integrating the transmission probability of electrons in an energy window for both pristine and creatine-adsorbed structures; subsequently, the normalized current difference is featured as the sensing device response with the maximum value of 1184.33&#x0025; under an applied bias of 2 V for the optimal adsorption configuration.

Fluorinated Zigzag ZnO Nanoribbons for Negative Differential Resistance-Based Nanoelectronic Devices: First-Principles Investigation

Fluorinated Zigzag ZnO Nanoribbons for Negative Differential Resistance-Based Nanoelectronic Devices: First-Principles Investigation

First-principles study of structural and electronic properties of cove-edged zigzag ZnO nanoribbons

ZnO is a wide band gap material that exhibits particular applications in opto-electronic devices. Nanowires, nanotubes, and two-layer thick layers of ZnO have already been synthesized. It is known that bare zigzag ZnO (zZnO) nanoribbons are metallic in nature with a ferromagnetic ground state. In contrast, H-passivated zZnO nanoribbons are non-magnetic in nature. In zZnO nanoribbons, one edge is entirely made up of Zn atoms while there are only O atoms on its opposite edge. In the present work, we investigated the effect of defects (cove-edges) on the structural and electronic properties of zZnO nanoribbons. Various possible configurations were considered which include (a) cove-edge at O side (ZnO-cv) (b) cove-edge at Zn side (cv-ZnO) (c) cove-edge at both the sides (cv-ZnO-cv) (d) Zn-edge is H-passivated while O-edge is coved (H-ZnO-cv) (e) O-edge is H-passivated while Zn-edge is coved (cv-ZnO-H). The introduction of cove-defects affects the structural and electronic properties of zZnO nanoribbons in a significant manner. The binding energy analysis shows that all of these structures are exothermic and energetically feasible to be obtained. Moreover, the energetic feasibility is proportional to the ribbon width. Present findings revealed that ZnO-Cv is a zero-band gap semi-metal similar to graphene whereas, Cv-ZnO and Cv-ZnO-Cv exhibit pure metallic character.

Self-passivated edges of ZnO nanoribbons: a global search.

The edge structure of two-dimensional (2D) materials plays a critical role in controlling their growth kinetics and morphological evolution, electronic structures and functionalities. However, until now, the accurate edge reconstruction of ZnO nanoribbons remains absent. Here, we present results of a global search of ZnO edge structures having used the CALYPSO program combined with the density functional theory (DFT) method. In addition to a database of all the possible edge reconstructed structures of ZnO nanoribbons, the most stable edge reconstructed structures of armchair (ZnOAC), O-enriched zigzag (OZZ) and Zn-enriched zigzag edges (ZnZZ) have been confirmed based on molecular dynamics (MD) simulation and bonding configuration analysis of atoms near the edges. The edge formation energies show that their stabilities depend on the chemical potential (μO) and the concentrations (ρO) of oxygen atoms. Interestingly, a highly stable ZnZZ edge exhibits a novel nanotube-like structure and metallic characteristics, while the most stable reconstructed OZZ edge, resembling the letter "T", exhibits a narrow direct band-gap. It is almost certain that their electronic properties are determined by the edge states.

Ab Initio Modeling of the ZnO-Cu(111) Interface

The morphology at the catalytically active interfacial site of ZnO/Cu in the commercial ZnO/Cu/Al2O3 catalyst for CO2 hydrogenation to methanol is still an open question. In the present study, we employ ab initio density functional theory based methods to gain insight into the structure of the ZnO-Cu interface by investigating the morphology of supported ZnO nano-ribbons at the interface with the Cu(111) surface in the presence of hydrogen and water molecules. We find that the stabilities of free-standing ZnO nano-ribbons get enhanced when they are supported on the Cu(111) surface. These supported nano-ribbons are further stabilized by the adsorption of hydrogen atoms on the top of O atoms of the nano-ribbons. Interestingly, the hydrogenated nano-ribbons are found to be equally stable and they appear to be an array of independent chains of ZnOH motifs, suggesting that the hydrogenated nano-ribbons are structurally fluxional. The edge of these fluxional nano-ribbons is stabilized via a triangular reconstruction with a basic composition of Zn6O7H7 in the presence of water molecules. Such a triangular structure gets further stabilized when it is attached to a bulk-like part of the ZnO/Cu(111) system. Furthermore, we find that the triangular reconstruction is energetically favorable even at the methanol synthesis conditions. Therefore, we propose that, under methanol synthesis conditions, the motif Zn6O7H7 represents a stable form at the interface between the bulk-like part of ZnO and the Cu(111) surface in the ZnO/Cu/Al2O3 based commercial catalyst.

Nitrogen doped armchair ZnO nanoribbons for potential rectification applications: DFT analysis

This work investigates the structural, electronic, and transport properties of pristine and N-doped armchair ZnO nanoribbons (ZnONRs) using density functional theory (DFT) in combination with non-equilibrium Green's function (NEGF). It is reported here that the N atom doping at the O atom site slightly reduces the binding energy (E b ) and it also decreases band gap (E g ). For 9-atom width, the pristine structures are most stable with a binding energy of −4.961 eV and a band gap of 2.012 eV. Additionally, the Fermi energy level in doped ZnONRs lies near the valence band thereby induces the p-type characteristics. The transport properties of the two-terminal devices have also been examined. These devices exhibit asymmetric I–V characteristics leading to the rectification phenomenon. Relative to the pristine device, N-doped devices demonstrated improved I–V characteristics. Interestingly, the N-doped two-terminal devices exhibit a higher rectification ratio (RR) in contrast to the pristine device. Similar characteristics are observed for the devices irrespective of width. For the 9-atom width ZnONR devices with N doped at the edge and center positions demonstrate significantly high RR of about 4.54 × 10 8 and 1.56 × 10 8 at 1.35 V and 1.0 V bias points, respectively. With such enhanced rectification characteristics, ZnONRs can be used as potential candidates for future nanoelectronic switching devices. • The structural, electronic, and transport properties of pristine and N-doped armchair ZnONRs have been investigated here. • The N atom doping at the O atom site slightly reduces the E b and it also decreases E g . • The Fermi energy level in doped ZnONRs lies near the valence band thereby induces the p-type characteristics. • N-doped two-terminal devices exhibit a higher RR. • For 9-ZnONR devices with N doped at the edge and center positions, significantly high RR is of the order of 10 8 .

Disconnected N-doped zigzag ZnO nanoribbon for potential Negative Differential Resistance (NDR) applications

Quantum coherence and non-equilibrium statistics are the governing mechanisms for electronic transport in 2-D materials. The present work investigates the electronic transport properties of pristine and N-doped disconnected zigzag ZnO nanoribbons (Z-ZnONRs) using density functional theory (DFT) framework along with non-equilibrium Green’s function (NEGF). Interestingly, even though the structures are disconnected, still they exhibit electron transport. These ZnONRs disconnected structures can act as two probe devices by deploying the tunneling mechanism for electron transport. It is reported that the tunneling current decreases with an increase in the disconnected distance between the two considered Z-ZnONR structures. Further, negative differential resistance (NDR) characteristics are observed in all the considered configurations. Moreover, the N atom doping is also studied at the disconnected edges. N-dopant position affects the I–V characteristics based on the dopant sites. Zn-rich edge dopant induces NDR across a wide range while O-rich edge dopant induces linear I–V behavior with lower NDR characteristics. The highest NDR peak-to-valley current ratio is reported around 5.6 ×104 within the 0.15 V bias region. The structure with N doped at both edges and disconnected distance as 0.5 Å exhibited dominant NDR behavior. This finds their potential use in the design of oscillators, switches, rectifiers, amplifiers, frequency converters, detectors, and resonator circuits, etc.

Impedance spectroscopy of nanostructured ZnO morphologies

In this study, four nanostructured ZnO morphologies, nanoribbons, nanorods, nanoparticles, and nanoshuttles, were synthesized at annealing temperatures of 300 °C, 500 °C, and 700 °C. Structural properties were studied by Scanning Electron Microscopy (SEM), Transmission Electron Microscopy (TEM), X-ray Diffraction Spectroscopy (XRD), and Differential Scanning Calorimetry (DSC). Optical properties were analyzed by UV–Visible Spectroscopy and Photoluminescence (PL). Electrical transport properties were studied by the Cole–Cole plot technique and electrical resistivity. From the impedance spectroscopy analysis, we extracted the carrier lifetime, the RC time constant, and grain and grain boundary parameters in each morphology. We observed that resistance decreased with increasing temperature in all samples in general, while nanorods, nanoshuttles, and nanoribbons showed well-defined semicircle profiles due to grain and grain boundaries at higher temperatures. From wettability studies, we obtained that surface with ZnO nanoparticles has hydrophobic properties, while nanorods, nanoribbons, and nanoshuttles resulted in a superhydrophobic surface. The optimum ZnO nanomorphology based on impedance studies can be used for developing electrodes for dye-sensitized solar cells.

Ultra dynamic water repellency and anti-icing performance of superhydrophobic ZnO surface on the printed circuit board (PCB)

Forming superhydrophobic surface (SPS) is an effective way for anti-icing materials in the field of electronic packaging. In this paper, ZnO nanoribbons, regular hexagonal columns, nanowires and irregular hexagonal columns SPS were fabricated by using the Zn(NO3)2, ZnSO4, Zn(Ac)2 and ZnCl2 as zinc sources, respectively. The results show that the ZnO nanoribbons SPS has the longest delayed icing time (16225 s) at temperature of −5℃when compared with other three SPSs. But the anti-icing ability of the ZnO nanoribbons SPS was significantly reduced with the decreasing temperature. This work offers a practical application for enhancing anti-icing ability of Cu-based PCB in electronic packaging.

Nanoscale design of 1D metal oxides derived from mixed Ni-MH battery/transition metal dust

Controllable recycling of End-of-life rechargeable nickel-metal hydride (Ni-MH) batteries and by-products of steelmaking to added-value functional nanostructures is desired but challenging. The present work introduces an innovative and high-yield microrecycling strategy to simultaneous synthesis of TM alloy (i.e., Ni-based superalloy) and RE oxide (REO) nanostructures from obsolete Ni-MH batteries mixed with zinc-rich electric arc furnace dust (EAFD). This strategy involves integration of high-temperature thermal isolation followed by thermal nanowiring techniques. The impure thermally-isolated REOs were purified and transformed into one dimensional (1D) nanorods of hybrid REOs. Besides, during high-temperature thermal isolation, defect-rich ZnO with tailored structures of nanorods and nanoribbons were fabricated using controllable vapour deposition. The electrochemical performance of ZnO nanoribbons for oxygen evolution reaction (OER) revealed a considerable overpotential reduction of 131 mV (18%) compared to pure commercial nano-ZnO. This approach is transformational in providing a scalable and cost-effective pathway to facilitate recycling of the challenging, yet critical, waste materials into functional nanostructures for energy and environmental applications.