Growth Of Nanoribbons Research Articles

Superatomic Layer of Cubic Mo4S4 Clusters Connected by Cl Cross-Linking.

Superatomic clusters - assemblies of atoms with various sizes, shapes, and compositions - can form hierarchical architectures that exhibit emergent electronic properties not found in their individual units. In particular, cubic M4X4 clusters of chalcogenides (M = transition metal; X = chalcogen) are recognized as versatile building blocks for 3D structures with tunable morphologies and electronic properties. However, tetrahedral M4X4 clusters rarely assemble into 2D architectures, which could offer a distinct class of functional materials from their 3D analogues. Here, this work reports the preparation of 2D Mo8S8Cl11, a superatomic layer with a sandwich structure consisting of Mo4S4 clusters interconnected through Cl cross-linking. The vapor-phase reaction inside nanotubes promotes the selective growth of Mo8S8Cl11 nanoribbons, allowing detailed characterization via transmission electron microscopy. This methodology can be applied to the growth of layered structures containing Mo8S8Cl11 at the micrometer scale. This work has demonstrated that mono- and few-layer Mo8S8Cl11 can be prepared by exfoliation of parent solids. Electronic structure calculations indicate that the 2D monolayer has quasi-flat bands, giving rise to an indirect-to-direct bandgap transition under mechanical strain. Furthermore, scanning electrochemical microscopy reveals the potential of the layered structures as highly efficient catalysts for the hydrogen-evolution reaction.

Graphene nanoribbons with hBN passivated edges grown by high-temperature molecular beam epitaxy

Integration of graphene and hexagonal boron nitride (hBN) in lateral heterostructures has provided a route to broadly engineer the material properties by quantum confinement of electrons or introduction of novel electronic and magnetic states at the interface. In this work we demonstrate lateral heteroepitaxial growth of graphene nanoribbons (GNRs) passivated by hBN using high-temperature molecular beam epitaxy (HT-MBE) to grow graphene in oriented hBN trenches formed ex-situ by catalytic nanoparticle etching. High-resolution atomic force microscopy (AFM) reveals that GNRs grow epitaxially from the etched hBN edges, and merge to form a GNR network passivated by hBN. Using conductive AFM we probe the nanoscale electrical properties of the nanoribbons and observe quasiparticle interference patterns caused by intervalley scattering at the graphene/hBN interface, which carries implications for the potential transport characteristics of hBN passivated GNR devices.

Molybdenum Disulfide Nanoribbons with Enhanced Edge Nonlinear Response and Photoresponsivity.

MoS2 nanoribbons have attracted increased interest due to their properties, which can be tailored by tuning their dimensions. Herein, the growth of MoS2 nanoribbons and triangular crystals formed by the reaction between films of MoOx (2<x<3)grown by pulsed laser deposition and NaF in a sulfur-rich environment is demonstrated. The nanoribbons can reach up to 10µm in length, and feature single-layeredges, forming a monolayer-multilayer junction enabled by the lateral modulation in thickness. The single-layer edges show a pronounced second harmonic generation due to the symmetry breaking, in contrast to the centrosymmetric multilayer structure, which is unsusceptible to the second-order nonlinear process. A splitting of the Raman spectra is observed in MoS2 nanoribbons arising from distinct contributions from the single-layer edges and multilayer core. Nanoscale imaging reveals a blue-shifted exciton emission of the monolayer edge compared to the isolated MoS2 monolayers due to built-in local strain and disorder. Wefurther report on an ultrasensitive photodetector made of a single MoS2 nanoribbon with a responsivity of 8.72×102 AW-1 at 532nm, among the highest reported up-to-date for single-nanoribbon photodetectors. These findings can inspire the design of MoS2 semiconductors with tunable geometries for efficient optoelectronic devices.

Molecular-Vapor-Assisted Low-Temperature Growth of Graphene Nanoribbons

Conventional on-surface synthesis under ultrahigh vacuum deposition has been used to synthesize various types of graphene nanoribbons (GNRs). The dehydrogenation reaction from a prepolymer to GNR requires catalysis with a metal substrate at high temperatures, which suffers from undesired side reactions that decompose introduced functional substituents during conversion to GNRs. To overcome these drawbacks, we have developed a new method, molecular-vapor-assisted low-temperature growth (MVLTG), based on a massive excess of gaseous hydrogen-accepting molecules (2,3-dichloro-5,6-dicyano-p-benzoquinone (DDQ) or oxygen) relative to the prepolymer on the metal surface. MVLTG reduces the GNR growth temperature of prepolymers with the Z-type precursor, 4′,5″-dibromo-1,1′:2′,1′:2″-quaterphenyl from 500 °C, used in conventional thermal annealing, to 350 °C. To investigate the reaction mechanism of MVLTG, a kinetic study using Raman spectroscopy to obtain GNR yields as a function of the hydrogen acceptor concentration and time was in good agreement with a simulation based on the gas-2D solid-state reaction model. These studies suggest a successful “Scholl reaction” in the gas phase, in which gaseous hydrogen acceptors (DDQ and oxygen) efficiently extract hydrogens from prepolymers at lower temperatures, converting them into GNRs. Additionally, MVLTG successfully promoted dehydrogenation reactions of prepolymers made from functionalized precursors of 4′,5″-dibromo-4-butoxy-1,1′:2′,1″:2″,1″′-quaterphenyl or 4′,5″-dibromo-4-butoxy-1,1′:2′,1″:2″,1‴:4‴,1″-quinquephenyl, suppressing decomposition of substituents. MVLTG not only realizes a new class of GNRs but also enables unprecedented on-surface synthesis.

Bottom-up synthesis of mesoscale nanomeshes of graphene nanoribbons on germanium

The synthesis of functional graphene nanostructures on Ge(001) provides an attractive route toward integrating graphene-based electronic devices onto complementary metal oxide semiconductor-compatible platforms. In this study, we leverage the phenomenon of the anisotropic growth of graphene nanoribbons from rationally placed graphene nanoseeds and their rotational self-alignment during chemical vapor deposition to synthesize mesoscale graphene nanomeshes over areas spanning several hundred square micrometers. Lithographically patterned nanoseeds are defined on a Ge(001) surface at pitches ranging from 50 to 100 nm, which serve as starting sites for subsequent nanoribbon growth. Rotational self-alignment of the nanoseeds followed by anisotropic growth kinetics causes the resulting nanoribbons to be oriented along each of the equivalent, orthogonal Ge⟨110⟩ directions with equal probability. As the nanoribbons grow, they fuse, creating a continuous nanomesh. In contrast to nanomesh synthesis via top-down approaches, this technique yields nanomeshes with atomically faceted edges and covalently bonded junctions, which are important for maximizing charge transport properties. Additionally, we simulate the electrical characteristics of nanomeshes synthesized from different initial nanoseed-sizes, size-polydispersities, pitches, and device channel lengths to identify a parameter-space for acceptable on/off ratios and on-conductance in semiconductor electronics. The simulations show that decreasing seed diameter and pitch are critical to increasing nanomesh on/off ratio and on-conductance, respectively. With further refinements in lithography, nanomeshes obtained via seeded synthesis and anisotropic growth are likely to have superior electronic properties with tremendous potential in a multitude of applications, such as radio frequency communications, sensing, thin-film electronics, and plasmonics.

Tailoring the epitaxial growth of oriented Te nanoribbon arrays

As an elemental semiconductor, tellurium (Te) has been famous for its high hole-mobility, excellent ambient stability and topological states. Here, we realize the controllable synthesis of horizontal Te nanoribbon arrays (TRAs) with an angular interval of 60°on mica substrates by physical vapor deposition strategy. The growth of Te nanoribbons (TRs) is driven by two factors, where the intrinsic quasi-one-dimensional spiral chain structure promotes the elongation of their length; the epitaxy relationship between [110] direction of Te and [110] direction of mica facilitates the oriented growth and the expansion of their width. The bending of TRs which have not been reported is induced by grain boundary. Field-effect transistors based on TRs demonstrate high mobility and on/off ratio corresponding to 397cm2V-1s-1 and 1.5×105, respectively. These phenomena supply an opportunity to deep insight into the vapor-transport synthesis of low-dimensional Te and explore its underlying application in monolithic integration.

Growth and Properties of Graphene and Graphene Nanoribbons on Ge

The synthesis of graphene directly on Ge and on Ge deposited on Si provides a scalable route toward integrating graphene onto conventional semiconductors. This presentation will first survey the growth modes of graphene on Ge(001), Ge(011), Ge(111), Ge(112), Ge(001)-6°, and Ge(001)-9° via chemical vapor deposition (CVD), reporting on the effect of Ge surface orientation on graphene island formation and shape, strain in large-area graphene films, and the nanofaceting of the Ge below graphene.[1] We will then focus on the anisotropic growth of semiconducting graphene nanoribbons on Ge(001) and Ge(001)-9° and of nominally single crystal graphene on Ge(110).On Ge(001), we have discovered how to drive graphene crystal growth with a large shape anisotropy through control of kinetics.[2-6] This discovery enables the direct synthesis of narrow, armchair, semiconducting nanoribbons. The ribbons are self-orienting, self-defining, and have smooth edges. The ribbons exhibit excellent transport properties (e.g., high on-state conductance and on/off ratio at room temperature) and provide a promising pathway towards the direct integration of high-performance nanocarbon electronics onto conventional semiconductor wafer platforms.On Ge(001), nominally single crystal graphene has been reported in limited cases; however, conflicting studies have evidenced polycrystallinity. Here, the factors affecting the mosaicity of graphene on Ge(110) will be elucidated using low energy electron diffraction and microscopy data.[7][1] R. M. Jacobberger, D. E. Savage, X. Zheng, P. Sookchoo, R. R. Delgado, M. G. Lagally, M. S. Arnold, SUBMITTED (2022).[2] R. M. Jacobberger, M. S. Arnold, et al., Direct Oriented Growth of Armchair Graphene Nanoribbons on Germanium, NATURE COMMUNICATIONS, 6, 8006 (2015).[3] B. Kiraly, M. S. Arnold, M. C. Hersam, N. P. Guisinger et al., Sub-5 nm, Globally Aligned Graphene Nanoribbons on Ge (001), APPLIED PHYSICS LETTERS, 108, 213101 (2016).[4] A. J. Way, R. M. Jacobberger, M. S. Arnold, Seed-Initiated Anisotropic Growth of Unidirectional Armchair Graphene Nanoribbon Arrays on Germanium, NANO LETTERS, 18, 898 (2018).[5] V. Saraswat, Y. Yamamoto, H.J. Kim, R.M. Jacobberger, K.R. Jinkins, A.J. Way, N.P. Guisinger, M.S. Arnold Synthesis of armchair graphene nanoribbons on germanium-on-silicon, THE JOURNAL OF PHYSICAL CHEMISTRY C 123 (30), 18445-18454 (2019).[6] A. J. Way, R. M. Jacobberger, N. P. Guisinger, V. Saraswat, X. Zheng, A. Suresh, J. H. Dwyer, P. Gopalan, Michael S. Arnold, SUBMITTED (2022).[7] R. M. Jacobberger, Z. Miao, T. Yu, V. Saraswat, M. G. Lagally, M. S. Altman, M. S. Arnold, SUBMITTED (2022).

Achievements and Challenges of Graphene Chemical Vapor Deposition Growth (Adv. Funct. Mater. 42/2022)

Chemical Vapor Deposition In article number 2203191, Feng Ding and co-authors report the vapor-liquid-solid growth of graphene nanospears and graphene nanoribbons on Cu surface. The vapor-liquid-solid growth of graphene nanostructures is enabled by liquid Si-Cu catalysts and opens a platform for excellent graphene-based electronics.

Bottom‐Up Growth of Graphene Nanospears and Nanoribbons

One dimensional graphene nanostructures are one of the most promising materials for next generation electronics. Here, the chemical vapor depostion growth of graphene nanoribbons (GNRs) and graphene nanospears (GNSs) on a copper surface is reported. The growth of GNRs and GNSs is enabled by a vapor–liquid–solid (VLS) mechanism guided by on-surface propagation of a liquid Cu-Si catalyst particle. The slow lateral growth and the fast VLS vertical growth give rise to spear head-shaped GNSs. In situ observations further confirm that the lateral graphene growth can be completely suppressed and thus GNRs are grown. The synthesized field effect transistor (FET) devices show that the GNRs and GNSs have high carrier mobilities of ≈2000 cm2 V−1 s−1. Both FET and Kelvin probe force microscopy measurements confirm that the Fermi levels of the synthesize GNSs shift downward from the wide part to the tip is strongly p-doped. These findings yield key insights into the growth mechanism of graphene and open a door for achieving a facile and scalable method of synthesizing free standing GNRs and GNSs and their applications, such as the Fermi-level tunable devices.

Enhanced Efficiency and Stability in Sb2S3 Seed Layer Buffered Sb2Se3 Solar Cells

AbstractAntimony selenide (Sb2Se3) has excellent directional optical and electronic behaviors due to its quasi‐1D nanoribbons structure. The photovoltaic performance of Sb2Se3 solar cells largely depends on the orientation of the nanoribbons. It is desired to grow these Sb2Se3 ribbons normal to the substrate to enhance photoexcited carrier transport. Therefore, it is necessary to develop a strategy for the vertical growth of Sb2Se3 nanoribbons to achieve high‐efficiency solar cells. Since antimony sulfide (Sb2S3) and Sb2Se3 are from the same space group (Pbnm) and have the same crystal structure, herein an ultrathin layer (≈20 nm) of Sb2S3 has been used to assist the vertical growth of Sb2Se3 nanoribbons to improve the overall efficiency of Sb2Se3 solar cell. The Sb2S3 thin layer deposited by the hydrothermal process helps the Sb2Se3 ribbons grow normal to the substrate and increases the efficiency from 5.65% to 7.44% through the improvement of all solar cell parameters. This work is expected to open a new direction to tailor the Sb2Se3 grain growth and further develop the Sb2Se3 solar cell in the future.

On‐surface synthesis of porous graphene nanoribbons containing nonplanar [14]annulene pores

AbstractThe precise introduction of nonplanar pores in the backbone of graphene nanoribbon represents a great challenge. Here, we explore a synthetic strategy toward the preparation of nonplanar porous graphene nanoribbon from a predesigned dibromohexabenzotetracene monomer bearing four cove‐edges. Successive thermal annealing steps of the monomers indicate that the dehalogenative aryl‐aryl homocoupling yields a twisted polymer precursor on a gold surface and the subsequent cyclodehydrogenation leads to a defective porous graphene nanoribbon containing nonplanar [14]annulene pores and five‐membered rings as characterized by scanning tunneling microscopy and noncontact atomic force microscopy. Although the C–C bonds producing [14]annulene pores are not achieved with high yield, our results provide new synthetic perspectives for the on‐surface growth of nonplanar porous graphene nanoribbons.

Solution phase growth and analysis of super-thin zigzag tin selenide nanoribbons

Tin selenide (SnSe), a highly promising layered material, has been garnering particular interest in recent times due to its significant promise for future energy devices. Herein we report a simple solution-phase approach for growing highly crystalline layered SnSe nanoribbons. Polyvinylpyrrolidone (PVP) was used as a templating agent to selectively passivates the (100) and (001) facets of the SnSe nanoribbons resulting in the unique growth of nanoribbons along their b-axis with a defined zigzag edge state along the sidewalls. The SnSe nanoribbons are few layers thick (∼20 layers), with mean widths of ∼40 nm, and achievable length of >1 μm. Nanoribbons could be produced in relatively high quantities (>150 mg) in a single batch experiment. The PVP coating also offers some resistance to oxidation, with the removal of the PVP seen to lead to the formation of a SnSe/SnO x core-shell structure. The use of non-toxic PVP to replace toxic amines that are typically employed for other 1D forms of SnSe is a significant advantage for sustainable and environmentally friendly applications. Heat transport properties of the SnSe nanoribbons, derived from power-dependent Raman spectroscopy, demonstrate the potential of SnSe nanoribbons as thermoelectric material.

CsCu2I3 Nanoribbons on Various Substrates for UV Photodetectors

Cesium copper (I) halides, as a lead-free halide material system, have shown great potential in optoelectronic devices due to their environmental friendliness, high quantum efficiency, and extraordinary air stability. However, most of the previous reports are on quantum dots, bulk crystals, or free-standing wires. It is still challenging to realize the in-plane growth of one-dimensional (1D) cesium copper (I) halides on various substrates, which is essential for nanodevices with high integration density. Herein, we report the planar growth of CsCu2I3 nanoribbons (NBs) with high-quality single crystals on diverse substrates through a spatial-confined method. The in situ investigation of the growth process reveals that the morphology evolution of the NBs is controlled by both thermodynamics and kinetics that are dependent on the local supersaturation near the NBs. The CsCu2I3 NB-based photodetectors (PDs) exhibit an outstanding ultraviolet (UV) detection performance with a high responsivity (0.27 A/W), a specific detectivity (6.38 × 108 Jones), and a fast photoresponse speed (trise/tdecay = 5.8/6.0 ms). Furthermore, the PDs exhibit high stability to light illumination and excellent flexibility to bending. The direct in-plane growth of the lead-free CsCu2I3 NBs on various substrates would promote the practical application of copper (I) halides in electronics and optoelectronics.

Microwave-assisted in situ growth of VO2 nanoribbons on Ni foam as inexpensive bifunctional electrocatalysts for the methanol oxidation and oxygen evolution reactions

Electrochemical water splitting and methanol (MeOH) oxidation using electrocatalysts are effective methods of producing clean energy with low pollutant emissions. In this study, low-cost vanadium oxide (VO2) electrocatalysts with nanoribbon-like structure (NRBs) were grown on Ni foam at 140, 180, and 220 °C using a microwave-assisted method. The electrochemical properties of the electrocatalysts fabricated at 140, 180, and 220 °C (VO-140, VO-180, and VO-220, respectively) were evaluated for the MeOH oxidation reaction (MOR) and oxygen evolution reaction (OER) using cyclic voltammetry (CV), linear sweep voltammetry (LSV), multi-step chronoamperometry (M−CA), and electrochemical impedance spectroscopy analyses (EIS). The VO-180 electrocatalyst presented a high current density of 224 mA cm−2 for MOR and an overpotential of 150 mV at a current density of 10 mA cm−2 for OER. The specific surface area and electron transfer rate of VO-180 were higher than those of VO-140 and VO-220. Moreover, the as-synthesized VO-180 electrocatalyst exhibited excellent MOR and OER activity and stability, suggesting its potential applications in direct MeOH fuel cells.

Unravelling the growth mechanism of (3,1) graphene nanoribbons on a Cu(111) surface.

The growth of graphene nanoribbons has been widely investigated on metal surfaces in an ultrahigh vacuum. Here, we re-investigate the growth of graphene nanoribbons obtained by thermal annealing of 9,9'-bianthryl derivatives on a Cu(111) surface by using scanning tunnelling microscopy. On the basis of our results, we propose to complete the reaction mechanism commonly accepted in the literature by adding an intramolecular hydrogen atom transfer from the 2,2'-positions to the 10,10'-positions as a key-step in the formation of (3,1)-graphene nanoribbons on a Cu(111) surface.

Templating Effect of Different Low-Miller-Index Gold Surfaces on the Bottom-Up Growth of Graphene Nanoribbons

This work is focused on the structural control of graphene nanoribbons (GNRs) and intermediate polymeric wires [poly(p-phenylene), PPP] during their thermoactivated bottom-up synthesis from room te...

Bottom-up Growth of Graphene Nanoribbons for Application to Electronic Devices

Bottom-up Growth of Graphene Nanoribbons for Application to Electronic Devices

Well-defined sub-nanometer graphene ribbons synthesized inside carbon nanotubes

Graphene nanoribbons with sub-nanometer widths are extremely interesting for nanoscale electronics and devices as they combine the unusual transport properties of graphene with the opening of a band gap due to quantum confinement in the lateral dimension. Strong research efforts are presently paid to grow such nanoribbons. Here we show the synthesis of 6- and 7-armchair graphene nanoribbons, with widths of 0.61 and 0.74 nm, and excitonic gaps of 1.83 and 2.18 eV, by high-temperature vacuum annealing of ferrocene molecules inside single-walled carbon nanotubes. The growth of the so-obtained graphene nanoribbons is evidenced from atomic resolution electron microscopy, while their well-defined structure is identified by a combination of an extensive wavelength-dependent Raman scattering characterization and quantum-chemical calculations. These findings enable a facile and scalable approach leading to the controlled growth and detailed analysis of well-defined sub-nanometer graphene nanoribbons.

Exploring driving forces for length growth in graphene nanoribbons during chemical vapor deposition of hydrocarbons on Ge(0 0 1) via kinetic Monte Carlo simulations

Graphene grown slowly on Ge(0 0 1) using chemical vapor deposition of hydrocarbons leads to high-aspect ratio graphene nanoribbons with smooth edges and a technologically relevant band gap at room temperature; however, the driving forces leading to one-dimensional growth of such graphene crystals are not well understood. Here, we combine a lattice kinetic Monte Carlo approach based on steps in graphene growth and experimental measurements to study the growth of graphene nanoribbons via chemical vapor deposition on Ge(0 0 1). To identify potential reasons for growth of graphene as anisotropic ribbons, we study the impact of anisotropy in various growth parameters on the resulting graphene crystals. Comparing our model with experimental measurements indicates that anisotropy in the stabilization of a graphene precursor species bound to the graphene edge is the most likely reason why high aspect ratio graphene ribbons with smooth edges grow on Ge(0 0 1). Using the growth model developed here, we reproduce experimental trends in the synthesis of graphene nanoribbons on Ge(001) and arrive at an intuitive picture for their growth. These insights shed light on the driving forces governing this highly anisotropic regime of crystal growth.

One-Step Synthesis of Enhanced Band-Edge Emission ZnSe Nanowires Assisted by SnO&lt;SUB&gt;2&lt;/SUB&gt;

Zinc selenide (ZnSe) is a direct band gap semiconductor material with a band gap of 2.7 eV at room temperature, and is a very promising blue light emitting material. However, the ZnSe nanomaterials grown by the usual Au-catalyzed chemical vapor deposition (CVD) method are prone to cause defects in the material, and its luminescence spectra generally have strong yellow light emission, which seriously affects its application in blue light devices. The paper proposes a simple method for preparing blue light-emitting ZnSe nanowires. Adding a small amount of SnO2 to the source material ZnSe powder, when using the CVD method to grow ZnSe nanomaterials, can obtain ZnSe nanomaterials with only band edge blue emission. SnO2 can not only act as a catalyst, promote the growth of ZnSe nanowires and nanoribbons, reduce the growth temperature of nanomaterials, but also avoid the occurrence of deep level defects in ZnSe nanomaterials, and obtain pure blue light emitting ZnSe nanowires. The emission peak of the nanowire grown by this method can be shifted from 460 to 500 nm. By precisely regulating the growth of the nanowire, it can make it emit light to cover the entire blue region, which can promote the application of inorganic semiconductor nanomaterials in the field of lighting and display.