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The presence of metal atoms at the edges of graphene nanoribbons (GNRs) opens new possibilities toward tailoring their physical properties. We present here formation and high-resolution characterization of indium (In) chains on the edges of graphene-supported GNRs. The GNRs are formed when adsorbed hydrocarbon contamination crystallizes via laser heating into small ribbon-like patches of a second graphitic layer on a continuous graphene monolayer and onto which In is subsequently physical vapor deposited. Using aberration-corrected scanning transmission electron microscopy (STEM), we find that this leads to the preferential decoration of the edges of the overlying GNRs with multiple In atoms along their graphitic edges. Electron-beam irradiation during STEM induces migration of In atoms along the edges of the GNRs and triggers the formation of longer In atom chains during imaging. Density functional theory (DFT) calculations of GNRs similar to our experimentally observed structures indicate that both bare zigzag (ZZ) GNRs as well as In-terminated ZZ-GNRs have metallic character, whereas in contrast, In termination induces metallicity for otherwise semiconducting armchair (AC) GNRs. Our findings provide insights into the creation and properties of long linear metal atom chains at graphitic edges. [ABSTRACT FROM AUTHOR]

Many applications of 2D materials require deposition of non‐2D metals and metal‐oxides onto the 2D materials. Little is however known about the mechanisms of such non‐2D/2D interfacing, particularly at the atomic scale. Here, atomically resolved scanning transmission electron microscopy (STEM) is used to follow the entire physical vapor deposition (PVD) cycle of application‐relevant non‐2D In/In2O3 nanostructures on graphene. First, a "quasi‐in‐situ" approach with indium being in situ evaporated onto graphene in oxygen‐/water‐free ultra‐high‐vacuum (UHV) is employed, followed by STEM imaging without vacuum break and then repeated controlled ambient air exposures and reloading into STEM. This allows stepwise monitoring of the oxidation of specific In particles toward In2O3 on graphene. This is then compared with conventional, scalable ex situ In PVD onto graphene in high vacuum (HV) with significant residual oxygen/water traces. The data shows that the process pathway difference of oxygen/water feeding between UHV/ambient and HV fabrication drastically impacts not only non‐2D In/In2O3 phase evolution but also In2O3/graphene out‐of‐plane texture and in‐plane rotational van‐der‐Waals epitaxy. Since non‐2D/2D heterostructures' properties are intimately linked to their structure and since influences like oxygen/water traces are often hard to control in scalable fabrication, this is a key finding for non‐2D/2D integration process design. [ABSTRACT FROM AUTHOR]

Single‐walled carbon nanotubes (SWCNTs) with a mean diameter of 1.4 nm are filled with rubidium iodide. The filling of nanotubes is proved by high‐resolution scanning transmission electron microscopy. The chemical composition of the filler is confirmed by X‐ray photoelectron spectroscopy (XPS). The electronic properties of the filled SWCNTs are studied by XPS and Raman spectroscopy. The encapsulated salt leads to n‐doping of nanotubes. The detailed multifrequency Raman spectroscopy investigation of the alteration of Raman modes of SWCNTs upon filling is conducted. The doping‐induced changes in the radial breathing mode and G‐band are revealed. It is found that these changes differ for the metallic and semiconducting SWCNTs. The obtained data and revealed trends are expected to be helpful for forthcoming studies to interpret the observed changes in Raman spectra of filled metallic and semiconducting SWCNTs. [ABSTRACT FROM AUTHOR]

Crystalline Ni/Au bimetallic oxide nanoparticles with various forms of crystallographic systems and defects were generated by femtosecond laser ablation of nickel–gold target in alcoholic solvents. The nature of the liquid can influence the chemical composition, stability, and size distribution of laser-synthesized nanoparticles. In ethanol, bimodal crystalline bimetallic Ni/Au oxide nanoparticles with median size of 15 nm were synthesized. The laser ablation of Ni/Au target in isopropanol and butanol led to nearly monomodal size distribution with median size of 10 and 13 nm, respectively. High-resolution transmission electron microscopy of Ni/Au oxide nanoparticles in butanol, revealed a graphitic shell of a few atomic layers. In this context, two suggested mechanisms were considered. First of all, the high photon intensity of femtosecond laser pulses can induce direct photolysis of liquid media. Secondly, the formation of supercritical temperature solvent due to the interaction of solvent with molten metal layer at liquid–metal interface can trigger pyrolysis of solvent. These mechanisms can contribute to butanol decomposition and encapsulation of Ni/Au oxide bimetallic nanoparticles with graphite shell. Graphite shell can create a better colloidal stability by preventing nanoparticles from further growth and agglomeration. [ABSTRACT FROM AUTHOR]

We have investigated the electronic properties of single-walled carbon nanotubes (SWCNTs) filled with lead chloride, lead bromide (PbBr2) and lead iodide (PbI2). The filling of SWCNTs and formation of encapsulated one-dimensional nanocrystals of the salts were directly confirmed by high-resolution scanning transmission electron microscopy. The chemical composition of the encapsulated nanocrystals was proven by X-ray photoelectron spectroscopy (XPS). The electronic properties of the filled SWCNTs were characterized by Raman spectroscopy and XPS. All the three lead halogenides result in p-doping of SWCNTs and, consequently, there is a downshift of the SWCNTs' Fermi level due to the charge transfer towards the salts. The effect is stronger with metallic than semiconducting nanotubes. The efficiency of doping depends on the type of lead halogenide. The doping effect is the strongest for PbI2 and the weakest for PbBr2. [ABSTRACT FROM AUTHOR]