Nanowires are conventionally assumed to grow via the vapor-liquid-solid process, in which material from vapor is incorporated into growing nanowire a liquid catalyst, commonly low–melting point eutectic alloy. However, nanowires have been observed below temperature, and state of catalyst remains controversial. Using situ microscopy, we showed that, for classic Ge/Au system, growth can occur temperature with either or solid catalysts at same temperature. We found, unexpectedly, that depends...

Sharp Nanowires The potential for using nanowires in devices can be limited by the ability to synthesize them from two or more materials while maintaining compositional purity at interfaces. Instead of liquid droplets eutectic point when melting is a minimum, Wen et al. (p. 1247 ) show that generating wires solid alloy catalysts allows fabrication silicon germanium with atomically sharp system works well because an AlAu composition was chosen which Si and Ge have low solubility but high...

We report in situ scanning tunneling microscopy studies of graphene growth on Pd(111) during ethylene deposition at temperatures between 723 and 1023 K. observe the formation monolayer islands, 200−2000 Å size, bounded by Pd surface steps. Surprisingly, topographic image contrast from islands reverses with bias, suggesting a semiconducting behavior. Scanning spectroscopy measurements confirm that are semiconducting, band gap 0.3 ± 0.1 eV. On basis density functional theory calculations, we...

Density functional methods were used to calculate binding and diffusion energies of adatoms, molecules, small clusters on TiN(001) TiN(111) surfaces in order isolate the key atomistic processes which determine texture evolution during growth polycrystalline TiN layers. The surface energy for nonpolar TiN(001), 81 meV/Å2, was found be lower than that both N- Ti-terminated polar surfaces, 85 346 meV/Å2. While N2 molecules are only weakly physisorbed, Ti adatoms form strong bonds with 3.30 eV,...

We examine individual Si nanowires grown by the vapor-liquid-solid mechanism, using real-time in situ ultra high vacuum transmission electron microscopy. By directly observing Au-catalyzed growth of wires from disilane, we show that rate is independent wire diameter, contrary to expected behavior. Our measurements unique rate-limiting step here irreversible, kinetically limited, dissociative adsorption disilane on catalyst surface. also identify a novel dependence taper.

We measured the nucleation and growth kinetics of solid silicon (Si) from liquid gold-silicon (AuSi) catalyst particles as Si supersaturation increased, which is first step vapor-liquid-solid nanowires. Quantitative measurements agree well with a kinetic model, providing unified picture process. Nucleation heterogeneous, occurring consistently at edge AuSi droplet, yet it intrinsic highly reproducible. studied critical required for found no observable size effects, even systems down to 12...

We present an extensive investigation of the epitaxial growth Au-assisted axial heterostructure nanowires composed group IV and III−V materials derive a model to explain overall morphology such wires. By analogy with 2D growth, this relates wire (i.e., whether it is kinked or straight) relationship interface energies between two particle. This suggests that, for any pair materials, should be easier form straight one direction than other, we demonstrate material combinations presented here....

Nanowire growth in the standard $⟨111⟩$ direction is assumed to occur at a planar catalyst-nanowire interface, but recent reports contradict this picture. Here we show that nonplanar interface is, fact, general phenomenon. Both III--V and group IV nanowires distinct region trijunction with different orientation whose size oscillates during growth, synchronized step flow. We develop an explicit model for structure agrees well experiment shows oscillations provide direct visualization of...

We report an ab initio study of the mechanical stability platinum nitride (PtN), in four different crystal structures, rock salt (rs-PtN), zinc-blende (zb-PtN), cooperite, and a face-centered orthorhombic phase. Of these phases only rs-PtN phase is found to be stable has highest bulk modulus $B=284\phantom{\rule{0.3em}{0ex}}\mathrm{GPa}$. Its electronic density states shows no band gap making it metallic. The zb-PtN does not stabilize or harden by nitrogen vacancies investigated this study....

Using density functional theory calculations with van der Waals corrections, we investigated how the interlayer orientation affects structure and electronic properties of MoS2-graphene bilayer heterostructures. Changing graphene respect to MoS2 strongly influences type value bandgap in MoS2, while not significantly altering binding energy between layers or spacing. We show that physical origin this tunable arises from variations S–S interplanar distance (MoS2 thickness) orientation, which...

Semiconductor nanowires formed using the vapor−liquid−solid mechanism are routinely grown in many laboratories, but a comprehensive understanding of key factors affecting wire growth is still lacking. In this paper we show that, under conditions low disilane pressure and higher temperature, long, untapered Si wires cannot be grown, Au catalyst, without presence oxygen. Exposure to oxygen, even at levels, reduces diffusion away from catalyst droplets. This allows droplet volumes remain...

Measurements of solution-phase crystal growth provide mechanistic information that is helpful in designing and synthesizing nanostructures. Here, we examine the model system individual Au nanocrystal formation within a defined liquid geometry during electron beam irradiation gold chloride solution, where radiolytically formed hydrated electrons reduce ions to solid Au. By selecting conditions favor well-faceted nanoprisms, measure rates crystals. The volume each increases linearly with time...

Selected-area diffraction establishes that at least six different in-plane orientations of monolayer graphene on Pd(111) can form during growth. From the intensities low-energy electron microscopy images as a function incident energy, we find work functions rotational domains vary by up to 0.15 eV. Density functional theory calculations show these significant variations result from orientation-dependent charge transfer Pd graphene. These findings suggest electronics will require precise...

Refractory carbides of transition metals (Zr, Ta, etc.), owing to a mixture ionic, covalent, and metallic bonding, exhibit high hardness (10s GPa), elastic moduli (100s good resistance wear, ablation, corrosion, high‐temperature mechanical strength, along with electrical conductivities. They are attractive as structural components in aerospace vehicles. Although these materials exceptionally hard, their applications at low temperatures have been limited because brittleness. The design...

Using scanning tunneling microscopy and spectroscopy, in combination with density functional theory calculations, we investigated the morphology electronic structure of monolayer graphene grown on (111) (110) facets three-dimensional nickel islands highly oriented pyrolytic graphite substrate. We observed domains exhibiting hexagonal striped moiré patterns periodicities 22 12 Å, respectively, Ni islands. Graphene are also to grow, as single crystals, across adjacent over facet boundaries....

Vertical indium phosphide nanowires have been grown epitaxially on silicon (111) by metalorganic vapor-phase epitaxy. Liquid droplets were formed in situ and used to catalyze deposition. For growth at 350 degrees C, about 70% of the wires vertical, while remaining ones distributed 3 other <111> directions. The vertical fraction, rate, tapering increased with temperature V/III ratio. At 370 C equal 200, 100% a density approximately 1.0 x 10(9) cm(-2) average dimensions 3.9 mum length, 45 nm...

By combining in situ and ex transmission electron microscopy measurements, we examine the factors that control morphology of "hybrid" nanowires include group III–V IV materials. We focus on one materials pair, GaP/Si, for which use a wide range growth parameters. show through video imaging nanowire depends conditions, but general pattern emerges where either single kinks or inclined defects form some distance after heterointerface. pure Si can be made to exhibit same by changing their...

Au nanoplates (quasi-two-dimensional single crystals) are most commonly synthesized using a mixture of precursors via approaches involving multiple processing steps and the use seed crystals. Here, we report synthesis truncated-hexagonal {111}-oriented micrometer-scale on graphene multilayers only potassium tetrabromoaurate (KAuBr4) as precursor. We demonstrate that nanoplate sizes can be controllably varied from tens nanometers up to few micrometers by introducing desired concentrations...

The morphological phase diagram is reported for InP nanostructures grown on (111)B as a function of temperature and V/III ratio. Indium droplets were used the catalyst generated in situ metalorganic vapor-phase epitaxy reactor. Three distinct observed: wires, cones, pillars. It proposed that shape depends relative rates indium phosphide deposition via vapor-liquid-solid (VLS) (VPE) processes. rate VLS relatively insensitive to results vertical wire growth starting at 350 degrees C. By...

Idealized nanowire geometries assume stable sidewalls at right angles to the growth front. Here we report simulations that include a mix of nonorthogonal facet orientations, as for Au-catalyzed Si. We compare these with in situ microscopy observations, finding striking correspondences. In both experiments and simulations, there are distinct modes accommodate lack different ways--one through sawtooth-textured sidewalls, other front an angle axis. Small changes conditions can reversibly switch...