Formation of Cu_xAu_1−x phases by cold homogenization of Au/Cu nanocrystalline thin films

• Alona Tynkova,
• Gabor L. Katona,
• Gabor A. Langer,
• Sergey I. Sidorenko,
• Svetlana M. Voloshko and
• Dezso L. Beke

Beilstein J. Nanotechnol. 2014, 5, 1491–1500, doi:10.3762/bjnano.5.162

• , which leads to formation of intermetallic phases. Different compounds can be formed depending on the initial thickness ratio. The process starts with grain boundary interdiffusion, which is followed by a formation of reaction layers at the grain boundaries that leads to the motion of the newly formed

• interfaces perpendicular to the grain boundary plane. Finally, the homogenization finishes when all the pure components have been consumed. The process is asymmetric: It is faster in the Au layer. In Au(25nm)/Cu(50nm) samples the final state is the ordered AuCu3 phase. Decrease of the film thicknesses, as

• using a simple model the interface velocity in both the Cu and Au layers were estimated from the linear increase of the average composition and its value is about two orders of magnitude larger in Au (ca. 10−11 m/s) than in Cu (ca. 10−13 m/s). Keywords: Cu/Au; grain boundary diffusion; nanofilms of

Scale effects of nanomechanical properties and deformation behavior of Au nanoparticle and thin film using depth sensing nanoindentation

• Dave Maharaj and
• Bharat Bhushan

Beilstein J. Nanotechnol. 2014, 5, 822–836, doi:10.3762/bjnano.5.94

• disrupt the regular atomic arrangements in the lattice planes, the so called dislocations. Figure 1 shows for a polycrystalline material, as an example, dislocations in the grain originating from the grain boundary and the grain interior, from a multiplication of existing dislocations during loading or

• grain boundary. The stress at the grain boundary is called the pile up stress, given as where τi is the friction stress opposing the movement of the dislocations. The number of dislocations in the pile up in grain A (n1A) is greater than in grain C (n2C) due to the larger size which leads to a greater

• τp. For a slip to occur across the grain boundary, τp must be greater than the critical stress, τcritical. A higher initial τ is therefore required on grain C before the critical stress is reached to allow slip to occur and plastic deformation to continue, which results in a higher yield stress

Confinement dependence of electro-catalysts for hydrogen evolution from water splitting

• Mikaela Lindgren and
• Itai Panas

Beilstein J. Nanotechnol. 2014, 5, 195–201, doi:10.3762/bjnano.5.21

• grain boundaries, see Figure 1a, These hydroxide ions subsequently react with transition metal decorated sites (see Figure 1a) and zirconium metal to produce ZrO2 in conjunction with transient transition metal associated hydride-proton (hydroxide) pairs (see Figure 1b) to restore the ZrO2 grain boundary

• according to This can be subdivided into an anode process where the [ZrIV–O–ZrIV] oxide grain boundary is recovered, and a cathode process is employed to decide the oxidation state X. The subsequent chemical drive for H2 release into the confining grain boundary determines M and recovers the [ZrIV–O–MX

• ] site (cf. Figure 1c) Indeed, Equation 6 was found to be decisive for the fraction of hydrogen atoms not forming H2 but being absorbed in the Zr alloy according to For completeness, a 1.1 eV/H2 drive to release H2 from the confining grain boundary was computed according to Utilization of the hydride

Mapping of plasmonic resonances in nanotriangles

• Simon Dickreuter,
• Julia Gleixner,
• Andreas Kolloch,
• Johannes Boneberg,
• Elke Scheer and
• Paul Leiderer

Beilstein J. Nanotechnol. 2013, 4, 588–602, doi:10.3762/bjnano.4.66

• nm. When the films are molten and solidify quickly on a nanosecond scale, they become smoother and exhibit grain boundary structures. (For larger melting times the films would start to dewet and would develop holes [42].) The melting threshold, Ith,melt, calculated from Figure 17 and the

Deformation-induced grain growth and twinning in nanocrystalline palladium thin films

• Aaron Kobler,
• Jochen Lohmiller,
• Jonathan Schäfer,
• Michael Kerber,
• Anna Castrup,
• Ankush Kashiwar,
• Patric A. Gruber,
• Karsten Albe,
• Horst Hahn and
• Christian Kübel

Beilstein J. Nanotechnol. 2013, 4, 554–566, doi:10.3762/bjnano.4.64

• are under investigation for a number of years, there still is an ongoing debate on the deformation mechanisms active in these materials. Discussed are grain boundary sliding, grain rotation, emission and annihilation of dislocations at grain boundaries, intragranular dislocation glide resulting in

• twinning/detwinning processes, stress-driven grain boundary migration and the formation of shear bands [4][5][6][7]. When studying the mechanical properties of nc metals and the associated deformation mechanisms, it is important to consider the preparation technique for the corresponding bulk nc metal

• ., pores and impurities may pin grain boundaries [14][15]. Furthermore, the different production techniques may also lead to different grain boundary structures with varying free volume and defect structure [4][16][17]. All these factors will affect the mechanical behavior of the material, making it

Plasticity of nanocrystalline alloys with chemical order: on the strength and ductility of nanocrystalline Ni–Fe

• Jonathan Schäfer and
• Karsten Albe

Beilstein J. Nanotechnol. 2013, 4, 542–553, doi:10.3762/bjnano.4.63

• of disordered structures with various elemental distributions and the simultaneous analysis of intragranular defects reveal that solid solution strengthening is absent for the studied grain sizes. The composition and relaxation state of the grain boundary control the strength of the material, which

• is also found for ordered structures (L12), where dislocation activity is suppressed. Keywords: nanocrystalline materials; grain boundary structure; grain boundary segregation; plastic deformation; molecular dynamics; Introduction In intermetallics grain refinement to the nanometer scale has been

• considered as a possible route for achieving room temperature ductility in this otherwise brittle class of materials [1][2]. The underlying assumption is that for very small grain sizes plasticity can be carried by grain boundary (GB) mediated processes rather than by energetically expensive superlattice

Digging gold: keV He⁺ ion interaction with Au

• Vasilisa Veligura,
• Gregor Hlawacek,
• Robin P. Berkelaar,
• Raoul van Gastel,
• Harold J. W. Zandvliet and
• Bene Poelsema

Beilstein J. Nanotechnol. 2013, 4, 453–460, doi:10.3762/bjnano.4.53

• presented, but after six weeks. The blister, formed by the 35 keV beam and presented in Figure 1c, was imaged again after 16 weeks. The image is shown in Figure 1d. In both cases the pattern has almost completely vanished, except in areas close to the grain boundary (inset in Figure 1c), which apparently

• vicinity of the grain boundary. HIM SE images of the pattern that develops on the Au{111} surface as a function of ion fluence. Numbers indicate the ion fluence in helium ions per cm2. Arrows in (d) and (g) indicate the azimuthal directions of the grains. The He+ beam energies are 15, 25 and 35 keV. FOV is

Ferromagnetic behaviour of Fe-doped ZnO nanograined films

• Boris B. Straumal,
• Svetlana G. Protasova,
• Andrei A. Mazilkin,
• Thomas Tietze,
• Eberhard Goering,
• Gisela Schütz,
• Petr B. Straumal and
• Brigitte Baretzky

Beilstein J. Nanotechnol. 2013, 4, 361–369, doi:10.3762/bjnano.4.42

• Metallurgy and Materials Science, Russian Academy of Sciences, Leninsky prospect 49, 117991 Moscow, Russia 10.3762/bjnano.4.42 Abstract The influence of the grain boundary (GB) specific area sGB on the appearance of ferromagnetism in Fe-doped ZnO has been analysed. A review of numerous research

• contributions from the literature on the origin of the ferromagnetic behaviour of Fe-doped ZnO is given. An empirical correlation has been found that the value of the specific grain boundary area sGB is the main factor controlling such behaviour. The Fe-doped ZnO becomes ferromagnetic only if it contains enough

• content can be explained by the changes in the structure and contiguity of a ferromagnetic “grain boundary foam” responsible for the magnetic properties of pure and doped ZnO. Keywords: Fe; ferromagnetism; grain boundaries; ZnO; Introduction The possibility of ferromagnetism (FM) in oxides has been

Grain boundaries and coincidence site lattices in the corneal nanonipple structure of the Mourning Cloak butterfly

• Ken C. Lee and
• Uwe Erb

Beilstein J. Nanotechnol. 2013, 4, 292–299, doi:10.3762/bjnano.4.32

• particular emphasis on the high-angle grain-boundary-like defects that are observed between individual nanonipple crystals. It is shown that these grain boundaries are generated by rows of topological coordination defects, which create very specific misorientations between adjacent crystals. These specific

• parameter of about 200 nm. Perfect crystals with sizes on the order of a few micrometers cover the entire surface of each ommatidium. The crystals are separated by grain-boundary type defects created by rows of 5–7 coordination defects. While an individual 5–7 coordination defect in a perfect crystal

• these defect rows are clearly grain-boundary-type defects across which the orientations of otherwise defect-free crystals change. What is quite remarkable in both cases shown in Figure 4 is that some sort of superlattice can be identified as indicated by the nipples marked in white. This superlattice

Characterization and properties of micro- and nanowires of controlled size, composition, and geometry fabricated by electrodeposition and ion-track technology

• Maria Eugenia Toimil-Molares

Beilstein J. Nanotechnol. 2012, 3, 860–883, doi:10.3762/bjnano.3.97

• compared to its bulk counterpart, which is relevant to nanowire applications such as field-effect transistor sensors, and interconnectors. The influence of grain boundary scattering on the resistivity was predicted decades ago by Mayadas and Shatzkes, and depends on parameters such as electron mean free

Spontaneous dissociation of Co₂(CO)₈ and autocatalytic growth of Co on SiO₂: A combined experimental and theoretical investigation

• Kaliappan Muthukumar,
• Harald O. Jeschke,
• Roser Valentí,
• Evgeniya Begun,
• Johannes Schwenk,
• Fabrizio Porrati and
• Michael Huth

Beilstein J. Nanotechnol. 2012, 3, 546–555, doi:10.3762/bjnano.3.63

• precursor [52][53]. A larger degree of grain boundary scattering in the spontaneously formed deposit, as well as a possibly higher carbon content may be the cause for this enhanced resistivity. We also performed temperature-dependent resistivity measurements (Figure 4a) as well as Hall effect measurements

Functionalised zinc oxide nanowire gas sensors: Enhanced NO₂ gas sensor response by chemical modification of nanowire surfaces

• Eric R. Waclawik,
• Jin Chang,
• Andrea Ponzoni,
• Isabella Concina,
• Dario Zappa,
• Elisabetta Comini,
• Nunzio Motta,
• Guido Faglia and
• Giorgio Sberveglieri

Beilstein J. Nanotechnol. 2012, 3, 368–377, doi:10.3762/bjnano.3.43

• devices. Since the working principle of an oxide-semiconductor gas sensor involves the receptor function that is played by the surface of each oxide grain and the transducer function that is played by each grain boundary [3], the self-assembly of DT and THMA monolayers on the surface of the oxide was

• expected to modify both functions. The performances of both ZnO nanoparticle (ZnO NP) sensors and also ZnO nanowire (ZnO NW) sensors coated with a low density of DT-, or THMA-functionalised ZnO nanoparticles were examined and compared to nanowire-only devices to test the influence of grain-boundary effects

Formation of precise 2D Au particle arrays via thermally induced dewetting on pre-patterned substrates

• Dong Wang,
• Ran Ji and
• Peter Schaaf

Beilstein J. Nanotechnol. 2011, 2, 318–326, doi:10.3762/bjnano.2.37

• , and then proceeds with void growth and particle formation. For polycrystalline films on the flat substrates, void nucleation is generally thought to occur due to grain boundary grooving, via surface diffusion at the grain boundaries, and grain boundary triple junctions which intersect the substrate

• surface [39][40]. Recently, Mueller and Spolenak have reported that holes (large substrate-exposing voids) were found to protrude into the film predominantly at high angle grain boundaries during dewetting [41]. During annealing, grain boundary grooving and grain growth are competing kinetic processes

• . Grain growth is driven by the reduction of total grain boundary energy. The total grain boundary energy decreases with decreasing total grain boundary area. Microscopically, the reduction of the grain boundary area is accomplished by the movement of the individual boundaries and reducing the boundary