Optical modeling-assisted characterization of dye-sensitized solar cells using TiO₂ nanotube arrays as photoanodes

• Jung-Ho Yun,
• Il Ku Kim,
• Yun Hau Ng,
• Lianzhou Wang and
• Rose Amal

Beilstein J. Nanotechnol. 2014, 5, 895–902, doi:10.3762/bjnano.5.102

• TiO2 nanoparticles, vertically well-ordered TNT-based DSSCs presented an enhanced electron transport by efficiently reducing the recombination possibility of photogenerated charge carriers through minimizing the trapping sites that normally exist in the grain boundaries of randomly oriented TiO2

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

• stress or hardness as the dislocations interact with each other or at the grain boundaries in polycrystalline material. These interactions are responsible for the trend of enhanced mechanical properties with reduction in size or the ‘smaller is stronger’ phenomenon. They help to explain certain

• –displacement curves point to pop-in events during indentation. The horizontal white arrows indicate the nanoparticle of interest along with the section on which the profiles were taken. The pop-in events correspond to generation of new dislocations and multiplication of existing dislocations within the grain

• boundaries, which leads to an increase in displacement at a constant load. The eventual hardening is due to the dislocation density mechanism and possibly the pile-up mechanism, as discussed in section Mechanisms. Similar to the thin film, it is believed that the submicron size of the Au nanoparticles

Resonance of graphene nanoribbons doped with nitrogen and boron: a molecular dynamics study

• Ye Wei,
• Haifei Zhan,
• Kang Xia,
• Wendong Zhang,
• Shengbo Sang and
• Yuantong Gu

Beilstein J. Nanotechnol. 2014, 5, 717–725, doi:10.3762/bjnano.5.84

• grain boundaries, oxidations or vacancies [34][35]. Specifically, for GNRs with vacancies, researchers reported three different types of nitrogen doping, namely graphitic N, pyridine-like N and pyrrole-like N depending on their locations. Therefore, in the following, we consider the vibration properties

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

Template based precursor route for the synthesis of CuInSe₂ nanorod arrays for potential solar cell applications

• Mikhail Pashchanka,
• Jonas Bang,
• Niklas S. A. Gora,
• Ildiko Balog,
• Rudolf C. Hoffmann and
• Jörg J. Schneider

Beilstein J. Nanotechnol. 2013, 4, 868–874, doi:10.3762/bjnano.4.98

• moderate shift of this peak to lower wavenumbers may result from structural defects like grain boundaries, and confirms the nanocrystalline composition of the nanorods [27]. The broad structureless signal centred at 226 cm−1 is also in good agreement with previous studies of CuInSe2 lattice dynamics

Evolution of microstructure and related optical properties of ZnO grown by atomic layer deposition

• Adib Abou Chaaya,
• Roman Viter,
• Mikhael Bechelany,
• Zanda Alute,
• Donats Erts,
• Anastasiya Zalesskaya,
• Kristaps Kovalevskis,
• Vincent Rouessac,
• Valentyn Smyntyna and
• Philippe Miele

Beilstein J. Nanotechnol. 2013, 4, 690–698, doi:10.3762/bjnano.4.78

• than unity, which points to an oxygen-rich stoichiometry of the studied samples. In oxygen-rich films Zn vacancies, oxygen interstitials and oxygen interstates can be formed [46]. The excess oxygen may also localize on grain boundaries to form a negative surface charge [54] and depletion layer. The

• crystalline structure with a growing size of the grains. A narrowing of the depleted layer which does not affect the visible emissions is attributed to a low bulk concentration of oxygen vacancies mainly located on grain boundaries. The oxygen excess is attributed to the formation of Zn vacancies, oxygen

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

• , the conventional deformation mechanisms based on dislocation motion and multiplication, which govern deformation in coarse-grained metals, are increasingly limited by grain boundaries with decreasing grain size. It is believed that their low ductility is associated with this [3]. Although nc metals

• 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

• ., 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

• order of 2 GPa and an increase in strength after annealing even though some grain growth was observed [11]. It was reported that plastic deformation processes in nc Ni–Fe (15% Fe) undergo a transition with applied strain, where at low strains the strain is mainly accommodated by the grain boundaries

• randomly placed center points in 3-dimensional periodic cubic simulation box. The lattice orientations of the grains were taken from a random isotropic distribution. For avoiding spurious configurations in the as-prepared Voronoi samples, we deleted atoms from the grain boundaries that were closer than 2.0

• αi = 1 − Zj/(12 × (1 − ci)), where αi denotes the ordering parameter for atom of type i, Zj is the number of atoms of the according other type among the 12 nearest neighbors and ci is the global concentration of atoms of type i. For distinguishing atoms located in grain boundaries from those in the

Nanoglasses: a new kind of noncrystalline materials

• Herbert Gleiter

Beilstein J. Nanotechnol. 2013, 4, 517–533, doi:10.3762/bjnano.4.61

• not yet been utilized to a similar extent. The main reason is that, so far, glasses are produced by quenching the melt and/or the vapor. Obviously, this approach does not permit the introduction of defect microstructures (e.g., similar to grain boundaries, Figure 1) or chemical microstructures (e.g

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

• polycrystalline nature of the samples influences the pattern formation as well. First, the pattern propagation is stopped by grain boundaries as can be seen in the inset in Figure 1c: no pattern or rising of the surface level is observed on the neighboring grain. Second, the pattern orientation depends on the

• of adatoms on the surface. Gold interstitials are able to travel a few tens of nanometers outside the exposed area, but they cannot cross grain boundaries. The pattern orientation along a specific crystallographic direction can be explained by considering its formation as a result of the suppression

Kelvin probe force microscopy of nanocrystalline TiO₂ photoelectrodes

• Alex Henning,
• Gino Günzburger,
• Res Jöhr,
• Yossi Rosenwaks,
• Biljana Bozic-Weber,
• Catherine E. Housecroft,
• Edwin C. Constable,
• Ernst Meyer and
• Thilo Glatzel

Beilstein J. Nanotechnol. 2013, 4, 418–428, doi:10.3762/bjnano.4.49

• and the carrier transport. Smaller TiO2 particles lead to an increase of grain boundaries and reduce the solar cell current. Hence, we have considered it as relevant to characterize the surface potential of nanostructured TiO2 with a high-resolution method. Surface dipole changes upon dye adsorption

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

• 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

• proposed an explanation for the contradictory results in the investigations of FM ZnO [6]. We observed, that FM behaviour does not appear in bulk ZnO (even doped by Mn or Co), but only in polycrystalline samples with very high specific area sGB of grain boundaries (GBs), i.e., the ratio of GB area to grain

• volume [6]. Only in the case where the specific area of grain boundaries in ZnO exceeds a certain threshold called sth, does the ferromagnetism appear. If sGB is high enough, even the doping by TM ions is not essential, and FM appears in pure, undoped ZnO. The viewpoint that GBs are the reason for FM in

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

• materials is made and the importance of such arrangements in terms of nipple packing density, corneal lens curvature and potential optical properties is discussed. Keywords: butterfly-eye structure; coordination defects; sigma grain boundaries; Introduction The structure of moth and butterfly eyes consist

• creates a dislocation-type defect, rows of these defects with relatively large spacing form low-angle grain boundaries. With decreasing spacing between 5–7 coordination defects, high-angle grain boundaries are formed for which the misorientation between adjacent crystals is more than 10 degrees. In the

Micro- and nanoscale electrical characterization of large-area graphene transferred to functional substrates

• Gabriele Fisichella,
• Salvatore Di Franco,
• Patrick Fiorenza,
• Raffaella Lo Nigro,
• Fabrizio Roccaforte,
• Cristina Tudisco,
• Guido G. Condorelli,
• Nicolò Piluso,
• Noemi Spartà,
• Stella Lo Verso,
• Corrado Accardi,
• Cristina Tringali,
• Sebastiano Ravesi and
• Filippo Giannazzo

Beilstein J. Nanotechnol. 2013, 4, 234–242, doi:10.3762/bjnano.4.24

• is reported, showing the typical size of Cu grains, ranging from about 20 to 200 μm. The graphene membrane, uniformly covering the Cu foil, is mostly composed of a single layer of graphene (over 90% of the surface area), while bilayers or multilayers can be typically found at Cu grain boundaries. A

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

• electrolyte, at 50 °C, by applying Uc = −500 mV between cathode and anode. Several zones of light and dark contrast reveal several grain boundaries along the wire axis. The TEM image in Figure 8c depicts a single-crystalline wire deposited with the cyanidic electrolyte at Uc = −900 mV and 60 °C, while the

• investigations of the electrical transport properties of metal and semiconductor nanowires are necessary in order to better understand classical size effects such as electron scattering at surfaces and grain boundaries. These effects lead to an increase of the specific resistivity of the wire under study

• path, average grain size, and a reflection coefficient at the grain boundaries [128]. The effect of surface scattering was predicted by Dingle et al., and is influenced by nanowire diameter and the specularity of scattering processes at the wire surface [129]. Absolute measurements of the specific

Tuning the properties of magnetic thin films by interaction with periodic nanostructures

• Ulf Wiedwald,
• Felix Haering,
• Stefan Nau,
• Carsten Schulze,
• Herbert Schletter,
• Denys Makarov,
• Alfred Plettl,
• Karsten Kuepper,
• Manfred Albrecht,
• Johannes Boneberg and
• Paul Ziemann

Beilstein J. Nanotechnol. 2012, 3, 831–842, doi:10.3762/bjnano.3.93

• ; Introduction Perpendicular recording media currently in use consist of magnetic CoCrPt grains that are exchange-decoupled from each other by a thin layer of Si oxide or Ti oxide at the grain boundaries. A single magnetic bit is stored on the hard disk by magnetizing a small region consisting of several tens of

Reversible mechano-electrochemical writing of metallic nanostructures with the tip of an atomic force microscope

• Christian Obermair,
• Marina Kress,
• Andreas Wagner and
• Thomas Schimmel

Beilstein J. Nanotechnol. 2012, 3, 824–830, doi:10.3762/bjnano.3.92

• defects and grain boundaries. The deposited metal in the beginning of the deposition process thus forms a chain of islands along the path of the AFM tip. These islands finally touch and overgrow each other, in this way forming a continuous wire in the shape of the digit “6”. The line width of the

Dimer/tetramer motifs determine amphiphilic hydrazine fibril structures on graphite

• Loji K. Thomas,
• Nadine Diek,
• Uwe Beginn and
• Michael Reichling

Beilstein J. Nanotechnol. 2012, 3, 658–666, doi:10.3762/bjnano.3.75

• 1CHn-10 and 2CHd-10 to produce fibrils (as evident from the AFM images), the absence of grain boundaries and single/multiple steps near the molecular wires [25] (which are the two most important causes for their appearance), and the discrepancy in periodicities between molecular structures and reported

Effect of deposition temperature on the structural and optical properties of chemically prepared nanocrystalline lead selenide thin films

• Anayara Begum,
• Amir Hussain and
• Atowar Rahman

Beilstein J. Nanotechnol. 2012, 3, 438–443, doi:10.3762/bjnano.3.50

• due to a decrease in the occurrence of grain boundaries because of an increase in the crystallite size of the film with increasing temperature. Surface morphology Scanning electron microscopy gives valuable information regarding the shape and size of the grains on the surface of the deposited thin

Junction formation of Cu₃BiS₃ investigated by Kelvin probe force microscopy and surface photovoltage measurements

• Fredy Mesa,
• William Chamorro,
• William Vallejo,
• Robert Baier,
• Thomas Dittrich,
• Alexander Grimm,
• Martha C. Lux-Steiner and
• Sascha Sadewasser

Beilstein J. Nanotechnol. 2012, 3, 277–284, doi:10.3762/bjnano.3.31

• distribution for In2S3 compared to that of CdS and ZnS. For In2S3 and CdS buffer layers the KPFM experiments indicate negatively charged Cu3BiS3 grain boundaries resulting from the deposition of the buffer layer. Macroscopic measurements of the surface photovoltage at variable excitation wavelength indicate

• , such as chemical bath deposition, atomic layer deposition, ion layer gas reaction (ILGAR) deposition, evaporation, and spray deposition [9]. One interesting aspect of the above mentioned solar cell materials CdTe and Cu(In,Ga)Se2 is their high efficiency despite the abundance of grain boundaries (GBs

• ). Scanning probe microscopy experiments have provided significant insight into the physics of grain boundaries on these materials [10]. Specifically, recent experiments provided evidence for the benign properties of the GBs [11][12], in agreement with previous theoretical work [13][14]. Also the influence of

Nanoscaled alloy formation from self-assembled elemental Co nanoparticles on top of Pt films

• Luyang Han,
• Ulf Wiedwald,
• Johannes Biskupek,
• Kai Fauth,
• Ute Kaiser and
• Paul Ziemann

Beilstein J. Nanotechnol. 2011, 2, 473–485, doi:10.3762/bjnano.2.51

• exhibiting grain sizes (20–30 nm) smaller than the particle spacing (100 nm), the formation of local nanoalloys at the surface is strongly suppressed and Co incorporation into the film via grain boundaries is favoured. In contrast, due to the absence of grain boundaries on high quality epitaxial Pt(100

• restricted by a photoelectron mean free path of about 1.6 nm [27]. Rather, diffusion along the large number of grain boundaries in the Pt(111) film on MgO(100) is expected. On Pt(100) films with micron-sized, atomically-flat surfaces this diffusion channel does not exist for most of the NPs, thus markedly

• reduced Co content after annealing suggests that Co atoms diffuse away from the surface along grain boundaries at elevated temperature. Thus, we speculate that after annealing the size-reduced NPs on Pt(111) remain in a pure Co, or at least Co-rich, phase having a rather low orbital moment. Nevertheless

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

• agglomeration [32][33], voids can nucleate due to periodic film thickness fluctuations (spinodal dewetting), or at defects, which is then followed by void growth and particle formation [31]. For polycrystalline metallic films, dewetting is also affected by the character of grain boundaries [33]. Altogether

• , 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

Schottky junction/ohmic contact behavior of a nanoporous TiO₂ thin film photoanode in contact with redox electrolyte solutions

• Masao Kaneko,
• Hirohito Ueno and
• Junichi Nemoto

Beilstein J. Nanotechnol. 2011, 2, 127–134, doi:10.3762/bjnano.2.15

• are transported first to the fluorine-doped tin oxide (FTO, SnO2:F) conductive layer through TiO2 grain boundaries and then to the cathode reducing electron acceptor there (O2 in the present case). In a Schottky junction, under the conditions when the band structure is flat without any bending, the

• . The thin space charge layer is located at the interface between TiO2 and the liquid, and the band structure (CB and VB) in the TiO2 bulk is interconnected through the TiO2 grain boundaries forming continuous CB electron-transporting channels from the space charge layer to reach the conductive layer on

• separated into electrons and holes due to the slope of the VB and CB bands, the h+ then being reduced by MeOH present in the liquid, and the e− being transported in the CB through TiO2 grain boundaries to the counter cathode via the FTO. As reported earlier by us [13], resistances at the grain boundaries

Defects in oxide surfaces studied by atomic force and scanning tunneling microscopy

• Thomas König,
• Georg H. Simon,
• Lars Heinke,
• Leonid Lichtenstein and
• Markus Heyde

Beilstein J. Nanotechnol. 2011, 2, 1–14, doi:10.3762/bjnano.2.1

• trapped charge on the surface dipole. This demonstrates the great benefit of NC-AFM and KPFM in combination with STM and STS. Line defects Apart from point defects more complex structures like line defects are found on oxide surfaces. Line defects can be caused by step edges or grain boundaries that