High I_on/I_off current ratio graphene field effect transistor: the role of line defect

• Mohammad Hadi Tajarrod and
• Hassan Rasooli Saghai

Beilstein J. Nanotechnol. 2015, 6, 2062–2068, doi:10.3762/bjnano.6.210

• transistor devices [5][6]. The electronic properties of graphene are the result of its particular structure. In order to modify the transport behavior, the physical structure of graphene needs to be changed. Consequently, topological defects such as vacancies, impurities, adatoms and Stone–Wales defects are

Nitrogen-doped graphene films from chemical vapor deposition of pyridine: influence of process parameters on the electrical and optical properties

• Andrea Capasso,
• Theodoros Dikonimos,
• Francesca Sarto,
• Alessio Tamburrano,
• Giovanni De Bellis,
• Maria Sabrina Sarto,
• Giuliana Faggio,
• Angela Malara,
• Giacomo Messina and
• Nicola Lisi

Beilstein J. Nanotechnol. 2015, 6, 2028–2038, doi:10.3762/bjnano.6.206

• [17]. Besides, the electron mobility itself can be greatly affected by the presence of substitutional atoms (which are a kind of lattice defects, such as vacancies, and grain boundaries) [18]. Graphene can be doped through surface proximity by layering it with other materials (such as metals [19

Distribution of Pd clusters on ultrathin, epitaxial TiO_x films on Pt₃Ti(111)

• Christian Breinlich,
• Maria Buchholz,
• Marco Moors,
• Tobias Pertram,
• Conrad Becker and
• Klaus Wandelt

Beilstein J. Nanotechnol. 2015, 6, 2007–2014, doi:10.3762/bjnano.6.204

• (i.e., oxygen vacancies) in this structure are confined to these trenches and act as nucleation sites. Therefore, the Pd clusters are mostly arranged in unidirectional rows along the trenches, creating a template effect. The second phase, w'-TiOx, exhibits a hexagonal, long range, (7 × 7)R21.8°, Moiré

• ) standard surface science techniques can be applied due to the high conductivity of these films compared to the respective bulk oxides, (b) the films can be prepared with a very high degree of structural preciseness, and (c) the influence of bulk effects such as subsurface oxygen vacancies is excluded. In

Possibilities and limitations of advanced transmission electron microscopy for carbon-based nanomaterials

• Xiaoxing Ke,
• Carla Bittencourt and
• Gustaaf Van Tendeloo

Beilstein J. Nanotechnol. 2015, 6, 1541–1557, doi:10.3762/bjnano.6.158

• subsequent reconstruction of large even-number vacancies takes place, as discussed in detail in [43]. One example is shown in Figure 4a,b. When carbon atoms in CNTs are displaced by electron irradiation, single vacancies (SV), divacancies (DV), and even tetravacancies can be created; a schematic illustration

• is presented in Figure 4a,b. Displaced carbon atoms may form adatoms (A) on the lattice. Atomistic computer simulations predict that the reconstruction of the atomic network near vacancies and adatoms is very likely to happen, resulting in an agglomeration of 5- to 8-membered rings [44][45]. As shown

• thus provide a HRTEM image with an acceptable signal to noise ratio with only limited damage to the sample. The introduction of a high-speed detector may also have an impact on increasing the time resolution. In a molecular dynamics simulations on the reconstruction of vacancies, the time scale is

Transformations of PTCDA structures on rutile TiO₂ induced by thermal annealing and intermolecular forces

• Szymon Godlewski,
• Jakub S. Prauzner-Bechcicki,
• Thilo Glatzel,
• Ernst Meyer and
• Marek Szymoński

Beilstein J. Nanotechnol. 2015, 6, 1498–1507, doi:10.3762/bjnano.6.155

• located in between. The overall STM appearance is much different from the surface topography. Additional bright spots recorded within dark oxygen rows are attributed to oxygen vacancies (fainter spots) or single and double surface hydroxy groups (brighter spots). The oxygen vacancies are created during

• the preparation procedure, leading to a slight reduction of the sample and decreasing the intrinsic band gap from approximately 3.0 eV to 1.5–2.5 eV. Hydroxy groups are created as a result of atomic hydrogen adsorption and dissociative adsorption of water at oxygen vacancies. The surface is very

• sensitive to the presence of water among residual gases and therefore the maintenance of the high vacuum level during sample preparation plays a crucial role. The adopted experimental procedure enables us to obtain clean surfaces with several oxygen vacancies and some hydroxy groups after final annealing

Enhanced fullerene–Au(111) coupling in (2√3 × 2√3)R30° superstructures with intermolecular interactions

• Michael Paßens,
• Rainer Waser and
• Silvia Karthäuser

Beilstein J. Nanotechnol. 2015, 6, 1421–1431, doi:10.3762/bjnano.6.147

• ” C60 [8][16], are observed in different structural domains. In a systematic study Gardener et al. [16] proposed, that the reason for the dim C60 are nanopits, also called vacancies, which are formed at the C60–Au interface. Dim C60 molecules adsorbed at vacancies are lower in height than the bright C60

• reconstruction [16] or the forming of a new surface arrangement at the C60–Au interface depending on the thermal treatment [24][25]. The number and the distribution of dim C60 molecules adsorbed on vacancies differ in the respective superstructures on Au(111). While very few dim C60 molecules are randomly

• is commonly called “disordered”. Interestingly, this (2√3 × 2√3)R30° superstructure shows a dynamic bright–dim flipping near room temperature, which points to highly mobile vacancies at the C60–Au(111) interface [16][26]. Recently, also a uniform (2√3 × 2√3)R30° structure with all C60 molecules

The Kirkendall effect and nanoscience: hollow nanospheres and nanotubes

• Abdel-Aziz El Mel,
• Ryusuke Nakamura and
• Carla Bittencourt

Beilstein J. Nanotechnol. 2015, 6, 1348–1361, doi:10.3762/bjnano.6.139

• , the position of the initial interface changes during the annealing process since the atomic diffusion coefficients of atom A in metal B and of atom B in metal A are different. As a consequence of the unbalanced diffusion rates between the two stacked metals, vacancies will be injected at the interface

• region will be more extended within metal B and vacancies will be injected at the interface region within metal A (Figure 2b). The coalescence of excess of vacancies leads to the formation of small voids distributed all along the interface. As the annealing process progresses in time, vacancies will be

• , vacancies are created and injected at the Co(core)/CoSe(shell) interface. The migration and agglomeration of vacancies result in the formation and merging of the initial voids located at the interface and extended along the Co core (Figure 4a). The increase in size of these voids was found to lead to the

High photocatalytic activity of V-doped SrTiO₃ porous nanofibers produced from a combined electrospinning and thermal diffusion process

• Panpan Jing,
• Wei Lan,
• Qing Su and
• Erqing Xie

Beilstein J. Nanotechnol. 2015, 6, 1281–1286, doi:10.3762/bjnano.6.132

• above room temperature in air, generally, the oxygen vacancy is one of the most important defects that can be easily introduced [31]. The crystal cell is then distorted and the cell volume or lattice constant is reduced. However, if a few Ti4+ ions are substituted by V5+ ions, some oxygen vacancies will

Characterization of nanostructured ZnO thin films deposited through vacuum evaporation

• Jose Alberto Alvarado,
• Arturo Maldonado,
• Héctor Juarez,
• Mauricio Pacio and
• Rene Perez

Beilstein J. Nanotechnol. 2015, 6, 971–975, doi:10.3762/bjnano.6.100

• . There are a lot of emission lines related to the characteristics of the deposited thin films, as the annealing temperature and the intrinsic defects (VZn, VO). One of the emissions is in the blue region, which is close to 2.6 and 2.5 eV, and refers to the Zn vacancies. The emission close to 1.6 eV (red

• region) corresponds to oxygen vacancies (VO). The emission intensities are similar intensity for the thin films annealed at 400 and 25 °C. They change drastically when we have the nanostructures deposited as thin film where the main emission line attributed to VZn is related to the form of the

Graphene on SiC(0001) inspected by dynamic atomic force microscopy at room temperature

• Mykola Telychko,
• Jan Berger,
• Zsolt Majzik,
• Pavel Jelínek and
• Martin Švec

Beilstein J. Nanotechnol. 2015, 6, 901–906, doi:10.3762/bjnano.6.93

• SLG and BLG graphene, (e) 6.4 × 6.4 nm2, Vbias = −0.2 V, I = 0.16 nA; × near to vacancies created by ion etching. (Color online) (a) Spectroscopy curves of average tunneling current , Δf and force F vs the tip–sample distance on graphene/SiC(0001), taken with a bias voltage of 100 mV, just before

Transformation of hydrogen titanate nanoribbons to TiO₂ nanoribbons and the influence of the transformation strategies on the photocatalytic performance

• Melita Rutar,
• Nejc Rozman,
• Matej Pregelj,
• Carla Bittencourt,
• Romana Cerc Korošec,
• Andrijana Sever Škapin,
• Aleš Mrzel,
• Srečo D. Škapin and
• Polona Umek

Beilstein J. Nanotechnol. 2015, 6, 831–844, doi:10.3762/bjnano.6.86

• vacancies [35][41]. In addition to this resonance, in the samples that were treated in reductive atmosphere, i.e., in TN-400, TN-580 and TN-650, exhibit another intense line at g ≈ 1.988, which is assigned to the Ti3+ centers in the bulk. Moreover, as the reaction temperature increases the intensity of this

• ., TO-580, TN-400 and TN-580, both resonances that were observed at room temperature (Figure 8) increase, i.e., the number of oxygen vacancies and the Ti3+ ions increases. Moreover, the former are most likely responsible also for the resonances appearing at g values [35][41] of approx. 2.012, and approx

• within the band-gap states created by substitutional and interstitional N-doping [23][36] and to creation of an additional localized state due to oxygen vacancies below the conduction band [36]. Assessment of the photocatalytic performance of the TiO2 NRs The photocatalytic performance (PP) of the

Tm-doped TiO₂ and Tm₂Ti₂O₇ pyrochlore nanoparticles: enhancing the photocatalytic activity of rutile with a pyrochlore phase

• Desiré M. De los Santos,
• Javier Navas,
• Teresa Aguilar,
• Antonio Sánchez-Coronilla,
• Concha Fernández-Lorenzo,
• Rodrigo Alcántara,
• Jose Carlos Piñero,
• Ginesa Blanco and
• Joaquín Martín-Calleja

Beilstein J. Nanotechnol. 2015, 6, 605–616, doi:10.3762/bjnano.6.62

• , respectively, confirming the presence of Tm(III) in an oxide matrix. Thus, considering that the predominant cations in the TiO2 lattice of the doped samples are Ti4+ and Tm3+, and that the doping is substitutional, oxygen vacancies are generated to maintain the local neutrality of the lattice. The presence of

• oxygen vacancies is interesting for photocatalytic applications because, for example, an increase in oxygen vacancies generates more surface defects on the synthesized nanoparticles. This can be studied from the O 1s XPS spectra. Figure 2c (bottom) shows the different contributions in the O 1s spectrum

• demonstrates how the amount of O in the adsorbed species increases with the Tm concentration. This is due to the increase in oxygen vacancies produced, and thus in the number of adsorption centers available. The adsorption of hydroxy groups onto the surface is of interest in photocatalytic applications

Novel ZnO:Ag nanocomposites induce significant oxidative stress in human fibroblast malignant melanoma (Ht144) cells

• Syeda Arooj,
• Samina Nazir,
• Akhtar Nadhman,
• Nafees Ahmad,
• Bakhtiar Muhammad,
• Ishaq Ahmad,
• Kehkashan Mazhar and
• Rashda Abbasi

Beilstein J. Nanotechnol. 2015, 6, 570–582, doi:10.3762/bjnano.6.59

• possible presence of the ZnO2 structure. The minor variation in oxygen amount is, however, due to oxygen vacancies created by the Fermi gas we used in our annealing procedure. These oxygen vacancies gradually obtained some atmospheric oxygen when samples were stored under normal atmospheric conditions. The

Chains of carbon atoms: A vision or a new nanomaterial?

• Florian Banhart

Beilstein J. Nanotechnol. 2015, 6, 559–569, doi:10.3762/bjnano.6.58

• layers led to growing vacancies and holes. The phenomenon has been confirmed later [39][40]; in some experiments even two parallel chains were observed once a graphene ribbon has been thinned laterally to a certain minimum width. The narrowing graphene ribbons between two holes ended in atomic chains as

• is around 80 keV [75]. Undercoordinated edge atoms can be sputtered off at lower energies although the edges tend to reconstruct [76]. The same holds for atoms next to unreconstructed vacancies. As for graphene, the displacement threshold for carbon chains should be highly asymmetric, being much

Nanoporous Ge thin film production combining Ge sputtering and dopant implantation

• Jacques Perrin Toinin,
• Alain Portavoce,
• Khalid Hoummada,
• Michaël Texier,
• Maxime Bertoglio,
• Sandrine Bernardini,
• Marco Abbarchi and
• Lee Chow

Beilstein J. Nanotechnol. 2015, 6, 336–342, doi:10.3762/bjnano.6.32

• of the Ge film up to a depth of 140 nm. One can observe in Figure 1 that no dopants and no vacancies are expected to be found at a depth larger than 220 nm. Consequently, the implantation-induced defects should be confined in the Ge layer thickness. Figure 2 presents scanning electron microscopy (SEM

• straight lines on the right axis and the vacancies distributions are shown using dashed lines on the left axis. SEM plan-view images of the as-implanted Se sample: (1) low resolution view showing the different types of defects; (2) a single GeOx cluster; (3) the structure of holes; and (4) the nanoporous

Tunable white light emission by variation of composition and defects of electrospun Al₂O₃–SiO₂ nanofibers

• Jinyuan Zhou,
• Gengzhi Sun,
• Hao Zhao,
• Xiaojun Pan,
• Zhenxing Zhang,
• Yujun Fu,
• Yanzhe Mao and
• Erqing Xie

Beilstein J. Nanotechnol. 2015, 6, 313–320, doi:10.3762/bjnano.6.29

• -like heterostructure composed of SiOx particles orderly embedded in the highly crystalline α-Al2O3 nanoribbons. They observed a strong and stable blue emission centered at 467 nm under excitation at 320 nm, which was attributed to the neutral oxygen vacancies (≡Si–Si≡) in the SiOx–Al2O3 heterostructure

Morphology, structural properties and reducibility of size-selected CeO_2−x nanoparticle films

• Maria Chiara Spadaro,
• Sergio D’Addato,
• Gabriele Gasperi,
• Francesco Benedetti,
• Paola Luches,
• Vincenzo Grillo,
• Giovanni Bertoni and
• Sergio Valeri

Beilstein J. Nanotechnol. 2015, 6, 60–67, doi:10.3762/bjnano.6.7

• electrostatic force. With the assumption that the increase of the lattice parameter is also due to a higher concentration of oxygen vacancies, Tsunekawa results are complementary with the ones of Zhou et al. [7], obtained for NP diameters between 4 and 60 nm. These results led to the conclusion that the lattice

• parameter increase is related to the formation of oxygen vacancies and Ce3+ ions. Following this approach, Deshpande et al. [8] correlated the lattice parameter expansion with the concentration of Ce3+ ions (measured by X-ray photoelectron spectroscopy, XPS), ascribing it to the higher ionic radius of Ce3

• +, compared to the Ce4+, and to the introduction of oxygen vacancies, which in turn induces a distortion of the local symmetry. In the last years a ‘Madelung model’ has been proposed to describe the properties of ionic crystals as a function of their surface to volume ratio. Here, the balance between long

Manganese oxide phases and morphologies: A study on calcination temperature and atmospheric dependence

• Matthias Augustin,
• Daniela Fenske,
• Ingo Bardenhagen,
• Anne Westphal,
• Martin Knipper,
• Thorsten Plaggenborg,
• Joanna Kolny-Olesiak and
• Jürgen Parisi

Beilstein J. Nanotechnol. 2015, 6, 47–59, doi:10.3762/bjnano.6.6

• especially useful for application as molecular sieves and absorbents for the removal of toxic species from waste gases such as carbon monoxide and nitrogen oxide [6][7][8]. Additionally, manganese oxide structures exhibiting oxygen vacancies provide additional active sites for reduction and oxidation

• crystallite sizes of less than a third compared to those obtained in O2. Furthermore, the lattice constants of Mn3O4 produced in Ar are smaller at all temperatures than those obtained by calcination in O2 atmosphere. This could be due to oxygen vacancies, as the oxygen for the oxidation to Mn3O4 in pure Ar is

• only supplied by the manganese glycolate precursor and cannot be obtained from the gas atmosphere. The presence of oxygen vacancies is also supported by the less pronounced variation of the lattice constants of Mn3O4 obtained at 320 °C and 350 °C in O2 atmospheres, leading to the assumption of

Liquid-phase exfoliated graphene: functionalization, characterization, and applications

• Mildred Quintana,
• Jesús Iván Tapia and
• Maurizio Prato

Beilstein J. Nanotechnol. 2014, 5, 2328–2338, doi:10.3762/bjnano.5.242

• vacancies, adatoms or substitutional atoms might act as active chemical sites on the graphene layer [37]. These features make the organic chemistry of graphene very accessible, but only partially understood. Improvement in the chemical knowledge of the two dimensional material is expected to increase the

Patterning a hydrogen-bonded molecular monolayer with a hand-controlled scanning probe microscope

• Matthew F. B. Green,
• Taner Esat,
• Christian Wagner,
• Philipp Leinen,
• Alexander Grötsch,
• F. Stefan Tautz and
• Ruslan Temirov

Beilstein J. Nanotechnol. 2014, 5, 1926–1932, doi:10.3762/bjnano.5.203

• consisting of 47 vacancies that were created by removing individual PTCDA molecules from the PTCDA/Ag(111) monolayer. The sequence of intermediate steps recorded during writing can be downloaded from the supplement. The three insets show the “repair” of a vacancy created by mistake. The black arrow marks the

• position of the error vacancy. The white arrow marks the position of the molecule at the edge of the molecular monolayer island that was used to fill the error vacancy. The molecule from the edge was removed by using the same manipulation protocol as for all other vacancies and was then placed into the

Synthesis of Pt nanoparticles and their burrowing into Si due to synergistic effects of ion beam energy losses

• Pravin Kumar,
• Udai Bhan Singh,
• Kedar Mal,
• Sunil Ojha,
• Indra Sulania,
• Dinakar Kanjilal,
• Dinesh Singh and
• Vidya Nand Singh

Beilstein J. Nanotechnol. 2014, 5, 1864–1872, doi:10.3762/bjnano.5.197

• interface at ≈242 nm below the surface is clearly seen in Figure 5a. This is mainly attributed to the amorphization of the silicon by collision cascade which can propagate even further than the range of ions (see Si vacancies profile distribution in Figure 6). Figure 5b, which is the zoomed image of the

• . Therefore, local defects (especially vacancies) produced by elastic collisions, which are governed by Sn, are mainly responsible for the burrowing of NPs in silicon as also discussed by Hu et al. [22]. Given the irradiation parameters (50 keV energy, 1 µA beam current and 16 × 103 s to irradiate 1017 ions

• silicon is estimated to be ≈50 nm. Therefore, the presence of NPs beneath the surface and up to ≈250 nm is probably due to radiation-induced enhanced diffusion. Holm et al. [41] have reported Pt distribution into lightly damaged regions of silicon approximately congruous to the vacancies generated during

Silicon and germanium nanocrystals: properties and characterization

• Ivana Capan,
• Alexandra Carvalho and
• José Coutinho

Beilstein J. Nanotechnol. 2014, 5, 1787–1794, doi:10.3762/bjnano.5.189

• by varying the implantation conditions (implantation energy and dose) and subsequent annealing. It is a well-known fact that Si ion implantation of SiO2 is characterized by the production of a large number of oxygen vacancies and other defects in the oxide matrix. These defects enhance the QD

On the structure of grain/interphase boundaries and interfaces

• K. Anantha Padmanabhan and
• Herbert Gleiter

Beilstein J. Nanotechnol. 2014, 5, 1603–1615, doi:10.3762/bjnano.5.172

• as vacancies and extra occupancies, are due to the details of the electronic structure requirements and not just structural defects [19][20][21]. In these cases, the formation of structural/basic units will depend on the separation between the atoms and the nature (metallic, ionic or covalent) of the

Effects of palladium on the optical and hydrogen sensing characteristics of Pd-doped ZnO nanoparticles

• Anh-Thu Thi Do,
• Hong Thai Giang,
• Thu Thi Do,
• Ngan Quang Pham and
• Giang Truong Ho

Beilstein J. Nanotechnol. 2014, 5, 1261–1267, doi:10.3762/bjnano.5.140

• the gas sensing response characteristics allows us to suggest that the dissociation of hydrogen takes place at PdZn-vacancies ([Pd 2+(4d9)]). The design of this sensor allows for a continuous monitoring in the range of 0–100% LEL H2 concentration with high sensitivity and selectivity. Keywords

• interstitials, Zn anti-site vacancies, and oxygen vacancies, it is of interest to find out whether Pd incorporated in ZnO significantly improves sensitivity and specificity for hydrogen [13][14]. In this work, we have successfully synthesized Pd-doped ZnO nanoparticles for an application as gas sensors by a low

• -temperature wet-chemical process. Photoluminescence (PL) measurements at room temperature are then carried out in order to determine the role of vacancies, trapping levels, and the transition shift of the PL emission maximum in these samples. In order to study and optimize the four main factors affecting the

Sublattice asymmetry of impurity doping in graphene: A review

• James A. Lawlor and
• Mauro S. Ferreira

Beilstein J. Nanotechnol. 2014, 5, 1210–1217, doi:10.3762/bjnano.5.133

• lattice sites yields no band gap [17]. Further investigations using vacancies, where carbon atoms are removed from the lattice, found that both superlattices [18] and random distributions restricted to one of the two graphene sublattices [19] both lead to a tunable band gap, and in the latter case an