Focused electron beam induced deposition: A perspective

• Michael Huth,
• Fabrizio Porrati,
• Christian Schwalb,
• Marcel Winhold,
• Roland Sachser,
• Maja Dukic,
• Jonathan Adams and
• Georg Fantner

Beilstein J. Nanotechnol. 2012, 3, 597–619, doi:10.3762/bjnano.3.70

• -energy tail: with the work function Φ. For FEBID, in particular with a view to the microstructure of the typically obtained inhomogeneous deposits, which then act as a “growing substrate”, the spectrum of secondary electrons is a priori unknown. Considering the fact that the radial density distribution

Low-temperature synthesis of carbon nanotubes on indium tin oxide electrodes for organic solar cells

• Andrea Capasso,
• Luigi Salamandra,
• Aldo Di Carlo,
• John M. Bell and
• Nunzio Motta

Beilstein J. Nanotechnol. 2012, 3, 524–532, doi:10.3762/bjnano.3.60

• solar cells based on poly(3-hexylthiophene) (P3HT) and phenyl-C61-butyric acid methyl ester (PCBM), the MWCNT-enhanced electrodes are found to improve the charge-carrier extraction from the photoactive blend, thanks to the additional percolation paths provided by the CNTs. The work function of as

• these parameters it is possible to create MWCNT mats with the required size and density on the ITO-coated glass surface. Such CNT-enhanced electrodes are found to show advantages in terms of work-function (WF) matching and electrical properties in comparison with pristine ITO electrodes, contributing to

• ” and the Project “Polo Solare Organico - Regione Lazio”. One of the authors (A.C.) would like to thank Dr. Gianlorenzo Bussetti for his help and significant considerations to the work-function measurements, and Mr. Paul Moonie for critical reading of the manuscript.

Imaging ultra thin layers with helium ion microscopy: Utilizing the channeling contrast mechanism

• Gregor Hlawacek,
• Vasilisa Veligura,
• Stefan Lorbek,
• Tijs F. Mocking,
• Antony George,
• Raoul van Gastel,
• Harold J. W. Zandvliet and
• Bene Poelsema

Beilstein J. Nanotechnol. 2012, 3, 507–512, doi:10.3762/bjnano.3.58

• build-up in the irradiated sample area [5]. Contrast in SE images is primarily based on differences in work function and the yield of SE generation in the region near the surface [6]. As a consequence, HIM has an unprecedented surface sensitivity in SE mode. Together with the high lateral resolution

• relatively low work function of SiO2, these areas are brightest. The work functions of PFS and MS are 6.6 eV and 5.3 eV [13], respectively. The value for PFS was extrapolated from a shorter fluorinated alkanethiol [14], and should be treated as an estimate. We can therefore identify the medium light-gray

• areas below and above the Si patches as being MS-covered. The medium dark areas to the left and the right of the Si patches are covered by the higher-work-function PFS layer. The remaining square is covered by an unknown mixture of both, MS and PFS. A clear statement on the work function or the contrast

Channeling in helium ion microscopy: Mapping of crystal orientation

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

Beilstein J. Nanotechnol. 2012, 3, 501–506, doi:10.3762/bjnano.3.57

• rougher surface will have a smaller work function, which allows a higher number of SE to escape. In Figure 4a the average SE yield of several grains is plotted versus the azimuthal angle for two different primary energies. The SE yield of individual grains has been normalized with respect to the maximum

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

• of metals and metal-oxide materials [6]. Previously, when foreign receptors were introduced into MOx sensor grains, sensitizing actions were observed, particularly when they modified the work function and surface space-charge layer of the sensor material [7]. Another significant effect that may arise

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

• to be developed. We present an investigation of the Cu3BiS3 absorber layer and the junction formation with CdS, ZnS and In2S3 buffer layers. Kelvin probe force microscopy shows the granular structure of the buffer layers with small grains of 20–100 nm, and a considerably smaller work-function

• is important to know the state of the surface of the examined sample. Surface oxidation can modify the work function of the sample and complicate data analysis. To clean the surface of Cu3BiS3 samples, we used an NH3 treatment prior to introduction into the ultrahigh-vacuum (UHV) system of the KPFM

• reference also on the pure Cu3BiS3 surface after NH3 etching. Figure 2 shows the results on all surfaces, in which the topography is shown in the upper row, the derivative of the topography in the second row, and the work-function image in the third row; a histogram displaying the work-function distribution

Noncontact atomic force microscopy study of the spinel MgAl₂O₄(111) surface

• Morten K. Rasmussen,
• Kristoffer Meinander,
• Flemming Besenbacher and
• Jeppe V. Lauritsen

Beilstein J. Nanotechnol. 2012, 3, 192–197, doi:10.3762/bjnano.3.21

• between two consecutive crystal planes in the [111] direction, i.e., between the O3–O and the Al3 layer (Figure 1a). However, it is well known that the atomic-level NC-AFM contrast in topographic measurements between two areas with a different chemical composition may be affected by work-function

Molecular-resolution imaging of pentacene on KCl(001)

• Julia L. Neff,
• Jan Götzen,
• Enhui Li,
• Michael Marz and
• Regina Hoffmann-Vogel

Beilstein J. Nanotechnol. 2012, 3, 186–191, doi:10.3762/bjnano.3.20

• -range electrostatic forces, the tip–sample work-function difference was compensated by application of the appropriate bias voltage to the tip. Results and Discussion Figure 1a shows the KCl(001) surface with submonolayer coverage of pentacene molecules forming an extended island over several microns

Transmission eigenvalue distributions in highly conductive molecular junctions

• Justin P. Bergfield,
• Joshua D. Barr and
• Charles A. Stafford

Beilstein J. Nanotechnol. 2012, 3, 40–51, doi:10.3762/bjnano.3.5

• various bonding configurations, we also consider an ensemble of junctions to sample all possible Pt surfaces. The work function of Pt ranges from 5.93 eV for the (111) surface to 5.12 eV for the (331) surface [24], and we assume that μPt is distributed uniformly over this interval. Using this ensemble

• of the HOMO or LUMO resonance, respectively. These data are in good agreement with the measurements of [4]. The work-function range for the crystal planes of Pt is shaded in blue, where −5.93 eV ≤ μPt ≤ −5.12 eV [24]. The calculated Fano factor F distribution for the full ensemble of 1.74 × 105 Pt

• ionization energy of the neutral molecule [17][18][19][20][22], and the vertical electron affinity of the neutral molecule [23]. The asymmetry in the average spectral function arises because the HOMO resonance couples more strongly on average to the Pt tip atoms than does the LUMO resonance. The work

X-ray spectroscopy characterization of self-assembled monolayers of nitrile-substituted oligo(phenylene ethynylene)s with variable chain length

• Hicham Hamoudi,
• Ping Kao,
• Alexei Nefedov,
• David L. Allara and
• Michael Zharnikov

Beilstein J. Nanotechnol. 2012, 3, 12–24, doi:10.3762/bjnano.3.2

• ranging from one to three structural units) was described in [38]. The authors, however, presented only results for the SAM-induced work-function tuning and did not provide any information about the SAM structure or packing density. Results High-resolution X-ray photoelectron spectroscopy High-resolution

Self-assembled monolayers and titanium dioxide: From surface patterning to potential applications

• Yaron Paz

Beilstein J. Nanotechnol. 2011, 2, 845–861, doi:10.3762/bjnano.2.94

• semiconductors (Si, GaN, InP, InGaAs) provide a unique way to alter the properties of a surface at will. This ability may be manifested through a variety of phenomena, among which are wetting phenomena (hydrophobicity, hydrophilicity and oleophobicity), electronic phenomena (from affecting band bending and work

• function, to charge conduction), and, no less important, the ability to form tailored three-dimensional supramolecular arrays by attaching a specific molecule or a particle to an external functional group. Being adsorbed on the surface of titanium dioxide or in its vicinity, organic self-assembled

Towards quantitative accuracy in first-principles transport calculations: The GW method applied to alkane/gold junctions

• Mikkel Strange and
• Kristian S. Thygesen

Beilstein J. Nanotechnol. 2011, 2, 746–754, doi:10.3762/bjnano.2.82

• corresponding to double-zeta plus polarization (DZP) for the Au atoms and double-zeta (DZ) for the atoms of the molecules. We use rather diffuse basis functions with a confinement-energy shift of 0.01 eV. This ensures that the calculated work function of Au(111) and the Kohn–Sham energy levels of the molecular

Highly efficient ZnO/Au Schottky barrier dye-sensitized solar cells: Role of gold nanoparticles on the charge-transfer process

• Tanujjal Bora,
• Htet H. Kyaw,
• Soumik Sarkar,
• Samir K. Pal and
• Joydeep Dutta

Beilstein J. Nanotechnol. 2011, 2, 681–690, doi:10.3762/bjnano.2.73

• to the I−/I3− redox electrolyte. The formation of the Schottky barrier at the ZnO/Au interface can be explained from the classical Schottky model, according to which a Schottky barrier forms at a semiconductor/metal junction when the work function of the metal (θM) is higher than the electron

• affinity of the semiconductor (χS) and the barrier height (θSB) at the junction can be expressed as given in Equation 1. In the ZnO/Au-nanocomposite system, due to the larger work function of Au (5.1 eV) [21] compared the electron affinity of ZnO (4.2 eV) [24], a Schottky barrier exists at their interface

Distinguishing magnetic and electrostatic interactions by a Kelvin probe force microscopy–magnetic force microscopy combination

• Miriam Jaafar,
• Oscar Iglesias-Freire,
• Luis Serrano-Ramón,
• Manuel Ricardo Ibarra,
• Jose Maria de Teresa and
• Agustina Asenjo

Beilstein J. Nanotechnol. 2011, 2, 552–560, doi:10.3762/bjnano.2.59

• the topography of organic and inorganic materials and to study chemical (composition), mechanical (including friction and stiffness, etc.), electrical (surface potential, work function), magnetic (domain structure) or biological (specific recognition) properties. A priori, the unknown contribution of

• known that an electrostatic interaction is present whenever tip and sample exhibit a different work function. For homogeneous samples, the work function difference can be compensated by applying an appropriate bias voltage and, hence, an unambiguous magnetic image can be obtained [33]. Sometimes, this

• electron beam impinges on the substrate may not have enough energy to overcome the work function of the surface and penetrate the bulk and as a consequence they will become trapped in the neighboring area of the wires. During the FEBID deposition process some secondary electrons reach the substrate surface

Influence of water on the properties of an Au/Mpy/Pd metal/molecule/metal junction

• Jan Kučera and
• Axel Groß

Beilstein J. Nanotechnol. 2011, 2, 384–393, doi:10.3762/bjnano.2.44

• weak metal–water interaction the electronic structure of the metal substrate remains almost unaffected upon the water adsorption [26]. On the other hand, the adsorbed water bilayers become strongly polarized which leads to a significant work function change upon water adsorption on more strongly

Simple theoretical analysis of the photoemission from quantum confined effective mass superlattices of optoelectronic materials

• Debashis De,
• Sitangshu Bhattacharya,
• S. M. Adhikari,
• A. Kumar,
• P. K. Bose and
• K. P. Ghatak

Beilstein J. Nanotechnol. 2011, 2, 339–362, doi:10.3762/bjnano.2.40

• photo-current density is [19] where e, m*, gv, kb, T, h, hν, are the electron charge, effective electron mass at the edge of the conduction band, valley degeneracy, the Boltzmann constant, temperature, the Planck constant, incident photon energy along the z-axis and work function respectively. It may

• be noted that the said equation is valid for both charge carriers and in this conventional form the photoemission changes with temperature, work function and the incident photon energy. This relation holds only under the condition of carrier non-degeneracy [20]. The following section gives the

The role of the cantilever in Kelvin probe force microscopy measurements

• George Elias,
• Thilo Glatzel,
• Ernst Meyer,
• Alex Schwarzman,
• Amir Boag and
• Yossi Rosenwaks

Beilstein J. Nanotechnol. 2011, 2, 252–260, doi:10.3762/bjnano.2.29

• displacement. We define a diagonal matrix Z whose diagonal elements are equal to the relative displacement for each cantilever element and equal to 1 for each tip element. The overall virtual work function may then be written as By nullifying the above expression we may achieve the new PSF of the system

Single-pass Kelvin force microscopy and dC/dZ measurements in the intermittent contact: applications to polymer materials

• Sergei Magonov and
• John Alexander

Beilstein J. Nanotechnol. 2011, 2, 15–27, doi:10.3762/bjnano.2.2

• verification of KFM operations. The same is true for metal alloys because their surface potentials are directly defined by work function [8]. At the beginning we compare KFM imaging in the non-contact and intermittent contact modes. When the AFM probe, which is driven into an oscillation at its resonant

• related to the strength and orientation of the molecular dipole, as is the case in fluoroalkanes self-assemblies. In other materials surface potential correlates to the surface work function of metals, the doping level of semiconductors, the strength and orientation of molecular dipoles, and the presence

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

• force microscopy; scanning tunneling microscopy; thin films; work function; Review Introduction The chemical properties of many crystal surfaces, especially oxides, are significantly influenced by defects in the perfectly ordered structure [1][2][3][4][5]. These defects can be impurities in the surface

• material with the lower work function (here tip) flow to the material with the higher work function. The Fermi levels align and an electrical field is built up [21]. The contact potential ΔΦ is then given by the difference in work function of the tip and of the sample surface, which may contain the studied

• single point defects or single adsorbates, instead of integrating over a square millimeter range. However, absolute values of the work function cannot be measured directly, only work function differences. Point defects Oxygen vacancies, also known as color centers, are electron trapping point defects and