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

• surface and bulk defect states. TiO2 is regarded as an insulator with a relative permittivity of εr = 36 and consequently acts as a charge storage capacitor between a metallic tip and a highly conductive SnO2:F contact. Upon photoelectric charge injection, the redistribution of charge carriers (by

• work function, ΔΦS, is related to the surface dipole through the Helmholtz equation: where (N/A) is the number of dipoles/molecules per surface area, ε = (P0/P) is the effective dielectric constant of a molecular monolayer and ε0 is the permittivity in vacuum. The dipole layer is oriented at an angle

Influence of diffusion on space-charge-limited current measurements in organic semiconductors

• Thomas Kirchartz

Beilstein J. Nanotechnol. 2013, 4, 180–188, doi:10.3762/bjnano.4.18

• density J would to a first approximation not depend on the equilibrium electron concentration anymore. Instead J would just depend on the mobility μ, which is typically the only unknown parameter, as well as the voltage V, the device thickness d and the permittivity ε = ε0εr and would ideally follow the

• Mott–Gurney law [18][19] Here ε0 is the vacuum permittivity and εr is the relative permittivity. The Mott–Gurney law is frequently used to determine the mobility of organic semiconductors used for light emitting diodes and solar cells. However, its derivation uses three assumptions that are often not

• simulations except for the one with Vbi = 1 V in Figure 2, where the contact barrier at the cathode (x = d) is 0.1 eV and the contact barrier at the anode (x = 0) is 1.1 eV. The relative permittivity used in all simulations is εr = 3.8 and the capture coefficient for the Gaussian defect is 10−10 cm3·s−1 for

Plasmonics-based detection of H₂ and CO: discrimination between reducing gases facilitated by material control

• Gnanaprakash Dharmalingam,
• Nicholas A. Joy,
• Benjamin Grisafe and
• Michael A. Carpenter

Beilstein J. Nanotechnol. 2012, 3, 712–721, doi:10.3762/bjnano.3.81

• inducing a blue shift or increase in LSPR frequency, ω, as characterized by the Drude model in Equation 1. In the above equation N0 is the free-electron density of the Au particle, e the electron charge, εm the dielectric constant of the matrix and ε0 the permittivity of vacuum [24]. These reactions will

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

• distance. When both the tip and the sample are conductive and there is an electrostatic potential difference (U) between them, the electrostatic force [27][28] is where R is the radius of the metallic part of the spherical tip, ε0 is the permittivity of free space and z is the effective tip–sample distance

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

• magnitude of electronic charge, mr is the reduced mass and is given by mr−1 = (m*)−1 + mv−1, mv is the effective mass of the heavy hole at the top of the valance band in the absence of any field, I0 is the light intensity of wavelength λ, ε0 is the permittivity of vacuum, εsc is the permittivity of the

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

• permittivity (ε of TiO2 = 85.8 and 170, anisotropic), ε0 the vacuum permittivity (8.854 × 10−12 F·m−1), q the elementary electric charge (1.602 × 10−19 C), N the carrier density [m−3], E the applied potential [V], Efb the flat band potential [V], kB the Boltzman constant (1.380 × 10−23 J·K−1), and T the

• Equation 2, the flat band potential Efb, carrier density N, and the thickness of space charge layer dsc were calculated and are shown in Table 1. For the calculation, since the relative permittivity ε of TiO2 is anisotropic (85.8 and 170), we used both the values in the calculation, and thereafter took

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

• enable measurements of electrical properties (surface potential, dielectric permittivity, capacitance, etc.) at a tip–sample junction. Here we will demonstrate that single-pass Kelvin force microscopy (KFM) studies based on sensing of an electrostatic force gradient can be performed in the intermittent

• to dC/dZ. Both the dC/dZ and d2C/dZ2 signals are related to the local dielectric permittivity and we used these for compositional mapping. The interplay between the experimental measurements and theoretical studies is needed for a better understanding of the sensitivity of dC/dZ and d2C/dZ2 based

• dielectric studies, and for the extraction of quantitative permittivity data. In addition, we also recorded the phase response at 2ωelec that can be used for detection of complex dielectric response. In the following we will demonstrate that surface potential and dC/dZ data, which are measured simultaneously

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

• friction forces. The forces relevant in this work are described below. Coulomb forces are a result of interacting charges and can be stronger than most chemical binding forces [9]. The Coulomb potential ECoulomb between two charges Q1 and Q2 is given by where ε0 is the permittivity constant, ζ is the

• relative permittivity or dielectric constant of the medium and z the distance between the charges. The Coulomb force FCoulomb is given by It is well known [12] that for very small amplitudes, the shift of the resonance frequency Δf corresponds to the derivative of the tip-sample forces with respect to z