Graphene quantum interference photodetector

• Mahbub Alam and
• Paul L. Voss

Beilstein J. Nanotechnol. 2015, 6, 726–735, doi:10.3762/bjnano.6.74

• % for the device. The results of the interaction of light with the zigzag and armchair structures are shown in Figure 5 and Figure 6, respectively. For this simulation, the parameters used for the zigzag structure were an applied voltage of 0.1 eV, photon energy of 0.26 eV and a photon flux of 1025

• photon/m2/s (4.16 × 106 W/m2). The parameters used for armchair structure were an applied voltage of 0.1 eV, photon energy of 0.13 eV and a photon flux of 1025 photon/m2/s (2.08 × 106 W/m2). For both the zigzag and armchair structures, the polarization of the applied electromagnetic field was along the

• variation of light. With the appropriate bias, the device can also be used to detect the photon energy corresponding to the energy difference of any two resonant levels. The peak photocurrent variations with different photon energies are shown in Figure 8a and Figure 8b corresponding to zigzag and armchair

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

• determined by direct transition, or for n = 2 if the transition is indirect [18][19]. As the TiO2 band gap is determined by direct transition, the plot of [f(R)·hν]1/2 versus hν shows a linear region which satisfies the equation where hν is the photon energy, Eg is the band gap energy, and K a characteristic

Overview of nanoscale NEXAFS performed with soft X-ray microscopes

• Peter Guttmann and
• Carla Bittencourt

Beilstein J. Nanotechnol. 2015, 6, 595–604, doi:10.3762/bjnano.6.61

• (i.e., up to 10 µm) specimens in materials and biological sciences using photon energies that covers the K- and L-X-ray absorption edges of elements of major interest [2][3][4][5]. High-photon energy X-ray diffraction used in operando studies can correlate changes in size of the unit cell of catalysts

• normally detect the photons which are transmitted through the sample. The penetration depth of X-rays and therefore the usable sample thickness correlates with the X-ray photon energy used for the analysis and is much larger than for electrons (Figure 2) [30]. In the soft X-ray regime penetration depths in

• the spatial resolution of the TXM, but still provide signals which can be used for NEXAFS spectroscopy. Spectroscopic studies at the carbon K-edge are very challenging because nearly in all beamlines the photon flux is sharply reduced within the carbon K-edge photon energy range (280 up to 320 eV) due

Structural, optical, opto-thermal and thermal properties of ZnS–PVA nanofluids synthesized through a radiolytic approach

• Alireza Kharazmi,
• Nastaran Faraji,
• Roslina Mat Hussin,
• Elias Saion,
• W. Mahmood Mat Yunus and
• Kasra Behzad

Beilstein J. Nanotechnol. 2015, 6, 529–536, doi:10.3762/bjnano.6.55

• concentration in agreement with the FTIR results. The optical band gap energy of the ZnS NPs was estimated through the Tauc equation as follows [6]: where α is the absorption coefficient, hν is the photon energy of the incident light, Eg is the band gap energy, B is a constant and n depends on the type of

Influence of size, shape and core–shell interface on surface plasmon resonance in Ag and Ag@MgO nanoparticle films deposited on Si/SiO_x

• Sergio D’Addato,
• Daniele Pinotti,
• Maria Chiara Spadaro,
• Guido Paolicelli,
• Vincenzo Grillo,
• Sergio Valeri,
• Luca Pasquali,
• Luca Bergamini and
• Stefano Corni

Beilstein J. Nanotechnol. 2015, 6, 404–413, doi:10.3762/bjnano.6.40

• radiation of s- and p-polarisation, together with classical electrodynamics simulations. For s-polarised incident radiation, it can be readily observed that SDR data from bare NPs do not reveal any significant features in the photon energy region between 2 and 4 eV (Figure 3b). In the case of MgO-covered

• . When co-deposited with Mg in O atmosphere, SEM images showed grains, which were assigned to formation of MgO shells around the original Ag NPs. SDR spectra taken under p-polarisation excitation exhibited a plasmon feature (with a deep minimum) at a photon energy between 3 and 3.5 eV where the intensity

Optical properties and electrical transport of thin films of terbium(III) bis(phthalocyanine) on cobalt

• Peter Robaschik,
• Pablo F. Siles,
• Daniel Bülz,
• Peter Richter,
• Manuel Monecke,
• Michael Fronk,
• Svetlana Klyatskaya,
• Daniel Grimm,
• Oliver G. Schmidt,
• Mario Ruben,
• Dietrich R. T. Zahn and
• Georgeta Salvan

Beilstein J. Nanotechnol. 2014, 5, 2070–2078, doi:10.3762/bjnano.5.215

• , respectively. For the dielectric constant we consider a minimum value of ε = 4.5, which is the real part of the dielectric function at the lowest photon energy (1.3 eV) used in our ellipsometry experiment (see Figure 2). As a maximum value for the dielectric constant we used ε = 13, which was previously

Cathode lens spectromicroscopy: methodology and applications

• T. O. Menteş,
• G. Zamborlini,
• A. Sala and
• A. Locatelli

Beilstein J. Nanotechnol. 2014, 5, 1873–1886, doi:10.3762/bjnano.5.198

• simplified sketch of an XPEEM setup is given in Figure 1a. Similar to LEEM, it is based on the cathode lens, which accelerates the photoelectrons to an energy of several keV and directs them towards the imaging column of the instrument. The low photon energy of the conventional photon sources readily

• secondary photoelectrons are collected in XPEEM as a close approximation to the total photoelectron yield measurement. The local XAS spectra are obtained by acquiring image sequences as a function of the photon energy, which can then be processed in order to extract the intensity variation within any region

• function. When the photon energy is tuned to the Fe absorption threshold (middle panel), the elongated Fe nanowires become much brighter, whereas the regions in between barely change intensity. The spectrum seen in the plot in Figure 3a is extracted from an individual nanowire. Magnetic imaging. X-ray

An insight into the mechanism of charge-transfer of hybrid polymer:ternary/quaternary chalcopyrite colloidal nanocrystals

• Parul Chawla,
• Son Singh and
• Shailesh Narain Sharma

Beilstein J. Nanotechnol. 2014, 5, 1235–1244, doi:10.3762/bjnano.5.137

• in Figure 3C(a–c), which shows the enhancement of the optical bandgap (as calculated from the Tauc’s plot involving the absorption coefficient, α and the photon energy hν) from CISe to CZTSe. The bandgap values of pristine CISe, CIGSe and CZTSe are ≈1.03 eV, 1.1 eV and 1.15 eV, respectively (Figure

Electron-beam induced deposition and autocatalytic decomposition of Co(CO)₃NO

• Florian Vollnhals,
• Martin Drost,
• Fan Tu,
• Esther Carrasco,
• Andreas Späth,
• Rainer H. Fink,
• Hans-Peter Steinrück and
• Hubertus Marbach

Beilstein J. Nanotechnol. 2014, 5, 1175–1185, doi:10.3762/bjnano.5.129

• Si3N4 membrane. In transmission X-ray microscopy or NEXAFS spectroscopy in transmission mode, the absorbance (or optical density, OD) is derived from: with I0 and I being the incident and the transmitted intensities, respectively, d represents the sample thickness and µ(E) the photon energy dependent

• interferometric control through the focal spot, while the transmitted photon intensity is recorded by using a photo multiplier tube. Near-edge X-ray absorption fine structure (NEXAFS) spectra were recorded by consecutive scanning of the investigated area with varying photon energy. The lateral resolution in

• deposits at an enlarged photon energy scale, along with the spectrum of a Co layer produced by PVD as reference (grey). Evaluation of the X-ray absorption data for the growth of Co-containing deposits by EBID plus autocatalytic growth upon Co(CO)3NO dosage. a) Optical density (left vertical axis) and

Characterization and photocatalytic study of tantalum oxide nanoparticles prepared by the hydrolysis of tantalum oxo-ethoxide Ta₈(μ₃-O)₂(μ-O)₈(μ-OEt)₆(OEt)₁₄

• Subia Ambreen,
• N D Pandey,
• Peter Mayer and
• Ashutosh Pandey

Beilstein J. Nanotechnol. 2014, 5, 1082–1090, doi:10.3762/bjnano.5.121

• absorption coefficient F(R′) values according to the Kubelka–Munk remission function [24][25][26] (Equation 5), where α is the absorption coefficient (cm−1) and S is the dispersion factor. The absorption coefficient α is related to the incident photon energy by Equation 6: A is a constant for the given

• material, E is the photon energy, Eg is the band gap energy and n is a constant of different values, 1/2, 3/2, 2 and 3, depending on the type of electronic transition, i.e., permitted/prohibited-direct or indirect transition. The band gap is calculated from a Tauc plot [27][28][29][30]. The band gap of the

Effects of the preparation method on the structure and the visible-light photocatalytic activity of Ag₂CrO₄

• Difa Xu,
• Shaowen Cao,
• Jinfeng Zhang,
• Bei Cheng and
• Jiaguo Yu

Beilstein J. Nanotechnol. 2014, 5, 658–666, doi:10.3762/bjnano.5.77

• particle size among the three samples. The indirect band gaps of the Ag2CrO4 samples are calculated according to the Kubelka–Munk (KM) method by the following equation [62]: where α is the absorption coefficient, hν is the photon energy, Eg is the indirect band gap, and A is a constant. As shown in the

Interaction of iron phthalocyanine with the graphene/Ni(111) system

• Lorenzo Massimi,
• Simone Lisi,
• Daniela Pacilè,
• Carlo Mariani and
• Maria Grazia Betti

Beilstein J. Nanotechnol. 2014, 5, 308–312, doi:10.3762/bjnano.5.34

• energy in normal emission and by the quenching of the Gr–Ni π−d hybrid state at the K point of the BZ. Experimental ARPES band structure for graphene grown on Ni(111) (left) and on Ir(111) (right), taken with 40.814 eV photon energy along the ΓK direction of the 2D BZ. Insets: corresponding LEED patterns

• graphene (red lines) and of the FePc/Gr systems (black lines). Data taken with 40.814 eV photon energy (HeIIα) and around normal emission (±4° angular integration around the Γ point). The data was normalized to the intensity at the Fermi edge and vertically stacked for clarity. In the insets, a zoom around

• the Fermi level for a coverage of 0.3 and 1 SL of FePc is given. Valence band spectral density of states of clean Ni(111) (red line), of Gr/Ni(111) and of 0.2 SL FePc onto Gr/Ni (black lines), taken at the K point of the BZ (±2° angular integration around K, with 21.218 eV photon energy

Challenges in realizing ultraflat materials surfaces

• Takashi Yatsui,
• Wataru Nomura,
• Fabrice Stehlin,
• Olivier Soppera,
• Makoto Naruse and
• Motoichi Ohtsu

Beilstein J. Nanotechnol. 2013, 4, 875–885, doi:10.3762/bjnano.4.99

• DPPs induce the photodissociation of molecules at protrusions on the substrate (Figure 1b) even when the incident photon energy is smaller than the photodissociation energy, Ed. The dissociated molecules in turn induce the etching of the protrusion and the flattening the substrate (Figure 1c). This

• gas in the DPP etching, which produced the oxygen radicals O* to etch the protrusions of the diamond substrate and ultimately yielded an ultra-flat surface. Since the photon energy of the laser is lower than Ed of O2, the conventional O2 adiabatic photochemical reaction was avoided. Furthermore, the

• by the fact that the Ra value remained the same after 24 hours of etching. To verify that the smoothing effect originated from the DPP process, the surface roughness was compared by using AFM images taken after conventional photoetching, in which a photon energy higher than Ed was used and after DPP

Probing the plasmonic near-field by one- and two-photon excited surface enhanced Raman scattering

• Katrin Kneipp and
• Harald Kneipp

Beilstein J. Nanotechnol. 2013, 4, 834–842, doi:10.3762/bjnano.4.94

• near-field of silver nanoaggregates. The experiments reveal enhancement factors of local fields in the hottest hot spots of the near-field and their dependence on the photon energy. Also, the number of the hottest spots and their approximate geometrical size are found. Near-field amplitudes in the

• hottest spots can be enhanced by three orders of magnitudes. Nanoaggregates of 100 nm dimensions provide one hot spot on this highest enhancement level where the enhancement is confined within less than 1nm dimension. The near-field enhancement in the hottest spots increases with decreasing photon energy

• interesting question is the dependence of the near-field enhancement on the photon energy. The ratio between SEHRS and SERS signals measured vs the excitation wavelengths delivers direct information about this dependence. Figure 5 shows the result of experiments, in which a tunable ps Ti:sapphire was used for

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

• is the optical transmittance. The optical density D is related to the band gap Eg by proportion [35]: where hν is the photon energy, and Eg is the band gap. Graphically estimated band gap values of thin ZnO films are shown in Figure 3c. The obtained values are lower than the value typical of a ZnO

• the band edge is an exponential function of the photon energy as described by the Urbach law [37]: where E0 is the Urbach energy interpreted as the width of the tail of the states localized close to the conductance band in the forbidden zone. Numerical calculations show a decrease of the Urbach energy

Photocatalytic antibacterial performance of TiO₂ and Ag-doped TiO₂ against S. aureus. P. aeruginosa and E. coli

• Kiran Gupta,
• R. P. Singh,
• Ashutosh Pandey and
• Anjana Pandey

Beilstein J. Nanotechnol. 2013, 4, 345–351, doi:10.3762/bjnano.4.40

• case, for an indirect band gap, the value of n is ½ [17]. The variation of (αhν)1/2 with photon energy is shown in Figure 4. The band gaps were determined to be about 3.15 eV, 2.8 eV and 2.7 eV for annealed TiO2, Ag–TiO2 (3%) and Ag–TiO2 (7%), respectively, by extrapolation of the linear portion of the

• versus photon energy (eV) curve of (a) TiO2 and (b) 3% and (c) 7% Ag-doped TiO2 nanoparticles. Photoluminescence spectra of annealed TiO2 (a) and 3% and 7% Ag-doped TiO2 nanoparticles (b,c). Viability of bacteria (S. aureus) against the concentration of nanoparticles (mg/30 mL of culture) in %. Viability

Near-field effects and energy transfer in hybrid metal-oxide nanostructures

• Ulrich Herr,
• Barat Achinuq,
• Cahit Benel,
• Giorgos Papageorgiou,
• Manuel Goncalves,
• Johannes Boneberg,
• Paul Leiderer,
• Paul Ziemann,
• Peter Marek and
• Horst Hahn

Beilstein J. Nanotechnol. 2013, 4, 306–317, doi:10.3762/bjnano.4.34

• measured. Figure 3 shows a typical emission spectrum of a TiO2:Eu sample containing 0.8 wt % Eu under excitation at 330 or 390 nm. The characteristic Eu3+ emission lines with the dominating 5D0→7F2 transition at 617 nm can be clearly observed. For excitation with 330 nm, the photon energy (3.76 eV) is

Photoresponse from single upright-standing ZnO nanorods explored by photoconductive AFM

• Igor Beinik,
• Markus Kratzer,
• Astrid Wachauer,
• Lin Wang,
• Yuri P. Piryatinski,
• Gerhard Brauer,
• Xin Yi Chen,
• Yuk Fan Hsu,
• Aleksandra B. Djurišić and
• Christian Teichert

Beilstein J. Nanotechnol. 2013, 4, 208–217, doi:10.3762/bjnano.4.21

• ZnO NRs revealed that the minimum photon energy sufficient for photocurrent excitation is 3.1 eV. This value is at least 100 meV lower than the band-gap energy determined from the photoluminescence experiments. Conclusion: The obtained results suggest that the photoresponse in ZnO NRs under ambient

•  5b). The latter provides the energy corresponding to the transition involved in the photocarrier generation process. Interestingly, it has been found that the NRs are already sensitive to illumination with a wavelength of 400 nm, i.e., with a corresponding photon energy of 3.1 eV which is smaller

• by the dashed line in Figure 5b yields the transition energies involved in the photocarrier generation process. The obtained value Emin ≈ 3.1 eV is the minimum photon energy sufficient for the photoexcitation of mobile charge carriers. The value of 3.1 eV turned out to be at least 100 meV lower than

Towards atomic resolution in sodium titanate nanotubes using near-edge X-ray-absorption fine-structure spectromicroscopy combined with multichannel multiple-scattering calculations

• Carla Bittencourt,
• Peter Krüger,
• Maureen J. Lagos,
• Xiaoxing Ke,
• Gustaaf Van Tendeloo,
• Chris Ewels,
• Polona Umek and
• Peter Guttmann

Beilstein J. Nanotechnol. 2012, 3, 789–797, doi:10.3762/bjnano.3.88

• measurements. NEXAFS spectra at the Ti L-edge recorded on (1) SrTiO3, (2) (Na,H)TiNTs and (3) anatase. The vertical lines indicate the photon energy of the first four X-ray images in Figure 2. The inset shows the pre-edge structures in the nanotube spectrum. (b) Ti L-edge spectra of (1) SrTiO3, (2) (Na,H)TiNTs

Ultraviolet photodetection of flexible ZnO nanowire sheets in polydimethylsiloxane polymer

• Jinzhang Liu,
• Nunzio Motta and
• Soonil Lee

Beilstein J. Nanotechnol. 2012, 3, 353–359, doi:10.3762/bjnano.3.41

• photon energy higher than Eg generates electron–hole pairs in the ZnO. Holes migrate to the surface along the potential slope created by the band bending and recombine with O2-trapped electrons, thus releasing oxygen from the surface: O2–(ad) + h+ → O2(g). The heavily populated electrons in the

X-ray absorption spectroscopy by full-field X-ray microscopy of a thin graphite flake: Imaging and electronic structure via the carbon K-edge

• Carla Bittencourt,
• Adam P. Hitchock,
• Xiaoxing Ke,
• Gustaaf Van Tendeloo,
• Chris P. Ewels and
• Peter Guttmann

Beilstein J. Nanotechnol. 2012, 3, 345–350, doi:10.3762/bjnano.3.39

• ). During the data acquisition for a NEXAFS image stack, only the objective is moved, since the reflective condenser works largely independently of the photon energy of the illuminating X-rays. For the different photon energies there are slight changes in magnification, which are corrected by relocation of

• energy of this structure, indicating that the doping is rather uniform in the flake. In a recent theoretical study, spectral features appearing at 287–290 eV photon energy were associated with topological defects, such as monovacancies, divacancies and Stone–Wales defects [26]. In particular, a structure

• aXis2000 [27]. The NEXAFS spectra were normalized by using the signal intensity of the sample (the circled area in Figure 2) to correct for variations of the photon flux with photon energy (hν) and acquisition time. The sample was obtained from NanoIntegris (Illinois, USA) in the form of “PureSheets” (MONO

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

• ) and Cu3BiS3/In2S3 (b) samples. The x-signal begins at photon energies significantly below the optical band gap of Cu3BiS3. For Cu3BiS3 the in-phase PV signal is initially positive and increases to about 13 µV with increasing photon energy. Before a strong increase of the signal up to 114 µV at photon

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

• difference in attenuation of this signal in different films. Due to the quite close binding energies of the Au 4f and S 2p emissions, both signals are attenuated similarly, although not absolutely equally, as far as the primary excitation is performed at high photon energy. The S2p/Au4f intensity ratios for

• monitored by plotting the difference between the NEXAFS spectra acquired at normal (90°) and grazing (20°) angles of X-ray incidence. The C K-edge NEXAFS spectra of the NC-OPEn SAMs acquired at an X-ray incidence angle of 55° are presented in Figure 3a, whereas the π*-resonance photon-energy range of these

• higher photon energy. These spectra resemble that of benzonitrile [57][58] and are also typical of SAMs containing this moiety [29][30][33][59]. The appearance of the dominant double resonance is caused by the conjugation between the π* orbitals of the nitrile group and those of the adjacent phenyl ring

Investigation on structural, thermal, optical and sensing properties of meta-stable hexagonal MoO₃ nanocrystals of one dimensional structure

• Angamuthuraj Chithambararaj and
• Arumugam Chandra Bose

Beilstein J. Nanotechnol. 2011, 2, 585–592, doi:10.3762/bjnano.2.62

• band gap is evaluated using K–M function as follows [27]: where F(R∞) is the K–M function or re-emission function, R∞ is the diffuse reflectance of an infinitely thick sample, K(λ) is the absorption coefficient, s(λ) is the scattering coefficient, hν is the photon energy and Eg is the band gap energy

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

• recording the sample drain current (total electron yield, TEY) as a function of photon energy. External fields of up to µ0H = ± 3 T were available. Spectra and hysteresis loops were recorded and evaluated by methods described previously [11][28][29][30]. The insert to Figure 4a displays a typical pair of