Apparent tunneling barrier height and local work function of atomic arrays

• Neda Noei,
• Alexander Weismann and
• Richard Berndt

Beilstein J. Nanotechnol. 2018, 9, 3048–3052, doi:10.3762/bjnano.9.283

• have been used to estimate variations of the local work function Φ of surface structures. We experimentally show that Φapp can fail as a measure of Φ. The discrepancies are attributed to a kinetic-energy contribution to Φapp. This contribution depends on the lateral extent of the tunneling current

• filament and, consequently, on the local surface structure. Keywords: scanning tunneling microscopy; tunneling barrier height; work function; Findings The work function of a metal surface [1], the work required at temperature T = 0 K to move an electron from the metal to infinity, is relevant for, e.g

• . This is reflected by the notion of a local work function Φ [7][8][9]. Adsorbates modify Φ in an intriguing manner [10][11][12][13]. In turn, variations of Φ produce, e.g., atomic-scale contrast in field-emission microscopy, photo-emission electron microscopy, and low-energy electron microscopy [14][15

In situ characterization of nanoscale contaminations adsorbed in air using atomic force microscopy

• Jesús S. Lacasa,
• Lisa Almonte and
• Jaime Colchero

Beilstein J. Nanotechnol. 2018, 9, 2925–2935, doi:10.3762/bjnano.9.271

• the islands. Since the contact potential image is very sensitive to differences in work function and since it seems unlikely that platinum has the same work function as the (unknown) material of the island, we think that the most logical explanation for the homogeneous contact potential image is that

Charged particle single nanometre manufacturing

• Philip D. Prewett,
• Cornelis W. Hagen,
• Claudia Lenk,
• Steve Lenk,
• Marcus Kaestner,
• Tzvetan Ivanov,
• Ahmad Ahmad,
• Ivo W. Rangelow,
• Xiaoqing Shi,
• Stuart A. Boden,
• Alex P. G. Robinson,
• Dongxu Yang,
• Sangeetha Hari,
• Marijke Scotuzzi and
• Ejaz Huq

Beilstein J. Nanotechnol. 2018, 9, 2855–2882, doi:10.3762/bjnano.9.266

• and Lothar Nordheim [131]. This process is governed by Equation 4: The equation describes the dependence of the emitted current density J on the electric field E and the work function of the tip material. A, B and C are constants, which are given, e.g., in [132]. Since the electric field strongly

Graphene-enhanced metal oxide gas sensors at room temperature: a review

• Dongjin Sun,
• Yifan Luo,
• Marc Debliquy and
• Chao Zhang

Beilstein J. Nanotechnol. 2018, 9, 2832–2844, doi:10.3762/bjnano.9.264

• of the p–n heterojunction is shown in Figure 1, Ec and Ev are the energies of conduction band and valence band of the two components, respectively, while the Fermi level energy (Ef) is between these two bands. It can be seen from Figure 1 that the work function of rGO is lower than that of SnO2

• -type CuO and rGO contributed to the extraordinary sensing performance. The work function of CuO (4.1–4.3 eV) and rGO (5.0–5.1 eV) are not equal [48][49], hence Eg1 (1.2 eV) is not equal to Eg2 (0.4 eV) [50][51]. The electrons will transfer from CuO to rGO until the Fermi energy level of the two

• work function of SnO2 (4.55 eV) is lower than that of rGO (4.75 eV). As a result, electrons transfer from SnO2 to the conduction band of rGO, not only leading to the bending of the energy bands but also forming potential barriers at the interfaces between SnO2 and rGO. When exposed to air at room

Optimization of Mo/Cr bilayer back contacts for thin-film solar cells

• Nima Khoshsirat,
• Fawad Ali,
• Vincent Tiing Tiong,
• Mojtaba Amjadipour,
• Hongxia Wang,
• Mahnaz Shafiei and
• Nunzio Motta

Beilstein J. Nanotechnol. 2018, 9, 2700–2707, doi:10.3762/bjnano.9.252

• , the back contact material should have a higher work function than the neighboring light-absorbing semiconductor layer [3]. Accordingly, different metal contacts (such as Al, Au, Cr, Mn, Mo, Pt, Ti, V and W) have been used as back contact layer in thin-film solar cells [4][5][6][7]. Among these

• elements, Mo is reported to have a relatively better stability at the elevated temperatures required for the fabrication of CIGS and CZTS, better ohmic contact behavior, lower resistivity and a higher work function than the CIGS and CZTS light-absorbing semiconductor layers. However, the most challenging

Enhancement of X-ray emission from nanocolloidal gold suspensions under double-pulse excitation

• Wei-Hung Hsu,
• Frances Camille P. Masim,
• Armandas Balčytis,
• Hsin-Hui Huang,
• Tetsu Yonezawa,
• Aleksandr A. Kuchmizhak,
• Saulius Juodkazis and
• Koji Hatanaka

Beilstein J. Nanotechnol. 2018, 9, 2609–2617, doi:10.3762/bjnano.9.242

• electron work function (escape energy) need to be accounted for through (εb + εesc) together with the substitution A/ls = 4π/λ. For the ionization threshold, the electron work function is considered. Then, the ionization threshold reads [37]: For gold the following values are valid: εesc = 5.1 eV and

Intrinsic ultrasmall nanoscale silicon turns n-/p-type with SiO₂/Si₃N₄-coating

• Dirk König,
• Daniel Hiller,
• Noël Wilck,
• Birger Berghoff,
• Merlin Müller,
• Sangeeta Thakur,
• Giovanni Di Santo,
• Luca Petaccia,
• Joachim Mayer,
• Sean Smith and
• Joachim Knoch

Beilstein J. Nanotechnol. 2018, 9, 2255–2264, doi:10.3762/bjnano.9.210

• realized using a tantalum (Ta) stripe in electrical contact to the sample as a work function reference. Further UPS-data of SiO2 and Si3N4 reference samples as well as UPS signal normalization are available in Supporting Information File 1. All samples for TEM investigation were capped with a protective

A scanning probe microscopy study of nanostructured TiO₂/poly(3-hexylthiophene) hybrid heterojunctions for photovoltaic applications

• Laurie Letertre,
• Roland Roche,
• Olivier Douhéret,
• Hailu G. Kassa,
• Denis Mariolle,
• Nicolas Chevalier,
• Łukasz Borowik,
• Philippe Dumas,
• Benjamin Grévin,
• Roberto Lazzaroni and
• Philippe Leclère

Beilstein J. Nanotechnol. 2018, 9, 2087–2096, doi:10.3762/bjnano.9.197

• work function (around 4.7 eV in literature [6][15]) compared to that of TiO2 (around 4.3 eV in literature [7]). The data of Figure 3 were compared with the images obtained on bare nanocolumnar TiO2 (Figure 2). In both measurements, the ITO electrode was grounded and the same tip was used. The

Electromigrated electrical optical antennas for transducing electrons and photons at the nanoscale

• Arindam Dasgupta,
• Mickaël Buret,
• Nicolas Cazier,
• Marie-Maxime Mennemanteuil,
• Reinaldo Chacon,
• Kamal Hammani,
• Jean-Claude Weeber,
• Juan Arocas,
• Laurent Markey,
• Gérard Colas des Francs,
• Alexander Uskov,
• Igor Smetanin and
• Alexandre Bouhelier

Beilstein J. Nanotechnol. 2018, 9, 1964–1976, doi:10.3762/bjnano.9.187

• barrier height. Considering that the work function of gold is ca. 5.4 eV, Equation 1 is usually valid for applied bias voltages up to a few volts. The shape of the tunneling characteristics of IT(Vdc) essentially depends on the parameters d and with minor corrections from the effective area A [41]. These

• work function of gold. The Fowler–Nordheim plot, as a function of 1/Vdc, is commonly used to distinguish the transition between direct tunneling at low Vdc and a high-bias regime where the energy barrier is drastically reduced and electrons are tunneling by field emission [44]. Thus, the

The role of the Ge mole fraction in improving the performance of a nanoscale junctionless tunneling FET: concept and scaling capability

• Hichem Ferhati,
• Fayçal Djeffal and
• Toufik Bentrcia

Beilstein J. Nanotechnol. 2018, 9, 1856–1862, doi:10.3762/bjnano.9.177

• tunneling effect, while materials with high work function are required to generate the tunnel current. In other words, the channel is assumed to be a uniformly and highly doped n-type material, and in order to ensure the band-to-band tunneling effect, the source is supported with a control gate to make the

• ensure a good electrostatic control of the channel, with tox representing its thickness. Moreover, the material of the gated source is assumed to have a high work function value of 5.6 eV in order to guarantee the tunnel effect, while the work function of the channel gate is set equal to 4.3 eV. In

Know your full potential: Quantitative Kelvin probe force microscopy on nanoscale electrical devices

• Amelie Axt,
• Ilka M. Hermes,
• Victor W. Bergmann,
• Niklas Tausendpfund and
• Stefan A. L. Weber

Beilstein J. Nanotechnol. 2018, 9, 1809–1819, doi:10.3762/bjnano.9.172

• , most studies comparing AM- to FM-KPFM methods have used samples exhibiting a work function contrast [23][24][27]. For example, Zerweck et al. have observed a superior spatial and quantitative resolution of FM-KPFM as compared to AM-KPFM on a gold and potassium chloride interface in ultra-high vacuum

• cantilevers was ≈225 μm, the width ≈35 μm. Tip, tip cone and cantilever are coated with PtIr (work function 5.5 eV [39]) on both sides. The topography feedback was performed with amplitude modulation (AM) on the first eigenmode and the oscillation amplitude was kept to approximately 40 nm for all methods. To

• width of the electrodes is 2 μm and the length 2 mm. The electrode array consists of 65 pairs of electrodes. According to ALS-Japan the electrodes are made of pure platinum with a work function of 5.7 eV [41]. The electrodes are embedded into the glass substrate and therefore offer a low resistance

Direct AFM-based nanoscale mapping and tomography of open-circuit voltages for photovoltaics

• Katherine Atamanuk,
• Justin Luria and
• Bryan D. Huey

Beilstein J. Nanotechnol. 2018, 9, 1802–1808, doi:10.3762/bjnano.9.171

• , local photovoltaic (PV) properties such as the open-circuit voltage, photocurrent, and work function have been demonstrated to vary by an order of magnitude, or more, within tens of nanometers [1][2][3]. Recently, property mapping with high spatial resolution by AFM has been further combined with the

• measured properties, for example with work function differences of molecular perovskites observed at specific facets [24] or grain boundary interfaces [2]. Topography commonly couples with conductive or photoconductive AFM contrast as well. Routines to test for such associations are therefore increasingly

Multimodal noncontact atomic force microscopy and Kelvin probe force microscopy investigations of organolead tribromide perovskite single crystals

• Yann Almadori,
• David Moerman,
• Jaume Llacer Martinez,
• Philippe Leclère and
• Benjamin Grévin

Beilstein J. Nanotechnol. 2018, 9, 1695–1704, doi:10.3762/bjnano.9.161

• = Wtip − Wsample, where W is the work function divided by the elementary charge in absolute value) is thus the opposite of VDC (more details about these polarity conventions can be found in [19]). In the following, the KPFM data are presented as compensation bias (Vtip = −CPD) images (also called the

Toward the use of CVD-grown MoS₂ nanosheets as field-emission source

• Geetanjali Deokar,
• Nitul S. Rajput,
• Junjie Li,
• Francis Leonard Deepak,
• Wei Ou-Yang,
• Nicolas Reckinger,
• Carla Bittencourt,
• Jean-Francois Colomer and
• Mustapha Jouiad

Beilstein J. Nanotechnol. 2018, 9, 1686–1694, doi:10.3762/bjnano.9.160

• and low-cost production technology with high quality and large quantities. An ideal FE material would have a low work function, aligned arrays of sharp tips, large aspect ratio, high stability and moderate current density, as well as the capability to be placed easily on a conductive substrate [1

• factor) is a particular value of the principal Schottky–Nordheim barrier function U. β is the local electrical field enhancement factor. is the work function of the emitter (considered to be 4.04 eV here [29]). In Figure 6a, the current density versus electric field (J–E) curve of the transferred MoS2

Robust topological phase in proximitized core–shell nanowires coupled to multiple superconductors

• Tudor D. Stanescu,
• Anna Sitek and
• Andrei Manolescu

Beilstein J. Nanotechnol. 2018, 9, 1512–1526, doi:10.3762/bjnano.9.142

• shell, and the presence of the carrier density in the shell. In addition, for Majorana devices, one should incorporate the effects due to the presence of a parent superconductor, including the work function difference between the superconductor and the semiconductor, as well as the effects generated by

Cr(VI) remediation from aqueous environment through modified-TiO₂-mediated photocatalytic reduction

• Rashmi Acharya,
• Brundabana Naik and
• Kulamani Parida

Beilstein J. Nanotechnol. 2018, 9, 1448–1470, doi:10.3762/bjnano.9.137

• from the semiconductor to graphene only when the work function of graphene is greater than the conduction band energy of the semiconductor. Since the work function of graphene (≈4.42 eV) [120][121] is greater than the conduction band potential of TiO2 (−4.21 V vs vacuum) [122][123][124], photogenerated

Artifacts in time-resolved Kelvin probe force microscopy

• Sascha Sadewasser,
• Nicoleta Nicoara and
• Santiago D. Solares

Beilstein J. Nanotechnol. 2018, 9, 1272–1281, doi:10.3762/bjnano.9.119

• nanometer scale [2]. The imaging mechanism relies on the compensation of electrostatic forces by application of a bias voltage that corresponds to the local contact potential difference (CPD), the relative difference between the work function of the tip and that of the sample area below the tip. In most

• the Fermi level, affecting the work function, which is defined as the energy difference between the local vacuum level and the Fermi level [12]. Usually, KPFM is used as a slow technique aiming at imaging local variations in the CPD. The KPFM feedback circuit applies a dc voltage to the tip (or the

• applications, spatial variations of the CPD are imaged in a static fashion, where variations in the CPD images can have different origins. (i) Variations in the local surface structure, chemistry, or material can affect the CPD by means of a change in the surface dipole, the electron affinity, or the work

Electro-optical interfacial effects on a graphene/π-conjugated organic semiconductor hybrid system

• Karolline A. S. Araujo,
• Luiz A. Cury,
• Matheus J. S. Matos,
• Thales F. D. Fernandes,
• Luiz G. Cançado and
• Bernardo R. A. Neves

Beilstein J. Nanotechnol. 2018, 9, 963–974, doi:10.3762/bjnano.9.90

• of graphene-based devices, SAM surface functionalization is employed for both doping level control and work function tuning [14][15][16]. The present work brings these two fronts together by investigating a graphene/retinoic acid (RA) – a π-conjugated organic semiconductor – hybrid system and its

• surface), G (green color), Gf and RA (brown – dark and blue – illuminated). It is clear in Figure 4f that, upon RA functionalization, the surface potential of a graphite microplate decreases. This provides a signature of p-type doping of graphene, as follows: the work function φ of any material is given

• an increase on its work function φ [35][36]. Since the tip–sample surface potential Φ is given by eΦ = φTip – φS, where φTip(φS) is the tip (sample) work function and e the elementary charge [37], a p-type doping in graphene (sample) increases its work function, hence decreasing the observed surface

Synthesis and characterization of two new TiO₂-containing benzothiazole-based imine composites for organic device applications

• Anna Różycka,
• Agnieszka Iwan,
• Krzysztof Artur Bogdanowicz,
• Michal Filapek,
• Natalia Górska,
• Damian Pociecha,
• Marek Malinowski,
• Patryk Fryń,
• Agnieszka Hreniak,
• Jakub Rysz,
• Paweł Dąbczyński and
• Monika Marzec

Beilstein J. Nanotechnol. 2018, 9, 721–739, doi:10.3762/bjnano.9.67

• investigated devices, together with energy level diagram of donor and acceptors based on the CV experiments, as well as the work function of both electrodes, are presented in Figure 15. It turned out that all investigated devices based on SP1 imine, independent of the active layer composition, exhibited very

• energy level diagram of donor and acceptors based on CV experiments and the work function of the different electrodes. I–V curves of the ITO/TiO2/active layer/Au systems under 88 mW/cm2 illumination: I–IV characteristics. Synthetic route and chemical structure of SP1 and SP2 imines. Electrochemical and

Mechanistic insights into plasmonic photocatalysts in utilizing visible light

• Kah Hon Leong,
• Azrina Abd Aziz,
• Lan Ching Sim,
• Pichiah Saravanan,
• Min Jang and
• Detlef Bahnemann

Beilstein J. Nanotechnol. 2018, 9, 628–648, doi:10.3762/bjnano.9.59

• hot-electron density on the surface of Ag and Au NPs escalated the Fermi energy level of Ag and Au, enabling the electrons to be easily injected to the conduction band of AgBr. Simultaneously, the difference in work function between the bimetallic and AgBr formed a Schottky junction to facilitate the

• parameters of plasmonic metal nanostructures such as particle size, work function, surface facet and plasmonic band is a challenging task that demands numerical simulation. It is known that the photocatalysis performance is affected by the noble metal particle size and thus finite difference time domain

Anchoring of a dye precursor on NiO(001) studied by non-contact atomic force microscopy

• Sara Freund,
• Antoine Hinaut,
• Nathalie Marinakis,
• Edwin C. Constable,
• Ernst Meyer,
• Catherine E. Housecroft and
• Thilo Glatzel

Beilstein J. Nanotechnol. 2018, 9, 242–249, doi:10.3762/bjnano.9.26

• recorded by Kelvin probe force microscopy (KPFM) [68]. The CPD arises from the work function difference between the tip and the substrate and is altered by surface charges or dipoles. The voltage needed to compensate for the electrostatic forces due to this potential difference is measured in KPFM. The CPD

• , compared to bare NiO, the CPD is increased when molecules are adsorbed in assemblies and consequently, the sample work function also increased. This can directly be related to a more negatively charged molecular layer compared to the substrate and a dipole moment is pointing towards the surface. The

Combined scanning probe electronic and thermal characterization of an indium arsenide nanowire

• Tino Wagner,
• Fabian Menges,
• Heike Riel,
• Bernd Gotsmann and
• Andreas Stemmer

Beilstein J. Nanotechnol. 2018, 9, 129–136, doi:10.3762/bjnano.9.15

• each position x, Ulcpd(x, I) can be separated into an offset value and the potential U(x, I) induced by the applied current I. contains information on the effect of charges trapped in a capping oxide surrounding the nanowire, and the differences in work function of the heterogeneous device and the

Amplified cross-linking efficiency of self-assembled monolayers through targeted dissociative electron attachment for the production of carbon nanomembranes

• Sascha Koch,
• Christopher D. Kaiser,
• Paul Penner,
• Michael Barclay,
• Lena Frommeyer,
• Daniel Emmrich,
• Patrick Stohmann,
• Tarek Abu-Husein,
• Andreas Terfort,
• D. Howard Fairbrother,
• Oddur Ingólfsson and
• Armin Gölzhäuser

Beilstein J. Nanotechnol. 2017, 8, 2562–2571, doi:10.3762/bjnano.8.256

• forming SAMs and is also likely to affect the cross-linking efficiency [40]. Secondly, when a SAM is formed on a metallic surface, such as Au(111) for example, the work function of the substrate is changed, leading to an increase or a decrease of the secondary electron emission. In the same manner, self

• -assembled monolayers from different terminated molecules can lead to an unequal change of the surface work function [41] as well as the emission of secondary electrons. However, the specific role of the halogen substituent within the cross-linking process cannot be extracted from our experimental data and

Adsorption of iron tetraphenylporphyrin on (111) surfaces of coinage metals: a density functional theory study

• Hao Tang,
• Nathalie Tarrat,
• Véronique Langlais and
• Yongfeng Wang

Beilstein J. Nanotechnol. 2017, 8, 2484–2491, doi:10.3762/bjnano.8.248

• . At the end, the relationship between the substrate and the coordination sphere of Fe is discussed in terms of molecule–surface interaction, charge transfer and work function modification. Results and Discussion Free molecule and conformations The ideal D4h symmetry, exhibiting the phenyl rings

• adsorbed FeTPP in the deckchair conformation (C2h). In the following we check the strength of different interactions involved in the adsorption of this HS FeTPP on the Au(111) surface as well as the charge transfer, work function modification and the projected density of states (PDOS) variations. In the

• to the Au(111) surface does not disturb the distribution of d-orbitals around the Fermi level. The work function Φ = Epot − EFermi on uncovered Au(111) was calculated with Epot being the local potential at the middle of vacuum of the simulation cell. The evaluated value of 5.14 eV is in good

Intercalation of Si between MoS₂ layers

• Rik van Bremen,
• Qirong Yao,
• Soumya Banerjee,
• Deniz Cakir,
• Nuri Oncel and
• Harold J. W. Zandvliet

Beilstein J. Nanotechnol. 2017, 8, 1952–1960, doi:10.3762/bjnano.8.196

• reveal no noteworthy differences. (4) Spatial maps of dI/dz reveal that the surface exhibits a uniform work function and a lattice constant of 3.16 Å. (5) X-ray photo-electron spectroscopy measurements reveal that sputtering of the MoS2/Si substrate does not lead to a decrease, but an increase of the

• differ significantly as is shown in Figure S2 in Supporting Information File 1. In order to remove the large-scale height variation from the topography scan, we simultaneously recorded a spatial map of dI/dz (Figure 3). The dI/dz signal only depends on the effective work function, also referred to as the