Silicene, germanene and other group IV 2D materials

• Patrick Vogt

Beilstein J. Nanotechnol. 2018, 9, 2665–2667, doi:10.3762/bjnano.9.248

• substrate can effect the buckling, which in turn, alters the properties of the 2D layer. The related modification might include, for example, the tunability of the electronic band gap, modification of the electronic band structure, or tuning the 2D topological properties. Some of these external influences

• 2D layer properties, for example, via chemical functionalization or external fields. This could be efficiently utilized in a transistor, where the electronic band gap can then be tuned by the electric field applied perpendicular to the lattice plane. As an example, ab initio calculations have shown

• that the two sub-lattices in silicene, resulting from the buckling, are moved further apart by an orthogonal electric field, which leads to a band gap opening [7][8]. Another important advantage of these new materials is the significant spin–orbit interaction, which also increases with increasing

Exploring the photoleakage current and photoinduced negative bias instability in amorphous InGaZnO thin-film transistors with various active layer thicknesses

• Dapeng Wang and
• Mamoru Furuta

Beilstein J. Nanotechnol. 2018, 9, 2573–2580, doi:10.3762/bjnano.9.239

• because of its excellent electrical and optical properties [5][6][7][8]. Although the band gap of IGZO (≈3.1 eV) is higher than the photon energy of visible light, photoinduced leakage current under visible-light irradiation can be detected in the oxide-based TFTs [9][10]. This is due to the fact that the

• though the photon energy is smaller than the band gap of IGZO. In terms of the a-IGZO material, the high-density electron traps exist at (EC − E) of over 2.7 eV [9], which affect the photoleakage current of a-IGZO TFTs. The total amount of trapped electrons increase with an increase in the TIGZO. The

Thickness-dependent photoelectrochemical properties of a semitransparent Co₃O₄ photocathode

• Malkeshkumar Patel and
• Joondong Kim

Beilstein J. Nanotechnol. 2018, 9, 2432–2442, doi:10.3762/bjnano.9.228

• regarding low-cost and reliable PEC cells [1][2][3][4][5][6][7][8]. For a widespread application of PEC cells, the photoelectrodes need to fulfill the criteria of (i) a low band gap (1.7–2.2 eV), (ii) low resistivity, (iii) low cost, (iv) corrosion stability and (v) a correct alignment of band edges with

• in Figure 5c supports the claim of porosity in the grown Co3O4 film and the void-free interface between Co3O4/FTO. Further, we estimated the thickness-dependent band-gap energies (Eg) of the Co3O4 samples using Tauc’s relation as shown in Figure 5d. The coexistence of bandgaps two distinct band gaps

• the Co3O4/FTO samples. Here t, T, λ, Eg, VFB and NA are the thickness of the Co3O4 layer, transmittance, photon wavelength, band gap, flat-band potential, and acceptor carrier concentration, respectively. Supporting Information Supporting Information File 146: Additional experimental data

Metal–dielectric hybrid nanoantennas for efficient frequency conversion at the anapole mode

• Valerio F. Gili,
• Lavinia Ghirardini,
• Davide Rocco,
• Giuseppe Marino,
• Ivan Favero,
• Iännis Roland,
• Giovanni Pellegrini,
• Lamberto Duò,
• Marco Finazzi,
• Luca Carletti,
• Andrea Locatelli,
• Aristide Lemaître,
• Dragomir Neshev,
• Costantino De Angelis,
• Giuseppe Leo and
• Michele Celebrano

Beilstein J. Nanotechnol. 2018, 9, 2306–2314, doi:10.3762/bjnano.9.215

• amplification [22] and enhanced Raman scattering [23] have been recently suggested. In this framework, AlxGa1−xAs, a III–V semiconductor, has become a popular material for nonlinear photonics thanks to its non-centrosymmetric structure and other important key assets including: i) a large band gap enabling TPA

Hierarchical heterostructures of Bi₂MoO₆ microflowers decorated with Ag₂CO₃ nanoparticles for efficient visible-light-driven photocatalytic removal of toxic pollutants

• Shijie Li,
• Wei Jiang,
• Shiwei Hu,
• Yu Liu,
• Yanping Liu,
• Kaibing Xu and
• Jianshe Liu

Beilstein J. Nanotechnol. 2018, 9, 2297–2305, doi:10.3762/bjnano.9.214

• absorption of the Ag2CO3/Bi2MoO6 heterostructures was substantially improved owing through the introduction of Ag2CO3 nanoparticles. Ag/Ag2CO3/Bi2MoO6 [32], Ag2MoO4/Bi2MoO6 [22], and Ag2CO3/Bi2MoO6 heterostrutures are VLD photocatalysts. The band gap energy (Eg) can be estimated from the Tauc plot: (αhν) = A

Lead-free hybrid perovskites for photovoltaics

• Oleksandr Stroyuk

Beilstein J. Nanotechnol. 2018, 9, 2209–2235, doi:10.3762/bjnano.9.207

Electrospun one-dimensional nanostructures: a new horizon for gas sensing materials

• Muhammad Imran,
• Nunzio Motta and
• Mahnaz Shafiei

Beilstein J. Nanotechnol. 2018, 9, 2128–2170, doi:10.3762/bjnano.9.202

• type of ZnO doping is with indium, for which the product is called “IZO”. When the amount of indium is greater than 0.05, amorphous In2O3 forms and leads to a pronounced decrease in grain size. The optical band gap energy of IZO NTs also decreases with increased doping levels. Doped indium atoms may

Light–Matter interactions on the nanoscale

• Mohsen Rahmani and
• Chennupati Jagadish

Beilstein J. Nanotechnol. 2018, 9, 2125–2127, doi:10.3762/bjnano.9.201

• graphene with electromagnetic radiation is fascinating due to the two-dimensional confinement of electrons and the exceptional band structure of graphene. Graphene has a simple band structure with zero band gap, but its optical response is nontrivial. Subsequently, other two-dimensional (2D) materials

Spin-coated planar Sb₂S₃ hybrid solar cells approaching 5% efficiency

• Pascal Kaienburg,
• Benjamin Klingebiel and
• Thomas Kirchartz

Beilstein J. Nanotechnol. 2018, 9, 2114–2124, doi:10.3762/bjnano.9.200

• ; hole transport material; solar cell; Introduction Antimony sulfide (Sb2S3) is a promising high band gap light absorber for solar cells [1][2][3][4][5]. The record efficiency of 7.5% [6] is comparable to that of other less investigated materials, such as the best lead-free perovskites [7], Cu2O [8] and

• -bandgap region [53][54][55][56] including band tails that yield the Urbach energy as a measure of disorder as well as the detection of (optically active) defects in the band gap which can act as recombination centers in a solar cell. The Sb-TU process shows a slight increase in uncovered substrate area

• conditions thus closely resemble those of the fabricated solar cells. The results for different crystallization temperatures in the Sb-TU process are shown in Figure 3c. For the sample crystallized at 265 °C and 300 °C, the measurement signal quickly saturates at energies above the band gap. At low energies

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

• can easily form nanostructures, such as nanoporous layers, nanowires or nanocolumns [5][11][12]. Because of its large band gap (3.2 eV [13]), light absorption is carried out by an organic or inorganic dye. The nanostructuration of the acceptor material is crucial for the cell performance [11], as it

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

• combined using Matthiessen’s formula. Accordingly, the Lombardi model (CVT) is used to express the carrier mobility in the channel [27]. Moreover, the intrinsic parameters of the materials (Si, Si1−xGex and Ge) such as band gap, mobility and the density of states were considered to be dependent on the Ge

• conventional design with Si channel shows a reduced OFF-state current compared to that of the investigated heterochannel designs, which is mainly due to the high band-gap energy and the low electron mobility associated to Si. On the other hand, the conventional Ge-DG-JL TFET design provides higher ON-state

• current. This is due to the smaller band gap energy of Ge, yielding a higher tunneling efficiency. Moreover, the higher electron mobility of Ge (3900 cm2·V−1·s−1) contributes to the increased drain current at the threshold voltage as compared to the conventional design with silicon (1400 cm2·V−1·s−1

Improving the catalytic activity for hydrogen evolution of monolayered SnSe_2(1−x)S_2x by mechanical strain

• Sha Dong and
• Zhiguo Wang

Beilstein J. Nanotechnol. 2018, 9, 1820–1827, doi:10.3762/bjnano.9.173

• . In this work, the electronic properties and catalytic behaviour for HER of SnSe2(1−x)S2x (x = 0, 0.125, 0.25, 0.375, 0.5, 0.625, 0.750, 0.875 and 1.0) monolayers were investigated by density functional theory (DFT). It was shown that band gap and catalytic activity of these alloys can be continuously

• , Figure 1g and Figure 1h, respectively. The substitution of S with Se does not affect the indirect bandgap semiconducting characteristics; however, the band gap is tuned with changing the content of Se, as shown in Figure 1d with the indirect band gap decreasing with increasing Se content. These results

• the top of S are close to zero at a tensile strain of 10%; thus, strain can be used to improve the catalytic activity for HER. As shown in Figure 4, also the band gaps show great dependence on the applied strain. The band gap decreases from 1.59 to 1.48 eV for the SnS2 monolayer as the compressive

Controllable one-pot synthesis of uniform colloidal TiO₂ particles in a mixed solvent solution for photocatalysis

• Jong Tae Moon,
• Seung Ki Lee and
• Ji Bong Joo

Beilstein J. Nanotechnol. 2018, 9, 1715–1727, doi:10.3762/bjnano.9.163

• explored semiconducting material that exists in abundance from natural resources. It has a wide range of applications including bio-separation, sensors, energy storage, catalysis and photocatalysis [1][2][3][4][5][6][7][8][9][10][11]. Due to its wide band gap energy (3.0–3.2 eV) between the conduction and

• . First, the semiconductor photocatalyst can absorb photon energy that is greater than its band gap and electrons in the valance band can be exited to the conduction band, resulting in photoexcited electron–hole pairs. Then, the photo-exited electron–hole can move to the surface of the photocatalyst

• without charge recombination. Finally, each charge carrier can be consumed for surface redox reactions [9][15]. To achieve high performance in the overall photocatalysis system, the efficiency of each step should be improved [13]. Regarding the point of light absorption, the band gap energy range of the

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

• , including a direct band gap, high absorption coefficient, large and balanced carrier mobility, high diffusion length, long carrier lifetime and high photoluminescence quantum yield. Within a few years of their discovery, these materials were successfully used to develop photovoltaic cells [2] with power

Free-radical gases on two-dimensional transition-metal disulfides (XS₂, X = Mo/W): robust half-metallicity for efficient nitrogen oxide sensors

• Chunmei Zhang,
• Yalong Jiao,
• Fengxian Ma,
• Sri Kasi Matta,
• Steven Bottle and
• Aijun Du

Beilstein J. Nanotechnol. 2018, 9, 1641–1646, doi:10.3762/bjnano.9.156

• NOx (x = 1, 2; Figure 2). Pristine 2D XS2 (X = Mo, W) has a band gap of approximately 2 eV. In the case of NO adsorbed on XS2 (X = Mo, W), a large density of spin-up electrons appear around the Fermi level, while no spin-down electrons appear. Analyzing the PDOS of a WS2 nanosheet with adsorbed NO

Sulfur-, nitrogen- and platinum-doped titania thin films with high catalytic efficiency under visible-light illumination

• Boštjan Žener,
• Lev Matoh,
• Giorgio Carraro,
• Bojan Miljević and
• Romana Cerc Korošec

Beilstein J. Nanotechnol. 2018, 9, 1629–1640, doi:10.3762/bjnano.9.155

• , band gap measurements). The photocatalytic activity of the prepared thin films was determined by measuring the degradation rate of plasmocorinth B (PB), an organic pigment used in the textile industry, which can pose an environmental risk when expelled into wastewater. A kinetic model for adsorption

• rather there exists an optimal particle size for pure nanocrystalline TiO2 [19]. This is due to surface recombination of electron–hole pairs in samples with particle sizes smaller than 6 nm. One of the main drawbacks of using TiO2 as a photocatalyst is the width of its band gap (3.2 eV), which means the

• of the band gap by introducing a new energy level close to the valence band. Nitrogen doping can also create impurity energy levels above the valence band, thus effectively also narrowing the band gap [35][36]. Illumination with visible light can then excite electrons from impurity energy levels into

Sheet-on-belt branched TiO₂(B)/rGO powders with enhanced photocatalytic activity

• Huan Xing,
• Wei Wen and
• Jin-Ming Wu

Beilstein J. Nanotechnol. 2018, 9, 1550–1557, doi:10.3762/bjnano.9.146

• . The TGN-branch 4 h sample exhibits almost the same absorbance (Figure 6a) and the same band gap of 2.87 eV (Figure 6b) compared to TGN. This can be attributed to the same phase composition of TiO2(B) in both samples. The evaluated band gap of 2.87 eV for TiO2(B) agrees with that (2.9 eV) reported by

• Kandiel et al. [25]. This band gap value is smaller than that of 3.2 eV for bulk anatase TiO2 [27]. Chakraborty et al. also reported that the absorption band edge of the pure TiO2(B) is located at a relatively longer wavelength compared to that of the pure anatase TiO2 [21]. The low temperature nitrogen

• , and (d) O 1s for sample TGN-branch 4 h. (a) UV–vis diffuse reflectance spectra of TGN and TGN-branch 4 h. (b) Re-plotting of (a) in the α1/2 ~ hν coordinate to evaluate the corresponding band gap, assuming an indirect transition between bands for TiO2. Photodegradation of phenol in the presence of

Photoluminescence of CdSe/ZnS quantum dots in nematic liquid crystals in electric fields

• Margarita A. Kurochkina,
• Elena A. Konshina and
• Daria Khmelevskaia

Beilstein J. Nanotechnol. 2018, 9, 1544–1549, doi:10.3762/bjnano.9.145

• University (Minsk). The shell of ZnS with wider band gap prevents a degradation of the CdSe core by passivation of broken bonds on its surface. Quantum dots were covered with а layer of surface-active trioctylphosphine oxide (TOPO) molecules. The nematic alkylcyanobiphenyl-based liquid crystal ZhK-1289

• dependence on two independent, but spectrally overlapping, processes. The first process involves the recombination of the so-called “internal” exciton with energy close to the width of the band gap and a decay time of about 20–30 ns, depending on the size of the quantum dots. The second process is associated

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

• surface of the semiconductor. When photons with energy greater than the band gap energy of the semiconductor photocatalyst (SP) are absorbed, photogenerated electrons are excited to conduction band (CB) leaving behind holes at the valence band (VB) as per Equation 1: These photogenerated species

• cases, hole scavengers are used to facilitate the electron–hole separation process. However, application of TiO2 in photocatalysis is largely restricted mainly due to the following reasons. (i) The wide band gap of 3.2 eV causes excitation of electrons from the valence band under irradiation of UV light

• , or B narrows the band gap either by creating a mid-band gap or shifting the valence band to upper positions, resulting in a redshift. Even modification of titania with semiconductor oxides or sulfides improves the light absorption. It was evident from UV–vis DRS spectra that light absorption is

Robust midgap states in band-inverted junctions under electric and magnetic fields

• Álvaro Díaz-Fernández,
• Natalia del Valle and
• Francisco Domínguez-Adame

Beilstein J. Nanotechnol. 2018, 9, 1405–1413, doi:10.3762/bjnano.9.133

• Figure 5 it may be surprising to see that the Landau bands shift below the band edge, leading to the apparent and erroneous belief that the latter enter the band gap. The effect of the electric field is to bend the constant band edges shown in Figure 1a upwards due to the presence of the electrostatic

• potential eFz, and so the Landau levels of the conduction band can move towards lower energies as long as the corresponding wave functions are not inside the band gap in position space. Finally, it deserves consideration the previous discussion for low values of . As we can see in Figure 6, the parabolic

Predicting the strain-mediated topological phase transition in 3D cubic ThTaN₃

• Chunmei Zhang and
• Aijun Du

Beilstein J. Nanotechnol. 2018, 9, 1399–1404, doi:10.3762/bjnano.9.132

• Chunmei Zhang Aijun Du School of Chemistry, Physics and Mechanical Engineering, Queensland University of Technology, Gardens Point Campus, QLD 4001, Brisbane, Australia 10.3762/bjnano.9.132 Abstract The cubic ThTaN3 compound has long been known as a semiconductor with a band gap of approximately

• 1 eV, but its electronic properties remain largely unexplored. By using density functional theory, we find that the band gap of ThTaN3 is very sensitive to the hydrostatic pressure/strain. A Dirac cone can emerge around the Γ point with an ultrahigh Fermi velocity at a compressive strain of 8

• %. Interestingly, the effect of spin–orbital coupling (SOC) is significant, leading to a band gap reduction of 0.26 eV in the ThTaN3 compound. Moreover, the strong SOC can turn ThTaN3 into a topological insulator with a large inverted gap up to 0.25 eV, which can be primarily attributed to the inversion between

Computational exploration of two-dimensional silicon diarsenide and germanium arsenide for photovoltaic applications

• Sri Kasi Matta,
• Chunmei Zhang,
• Yalong Jiao,
• Anthony O'Mullane and
• Aijun Du

Beilstein J. Nanotechnol. 2018, 9, 1247–1253, doi:10.3762/bjnano.9.116

• . Furthermore, band-gap tuning is also possible by application of tensile strain. Our results highlight a new family of 2D materials with great potential for solar cell applications. Keywords: density functional theory (DFT); photovoltaic applications; solar cell; two-dimensional semiconductors; Introduction

• ]. However, they did not report the band structure or the band gap values of these materials. Later, Wu et al. performed theoretical studies on silicon and germanium arsenides [9] to predict and reaffirm that m-SiAs/GeAs and o-SiAs2/GeAs2 are indeed semiconductors. The studies were based on band-structure

• the same IV–V group combination, we focus our study on two-dimensional SiAs2 and GeAs2 and compare them with their bulk counter parts with regard to electronic band structure, phonon-vibration frequencies, optical properties, band gap modulation behavior and predict their potential applications

Theoretical study of strain-dependent optical absorption in a doped self-assembled InAs/InGaAs/GaAs/AlGaAs quantum dot

• Tarek A. Ameen,
• Hesameddin Ilatikhameneh,
• Archana Tankasala,
• Yuling Hsueh,
• James Charles,
• Jim Fonseca,
• Michael Povolotskyi,
• Jun Oh Kim,
• Sanjay Krishna,
• Monica S. Allen,
• Jeffery W. Allen,
• Rajib Rahman and
• Gerhard Klimeck

Beilstein J. Nanotechnol. 2018, 9, 1075–1084, doi:10.3762/bjnano.9.99

• gap and confinement energies work with each other, whereas when the height is changed, the band gap and confinement energies work against each other. Increasing the mole fraction if In in the strain controlling layer works in the same way as increasing the dot diameter and changes the strain leading

• NEMO5 and used to simulate characteristics of an InAs/GaAs/AlAs quantum dot systems. Increasing the dot diameter results in a shift of the absorption peaks towards longer wavelengths, while increasing the dot height does not have a significant effect on wavelength. When the diameter is changed, the band

Non-equilibrium electron transport induced by terahertz radiation in the topological and trivial phases of Hg_1−xCd_xTe

• Alexandra V. Galeeva,
• Alexey I. Artamkin,
• Alexey S. Kazakov,
• Sergey N. Danilov,
• Sergey A. Dvoretskiy,
• Nikolay N. Mikhailov,
• Ludmila I. Ryabova and
• Dmitry R. Khokhlov

Beilstein J. Nanotechnol. 2018, 9, 1035–1039, doi:10.3762/bjnano.9.96

• . 53, 119991 Moscow, Russia 10.3762/bjnano.9.96 Abstract Terahertz photoconductivity in heterostructures based on n-type Hg1−xCdxTe epitaxial films both in the topological phase (x < 0.16, inverted band structure, zero band gap) and the trivial state (x > 0.16, normal band structure) has been studied

• . It was assumed that the negative photoresponse in the samples with the normal band structure is most likely related to the electron gas heating, while the positive photoconductivity in the zero band gap mercury cadmium telluride was reasonable to associate with interband transitions. In this work, we

An implementation of spin–orbit coupling for band structure calculations with Gaussian basis sets: Two-dimensional topological crystals of Sb and Bi

• Sahar Pakdel,
• Mahdi Pourfath and
• J. J. Palacios

Beilstein J. Nanotechnol. 2018, 9, 1015–1023, doi:10.3762/bjnano.9.94

• recently added to the growing library of 2D crystals. Its recent isolation and characterization [33], is bringing this material into the focus of the research community. Several DFT studies on this material have predicted a number of exciting physico-chemical properties, including a tunable band gap with