Recent highlights in nanoscale and mesoscale friction

• Andrea Vanossi,
• Dirk Dietzel,
• Andre Schirmeisen,
• Ernst Meyer,
• Rémy Pawlak,
• Thilo Glatzel,
• Marcin Kisiel,
• Shigeki Kawai and
• Nicola Manini

Beilstein J. Nanotechnol. 2018, 9, 1995–2014, doi:10.3762/bjnano.9.190

• , which can occur through precursor events. These phenomena were investigated in macroscopic-friction experiments [89][90] and simulated by means of several theoretical approaches [91][92][93][94][95][96][97][98][99]. Notice however that a different behavior was observed for Sb particles on MoS2. Here

• [101] leading to a size-dependent breakdown of structural lubricity. As anticipated, the critical length scale depends sensitively on the ratio between the slider elasticity and the interaction forces with the substrate. Consequently, this transition was experimentally observed only for the MoS2

• research groups have been investigating the frictional properties of nanoscale systems confined between two sliding blocks. This intendedly vague indication of “systems” includes liquid lubricants in the boundary-lubrication regime, but also solid lubricants such as graphite or graphene or MoS2 flakes

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

• hydrogen. Two-dimensional (2D) atomic layer thin materials, such as monolayer transition-metal dichalcogenides (TMDs) [11][12][13][14][15][16][17][18][19], have demonstrated many fascinating properties, including the substitution of Pt as an electrocatalyst for HER. 2D MoS2 has been widely studied

• . Yue et al. [42] investigated the electronic properties of monolayer MoS2 under elastic strain and found that the direct-to-indirect transition of MoS2 occurs at a strain of 0.01, and the semiconductor-to-metal transition occurs at a strain of 0.10. Huang et al. [22] reported that both compressive (−11

• %) and tensile (14%) strain can trigger the semiconductor–metal transition in the SnSe2 monolayer. Furthermore, Scalise et al. [15] showed that the electronic structure of the MoS2 monolayer can be reversibly tuned from direct to indirect by applying strain (ca. 2%). Much research effort has been devoted

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

• ), CIRMAP, Research Institute for Materials Science and Engineering, University of Mons, Mons, Belgium 10.3762/bjnano.9.160 Abstract Densely populated edge-terminated vertically aligned two-dimensional MoS2 nanosheets (NSs) with thicknesses ranging from 5 to 20 nm were directly synthesized on Mo films

• transferred NSs sample showed excellent field-emission properties. A low turn-on field of 3.1 V/μm at a current density of 10 µA/cm2 was measured. The low turn-on field is attributed to the morphology of the NSs exhibiting vertically aligned sheets of MoS2 with sharp and exposed edges. Our findings show that

• the fabricated MoS2 NSs could have a great potential as robust high-performance electron-emitter material for various applications such as microelectronics and nanoelectronics, flat-panel displays and electron-microscopy emitter tips. Keywords: chemical vapor deposition (CVD); field emission

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

• ][16], phosphorene [9], siligraphene (SiC5) [10] and molybdenum disulfide (MoS2) [11][17] possess a high specific surface area and high electrical conductivity making them the ideal candidates for gas sensors. In particular, investigations of XS2-based (X = Mo, W) monolayer nanodevices demonstrate that

• they are ultra-sensitive to a number of molecules that are important in environmental studies [18][19][20][21][22][23][24][25][26]. More specifically, it has been suggested that MoS2 exhibits ultrahigh sensitivity to the adsorption of paramagnetic gases such as NO and NO2 [11]. Single-layer MoS2 has

• been confirmed to be a good candidate for fabricating field-effect transistor (FET) sensors for NO with high mobility at room temperature [17], and the detection offers a high sensitivity and rapid current response. However, the detailed mechanism regarding the interaction between the MoS2 surface and

Atomistic modeling of tribological properties of Pd and Al nanoparticles on a graphene surface

• Alexei Khomenko,
• Miroslav Zakharov,
• Denis Boyko and
• Bo N. J. Persson

Beilstein J. Nanotechnol. 2018, 9, 1239–1246, doi:10.3762/bjnano.9.115

• . Figure 5 depicts the frictional shear stress τ as a function of the contact area. The average shear stress is τ ≈ 9.9 MPa for the Al particles and 12.2 MPa for Pd particles. The values of shear stress in experiments (Figure 2 in [7]) for Sb particles on MoS2 substrate varies from 1 MPa to 3 MPa with

Sensing behavior of flower-shaped MoS₂ nanoflakes: case study with methanol and xylene

• Maryam Barzegar,
• Masoud Berahman and
• Azam Iraji zad

Beilstein J. Nanotechnol. 2018, 9, 608–615, doi:10.3762/bjnano.9.57

• emerging new group of materials known as transition metal dichalcogenides (TMDs), which have significant electrical, optical, and transport properties. MoS2 is one of the well-known 2D materials in this group, which is a semiconductor with controllable band gap based on its structure. The hydrothermal

• process is known as one of the scalable methods to synthesize MoS2 nanostructures. In this study, the gas sensing properties of flower-shaped MoS2 nanoflakes, which were prepared from molybdenum trioxide (MoO3) by a facile hydrothermal method, have been studied. Material characterization was performed

• functional theory; gas sensor; hydrothermal method; methanol; MoS2 nanoflakes; xylene vapor; Introduction Recent efforts in exploring two-dimensional (2D) materials have led to the introduction of a new family of materials known as transition metal dichalcogenides (TMDs), which show remarkable electrical

Review: Electrostatically actuated nanobeam-based nanoelectromechanical switches – materials solutions and operational conditions

• Liga Jasulaneca,
• Jelena Kosmaca,
• Raimonds Meija,
• Jana Andzane and
• Donats Erts

Beilstein J. Nanotechnol. 2018, 9, 271–300, doi:10.3762/bjnano.9.29

• well as on the band structure of contacting materials [86], and can be modulated by an applied source–drain bias in the on state of a NEM switch. For example, the change in the transport mechanism from direct tunnelling at low drain bias to FN tunnelling at the higher drain bias was shown for a Pd–MoS2

Transition from silicene monolayer to thin Si films on Ag(111): comparison between experimental data and Monte Carlo simulation

• Alberto Curcella,
• Romain Bernard,
• Yves Borensztein,
• Silvia Pandolfi and
• Geoffroy Prévot

Beilstein J. Nanotechnol. 2018, 9, 48–56, doi:10.3762/bjnano.9.7

• Å has been precisely measured for the (4 × 4) structure [8][9][10]. Silicene growth has also been reported on other substrates, such as Ir [11], ZrB2 [12], or MoS2 [13], although the precise crystallographic structure of these layers has not been elucidated yet. In spite of its atomic structure

Ab initio study of adsorption and diffusion of lithium on transition metal dichalcogenide monolayers

• Xiaoli Sun and
• Zhiguo Wang

Beilstein J. Nanotechnol. 2017, 8, 2711–2718, doi:10.3762/bjnano.8.270

• deposition [12][13][14]. MX2 has received tremendous attention as an alternative to graphite for the anode material in LIBs [15][16]. In particular, MoS2 has been well-investigated as an anode material for LIBs both theoretically and experimentally. A graphene like-MoS2/graphene composite was shown to

• exhibit a high specific capacity of 1400 mA h/g and good rate performance as well as cycling ability [17]. It was reported that MoS2 zigzag nanoribbons are promising electrode materials for LIBs with a high power density and fast charge/discharge rates [18]. The presence of structural defects can enhance

• the adsorption of Li atoms onto two-dimensional materials. Different from the situation where Li atoms are trapped by the defects in graphene, the presence of structural defects does not affect the diffusion of lithium [19]. The main drawback of MoS2 is its poor electrical conductivity. Various

Optical contrast and refractive index of natural van der Waals heterostructure nanosheets of franckeite

• Patricia Gant,
• Foad Ghasemi,
• David Maeso,
• Carmen Munuera,
• Elena López-Elvira,
• Riccardo Frisenda,
• David Pérez De Lara,
• Gabino Rubio-Bollinger,
• Mar Garcia-Hernandez and
• Andres Castellanos-Gomez

Beilstein J. Nanotechnol. 2017, 8, 2357–2362, doi:10.3762/bjnano.8.235

• that franckeite is a semiconductor with narrow band gap. Other 2D semiconductors, such as MoS2, present refractive indexes whose imaginary part vanishes within the visible region of the spectrum. Moreover, the refractive index of transition-metal dichalcogenides shows sharp features associated to the

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

• , Grand Forks, ND 58202, USA 10.3762/bjnano.8.196 Abstract We report a combined experimental and theoretical study of the growth of sub-monolayer amounts of silicon (Si) on molybdenum disulfide (MoS2). At room temperature and low deposition rates we have found compelling evidence that the deposited Si

• atoms intercalate between the MoS2 layers. Our evidence relies on several experimental observations: (1) Upon the deposition of Si on pristine MoS2 the morphology of the surface transforms from a smooth surface to a hill-and-valley surface. The lattice constant of the hill-and-valley structure amounts

• to 3.16 Å, which is exactly the lattice constant of pristine MoS2. (2) The transitions from hills to valleys are not abrupt, as one would expect for epitaxial islands growing on-top of a substrate, but very gradual. (3) I(V) scanning tunneling spectroscopy spectra recorded at the hills and valleys

Coexistence of strongly buckled germanene phases on Al(111)

• Weimin Wang and
• Roger I. G. Uhrberg

Beilstein J. Nanotechnol. 2017, 8, 1946–1951, doi:10.3762/bjnano.8.195

• bilayer germanene on Cu(111) at room temperature. Scanning tunneling spectroscopy showed a “V” shaped density of states, which was also observed by Zhang et al. [12], who synthesized germanene on MoS2 at room temperature. Al(111) was chosen as a substrate to deposit germanene by Derivaz et al. [13] with

α-Silicene as oxidation-resistant ultra-thin coating material

• Ali Kandemir,
• Fadil Iyikanat,
• Cihan Bacaksiz and
• Hasan Sahin

Beilstein J. Nanotechnol. 2017, 8, 1808–1814, doi:10.3762/bjnano.8.182

• calculations [9]. Bulk forms of transition-metal dichalcogenides (TMDs) are well-known coating materials, and the respective 2D TMDs can be used as surface protection. In addition, MoS2 is one of the most widely used lubricant coating material [10]. Theoretical and experimental studies have demonstrated that

• single-layer MoS2 and single layer W(S/Se)2 can be used as a protective nanocoating material [11][12][13][14]. One of the most challenging members of the 2D material family is silicene [15][16][17][18][19], the silicon analogue of graphene. After theoretical prediction [18], silicene was synthesized [19

Adsorption and diffusion characteristics of lithium on hydrogenated α- and β-silicene

• Fadil Iyikanat,
• Ali Kandemir,
• Cihan Bacaksiz and
• Hasan Sahin

Beilstein J. Nanotechnol. 2017, 8, 1742–1748, doi:10.3762/bjnano.8.175

• atoms with silicene is stronger than with graphene, and the adsorption of metal atoms leads to the metalization of silicene [37]. It was calculated that the adsorption of Li atoms results in the stabilization of the unstable distorted T-phase of MoS2 [38]. In addition, Zr-based MXenes were found to be

Two-dimensional carbon-based nanocomposites for photocatalytic energy generation and environmental remediation applications

• Suneel Kumar,
• Ashish Kumar,
• Ashish Bahuguna,
• Vipul Sharma and
• Venkata Krishnan

Beilstein J. Nanotechnol. 2017, 8, 1571–1600, doi:10.3762/bjnano.8.159

• higher than pure graphene cocatalyst. Similarly some other groups have also investigated the cocatalytic role of graphene, for example Ye et al. [116] have reported CdS–MoS2–graphene nanocomposites, which is active in visible light for hydrogen generation. They reported the hydrogen evolution rate of 1.8

• mmol h−1 in lactic acid solution at 420 nm, which is much higher than that of the Pt–CdS system in the same solution. This high H2 evolution rate was mainly achieved because of the excellent cocatalytic function of MoS2–graphene, which leads to the higher number of reaction sites and fast charge

• transfer. Moreover, in nanometer-sized MoS2, exposed S atoms have strong affinity to H+ ions in solution, which are reduced to H2 by transferred electrons from the CB of CdS. Similarly, a noble-metal-free, ternary nanocomposite of TiO2–MoS2–graphene has been reported by Yu et al. for H2 generation [126

Development of a nitrogen-doped 2D material for tribological applications in the boundary-lubrication regime

• Shende Rashmi Chandrabhan,
• Velayudhanpillai Jayan,
• Somendra Singh Parihar and
• Sundara Ramaprabhu

Beilstein J. Nanotechnol. 2017, 8, 1476–1483, doi:10.3762/bjnano.8.147

• tribological properties of nanolubricant based on metals [16], metal oxides [17][18], MoS2 [4][19], boron [20] and WS2 [21]. Among all the solid additives, 2D graphene is a promising material to improve the tribological performance because of its high surface area to volume ratio and excellent mechanical

3D continuum phonon model for group-IV 2D materials

• Morten Willatzen,
• Lok C. Lew Yan Voon,
• Appala Naidu Gandi and
• Udo Schwingenschlögl

Beilstein J. Nanotechnol. 2017, 8, 1345–1356, doi:10.3762/bjnano.8.136

• beyond the analytical solutions sought for in the current manuscript. Furthermore, we have included a study of a well-known compound 2D material (molybdenum disulfide MoS2) in order to further understand the properties derived for the elemental materials. Results and Discussion Continuum model The 2D

• of the problem. In order to simplify and then solve it, it is necessary to specify the crystal symmetry of the vibrating system. The three problems considered in this article are graphene, silicene and MoS2. The Bravais lattice symmetries of the single-layer graphene (D6h ≡ 6/mmm) and MoS2

• () structures belong to the hexagonal system, while silicene belongs to the trigonal system (point group D3d). Graphene and silicene are non-piezoelectric materials because of the inversion symmetry of the unit cell, while MoS2 is piezoelectric because its unit cell exhibits inversion asymmetry. Application

Two-dimensional silicon and carbon monochalcogenides with the structure of phosphorene

• Dario Rocca,
• Ali Abboud,
• Ganapathy Vaitheeswaran and
• Sébastien Lebègue

Beilstein J. Nanotechnol. 2017, 8, 1338–1344, doi:10.3762/bjnano.8.135

• two-dimensional materials has increased exponentially [1]. Following the initial report of the existence of graphene [2], it was shown that isolated sheets of other layered compounds, such as h-BN or MoS2 among others, could be obtained as well [3][4]. These compounds demonstrate properties of the

Growth, structure and stability of sputter-deposited MoS₂ thin films

• Reinhard Kaindl,
• Bernhard C. Bayer,
• Roland Resel,
• Thomas Müller,
• Viera Skakalova,
• Gerlinde Habler,
• Rainer Abart,
• Alexey S. Cherevan,
• Dominik Eder,
• Maxime Blatter,
• Fabian Fischer,
• Jannik C. Meyer,
• Dmitry K. Polyushkin and
• Wolfgang Waldhauser

Beilstein J. Nanotechnol. 2017, 8, 1115–1126, doi:10.3762/bjnano.8.113

• , Austria Institute of Life Technologies, HES-SO Valais-Wallis, Route du Rawyl 64, CP, 1950 Sion 2, Switzerland 10.3762/bjnano.8.113 Abstract Molybdenum disulphide (MoS2) thin films have received increasing interest as device-active layers in low-dimensional electronics and also as novel catalysts in

• electrochemical processes such as the hydrogen evolution reaction (HER) in electrochemical water splitting. For both types of applications, industrially scalable fabrication methods with good control over the MoS2 film properties are crucial. Here, we investigate scalable physical vapour deposition (PVD) of MoS2

• films by magnetron sputtering. MoS2 films with thicknesses from ≈10 to ≈1000 nm were deposited on SiO2/Si and reticulated vitreous carbon (RVC) substrates. Samples deposited at room temperature (RT) and at 400 °C were compared. The deposited MoS2 was characterized by macro- and microscopic X-ray

In-situ monitoring by Raman spectroscopy of the thermal doping of graphene and MoS₂ in O₂-controlled atmosphere

• Aurora Piazza,
• Filippo Giannazzo,
• Gianpiero Buscarino,
• Gabriele Fisichella,
• Antonino La Magna,
• Fabrizio Roccaforte,
• Marco Cannas,
• Franco Mario Gelardi and
• Simonpietro Agnello

Beilstein J. Nanotechnol. 2017, 8, 418–424, doi:10.3762/bjnano.8.44

• O2) on the doping of monolayers of graphene (Gr) on SiO2 and Si substrates, and on the doping of MoS2 multilayer flakes transferred on the same substrates have been investigated. The investigations were carried out by in situ micro-Raman spectroscopy during thermal treatments up to 430 °C, and by

• red shift due to thermal effects and a blue shift induced by doping. This shows the potential of in situ measurements to follow the doping kinetics. The treatment of MoS2 in O2 has evidenced a progressive erosion of the flakes without relevant spectral changes in their central zone during in situ

• measurements. The formation of MoO3 on the edges of the flakes is observed indicative of the oxygen-activated transformation. Keywords: two-dimensional (2D) materials; graphene; MoS2; Raman spectroscopy; thermal doping; Introduction A wide interest for two-dimensional (2D) materials has grown in recent years

Impact of contact resistance on the electrical properties of MoS₂ transistors at practical operating temperatures

• Filippo Giannazzo,
• Gabriele Fisichella,
• Aurora Piazza,
• Salvatore Di Franco,
• Giuseppe Greco,
• Simonpietro Agnello and
• Fabrizio Roccaforte

Beilstein J. Nanotechnol. 2017, 8, 254–263, doi:10.3762/bjnano.8.28

• , University of Palermo, Via Archirafi 36, 90143 Palermo, Italy Department of Physics and Astronomy, University of Catania, Via Santa Sofia, 64, 95123 Catania, Italy 10.3762/bjnano.8.28 Abstract Molybdenum disulphide (MoS2) is currently regarded as a promising material for the next generation of electronic

• and optoelectronic devices. However, several issues need to be addressed to fully exploit its potential for field effect transistor (FET) applications. In this context, the contact resistance, RC, associated with the Schottky barrier between source/drain metals and MoS2 currently represents one of the

• main limiting factors for suitable device performance. Furthermore, to gain a deeper understanding of MoS2 FETs under practical operating conditions, it is necessary to investigate the temperature dependence of the main electrical parameters, such as the field effect mobility (μ) and the threshold

The difference in the thermal conductivity of nanofluids measured by different methods and its rationalization

• Aparna Zagabathuni,
• Sudipto Ghosh and
• Shyamal Kumar Pabi

Beilstein J. Nanotechnol. 2016, 7, 2037–2044, doi:10.3762/bjnano.7.194

• in the specific heat of the nanofluid. Using LFM, Zeng et al. [3] have reported 38.7% enhancement for 1.0 vol % loading of MoS2 nanoparticles in oil. They recognized that the thermal conductivity enhancement diminishes when the temperature is close to the flash point of the base oil. Based on several

Role of RGO support and irradiation source on the photocatalytic activity of CdS–ZnO semiconductor nanostructures

• Suneel Kumar,
• Rahul Sharma,
• Vipul Sharma,
• Gurunarayanan Harith,
• Vaidyanathan Sivakumar and
• Venkata Krishnan

Beilstein J. Nanotechnol. 2016, 7, 1684–1697, doi:10.3762/bjnano.7.161

• degradation of organic pollutants [32][33][34][35]. In one of our recent works [34], we have reported the synergistic effect of MoS2–RGO support to improve the photocatalytic performance of ZnO nanoparticles. However, the role played by RGO support in enhancing the photocatalytic performance of the

Nanostructured germanium deposited on heated substrates with enhanced photoelectric properties

• Ionel Stavarache,
• Valentin Adrian Maraloiu,
• Petronela Prepelita and
• Gheorghe Iordache

Beilstein J. Nanotechnol. 2016, 7, 1492–1500, doi:10.3762/bjnano.7.142

• % over the whole investigated frequency range (1–4 kHz), which is a good result compared with other new materials and test structures reported in literature (18% in the case of graphene monolayer/germanium heterojunctions or about 13% for MoS2/Si heterojunctions) [48][49]. This is an indication of the

• high quality of the materials deposited by RF-sputtering for this experiment. The results of response time measurements show that photodetector structure as realized here is much quicker than Ge–graphene based photodetectors (tr ≈ 23 µs and tf ≈ 108 µs) [48], MoS2-based photodetectors (tr ≈ 3 µs and tf

Fracture behaviors of pre-cracked monolayer molybdenum disulfide: A molecular dynamics study

• Qi-lin Xiong,
• Zhen-huan Li and
• Xiao-geng Tian

Beilstein J. Nanotechnol. 2016, 7, 1411–1420, doi:10.3762/bjnano.7.132

• and Vibration, Xi’an Jiaotong University, Xi’an 710049, China 10.3762/bjnano.7.132 Abstract The fracture strength and crack propagation of monolayer molybdenum disulfide (MoS2) sheets with various pre-existing cracks are investigated using molecular dynamics simulation (MDS). The uniaxial tensions of

• pre-cracked monolayer MoS2 sheets with different crack tips, different locations of crack, different crack lengths and angled cracks are simulated and studied. The results show that the configuration of crack tip can influence significantly the fracture behaviors of monolayer MoS2 sheets while the

• location of crack does not influence the fracture strength. With the increase of crack length, the fracture strength of monolayer MoS2 sheets reduces almost linearly, and the fracture of monolayer MoS2 sheets is transformed from almost brittle to ductile. By making comparison between the MDS results and