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Precise characterization of the mechanical properties of ultrathin films is of paramount importance for both a fundamental understanding of nanoscale materials and for continued scaling and improvement of nanotechnology. In this work, we use coherent extreme ultraviolet beams to characterize the full elastic tensor of isotropic ultrathin films down to 11 nm in thickness. We simultaneously extract the Young's modulus and Poisson's ratio of low-k a-SiC:H films with varying degrees of hardness and average network connectivity in a single measurement. Contrary to past assumptions, we find that the Poisson's ratio of such films is not constant but rather can significantly increase from 0.25 to >0.4 for a network connectivity below a critical value of ~2.5. Physically, the strong hydrogenation required to decrease the dielectric constant k results in bond breaking, lowering the network connectivity, and Young's modulus of the material but also decreases the compressibility of the film. This new understanding of ultrathin films demonstrates that coherent EUV beams present a new nanometrology capability that can probe a wide range of novel complex materials not accessible using traditional approaches. [ABSTRACT FROM AUTHOR]

We describe the implementation of an experimental setup based on Surface Enhanced Raman Spectroscopy (SERS) to investigate polymer interdiffusion. Ultra-thin bilayer films of deuterated polystyrene (dPS) and polystyrene (PS) are placed in contact onto SERS-active gold substrates with inverted square-base pyramidal geometry and subsequently annealed. Initially, the Raman spectrum shows only spectral features of the polymer adjacent to the substrate. Upon annealing, Raman bands of the polymer located far from the substrate start to emerge, an indication of chain diffusion into the substrate hotspot and mixing between polymer layers. The kinetics of the process is consistent with transport of polymer chains in nanometer scale, with diffusion coefficients in the range 10-13 - 10-15cm2/s. The temperature response of the process is characterized by an activation energy of 48.93±1.5 kcal/mol, in excellent agreement with earlier experiments. SERS experiments provide a powerful and reliable experimental platform to characterize polymer interdiffusion without the need of chemical labeling, with several prospective applications to the study of chain dynamics in advanced polymer-based nanocomposite materials. Copyright © 2016 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

FeO(1 1 1) films grown on a Au(1 1 1) substrate were studied in the low temperature CO oxidation reaction at near-atmospheric pressure. Enhanced reactivity over the otherwise inert Au(1 1 1) surface was only observed if the iron oxide films possessed so-called 'weakly bound oxygen' (WBO) species upon oxidation at elevated pressures. The reaction rate measured under O-rich conditions (CO/O2=1/5, totally 60 mbar, He balance to 1 bar) was found to correlate with the total amount of WBO measured in the 'oxidized' films by temperature programmed desorption. The initial reaction rate measured as a function of the film coverage showed a maximum at about one monolayer (ML), in contrast to ≈0.4 ML obtained for the Pt(1 1 1)-supported FeO(1 1 1) films measured with the same setup. When compared to FeO(1 1 1)/Pt(1 1 1), WBO species on FeO(1 1 1)/Au(1 1 1) desorb at a much lower (i.e., by ≈200 K) temperature, but also in much smaller amounts. Scanning tunneling microscopy studies showed that the FeO(1 1 1) layer on Au(1 1 1) is fairly stable towards high pressure oxidation in the low coverage regime, but undergoes substantial reconstruction at near-monolayer coverages, thus resulting in poorly-defined structures. Comparison of structure-reactivity relationships observed for Au(1 1 1) and Pt(1 1 1) supported FeO(1 1 1) films revealed the complex role of a metal support on reactivity. Although a strong interaction with the Pt(1 1 1) surface stabilizes a planar FeO(1 1 1)-derived structure for the active oxide phase, in the case of a more weakly interacting Au(1 1 1) surface, the reaction atmosphere induces structural transformations governed by the thermodynamic phase diagram of the iron oxide, albeit it seems crucial to have a dense FeO(1 1 1) film as the precursor. [ABSTRACT FROM AUTHOR]

For the first time ultrathin films of palladium oxide are set forth as the perspective materials for detecting oxidizing gases. PdO 1± x thin films were prepared by thermal oxidation of previously formed Pd layers. By RHEED and HRTEM investigations it has been established that homogenous polycrystalline PdO 1± x films (thickness was about 5 – 10 nm) with grain size ∼ 7 – 15 nm were formed on polished poly-Al 2 O 3 , SiO 2 /Si(100), optical quartz, and amorphous C/KCl substrates. At ozone detecting in air PdO 1± x films have shown high values of sensor response, signal stability, and reproducibility of sensor response. At fabrication of gas sensors usage of PdO 1± x ultrathin films has some advantages in comparison with other materials. Firstly, PdO 1± x films have shown high values of sensor response, signal stability, and reproducibility of sensor response. Secondly, the synthesis procedure of binary films PdO 1± x is rather simple and is compatible with planar processes of a microelectronic industry also. [ABSTRACT FROM AUTHOR]

Recent development in epidermal and bionic electronics systems has promoted the increasing demand for supercapcacitors with micrometer-thickness and good compatibility. Here, a highly flexible free-standing epidermal supercapacitor (SC-E) with merely 1 μm thickness and high performance is developed. Single-walled carbon nanotube/poly(3,4-ethylenedioxythiophene) hybrid films with unique inner-connected reticulation are adopted as electrodes for ultrathin structure and high electric conductivity. Then, based on two substrates with different surface energies, a stepwise lift-off method is presented to peel off the ultrathin integrated supercapacitor from the substrates nondestructively. As a result of the high conductive hybrid electrodes and the thin electrolyte layer, the as-designed supercapacitors (based on the total mass of two electrodes) achieve a good capacitance of 56 F g−1 and a superhigh power density of 332 kW kg−1, which manifest superior performance in contrast to the other devices fabricated by traditional electrodes. Meanwhile, the ultrashort response time of 11.5 ms enables the epidermal supercapacitor (SC-E) work for high-power units. More importantly, the free-standing structure and outstanding flexibility (105 times bending) endow the SC-E with excellent compatibility to be integrated and work in the next generation of smart and epidermal systems. [ABSTRACT FROM AUTHOR]

In the present work, photoactive cation N, N′-Dimenthyl-9, 9’-bisacridinium nitrate (BNMA) was assembled with exfoliated layered α-zirconium phosphate (α-ZrP) via an electrostatic layer-by-layer (LBL) assembly method. As a result, the luminescent films which were well-aligned and periodical had been successfully fabricated. Surprisingly, the lifetimes of (BNMA/ZrP) n were found to be prolonged by 16-fold for the first time, due to the isolation effect of inorganic nanosheets and hydrogen ion migration between the interlayers. Therefore, it is testified that α-ZrP can be used as the laminate and has remarkable influences on enhancing the lifetimes of chromophores. We expect that this new discovered effect can enable α-ZrP a kind of new potential material to develop novel light-emitting materials and optical devices. [ABSTRACT FROM AUTHOR]

Ultrathin transition metal oxide films exhibit unique physical and chemical properties not observed for the corresponding bulk oxides. These properties, originating mainly from the limited thickness and the interaction with the support, make those films similar to other supported 2D materials with bulk counterparts, such as transition metal dichalcogenides. Ultrathin iron oxide (FeO) films, for example, were shown to exhibit unique electronic, catalytic and magnetic properties that depend on the type of the used support. Ag(111) has always been considered a promising substrate for FeO growth, as it has the same surface symmetry, only ~5% lattice mismatch, is considered to be weakly-interacting and relatively resistant to oxidation. The reports on the growth and structure of ultrathin FeO films on Ag(111) are scarce and often contradictory to each other. We attempted to shed more light on this system by growing the films using different preparation procedures and studying their structure using scanning tunneling microscopy (STM), low energy electron diffraction (LEED) and X-ray photoelectron spectroscopy (XPS). We observed the formation of a previously unreported Moiré superstructure with 45 Å periodicity, as well as other reconstructed and reconstruction-free surface species. The experimental results obtained by us and other groups indicate that the structure of FeO films on this particular support critically depends on the films’ preparation conditions. We also performed density functional theory (DFT) calculations on the structure and properties of a conceptual reconstruction-free FeO film on Ag(111). The results indicate that such a film, if successfully grown, should exhibit tunable thickness-dependent properties, being substrate-influenced in the monolayer regime and free-standing-FeO-like when in the bilayer form.

Iron oxide films epitaxially grown on close-packed metal single crystal substrates exhibit nearly-perfect structural order, high catalytic activity (FeO) and room-temperature magnetism (Fe3O4). However, the morphology of the films, especially in the ultrathin regime, can be significantly influenced by the crystalline structure of the used support. This work reports an ultra-high vacuum (UHV) low energy electron/synchrotron light-based X-ray photoemission electron microscopy (LEEM/XPEEM) and electron diffraction (µLEED) study of the growth of FeO and Fe3O4 on two closed-packed metal single crystal surfaces: Pt(111) and Ru(0001). The results reveal the influence of the mutual orientation of adjacent substrate terraces on the morphology of iron oxide films epitaxially grown on top of them. On fcc Pt(111), which has the same mutual orientation of adjacent monoatomic terraces, FeO(111) grows with the same in-plane orientation on all substrate terraces. For Fe3O4(111), one or two orientations are observed depending on the growth conditions. On hcp Ru(0001), the adjacent terraces of which are ‘rotated’ by 180° with respect to each other, the in-plane orientation of initial FeO(111) and Fe3O4(111) crystallites is determined by the orientation of the substrate terrace on which they nucleated. The adaptation of three-fold symmetric iron oxides to three-fold symmetric substrate terraces leads to natural structuring of iron oxide films, i.e., the formation of patch-like magnetite layers on Pt(111) and stripe-like FeO and Fe3O4 structures on Ru(0001).

A potential approach to enhance the suppressed proton conductivity of nanoscale ultrathin Nafion films is to adjust the ionomer structure via regulating the catalyst-ionomer interaction. To understand the interaction between substrate surface charges and Nafion molecules, self-assembled ultrathin films (∼20 nm) were prepared on the SiO 2 model substrates, which were modified with silane coupling agents to carry either negative (COO - ) or positive (NH 3 ) charges. Specifically, the surface energy, phase separation, and proton conductivity were investigated by contact angle measurements, atomic force microscopy, and microelectrodes to illuminate the relationship between the substrate surface charge, thin-film nanostructure, and proton conduction. Compared to electrically neutral substrates, ultrathin films formed faster on the negatively charged substrate with an 83% increase in proton conductivity but formed more slowly on the positively charged substrate, with proton conductivity decreased by 35% at 50 °C. The surface charges interact with sulfonic acid groups of Nafion molecules to alter molecular orientation, resulting in different surface energies and phase separation, which are responsible for proton conductivity variation.+ ) charges. Specifically, the surface energy, phase separation, and proton conductivity were investigated by contact angle measurements, atomic force microscopy, and microelectrodes to illuminate the relationship between the substrate surface charge, thin-film nanostructure, and proton conduction. Compared to electrically neutral substrates, ultrathin films formed faster on the negatively charged substrate with an 83% increase in proton conductivity but formed more slowly on the positively charged substrate, with proton conductivity decreased by 35% at 50 °C. The surface charges interact with sulfonic acid groups of Nafion molecules to alter molecular orientation, resulting in different surface energies and phase separation, which are responsible for proton conductivity variation.

[Display omitted] • PtSe 2 films with the different crystallographic orientations of the c-axis were prepared. • Tribological properties of the PtSe 2 films were investigated. • The friction forces and adhesion are affected by the crystal quality rather than crystallographic orientation. • The coefficient of friction decreases for films with horizontally aligned flakes. Two-dimensional (2D) transition metal dichalcogenides are potential candidates for ultrathin solid-state lubricants in low-dimensional systems owing to their flatness, high in-plane mechanical strength, and low shear interlayer strength. Yet, the effects of surface topography and surface chemistry on the tribological properties of 2D layers are still unclear. In this work, we performed a comparative investigation of nanoscale tribological properties of ultra-thin highly-ordered PtSe 2 layers deposited on the sapphire substrates with the in-plane and out-of-plane crystallographic orientation of the PtSe 2 c -axis flakes, and epitaxial PtSe 2 layers. PtSe 2 c -axis orientation was found to has an impact on the nanotribological, morphological and electrical properties of PtSe 2 , in particular the change in the alignment of the PtSe 2 flakes from vertical (VA) to horizontal (HA) led to the lowering of the coefficient of friction from 0.21 to 0.16. This observation was accompanied by an increase in the root-mean-square surface roughness from 1.0 to 1.7 nm for the HA and VA films, respectively. The epitaxial films showed lower friction caused by lowering adhesion when compared to other investigated films, whereas the friction coefficient was similar to films with HA flakes. The observed trends in nanoscale friction is attributed to a different distribution of PtSe 2 structure. [ABSTRACT FROM AUTHOR]

Spin-polarized scanning tunneling microscopy is used to investigate the magnetic state of the Fe monolayer on Re(0001). Two coexisting atomic-scale noncollinear spin textures are observed with a sharp transition between them on the order of the atomic lattice spacing. A position correlation between the two spin states is observed both in experiments and in Monte Carlo simulations, demonstrating their coupling behavior. [ABSTRACT FROM AUTHOR]

We present the observation of transverse thermopower , or planar Nernst Effect (PNE), and planar Hall Effect (PHE) in patterned ultrathin film (∼8 nm) of La 0.7 Sr 0.3 MnO 3 (LSMO). For PNE, a heat current was applied in-plane of the film (by creating a temperature gradient ∇T) whereas an in-plane current of 100 μA was applied for measuring PHE. Even for a temperature difference of ΔT = 5 K the planar Nernst effect in LCMO ultrathin film (∼8 nm) shows a coercivity of ∼3 Oe and confirms the ferromagnetic nature of the thin film. The angular dependence of transverse voltage in PNE shows a four-fold sinθ cosθ dependence symmetry at 250 K, which is consistent with the planar Hall effect measurement. [ABSTRACT FROM AUTHOR]

ABSTRACT Manipulation of optical transmission using plasmonic nanostructures is a significant issue in applications related to ultra-compact optoelectronic devices. In this paper, we present a type of plasmonic frequency selective surface constructed with an ultrathin gold film (∼20 nm) with arrays of subwavelength holes. By means of modified nanosphere lithography, we fabricate the nanostructured gold films with scalable sizes and tunable transmission in the visible and near-infrared range. Moreover, electromagnetic simulations are performed and demonstrate good agreement with experimental results and further reveal the evolution of optical properties from the optically thick film to the ultrathin film. The research achievements will provide significant design guidance of ultrathin plasmonic frequency selective surface for future nanophotonic devices. © 2016 Wiley Periodicals, Inc. Microwave Opt Technol Lett 58:2171-2176, 2016 [ABSTRACT FROM AUTHOR]

We use short wavelength extreme ultraviolet light to independently measure the mechanical properties of disparate layers within a bilayer film for the first time, with single-monolayer sensitivity. We show that in Ni/Ta nanostructured systems, while their density ratio is not meaningfully changed from that expected in bulk, their elastic properties are significantly modified, where nickel softens while tantalum stiffens, relative to their bulk counterparts. In particular, the presence or absence of the Ta capping layer influences the mechanical properties of the Ni film. This nondestructive nanomechanical measurement technique represents the first approach to date able to distinguish the properties of composite materials well below 100 nm in thickness. This capability is critical for understanding and optimizing the strength, flexibility and reliability of materials in a host of nanostructured electronic, photovoltaic, and thermoelectric devices. [ABSTRACT FROM AUTHOR]

Abstract: Healable films with structural color are highly desirable and have a variety of potential applications. However, combining structural color with self‐healing properties to obtain new functional materials is a big challenge in current research. Herein, we present the first example of a color tunable, ultrathin film that can self‐heal in response to external mechanical abrasion. It is designed based on intermolecular hydrogen bonding interaction; the synthetic strategy involves spin‐coating of poly(acrylic acid) (PAA) and chitosan (CS). The successful preparation of ultrathin, healable, structural color films provides a new type of biomimetic material. [ABSTRACT FROM AUTHOR]

The device physics of CdS/CdTe Ultrathin Film solar cells (UTF-SCs) is modeled using Sah–Noyce–Shockley (SNS) theory for the generation/recombination in the Space Charge Region (SCR) of an asymmetric pn + junction. This theory is based on Shockley–Read–Hall (SRH) recombination mechanism related to midgap defects in the band gap. The maximum effect of SRH is within SCR where the carriers are mainly collected by the electric field. Since the depletion width in a UTF extends to the back region, a UTF resembles an asymmetric pn + junction, which is most commonly modelled by SNS theory. Several materials and electrical parameters dominate the device physics of a fully depleted CdTe layer with d CdTe ⩽ 1 μm. The uncompensated defect density, recombination lifetime, and CdTe thickness are parameters which effectively control the current–voltage characteristics and quantum efficiency of UTF devices. Simulation results indicate that any parameter that narrows the SCR of a UTF will reduce the open-circuit voltage whereas only thinning the CdTe layer lowers the short-circuit current density. The electrical resistivity and quantum efficiency are a measure of defect density/level and d CdTe or band bending at the junction, respectively. A practical takeaway of our simulation results is to measure the electrical resistivity of the CdTe layer before metallization of UTF solar cells. Band bending is a measure of junction quality. The latter parameters are usually ignored in device fabrication and modeling. However, any parameter related to defect density in UTF devices must be considered in the modeling since the front and back contacts are closer here and the degradation rate is rather probable. The degradation of UTF devices based on carrier collection mechanisms dominated by drift component is briefly discussed. [ABSTRACT FROM AUTHOR]

Large-scale production of reliable carbon nanotubes (CNTs) based gas sensors involves the development of scalable and reliable processes for the fabrication of films with controlled morphology. Here, we report for the first time on highly scalable, ultrathin CNT films, to be employed as conductometric sensors for NO 2 and NH 3 detection at room temperature. The sensing films are produced by dip coating using dissolved CNTs in chlorosulfonic acid as a working solution. This surfactant-free approach does not require any post-treatment for the removal of dispersants or any CNTs functionalization, thus promising high quality CNTs for better sensitivity and low production costs. The effect of CNT film thickness and defect density on the gas sensing properties has been investigated. Detection limits of 1 ppm for NO 2 and 7 ppm for NH 3 have been achieved at room temperature. The experimental results reveal that defect density and film thickness can be controlled to optimize the sensing response. Gas desorption has been accelerated by continuous in-situ UV irradiation. [ABSTRACT FROM AUTHOR]

Surface-active polymers that display nonfouling properties and carry binding groups that can adsorb onto different substrates are highly desirable. We present a postmodification protocol of an active-ester-containing polymer that allows the creation of such a versatile platform. Poly(pentafluorophenyl acrylate) has been postmodified with a fixed grafting ratio of a nonfouling function (mPEG) and various combinations of functional groups, such as amine, silane and catechol, which can provide strong affinity to two model substrates: SiO2 and TiO2. Adsorption, stability and resistance to nonspecific protein adsorption of the polymer films were studied. A polymer was obtained that maintained its surface functionality under a variety of harsh conditions. EG surface-density calculations show that this strategy generates a denser packing when both negatively and positively charged groups are present within the backbone, and readily allows the fabrication of a broad combinatorial matrix. [ABSTRACT FROM AUTHOR]

In this paper, isothermal crystallization at different temperatures and multiple melting of four molecular weights ( MW ) PCL ultrathin films were investigated by using Atomic Force Microscopy (AFM). The results showed that: two different crystal structures, Flat-on and Edge-on lamellae, were simultaneously formed in PCL ultrathin films when the T c lower than 30 °C. During the heating process, Edge-on lamellae was melted firstly. This demonstrated that the multiple melting behavior of PCL in ultrathin films was caused by the two different lamellar structures. With the increase of MW , or with the decrease of T c , PCL chains in ultrathin films changed from Flat-on to Edge-on, and the controlled factors of growth process in ultrathin films transformed from surface nucleation-limited (NL) to melt diffusion-limited (DL). [ABSTRACT FROM AUTHOR]

Ultrathin films of thicknesses below 100 nm are now considered in different areas of applications. Their behavior in term of kinetics of crystallization is very different from that of bulk samples due to the film confinement in two-dimensions, and their morphologies are unique. In this review, recent advances in the crystallization of ultrathin films of homopolymers and miscible polymer blends will be described, with an emphasis on morphologies and, in the case of blends, on mixtures made of two crystalline polymers. [ABSTRACT FROM AUTHOR]

The characterization of nanosize SOI materials and devices is challenging because multiple oxides, interfaces and channels coexist. Conventional measurement methods need to be replaced, or at least updated. We review the routine techniques that proved efficient for the evaluation of bare SOI wafers (essentially the pseudo-MOSFET) and of MOS structures (transistors and gated diodes). Informative examples are selected to illustrate the typical properties of advanced SOI wafers and MOSFETs. We will show how the ultrathin film and short-channel effects affect the interpretation of the experimental data. [ABSTRACT FROM AUTHOR]

There are increasing requirements for highly efficient and solvent-resistant nanoporous membranes in various separation processes. Traditional membranes usually have a poor solvent resistance and a thick skin layer leading to a low permeation flux. Currently, the major challenge lies in fabrication of ultrathin few-nanometers-pore membranes for fast organic filtration. Herein, a facile approach is presented to prepare ultrafine cellulose nanofibers for fabrication of ultrathin nanoporous membranes. The obtained nanofibers have a uniform diameter of 7.5 ± 2.5 nm and are homogeneously dispersed in aqueous solutions that are favorable to the fabrication of ultrathin nanoporous membranes. The resulting cellulose nanoporous membranes have an adjustable thickness down to 23 nm and pore sizes ranging from 2.5 to 12 nm. They allow fast permeation of water and organics during pressure-driven filtration. Typically, the 30 nm thick membrane has high fluxes of 1.14 and 3.96 × 104 L h−1 m−2 bar−1 for pure water and acetone respectively. Furthermore, the as-prepared cellulose nanofibers are easily employed to produce a novel syringe filter with sub-10 nm pores that have a wide application in fast separation and purification of nanoparticles on few-nanometers scale. [ABSTRACT FROM AUTHOR]

Simultaneously synthesizing and structuring atomically thick or ultrathin 2D non-precious metal nanocrystal may offer a new class of materials to replace the state-of-art noblemetal electrocatalysts; however, the synthetic strategy is the bottleneck which should be urgently solved. Here we report the synthesis of an ultrathin nickel nanosheet array (Ni-NSA) through in situ topotactic reduction from Ni(OH)2 array precursors. The Ni nanosheets showed a single-crystalline lamellar structure with only ten atomic layers in thickness and an exposed (111) facet. Combined with a superaerophobic (low bubble adhesive) arrayed structure the Ni-NSAs exhibited a dramatic enhancement on both activity and stability towards the hydrazine-oxidation reaction (HzOR) relative to platinum. Furthermore, the partial oxidization of Ni-NSAs in ambient atmosphere resulted in effective water-splitting electrocatalysts for the hydrogen-evolution reaction (HER). [ABSTRACT FROM AUTHOR]

While the mechanical properties of ultrathin polymer films have been extensively studied, only few studies have focused on the ultrathin block copolymer films with complex topologies. The structure-property relationship of ultrathin films (thickness = 35–1000 nm) of polystyrene- b -polyisoprene- b -polystyrene (SIS) containing 14 wt% polystyrene (PS) is established in this study. Grazing-incidence small-angle X-ray scattering, dynamic secondary ion mass spectrometry, and atomic force microscopy were used to characterize the film structure. The difference in surface energy and interfacial energy of the domains resulted in the SIS thin films to primarily consist of three layers: a PS-rich subsurface layer (30 wt%), a spherical PS bulk layer (14 wt%), and a PS-rich interface layer (20 wt%). The film-on-water tensile test was used to investigate both the film thickness and strain rate dependences of mechanical properties. We found that the Young's modulus increased dramatically as film thickness decreased, although only few PS-rich layers consisting of disperse cylindrical and spherical PS domains existed at the surface and interface. Furthermore, the strain rate dependence of the modulus and stress relaxation was more significant for thinner films than for thicker films. The increase in modulus and unusual relaxation behavior are hypothesized to be the result of a combination of different factors, including PS domain alignment, confinement effects, and surface and interface interactions. [Display omitted] • The structure-property relationship of ultrathin SIS films is analyzed. • Young's modulus increases upon decreasing thickness. • The extent of stress relaxation is larger for thinner films. • The stiffening may result from PS domain alignment. [ABSTRACT FROM AUTHOR]

• A molecular layer made of face-on and/or edge-on molecules on top of the edge-on organic terraces is identified in sub-monolayer organic films. • Standard and advanced Scanning Probe Microscopy techniques, operating in different environments, have confirmed such additional molecular layer. • In situ and ex situ morphological and height measurements highlight a transition from a standard to non-standard growth mechanism in sub-monolayer films. • Topographic data, recorded in air and vacuum, prove that the water layer always present in air does not affect the height measurement. The morphology of sub-monolayer sexithiophene films has been investigated in situ and ex situ as a function of the substrate temperature of deposition. In this thickness range, monolayer terraces formed of edge-on molecules, i.e. nearly upright, are typically nucleated. Herein, the terrace height is found to be correlated to both the film morphology and the substrate surface energy. In particular, the presence of a layer of variable thickness with molecules lying face-on or side-on can be identified atop the terraces when the deposition is carried out on inert substrates. This phenomenon can be evidenced thanks to accurate height measurements made with atomic force microscopy and further data obtained with advanced scanning probe microscopy techniques operating in different environments, viz. liquid, air and vacuum. An upward displacement of molecules from the substrate to the top of the terraces is considered to be responsible of this layer formation, whose molecules weakly interact with the underlying terraces. [ABSTRACT FROM AUTHOR]

• Epitaxial layered stacks Pt/W(d W)/Co(d Co)/Pt were grown by MBE. • Magnetic anisotropy strongly depends on W layer thickness d W. • The presence of Dzyaloshinskii Morya interaction was proved by BLS. • Bubble-like domain structure with micrometer range diameter was observed. We discuss the magnetic properties of epitaxial Pt/W(d W)/Co(d Co)/Pt layered films as a function of W(d W) and Co(d Co) layer thicknesses. The samples were investigated by means of: (i) polar magnetooptical Kerr effect based magnetometry and microscopy as well as (ii) Brillouin light scattering (BLS) spectrometry. The bottom W layer exhibits a strong influence on the magnetic anisotropy, d Co -dependent spin reorientation transition and magnetic polarization of atoms forming the interfaces. The areas with (i) in-plane, (ii) out-of-plane, (iii) superparamagnetic with out-of-plane anisotropy, and (iv) nonmagnetic states appear with d Co decrease. The d W driven transition from hard to soft magnetic material with out-of-plane magnetization was found. The observed domain structures (micrometer range bubbles, stripes and dendritic-like) at out-of-plane state are very sensitive to d Co , d W thicknesses and external magnetic field. The presence of Dzyaloshinskii-Moriya interaction was deduced from BLS measurements. [ABSTRACT FROM AUTHOR]

Microscopy and diffraction measurements are presented of ultrathin binary alloy films of ruthenium and molybdenum that are obtained by standard sputter deposition. For compositions close to Ru 50 Mo 50 , we find the films to be amorphous. The amorphicity of the films is accompanied by a significant reduction of the roughness with respect to the roughness of equally thick films of either ruthenium or molybdenum. We ascribe this to the absence of the grain structure that is characteristic of the polycrystalline films of the separate elements. [Display omitted] • Amorphous, thin alloy films of ruthenium and molybdenum can be produced by simultaneous sputter deposition. • Surfaces of thin amorphous RuMo films are extremely smooth. • Grain boundaries make regular, polycrystalline Ru or Mo films rougher than films of their amorphous mixture. [ABSTRACT FROM AUTHOR]

The self-assembly technique is a powerful tool to fabricate ultrathin films from organic compounds aiming at technological applications in molecular electronics. This relatively new approach allows molecularly flat films to be obtained on a simple and cheap fashion from various types of material, including polyelectrolytes, conducting polymers, dyes and proteins. The resulting multilayer films may be fabricated according to specific requirements since their structural and physical properties may be controlled at the molecular level. In this review we shall comment upon the evolution of preparation methods for ultrathin films, the process of adsorption and their main properties, as well as some examples of technological applications of layer-by-layer or self-assembled films.

Perfect absorption and strong coupling are two highly sought-after regimes of light-matter interactions. Both regimes have been studied as separate phenomena in excitonic 2D materials, particularly in MoS 2 . However, the structures used to reach these regimes often require intricate nanofabrication. Here, we demonstrate the occurrence of perfect absorption and strong coupling in thin MoS 2 multilayers supported by a glass substrate. We measure reflection spectra of mechanically exfoliated MoS 2 flakes at various angles beyond the light-line via Fourier plane imaging and spectroscopy and find that absorption in MoS 2 monolayers increases up to 74% at the C-exciton by illuminating at the critical angle. Perfect absorption is achieved for ultrathin MoS 2 flakes (4-8 layers) with a notable angle and frequency sensitivity to the exact number of layers. By calculating zeros and poles of the scattering matrix in the complex frequency plane, we identify perfect absorption (zeros) and strong coupling (poles) conditions for thin (<10 layers) and thick (>10 layers) limits. Our findings reveal rich physics of light-matter interactions in bare MoS 2 flakes, which could be useful for nanophotonic and light harvesting applications.

Co/CoO multilayers are fabricated by means of radio-frequency magnetron sputtering. For the formation of each multilayer period, a Co layer is initially produced followed by natural oxidation. Platinum is used not only as buffer and capping layers, but also in the form of intermediate ultrathin layers to enhance perpendicular magnetic anisotropy. Three samples are compared with respect to the magnetic anisotropies and exchange bias between 4-300 K based on superconducting quantum interference device magnetometry measurements. Two of the multilayers are identical Co/CoO/Pt ones; one of them, however, is grown on a Co/Pt "magnetic substrate" to induce perpendicular magnetic anisotropy via exchange coupling through an ultrathin Pt intermediate layer. The third multilayer is of the form Co/CoO/Co/Pt. The use of a "magnetic substrate" results in the observation of loops with large remanence when the field applies perpendicular to the film plane. The CoO/Co interfaces lead to a significant exchange bias at low temperatures after field cooling. The largest exchange bias was observed in the film with double Co/CoO/Co interfaces. Consequently, significant perpendicular anisotropy coexists with large exchange bias, especially at low temperatures. Such samples can be potentially useful for applications related to spintronics and magnetic storage.

Super broadband optical absorbers with ultrathin films have been keenly pursued for a long time. Although highly lossy materials with sharp light attenuation have the potential to become super absorbers, a large percent of light from free space is inevitably reflected back for the distinct impedance mismatch. Here, a simple strategy, of which reducing the thickness of highly-lossy thin films to minish reflectance and simultaneously folding the ultrathin films to make light multiple pass through, is proposed to obtain super broadband mid-infrared absorbers with ultrathin films. Along this line, the absorbers were prepared by depositing Al-doped ZnO film on scaffolds consisted of alumina spherical shells, whose substrates were opaque. When the thickness of Al-doped ZnO is 43 nm and the layer number of scaffolds is three, a maximum average absorptance was achieved as 97.6% over the wavelength range from 3 to 15 μm. Applying this strategy on polished Al foil, excellent infrared camouflage performance on human-body background was demonstrated. Featured by the strong broadband optical absorption with ultrathin films, flexible access to multiple substrates and low-cost procedures, this approach has the potential in widespread applications of infrared thermal emitters and optoelectronic devices., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2022 Elsevier Inc. All rights reserved.)