Showing papers on "Substrate (electronics) published in 2019"
TL;DR: This review links metal halide perovskites' performance as efficient light emitters with their underlying materials electronic and photophysical attributes.
Abstract: Next-generation displays and lighting technologies require efficient optical sources that combine brightness, color purity, stability, substrate flexibility. Metal halide perovskites have potential use in a wide range of applications, for they possess excellent charge transport, bandgap tunability and, in the most promising recent optical source materials, intense and efficient luminescence. This review links metal halide perovskites' performance as efficient light emitters with their underlying materials electronic and photophysical attributes.
542 citations
TL;DR: It is found that freestanding BiFeO3 films exhibit unexpected and giant tetragonality and polarization when approaching the 2D limit, and the absence of a critical thickness for stabilizing the crystalline order in thefreestanding ultrathin oxide films is demonstrated.
Abstract: Two-dimensional (2D) materials such as graphene and transition-metal dichalcogenides reveal the electronic phases that emerge when a bulk crystal is reduced to a monolayer1-4. Transition-metal oxide perovskites host a variety of correlated electronic phases5-12, so similar behaviour in monolayer materials based on transition-metal oxide perovskites would open the door to a rich spectrum of exotic 2D correlated phases that have not yet been explored. Here we report the fabrication of freestanding perovskite films with high crystalline quality almost down to a single unit cell. Using a recently developed method based on water-soluble Sr3Al2O6 as the sacrificial buffer layer13,14 we synthesize freestanding SrTiO3 and BiFeO3 ultrathin films by reactive molecular beam epitaxy and transfer them to diverse substrates, in particular crystalline silicon wafers and holey carbon films. We find that freestanding BiFeO3 films exhibit unexpected and giant tetragonality and polarization when approaching the 2D limit. Our results demonstrate the absence of a critical thickness for stabilizing the crystalline order in the freestanding ultrathin oxide films. The ability to synthesize and transfer crystalline freestanding perovskite films without any thickness limitation onto any desired substrate creates opportunities for research into 2D correlated phases and interfacial phenomena that have not previously been technically possible.
344 citations
TL;DR: In this article, it was shown that the infrared reflection losses in tandem cells processed on a flat silicon substrate can be significantly reduced by using an optical interlayer consisting of nanocrystalline silicon oxide.
Abstract: Perovskite/silicon tandem solar cells are attractive for their potential for boosting cell efficiency beyond the crystalline silicon (Si) single-junction limit. However, the relatively large optical refractive index of Si, in comparison to that of transparent conducting oxides and perovskite absorber layers, results in significant reflection losses at the internal junction between the cells in monolithic (two-terminal) devices. Therefore, light management is crucial to improve photocurrent absorption in the Si bottom cell. Here it is shown that the infrared reflection losses in tandem cells processed on a flat silicon substrate can be significantly reduced by using an optical interlayer consisting of nanocrystalline silicon oxide. It is demonstrated that 110 nm thick interlayers with a refractive index of 2.6 (at 800 nm) result in 1.4 mA cm − ² current gain in the silicon bottom cell. Under AM1.5G irradiation, the champion 1 cm 2 perovskite/silicon monolithic tandem cell exhibits a top cell + bottom cell total current density of 38.7 mA cm −2 and a certified stabilized power conversion efficiency of 25.2%.
224 citations
TL;DR: The high performance of the phototransistor shown here together with the developed unique transfer technique are promising for the development of novel 2D-material-based optoelectronic applications as well as integrating with state-of-the-art silicon photonic and electronic technologies.
Abstract: 2D materials are considered as intriguing building blocks for next-generation optoelectronic devices. However, their photoresponse performance still needs to be improved for practical applications. Here, ultrasensitive 2D phototransistors are reported employing chemical vapor deposition (CVD)-grown 2D Bi2 O2 Se transferred onto silicon substrates with a noncorrosive transfer method. The as-transferred Bi2 O2 Se preserves high quality in contrast to the serious quality degradation in hydrofluoric-acid-assisted transfer. The phototransistors show a responsivity of 3.5 × 104 A W-1 , a photoconductive gain of more than 104 , and a time response in the order of sub-millisecond. With back gating of the silicon substrate, the dark current can be reduced to several pA. This yields an ultrahigh sensitivity with a specific detectivity of 9.0 × 1013 Jones, which is one of the highest values among 2D material photodetectors and two orders of magnitude higher than that of other CVD-grown 2D materials. The high performance of the phototransistor shown here together with the developed unique transfer technique are promising for the development of novel 2D-material-based optoelectronic applications as well as integrating with state-of-the-art silicon photonic and electronic technologies.
171 citations
TL;DR: In this article, the properties of Er3+-doped gallium lanthanum sulphide thin films were studied as a function of process temperature, showing that by increasing the substrate temperature, the deposited layer thickness increases and the crystallinity of the films changes.
Abstract: The properties of Er3+-doped gallium lanthanum sulphide thin films prepared on a silicon substrate by femtosecond pulsed laser deposition were studied as a function of process temperature. The films were characterised using transition electron microscopy imaging, X-ray diffractometry, Raman spectroscopy, fluorescence spectroscopy, and UV–Vis–NIR spectroscopy. The results show that by increasing the substrate temperature, the deposited layer thickness increases and the crystallinity of the films changes. The room temperature photoluminescence and lifetimes of the 4I13/2→4I15/2 transition of Er3+ are reported in the paper.
138 citations
TL;DR: The electrochromic property and device construction of a triphenylamine-based oriented two-dimensional cova-lent organic framework (2D COF) films on the indium tin oxide (ITO) was reported and it exhibited moderate performance and stability in the near-infrared region.
Abstract: The electrochromic property and device construction of a triphenylamine-based oriented two-dimensional covalent organic framework (2D COF) film on indium tin oxide (ITO) coated glass was reported. The characterization of the 2D COF3PA-TT film revealed that the film was uniform, with good crystallinity, and oriented with its 2D plane parallel to the substrate. For the first time, the electrochromic properties of 2D COF3PA-TT film were studied. 2D COF3PA-TT film on ITO exhibited reversible color transition between deep red and dark brown during redox process. Spectroelectrochemical experiments revealed color changes in the absorption spectra of 2D COF3PA-TT film in the visible and near-infrared regions and showed the characteristics of intervalence charge transfer. The quasi-solid-state electrochromic device was prepared based on the COF3PA-TT film, and it exhibited moderate performance and stability in the near-infrared region.
122 citations
25 Nov 2019
TL;DR: In this article, the authors show that twisted bilayer graphene hosts narrow Chern bands if aligned with hBN substrate, which give rise to quantum anomalous effects through quantum Hall ferromagnetism.
Abstract: Recently quantum anomalous effects were observed in twisted bilayer graphene. This paper shows that twisted bilayer graphene hosts narrow Chern bands if aligned with hBN substrate, which give rise to quantum anomalous effects through quantum Hall ferromagnetism
120 citations
TL;DR: It is shown that epitaxial films of inorganic materials such as cesium lead bromide (CsPbBr3), lead(II) iodide (PbI2), zinc oxide (ZnO), and sodium chloride (NaCl) can be deposited onto a variety of single-crystal and single- Crystalline substrates by simply spin coating either solutions of the material or precursors to the material.
Abstract: Spin-coated films, such as photoresists for lithography or perovskite films for solar cells, are either amorphous or polycrystalline. We show that epitaxial films of inorganic materials such as cesium lead bromide (CsPbBr3), lead(II) iodide (PbI2), zinc oxide (ZnO), and sodium chloride (NaCl) can be deposited onto a variety of single-crystal and single-crystal-like substrates by simply spin coating either solutions of the material or precursors to the material. The out-of-plane and in-plane orientations of the spin-coated films are determined by the substrate. The thin stagnant layer of supersaturated solution produced during spin coating promotes heterogeneous nucleation of the material onto the single-crystal substrate over homogeneous nucleation in the bulk solution, and ordered anion adlayers may lower the activation energy for nucleation on the surface. The method can be used to produce functional materials such as inorganic semiconductors or to deposit water-soluble materials such as NaCl that can serve as growth templates.
117 citations
TL;DR: In this article, a gear-like triboelectric nanogenerator (TENG) was designed for self-powered sensing, which can reflect the change in the state of human touch through electric signals and respond to the changes in small forces caused by water drop and vibration in the substrate.
117 citations
TL;DR: Guo et al. as mentioned in this paper used the seed screening model to control the orientation of 1D crystal-structural Sb2 Se3 solar cells on an inert TiO2 substrate.
Abstract: The orientation of low-dimensional crystal-structural (LDCS) films significantly affects the performance of photoelectric devices, particularly in vertical conducting devices such as solar cells and light-emitting diodes. According to film growth theory, the initial seeds determine the final orientation of the film. Ruled by the minimum energy principle, lying (chains or layers parallel to the substrate) seeds bonding with the substrate through van der Waals forces are easier to form than standing (chains or layers perpendicular to the substrate) seeds bonding with the substrate by a covalent bond. Utilizing high substrate temperature to re-evaporate the lying seeds and preserve the standing seeds, the orientation of 1D crystal-structural Sb2 Se3 is successfully controlled. Guided by this seed screening model, highly [211]- and [221]-oriented Sb2 Se3 films on an inert TiO2 substrate are obtained; consequently, a record efficiency of 7.62% in TiO2 /Sb2 Se3 solar cells is achieved. This universal model of seed screening provides an effective method for orientation control of other LDCS films.
103 citations
04 Jan 2019
TL;DR: In this article, a combination of X-ray crystal truncation rod analysis and ab initio molecular dynamics was used to probe the pre-nucleation liquid layering at the sapphire-aluminium solid/liquid interface.
Abstract: Liquid layering at heterogeneous solid/liquid interfaces is a general phenomenon, which provides structural templates for nucleation of crystalline phases on potent nucleants. However, its efficacy near poor nucleants is incompletely understood. Here we use a combination of X-ray crystal truncation rod analysis and ab initio molecular dynamics to probe the pre-nucleation liquid layering at the sapphire–aluminium solid/liquid interface. At the sapphire side, a ~1.6 aluminium-terminated structure develops, and at the liquid side, two pre-nucleation layers emerge at 950 K. No more pre-nucleation layer forms with decreasing temperature indicating that nucleation of crystalline aluminium through layer-by-layer atomic adsorption of liquid atoms is not favoured. Instead, the appearance of stochastically-formed nuclei near the substrate is supported by our experiments. Nucleation on poor nucleants is dominated by the stochastic nucleation events which are substantially influenced by the pre-nucleation layers that determine the surface structure in contact with the nuclei. Liquid layering at heterogeneous surfaces is a general phenomenon but is poorly understood. Here the authors probe pre-nucleation liquid layering at the sapphire–Al solid/liquid interface using a combination of in situ X-ray crystal truncation rod analysis and ab-initio molecular dynamics simulations.
TL;DR: In this paper, the effect of processing parameters in directed energy deposition (DED) additive manufacturing (AM) on the microstructure and mechanical properties of Ti-6Al-4V was evaluated.
TL;DR: In this article, the authors describe room-temperature photoluminescence (PL) emitters that naturally occur whenever monolayer transition metal dichalcogenides (TMDCs) is deposited on an atomically flat substrate.
Abstract: The possibility to tailor photoluminescence (PL) of monolayer transition metal dichalcogenides (TMDCs) using external factors such as strain, doping, and external environment is of significant interest for optoelectronic applications. Strain in particular can be exploited as a means to continuously vary the band gap. Micrometer-scale strain gradients were proposed for creating “artificial atoms” that can utilize the so-called exciton funneling effect and work, for example, as exciton condensers. Here we describe room-temperature PL emitters that naturally occur whenever monolayer TMDC is deposited on an atomically flat substrate. These are hydrocarbon-filled bubbles, which provide predictable, localized PL from well-separated sub-micrometer areas. Their emission energy is determined by the built-in strain controlled only by the substrate material, such that both the maximum strain and the strain profile are universal for all bubbles on a given substrate, i.e., independent of the bubble size. We show that ...
TL;DR: In this paper, the material properties of Pb(Zr,Ti)O3 (PZT) thin film with a LaNiO3 buffer layer on an ultra-thin Ni-Cr-based austenitic steel metal foil substrate are systematically investigated for flexible piezoelectric vibrational energy harvesting device applications.
01 Feb 2019
TL;DR: In this article, the dielectric-dependent electronic bandgap can be used to engineer a lateral heterojunction within a homogeneous molybdenum disulfide monolayer.
Abstract: Owing to their low dimensionality, two-dimensional semiconductors, such as monolayer molybdenum disulfide, have a range of properties that make them valuable in the development of nanoelectronics. For example, the electronic bandgap of these semiconductors is not an intrinsic physical parameter and can be engineered by manipulating the dielectric environment around the monolayer. Here we show that this dielectric-dependent electronic bandgap can be used to engineer a lateral heterojunction within a homogeneous MoS2 monolayer. We visualize the heterostructure with Kelvin probe force microscopy and examine its influence on electrical transport experimentally and theoretically. We observe a lateral heterojunction with an approximately 90 meV band offset due to the differing degrees of bandgap renormalization of monolayer MoS2 when it is placed on a substrate in which one segment is made from an amorphous fluoropolymer (Cytop) and another segment is made of hexagonal boron nitride. This heterostructure leads to a diode-like electrical transport with a strong asymmetric behaviour. A lateral heterojunction with diode-like electrical transport can be created in a homogeneous MoS2 monolayer by using a substrate in which one segment is made from an amorphous fluoropolymer and another segment from hexagonal boron nitride.
TL;DR: In this article, the structural quality of the orthorhombic Ga2O3 thin film was studied based on the growth parameters employing X-ray diffraction 2θ-ω scans, rocking curves, ϕ scans, and reciprocal space maps.
Abstract: High-quality Ga2O3 thin films in the orthorhombic κ-phase are grown by pulsed-laser deposition using a tin containing target on c-sapphire, MgO(111), SrTiO3(111), and yttria-stabilized ZrO2(111) substrates. The structural quality of the layers is studied based on the growth parameters employing X-ray diffraction 2θ-ω scans, rocking curves, ϕ scans, and reciprocal space maps. Our layers exhibit superior crystalline properties in comparison to thin films deposited in the monoclinic β-phase at nominally identical growth parameters. Furthermore, the surface morphology is significantly improved and the root-mean-squared roughness of the layers was as low as ≈0.5 nm, on par with homoepitaxial β-Ga2O3 thin films in the literature. The orthorhombic structure of the thin films was evidenced, and the epitaxial relationships were determined for each kind of the substrate. A tin-enriched surface layer on our thin films measured by depth-resolved photoelectron spectroscopy suggests surfactant-mediated epitaxy as a possible growth mechanism. Thin films in the κ-phase are a promising alternative for β-Ga2O3 layers in electronic and optoelectronic device applications.High-quality Ga2O3 thin films in the orthorhombic κ-phase are grown by pulsed-laser deposition using a tin containing target on c-sapphire, MgO(111), SrTiO3(111), and yttria-stabilized ZrO2(111) substrates. The structural quality of the layers is studied based on the growth parameters employing X-ray diffraction 2θ-ω scans, rocking curves, ϕ scans, and reciprocal space maps. Our layers exhibit superior crystalline properties in comparison to thin films deposited in the monoclinic β-phase at nominally identical growth parameters. Furthermore, the surface morphology is significantly improved and the root-mean-squared roughness of the layers was as low as ≈0.5 nm, on par with homoepitaxial β-Ga2O3 thin films in the literature. The orthorhombic structure of the thin films was evidenced, and the epitaxial relationships were determined for each kind of the substrate. A tin-enriched surface layer on our thin films measured by depth-resolved photoelectron spectroscopy suggests surfactant-mediated epitaxy as a pos...
TL;DR: In this article, the authors studied the thermal transport across the interfaces of Ga2O3 exfoliated onto a single crystal diamond and found that the van der Waals bonded temperature was 17 −1.7/+2.0 MW/m2 K, which is comparable to the TBC of several physical-vapor-deposited metals on diamond.
Abstract: Because of its ultra-wide bandgap, high breakdown electric field, and large-area affordable substrates grown from the melt, β-Ga2O3 has attracted great attention recently for potential applications of power electronics. However, its thermal conductivity is significantly lower than those of other wide bandgap semiconductors, such as AlN, SiC, GaN, and diamond. To ensure reliable operation with minimal self-heating at high power, proper thermal management is even more essential for Ga2O3 devices. Similar to the past approaches aiming to alleviate self-heating in GaN high electron mobility transistors, a possible solution has been to integrate thin Ga2O3 membranes with diamond to fabricate Ga2O3-on-diamond lateral metal-semiconductor field-effect transistor or metal-oxide-semiconductor field-effect transistor devices by taking advantage of the ultra-high thermal conductivity of diamond. Even though the thermal boundary conductance (TBC) between wide bandgap semiconductor devices and a diamond substrate is of primary importance for heat dissipation in these devices, fundamental understanding of the Ga2O3-diamond thermal interface is still missing. In this work, we study the thermal transport across the interfaces of Ga2O3 exfoliated onto a single crystal diamond. The van der Waals bonded Ga2O3-diamond TBC is measured to be 17 −1.7/+2.0 MW/m2 K, which is comparable to the TBC of several physical-vapor-deposited metals on diamond. A Landauer approach is used to help understand phonon transport across a perfect Ga2O3-diamond interface, which in turn sheds light on the possible TBC one could achieve with an optimized interface. A reduced thermal conductivity of the Ga2O3 nano-membrane is also observed due to additional phonon-membrane boundary scattering. The impact of the Ga2O3–substrate TBC and substrate thermal conductivity on the thermal performance of a power device is modeled and discussed. Without loss of generality, this study is not only important for Ga2O3 power electronics applications which would not be realistic without a thermal management solution but also for the fundamental thermal science of heat transport across van der Waals bonded interfaces.
TL;DR: In this article, NiMoO4/NiO nanoflowers material with a high specific surface area grown on a nickel foam conductive substrate is successfully synthesized via a facile and efficient method, which exhibits an excellent capacitance of 10.3
TL;DR: The authors show that the properties of a microgel can change from colloidal-like in three dimensions to a flexible polymer under a confined environment.
Abstract: Microgels are solvent-swollen nano- and microparticles that show prevalent colloidal-like behavior despite their polymeric nature. Here we study ultra-low crosslinked poly(N-isopropylacrylamide) microgels (ULC), which can behave like colloids or flexible polymers depending on dimensionality, compression or other external stimuli. Small-angle neutron scattering shows that the structure of the ULC microgels in bulk aqueous solution is characterized by a density profile that decays smoothly from the center to a fuzzy surface. Their phase behavior and rheological properties are those of soft colloids. However, when these microgels are confined at an oil-water interface, their behavior resembles that of flexible macromolecules. Once monolayers of ultra-low crosslinked microgels are compressed, deposited on solid substrate and studied with atomic-force microscopy, a concentration-dependent topography is observed. Depending on the compression, these microgels can behave as flexible polymers, covering the substrate with a uniform film, or as colloidal microgels leading to a monolayer of particles. Microgels combine the properties of flexible polymers and colloids, but effects which influence the individual properties are less known. Here the authors show that the properties of a microgel can change from colloidal-like in three dimensions to a flexible polymer under a confined environment.
TL;DR: In this article, the authors describe room-temperature photoluminescence (PL) emitters that naturally occur whenever monolayer transition metal dichalcogenides (TMDCs) is deposited on an atomically flat substrate.
Abstract: The possibility to tailor photoluminescence (PL) of monolayer transition metal dichalcogenides (TMDCs) using external factors such as strain, doping and external environment is of significant interest for optoelectronic applications. Strain in particular can be exploited as a means to continuously vary the bandgap. Micrometer-scale strain gradients were proposed for creating 'artificial atoms' that can utilize the so-called exciton funneling effect and work, for example, as exciton condensers. Here we describe room-temperature PL emitters that naturally occur whenever monolayer TMDC is deposited on an atomically flat substrate. These are hydrocarbon-filled bubbles which provide predictable, localized PL from well-separated submicron areas. Their emission energy is determined by the built-in strain controlled only by the substrate material, such that both the maximum strain and the strain profile are universal for all bubbles on a given substrate, i.e., independent of the bubble size. We show that for bubbles formed by monolayer MoS2, PL can be tuned between 1.72 to 1.81 eV by choosing bulk PtSe2, WS2, MoS2 or graphite as a substrate and its intensity is strongly enhanced by the funneling effect. Strong substrate-dependent quenching of the PL in areas of good contact between MoS2 and the substrate ensures localization of the luminescence to bubbles only; by employing optical reflectivity measurements we identify the mechanisms responsible for the quenching. Given the variety of available monolayer TMDCs and atomically flat substrates and the ease of creating such bubbles, our findings open a venue for making and studying the discussed light-emitting 'artificial atoms' that could be used in applications.
TL;DR: In this paper, α-Ga2O3 homoepitaxial films were grown on commercially available c-plane sapphire substrates, and the film morphology was found to be strongly impacted by the surface finish of the substrate.
Abstract: Halide vapor phase epitaxy was used to grow homoepitaxial films of β-Ga2O3 on bulk (010) crystals and heteroepitaxial films of α-Ga2O3 on c-plane sapphire substrates. The β-Ga2O3 substrates were prepared prior to growth to remove sub-surface damage and to apply various miscuts to their surfaces. Structural and electrical properties were found to be most impacted by the crystallinity of the β-Ga2O3 substrate itself, while the surface morphology was found to be most impacted by the miscut of the substrate. The appropriate choice of growth conditions and the miscut appear to be critical to realizing smooth, thick (>20 µm) homoepitaxial films of β-Ga2O3. The α-Ga2O3 films were grown on commercially available c-plane sapphire substrates, and the film morphology was found to be strongly impacted by the surface finish of the sapphire substrates. The α-Ga2O3 films were found to be smooth and free of additional phases or crystal twinning when the sapphire was sufficiently polished prior to growth.
TL;DR: It is found that VG nanowalls can effectively enhance the heat dissipation between an AlN film and a sapphire substrate in the longitudinal direction because of their unique vertical structure and good thermal conductivity.
Abstract: For III-nitride-based devices, such as high-brightness light-emitting diodes (LEDs), the poor heat dissipation of the sapphire substrate is deleterious to the energy efficiency and restricts many of their applications. Herein, the role of vertically oriented graphene (VG) nanowalls as a buffer layer for improving the heat dissipation in AlN films on sapphire substrates is studied. It is found that VG nanowalls can effectively enhance the heat dissipation between an AlN film and a sapphire substrate in the longitudinal direction because of their unique vertical structure and good thermal conductivity. Thus, an LED fabricated on a VG-sapphire substrate shows a 37% improved light output power under a high injection current (350 mA) with an effective 3.8% temperature reduction. Moreover, the introduction of VG nanowalls does not degrade the quality of the AlN film, but instead promotes AlN nucleation and significantly reduces the epilayer strain that is generated during the cooling process. These findings suggest that the VG nanowalls can be a good buffer layer candidate in III-nitride semiconductor devices, especially for improving the heat dissipation in high-brightness LEDs.
TL;DR: In this article, an electrically tunable metasurface is proposed to achieve relatively large phase modulation in both reflection and transmission modes (dual-mode operation) by integration of an ultrathin layer of indium tin oxide (ITO) as an electro-optable material into a semiconductor-insulator-semiconductor (SIS) unit cell.
Abstract: We propose an electrically tunable metasurface, which can achieve relatively large phase modulation in both reflection and transmission modes (dual-mode operation). By integration of an ultrathin layer of indium tin oxide (ITO) as an electro-optically tunable material into a semiconductor-insulator-semiconductor (SIS) unit cell, we report an approach for active tuning of all-dielectric metasurfaces. The proposed controllable dual-mode metasurface includes an array of silicon (Si) nanodisks connected together via Si nanobars. These are placed on top of alumina and ITO layers, followed by a Si slab and a silica substrate. The required optical resonances are separately excited by Si nanobars in reflection and Si nanodisks in transmission, enabling highly confined electromagnetic fields at the ITO-alumina interface. Modulation of charge carrier concentration and refractive index in the ITO accumulation layer by varying the applied bias voltage leads to 240° of phase agility at an operating wavelength of 1696 nm for the reflected transverse electric (TE)-polarized beam and 270° of phase shift at 1563 nm for the transmitted transverse magnetic (TM)-polarized light. Independent and isolated control of the reflection and transmission modes enables distinctly different functions to be achieved for each operation mode. A rigorous coupled electrical and optical model is employed to characterize the carrier distributions in ITO and Si under applied bias and to accurately assess the voltage-dependent effects of inhomogeneous carrier profiles on the optical behavior of a unit cell.
TL;DR: In this paper, the effect of the thickness of the adhesion layers (0.3 and 0.7) and the wear-resistant layer (2.0, 4.0 and 8.0) on the microhardness, adhesion bond strength, and performance properties of the ZrN-(Zr,Al,Si)N coatings was investigated.
Abstract: The study involved the investigation of the effect of the thickness of the adhesion layers (0.3 and 0.7 μm) and the wear-resistant layer (2.0, 4.0, 6.0, and 8.0 μm) on the microhardness, adhesion bond strength, and performance properties of the ZrN-(Zr,Al,Si)N coatings. The scratch-test method was applied to study the adhesion bond strength to the substrate and coating failure patterns. The study revealed an effect of the coefficient kwa, determining the effect of the thicknesses of the wear-resistant and adhesion layers of the coating on the value of the critical load LC2. The study investigated the wear patterns and mechanisms for the specified coatings and the tool life of tools with these coatings in turning. An effect of the coefficient kwa which is the adhesion and wear-resistant layer thickness ratio on the tool life and a difference in the wear pattern dynamics for tools with these coatings with wear-resistant layers of equal thickness and adhesion layers of different thicknesses was revealed. The study also determined the chemical and phase composition of the coatings.
TL;DR: In this paper, the absence of any significant electronically active tail states within the bulk of the (FA0.85MA0.1Cs0.05) PbBr3 absorber was found.
Abstract: High band gap Pb bromide perovskite (APbBr3)-based solar cells, where A is a mixture of formamidinium, methylammonium, and Cs, show significantly higher, relative, VOC losses than their iodide analogs. Using photoluminescence-, quantum efficiency-, and surface photovoltage-spectroscopy measurements, we show the absence of any significant electronically active tail states within the bulk of the (FA0.85MA0.1Cs0.05)PbBr3 absorber. All methods confirm that EG = 2.28 eV for this halide perovskite, HaP. Contact potential difference measurements for this HaP, on different substrates, reveal a Z-shape dependence between the substrate work functions and that of the HaP, deposited on it, indicating that the HaP is relatively low doped and that its Fermi level is affected by the substrate onto which it is deposited. We confirm results from electron beam-induced current (EBIC) and other measurements that most voltage loss of cells, made with these HaP films, is at the HaP/selective-contact interface, specifically the...
20 Mar 2019
TL;DR: In this article, the authors focus on 7 and 9-atom wide armchair graphene nanoribbons (i.e., 7-AGNR and 9AGNR) grown on 200 nm Au(111)/mica substrates using a high throughput system.
Abstract: Recent progress in the on-surface synthesis of graphene nanoribbons (GNRs) has given access to atomically precise narrow GNRs with tunable electronic band gaps which makes them excellent candidates for room temperature switching devices such as field-effect transistors (FET). However, in spite of their exceptional properties, significant challenges remain for GNR processing and characterization. This contribution addresses some of the most important challenges, including GNR fabrication scalability, substrate transfer, long-term stability under ambient conditions, and ex situ characterization. We focus on 7- and 9-atom-wide armchair graphene nanoribbons (i.e., 7-AGNR and 9-AGNR) grown on 200 nm Au(111)/mica substrates using a high throughput system. Transfer of both 7- and 9-AGNRs from their Au growth substrate onto various target substrates for additional characterization is accomplished utilizing a polymer-free method that avoids residual contamination. This results in a homogeneous GNR film morphology ...
TL;DR: Graphene grown on silicon carbide is found to be the most promising substrate for obtaining of 1–5 nm thick Bi2Se3 films.
Abstract: Knowledge of nucleation and further growth of Bi2Se3 nanoplates on different substrates is crucial for obtaining ultrathin nanostructures and films of this material by physical vapour deposition technique. In this work, Bi2Se3 nanoplates were deposited under the same experimental conditions on different types of graphene substrates (as-transferred and post-annealed chemical vapour deposition grown monolayer graphene, monolayer graphene grown on silicon carbide substrate). Dimensions of the nanoplates deposited on graphene substrates were compared with the dimensions of the nanoplates deposited on mechanically exfoliated mica and highly ordered pyrolytic graphite flakes used as reference substrates. The influence of different graphene substrates on nucleation and further lateral and vertical growth of the Bi2Se3 nanoplates is analysed. Possibility to obtain ultrathin Bi2Se3 thin films on these substrates is evaluated. Between the substrates considered in this work, graphene grown on silicon carbide is found to be the most promising substrate for obtaining of 1–5 nm thick Bi2Se3 films.
TL;DR: A new approach for the fabrication of ultraflat single-crystal graphene using Cu/Ni (111)/sapphire wafers at lower temperature is reported and it is found that the temperature of epitaxial growth of graphene usingCu/ Ni (111) can be reduced to 750 °C, much lower than that of earlier reports on catalytic surfaces.
Abstract: The future electronic application of graphene highly relies on the production of large-area high-quality single-crystal graphene. However, the growth of single-crystal graphene on different substrates via either single nucleation or seamless stitching is carried out at a temperature of 1000 °C or higher. The usage of this high temperature generates a variety of problems, including complexity of operation, higher contamination, metal evaporation, and wrinkles owing to the mismatch of thermal expansion coefficients between the substrate and graphene. Here, a new approach for the fabrication of ultraflat single-crystal graphene using Cu/Ni (111)/sapphire wafers at lower temperature is reported. It is found that the temperature of epitaxial growth of graphene using Cu/Ni (111) can be reduced to 750 °C, much lower than that of earlier reports on catalytic surfaces. Devices made of graphene grown at 750 °C have a carrier mobility up to ≈9700 cm2 V-1 s-1 at room temperature. This work shines light on a way toward a much lower temperature growth of high-quality graphene in single crystallinity, which could benefit future electronic applications.
TL;DR: In this paper, the most recent advances of β-Ga2O3-based power devices are reviewed, including diodes and FETs, and the performance of state-of-the-art gallium oxide-based devices are compared.
Abstract: Until very recently, gallium oxide (Ga2O3) has aroused more and more interests in the area of power electronics due to its ultra-wide bandgap of 4.5–4.8 eV, estimated critical field of 8 MV/cm and decent intrinsic electron mobility limit of 250 cm2/(V·s), yielding a high Baliga’s figures-of-merit (FOM) of more than 3000, which is several times higher than GaN and SiC. In addition to its excellent material properties, potential low-cost and large size substrate through melt-grown methodology also endows β-Ga2O3 more potential for future low-cost power devices. This article focuses on reviewing the most recent advances of β-Ga2O3 based power devices. It will be starting with a brief introduction to the material properties of β-Ga2O3 and then the growth techniques of its native substrate, followed by the thin film epitaxial growth. The performance of state-of-art β-Ga2O3 devices, including diodes and FETs are fully discussed and compared. Finally, potential solutions to the challenges of β-Ga2O3 are also discussed and explored.
TL;DR: A stretchable organometal-halide-perovskite quantum-dot LED with both high efficiency and mechanical compliancy is demonstrated, which can survive 1000 stretch-release cycles of 20% tensile strain with small fluctuations in electroluminescent performance.
Abstract: Stretchable light-emitting diodes (LEDs) and electroluminescent capacitors have been reported to potentially bring new opportunities to wearable electronics; however, these devices lack in efficiency and/or stretchability. Here, a stretchable organometal-halide-perovskite quantum-dot LED with both high efficiency and mechanical compliancy is demonstrated. The hybrid device employs an ultrathin (<3 µm) LED structure conformed on a surface-wrinkled elastomer substrate. Its luminescent efficiency is up to 9.2 cd A-1 , which is 70% higher than a control diode fabricated on the rigid indium tin oxide/glass substrate. Mechanical deformations up to 50% tensile strain do not induce significant loss of the electroluminescent property. The device can survive 1000 stretch-release cycles of 20% tensile strain with small fluctuations in electroluminescent performance.