Showing papers on "Thin film published in 2014"
TL;DR: A low-temperature vapor-assisted solution process is demonstrated to construct polycrystalline perovskite thin films with full surface coverage, small surface roughness, and grain size up to microscale, paving the way for high reproducibility of films and devices.
Abstract: Hybrid organic/inorganic perovskites (e.g., CH3NH3PbI3) as light absorbers are promising players in the field of third-generation photovoltaics. Here we demonstrate a low-temperature vapor-assisted solution process to construct polycrystalline perovskite thin films with full surface coverage, small surface roughness, and grain size up to microscale. Solar cells based on the as-prepared films achieve high power conversion efficiency of 12.1%, so far the highest efficiency based on CH3NH3PbI3 with the planar heterojunction configuration. This method provides a simple approach to perovskite film preparation and paves the way for high reproducibility of films and devices. The underlying kinetic and thermodynamic parameters regarding the perovskite film growth are discussed as well.
2,136 citations
TL;DR: Using highly sensitive photothermal deflection and photocurrent spectroscopy, the absorption spectrum of CH3NH3PbI3 perovskite thin films at room temperature is measured, finding a high absorption coefficient with particularly sharp onset and a compositional change of the material.
Abstract: Solar cells based on organometallic halide perovskite absorber layers are emerging as a high-performance photovoltaic technology. Using highly sensitive photothermal deflection and photocurrent spectroscopy, we measure the absorption spectrum of CH3NH3PbI3 perovskite thin films at room temperature. We find a high absorption coefficient with particularly sharp onset. Below the bandgap, the absorption is exponential over more than four decades with an Urbach energy as small as 15 meV, which suggests a well-ordered microstructure. No deep states are found down to the detection limit of ∼1 cm–1. These results confirm the excellent electronic properties of perovskite thin films, enabling the very high open-circuit voltages reported for perovskite solar cells. Following intentional moisture ingress, we find that the absorption at photon energies below 2.4 eV is strongly reduced, pointing to a compositional change of the material.
2,099 citations
TL;DR: It is reported that flat, uniform thin films of this material can be deposited by a one-step, solvent-induced, fast crystallization method involving spin-coating of a DMF solution of CH3NH3PbI3 followed immediately by exposure to chlorobenzene to induce crystallization.
Abstract: Thin-film photovoltaics based on alkylammonium lead iodide perovskite light absorbers have recently emerged as a promising low-cost solar energy harvesting technology. To date, the perovskite layer in these efficient solar cells has generally been fabricated by either vapor deposition or a two-step sequential deposition process. We report that flat, uniform thin films of this material can be deposited by a one-step, solvent-induced, fast crystallization method involving spin-coating of a DMF solution of CH3NH3PbI3 followed immediately by exposure to chlorobenzene to induce crystallization. Analysis of the devices and films revealed that the perovskite films consist of large crystalline grains with sizes up to microns. Planar heterojunction solar cells constructed with these solution-processed thin films yielded an average power conversion efficiency of 13.9±0.7% and a steady state efficiency of 13% under standard AM 1.5 conditions.
1,554 citations
TL;DR: This controllable self-induced passivation technique for perovskite films is demonstrated, which enables their compositional change, and allows substantial enhancement in corresponding device performance.
Abstract: To improve the performance of the polycrystalline thin film devices, it requires a delicate control of its grain structures. As one of the most promising candidates among current thin film photovoltaic techniques, the organic/inorganic hybrid perovskites generally inherit polycrystalline nature and exhibit compositional/structural dependence in regard to their optoelectronic properties. Here, we demonstrate a controllable passivation technique for perovskite films, which enables their compositional change, and allows substantial enhancement in corresponding device performance. By releasing the organic species during annealing, PbI2 phase is presented in perovskite grain boundaries and at the relevant interfaces. The consequent passivation effects and underlying mechanisms are investigated with complementary characterizations, including scanning electron microscopy (SEM), X-ray diffraction (XRD), time-resolved photoluminescence decay (TRPL), scanning Kelvin probe microscopy (SKPM), and ultraviolet photoemi...
1,298 citations
TL;DR: Atomic layer deposition (ALD) is a vapor phase technique capable of producing thin films of a variety of materials as discussed by the authors, including metal oxides such as Zn1−xSnxOy, ZrO2, Y2O3, and Pt.
1,280 citations
TL;DR: An ultra-sensitive resistive pressure sensor based on an elastic, microstructured conducting polymer thin film that enables the detection of pressures of less than 1Pa and exhibits a short response time, good reproducibility, excellent cycling stability and temperature-stable sensing.
Abstract: Pressure sensing is an important function of electronic skin devices. The development of pressure sensors that can mimic and surpass the subtle pressure sensing properties of natural skin requires the rational design of materials and devices. Here we present an ultra-sensitive resistive pressure sensor based on an elastic, microstructured conducting polymer thin film. The elastic microstructured film is prepared from a polypyrrole hydrogel using a multiphase reaction that produced a hollow-sphere microstructure that endows polypyrrole with structure-derived elasticity and a low effective elastic modulus. The contact area between the microstructured thin film and the electrodes increases with the application of pressure, enabling the device to detect low pressures with ultra-high sensitivity. Our pressure sensor based on an elastic microstructured thin film enables the detection of pressures of less than 1Pa and exhibits a short response time, good reproducibility, excellent cycling stability and temperature-stable sensing.
1,199 citations
TL;DR: Using copper iodide, this work has succeeded in achieving a promising power conversion efficiency of 6.0% with excellent photocurrent stability and impedance spectroscopy revealed that CuI exhibits 2 orders of magnitude higher electrical conductivity than spiro-OMeTAD which allows for significantly higher fill factors.
Abstract: Organo-lead halide perovskite solar cells have emerged as one of the most promising candidates for the next generation of solar cells. To date, these perovskite thin film solar cells have exclusively employed organic hole conducting polymers which are often expensive and have low hole mobility. In a quest to explore new inorganic hole conducting materials for these perovskite-based thin film photovoltaics, we have identified copper iodide as a possible alternative. Using copper iodide, we have succeeded in achieving a promising power conversion efficiency of 6.0% with excellent photocurrent stability. The open-circuit voltage, compared to the best spiro-OMeTAD devices, remains low and is attributed to higher recombination in CuI devices as determined by impedance spectroscopy. However, impedance spectroscopy revealed that CuI exhibits 2 orders of magnitude higher electrical conductivity than spiro-OMeTAD which allows for significantly higher fill factors. Reducing the recombination in these devices could ...
1,169 citations
TL;DR: This work reports the preparation of 6 nm-sized nanoparticles of this type by a simple and fast method based on the use of an ammonium bromide with a medium-sized chain that keeps the nanoparticles dispersed in a wide range of organic solvents.
Abstract: To date, there is no example in the literature of free, nanometer-sized, organolead halide CH3NH3PbBr3 perovskites. We report here the preparation of 6 nm-sized nanoparticles of this type by a simple and fast method based on the use of an ammonium bromide with a medium-sized chain that keeps the nanoparticles dispersed in a wide range of organic solvents. These nanoparticles can be maintained stable in the solid state as well as in concentrated solutions for more than three months, without requiring a mesoporous material. This makes it possible to prepare homogeneous thin films of these nanoparticles by spin-coating on a quartz substrate. Both the colloidal solution and the thin film emit light within a narrow bandwidth of the visible spectrum and with a high quantum yield (ca. 20%); this could be advantageous in the design of optoelectronic devices.
1,090 citations
TL;DR: A low-cost, solution-based deposition procedure utilizing nanocomposites of graphene and TiO2 nanoparticles as the electron collection layers in meso-superstructured perovskite solar cells shows the potential to contribute significantly toward the development of low- cost solar cells.
Abstract: The highest efficiencies in solution-processable perovskite-based solar cells have been achieved using an electron collection layer that requires sintering at 500 °C. This is unfavorable for low-cost production, applications on plastic substrates, and multijunction device architectures. Here we report a low-cost, solution-based deposition procedure utilizing nanocomposites of graphene and TiO2 nanoparticles as the electron collection layers in meso-superstructured perovskite solar cells. The graphene nanoflakes provide superior charge-collection in the nanocomposites, enabling the entire device to be fabricated at temperatures no higher than 150 °C. These solar cells show remarkable photovoltaic performance with a power conversion efficiency up to 15.6%. This work demonstrates that graphene/metal oxide nanocomposites have the potential to contribute significantly toward the development of low-cost solar cells.
948 citations
TL;DR: The introduction of hydrogen in the reaction chamber helps to activate the selenization of WO3, where large-size WSe2 monolayer flakes or thin films can be successfully grown and the resistor-loaded inverter based on a WSe 2 film, with a gain of ∼13, further demonstrates its applicability for logic-circuit integrations.
Abstract: The monolayer transition metal dichalcogenides have recently attracted much attention owing to their potential in valleytronics, flexible and low-power electronics, and optoelectronic devices. Recent reports have demonstrated the growth of large-size two-dimensional MoS2 layers by the sulfurization of molybdenum oxides. However, the growth of a transition metal selenide monolayer has still been a challenge. Here we report that the introduction of hydrogen in the reaction chamber helps to activate the selenization of WO3, where large-size WSe2 monolayer flakes or thin films can be successfully grown. The top-gated field-effect transistors based on WSe2 monolayers using ionic gels as the dielectrics exhibit ambipolar characteristics, where the hole and electron mobility values are up to 90 and 7 cm2/Vs, respectively. These films can be transferred onto arbitrary substrates, which may inspire research efforts to explore their properties and applications. The resistor-loaded inverter based on a WSe2 film, wit...
889 citations
TL;DR: Using impedance spectroscopy measurements, a measurement of the diffusion length in a nanostructured perovskite solar cell is reported for the first time, highlighting the central role of the CH3NH3PbX3 semiconductor absorber in carrier collection and providing a new tool for improved optimization of perovSKite solar cells.
Abstract: Organometal halide perovskite-based solar cells have recently realized large conversion efficiency over 15% showing great promise for a new large scale cost-competitive photovoltaic technology. Using impedance spectroscopy measurements we are able to separate the physical parameters of carrier transport and recombination in working devices of the two principal morphologies and compositions of perovskite solar cells, viz. compact thin films of CH3NH3PbI3–xClx and CH3NH3PbI3 infiltrated on nanostructured TiO2. The results show nearly identical spectral characteristics indicating a unique photovoltaic operating mechanism that provides long diffusion lengths (1 μm). Carrier conductivity in both devices is closely matched, so that the most significant differences in performance are attributed to recombination rates. These results highlight the central role of the CH3NH3PbX3 semiconductor absorber in carrier collection and provide a new tool for improved optimization of perovskite solar cells. We report for the...
TL;DR: In this article, the optical conductivity tensor of multilayer black phosphorus thin films using the Kubo formula within an effective low-energy Hamiltonian was calculated, and the role of interband coupling and disorder on observed anisotropic absorption spectra was discussed.
Abstract: Black phosphorus thin films might offer attractive alternatives to narrow-gap compound semiconductors for optoelectronics across mid- to near-infrared frequencies. In this work, we calculate the optical conductivity tensor of multilayer black phosphorus thin films using the Kubo formula within an effective low-energy Hamiltonian. The optical absorption spectra of multilayer black phosphorus are shown to vary sensitively with thickness, doping, and light polarization. In conjunction with experimental spectra obtained from infrared absorption spectroscopy, we also discuss the role of interband coupling and disorder on the observed anisotropic absorption spectra.
TL;DR: This work demonstrates hybrid solar cells based on the mixed perovskite CH3 NH3 PbI2 Cl in a thin film sandwich structure, with unprecedented reproducibility and generating efficiencies up to 10.8%.
Abstract: Organometal halide perovskites have tremendous potential as light absorbers for photovoltaic applications. In this work we demonstrate hybrid solar cells based on the mixed perovskite CH3 NH3 PbI2 Cl in a thin film sandwich structure, with unprecedented reproducibility and generating efficiencies up to 10.8%. The successfulness of our approach is corroborated by the experimental electronic structure determination of this perovskite.
TL;DR: This work demonstrates optical control of ferromagnetic materials ranging from magnetic thin films to multilayers and even granular films being explored for ultra-high-density magnetic recording, and shows that Optical control of magnetic materials is a much more general phenomenon than previously assumed.
Abstract: The interplay of light and magnetism allowed light to be used as a probe of magnetic materials. Now the focus has shifted to use polarized light to alter or manipulate magnetism. Here, we demonstrate optical control of ferromagnetic materials ranging from magnetic thin films to multilayers and even granular films being explored for ultra-high-density magnetic recording. Our finding shows that optical control of magnetic materials is a much more general phenomenon than previously assumed and may have a major impact on data memory and storage industries through the integration of optical control of ferromagnetic bits.
TL;DR: It is demonstrated that larger crystallites present smaller band gap and longer lifetime, which correlates to a smaller radiative bimolecular recombination coefficient, and also shows that they present a higher optical gain, becoming preferred candidates for the realization of CW lasing devices.
Abstract: We report about the relationship between the morphology and luminescence properties of methylammonium lead trihalide perovskite thin films. By tuning the average crystallite dimension in the film from tens of nanometers to a few micrometers, we are able to tune the optical band gap of the material along with its photoluminescence lifetime. We demonstrate that larger crystallites present smaller band gap and longer lifetime, which correlates to a smaller radiative bimolecular recombination coefficient. We also show that they present a higher optical gain, becoming preferred candidates for the realization of CW lasing devices.
TL;DR: Effective diffusion lengths, LD, show that holes are extracted significantly more efficiently than electrons in CH3NH3PbI3-based solar cells, explaining why these cells require mesoporous electron conductors, while 3-Clx ones, where LD values are comparable for both charge types, do not.
Abstract: CH3NH3PbI3-based solar cells were characterized with electron beam-induced current (EBIC), and compared to CH3NH3PbI3-xClx ones. A spatial map of charge separation efficiency in working cells shows p-i-n structures for both thin film cells. Effective diffusion lengths, LD, (from EBIC profile) show that holes are extracted significantly more efficiently than electrons in CH3NH3PbI3, explaining why CH3NH3PbI3-based cells require mesoporous electron conductors, while CH3NH3PbI3-xClx ones, where LD values are comparable for both charge types, do not.
TL;DR: This work has grown, for the first time, macroscopically large crystalline thin films of triazine-based, graphitic carbon nitride (TGCN) using an ionothermal, interfacial reaction starting with the abundant monomer dicyandiamide.
Abstract: Graphitic carbon nitride has been predicted to be structurally analogous to carbon-only graphite, yet with an inherent bandgap. We have grown, for the first time, macroscopically large crystalline thin films of triazine-based, graphitic carbon nitride (TGCN) using an ionothermal, interfacial reaction starting with the abundant monomer dicyandiamide. The films consist of stacked, two-dimensional (2D) crystals between a few and several hundreds of atomic layers in thickness. Scanning force and transmission electron microscopy show long-range, in-plane order, while optical spectroscopy, X-ray photoelectron spectroscopy, and density functional theory calculations corroborate a direct bandgap between 1.6 and 2.0 eV. Thus TGCN is of interest for electronic devices, such as field-effect transistors and light-emitting diodes.
TL;DR: In this paper, electron beam-induced current (EBIC) profile was used to characterize CH3NH3PbI3-based solar cells and compared to CH 3NH3pbI-3-xClx ones.
Abstract: CH3NH3PbI3-based solar cells were characterized with electron beam-induced current (EBIC) and compared to CH3NH3PbI3–xClx ones. A spatial map of charge separation efficiency in working cells shows p-i-n structures for both thin film cells. Effective diffusion lengths, LD, (from EBIC profile) show that holes are extracted significantly more efficiently than electrons in CH3NH3PbI3, explaining why CH3NH3PbI3-based cells require mesoporous electron conductors, while CH3NH3PbI3–xClx ones, where LD values are comparable for both charge types, do not.
TL;DR: In this article, a survey of solution-based processing techniques for plastic electronics relevant on both the commercial and research scale and a set of strategies to control thin film morphology towards enhancing their electronic transport properties.
Abstract: While the chemical structure of organic semiconductors has an obvious effect on their proclivity for charge transport, the ways with which they are processed have a dramatic effect on the performance of plastic electronics devices incorporating them. In some cases, morphological defects and misalignment of crystalline grains can completely obscure the materials' intrinsic charge transport properties. Although some deposition methods, especially vapor-phase ones, can produce single crystals and thus avoid some of these problems, it is desirable to gain a fundamental understanding of how to improve charge transport when using solution-phase deposition techniques. In this review, we present both a survey of solution-based processing techniques for plastic electronics relevant on both the commercial and research scale and a set of strategies to control thin film morphology towards enhancing their electronic transport properties.
TL;DR: In this article, loss mechanisms are systematically investigated and mitigated in solar cells based on p-type tin monosulfide, SnS, absorber layers combined with n-type zinc oxysulfide and Zn(O,S) layers that selectively transmit electrons, but block holes.
Abstract: Thin-film solar cells are made by vapor deposition of Earth-abundant materials: tin, zinc, oxygen and sulfur. These solar cells had previously achieved an efficiency of about 2%, less than 1/10 of their theoretical potential. Loss mechanisms are systematically investigated and mitigated in solar cells based on p-type tin monosulfide, SnS, absorber layers combined with n-type zinc oxysulfide, Zn(O,S) layers that selectively transmit electrons, but block holes. Recombination at grain boundaries is reduced by annealing the SnS films in H2S to form larger grains with fewer grain boundaries. Recombination near the p-SnS/n-Zn(O,S) junction is reduced by inserting a few monolayers of SnO2 between these layers. Recombination at the junction is also reduced by adjusting the conduction band offset by tuning the composition of the Zn(O,S), and by reducing its free electron concentration with nitrogen doping. The resulting cells have an efficiency over 4.4%, which is more than twice as large as the highest efficiency obtained previously by solar cells using SnS absorber layers.
TL;DR: In this paper, a gas-assisted solution processing technique has been used to change the kinetics of nucleation and crystal growth of the perovskite during spin coating, producing very uniform thin films consisting of densely packed single crystalline grains.
TL;DR: A power conversion efficiency of 10.4% is demonstrated in planar CH3 NH3 PbBr3 hybrid solar cells without hysteresis of the J-V curve, by way of controlled crystallization in the spin-coating process.
Abstract: A power conversion efficiency of 10.4% is demonstrated in planar CH3 NH3 PbBr3 hybrid solar cells without hysteresis of the J-V curve, by way of controlled crystallization in the spin-coating process. The high efficiency is attributed to the formation of a dense CH3 NH3 PbBr3 thin film by the introduction of HBr solution because the HBr increases the solubility of the CH3 NH3 PbBr3 and forms a thinner CH3 NH3 PbBr3 layer with full surface coverage.
TL;DR: This work investigates the electronic transport properties of individual crystallites of high quality CVD-grown monolayer MoS2 and shows that the short-range scattering plays a dominant role in the highly conducting regime at low temperatures.
Abstract: Recent success in the growth of monolayer MoS2 via chemical vapor deposition (CVD) has opened up prospects for the implementation of these materials into thin film electronic and optoelectronic devices Here, we investigate the electronic transport properties of individual crystallites of high quality CVD-grown monolayer MoS2 The devices show low temperature mobilities up to 500 cm(2) V(-1) s(-1) and a clear signature of metallic conduction at high doping densities These characteristics are comparable to the electronic properties of the best mechanically exfoliated monolayers in literature, verifying the high electronic quality of the CVD-grown materials We analyze the different scattering mechanisms and show that the short-range scattering plays a dominant role in the highly conducting regime at low temperatures Additionally, the influence of optical phonons as a limiting factor is discussed
TL;DR: The planar-structured generator features an all-in-one design without separate and movable components for capturing and transmitting mechanical energy, making it a portable, flexible, and convenient power solution that can be applied on the ocean/river surface, at coastal/offshore areas, and even in rainy places.
Abstract: Energy harvesting from ambient water motions is a desirable but underexplored solution to on-site energy demand for self-powered electronics. Here we report a liquid-solid electrification-enabled generator based on a fluorinated ethylene propylene thin film, below which an array of electrodes are fabricated. The surface of the thin film is charged first due to the water-solid contact electrification. Aligned nanowires created on the thin film make it hydrophobic and also increase the surface area. Then the asymmetric screening to the surface charges by the waving water during emerging and submerging processes causes the free electrons on the electrodes to flow through an external load, resulting in power generation. The generator produces sufficient output power for driving an array of small electronics during direct interaction with water bodies, including surface waves and falling drops. Polymer-nanowire-based surface modification increases the contact area at the liquid-solid interface, leading to enhanced surface charging density and thus electric output at an efficiency of 7.7%. Our planar-structured generator features an all-in-one design without separate and movable components for capturing and transmitting mechanical energy. It has extremely lightweight and small volume, making it a portable, flexible, and convenient power solution that can be applied on the ocean/river surface, at coastal/offshore areas, and even in rainy places. Considering the demonstrated scalability, it can also be possibly used in large-scale energy generation if layers of planar sheets are connected into a network.
TL;DR: A novel sequential layer-by-layer sub-100 °C vacuum-sublimation method to fabricate planar-type organometal halide perovskite solar cells is developed, suitable for a wide variety of rigid and flexible applications.
Abstract: A novel sequential layer-by-layer sub-100 °C vacuum-sublimation method to fabricate planar-type organometal halide perovskite solar cells is developed. Very uniform and highly crystalline perovskite thin films with 100% surface coverage are produced. The cells attain maximum and average efficiencies up to 15.4% and 14%, respectively. This low- temperature, all-vacuum process is suitable for a wide variety of rigid and flexible applications.
TL;DR: In this article, the authors discuss recent experiments that directly measure mobility at or near the surface of glassy polymers and indicate that enhanced mobility near the free surface can exceed bulk mobility by several orders of magnitude and extend for several nanometers into the bulk polymer.
Abstract: The past 20 years have seen a substantial effort to understand dynamics and the glass transition in thin polymer films. In this Perspective, we consider developments in this field and offer a consistent interpretation of some major findings. We discuss recent experiments that directly measure mobility at or near the surface of glassy polymers. These experiments indicate that enhanced mobility near the free surface can exceed bulk mobility by several orders of magnitude and extend for several nanometers into the bulk polymer. Enhanced mobility near the free surface allows a qualitative understanding of many of the observations of a reduced glass transition temperature Tg in thin films. For thin films, knowledge of Tg by itself is less useful than for bulk materials. Because of this, new experimental methods that directly measure important material properties are being developed.
Book•
10 Nov 2014
TL;DR: In this paper, the authors define and define surface and interface physics: its definition and importance, preparation of well-defined Surfaces, Interfaces and Thin Films, morphology and structure of surfaces, interfaces and thin films.
Abstract: Surface and Interface Physics: Its Definition and Importance.- Preparation of Well-Defined Surfaces, Interfaces and Thin Films.- Morphology and Structure of Surfaces, Interfaces and Thin Films.- Scattering from Surfaces and Thin Films.- Surface Phonons.- Electronic Surface States.- Space-Charge Layers at Semiconductor Inferfaces.- Metal-Semiconductor Junctions and Semiconductor Heterostructures.- Collective Phenomena at Interfaces:Superconductivity and Ferromagnetism.- Adsorption on Solid Surfaces.
TL;DR: The addition of Br in the perovskite structure was demonstrated to improve slightly the lifetime of the devices and the efficiencies of all devices tested remained at least at the 80% of the initial value 1 month after their preparation.
Abstract: We report on the preparation of a series of solution-processed perovskite solar cells based on methylammonium (MA) lead halide derivatives, MAPbX3, which show tunable optical properties depending on the nature and ratio of the halides employed (X = Cl, Br, and I). Devices have been prepared with different cell architecture, thin film, and mesoporous scaffold (TiO2 and Al2O3). We have analyzed different sample sets focusing on the characterization of the charge recombination by means of impedance spectroscopy (IS). On the one hand, our study discloses that the insertion of both Cl and Br in the perovskite lattice reduces the charge recombination rates in the light absorber film, thus determining the open circuit voltage (Voc) of the device. The samples prepared on a mesoporous Al2O3 electrode present lower charge recombination rates than those devices prepared on mesoporous TiO2. Furthermore, the addition of Br in the perovskite structure was demonstrated to improve slightly the lifetime of the devices; in fact, the efficiencies of all devices tested remained at least at the 80% of the initial value 1 month after their preparation. These results highlight the crucial role of the charge-recombination processes on the performance of the perovskite solar cells and pave the way for further progress on this field.
TL;DR: In this article, a laser molecular beam epitaxy technology was employed to deposit β-gallium oxide (β-Ga2O3) on (0001) sapphire substrates.
Abstract: Laser molecular beam epitaxy technology has been employed to deposit β-gallium oxide (β-Ga2O3) on (0001) sapphire substrates. After optimizing the growth parameters, (2¯01)-oriented β-Ga2O3 thin film was obtained. Ultraviolet-visible absorption spectrum demonstrates that the prepared β-Ga2O3 thin film shows excellent solar-blind ultraviolet (UV) characteristic with a band gap of 5.02 eV. A prototype photodetector device with a metal-semiconductor-metal structure has been fabricated using high quality β-Ga2O3 film. The device exhibits obvious photoresponse under 254 nm UV light irradiation, suggesting a potential application in solar-blind photodetectors.
TL;DR: Raman and photoluminescence spectroscopy confirm the high quality of as-grown MoSe2 in optics, and electronic transport measurements highlight the potential applications of the sample in nanoelectronics.
Abstract: We present successful synthesis of large area atomically thin MoSe2 films by selenization of MoO3 in a vapor transport chemical vapor deposition (CVD) system. The homogeneous thin film can reach an area of 1 × 1 cm2 consisting primarily of monolayer and bilayer MoSe2 film. Scanning transmission electron microscopy (STEM) images reveal the highly crystalline nature of the thin film and the atomic structure of grain boundaries in monolayers. Raman and photoluminescence spectroscopy confirm the high quality of as-grown MoSe2 in optics, and electronic transport measurements highlight the potential applications of the sample in nanoelectronics.