Tunability of MoO<sub>3</sub> Thin-Film Properties Due to Annealing in Situ Monitored by Hard X-ray Photoemission

Liao, Xian; Jeong, Ah Reum; Wilks, Regan G.; Wiesner, S.; Rusu, M.; Félix, Roberto; Xiao, Ting; Hartmann, Claudia; Bär, Marcus

doi:10.1021/acsomega.9b01027

Cited by 29 publications

(17 citation statements)

References 31 publications

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“…These peaks indicate negligible oxygen vacancies in the synthesized α-MoO 3 thin films. [23] These investigations substantiate the fact that the chemical and structural properties of our fabricated rectangular-shaped α-MoO 3 thin films using thermal physical deposition technique are as expected.…”

Section: Resultssupporting

confidence: 85%

High Temperature Mid‐IR Polarizer via Natural In‐Plane Hyperbolic Van der Waals Crystals

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Dixit

Singh

et al. 2021

Advanced Optical Materials

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anisotropy is invoked by lithographic patterning, natural hyperbolicity of these vdW materials is attributed to structural anisotropy of crystal unit cell. In particular, hexagonal boron nitride (h-BN), [3] α-phase molybdenum trioxide (α-MoO 3 ) [1,6] and α-phase vanadium pentoxide (α-V 2 O 5 ) [2] are natural hyperbolic materials (NHMs) which exhibit Reststrahlen Bands (RBs)the spectral region between longitudinal optical (LO) and transverse optical (TO) phonons-in the mid-IR spectral region and show hyperbolicity due to interaction of optical phonons with photons (lightmatter interaction). Phonons have a relatively long lifetime compared to plasmons resulting in lower optical losses than their analogous plasmonic-based metamaterials [7][8][9] in which photons are coupled with plasmons. Many NHMs [1][2][3] exhibit hyperbolic anisotropy in mid-IR spectral region (3-30 µm) which has diverse applications like polarized IR imaging, [10] molecular sensing, [11,12] free space communication, [13] and quantum interference. [14] Unlike h-BN, which possesses uniaxial hyperbolic anisotropy (i.e., ε xx = ε yy ≠ ε zz ), α-MoO 3 exhibits in-plane hyperbolic anisotropy (i.e., ε xx ≠ ε yy ≠ ε zz ) which is particularly beneficial for planar mid-IR optical devices. [15,16] With this motivation, there has been recent interest in developing flat optics based on vdW layered materials which can be integrated with chip-scale platforms using vdW integration, operational at room temperature, and does not involve complex lithographic fabrication techniques. [17][18][19][20] We present an application of α-MoO 3 in the mid-IR spectral region, that is, from 545-1000 cm −1 (around 10-18 µm), as a thin film polarizer that reflects the light with one state of polarization while transmitting the light with its orthogonal state of polarization. Here, single-crystal α-MoO 3 thin films are synthesized using physical vapor deposition (schematically shown in Figure 1a) and are transferred on top of potassium bromide (KBr) window, purchased from Edmund Optics, using mechanical exfoliation technique. In-plane anisotropy of the synthesized α-MoO 3 thin film is confirmed using polarizationresolved Raman spectroscopy. We optimize the mid-IR optical responses of α-MoO 3 , mainly transmittance and reflectance, as a function of the thickness. Optimum thickness of α −MoO 3 based IR polarizer is found to lie in the range of 2.5-3.5 µm for which the extinction ratio (ER) is obtained more than 7.5Integration of conventional mid to long-wavelength infrared (IR) polarizers with chip-scale platforms is restricted by their bulky size and complex fabrication. Van der Waals materials based polarizer can address these challenges due to its nonlithographic fabrication, ease of integration with chip-scale platforms, and room temperature operation. In the present work, mid-IR optical response of the sub-wavelength thin films of α-phase molybdenum trioxide (α-MoO 3 ) is investigated for application toward high temperature mid-IR transmission and reflection type thin film...

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Section: Resultssupporting

confidence: 85%

High Temperature Mid‐IR Polarizer via Natural In‐Plane Hyperbolic Van der Waals Crystals

Sahoo

Dixit

Singh

et al. 2021

Advanced Optical Materials

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“…Lee et al reported that MoO x HTL-based OSCs are more stable at a high operating temperature near 300-420 K than PEDOT:PSS [90]. Therefore, there is much research in strategies to optimize the solution-processing methods and the film properties of MoO 3 [91][92][93]. Bortoti et al obtained the orthorhombic phase of MoO 3 (α-MoO 3 ) by refluxing MoS 2 in HNO 3 and H 2 SO 4 as the oxidant media, followed by heating at 120 • C for 10 min to evaporate the solvent [94].…”

Section: Hole-transporting Materials As Htls In Oscsmentioning

confidence: 99%

Recent Advances in Hole-Transporting Layers for Organic Solar Cells

et al. 2022

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Global energy demand is increasing; thus, emerging renewable energy sources, such as organic solar cells (OSCs), are fundamental to mitigate the negative effects of fuel consumption. Within OSC’s advancements, the development of efficient and stable interface materials is essential to achieve high performance, long-term stability, low costs, and broader applicability. Inorganic and nanocarbon-based materials show a suitable work function, tunable optical/electronic properties, stability to the presence of moisture, and facile solution processing, while organic conducting polymers and small molecules have some advantages such as fast and low-cost production, solution process, low energy payback time, light weight, and less adverse environmental impact, making them attractive as hole transporting layers (HTLs) for OSCs. This review looked at the recent progress in metal oxides, metal sulfides, nanocarbon materials, conducting polymers, and small organic molecules as HTLs in OSCs over the past five years. The endeavors in research and technology have optimized the preparation and deposition methods of HTLs. Strategies of doping, composite/hybrid formation, and modifications have also tuned the optical/electrical properties of these materials as HTLs to obtain efficient and stable OSCs. We highlighted the impact of structure, composition, and processing conditions of inorganic and organic materials as HTLs in conventional and inverted OSCs.

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“…Thus, it cannot be excluded that the extended exposure of the Cu x Ni 1− x O y library to X-rays (in total: several 100 hours) altered some of its properties. However, no reduction or ‘metallization’, as reported for other metal oxides like WO 3 14 and MoO 3 , 15 was observed during the measurements. In contrast, the Cu 2p data of measurement spots 7 and 163 (shown in S.I.…”

Section: Methodsmentioning

confidence: 57%

Prospect of making XPS a high-throughput analytical method illustrated for a Cu_xNi_1−xO_y combinatorial material library

et al. 2022

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Tunability of MoO₃ Thin-Film Properties Due to Annealing in Situ Monitored by Hard X-ray Photoemission

Cited by 29 publications

References 31 publications

High Temperature Mid‐IR Polarizer via Natural In‐Plane Hyperbolic Van der Waals Crystals

High Temperature Mid‐IR Polarizer via Natural In‐Plane Hyperbolic Van der Waals Crystals

Recent Advances in Hole-Transporting Layers for Organic Solar Cells

Prospect of making XPS a high-throughput analytical method illustrated for a Cu_xNi_1−xO_y combinatorial material library

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Tunability of MoO3 Thin-Film Properties Due to Annealing in Situ Monitored by Hard X-ray Photoemission

Cited by 29 publications

References 31 publications

High Temperature Mid‐IR Polarizer via Natural In‐Plane Hyperbolic Van der Waals Crystals

High Temperature Mid‐IR Polarizer via Natural In‐Plane Hyperbolic Van der Waals Crystals

Recent Advances in Hole-Transporting Layers for Organic Solar Cells

Prospect of making XPS a high-throughput analytical method illustrated for a CuxNi1−xOy combinatorial material library

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Tunability of MoO₃ Thin-Film Properties Due to Annealing in Situ Monitored by Hard X-ray Photoemission

Prospect of making XPS a high-throughput analytical method illustrated for a Cu_xNi_1−xO_y combinatorial material library