A study on enhancing EUV resist sensitivity

We have carried out extensive investigations of the gas phase composition during diamond CVD in a conventional hydrogen rich environment. Absolute densities of CH/sub 3/, CH, and the hydrogen dissociation ratio have been measured in hydrocarbon-based plasma-enhanced CVD (PECVD) and hot filament CVD (HFCVD) environments. Additional species, C/sub 2/H/sub 2/ and C/sub 6/H/sub 6/ have been studied in hot filament activated diamond growth. High sensitivity white light absorption spectroscopy has been able to provide a quantitative description of the densities of all the single carbon hydrocarbon species in hydrogen-rich diamond growth. The most extensively studied species is the CH/sub 3/ radical. This radical is the key to the diamond growth mechanism in hydrogen-rich diamond CVD. As with many other polyatomic species, the excited electronic levels of CH/sub 3/ all dissociate. Consequently, laser-induced fluorescence measurements are not possible with this species. Prior to the work with high sensitivity white light absorption spectroscopy, the CH/sub 3/ radical had been detected using resonantly-enhanced multiphoton ionization (REMPI), infrared diode laser absorption and near threshold ionization mass spectrometry. Compared with these techniques, high sensitivity white light absorption spectroscopy is considerably simpler and more sensitive, even deep in the ultraviolet.

Developing robust ultrahigh light absorption coatings has been a significant challenge, limited by the absorption‐adhesion tradeoff. Herein, a robust carbon‐based coating with omnidirectional broadband high absorption is designed and fabricated using a one‐step spray method. A novel rapidly cross‐linking resin is utilized as the binder to enhance adhesion. Beyond leveraging the intrinsic optical properties of carbon absorbents, the construction of a micro‐nano multi‐scale trapping structure is crucial for achieving high absorption efficiency in the coating. Innovatively, an inorganic matting agent is introduced to further diminish reflection by scattering incident light. The resulting ultrablack coating demonstrates good adhesion and an exceptionally high integral light absorption of 99.34% within the wavelength range of 1500–1800 nm, marking the highest reported value for binder‐incorporated spray coatings to date. This robust coating also exhibits outstanding thermal stability and resistance to vacuum thermal cycling and vibration. Furthermore, the application of the ultrablack coating via spraying is scalable and can be readily adapted to the surfaces or interiors of complex structural components made from diverse materials. The coating shows remarkable potential for solar energy harvesting and target stealth. This study presents a simple and efficient approach for developing robust ultrablack coatings suitable for widespread practical applications.

This study identifies the characteristics of water regions with negative normalized water-leaving radiance (nLw(λ)) values in the satellite observations of the Second-generation Global Imager (SGLI) sensor aboard the Global Change Observation Mission–Climate (GCOM-C) satellite. SGLI Level-2 data, along with atmospheric and in-water optical properties measured by the sun photometers in the AErosol RObotic NETwork-Ocean Color (AERONET-OC) from 26 sites globally, are utilized in this study. The focus is particularly on Tokyo Bay and the Ariake Sea, semi-enclosed water regions in Japan where previous research has pointed out the occurrence of negative nLw(λ) values due to atmospheric correction with SGLI. The study examines the temporal changes in atmospheric and in-water optical properties in these two regions, and identifies the characteristics of regions prone to negative nLw(λ) values due to atmospheric correction by comparing the optical properties of these regions with those of 24 other AERONET-OC sites. The time series results of nLw(λ) and the single-scattering albedo (ω(λ)) obtained by the sun photometers at the two sites in Tokyo Bay and Ariake Sea, along with SGLI nLw(λ), indicate the occurrence of negative values in SGLI nLw(λ) in blue band regions, which are mainly attributed to the inflow of absorptive aerosols. However, these negative values are not entirely explained by ω(λ) at 443 nm alone. Additionally, a comparison of in situ nLw(λ) measurements in Tokyo Bay and the Ariake Sea with nLw(λ) values obtained from 24 other AERONET-OC sites, as well as the inherent optical properties (IOPs) estimated through the Quasi-Analytical Algorithm version 5 (QAA_v5), identified five sites—Gulf of Riga, Long Island Sound, Lake Vanern, the Tokyo Bay, and Ariake Sea—as regions where negative nLw(λ) values are more likely to occur. These regions also tend to have lower nLw(λ) values at shorter wavelengths. Furthermore, relatively high light absorption by phytoplankton and colored dissolved organic matter, plus non-algal particles, was confirmed in these regions. This occurs because atmospheric correction processing excessively subtracts aerosol light scattering due to the influence of aerosol absorption, increasing the probability of the occurrence of negative nLw(λ) values. Based on the analysis of atmospheric and in-water optical measurements derived from AERONET-OC in this study, it was found that negative nLw(λ) values due to atmospheric correction are more likely to occur in water regions characterized by both the presence of absorptive aerosols in the atmosphere and high light absorption by in-water substances.

Canfieldite Ag8SnS6 nanoparticles with high light absorption coefficient and quantum yield

Water reduction to hydrogen (H2) by solar light is a green and sustainable approach to solve the energy crisis. However, conventional semiconductors usually suffer from low light absorbance and high charge recombination rate, which largely suppressed the application of this technology. Here, carbon nitride nanotubes (C3N4 NTs) prepared via morphological transformation method were utilized as photocatalysts for H2 production. The dispersed C3N4 nanosheets with few layers, suitable temperature difference and heating atmosphere in the process are of great importance to the formation of well-structured nanotubes. The C3N4 NTs demonstrates high visible light absorbance and efficient charge transfer kinetics, as evidenced by the UV–vis diffuse reflectance and photoluminescence spectra. In the absence of cocatalysts, a H2 generation rate of 2.69 µmol·h−1·mg−1 was achieved with an apparent quantum efficiency of 2.16% at 420 nm wavelength. Keywords: Carbon nitride nanotubes, Preparation effects, Photocatalysis, H2 production

Titanium dioxide (TiO2) is one of the most abundant compounds in our planet. It is cheap, non- toxic, highly chemically and thermally stable semiconductor material. Titanium dioxide nanoparticles (TiO2-NPs) show high visible light transparency combined with high UV light absorption. However, altering the particle size and crystalline structure of TiO2-NPs influences the absorption range, adsorption of dye molecules and electron transfer rate at the surface. Unfortunately, TiO2-NPs suffer high electron/hole recombination rates. Therefore, an ordered superstructure consisting of nanoparticles on the scale of nanometers to several micrometers is proposed titanium dioxide mesocrystals (TiO2-MCs). In this work, we represent a new and facile way to fabricate TiO2-MCs with spherical structure by sol-gel method. We were able to fabricate spherical TiO2-NCs with narrow size distribution by controlling the hydrolysis conditions. The effect of air annealing on the morphology, size shrinkage, and phase transition of the nanoparticles was studied by scanning electron microscopy, X-ray diffraction, and Raman spectroscopy. Also, the fabricated TiO2-MCs showed exceptional photoactivity compared to their Degussa p-25 nanoparticles counterparts upon their use in water splitting cells.

The indium gallium nitride (InGaN) ternary alloy system offers an ideal semiconductor basis as a light absorber for driving chemical reactions such as the oxygen evolution reaction (OER) and hydrogen evolution reaction (HER). It is a direct bandgap semiconductor whose energy can be tuned for optimal solar absorption and overcoming kinetic overpotential losses, it can be grown epitaxially as a single crystal for high material quality, and it exhibits relatively high corrosion resistance in aqueous solutions for a III-V material. In this work, we report on the design, synthesis, and photoelectrochemical studies of InGaN in an anode configuration with a goal of using this material as a light absorber basis for driving solar fuels reactions such as the OER and the HER. Studies are shown reporting on how reactive vapor synthesis of GaN and InN with different structuring affects the light conversion properties and band diagram electrostatics in an electrochemical junction with ferrocene and cobaltocene redox pairs. This structure is extended to thin films of GaN and InGaN grown by molecular beam epitaxy for high efficiency light conversion, with the resulting electrochemical junction also made with ferrocene and cobaltocene. The effects of ternary alloying, doping, and the two different c-plane polarities (III-polar and V-polar) on the junction are investigated using the same electrochemical junction to evaluate the light conversion properties in relation to the electrostatics; specifically, tuning the bandgap energy for optimal light absorption, determining the c-plane polarity configuration for the electric fields to have the correct band alignment, and incorporating silicon doping to create a conductive substrate. The combination of these engineering techniques extends the depletion region of the active layer for high efficiency light absorption as similarly demonstrated for epitaxial phosphide films [1], and is utilized toward the goal of high performance solar energy conversion. [1] V. Parameshwaran, X. Xu, and B. Clemens, Journal of the Electrochemical Society, vol. 163, no. 8, pg. H714-H721 (2016).

This study analyzed the electronic and optical properties of pentacene derivatives chemically modified by adding nitro and amine groups at different positions on the molecular structure. The study aimed to understand the impact of these modifications on electronic and optical applications, focusing on improving performance in organic electronic devices and solar cells. The results showed that adding nitro groups as electron acceptors and amine groups as electron donors reduces the energy gap and increases the chemical activity of the molecules. It was also observed that changing the positions of these groups significantly affects the polar moment, reflecting changes in the charge distribution within the molecules. In terms of optical properties, the modified molecules showed high light absorption in the visible region of the electromagnetic spectrum, making them promising candidates for organic solar cell applications, where high light absorption efficiency is a prerequisite for these applications. All calculations were performed using the Gaussian 09 software package. The study included molecular geometry optimization using density functional theory (DFT) with the B3LYP hybrid functional and 6-31G(d,p) basis set. Electronic properties, such as the highest occupied molecular orbital HOMO and lowest unoccupied molecular orbital LUMO energy levels, and the energy gap between them were calculated to evaluate the stability and chemical activity. Time-dependent density functional theory (TD-DFT) was used to analyze the optical properties and light absorption. In addition, fixed points were confirmed by vibrational frequency analysis to ensure that the optimized molecular structures represent stable states. The study also included a polar moment calculation to evaluate the effect of chemical modifications on the polarity of the molecules.

Design of expanded graphite/poly (vinyl alcohol) hierarchically porous carbon foam by a controllable vacuum foaming strategy for efficient solar evaporation

Transition metal dichalcogenides (TMDCs) have been proposed as light absorber materials for ultrathin solar cells. These materials are characterized by their strong light-matter interaction and the possibility to be assembled into devices at room temperature. Here, we model the optical absorptance of an ultrathin MoS2 absorber embedded in different designs of a 1D optical cavity. We find that up to 87% of the photons contained in the 300-700 nm range of the AM1.5G spectrum can be absorbed employing MoS2 absorbers as thin as 10 nm sandwiched between a h-BN top layer and an optically thick Ag reflector. An h-BN/MoS2/h-BN/Ag cavity produces 0.89 average absorptance for a 57-nm-thick MoS2 slab and it also maximizes the absorption of extremely thin absorbers, between 1 and 9 nm. We also model a possible large-scale device on a glass substrate combined with indium-tin oxide (ITO) whose absorptance is comparable to the other presented structures. The high broadband absorption in these light-trapping structures is caused by the amplification of the zeroth Fabry-Perot interference mode. This study demonstrates that light absorption in ultrathin solar cells based on nanometric TMDC absorbers can compete with conventional photovoltaic technology and provides different simple optical designs to choose from depending on the electronic characteristics of the TMDC junction.

The practical application of solar energy harvesting urgently calls for the facile preparation of high‐performance ultrablack surfaces with broadband and omnidirectional light absorption performance; however, some roadblocks still need to meet these requirements simultaneously. Herein, cone‐array ultrablack (CAUB) surfaces are prepared by combining feasible template replication and blade coating techniques. The elaborate micro‐sized cone structure and high absorptive materials (polydimethylsiloxane@carbon black, PDMS@CB) offer the CAUB extremely high, broadband, and omnidirectional light absorption over the solar spectrum with an average absorbance of 99.35%. Under one sun irradiation, the CAUB can efficiently absorb solar energy, reaching a surface temperature as high as 75 °C. A solar‐thermal‐electric generator (STEG) made from the CAUB film demonstrates real‐time solar‐heat‐electric conversion, achieving a high output power density of 330 µW cm−2. The CAUB film possesses excellent water repellency, flexibility, chemical solvent resistance, and potential for large‐scale production, satisfying the application requirements of solar energy harvesting and utilization.

ConspectusThe past decade has witnessed the great success and rapid development of halide perovskite materials in photovoltaics and light-emitting devices, which is due to the inherently high photoluminescence quantum yield, long carrier diffusion length, high light absorption coefficient, great defect tolerance, and remarkable tunability. For example, the record efficiency of perovskite solar cells has ramped up to 25.5%, comparable to single-crystal silicon solar cells. In combination with the facile solution processing, perovskite solar cells have gained tremendous attention and interest from both academia and the photovoltaic market. Moreover, as a newly emerging class of semiconductors with excellent properties and low manufacturing cost, it is also promising and meaningful to explore new applications beyond optoelectronic devices, such as transistors, lasers, and memory devices. To this end, the integration of different halide perovskites into epitaxial heterostructures provides an ideal option. On the other hand, from the perspective of fundamental studies, halide perovskite heterostructures also provide a platform to directly visualize ion migration and to study the charge transfer behavior and anomalous exciton phenomena, etc.The aim of our Account is to summarize the synthetic strategies to achieve halide perovskite epitaxial heterostructures and to highlight the effective routes to stabilize halide perovskites and heterostructures. We focus this Account on two-dimensional (2D) halide perovskites and emphasize the important roles the organic ligands play. Specifically, we discuss our recent findings on the incorporation of conjugated organic ligands into 2D halide perovskites leading to enhanced thermal and environmental stability and suppressed halide interdiffusion in the corresponding heterostructures. Molecular dynamics simulation and low-dose aberration corrected transmission electron microscopy were used as powerful tools to unveil and elucidate the working mechanism of stabilization and anion interdiffusion suppression. Following this strategy, diverse halide perovskite heterostructures between different halides, metals, or organic cations and more complex heterostructures and superlattices can be realized. Due to the reduced ion motion and improved stability, the interface of the heterostructures can be kept quite sharp. In the outlook of this Account, we discuss the challenges and a few promising directions with a special focus on the vertical van der Waals (vdW) heterostructures, which are expected to offer more flexibility in heterostructure integration and more opportunities in studying the charge transfer and carrier interaction along the out-of-plane direction. Moreover, the existence of semiconducting organic ligands provides new insights to tune the carrier and exciton behaviors along both in-plane and out-of-plane directions.

Low‐dimensional van der Waals materials (vdWMs) have attracted worldwide interest on account of numerous advantages including self‐passivated surface, high carrier mobility, excellent flexibility, etc. Among multiple vdWMs, Sb2Se3 stands out due to its high light absorption coefficient, environmentally friendly components, excellent stability, and abundant reserve. However, limited effective wavelength range and unscalable preparation have been obstinate issues standing in the way of further development. Herein, pulsed‐laser deposition (PLD) has been developed for synthesizing Sb2Se3 nanofilms, and wafer‐scale deposition has been realized. The PLD‐derived Sb2Se3 photodetector demonstrates broadband photoresponse across UV to NIR. First‐principles calculations have determined that this is because the formation of Se vacancies can result in a reduction of the bandgap. Upon 635 nm illumination, an optimal responsivity of 2.68 A W−1 has been achieved, corresponding to an external quantum efficiency of 524% and a specific detectivity of 1.34 × 1012 Jones. Furthermore, the device manifests a short response/recovery time of ≈2/1 ms. Proof‐of‐concept broadband imaging as well as fitness monitoring (respiratory rate & heart rate) have been realized. Profited from the scalable preparation, an array of Sb2Se3 photodetectors have been produced, exhibiting qualified device‐to‐device variation. On the whole, this study has depicted an attractive landscape for next‐generation integrated optoelectronics.

Chapter 9 - Lead-free Metal Halide Perovskites for Solar Energy

Aim & Scope: Metal halide perovskitehave been regarded as promising classes of materials for photovoltaics and optoelectronic devices, owing to the unique characteristics, such as long charge carrier diffusion lengths, precise tunable bandgaps, high light absorption coefficients, and high defect tolerance. Research on perovskite in the fields including photovoltaics, light-emitting diodes, lasers, X-ray imaging, and photodetectors has been gaining increasingly interest over the past years. Up to now, the efficiency of perovskite solar cells has grown from 3.8% in single-junction solar cells in 2009 to more than 25%, catching up the efficiency level of commercial silicon cells. Up to now, the key issues of perovskite photovoltaics and optoelectronic devices have become the stability, performance and large-scale production. This requires optimization of the film morphology, interface, device structure and the fabrication process. A lot work has been done on this issue and has made remarkable progress. We kindly invite you to submit a manuscript(s) for this Special Issue. Full papers, communications, and reviews are all welcome.