High Resolution Depth Profiling Research Articles

Underwater Single-Photon 3D Reconstruction Algorithm Based on K-Nearest Neighbor

The high sensitivity and picosecond time resolution of single-photon avalanche diodes (SPADs) can improve the operational range and imaging accuracy of underwater detection systems. When an underwater SPAD imaging system is used to detect targets, backward-scattering caused by particles in water often results in the poor quality of the reconstructed underwater image. Although methods such as simple pixel accumulation have been proven to be effective for time–photon histogram reconstruction, they perform unsatisfactorily in a highly scattering environment. Therefore, new reconstruction methods are necessary for underwater SPAD detection to obtain high-resolution images. In this paper, we propose an algorithm that reconstructs high-resolution depth profiles of underwater targets from a time–photon histogram by employing the K-nearest neighbor (KNN) to classify multiple targets and the background. The results contribute to the performance of pixel accumulation and depth estimation algorithms such as pixel cross-correlation and ManiPoP. We use public experimental data sets and underwater simulation data to verify the effectiveness of the proposed algorithm. The results of our algorithm show that the root mean square errors (RMSEs) of land targets and simulated underwater targets are reduced by 57.12% and 23.45%, respectively, achieving high-resolution single-photon depth profile reconstruction.

Underwater Single-Photon 3D Reconstruction Algorithm Based on K-Nearest Neighbor.

The high sensitivity and picosecond time resolution of single-photon avalanche diodes (SPADs) can improve the operational range and imaging accuracy of underwater detection systems. When an underwater SPAD imaging system is used to detect targets, backward-scattering caused by particles in water often results in the poor quality of the reconstructed underwater image. Although methods such as simple pixel accumulation have been proven to be effective for time-photon histogram reconstruction, they perform unsatisfactorily in a highly scattering environment. Therefore, new reconstruction methods are necessary for underwater SPAD detection to obtain high-resolution images. In this paper, we propose an algorithm that reconstructs high-resolution depth profiles of underwater targets from a time-photon histogram by employing the K-nearest neighbor (KNN) to classify multiple targets and the background. The results contribute to the performance of pixel accumulation and depth estimation algorithms such as pixel cross-correlation and ManiPoP. We use public experimental data sets and underwater simulation data to verify the effectiveness of the proposed algorithm. The results of our algorithm show that the root mean square errors (RMSEs) of land targets and simulated underwater targets are reduced by 57.12% and 23.45%, respectively, achieving high-resolution single-photon depth profile reconstruction.

Deconvolution of high-resolution depth profiling data with sputtering induced roughness for reconstruction of nano-layer structure

In this paper, a deconvolution method is proposed to obtain the original nano-layer structure directly from measured high-resolution depth profiling data with sputtering induced roughness. This method combines the Mixing-Roughness-Information (MRI) depth resolution function and the Total Variation (TV)-Tikhonov regularization. The regularization parameter of α that influences strongly the error and stability of the deconvolution result is optimized based on the L-curve criterion by the simulated annealing algorithm. The simulation results show that this method can be used to effectively obtain the original nano-layer structure even if the depth profiling data contains noise and/or sputtering induced roughness. Subsequently, as an example, the original multilayer structure of 4 × Si(15 nm)/Al (15 nm) is obtained directly from measured AES depth profiling data and the obtained roughness values accordingly at the depths of the middle of the first Al sublayer and of the last Al sublayer agree well with the ones measured by AFM.

Three-dimensional hard X-ray ptychographic reflectometry imaging on extended mesoscopic surface structures

Many nanodevices and quantum devices, with their sizes often spanning from millimeters down to sub-nanometer, have intricate low-dimensional, non-uniform, or hierarchical structures on surfaces and interfaces. Since their functionalities are dependent on these structures, high-resolution surface-sensitive characterization becomes imperative to gain a comprehensive understanding of the function–structure relationship. We thus developed hard x-ray ptychographic reflectometry imaging, a new technique that merges the high-resolution two-dimensional imaging capabilities of hard x-ray ptychography for extended objects, with the high-resolution depth profiling capabilities of x-ray reflectivity for layered structures. The synergy of these two methods fully leverages both amplitude and phase information from ptychography reconstruction to not only reveal surface topography and localized structures, such as shapes and electron densities, but also yields statistical details, such as interfacial roughness that is not readily accessible through coherent imaging solely. The hard x-ray ptychographic reflectometry imaging is well-suited for three-dimensional imaging of mesoscopic samples, particularly those comprising planar or layered nanostructures on opaque supports, and could also offer a high-resolution surface metrology and defect analysis on semiconductor devices, such as integrated nanocircuits and lithographic photomasks for microchip fabrications.

Optimization of deconvoluted parameter for the quantification of high-resolution SIMS depth profiles

It is demonstrated in this paper that the searching step τ in the TV-Tikhonov algorithm plays an important role for determining the original layer structure directly from measured high-resolution depth profiling data. The optimization of τ is very necessary for obtaining a reliable deconvoluted result. Considering a large increase of simulated data points by decreasing the depth interval for quantification of high-resolution depth profiling data, the optimization of τ is performed simply by one-dimensional search algorithm. Furthermore, the noise effects from “measured” depth profiling data on the deconvoluted profile with different optimal τ values are also quantitatively evaluated. Finally, as examples, the measured SIMS depth profiling data of the two In nano-layers embedded in InGaAs thin films and the 28Si/30Si isotope nano-superlattices are deconvoluted directly and the respective original layer structures are obtained accordingly.

Unveiling the parasitic-reaction-driven surface reconstruction in Ni-rich cathode and the electrochemical role of Li2CO3

Nickel-rich transition-metal oxides are widely regarded as promising cathode materials for high-energy-density lithium-ion batteries for emerging electric vehicles. However, achieving high energy density in Ni-rich cathodes is accompanied by substantial safety and cycle-life obstacles. The major issues of Ni-rich cathodes at high working potentials are originated from the unstable cathode-electrolyte interface, while the underlying mechanism of parasitic reactions towards surface reconstructions of cathode materials is not well understood. In this work, we controlled the Li2CO3 impurity content on LiNi0.83Mn0.1Co0.07O2 cathodes using air, tank-air, and O2 synthesis environments. Home-built high-precision leakage current and on-line electrochemical mass spectroscopy experiments verify that Li2CO3 impurity is a significant promoter of parasitic reactions on Ni-rich cathodes. The rate of parasitic reactions is strongly correlated to Li2CO3 content and severe performance deterioration of Ni83 cathodes. The post-mortem characterizations via high-resolution transition electron microscope and X-ray photoelectron spectroscopy depth profiles reveal that parasitic reactions promote more Ni reduction and O deficiency and even rock-salt phase transformation at the surface of cathode materials. Our observation suggests that surface reconstructions have a strong affiliation to parasitic reactions that create chemically acidic environment to etch away the lattice oxygen and offer the electrical charge to reduce the valence state of transition metal. Thus, this study advances our understanding on surface reconstructions of Ni-rich cathodes and prepares us for searching for rational strategies.

Cable bacteria regulate sedimentary phosphorus release in freshwater sediments

Previous studies have demonstrated that e-SOx can regulate the sedimentary release of phosphorus (P) in brackish and marine sediments. When e-SOx is active, an iron (Fe) and manganese (Mn) oxide rich layer is formed near the sediment surface, which prevents P release. When e-SOx becomes inactive, the metal oxide layer is reduced via sulfide-mediated dissolution, and P is subsequently released to the water column. Cable bacteria have been shown to also occur in freshwater sediments. In these sediments, sulfide production is limited, and the metal oxide layer would thus dissolve less efficiently, leaving the P trapped at the sediment surface. This lack of an efficient dissolution mechanism implies that e-SOx could play an important role in the regulation of P availability in eutrophied freshwater streams. To test this hypothesis, we incubated sediments from a eutrophic freshwater river to investigate the impact of cable bacteria on sedimentary cycling of Fe, Mn and P. High-resolution depth profiling of pH, O2 and ΣH2S complemented with FISH analysis and high-throughput gene sequencing showed that the development of e-SOx activity was closely linked to the enrichment of cable bacteria in incubated sediments. Cable bacteria activity caused a strong acidification in the suboxic zone, leading to the dissolution of Fe and Mn minerals and consequently a strong release of dissolved Fe2+ and Mn2+ to the porewater. Oxidation of these mobilized ions at the sediment surface led to the formation of a metal oxide layer that trapped dissolved P, as shown by the enrichment of P-bearing metal oxides in the top layer of the sediment and low phosphate in the pore and overlying water. After e-SOx activity declined, the metal oxide layer did not dissolve and P remained trapped at the surface. Overall, our results suggested cable bacteria can play an important role to counteract eutrophication in freshwater systems.

Corrosion behavior of a compositionally complex alloy utilizing simultaneous Al, Cr, and Ti passivation

The corrosion behavior of the Al0.3Cr0.5Fe2Mn0.25Mo0.15Ni1.5Ti0.3 compositionally complex dual-phase alloy was explored in a variety of electrolytes. Comparable corrosion resistance to 316L stainless steel and Ni-Cr binaries was observed in NaCl despite lower Cr concentrations. Individual elemental fates during corrosion were identified by combinations of in-situ atomic emission spectroelectrochemistry and ex-situ X-ray photoelectron spectroscopy with high-resolution surface analysis and depth profiling. A potentiostatically grown passive film was enriched in Al(III), Cr(III), Ti(IV), and Mo(VI). Al-Ti and Cr-Ti layers were suggested but significant Al, Cr, and Ti mixing was present. Proposed benefits of Al-Cr-Ti coexistence are addressed.

Microbially influenced tungsten mobilization and formation of secondary minerals in wolframite tailings

Wolframite [(Fe,Mn)WO4] tailings represent a hazardous waste that can pose a threat to the environment, humans, animals and plants. The present study aims to conduct a high-resolution depth profile characterization of wolframite tailings from Wolfram Camp, North Queensland, Australia, to understand the biogeochemical influences on W mobilization. Several indigenous Fe- and S-oxidizing bacteria (e.g., Streptococcus pneumoniae and Thiomonas delicata) in wolframite tailings were found highly associated with W, As, and rare earth elements. Biooxidation of metal sulfides, i.e., pyrite, molybdenite and bismuthinite, produced sulfuric acid, which accelerated the weathering of wolframite, mobilizing tungstate (WO42-). Using synchrotron-based X-ray fluorescence microscopy (XFM) and W L-edge X-ray absorption near-edge spectroscopy (µ-XANES) analysis, wolframite was initially transformed into Na- and Bi- tungstate as well as tungstic acid (partial weathering) followed by the formation of Ga- and Zn- tungstate after extensive weathering, i.e., the wolframite had disappeared. While W (VI) was the major W species in wolframite tailings, minor W(0) and W(II), and trace W(IV) were also detected. The major contaminant in the Wolfram Camp tailings was As. Though wolframite tailings are hazardous waste, the toxicity of W was unclear. Tungsten waste still has industrial value; apart from using them as substitution material for cement and glass production, there is interest in reprocessing W waste for valuable metal recovery. If the environmental benefits are taken into consideration, i.e., preventing the release of toxic metals into surrounding waterways, reprocessing may be economic.

Organochemical Characterization of Peat Reveals Decomposition of Specific Hemicellulose Structures as the Main Cause of Organic Matter Loss in the Acrotelm.

Peatlands store carbon in the form of dead organic residues. Climate change and human impact impose risks on the sustainability of the peatlands carbon balance due to increased peat decomposition. Here, we investigated molecular changes in the upper peat layers (0-40 cm), inferred from high-resolution vertical depth profiles, from a boreal peatland using two-dimensional 1H-13C nuclear magnetic resonance (NMR) spectroscopy, and comparison to δ13C, δ15N, and carbon and nitrogen content. Effects of hydrological conditions were investigated at respective sites: natural moist, drainage ditch, and natural dry. The molecular characterization revealed preferential degradation of specific side-chain linkages of xylan-type hemicelluloses within 0-14 cm at all sites, indicating organic matter losses up to 25%. In contrast, the xylan backbone, galactomannan-type hemicelluloses, and cellulose were more resistant to degradation and accumulated at the natural moist and drainage site. δ13C, δ15N, and carbon and nitrogen content did not correlate with specific hemicellulose structures but reflected changes in total carbohydrates. Our analysis provides novel insights into peat carbohydrate decomposition and indicates substantial organic matter losses in the acrotelm due to the degradation of specific hemicellulose structures. This suggests that variations in hemicellulose content and structure influence peat stability, which may have important implications with respect to climate change.

Elemental Depth Profiling of Intact Metal-Organic Framework Single Crystals by Scanning Nuclear Microprobe.

The growing field of MOF–catalyst composites often relies on postsynthetic modifications for the installation of active sites. In the resulting MOFs, the spatial distribution of the inserted catalysts has far-reaching ramifications for the performance of the system and thus needs to be precisely determined. Herein, we report the application of a scanning nuclear microprobe for accurate and nondestructive depth profiling of individual UiO-66 and UiO-67 (UiO = Universitetet i Oslo) single crystals. Initial optimization work using native UiO-66 crystals yielded a microbeam method which avoided beam damage, while subsequent analysis of Zr/Hf mixed-metal UiO-66 crystals demonstrated the potential of the method to obtain high-resolution depth profiles. The microbeam method was further used to analyze the depth distribution of postsynthetically introduced organic moieties, revealing either core–shell or uniform incorporation can be obtained depending on the size of the introduced molecule, as well as the number of carboxylate binding groups. Finally, the spatial distribution of platinum centers that were postsynthetically installed in the bpy binding pockets of UiO-67-bpy (bpy = 5,5′-dicarboxyy-2,2′-bipyridine) was analyzed by microbeam and contextualized. We expect that the method presented herein will be applicable for characterizing a wide variety of MOFs subjected to postsynthetic modifications and provide information crucial for their optimization as functional materials.

Use of Pulsed RF Glow Discharge Optical Emission Spectroscopy for the Study of Elemental Distribution of Li-NMC Cathode at Various State of Charge in Li-Ion Batteries

Glow discharge optical emission spectroscopy (GDOES) is an analytical technique that provides both a surface and depth profile of the elemental composition and distribution of solid or porous samples. Although GDOES is a destructive technique, it provides the advantage of being a high throughput technique that is highly sensitive to all elements from H to U and can provide high resolution (from nm to µm) depth profiles of elemental distributions in practically any sample. Previous works have investigated and optimized the operating parameters of using GDOES to study negative electrode materials and from the data gathered therein [1] we used 5% H2 in Ar gas in this study to increase sputtering rate of Li-NMC cathode materials and to increase sensitivity to Li in the sample to provide a more detailed elemental distribution. This study investigates the use of GDOES as a method for analyzing elemental and specifically lithium distribution in Li-NMC cathode materials in extreme depth and with validation from other techniques such as x-ray photoelectron spectroscopy (XPS) and x-ray fluorescence (XRF) and with additional morphological analysis of cells using x-ray computed tomography (X-ray CT).In this study coin cells were assembled in an Ar filled glovebox using a 15 mm diameter double sided graphite anode coated on a Cu current collector, 14 mm double sided NMC 111 cathode coated on an Al current collector, either a Celgard 3401 or 5550 separator, and 75 µL of 1M LiPF6–EC:EMC (3:7) electrolyte. The coin cells were then brought outside and EIS data was taken on the freshly made cells. They were then allowed to rest for 12 hours before going through a formation cycle at a C-rate of C/20. After the formation cycle, all cells went through 10 charge/discharge cycles at a C-rate of C/5. After these cycles EIS data was taken again and the cells were then charged to different states of charge (SOC) of 0, 25, 75, and 100% and again EIS data was taken after this. The cells were then brought back into the glovebox where they were de-crimped and disassembled. The electrodes were then rinsed in DMC and dried. They were then analyzed using XPS for surface analysis, XRF for elemental mapping, and X-ray CT for analysis of electrode morphology. Finally, they were analyzed using GDOES and the through thickness Li atomic distribution was plotted for the SOCs listed. An example of atomic concentration distribution of various elements for a SOC of 0% is shown by Figure 1. This study aims to validate the use of GDOES to generate accurate Li distribution profiles and elemental distributions in Li-NMC cathode materials.[1] H. Takahara, A. Kojyo, K. Kodama, T. Nakamura, K. Shono, Y. Kobayashi, M. Shikano, and H. Kobayashi, J. Anal. At. Spectrom., 29, 95–104 (2014). Figure 1

Ar gas cluster ion beam assisted XPS study of LiNbO3 Z cut surface

XPS combined with profiling by Ar2500+ gas cluster ion beam (GCIB) sputtering has been used to obtain new refined data on the polarization and processing-dependent Li/Nb ratio for the surface of a LiNbO3 single crystal. The most suitable GCIB parameters (normal incidence, 10 keV energy) and irradiation dose (less than or equal to 2.7 × 1016 ions/cm2) have been determined and employed to perform high resolution depth profile analysis without cluster ion-induced Li/Nb changes. The Li/Nb profiles obtained for Z cut wafers with positive and negative faces revealed the presence of two distinct regions. The initial 0.3 nm-thick region had a low Li/Nb ratio due to machining and leaching and did not show a dependence on the polarity direction. The next profile region had a constant Li/Nb ratio, which depended on the crystal polarity. The Li/Nb ratio for the Z+ surface of a wafer and a cleaved sample exceeded the values for the Z– surface of a wafer by 1.2 times. This result confirms theoretical predictions of a different stoichiometry for Z+ and Z– terminations and indicates the ability of GCIB to reach the surface condition that is close to the perfect termination.

Portraying Gradients of Structural Complexity in Coral Reefs Using Fine-Scale Depth Profiles

Structural complexity is an important feature to understand reef resilience abilities, through its role in mediating predator-prey interactions, regulating competition, and promoting recruitment. Most of the current methods used to measure reef structural complexity fail to quantify the contributions of fine and coarse scales of rugosity simultaneously, while other methods require heavy data computation. In this study, we propose estimating reef structural complexity based on high-resolution depth profiles to quantify the contributions of both fine and coarse rugosities. We adapted the root mean square of the deviation from the assessed surface profile (Rq) with polynomials. The efficiency of the proposed method was tested on nine theoretical cases and 50 in situ transects from South Taiwan, and compared to both the chain method and the visual rugosity index commonly employed to characterize reef structural complexity. The Rq indices proposed as rugosity estimators in this study consider multiple levels of reef rugosity, which the chain method and the visual rugosity index fail to apprehend. Furthermore, relationships were found between Rq scores and specific functional groups in the benthic community. Indeed, the fine scale rugosity of the South Taiwan reefs mainly comes from biotic components such as hard corals, while their coarse scale rugosity is essentially provided by the topographic variations that reflect the geological context of the reefs. This approach allows identifying the component of the rugosity that could be managed and which could, ultimately, improve strategies designed for conservation.

Robust real-time 3D imaging of moving scenes through atmospheric obscurant using single-photon LiDAR

Recently, time-of-flight LiDAR using the single-photon detection approach has emerged as a potential solution for three-dimensional imaging in challenging measurement scenarios, such as over distances of many kilometres. The high sensitivity and picosecond timing resolution afforded by single-photon detection offers high-resolution depth profiling of remote, complex scenes while maintaining low power optical illumination. These properties are ideal for imaging in highly scattering environments such as through atmospheric obscurants, for example fog and smoke. In this paper we present the reconstruction of depth profiles of moving objects through high levels of obscurant equivalent to five attenuation lengths between transceiver and target at stand-off distances up to 150 m. We used a robust statistically based processing algorithm designed for the real time reconstruction of single-photon data obtained in the presence of atmospheric obscurant, including providing uncertainty estimates in the depth reconstruction. This demonstration of real-time 3D reconstruction of moving scenes points a way forward for high-resolution imaging from mobile platforms in degraded visual environments.

Quantification of High Resolution Pulsed RF GDOES Depth Profiles for Mo/B4C/Si Nano-Multilayers

Pulsed-radio frequency glow discharge optical emission spectrometry (Pulsed-RF-GDOES) has exhibited great potential for high resolution (HR) depth profiling. In this paper, the measured GDOES depth profile of 60 × Mo (3 nm)/B4C (0.3 nm)/Si (3.7 nm) was quantified by employing the newly extended Mixing-Roughness-Information depth (MRI) model. We evaluated the influences of the thickness and sputtering rate on the depth profile of very thin layers. We demonstrated that a method using the full width at half maximum (FWHM) value of the measured time-concentration profile for determining the sputtering rate and the corresponding thickness was not reliable if preferential sputtering took place upon depth profiling.

Isotopic fingerprinting of biogeochemical processes and iron sources in the iron-limited surface Southern Ocean

Iron (Fe) is an essential micronutrient that limits primary productivity throughout the surface of the Southern Ocean. Here, we present the first high-resolution depth profiles for dissolved Fe and Fe isotope ratios (δ56Fe) from all major zones of the Southern Ocean, collected during the Antarctic Circumnavigation Expedition in austral summer 2017. Open-ocean surface waters are characterized by remarkably high δ56Fe values (up to +1.6‰) and very low Fe concentrations (<0.05 nmolkg−1). We attribute the elevated δ56Fe values above the ferricline to the effect of continuous shallow cycling processes (uptake, recycling, and binding of Fe to organic ligands), with only a very limited resupply of Fe from below. Below the ferricline, δ56Fe values approach ∼0‰ and remain constant down to our deepest samples at 1000 m, with no obvious isotope signal from regeneration. This overall pattern in δ56Fe is modified near islands, continental shelves and hydrothermal vents, where distinct δ56Fe signatures are associated with different Fe sources. Near the volcanic Balleny Islands, elevated surface Fe concentrations associated with low δ56Fe are indicative of reductive release of isotopically light Fe from sediments. Elevated δ56Fe values at depth near the Balleny seamount chain and near the East Scotia Arc may reflect distal hydrothermal influences, caused by fractionation associated with precipitation or the loss of specific phases of Fe during long-range transport. Sedimentary sources of isotopically light Fe on the Antarctic Peninsula are important for shelf waters. Long-distance transport of this sediment-derived Fe and its influence on surface waters are strongly dependent on the regional circulation, and may ultimately be the source of light Fe previously observed within Antarctic Intermediate Water in the Atlantic sector of the Southern Ocean.

Determination of parameters for self-stratification in bimodal colloidal coatings using Raman depth profiling

In waterborne mixtures of colloidal particles with differing sizes, the spontaneous stratification of one species of particle in a coating – driven by diffusiophoresis - offers the possibility to tailor the surface properties. However, despite strong research interest in stratification in recent years, the acceptable range of experimental parameters has not been fully explored, and the extent of stratification that is achievable has not yet been quantified. Here, we study the stratification of bimodal mixtures of waterborne polyurethane particles mixed with larger acrylic particles. We use ultra-low angle microtoming to prepare cross-sections of coating samples and analyse compositions quantitatively with Raman mapping. We use this method to obtain high-resolution depth profiles of the polyurethane phase in the coating with spacing between measurements corresponding to a few tens of nm. We experimentally test a model of diffusiophoresis and observe stratification when the processing parameters (evaporation rates, film thickness, and volume fraction of small particles) fall within the required range. Samples that exhibit stratification have top layer thicknesses on the order of tens of μm, which is a significant depth for exploitation in coatings aiming to modify surface properties. To guide the design of coatings in applications, we draw on the model to define the range of parameters in which self-stratification is expected. Our results provide a fundamental understanding that will enable the fabrication of tailored coatings in which the properties of the surface differ from the bulk material.

Partially Crystallized Ultrathin Interfaces between GaN and SiNx Grown by Low-Pressure Chemical Vapor Deposition and Interface Editing.

The formation mechanism of the partially crystallized ultrathin layer at the interface between GaN and SiNx grown by low-pressure chemical vapor deposition was analyzed based on the chemical components of reactants and products detected by high-resolution sputter depth profile analysis by X-ray photoelectron spectroscopy. A reasonable mass action equation for the formation of Si2N2O was proposed from the feasibility analysis of the Gibbs free energy changes of the reaction. The high-energy-activated Ga2O on the surface likely assists in the synthesis of the crystallized components. A well-defined 1ML θ-Ga2O3 transition interface was inserted into Si2N2O/GaN pure interface supercell slabs to edit the unsaturated state of the bonds. Low-density states can be achieved when the effective charges of the unsaturated atoms are adjusted to a certain interval.

Correlating chemical composition and optical properties of photochromic rare-earth oxyhydrides using ion beam analysis

We relate the photochromic response of rare-earth oxyhydride thin films (YHO, NdHO, GdHO and DyHO) synthesized by reactive magnetron sputtering to chemical composition. Depth profiles of the sample composition are extracted by a multi-method ion beam analysis approach. The total areal density of the thin films is deduced from Rutherford Backscattering Spectrometry while coincidence Time-of-Flight/Energy Elastic Recoil Detection Analysis provides depth-profiles of the film constituents. High-resolution depth profiles of the concentration of light species, i.e. hydrogen and oxygen, are additionally extracted from Nuclear Reaction Analysis and Elastic Backscattering Spectrometry, respectively. The photochromic response of the films is measured by optical transmission spectroscopy before and after illumination. We report photochromic properties for YHO, NdHO, GdHO and DyHO for chemical compositions described by the formula REH2−δOδ in the range of 0.45 < δ < 1.5.