Over the last two decades, prototype devices for future classical and quantum computing technologies have been fabricated, by using scanning tunneling microscopy and hydrogen resist lithography to position phosphorus atoms in silicon with atomic-scale precision. Despite these successes, phosphine remains the only donor precursor molecule to have been demonstrated as compatible with the hydrogen resist lithography technique. The potential benefits of atomic-scale placement of alternative dopant species have, until now, remained unexplored. In this work, we demonstrate the successful fabrication of atomic-scale structures of arsenic-in-silicon. Using a scanning tunneling microscope tip, we pattern a monolayer hydrogen mask to selectively place arsenic atoms on the Si(001) surface using arsine as the precursor molecule. We fully elucidate the surface chemistry and reaction pathways of arsine on Si(001), revealing significant differences to phosphine. We explain how these differences result in enhanced surface immobilization and inplane confinement of arsenic compared to phosphorus, and a dose-rate independent arsenic saturation density of 0.24±0.04 monolayers. We demonstrate the successful encapsulation of arsenic delta-layers using silicon molecular beam epitaxy, and find electrical characteristics that are competitive with equivalent structures fabricated with phosphorus. Arsenic delta-layers are also found to offer improvement in out-of-plane confinement compared to similarly prepared phosphorus layers, while still retaining >80% carrier activation and sheet resistances of <2 kΩ/□. These excellent characteristics of arsenic represent opportunities to enhance existing capabilities of atomic-scale fabrication of dopant structures in silicon, and are particularly important for threedimensional devices, where vertical control of the position of device components is critical. TOC GRAPHICS

In the search for nontoxic alternatives to lead-halide perovskites, bismuth oxyiodide (BiOI) has emerged as a promising contender. BiOI is air-stable for over three months, demonstrates promising early-stage photovoltaic performance and, importantly, is predicted from calculations to tolerate vacancy and antisite defects. Here, whether BiOI tolerates point defects is experimentally investigated. BiOI thin films are annealed at a low temperature of 100 °C under vacuum (25 Pa absolute pressure). There is a relative reduction in the surface atomic fraction of iodine by over 40%, reduction in the surface bismuth fraction by over 5%, and an increase in the surface oxygen fraction by over 45%. Unexpectedly, the Bi 4f 7/2 core level position, Fermi level position, and valence band density of states of BiOI are not significantly changed. Further, the charge-carrier lifetime, photoluminescence intensity, and the performance of the vacuum-annealed BiOI films in solar cells remain unchanged. The results show BiOI to be electronically and optoelectronically robust to percent-level changes in surface composition. However, from photoinduced current transient spectroscopy measurements, it is found that the as-grown BiOI films have deep traps located ≈0.3 and 0.6 eV from the band edge. These traps limit the charge-carrier lifetimes of BiOI, and future improvements in the performance of BiOI photovoltaics will need to focus on identifying their origin. Nevertheless, these deep traps are three to four orders of magnitude less concentrated than the surface point defects induced through vacuum annealing. The charge-carrier lifetimes of the BiOI films are also orders of magnitude longer than if these surface defects were recombination active. This work therefore shows BiOI to be robust against processing conditions that lead to percent-level iodine-, bismuth-, and oxygen-related surface defects. This will simplify and reduce the cost of fabricating BiOI-based electronic devices, and stands in contrast to the defect-sensitivity of traditional covalent semiconductors.

Several K-Ca-Si glass compositions typical of Central-European glassworks are susceptible to damage beyond recall, even in mild museum conservative conditions. In order to provide a comprehensive picture of the deterioration process, replica samples were produced and exposed to four different museum-like environments. The corrosion experiment was followed by the use of ToF-SIMS, µ-Raman and µ-FTIR, performing a systematic compositional and structural study for the early stages (one year) of surface alteration. This work demonstrates the dominant role of Pb 2+ and Ca 2+ content for the inferable existence of connected conduction pathways, with strong implications on the surface's hydration, alkalidiffusion and hydrolysis.

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Cathode active materials (CAMs) in state-of-the-art lithium-ion batteries are mostly lithium-transition-metal oxides such as Li(Ni x Co y Mn z )O 2 (x + y + z = 1). To achieve optimum cycling stability and performance of the cathode, the extent of degradation processes and side reactions between CAMs and liquid or solid electrolytes has to be minimized. For this purpose, various coating strategies for CAMs have been developed in recent years. The underlying mechanism of the protective function of nanoscale coatings and their role for the enhanced cycling performance are mostly unclear, which is often based on incomplete characterization of the coating. Only a few analytical methods, such as X-ray diffraction, scanning electron microscopy/energy-dispersive X-ray analysis, or X-ray photoelectron spectroscopy, have frequently been used in recent years, which often cannot provide enough information for a reliable and consistent picture of the very thin coating. For this reason, we demonstrate a systematic study on the analytical characterization of coated CAM using additional analytical methods. NCM622 coated with TiO 2 by atomic layer deposition is used as a model system and analyzed with SEM/EDX, focused ion beam scanning electron microscopy, scanning transmission electron microscopy, Raman spectroscopy, X-ray photoelectron spectroscopy, low-energy ion scattering, and time-of-flight secondary ion mass spectrometry. The results highlight the advantages and disadvantages of each analytical method for the analysis of typical CAM coatings. The results demonstrate that a combination of the different methods is essential to understand CAM coatings and their properties in full detail.

The combination of Raman spectroscopy and Secondary Ion Mass Spectrometry can improve understanding of the chemistry of the glass alteration process. Formic and acetic acids play an important role in the alteration of museum glass objects placed in a humid atmosphere. Raman spectroscopy indicates that the soda-rich glass structure is modified differently when exposed to a humid versus a humid and polluted atmosphere at 60°C. Formic acid was not formed from soda-rich glass in the presence of carbon dioxide, high humidity and light.

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Purpose: Micrometer-sized spherules formed of hydroxyapatite or whitlockite were identified within extracellular deposits that accumulate in the space between the basal lamina (BL) of retinal pigment epithelium (RPE) and the inner collagenous layer of Bruch's membrane (sub-RPEeBL space). This investigation aimed to characterize the morphologic features, structure, and distribution of these spherules in aged human eyes with and without clinical indications of age-related macular degeneration (AMD).Design: Experimental study.Participants: Five human eyes with varying degrees of sub-RPEeBL deposits were obtained from the University College London Institute of Ophthalmology and Moorfield's Eye Hospital Tissue Repository or the Advancing Sight Network. Two eyes were reported as having clinical indications of AMD (age, 76e87 years), whereas 3 were considered healthy (age, 69e91 years).Methods: Cadaveric eyes with sub-RPEeBL deposits were embedded in paraffin wax and sectioned to a thickness of 4-10 mm. Spherules were identified and characterized using high-resolution scanning electron microscopy (SEM), energy-dispersive x-ray spectroscopy, and time-of-flight secondary ion mass spectroscopy.Main Outcome Measures: High-resolution scanning electron micrographs of spherules, the size-frequency distribution of spherules including average diameter, and the distribution of particles across the central-peripheral axis. Elemental maps and time-of-flight secondary ion mass spectra also were obtained.Results: The precipitation of spherules is ubiquitous across the central, mid-peripheral, and far-peripheral axis in aged human eyes. No significant difference was found in the frequency of spherules along this axis. However, statistical analysis indicated that spherules exhibited significantly different sizes in these regions. Indepth analysis revealed that spherules in the sub-RPEeBL space of eyes with clinical signs of AMD were significantly larger (median diameter, 1.64 mm) than those in healthy aged eyes (median diameter, 1.16 mm).Finally, spherules showed great variation in surface topography and internal structure.Conclusions: The precipitation of spherules in the sub-RPEeBL space is ubiquitous across the centraleperipheral axis in aged human eyes. However, a marked difference exists in the size and frequency of spherules in eyes with clinical signs of AMD compared to those without, suggesting that the size and frequency of spherules may be associated with AMD.