In this study, an anisotropic quasi-atomic layer etching (qALE) process for InGaZnO4 (IGZO) removal was developed and systematically investigated, consisting of alternating unbiased CH4 plasma adsorption and biased (continuous or pulsed) O-2 plasma desorption steps. The etching behavior was examined by independently varying the CH4 plasma time, O-2 plasma time, surface temperature, bias voltage, and pulse duty cycle. The total cyclic etch rate was analyzed in terms of its physical and chemical components, with the two etching contributions examined separately. The physical cyclic etch rate increased linearly with O-2 plasma processing time, bias voltage, and pulse duty cycle, while the chemical cyclic etch rate exhibited a self-limiting behavior with increasing CH4 and O-2 plasma processing times. The chemical cyclic etch rate rose from 0.07 nm/cycle at 0% duty cycle in pulsed biased O-2 plasma to 0.13 nm/cycle at 10%, remained constant between 10% and 70%, and further increased to 0.20 nm/cycle at 100%. This defined a qALE process window between 10% and 70% duty cycle at 60 V bias voltage, likely due to the complete removal of the saturated hydrocarbonated IGZO layer under moderate ion bombardment. ALE synergy decreased with increasing O-2 plasma time, higher bias voltage, and higher duty cycle, reflecting the enhanced physical etching contribution. The cation composition of the IGZO film surface was analyzed using x-ray photoelectron spectroscopy after the qALE process. The Ga fraction in amorphous IGZO increased following qALE, due to the stronger Ga-O bond relative to In-O and Zn-O, resulting in a lower Ga etch rate. However, under higher bias voltage in the O-2 plasma step, the Ga enrichment was less pronounced, suggesting the formation and desorption of Ga-containing etch by-products at elevated ion bombardment. This developed anisotropic qALE process was effectively applied to top-gate trench patterning for IGZO channel transistor fabrication, enabling precise control of channel thickness and yielding an excellent etch profile with high ALE synergy.

Since Cu(InxGa1 - x)Se2 (CIGS) absorbers are among the most efficient materials for photovoltaic energy conversion, it is crucial to understand their degradation mechanisms and the key factors driving them. To do so, we present aging studies up to 2000 h at 80% relative humidity and 20°C, first under illumination and then in the dark. Three complementary techniques are used to unveil the evolution of the absorber at different probing depths. Surface and subsurface chemical reactivities are investigated, respectively, thanks to XPS (x-ray Photoelectron Spectroscopy) and HaXPES (Hard x-ray Photoemission Spectroscopy) characterizations (probing from 3 up to 41 nm). In addition, EDS (Energy Dispersive Spectroscopy) measurements unveil the bulk chemical reactivity at 0.7 and 1.3 µm. The main result is a greater sensitivity of the absorber's surface when RH is combined with light rather than dark exposure, which triggers the CIGS network faster, leading to oxide phase growth, Se0 side phases appearance, and Na diffusion. This shows that the degradation is boosted in the presence of light. On the other hand, the CIGS bulk results intact around 1 µm under all the ambient conditions investigated.

Hybrid vapor–solution processing combined with evaporated dual-interface engineering enables efficient FAPbI 3 -based solar cells with outstanding thermal stability beyond 10 000 hours.

Zinc oximates-organometallic compounds combining zinc and oximate ligands-were previously used as precursors for zinc-oxide-based thin-film transistor applications. Recently, the potential of zinc oximates as high-resolution patterning materials was evaluated via electron beam lithography and extreme ultraviolet (EUV) lithography (EUVL). However, a detailed understanding of the lithographic reaction mechanisms is currently lacking due to limited exploration in material characterization and process tuning, particularly the crucial reaction mechanism that occurs during the post-exposure bake (PEB). Understanding how PEB affects zinc oximate resists is essential to further enhance the EUV sensitivity and line-edge roughness (LER) of this potentially new class of organometallic resists. In addition, the integration of zinc oximate resists into industrial EUV lithography processes has not yet been demonstrated. To address this knowledge gap, we first demonstrated the highest resolution possible (pitch-24 nm line-and-space) with a 0.33NA ASML EUV scanner tool and then performed a holistic investigation of the EUV exposure and thermally driven reaction mechanisms of a zinc oximate resist, zinc open-source nano-engineered (ZONE), which we link to on-wafer pitch-32 nm dense line-and-space EUV patterning performance. Specifically, we show that thermal treatment at 140 degrees C temperatures leads to the initiation of conversion into ZnO, thus preventing the optimization of patterning performance via the PEB. In contrast, no ZnO formation is observed under EUV exposure of 100 mJ/cm2, indicating a fundamentally different mechanism for the solubility switch-one driven by preferential bond cleavage rather than bulk oxide formation. These competing chemical mechanisms manifest in a degradation of pattering performance (e.g., resolution, LER, etc.) under increasing PEB temperature (from 120 to 180 degrees C), which indicates thermally driven reactions indiscriminately cleave organic bonds and compromise the solubility contrast in ZONE. Nevertheless, the remarkably high resolution in EUV lithography suggests that metal oximate resists are a promising platform for future high-NA EUV lithography.

Perovskite photodetectors (PePDs) represent a promising extension of perovskite solar cells (PSCs), sharing the device architecture but targeting distinct performance metrics. While PSCs prioritize high power conversion efficiency and operational stability, PePDs require low dark-current, high responsivity, detectivity, and fast response. These traits depend strongly on the transport layers, which govern interfacial recombination and carrier extraction dynamics. Tin-oxide (SnOx), widely employed as an electron transport layer in PSCs due to its transparency, energy-level alignment, and chemical stability, is an attractive candidate for PePDs. Traditionally, SnOx is deposited via atomic layer deposition, which offers excellent conformality and thickness control but suffers from high precursor and processing gas costs and low throughput thus limiting its scalability. In this work, we explore magnetron sputtering as a scalable alternative. However, conventional sputtering can damage underlying layers through ultraviolet radiation and high-energy particle bombardment. To address this, we developed a soft-sputtering protocol that enables SnOx deposition on inverted perovskite devices while preserving the integrity of the underlying layers. Devices fabricated with soft-sputtered SnOx exhibit a low-leakage current of 10-8 A cm-2 at-0.5 V, a detectivity of up to 1012 Jones, and fast response times of less than 2 mu s for an active area of 0.125 cm2.

Nickel-oxide (NiO) is a widely adopted inorganic hole transport layer (HTL) for inverted (p-i-n) perovskite solar cells (PSCs). Its deposition by magnetron sputtering is particularly attractive for industrial deployment due to its uniformity, throughput, and large-area compatibility. Conventional sputtered NiOx typically requires post-deposition annealing (∼300 °C) to achieve suitable HTL characteristics. Such annealing imposes severe constraints on large-area glass, flexible substrates, and tandem device stacks, and exacerbates reliability issues like alkali migration from soda-lime glass. Here, we demonstrate an annealing-free, large-area processed NiO, sputtered from a stoichiometric NiO target. Our process delivers HTL properties comparable to, or exceeding, those of conventionally annealed NiOx. Through a combined analysis of optical spectroscopy, ellipsometry, XPS/UPS, and transmission line measurements, we achieve high transparency, favorable energetics (Φ = 4.25 eV, reduced EF-EV), and tuneable p-type transport governed by controlled oxygen supply. Inverted PSCs employing such NiOx reach efficiencies of ∼18% without any thermal treatment, matching annealed counterparts. With the inclusion of a self-assembled monolayer and passivation layers, the devices produce 22.5% efficiency. Crucially, we demonstrate process transfer to mini- (4 cm2) and large-area (781 cm2) modules, yielding comparable performance to annealed NiOx. Our mini- and large-area modules show efficiencies of 19.6% and 14.6% respectively.

In this study, an anisotropic quasi-atomic layer etching (qALE) process for InGaZnO 4 (IGZO) removal was developed and systematically investigated, consisting of alternating unbiased CH 4 plasma adsorption and biased (continuous or pulsed) O 2 plasma desorption steps. The etching behavior was examined by independently varying the CH 4 plasma time, O 2 plasma time, surface temperature, bias voltage, and pulse duty cycle. The total cyclic etch rate was analyzed in terms of its physical and chemical components, with the two etching contributions examined separately. The physical cyclic etch rate increased linearly with O 2 plasma processing time, bias voltage, and pulse duty cycle, while the chemical cyclic etch rate exhibited a self-limiting behavior with increasing CH 4 and O 2 plasma processing times. The chemical cyclic etch rate rose from 0.07 nm/cycle at 0% duty cycle in pulsed biased O 2 plasma to 0.13 nm/cycle at 10%, remained constant between 10% and 70%, and further increased to 0.20 nm/cycle at 100%. This defined a qALE process window between 10% and 70% duty cycle at 60 V bias voltage, likely due to the complete removal of the saturated hydrocarbonated IGZO layer under moderate ion bombardment. ALE synergy decreased with increasing O 2 plasma time, higher bias voltage, and higher duty cycle, reflecting the enhanced physical etching contribution. The cation composition of the IGZO film surface was analyzed using x-ray photoelectron spectroscopy after the qALE process. The Ga fraction in amorphous IGZO increased following qALE, due to the stronger Ga–O bond relative to In–O and Zn–O, resulting in a lower Ga etch rate. However, under higher bias voltage in the O 2 plasma step, the Ga enrichment was less pronounced, suggesting the formation and desorption of Ga-containing etch by-products at elevated ion bombardment. This developed anisotropic qALE process was effectively applied to top-gate trench patterning for IGZO channel transistor fabrication, enabling precise control of channel thickness and yielding an excellent etch profile with high ALE synergy.

Extreme ultraviolet (EUV) lithography has revolutionized the high-volume manufacturing of nanoscale components. The use of EUV light leads to ionization-driven chemistry in the imaging materials of lithography, the photoresists. The complex interplay of ionization, generation of primary/secondary electrons, and the subsequent chemical mechanisms that lead to image formation in photoresists has been notoriously difficult to study. This is in particular true for the radiochemical transformations occurring during exposure. In this work, we deploy table-top EUV photoemission spectroscopy to observe in situ chemical changes occurring during exposure in a model chemically amplified photoresist and discover a surprising chemical reaction pathway, the EUV-induced breakdown of a perfluoroalkyl substance (PFAS) photoacid generator (PAG). This previously unobserved breakdown of the PFAS PAG, a critical component in the EUV exposure mechanism, manifests as changes in the intensity of the valence band peaks of the EUV photoemission spectrum, which are linked to degradation of the PFAS PAG via an advanced atomistic simulation framework. Our combined experimental and theoretical approach shows that EUV photoemission can simultaneously resolve chemical dynamics and the production of primary and secondary electrons, giving unique insights into the radiochemical transformation of photoresist materials. More generally, our approach also shows that EUV photoemission spectroscopy can provide a unique platform for tracking degradation pathways of PFAS molecules in thin films, owing to the high ionization cross section of fluorine at EUV wavelengths. Our results pave the way for utilizing accessible, table-top EUV spectroscopy systems for observing EUV photoresist chemical dynamics, with the potential for time-resolved measurements of photoemission processes in the future.

Extreme ultraviolet (EUV) lithography has revolutionized high-volume manufacturing of nanoscale components, enabling the production of smaller, denser, and more energy efficient integrated circuit devices. Yet, the use of EUV light results in ionization driven chemistry within the imaging materials of lithography, the photoresists. The complex interplay of ionization, generation of primary and secondary electrons, and the subsequent chemical mechanisms leading to image formation in photoresists has been notoriously difficult to study. In this work, we deploy photoemission spectroscopy with a 92 eV EUV light source combined with first-principles simulations to unravel the chemical changes occurring during exposure in a model chemically amplified photoresist. The results reveal a surprising chemical reaction pathway, namely the EUV-induced breakdown of the photoacid generator (PAG), which is a critical component in the EUV mechanism. This previously unobserved reaction mechanism manifests as changes in intensity of the valence band peaks of the EUV photoemission spectrum, which are linked to degradation of the PAG via an advanced atomistic simulation framework. Our combined experimental and theoretical approach shows that EUV photoemission can simultaneously resolve chemical dynamics and the production of primary and secondary electrons, giving unique insights into the chemical transformation of photoresist materials. Our results pave the way for utilizing accessible, table-top EUV spectroscopy systems for observing EUV photoresist chemical dynamics, with the potential for time-resolved measurements of photoemission processes in the future.

Heavy-metal-free III-V semiconductor-based colloidal quantum dots (CQDs), such as InAs, are promising candidates for near- and short-wave infrared detection. However, up-to-date research efforts remain mainly limited to wavelengths below 1100 nm due to challenges in synthesis, junction formation, and passivation for large diameter InAs quantum dots. Systematic investigations into device design, reverse dark current mechanisms, and trap distributions in larger InAs quantum dots remain limited. Here, we report a thin-film PIN heterojunction colloidal InAs (1200 nm) photodiode stack with amorphous indium gallium zinc oxide and copper(I) iodide transport layers. To the best of our knowledge, the device exhibits one of the lowest reported dark current densities of 4.7 μA/cm2 at -1 V and 298 K, which decreases to 3.6 nA/cm2 at 220 K. Temperature-dependent current-voltage characteristics and activation energy analysis confirm thermally driven dark current increasing with applied field. Impedance spectroscopy reveals the dominant deep trap states within the InAs CQD layer, being tail states of the conduction band that reach down to ∼0.4 eV below the band edge, with a density of ∼2 × 1016 cm-3. The temperature-induced increase in carrier density and reduction in built-in potential within the depleted InAs layer reflect trap filling and Fermi level pinning in the N and P layers. The trapping-detrapping induced noise reduces the specific detectivity (D*) at -1 V by 1.97 orders at 1 Hz and by 1.52 orders of magnitude at 10 Hz relative to the shot-noise-limited baseline. At frequencies ∼ ≥500 Hz the D* approaches the calculated limit of 2.5 × 1011 Jones. Finally, we demonstrate infrared imaging by monolithically integrating the photodiode with a Si read-out IC, enabling imaging beyond the spectral range of CMOS sensors.

Ru post dry-etch surfaces are exposed to UV irradiation and subsequent wet cleaning, to remove post etch residues. The nature of these residues, their removal efficiency and mechanisms are investigated. The post etch surface consists of native oxides of Ru and Ti along with Cl-impurities. Both UV and UV + wet cleaning processes are found to reduce the native oxide and Cl-residues, increase the hydrophilicity of the surface and improve the residue removal efficiency by improving the wetting of the small trenches (9 nm CD) in the patterned structures (18 nm metal pitch). Leakage measurements show an improvement in the leakage yield from similar to 30% to similar to 50% at a current of 1x10(-11) A.

The development of extreme ultraviolet sources for nanolithography is enabling the production of integrated circuits with feature sizes of less than 10 nm. This necessitates simultaneously the optimization of photoresist materials adapted to the high photon energy and low flux of these sources to ensure a precise pattern transfer and guarantee a high throughput. A common type of EUV resists are chemically amplified resists (CAR), containing a (co)polymer, which plays the main role in the pattern transfer through a deprotection reaction leading to a solubility switch. The composition of CARs and the ionizing nature of EUV light lead to a complex chemistry induced by photons and electrons in the resist film. This makes it difficult to grasp the full reaction mechanism. Therefore, the isolated role of the photoionization process on the copolymer of typical CARs containing poly(hydroxy styrene)/poly(tert-butyl methacrylate) (PHS/PBMA) is studied. Gas phase photoelectron photoion coincidence (PEPICO) experiments on the proxy molecules 4-isopropyl phenol (IPP) and tert-butyl methacrylate (tBMA) are conducted employing synchrotron radiation, which yield deep insights into dissociative photoionization. While the phenolic moiety in IPP undergoes fragmentation only to a small degree, the dissociative photoionization of the ester group in tBMA leads to several important fragments that are mostly unfavorable for an efficient solubility switch. By comparing these insights to EUV photoemission and desorption experiments on PHS and PBMA thin films in solid phase, a better understanding of the initial photoionization reaction in the exposure mechanism of CARs is obtained. Combining this knowledge with further complementary experiments is crucial to develop higher performing EUV photoresists for future technology nodes.

Time of Flight Secondary Ion Mass Spectrometry is a powerful technique for the characterization of various materials. Depth profiling in the dual beam mode enables the acquisition of information about the threedimensional composition of a sample. In this context, the selection of the most appropriate sputter conditions is of critical importance in order to ensure the reliability of the results obtained. Despite advancements, challenges persist in finding a suitable sputter source to perform depth profiling on hybrid nanomaterials (based on the mixing of pure organic and inorganic compounds), primarily due to the different sputtering conditions required for the inorganic and the organic components. In this work, we present an approach that employs a high-energy-per-atom argon cluster sputter source to perform depth profiling of a model hybrid sample consisting of molybdenum oxide and N,N '-Di(1-naphthyl)-N,N '-diphenyl-(1,1 '-biphenyl)-4,4 '-diamine. The findings demonstrated that decreasing the cluster size while maintaining a high kinetic energy of the beam allowed to increase the sputtering yield for the inorganic moiety, while preserving the molecular information of the organic counterpart. Moreover, we demonstrated that damage accumulation and ion beam mixing processes can be successfully attenuated by decreasing the sample temperature during depth profiling.

Carbon nitride (CN) has emerged as a promising metal-free semiconductor for photoelectrochemical (PEC) water-splitting applications. However, its practical implementation is hindered by low photoactivity compared with inorganic photoanodes. We report the excellent photoactivity of modified CN photoanodes for PEC water oxidation. Incorporating powder precursors during the synthesis induces favorable morphological modifications, enhanced layer ordering, and charge transfer. The powder thiourea-assisted growth of CN boosted the photocurrent by almost 3-fold. This enhancement is attributed to suppressed carrier recombination, improved charge transfer, and the formation of CN and SnS2 heterojunctions. The champion CN photoanode achieved an excellent charge extraction efficiency of up to 69% and a benchmark photocurrent density with and without a hole scavenger of about 2.7 and 2 mA cm-2, respectively for water oxidation at 1.23 V versus RHE in neutral 0.1 M Na2SO4 solution, with an onset potential of 0.32 V vs RHE and external quantum yield reaching 42% at 440 nm.

This study examines the impact of inserting an ultrathin $\text{MoO}_{\mathrm{x}}$ seed $(<2 \text{nm})$ into HZO-based capacitors with TiN electrodes, while reducing the physical thickness of HZO, grown by atomic layer deposition, from 9 to 5 nm. The crystallinity of the stack was assessed using X-ray diffraction and transmission electron microscopy, while the grain size and phase analysis was analyzed in some cases by precession electron diffraction. X-ray photoelectron spectroscopy provided insights into the oxidation state of $\text{MoO}_{\mathrm{x}}$. Ferroelectric HZO with suppressed wake-up can be fabricated using $\text{MoO}_{\mathrm{x}}$ seed, achieving remanent polarization between 25 $\mu \mathrm{C} / \text{cm}^{2}$ and $40 \mu \mathrm{C} / \text{cm}^{2}$ and an endurance of at least 108 cycles for HZO layers with a thickness of 5 to 9 nm. The study elucidates how the $\text{MoO}_{\mathrm{x}}$ seed influences the phase equilibrium among tetragonal, orthorhombic, and monoclinic phases within HZO by regulating oxygen vacancies. This seed alters the size, distribution, and orientation of ferroelectric orthorhombic grains, which are essential for ferroelectric properties.

Two-dimensional transition metal dichalcogenides (2D TMDs), such as MoS2 and WS2, have emerged as promising channel materials for future generation transistors. However, carbon-based surface contaminants pose a significant challenge in the formation of high-quality metal-oxide-semiconductor gate stacks for 2D TMDs. Carbon-based surface contaminants are known to be present even on directly grown 2D TMDs that have not been in contact with polymers. These organic contaminants affect precursor adsorption during atomic layer deposition (ALD) of gate dielectrics on 2D TMDs and as such the 2D-dielectric interface. This study examines the effectiveness of predeposition annealing in mitigating carbon-based contaminants while maintaining the integrity of a directly grown WS2 monolayer on a SiO2 substrate. We show that a WS2 monolayer on a SiO2/Si substrate remains stable during vacuum annealing at temperatures up to 400 degrees C. Water contact angle measurements and x-ray photoelectron spectroscopy confirm that the surface concentration of carbon starts to decrease at 150 degrees C. Thermal anneal improves the surface coverage of Al2O3 for both conventional chemisorption-based ALD and physisorbed-precursor-assisted ALD processes by facilitating more effective Al2O3 nucleation on the WS2 monolayer. The impact of predeposition anneal on the Al2O3 growth behavior in both processes can be explained by changes in surface contaminant levels. Our results underscore the importance of surface pretreatment in dielectric deposition on 2D TMDs and demonstrate that predeposition anneal is an effective method to enhance ALD-based dielectric deposition on directly grown 2D TMDs.

In contrast to traditional X-ray photoelectron spectroscopy (XPS), hard X-ray photoelectron spectroscopy (HAXPES) can provide information from deeper within a sample while maintaining chemical resolution. However, working with higher energy X-rays introduces a series of new or different issues ranging from energy calibration to factors associated with quantitative analysis. As part of the efforts to identify and increase community awareness about these issues, a workshop was held to review HAXPES metrology challenges with the perspective of converting it into a quantitative technique. A summary is hereby given of this workshop, which was entitled "What New Challenges Come with the Capabilities of HAXPES?" It was held in Portland, OR, USA, on November 7, 2023, and was primarily sponsored by the ASTM E42 Committee and the Applied Surface Science Division of the American Vacuum Society. This report contains summaries of the presentations and discussions at this workshop regarding the current open problems in HAXPES metrology. There were 20 participants at the workshop.

Functionalizing surfaces with self-assembled monolayers (SAMs) allows to efficiently bind bioreceptors, for instance, by bio-orthogonal click reactions, which is useful in biosensor fabrication. Control of the bioreceptor concentration on the surface can be achieved by coating an SAM mixture consisting of a functional SAM, which binds the bioreceptor, and a nonfunctional SAM for dilution. In this work, a novel vapor-based coating approach for the preparation of mixed SAM coatings is presented. Sequential evaporation of the SAM precursors, i.e., fluoroalkyl and azidoalkyl silanes, by heating under reduced pressure leads to the formation of a two-dimensional siloxane monolayer network on silicon oxide. The presence of both SAMs in the mixed coatings is confirmed by Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy. As verified by atomic force microscopy, the morphologies of the coatings and the uncoated silicon oxide substrates are similar, indicating a conformal coating. Functionality of the SAM mixture is demonstrated by a reaction with a fluorescent dye, illustrating its potential application in biosensors.

The broadening in photoelectron spectra of polymers can be attributed to several factors, such as light source spread, spectrometer resolution, the finite lifetime of the hole state, and solid-state effects. Here, for the first time, we set up a computational protocol to assess the peak broadening induced for both core and valence levels by solid-state effects in four amorphous polymers by using a combination of density functional theory, many-body perturbation theory, and classical polarizable embedding. We show that intrinsic local inhomogeneities in the electrostatic environment induce a Gaussian broadening of 0.2-0.7 eV in the binding energies of both core and semivalence electrons, corresponding to a full width at half-maximum (FWHM) of 0.5-1.7 eV for the investigated systems. The induced broadening is larger in acrylate-based than in styrene-based polymers, revealing the crucial role of polar groups in controlling the roughness of the electrostatic landscape in the solid matrix.