AVS 72 Session TF-ThP: Thin Film Poster Session

Porous transport layers (PTLs) are essential components in water electrolyzers, facilitating efficient electrochemical reactions. Situated between the electrodes and current collectors, PTLs offer structural integrity, enable the diffusion of gases and the removal of water from reaction sites, ensure electrical connectivity between the electrode and current collector, and assist in thermal management by dissipating heat.

Titanium-based PTLs are widely used due to their good conductivity, corrosion resistance, and mechanical robustness. However, they are susceptible to long-term degradation under the aggressive chemical environments typical of electrolyzer cells. To address this, protective coatings are applied to enhance PTL performance by enhancing surface chemical stability and modifying surface characteristics.

Atomic layer deposition (ALD) is a highly effective technique for applying these protective coatings, particularly for porous substrates. Its conformal and precise nature allows for the fine-tuning of thin-film properties. In this study, we present findings from low-energy ion scattering (LEIS) analyses of ALD-coated Ti-based PTLs, utilizing a variety of coating materials.

LEIS, with its exceptional surface sensitivity, enables the quantification of surface coverage by the ALD film, offering critical insights into film growth and layer closure. Additionally, film thickness is evaluated to understand the ALD growth mechanism and growth per cycle. We also address the analytical challenges posed by the highly three-dimensional structure of the substrate, which impacts surface quantification and thickness measurements.

Quench-condensed bismuth thin films deposited at substrate temperatures T_s = 4 K can exhibit superconductivity. However, the origin of this phenomenon is still debated [1]. Here, we report on the effect of T_s on the microstructure and transport properties of 100 nm thick Bi films evaporated onto single-crystalline Al₂O₃(0001), amorphous SiO₂, and van der Waals structured mica substrates. Two sets of samples are deposited, one at low T_s = 77 K and the other at T_s = 296 K [2]. Using atomic force microscopy, X-ray diffraction, transmission electron microscopy, and variable temperature multicarrier magnetotransport characterization techniques, we determine morphologies, crystallinities, carrier mobilities, carrier densities and sheet resistances of the as-deposited films. For the Bi films deposited on Al₂O₃(0001) and SiO₂ at T_s =77 K, the measured root-mean-square roughness values are comparable and are 3 to 4 times smaller than those obtained for the films grown at T_s = 296 K. In comparison, for the Bi films deposited on mica at the two different T_s, while the surface roughness is similar, the film morphologies are different. On all three substrates, rhombohedral (R-3m) 110-textured films at T_s = 77 K and 111-textured films at 296 K are obtained, with grain sizes 1.7 times larger for the films grown at T_s = 296 K. We find evidence of multicarrier transport in the films, originating from electrons and holes in the bulk in addition to surface state electrons in Bi(111) and Bi(110) oriented films [3]. Overall, on all three substrates films deposited at T_s = 77 K exhibit lower carrier mobility and higher sheet resistance when compared with films deposited at T_s = 296 K. Interestingly, annealing Bi films grown at 77 K results in a transition from a predominantly 110-texture to a predominantly 111-texture. In contrast, annealing Bi films deposited at 296 K leads to dewetting. Our results show the effects of deposition temperature and the substrate structure on morphology, microstructure, and charge transport characteristics of Bi thin films.

References: [1]. T. Hamada et al., J. Phys. F: Metal Phys. 11, 657 (1981); [2] Y. Kirina et al., arXiv:2604.00369v1 (2026). [3] Ph. Hofmann, Prog.Surf. Sci. 81 (2006) 191.

Thin-film processing increasingly depends on controlling chemistry at the scale of individual surface sites. In atomic layer deposition and atomic layer etching, precursor exposure, ligand removal, surface activation, and product desorption determine the final film structure and process selectivity. Atomistic simulations can provide mechanistic insight into these steps, but realistic process modeling requires methods that can describe reactive events while remaining efficient enough to sample complex surfaces and repeated process cycles.

This poster presents a simulation workflow for studying thin-film growth and surface modification using reactive force fields and machine-learned interatomic potentials. Representative systems include HF interaction with SiO₂ surfaces, relevant to oxide etching and surface modification, and TMA reactions with hydroxylated Al₂O₃, relevant to alumina atomic layer deposition. The workflow combines model surface generation, reactive molecular dynamics, trajectory analysis, and comparison with higher-level reference calculations. Key observables include surface functional group populations, bond rearrangements, volatile product formation, local coordination environments, and changes in film density or surface roughness.

By comparing etching and deposition examples, we illustrate how similar atomistic tools can be used to study both material removal and film growth. For HF/SiO₂, simulations can probe how hydroxylation, strain, and local network structure affect fluorination and etch susceptibility. For TMA/Al₂O₃, simulations can examine ligand exchange, methane formation, steric blocking, and the persistence of reactive surface sites over repeated exposure steps. These results support a mechanistic picture of how local surface structure controls macroscopic process behavior.

The poster emphasizes practical workflow choices, including the role of ReaxFF for exploratory reactive dynamics, the use of machine-learned potentials for improved accuracy and transferability, and validation strategies based on quantum chemical reference data. The approach is intended to help bridge molecular-scale reaction mechanisms with thin-film processing outcomes such as growth per cycle, etch selectivity, nucleation behavior, and interface quality.

The scalability of superconducting quantum computers is fundamentally limited by decoherence in Josephson junction–based qubits, where two-level system (TLS) defects at material interfaces are a major source of energy loss. Although aluminum remains the standard electrode material, its susceptibility to surface oxidation and coherence limitations have motivated the search for alternative superconductors. Titanium nitride (TiN) is a promising candidate because of its oxidation resistance, tunable kinetic inductance, and potential for reduced TLS-related losses. However, despite its use in superconducting resonators and capacitive elements, TiN-based Josephson junctions remain insufficiently optimized.

This research advances TiN as an electrode material for Josephson junctions by establishing reproducible fabrication protocols for TiN thin films with controlled stoichiometry, crystallinity, and superconducting properties. Using reactive magnetron sputtering with in-situ control of nitrogen partial pressure and sputtering power, this work systematically tunes film properties and correlates them with cryogenic device performance and quantum coherence metrics in TiN-based superconducting qubits.

By linking deposition conditions, materials quality, and qubit performance, this work addresses a critical materials-engineering gap in Josephson junction fabrication and establishes a pathway for integrating TiN into scalable quantum computing architectures. Future efforts will extend the platform to multi-qubit systems and all-nitride junction designs incorporating superconducting nitride barriers for improved materials compatibility and device performance.

There is a great deal of interest in rationally realizing van der Waals epitaxy (vdWE), a mechanism characterized by atomic-level registry across a weakly-bonded film-substrate interface. Weak interface bonding is conducive for stress-free crystal growth, and transfer to other substrates or stand-alone films. This is in contrast to conventional epitaxy with strong film-substrate interface bonding and lattice matching. The most intuitive examples of vdWE are seen in 2D materials like graphene and hexagonal boron nitride, where film-substrate atomic registry is mediated solely by vdW bonding.

The situation is more complex for substrates on which both conventional and vdW epitaxy are possible. A particularly important example is mica, a layered material commonly used for mechanically flexible thin films. Mica has been shown to support vdWE for layered materials such as chalcogenides. However, the current understanding of interface energetics and mechanisms of vdWE is inadequate to predict if a material will grow by vdWE or conventional epitaxy. As a result, vdWE is often incorrectly presumed simply because mica is layered, without establishing the conditions to indicate vdWE or even ignoring evidence to the contrary. We have shown that the growth of rocksalt ScN and NiO films on mica(001) occurs by conventional epitaxy. In fact, for any nonlayered materials such as transition metal oxides and nitrides grown on mica, conventional epitaxy should be the default assumption, and any claim of vdWE must, as a minimum, provide compelling evidence. Necessary conditions for vdWE are: a) in-plane and b) out-of-plane texturing, and c) nearly strain-free epilayers independent of lattice mismatch or film thickness.

In contrast, for layered materials on mica, the situation is far more complex, and an atomistic understanding of film/substrate interface structure that explains and predicts vdWE has remained elusive. We have unveiled atomistic interface mechanisms for vdWE of MoO₃ and VO₂ on mica showing negligible strain buildup in continuous epilayers, confirming vdWE. Ab initio computations showing interface energy minima for these orientations correlate with high cross-interface proximity between Mo atoms in MoO3 and K in mica conducive for maximal vdW attraction. These insights on interface structure and energetics provide a framework for predicting vdWE for different film/substrate combinations and designing of stress-free and/or standalone epitaxial films of layered materials on layered substrates such as mica.

[1] E Ekström, …, P Eklund Materials & Design 229, 111864 (2023)

[2] S Chowdhury, …, P EklundarXiv:2602.05741

[3] FAF Lahiji, .., P Eklund arXiv:2502.10594

All–inorganic lead halide perovskites (LHPs) combine tunable optical properties with strong excitonic behavior, making them attractive for integrated photonic and thin–film devices. Their chemical instability and complex phase behavior, however, make conventional lithographic patterning difficult. Here, we present a soft–lithographic approach that uses precursor stoichiometry, fluoroalkyl–silane-based surface modification, and micropatterned Si/SiO₂ templates to guide the selective nucleation and confined growth of CsPbBr₃ and CsPb₂Br₅ structures. Adjusting the CsBr:PbBr₂ ratio allows us to control the dominant phase, verified through photoluminescence and Raman measurements. Vapor–phase silanization of PDMS produces a lyophobic coating that can be transferred onto the template, creating a wettability difference that directs precursor infiltration and self–assembly during evaporation. This method yields patterned 1D perovskite arrays without the need for aggressive etching and provides a route toward thin–film structures with controlled morphology and crystallinity.

Thin films were synthesized from a family of pillared, microporous coordination polymers with the general formula M₂(BDC)₂L, where M is Ni²⁺, Co²⁺, Cu²⁺ and Zn²⁺, BDC is benzendicarboxylic acid and L is either is 1,4-diazabicyclo[2.2.2]octane (DABCO) or 4,4’-bypridine (bpy), by a hot-solvent technique and a room temperature layer-by-layer solution deposition. The thin films were grown on gold substrates and characterized by x-ray diffraction, x-ray photoelectron spectroscopy, ion-scattering spectroscopy, vibrational spectroscopy and scanning electron microscopy. The films were activated by heating under high vacuum and adsorption/desorption isotherms were measured for several volatile organic compounds. The mass uptake of the guest molecules into the coordination polymer host strongly depends on the extent of lattice interpenetration. In general, the extent of lattice interpenetration depends on the length of the diamine pillar. In the hot-vapor synthesis technique, lattice interpenetration is observed when using the longer bpy pillar, but not the shorter DABCO pillar. However, at room temperature, lattice interpenetration can be suppressed by using the layer-by-layer solution deposition technique with the bpy pillar. The key to suppress lattice interpenetration is use of a pyridine terminated thiol monolayer which templates the growth of a single phase.

The rapid degradation of nickel aluminium bronze (NAB) alloys in chloride-rich marine environments necessitates protective coatings with superior mechanical integrity, tribological durability and electrochemical stability. In the present work, nickel-doped chromium nitride coatings were deposited on NAB substrates by reactive DC magnetron sputtering using a co-focal arrangement of Cr and Ni targets in an Ar/N₂ plasma atmosphere. The incorporation of Ni was intended to improve the structural and multifunctional performance of CrN-based coatings for marine applications.

X-ray diffraction analysis confirmed the formation of crystalline Cr-N rich multiphase nitride structure consisting predominantly of FCC CrN/(Cr, Ni)N and HCP Cr₂N phases. A slight shift in diffraction peaks towards higher angles indicated lattice distortion and compressive residual stresses induced by substitutional incorporation of Ni into the CrN lattice. XPS investigations further confirmed the presence of Cr-N and Ni-N bonding states, confirming successful nitridation and the formation of a passive oxide layer for corrosion protection.

The deposited coating exhibited exceptional multifunctional performance. Contact angle measurements revealed a transition from hydrophilic to hydrophobic behaviour, where the water contact angle increased from 68.31 ± 1.21° for uncoated NAB to 135.32 ± 2.31° for coated NAB. Nanoindentation analysis indicated a hardness of ~37.14 GPa, attributed to hard nitride phase, grain refinement and lattice distortion. Tribological analysis revealed improved wear resistance, while the electrochemical study demonstrated nearly threefold enhancement in corrosion resistance under simulated marine conditions. The combined enhancement in hardness, hydrophobicity, wear resistance, and corrosion protection shows the potential of Ni-doped chromium nitride coatings for marine applications. The synergistic interaction between the dense nitride matrix and passive surface oxide restricted electrolyte penetration and material degradation, improving the reliability of NAB components exposed to harsh marine environments.

Advanced epitaxy techniques have become essential for superconducting quantum circuits due to their ability to fabricate high-quality and low-loss superconductors. Atomic layer deposition, which provides precise layer-by-layer growth, is widely adopted in advanced silicon manufacturing for complex 3D architectures, such as FinFETs and gate-all-around transistors. In this study, we investigate the structural and electrical transport properties of titanium nitride (TiN) thin films grown by hydrogen-manipulated atomic layer epitaxy (HM-ALE). Our twinned TiN film exhibits semi-coherent epitaxy with negligible oxide content, confirmed by synchrotron-based grazing-incidence wide-angle X-ray scattering (GIWAXS) and X-ray photoelectron spectroscopy, and X-ray absorption spectroscopy. Electrical transport measurements on Hall bar devices show a superconducting transition temperature of 2.2 K and a kinetic inductance of 15 pH/sq. Moreover, the superconducting coherence length of our TiN thin films is estimated to be 14.6 nm, comparable to the crystal coherent length measured by GIWAXS, suggesting that its fundamental superconducting properties may be correlated with the twinned structure. Our findings highlight HM-ALE as a promising epitaxial method for superconducting quantum research and applications.

Zeolitic imidazolate framework-8 (ZIF-8) is a promising candidate for advanced technological applications, including gas separation membranes, chemical sensors, and microelectronic devices. For many of these applications, thin film morphology is the most appropriate configuration, where defining critical operational limits like thermal stability is essential. However, while bulk ZIF-8 powder stability is well-documented, the thermal thresholds and structural degradation pathways of substrate-supported thin films under vacuum remain unexplored. Here, we track this degradation pathway using in situ IRRAS on a gold-supported film continuously heated under vacuum from 575 to 775 K. The framework remains structurally intact up to 700 K, followed by an abrupt, concurrent collapse of all characteristic vibrational modes at higher temperatures. This process was complemented by evaluating identically prepared parallel films via ex situ SEM, GIXD, and XPS. Interestingly, comparing these workflows demonstrates that the ambient air exposure encountered during ex situ analysis lowers the film's apparent stability threshold, inducing earlier structural collapse and severe film cracking. These results define a practical vacuum operating window of ≤ 700 K for the present ZIF-8 thin films and highlight the importance of maintaining controlled environments after activation.

Amorphous carbon (a-C) films are widely studied as protective coatings for micro- and nanoelectromechanical systems (MEMS/NEMS), biomedical components, and engineering surfaces prone to wear or corrosion. Their hardness, friction, chemical stability, and optical/electronic response are highly tunable through the sp²/sp³ bonding structure. For silicon-based coatings, these properties depend on energetic carbon penetration, intermixing with the substrate, and relaxation into sp² or sp³ bonded networks. This study uses molecular dynamics (MD) to investigate how incident carbon energy and substrate temperature govern a-C film growth on Si (100).

MD simulations were performed using the Large-scale Atomic/Molecular Massively Parallel Simulator (LAMMPS) with the Tersoff potential for C–C, C–Si, and Si–Si interactions. A diamond-cubic Si (100) substrate was modeled with fixed, thermostat, and free regions. A total of 3500 carbon atoms were deposited along the surface normal over 7 ns, followed by structural relaxation. Two primary parameter sets were evaluated: (1) incident carbon energy from 1 to 100 eV at 300 K, and (2) substrate temperature from 300 to 1200 K at a fixed incident energy of 40 eV. The resulting films were characterized by depth-resolved atomic distribution profiles, radial distribution functions, coordination-based sp¹/sp²/sp³ fractions, layer thicknesses, and density profiles.

The results show that incident energy controls the balance between surface film growth and Si–C intermixing. As energy increased from 1 to 100 eV, the interlayer thickness increased from 5.99 to 46.26 Å, while the stable carbon growth layer decreased from 33.60 to 11.11 Å. The strongest diamond-like character was observed at 40 eV, where the film reached the maximum sp³ fraction of 26.90% and maximum density of 2.54 g cm⁻³. Low incident energy limited carbon penetration and favored surface adsorption, while higher energy led to excessive penetration and partial sp³-to-sp² rehybridization. On the other hand, substrate temperature primarily controlled post-impact relaxation. At 40 eV, increasing the temperature from 300 to 1200 K broadened the interlayer from 18.68 to 30.28 Å, reduced the stable growth region from 19.23 to 15.59 Å, decreased the sp³ fraction from 26.90% to 17.32%, and increased the sp² fraction from 66.27% to 78.84%.

These findings demonstrate that achieving dense a-C growth on Si requires balancing subplantation-driven densification against relaxation. An incident energy of 40 eV provides the optimal deposition window for tetrahedral bonding, while elevated substrate temperature accelerates graphitization and interfacial broadening.

Electrochemical nitrate reduction to ammonia (eNO₃RR) has emerged as a promising route and sustainable alternative to conventional ammonia production. However, its practical implementation remains limited by poor selectivity, the competing hydrogen evolution reaction, and insufficient long-term stability, particularly at industrially relevant current densities (>300 mA cm^-2). Here, we report conjugated microporous polymer films based on molecular copper-porphyrin tapes as heterogeneous electrocatalysts for nitrate-to-ammonia conversion. The electrodes are prepared by the solvent-free oxidative polymerization of phenyl-substituted Cu-DPP and mesityl-substituted Cu-DMP directly on carbon paper, producing binder-free catalytic coatings with extended conjugated networks. The pCuDPP-coated electrode reaches a current density of 590 mA cm⁻² at -0.78 V vs RHE and an ammonia production rate of 26.86 mg h^-1 cm^-2 (287.7 mmol h⁻¹ mg_cat⁻¹) at -0.58 V vs RHE, this represents one of the highest reported ammonia production rates for eNO₃RR using a polymeric electrocatalyst. It also maintains stable activity for 15 h at 250 mA cm^-2 and for six days at 50 mA cm^-2. SEM-EDX mapping confirms that copper remains uniformly distributed across the electrode before and after electrolysis, while high-resolution XPS indicates that Cu(II) sites are largely preserved after operation, demonstrating robust structural stability. In comparison, pCuDMP shows lower activity, reaching 230 mA cm^-2 at -0.78 V vs RHE and an ammonia production rate of 12.5 mg h^-1 cm^-2 (134.74 mmol h⁻¹ mg_cat⁻¹) at -0.68 V vs RHE. This reduced performance highlights the importance of precursor molecular structure in controlling the electrocatalytic activity of catalysts prepared by oxidative polymerization. DFT calculations show that the phenyl substituents in pCuDPP remain in-plane with the porphyrin backbone, promoting extended π-conjugation, electronic delocalization, and improved charge transport. In contrast, the bulkier mesityl substituents present in pCuDMP twist out of plane because of steric hindrance, disrupting conjugation and limiting electronic conductivity. This nonplanar geometry may also restrict nitrate adsorption near the catalytic Cu sites, contributing to lower nitrate to ammonia activity. These results highlight substituent-controlled molecular geometry as an important design principle for developing high-rate conjugated porphyrin electrocatalysts for sustainable ammonia synthesis.

Keywords: Electrochemical nitrate reduction (eNO₃RR), Porphyrin-based catalysts, electrocatalyst, energy, Electrocatalysis, density functional theory (DFT).

The long-term reliability of chronic implantable devices is fundamentally limited by the encapsulation layers to withstand the ion-rich harsh environment of the human body. Single-layer thin films often fail due to intrinsic pinhole defects or hydrothermal degradation. This study investigates a tri-layer nanolaminate strategy employing HfO₂/Al₂O₃/HfO₂ deposited with atomic layer deposition (ALD). By depositing the Al₂O₃ layer between two chemically resilient HfO₂ layers, a synergistic barrier that inhibits ion diffusion and prevents moisture ingress is created. To assess the barrier properties of the proposed tri-layer structure, monolayer of Al₂O₃ and HfO₂ samples were prepared.

Tri-layer HfO₂/Al₂O₃/HfO₂ thin films with a total thickness of 60 nm were deposited on 4 µm thick polyimide (PI) substrates at 100°C. Polyimide 2610 was first spin-coated onto a silicon wafer and thermally cured. HfO₂ layers were deposited using tetrakis(dimethylamido)hafnium (TDMAH) and water, while Al₂O₃ layers were deposited using trimethylaluminum (TMA) and H₂O. Each oxide layer was deposited to a thickness of ~20 nm. Growth-per-cycle (GPC) values of ~1.6 and ~1.0 Å were obtained for HfO₂ and Al₂O₃, resulting in an average GPC of ~1.4 Å/cycle for the tri-layer stack. Following deposition, the coated PI films were released from the wafer for characterization and testing.

Mechanical performance of the deposited films was evaluated through in situ tensile testing to quantify elastic modulus, crack onset strain, crack density, fracture toughness, and interfacial shear strength. In addition, water vapor transmission rate (WVTR) measurements were performed according to ASTM F3299 to compare the moisture barrier performance of HfO₂, Al₂O₃, and HfO₂/Al₂O₃/HfO₂ coatings. Further, sorption testing with DI water was performed by submerging coated films at 37°C and periodically measuring changes in mass. For sorption studies, films were deposited on commercially available 25.4 µm Kapton HN substrates suspended within the ALD chamber to achieve conformal 3D encapsulation with full surface coverage.

We will present results that provide important insights into the viability and advantages of tri-layer HfO₂/Al₂O₃/HfO₂ thin films for encapsulation of chronic implantable devices. The proposed precision tri-layer coating demonstrated enhanced moisture barrier performance with improved mechanical robustness, including resistance to cracking and delamination. These combined properties indicate strong potential for long-term reliability in flexible and implantable biomedical device applications.

Solid state nanopores are commonly fabricated by etching through low isoelectric point (IEP) materials such as silicon dioxide or silicon nitride. As a result, these pores often have a negative charge around pH 8 (physiological pH). However, it is often desirable in biosensing applications to have the surfaces of microfluidic devices be positively charged to improve protein adhesion and promote crosslinking. Though a neutral or positive charge coating can be applied a surface through an amine-terminated self-assembled monolayer (SAM) such as 3-(aminopropyl) triethoxysilane, this approach may result in uncontrolled polymerization or an unstable film structure.

An alternative strategy for changing surface charge is to use atomic layer deposition (ALD) or molecular layer deposition (MLD),which are cyclic processes for depositing a thin film via exposure to reactive precursors in the vapor phase. These processes are attractive options for modifying the size and/or chemistry of solid state nanopores because they are highly precise and conformal. However, most water-stable inorganic thin films and organic polymer coatings that can be created through ALD and MLD similarly exhibit IEPs below 5. As a result, producing neutral or positively charged nanopore surfaces at physiological pH remains a significant challenge in nanopore surface engineering.

In this work, we investigate several new ALD/MLD coatings as candidate high-IEP surface modifications for solid state nanopores, comparing hafnium oxide to polyureas composed of 2,4-toluene diisocyanate (TDIC) combined with substituted diamines such as bis(2-aminopropyl)(methyl)amine (BAPMA) and 2,6-diaminopyridine (DAP). To measure surface charge, nanofluidic electrokinetic characterization (NEC) techniques were used, which involves the analysis of the ion current rectification behavior, surface conductance, and streaming current. With the exception of streaming current, which can be performed on flat surfaces, these characterization techniques involve properties which are unique to the nanofluidic nature of the system, offering a unique characterization tool for gathering surface properties. Overall, this work highlights the potential of ALD/MLD for surface modification of solid state nanopores to produce stable, high IEP surfaces as well as the utility of analyzing the breadth of physical phenomena present in a nanofluidic electrokinetic experiment.

In order to improve the surface quality of 4H-SiC for Schottky barrier diodes (SBDs), plasma oxynitridation (PON) was carried out on substrates using an ultrathin nickel film of 2 nm as the Schottky contacts, deposited via electron-beam evaporation. This passivation technique, until this publication, has no evidence in the literature for Schottky barrier devices based on 4H-SiC. Two pairs of devices were fabricated. In the first pair, the devices were fabricated following the ohmic contact formed using 100 nm of nickel, and the samples underwent the PON process for 20 minutes executed using an ICP-LAM, creating a 5 nm thick NyOx layer. Following this, the samples were annealed at 950 °C for 5 minutes, while for the second pair, the samples were not exposed to PON. Subsequently, a dip in HF 10% for 20 seconds was carried out to remove the passivation layer. A 2 nm layer of Ni was deposited on the top side to form the Schottky contact, and the devices were subjected to an annealing temperature of 650 °C. To create the metallic contact, 300 nm of Al was deposited by thermal evaporation and patterned into pads of 2 mm diameter without any shielding structure, finishing with a thermal treatment at 450 °C for 5 minutes. The influence of PON passivation on electrical performance and interface quality was evaluated. Electrical characteristics were measured using a parameter analyzer, revealing the rectification ratio and density of surface states. Also, the junction morphology was analyzed by high-resolution transmission electron microscopy (HRTEM).

The electrical results showed a difference between the passivated samples and unpassivated samples, where the passivated samples showed a rectification ratio about 6 times higher than the unpassivated ones. The leakage current at –5 V was 2 pA for passivated samples and 10 µA for unpassivated samples. Also, these results showed a shift in Schottky barrier height (SBH) values, besides improving the ideality factor to a maximum value of 1. The passivated samples also showed a difference between the surface states, where in this case, the surface states kept the same values as the unpassivated samples; however, the values shifted slightly far from the Ec band, possibly caused by band bending due to SBH surface density change.

For upcoming analysis, devices will receive a shielding structure for testing under temperature variation, and breakdown voltage tests will be performed to check reliability. Furthermore, characterizations such as XPS and Raman will be conducted for further investigation of the surface improvements achieved.

Amorphous indium–gallium–zinc oxide (a-IGZO) is widely explored for advanced thin-film applications due to its high carrier mobility and uniform amorphous phase. While its basic electrical properties are well-understood, the defect generation mechanisms and interface stability of oxide semiconductor thin films under high-energy ionizing radiation require deeper investigation. This study explores the radiation tolerance and defect dynamics of a-IGZO thin-film transistors (TFTs) compared to low-temperature polycrystalline silicon (LTPS) TFTs under gamma-ray exposure.

Devices were irradiated with a 60Co gamma-ray source at total doses of 0, 0.5, and 1 kGy. Evaluating the electrical parameters provided direct insights into the generation of interface states and trapped charges within the thin films. For the a-IGZO TFTs, the subthreshold swing (SS) remained essentially constant at ~0.09 V/dec despite the irradiation, indicating that the generation of new interface trap states at the dielectric/channel boundary was heavily suppressed. The threshold voltage (Vth) exhibited only a slight negative shift (ΔVth ≈ −0.87 V), suggesting a strong resilience of the amorphous oxide network against radiation-induced oxygen vacancy generation and positive charge trapping.

Conversely, the LTPS TFTs experienced drastic degradation. The Vth shifted negatively by −4.24 V, and the SS deteriorated significantly from 0.22 to 0.81 V/dec. This implies severe structural damage, likely due to the massive generation of deep trap states at the poly-Si grain boundaries and the gate dielectric interface.

Post-irradiation annealing further differentiated the materials: the amorphous network of a-IGZO allowed for partial structural relaxation and recovery of initial characteristics, whereas the crystalline damage in LTPS was largely irreversible under the same thermal budget. These findings underscore the superior defect immunity and interface stability of a-IGZO thin films in extreme environments.

We investigate how ALD oxidizer chemistry and chamber temperature impact the optical and morphological stability of metal/dielectric superlattices targeting epsilon-near-zero (ENZ) photonics. ENZ multilayers rely heavily on high-quality, continuous metal/dielectric interfaces, where increased roughness, oxidation, or aggregation increases effective extinction and dissipative losses, degrading the field enhancement and resonant behavior required for ENZ operation. Our superlattices alternate ~10 nm thermally evaporated metallic layers (Ag, Al, or 90/10 Ag/Al alloy) with ~1 nm ALD Al₂O₃ deposited from trimethyl-aluminum (TMA) using H₂O, O₃, or t-BuOH oxidizing co-reactants. Following ALD growth, multilayer ellipsometric responses become poorly described by otherwise reliable isolated (pre-ALD) metal film models, suggesting direct interaction between ALD processing conditions and the underlying metallic layers. To isolate these effects, we omit TMA and pulse oxidizer only under conditions typical of dielectric growth (~100 °C for H₂O/O₃ and ~280 °C for t-BuOH). Optical constants (n,k) and thicknesses were characterized through spectroscopic ellipsometry and transmission measurements, while morphology was characterized via SEM. We observe that oxidizer selection strongly impacts metallic optical behavior, with “harder” oxidizers producing the greatest optical degradation (O₃ > H₂O > t-BuOH). However, the comparatively “soft” t-BuOH chemistry requires elevated process temperatures to maintain a viable ALD growth window, introducing competing thermal aggregation in Ag films. Elevated temperatures drive Ag aggregation that increases with both temperature and exposure duration, while oxidizer chemistry primarily governs oxidation-driven optical degradation. Pure Al exhibits strong morphological stability but remains optically unfavorable for ENZ applications due to its comparatively high extinction coefficient and associated dissipation. Ag/Al alloy films demonstrate substantially improved aggregation resistance while largely preserving Ag-dominated optical behavior. Although elevated-temperature t-BuOH processes do not universally outperform alternative chemistries, the reduced optical degradation associated with “soft” oxidizer exposure, combined with the aggregation resistance of Ag/Al alloy films, shows strong promise for maintaining optical and morphological stability. Rather than constructing full ENZ devices directly, this work identifies degradation mechanisms and practical ALD processing windows necessary for reliable fabrication of ENZ-oriented metal/dielectric superlattice metamaterials.