AVS 71 Session TF-ThP: Thin Film Poster Session

Many approaches have been taken towards precise determination of overlayer thickness and (elemental) quantification of thin/ultrathin films (0.5-100nm). X-ray reflectivity (XRR) and X-ray photoelectron spectroscopy (XPS) as well as spectroscopic ellipsometry are commonly used to provide information about sample composition and layer depth (1-3). However, each of these methods has its limitations and specific techniques/sample geometries etc. might require extensive preparation and or do not allow for the use of ultra-high vacuum instrumentation. In addition, some of these methods as well as alternatives like Rutherford Backscattering/Elastic Recoil Detection Analysis (RBS/ERDS) require expensive equipment and/or access to large-scale facilities which is not always an alternative in every day-use cases.

Herein we report a broad comparison of different techniques including most of the above-mentioned ones (XPS, SEM-EDX, XRR, Ellipsometry) as well as Auger-Meitner Electron Spectroscopy (AMES), X-ray fluorescence (WXRF and GIXRF) and Raman spectroscopy for two sets of reference materials: HfO₂ on SiO₂/Si (4) and Fe/Ni thin films with different relative compositions.

We provide an approach for choosing different methods and method combinations depending on the requirements/sample surface size/roughness etc. for laboratory scale application beyond the reference material case. In addition, limitations of each method in terms of precision and applicability are discussed.

A roadmap is laid out for finding the most useful way of reaching the desired precision for quantification and thickness determination trying to use methods that are available to a large number of researchers in academia and industry.

(1)J. R. Shallenberger et al., "Oxide thickness determination by XPS, AES, SIMS, RBS and TEM," 1998 International Conference on Ion Implantation Technology. Proceedings (Cat. No.98EX144), Kyoto, Japan, 1999, pp. 79-82 vol.1, doi: 10.1109/IIT.1999.812056.

(2)Donald R Baer, Yung-Cheng Wang, David G Castner, Use of XPS to Quantify Thickness of Coatings on Nanoparticles, Microscopy Today, Volume 24, Issue 2, 1 March 2016, Pages 40–45, doi: 10.1017/S1551929516000109 [https://doi.org/10.1017/S1551929516000109]

(3)S. Terada, H. Murakami and K. Nishihagi, "Thickness and density measurement for new materials with combined X-ray technique," 2001 IEEE/SEMI Advanced Semiconductor Manufacturing Conference (IEEE Cat. No.01CH37160), Munich, Germany, 2001, pp. 125-130, doi: 10.1109/ASMC.2001.925630.

(4)https://www.bipm.org/documents/20126/46087117/CCQM-P190.pdf/5eaf9732-659b-fc91-c1b9-7d14f25112d1

The microelectronics industry continuously advances materials science to enhance integrated circuit (IC) performance. Interconnect structures are becoming critical as the transistor density increases. It also limits the chip speed due to increased resistance-capacitance (RC) delay. Traditionally, aluminum (Al) and silicon oxide (SiO₂) were utilized as metal and dielectric materials, which were replaced with copper (Cu) and low dielectric constant carbon-doped silicon oxide (low-k SiCOH, k < 4) to improve the RC delay and power consumption. Simultaneously, flexible electronics have gained attention, utilizing polymer substrates for applications like wearable devices and displays. However, integrating low-k flexible dielectric films with polymer-based substrates remains challenging due to the low glass transition temperatures of the substrates. Besides, it is essential to study the mechanical stability of materials for the integration of flexible electronic devices. This study explores the applicability of the low-k SiCOH thin films for flexible electronics by observing the effects of repeated mechanical bending tests.

Flexible low-k SiCOH films were produced onto flexible indium tin oxide-coated polyethylene naphthalate (ITO/PEN) substrates by plasma-enhanced chemical vapor deposition (PECVD) of a tetrakis (trimethylsilyloxy)silane precursor. The films were deposited at room temperature with the RF plasma power varied from 20 to 100 W. The films were subjected to bending tests with up to 10000 bending cycles. Mechanical characterization was performed by nanoindentation testing for the elastic modulus and hardness. Chemical bonds were characterized by Fourier transform infrared (FTIR) spectroscopy, and the atomic concentration was measured by X-ray photoelectron spectroscopy (XPS). The dielectric constant was measured from capacitance-voltage measurements.

The pristine SiCOH films had a mechanical strength of up to 9.1 GPa and a low k-value down to 2.00. The films were optically transparent, smooth, and hydrophobic. The prominent chemical peaks of CH_x, Si-CH₃, Si-O-Si, and Si-(CH₃)_x were identified for pristine films from the analysis of FTIR spectra. Upon repeated mechanical bending tests with bending cycles up to 10,000, the flexible SiCOH films maintained their transparency, smoothness, and hydrophobicity and showed a stable k-value below 4.0. No significant changes in the FTIR spectra were observed, and no cracks or delamination were observed in the films. The SiCOH films showed stable physical, chemical, and electrical properties under repeated mechanical bending.

Copper oxide (CuO) is a promising p-type semiconductor material with potential applications for energy and optoelectronic devices. In this study, we conducted a comprehensive saturation study within the scope of our initial attempts to grow CuO films by hollow-cathode plasma-assisted atomic layer deposition (HCP-ALD) followed by material characterization study to evaluate the structural, optical, and electrical properties of grown samples.

During CuO growth experiments, copper(II) hexafluoroacetylacetonate hydrate [Cu(hfac)₂·xH₂O] and O₂ plasma were used as the metal precursor and oxidizing agent, respectively. Saturation experiments performed on Si(100) substrates at 150 °C showed that the growth rate reached the saturation regime when the precursor pulse duration increased above a certain threshold. This demonstrated that surface-controlled self-limiting ALD behavior is achieved under appropriate plasma conditions. On the other hand, CuO formation was suppressed in the growths performed using only Ar plasma or O₂/Ar mixture, and metallic or non-stoichiometric structures were observed in some samples. These results confirmed the critical role of reactive oxygen species for CuO growth.

After determining the self-limiting growth window, the synthesis temperature was gradually increased to 250°C and film deposition studies were carried out on n-Si, sapphire, and quartz substrates. Initial transmittance measurements showed that as the temperature increased, the films exhibited higher transmittance in the visible region, thus increasing the film smoothness and quality.

X-ray diffraction (XRD) analyses revealed that the films grown in optimized O₂ plasma conditions contained polycrystalline CuO phases with (110), (002) and (111) planes. In Ar-oriented plasma environments, Cu₃N phases were observed, suggesting that oxidation was incomplete, or nitrogen doping occurred. These findings indicate that the HCP-ALD process is extremely sensitive to plasma composition and precursor-plasma interactions.

Hall effect, XPS, and TEM analyses are ongoing to determine the electrical, chemical, and structural properties. This research provides the basis for reliable CuO film growth at low temperature, and future process optimizations are aimed at the production of phase-pure, stoichiometric, and electrically active p-type CuO films.

The development of flexible electronics has advanced rapidly, with applications from sensors and energy storage to wearables. Among these, photodetectors (PDs) are of growing interest due to their potential roles in health monitoring, security, and optical communication. Zinc Oxide (ZnO), with its wide bandgap, stability under long-term light exposure, and high sensitivity to UV/visible radiation is an ideal material for such devices. However, fabricating thin film-based devices on textiles often affects their mechanical properties such as flexibility, durability, and washability. This work presents an approach that leverages low-temperature atomic layer deposition (ALD) of ZnO on cotton to achieve flexible PDs while preserving the inherent properties of cotton.

ZnO was deposited on cotton (woven bleached, 98 gsm) substrates using diethylzinc (DEZ) and H2O as Zn precursor and co-reactant respectively in a thermal ALD reactor at 120 °C. The unit ALD cycle in which 20 sccm N2 is used as the carrier gas consists of 0.5s DEZ pulse, 30s purge, 0.5s H2O pulse, 30s purge steps. Following the deposition of ZnO layers on cotton, interdigitated electrodes consisting of 200 nm Cr was evaporated by e-beam deposition to create the metal-semiconductor-metal (MSM) structures.

Indium antimonide (InSb), an important narrow direct bandgap semiconductor (0.17 eV at 300K), is highly optically sensitive in the mid-wave infrared (MWIR, 2-5 µm) spectrum. InSb-based devices are crucial for thermal imaging, spectroscopy, and astronomy as a result of atmospheric transmission and thermal emission characteristics. [1–5]. Its broad sensitivity (1.5-7 µm) also enables gas detection. However, reproducible growth of high-quality InSb epitaxial layers via molecular beam epitaxy (MBE) is challenging due to its low melting point. The epitaxial process requires lower growth temperatures and is prone to crystalline and surface defects. Optimal InSb growth occurs at 385°C with a V: III ratio of 1.2. Accurate temperature control is challenging at these lower temperatures, which further complicates the narrow optimal growth range and can negatively impact the film properties. Controlling surface morphology during growth is critical for advanced optoelectronic devices.

Bismuth surfactancy in MBE has been shown to improve surface morphologies in many III-V materials [6, 7]. A very low bismuth flux can modify the adlayer surface before desorption, and has been shown to improve the morphology of the surface in multiple materials [6–8].To our knowledge, no systematic studies have been reported on the effects of Bi surfactancy on MBE growth of InSb thin films [6, 7, 9]. This study investigates the effects of Bi surfactancy on InSb MBE growth over a wide range of growth temperatures (280-410°C). Two series of homoepitaxial InSb(100) films were grown by MBE: a control set and a set grown with Bi surfactancy, with identical parameters otherwise. The temperature was calibrated using the RHEED pattern transition c(4x4) to a(1x3), which is reported to occur at 370°C [10, 11]. The surface morphology and elemental distribution were analyzed using AFM and SEM-EDS, while XPS confirmed the absence of Bi incorporation. Finally, TEM was performed to analyze the film’s lattice structure.

NiO is a wide-band transparent insulator, exhibiting a bandgap of 3.6 eV-4.0 eV [1]. It is an antiferromagnetic material with a Néel temperature of 523 K. NiO crystallizes in a NaCl-type face-centered cubic structure with a lattice parameter of 0.417 nm. The antiferromagnetic order in NiO is due to the antiferromagnetic alignment of ferromagnetic (111) planes along the [111] crystallographic direction[2].Below T_N,magnetic ordering induces a rhombohedral distortion.This study presents the growth of (111)-oriented NiO thin films on (0001)-sapphire substrate using pulsed laser deposition (PLD). DC magnetic susceptibility measurements of the films confirm that they maintain antiferromagnetic ordering at room temperature. Additionally, this finding is supported by the observation of two-magnon(2M) Raman scattering.The relative intensity of this 2M mode compared to a neighboring phonon mode further highlights the bulk-like antiferromagnetic state in the thin films. NiO thin films were irradiated utilizing an Au ion beam at varying fluences.X-ray diffraction (XRD) analysis indicated a broadening and a shift towards a higher 2θ value in the NiO(111) peak with increased fluence, which suggests a reduction in the out-of-plane lattice parameters.Atomic force microscopy (AFM) results demonstrated increased surface roughness of the films post-irradiation.DC magnetic susceptibility measurements showed a decrease in the magnetic moment and Néel temperature at the higher fluence of 5x10¹² ions/cm², attributable to defects induced by the ion beam irradiation. Raman spectroscopy further supported these findings, with significant changes observed in the two magnon peaks,which experienced a redshift and broadening in the irradiated samples. This shift and broadening signify a reduced antiferromagnetic coupling due to high-energy ion beam irradiation.Additionally,the 1P peak at 575 cm⁻¹ exhibited a redshift and broadening in the irradiated samples. The ratio of I_1P/I_2P increased significantly upon irradiation and even surpassed one at the higher fluence value, indicating a higher degree of disorder induced by the ion beams. Overall, this study demonstrates the successful deposition of (111)-oriented NiO thin films via PLD, exhibiting magnetic properties similar to bulk NiO, and the tuning of the 2M peak by ion beam irradiation.These findings highlight the potential of NiO thin films for exploring fundamental magnetic interactions and developing optoelectronic applications.

[1]H. Ohta et al., Thin Solid Films 445, 317(2003)

[2]S. M. Rezende et al., J. Appl. Phys. 126, 151101(2019)

Porous materials are of great interest in various fields such as optics, biology, energy, and catalysis. While energy and catalysis applications focus on achieving high porosity, optical applications demand not only low-refractive-index (RI) materials that overcome the limitations of naturally occurring substances but also the formation of a smooth RI gradient from the substrate to air. This requires both high porosity and precise control over it. Conventional methods for fabricating porous structures, including templating, self-assembly, and zeolitic synthesis, typically rely on sacrificial templates, which must be removed through chemical etching or thermal treatment, potentially damaging the host material and limiting scalability.

In this study, we present mesoporous metal fluoride films composed of MgF₂ and LaF₃, fabricated using a simple, template-free, one-step precursor-derived method. Pores spontaneously form during solidification due to the inherent instability of La(CF₃OO)₃. Electrostatic interactions between Mg(CF₃OO)₂ and La(CF₃OO)₃ precursors enable the controlled formation of mesoporous structures with finely tunable RI values ranging from 1.37 to 1.16. By stacking layers of MgF₂(1–x)–LaF₃(x) with different compositions, a graded refractive index (GRIN) antireflection coating (ARC) is achieved, delivering excellent broadband performance with an average transmittance of ~98.03% in the 400–1100 nm range. Despite these advances, a refractive index gap still remains between the fluoride composite and air, primarily due to the inherently high RI of LaF₃.

To address this, we propose an innovative approach that enables precise tuning of porosity using micelle-assisted MgF₂ precursor intermediates. As micellization increases the size of the MgF₂ precursor clusters, the resulting solidified MgF₂ grains and the intergranular voids between them also increase, allowing for the fabrication of MgF₂ structures with ultra-low RI (~1.04) and fine RI control increments. When applied as a GRIN ARC on quartz substrates, this strategy achieves an average transmittance of ~97.96% across the 250–1100 nm spectral range.

This research was supported by Nano-Material Technology Development Program through the National Research Foundation of Korea (NRF) funded by Ministry of Science and ICT (grant no. 2021M3H4A3A01055854).

Selective metal deposition on dielectric surfaces (MoD) is essential for advanced microelectronics applications, particularly in the context of the ongoing transition from 2D to 3D device architectures. However, achieving this selectivity remains challenging due to the similar surface chemistries of many dielectrics. In this work, we introduce a new approach for selectively controlling metal deposition on dielectric substrates by area-selective atomic layer deposition (AS-ALD) using an aldehyde inhibitor. Butyraldehyde was employed as an inhibitor to selectively adsorb on and passivate Al₂O₃ surfaces while leaving SiO₂ surfaces unaffected. As a result, the adsorption of the ruthenium precursor, [Ru(TMM)(CO)₃], was prevented on the aldehyde-inhibited Al₂O₃ surface in subsequent Ru ALD cycles and the Ru grew selectively on the SiO₂ surface. The inhibitor adsorption behavior, surface blocking properties, and film selectivity were investigated using water contact angle, ellipsometry, scanning electron microscopy (SEM), transmission electron microscopy (TEM), and X-ray photoelectron spectroscopy (XPS) measurements. We believe that AS-ALD using aldehyde inhibitors offers a promising pathway for area-selective MoD in general, and for the integration of Ru into complex interconnects and 3D nanoarchitectures in particular, for next-generation microelectronic devices.

Sulfide-based all-solid-state batteries (ASSBs) have emerged as a compelling alternative to conventional Li-ion batteries owing to their superior gravimetric and volumetric energy densities and enhanced safety characteristics. However, sulfide electrolytes such as Li₆PS₅Cl (LPSCl) are prone to chemical and electrochemical degradation upon contact with cathode and anode materials during cycling, giving rise to significant chemo-mechanical instability. Additionally, LPSCl exhibits extreme sensitivity to moisture and air exposure, leading to the release of toxic H₂S gas and the formation of resistive, electrochemically inactive interphases.Atomic layer deposition (ALD) offers a promising strategy to mitigate LPSCl degradation by depositing an ultrathin, conformal buffer layer on the LPSCl that is chemically and electrochemically stable. When properly engineered, this coating not only suppresses interfacial decomposition but can also improve ionic conductivity and mechanical integrity while minimizing electronic conductivity. Despite its potential, the interfacial reaction mechanisms between ALD precursors and LPSCl remain poorly understood.

In this study, we elucidate the reaction mechanism of Al₂O₃ ALD using trimethylaluminum (TMA) and H₂O on LPSCl through a combination of in situ and ex situ characterizations supported by density functional theory (DFT) calculations. In situ Fourier transform infrared (FTIR) spectroscopy and ex situ nuclear magnetic resonance (NMR) measurements revealed the surface functional groups involved in TMA chemisorption and subsequent H₂O reactions during the initial ALD cycle. Continued ALD cycling demonstrated steady Al₂O₃ growth, as observed by FTIR. Ex situ X-ray photoelectron spectroscopy (XPS) confirmed the formation of new interfacial bonds, while ex situ Raman spectroscopy verified the structural preservation of bulk LPSCl after ALD. Complementary DFT calculations enabled identification of the most thermodynamically favorable reaction pathways for precursor adsorption and film growth.Together, these results provide mechanistic insight into the ALD process on sulfide electrolytes and offer design principles for optimizing interfacial coatings in ASSBs, with implications for broader applications across sulfide-based solid electrolyte systems.

Globally there has been a push for renewable energy sources that can serve in the future as an alternative to the conventional energy sources in existence today that continually lead to environmental degradation. In line with this, research efforts have been geared towards studying the sustainability and reliability of these possible alternatives. In this light, hydrogen generation through the splitting of water is proposed.

This study investigates the electrochemical and structural properties of single crystal ruthenium dioxide (RuO₂), focusing on the effect of varying oxidation state (sub-stoichiometric-RuO2-x, stoichiometric RuO2, and hyper-stoichiometric RuO2+x) and lattice strain on electrochemical water splitting particularly in the oxygen evolution reactions (OER) in 0.1M KOH. Electrochemical Impedance Spectroscopy (EIS) and Cyclic Voltammetry (CV) were used to characterize RuO₂’s behavior in alkaline environments, extracting key parameters such as solution resistance (R_s), charge transfer resistance (R_ct), and double-layer capacitance (C_dl). RuO₂ thin films were grown through the Pulsed Laser Deposition (PLD) on single-crystal sapphire (Al₂O₃) substrates at varying oxygen pressures (25–75 mTorr) at substrate temperatures 600°C at 4800 pulses. Structural characterization was performed using X-ray diffraction (XRD), X-ray Photoelectron spectroscopy (XPS), X-ray absorption spectroscopy (XAS), Non-Rutherford Backscattering Spectrometry (NRBS), Atomic Force Microscopy (AFM) and Scanning Electron Microscopy (SEM). Atomic modelling was carried out using Vesta to understand the epitaxial growth and relationship between the film and substrate. The films' electrochemical performance was evaluated via CV and Linear Sweep Voltammetry (LSV), with emphasis on the effect of crystal structure and oxidation state on OER activity. These results, validate RuO₂ as a promising material for water splitting applicationswell as illustrates the importance of deposition ambient control in tailoring the properties of RuO₂ film, which is a fundamental part of the design and optimization of an efficient electrode material.

This work was supported by the NSF-PREM on the Collaborative Research and Education in Advanced Materials Center (via grant # DMR-2425119) and the DOE EFRC on the Center for Electrochemical Dynamics and Reactions on Surfaces (CEDARS) via grant # DE-SC0023415.

In our world today, despite the efforts of various governments and institutions, fossil fuel unfortunately remains the main source of electricity in the United States and globally. These energy sources create toxic emissions, pollute the atmosphere while promoting climate change. In line with the global shift towards developing sustainable fuels, efforts are needed to develop material systems and processes that can convert molecules in the air (e.g., water, carbon dioxide, and nitrogen) into renewable energy products. In response to preventing a continued dependence on fossil fuels, the splitting of water to produce hydrogen fuel and oxygen is proposed.

In this study Pulsed laser deposition (PLD) technique has been used to grow titanium oxynitride (TiNO) thin films on sapphire (Al₂O₃) for renewable energy applications. A pulsed Krypton Fluoride (KrF) excimer laser (Wavelength=248nm, pulse duration=30ns) was used, with a laser repetition rate of 10 Hz, 6000 pulses, and a deposition temperature of 600°C.

Structural properties of the films were investigated using X-ray Diffraction and Reflection (XRD, XRR), X-ray Photoelectron Spectroscopy (XPS), Atomic Force Microscopy (AFM) and Scanning Electron Microscopy. Structural modelling was performed using Vesta to understand the epitaxial growth and relationship between the film and substrate.

Electrochemical Impedance Spectroscopy (EIS) and Cyclic Voltammetry (CV) were used to characterize titanium oxynitride (TiNO) behavior in alkaline environments, extracting key parameters such as solution resistance (Rs), charge transfer resistance (Rct), and double-layer capacitance (Cdl).EIS data, analyzed with Nyquist plots and Randles circuit modeling, these results confirmed the presence of both resistive and capacitive elements, validating as a promising material for water splitting applications.

This work was supported by the NSF-PREM on the Collaborative Research and Education in Advanced Materials Center (via grant # DMR-2425119) and the DOE EFRC on the Center for Electrochemical Dynamics and Reactions on Surfaces (CEDARS) via grant # DE-SC0023415.

This research focuses on the study of hydrogen and oxygen evolution reaction kinetics of ruthenium dioxide (RuO₂) thin films in alkaline and acidic media using Tafel slope analysis. The study has given insights into the rate-determining step, kinetics, and mechanisms that govern electrochemical reactions at the RuO₂ electrode and electrolyte interface. The Butler-Volmer equation was also combined with the Tafel equation at higher overpotentials, which has allowed us to establish a connection between the magnitude of the Tafel Slope and the mechanism of the rate-determining step of the reaction. RuO₂ is an ideal candidate as an electrocatalyst because it is intrinsically stable, corrosion-resistant, and has low resistivity, making it viable for water splitting applications. The RuO₂ films were grown on (0001) plane Al₂O₃ under different deposition conditions, using a pulsed laser deposition method. A three-electrode cell and KOH and HClO₄ electrolytes with different concentrations were used for Linear Sweep Voltammetry testing. The OER and HER overpotential (h) was plotted as a function of log(j), for which the Tafel slope is calculated using the Tafel equation, h = a + blog(j). For example, Tafel Slope results in 1.0M KOH provide b_OER = 115 mVdec^-1 for the 4800-pulse sample and, b_OER = 150 mVdec^-1 for the 2100-pulse sample. While Tafel Slope results in 0.1M HClO₄ provide b_HER = 115 mVdec^-1 for the 4800-pulse sample and, b_HER = 160 mVdec^-1 for the 2100-pulse sample. This data suggests a thicker RuO₂ film will result in more kinetic activity on the surface in alkaline and acidic media. Future work will consist of different characterization methods to verify these results and compare our experimental data to theoretical data for further understanding the mechanisms and steps limiting the reactions of RuO₂ thin films as a working electrode.

The advancement of TiO₂-based memristors is critical for next-generation neuromorphic systems and non-volatile memory devices due to their simple structure, scalability, and stable resistive switching properties. However, achieving high endurance and uniform switching remains a major challenge. Precise control of oxygen vacancy distribution is essential to improve device reliability and performance.

In this work, we propose a thermally assisted oxygen plasma process with RF power modulation for the fabrication of glass/ITO/TiO₂/TiO₂₋ₓ/Ag memristors. The plasma treatment was conducted at various RF powers (0–80 W) under optimized thermal conditions to investigate its influence on resistive switching endurance, retention stability, and conduction mechanisms. Device performance was evaluated through I–V measurements, endurance cycling, and retention tests.

Acknowledgements: This work was supported by Innovative Human Resource Development for Local Intellectualization program through the Institute of Information & Communications Technology Planning & Evaluation (IITP) grant funded by the Korea government (MSIT) IITP-2025-RS-2020-II201462 (50%), in part by the Basic Science Research Program through the National Research Foundation of Korea (NRF) funded by Ministry of Education under Grant RS-2020-NR049604 (50%)

The use of silicon (Si) in the optics and photonics industry is very popular due to its electronic properties and compatibility with CMOS technology, as well as other semiconductor devices. Germanium (Ge) is an alternative material that can be grown on Si substrates and is now used in photonic devices. However, both Ge and Si suffer from non-radiative processes due to being indirect band-gap materials. Unlike Si, Ge is a quasi-direct bandgap semiconductor and can be band engineered through strain or Sn alloying. Similar to Ge, germanium-tin (GeSn) has shown potential in the photonics industry with a greater focus on light sources. Photoluminescence spectroscopy was carried out using a NIR 980nm laser to probe the optical properties of the GeSn/Ge/Si samples. These measurements were analyzed with reference to Rutherford backscattering and cross-sectional TEM.