Zirconia Thin Films Research Articles

Electrode Elastic Modulus as the Dominant Factor in the Capping Effect in Ferroelectric Hafnium Zirconium Oxide Thin Films.

The discovery of ferroelectricity in hafnia based thin films has catalyzed significant research focused on understanding the ferroelectric property origins and means to increase stability of the ferroelectric phase. Prior studies have revealed that biaxial tensile stress via an electrode "capping effect" is a suspected ferroelectric phase stabilization mechanism. This effect is commonly reported to stem from a coefficient of thermal expansion (CTE) incongruency between the hafnia and top electrode. Despite reported correlations between ferroelectric phase fraction and electrode CTE, the thick silicon substrate dominates the mechanics and CTE-related stresses, negating any dominant contribution from an electrode CTE mismatch toward the capping effect. In this work, these discrepancies are reconciled, and the origin of these differences deriving from electrode elastic modulus, not CTE, is demonstrated. Pt/M/TaN/Hf0.5Zr0.5O2/TaN/Si devices, where M is platinum, TaN, iridium, tungsten, and ruthenium, were fabricated. Sin2(ψ)-based X-ray diffraction measurements of biaxial stress in the HZO layer reveal a strong correlation between biaxial stress, remanent polarization, and electrode elastic modulus. Conversely, a low correlation exists between the electrode CTE, HZO biaxial stress, and remanent polarization. A higher elastic modulus enhances the resistance to electrode elastic deformation, which intensifies the capping effect during crystallization, and culminates in the tandem restriction of out-of-plane hafnia volume expansion and preferential orientation of the polar c-axis normal to the plane. These behaviors concomitantly increase the ferroelectric phase stability and polarization magnitude. This work provides electrode material selection guidelines toward the development of high-performing ferroelectric hafnia into microelectronic devices, such as nonvolatile memories.

Phase evolution and surface analysis of electron beam evaporated calcium and yttria-stabilized zirconia thin films

The manuscript investigates the structural and morphological characteristics of thin films of calcium stabilized zirconia (CSZ, 16 mol % CaO), synthesized through electron beam deposition on silicon wafers, with a focus on the phase evolution during annealing at 800 °C. The study compares these properties with yttria stabilized zirconia (YSZ, 8 mol % Y2O3) thin films. Rutherford backscattering spectrometry validates film composition, with thicknesses of ∼315 nm for CSZ and ∼285 nm for YSZ. X-ray diffraction initially identifies an amorphous structure, transitioning to a cubic phase post-annealing, with average crystallite sizes of 18.07 nm for CSZ and 16.22 nm for YSZ, corroborated by Raman spectroscopy. The lattice parameters are determined using Rietveld refinement. Surface morphology is investigated through field emission scanning electron microscope and atomic force microscopy shows a reduction in surface roughness from 6.05 nm to 1.34 nm for CSZ and from 4.54 nm to 1.64 nm for YSZ post-annealing, indicating enhanced homogeneity. Elemental distribution analysis using energy dispersive X-ray spectroscopy confirms film uniformity. The study provides insights into the structural evolution and morphological characteristics of calcium stabilized zirconia thin films, particularly at the nanoscale level, offering valuable contributions to its industrial applicability.

Synthesis and Characterization of Zirconia-Based Ceramics: A Comprehensive Exploration of Film Formation and Mixed Metal Oxide Nanoparticle Synthesis

Due to its strong ionic conductivity and superior mechanical qualities, zirconia-based ceramics are frequently used in electrochemical devices. Today, zirconium oxychloride octahydrate and ethanol have been developed for the purpose of reducing zirconium thin films on glass, single-crystal silicon p-type, substrates. The phase composition and properties of the films, as well as the physicochemical processes involved in film formation, have all been investigated. Zirconia mixed metal oxide nanoparticles with various physicochemical properties can be created using a variety of synthetic processes in conjunction with additional variables like concentration, PH, type of precursor utilized, etc. In order to create zirconia mixed metal oxide nanoparticles, many synthetic techniques, including sol-gel, hydrothermal, and coprecipitation methods are discussed in this article.

Optimization of molar concentrations for enhanced crystallinity and bandgap tuning of ZrO2 thin films via spray pyrolysis for advanced optical applications

In this study, Zirconium oxide (ZrO2) thin films were synthesized on glass substrates at 400°C using the Spray Pyrolysis method, due to its simplicity, cost-effectiveness, and precise control. The films were prepared at varying molar concentrations (0.1, 0.15, and 0.2 M) and analyzed for their structural, optical, and morphological properties. X-ray diffraction (XRD) confirmed that all films exhibited a tetragonal crystalline structure with a preferred orientation along the (101) plane. The crystallite size, calculated using the Scherrer equation, reached a maximum of 27.26 nm at 0.2 M concentration, indicating improved crystallinity with higher concentration. Optical studies revealed a decrease in transmittance and an increase in absorbance in the visible region as the concentration increased, accompanied by a reduction in the optical band gap from 3.84 to 3.57 eV and an increase in Urbach energy. Scanning Electron Microscopy (SEM) images showed that the films had a dense and smooth morphology, while Energy Dispersive X-ray (EDX) analysis confirmed the elemental presence of zirconium and oxygen in the films.

Optimization of ferroelectricity and endurance of hafnium zirconium oxide thin films by controlling element inhomogeneity

Optimization of ferroelectricity and endurance of hafnium zirconium oxide thin films by controlling element inhomogeneity

Phase Transformations Driving Biaxial Stress Reduction During Wake‐Up of Ferroelectric Hafnium Zirconium Oxide Thin Films

AbstractBiaxial stress is identified to play an important role in the polar orthorhombic phase stability in hafnium oxide‐based ferroelectric thin films. However, the stress state during various stages of wake‐up has not yet been quantified. In this work, the stress evolution with field cycling in hafnium zirconium oxide capacitors is evaluated. The remanent polarization of a 20 nm thick hafnium zirconium oxide thin film increases from 9.80 to 15.0 µC cm−2 following 106 field cycles. This increase in remanent polarization is accompanied by a decrease in relative permittivity that indicates that a phase transformation has occurred. The presence of a phase transformation is supported by nano‐Fourier transform infrared spectroscopy measurements and scanning transmission electron microscopy that show an increase in ferroelectric phase content following wake‐up. The stress of individual devices field cycled between pristine and 106 cycles is quantified using the sin2(ψ) technique, and the biaxial stress is observed to decrease from 4.3 ± 0.2 to 3.2 ± 0.3 GPa. The decrease in stress is attributed, in part, to a phase transformation from the antipolar Pbca phase to the ferroelectric Pca21 phase. This work provides new insight into the mechanisms controlling and/or accompanying polarization wake‐up in hafnium oxide‐based ferroelectrics.

Oxygen diffusion coefficients in ferroelectric hafnium zirconium oxide thin films

Oxygen diffusion coefficients in the metastable ferroelectric phase of polycrystalline hafnium zirconium oxide (HZO) thin films have been quantified using 18O tracers and time-of-flight secondary ion mass spectrometry. 11.5 nm thick HZO films containing 16O were deposited by plasma-enhanced atomic layer deposition followed by post-metallization annealing to crystallize into the ferroelectric phase. A 1.2 nm thick HZO layer containing 18O was then deposited using thermal atomic layer deposition with H218O as a reactant. Thermal anneals were conducted at 300, 350, and 400 °C and the ferroelectric phase confirmed after the anneals by x-ray diffraction, infrared spectroscopy, and electrical property measurements. 18O depth profiles were measured and fit with a thin film diffusion equation to determine the oxygen diffusion coefficients. Oxygen diffusion coefficients ranged from approximately 2 × 10−18 cm2/s at 300 °C to 5 × 10−17 cm2/s at 400 °C with an activation energy of 1.02 ± 0.24 eV.

High stability and photocatalytic activity of N-doped ZrO2 thin films

Undoped and nitrogen-doped ZrO2 thin films were obtained by HiPIMS on ITO/glass substrates. To stabilize their structure, the films were subjected to a heat treatment. The properties of the heat-treated films (structure, morphology, elemental composition of the atomic species at the films surface, optical band gap, wettability and oxidation performance of Rhodamine B) were correlated. Some properties of the studied films were compared with the ones of the as-deposited films previously reported. By nitrogen doping, zirconia thin film modifies its fundamental absorption edge, becoming absorbent in the visible domain. The heat treatment improves the hydrophilic properties of both undoped and N-doped films, the last one becoming super-hydrophilic. The photocatalytic activity under UV was investigated for three RhB concentrations. The degradation efficiency is higher than 90 % for both undoped and N-doped ZrO2 films, being better for the N-doped film. The studied films are exceptionally stable, keeping their oxidation properties almost unchanged after five degradation cycles, with a special remark for the N-doped film (the degradation efficiency around 93 %). The role of ITO substrate in charge carriers separation was investigated, based on the allowed band edges values, determined both for the films and ITO.

Nanoscale Phase and Orientation Mapping in Multiphase Polycrystalline Hafnium Zirconium Oxide Thin Films Using 4D-STEM and Automated Diffraction Indexing.

Ferroelectric hafnium zirconium oxide (HZO) holds promise for nextgeneration memory and transistors due to its superior scalability and seamless integration with complementary metal-oxide-semiconductor processing. A major challenge in developing this emerging ferroelectric material is the metastable nature of the non-centrosymmetric polar phase responsible for ferroelectricity, resulting in a coexistence of both polar and non-polar phases with uneven grain sizes and random orientations. Due to the structural similarity between the multiple phases and the nanoscale dimensions of the thin film devices, accurate measurement of phase-specific information remains challenging. Here, the application of 4D scanning transmission electron microscopy is demonstrated with automated electron diffraction pattern indexing to analyze multiphase polycrystalline HZO thin films, enabling the characterization of crystallographic phase and orientation across large working areas on the order of hundreds of nanometers. This approach offers a powerful characterization framework to produce a quantitative and statistically robust analysis of the intricate structure of HZO films by uncovering phase composition, polarization axis alignment, and unique phase distribution within the HZO film. This study introduces a novel approach for analyzing ferroelectric HZO, facilitating reliable characterization of process-structure-property relationships imperative to accelerating the growth optimization, performance, and successful implementation of ferroelectric HZO in devices.

Highly crystalline yttria‐stabilized zirconia and titania thin films on plastic substrates via sol‐gel transfer process

AbstractWe prepared yttria‐stabilized zirconia (YSZ) and titania crystalline thin films on polycarbonate (PC) substrates by the sol‐gel transfer technique that we have developed recently. Precursor gel films were deposited by spin‐coating on a polyimide/polyvinylpyrrolidone mixture layer on Si(100) substrates, and then were calcined at 600°C. The spin‐coating and the calcination were cycled, followed by final firing at 600–1000°C, to obtain 140–190 nm thick, YSZ and titania crystalline thin films. The film densification progressed as the final firing temperature increased, where the porosity calculated from the refractive index decreased down to a few percent. The film thus obtained was heated at 190°C on a hot plate, and a PC substrate was pressed on the film to transfer it to the PC substrate. The transferability quantified by image analysis of the film area was found to be significantly different between the YSZ and titania films. In the case of YSZ films, the area of silicon that was fractured and adhered to the transferred film increased significantly with increasing firing temperature, leading to a decrease down to 0% in the fraction of the successful transfer area without such a damage. On the other hand, the fraction of the successful transfer area remained around 90% irrespective of the firing temperature for the titania films. The surface of the titania films that were fired at 800–1000°C and transferred to PC substrates had voids of several tens nm scale, which may have been formed during anatase‐to‐rutile phase transformation. We thought that the reduced titania/Si(100) contact area due to such void formation facilitated the delamination of the titania films from Si(100) substrates. High temperature firing, which promotes crystallization and densification of films, thus affects differently the film transferability to plastic substrates, depending on the type of films. The work also suggested possible use of titania films as release‐assisting layers.

Zirconium oxide thin films deposited via DC magnetron sputtering: corrosion and morphological investigation

Purpose The purpose of this study is to investigate the structural, surface roughness and corrosion properties of the zirconium oxide thin films deposited onto SS304 substrates using the direct current (DC) magnetron sputtering technique. Design/methodology/approach DC sputtering at different powers – 80, 100 and 120 W – was used to deposit ZrO2 thin films onto different substrates (Si/SS304) without annealing of the substrate. Atomic force microscope (AFM), energy-dispersive X-ray spectroscopy (EDS), Tafel extrapolation and contact angle techniques were applied to investigate the surface roughness, chemical compositions, corrosion behavior and hydrophobicity of these films. Findings Results showed that the thickness of the deposited film increased with power increase, while the corrosion current decreased with power increase. AFM images indicated that the surface roughness decreased with an increase in DC power. EDS analysis showed that the thin film has a stoichiometric ZrO2 (Zr:O 1:2) composition with basic uniformity. Water contact angle measurements indicated that the hydrophobicity of the synthesized films decreased with an increase in surface roughness. Originality/value DC magnetron sputtering technique is infrequently used to deposition thin films. The obtained thin films showed good hydrophobic and anticorrosion properties. Finally, results are compared with other deposition techniques.

The Effect of Deposition Temperature on Structural, Morphological, and Dielectric Properties of Yttria-Doped Zirconia Thin Films

The aim of this study was to investigate the effect of deposition temperature on the structural, optical, morphological, and dielectric properties of yttria-stabilised zirconia (YSZ) films prepared by sol-gel spin-coating method. X-ray diffraction (XRD) measurements of YSZ films showed that the peaks of the cubic phase were prominent and the peak intensities increased with deposition temperature. The crystallite size, dislocation density, and microstrain of the thin films were identified by XRD. It was observed that the crystal size of the YSZ thin films increased from 16 nm to 22 nm with the deposition temperature. The surface roughness of the thin films was found to have changed as revealed by Atomic Force Microscopy (AFM) measurements. The roughness increased from 7.72 nm to 11.92 nm with increasing temperature. The optical transmittance of the YSZ thin films was investigated in the wavelength range 200-900 nm and was found to increase slightly with increasing deposition temperature. Metal-Oxide-Semiconductor (MOS) devices were fabricated from these YSZ materials for dielectric characterization. The dielectric properties of the Ag/YSZ/n-Si MOS structure were investigated. It was found that the capacitance, conductivity and other dielectric parameters of these structures are strongly frequency dependent.

Possibility and Optimized Conditions for Spontaneous Superlattice Formation in Stabilized Zirconia Thin Films Grown Under In Situ Magnetic Field

Possibility and Optimized Conditions for Spontaneous Superlattice Formation in Stabilized Zirconia Thin Films Grown Under In Situ Magnetic Field

Optimizing the Crystallinity of a ZrO2 Thin Film Insulator for InGaZnO‐Based Metal–Insulator–Semiconductor Capacitors

AbstractThe utilization of a zirconium oxide (ZrO2) thin film as the insulator in a metal–insulator–semiconductor (MIS) capacitor to enhance the characteristics of thin‐film transistors is investigated. Although the high crystallinity of ZrO2 is favorable to achieving higher capacitance density in metal–insulator–metal capacitors with ZrO2 thin films, it decreases the capacitance with increasing applied bias in Mo/ZrO2/InGaZnO (IGZO)‐structured MIS capacitors. Through comprehensive physical, chemical, and electrical characterizations, this study investigated the mechanism underlying the decreasing capacitance with increasing the applied bias in the accumulation state of the Mo/ZrO2/IGZO‐structured MIS capacitor depending on the crystallinity of ZrO2. Furthermore, the investigation identifies the optimal crystal structure of ZrO2 thin films for IGZO‐based MIS capacitors, highlighting the importance of forming meso‐crystalline structures in high dielectric constant (k) materials to enhance the k value and mitigating the decrease in capacitance caused by the accumulated carrier loss through grain boundaries of ZrO2.

Investigation of electrical, corporeal, ocular, and aquaphobic properties of zirconia thin-films by varying substrate temperature for high voltage insulators

ABSTRACT The addition of ZrO2 nanoparticles to porcelain insulators and its influence on their electrical and corporeal characteristics are studied throughout a wide range of sintering temperatures. The DC magnetron sputtering with a 99.99% pure zirconium target is utilized to create zirconium oxide thin films on glass and silicon substrates in a 12-inch-diameter chamber. Different temperatures were used to sinter the produced samples (room temperature (RT) − 400°C) for 1 h with gas pressure of 15 mTorr for all depositions. Scanning electron microscopy (SEM) was used to characterize the microstructures of a subset of the samples. In order to assess the physical and microphysical changes brought on by an increase in substrate temperature, the phase composition of various nanocomposites samples was determined using X-ray diffraction (XRD). The breakdown strength, electrical resistivity, and dielectric constant were measured to assess the electrical attributes of the various samples. The obtained findings showed that the electrical and corporeal characteristics of samples sintered at RT were the best. In addition, the sample of nanocomposite porcelain sintered at room temperature has excellent insulating qualities, confirming the possibility of electro-technical porcelain manufacture (water contact angle = 103.5º), dielectric constant = 24.4, refractive index = 2.15, and bandgap = 5.33.

Fabrication of YSZ ceramic thin films with sol-gel method for mixed potential-type zirconia-based NO2 sensor

In this work, yttria-stabilized zirconia (YSZ) thin films were prepared by sol-gel and spin-coating methods, which are simple and inexpensive, with good film quality and excellent electrical conductivity. Using this film, a YSZ film mixed-potential type NO2 gas sensor with NiO as the sensitive electrode material was fabricated. The films had the best dielectric properties when spin-coated four times, and the sensors had the highest response (48 mV–100 ppm NO2) as well as the best sensitivity (14.8 mV/decade for 5–20 ppm NO2 and 42 mV/decade for 20–500 ppm NO2). The YSZ thin-film gas sensor operates at a lower temperature, with an optimum operating temperature of 550 °C, and the power consumption of the sensor has been reduced by approximately 46 % or more compared to conventional bulk YSZ NO2 gas sensors. This provides a very effective direction for the low-power design of high-temperature devices such as the YSZ gas sensor. In addition, thin-film devices are more conducive to integrating sensors into microelectronic circuits, greatly improving the application scenarios for such devices. This sensor has excellent repeatability, very good selectivity, and outstanding long-term stability over 30 days of continuous measurement. In conclusion, based on the excellent sensing performance and low power consumption of the YSZ thin-film gas sensor, the sensor has a promising future for in-situ monitoring of NOx.

Mechanical strength of different zirconia thin films in relation with their thickness

Zirconia layers with different fractions of tetragonal phase and thicknesses were subjected to multi-cracking tests. Cracks perpendicular to the tensile direction appeared. Cross sections showed that cracks blunt into the substrate. The ratio of crack spacing at saturation to layer thickness decreases when the layer thickness increases. Unit cell modelling has been used to establish a relationship between the crack spacing and the strength of the layer. The relation falls within both bounds of Hu and Evans model. The relation is insensitive to the tetragonal zirconia fraction.

Low‐Power and Fast‐Response Limiting Current‐Type Oxygen Microsensor with a Wide Range Oxygen Concentration

In this study, we fabricated limiting current‐type oxygen microsensors capable of sensing a wide range of oxygen concentrations. The oxygen microsensors consist of yttria‐stabilized zirconia thin films on spiral Ta2O5 diffusion layers and high‐temperature micro‐hotplates. At temperatures above 575 °C, we observed a clear limiting current that increased proportionally with oxygen concentration between 0.4% and 94%. This wide‐range linearity is attributed to the Knudsen diffusion of the oxygen gas passing through the small gap in the spiral Ta2O5 diffusion layer. © 2023 Institute of Electrical Engineer of Japan and Wiley Periodicals LLC.

Synthesis and Characterization of a Zirconium (Zr) Thin Film on Si(100) via Pulsed Laser Deposition

Zirconium (Zr) thin films were deposited on silicon using pulsed laser deposition (PLD) with two laser wavelengths (1064 nm and 532 nm) and varying substrate temperatures (25 °C, 300 °C, and 500 °C) and laser fluences (0.25, 0.5, 1.0 J/cm2). Results indicate that smoother films were obtained with 1064 nm and surface roughness increased with higher fluences. Optimal crystalline films were obtained at 300 °C. XRD, SEM, and AFM analysis revealed distinct patterns and peaks related to laser parameters. The growth mechanisms of a Zr film were computed based on a well-known continuum model of thin film growth. Our simulations agree with experimental observations. The study highlights crucial factors affecting Zr thin film deposition and provides insights for optimizing PLD parameters to achieve high-quality films.

Plasmonic inhibition of bacterial adhesion on gold-decorated mesoporous zirconium oxide thin films

Preventing bacterial development on surfaces is essential to avoid problems caused by biofouling. Surfaces decorated with gold nanoparticles have been shown to thermally kill bacteria under high-intensity NIR illumination. In this study, we evaluated the colonization by E. coli of nanostructured surfaces composed of mesoporous zirconia thin films, both with and without gold nanoparticles embedded into the pores. We studied the effect of the nanostructure and of low intensity visible light excitation of the gold nanoparticles on the colonization process. We found that neither the zirconia, nor the presence of pores, or even gold nanoparticles affect bacterial adhesion compared to the bare glass substrate. Therefore, mesoporous zirconia thin films are biologically inert scaffolds that enable the construction of robust surfaces containing functional nanoparticles that can affect bacterial growth. When the gold containing surfaces are irradiated with light, bacterial adhesion shows a remarkable 96 ± 4% reduction. Our studies revealed that these surfaces affect early colonization steps, prior to biofilm formation, preventing bacterial adhesion without affecting its viability. In contrast to related systems where plasmonic excitation induces membrane damage due to strong local heating, the membrane integrity is preserved, showing that these surfaces have a different working principle.