Y2O3 Films Research Articles

Oxygen plasma-assisted magnetron sputtering deposition of non-stoichiometric Y2O3 films: Influence of oxygen vacancies on etching resistance

Yttrium oxide (Y2O3) films are widely used to protect equipment in plasma etching, a crucial technique in semiconductor processing, due to their exceptional resistance to plasma etching. Since oxygen vacancy affects the performance of Y2O3 and may impact physical etching resistance, the internal relationship necessitates further investigation. In this article, Y2O3 films with varying oxygen vacancy concentrations are prepared by reactive magnetron sputtering with the assistance of oxygen plasma. The formation and development of oxygen vacancies in cubic Y2O3 films and their impact on the physical etching resistance were investigated. The experiment results indicate that the accumulation of oxygen vacancies causes non-stoichiometry and the etching rate is significantly reduced. Combined with density-functional theory, it is revealed that oxygen vacancy distorts the lattice, which increases covalent YO bonding and the formation energy of atoms. Moreover, the vacancy line defects resulting from diffusion and aggregation of oxygen vacancies exert a similar influence on the adjacent yttrium and oxygen layers. The enhancement of physical etching resistance is attributed to the strengthened internal YO bonds led by increasing oxygen vacancy concentration in the cubic Y2O3 films without inducing phase transition. The discovery enriches the understanding of how plasma interacts with Y2O3, and the etching mechanism.

Optimization of Ion Beam-Assisted Deposition Process for Y2O3 Film to Enhance Plasma Resistance

Optimization of Ion Beam-Assisted Deposition Process for Y2O3 Film to Enhance Plasma Resistance

Reliable Operation in High-Mobility Indium Oxide Thin Film Transistors.

Transparent oxide semiconductors (TOSs) based thin-film transistors (TFTs) that exhibit higher field effect mobility (µFE) are highly required toward the realization of next-generation displays. Among numerous types of TOS-TFTs, In2O3-based TFTs are the front-running candidate because they exhibit the highest µFE ≈100cm2V-1s-1. However, the device operation of In2O3 TFTs is unreliable; a large voltage shift occurs especially when negative gate bias is applied due to adsorption/desorption of gas molecules. Although passivation of the TFTs is used to overcome such instability, previously proposed passivation materials do not improve the reliability. Here, it is shown that the In2O3 TFTs passivated with Y2O3 and Er2O3 films are highly reliable and do not show threshold voltage shifts when applying gate bias. Positive and negative gate bias is applied to the In2O3 TFTs passivated with various insulating oxides and found that only the In2O3 TFTs passivated with Y2O3 and Er2O3 films do not exhibit threshold voltage shifts. It is observed that only the Y2O3 grew heteroepitaxially on the In2O3 crystal. This is the origin of the high reliability of the In2O3 TFTs passivated with Y2O3 and Er2O3 films. This finding accelerates the development of next-generation displays using high-mobility In2O3 TFTs.

Effect of O2/Ar ratio on the microstructure and tribological properties of Y2O3 films by multi-arc ion plating

Multi-Arc Ion Plating (MAIP) technology was used to deposit yttrium oxide (Y2O3) ceramic thin films on Al2O3 ceramics and silicon wafers. The effects of varying the O-to-Ar gas flow ratio (Rc: 0.5, 1.0, 1.5, 2.0) and the annealing conditions on the phase composition, microstructure, mechanical properties, and tribological performance of the Y2O3 films were assessed. The films deposited at Rc values of 1.0 and 1.5 consisted of a single cubic phase structure. In contrast, films deposited at Rc values of 0.5 and 2.0 contained a small monoclinic phase and the cubic phase structure. The film deposited at an Rc value of 1.0 (oxygen flow rate of 200 sccm) exhibited a dense microstructure, the best mechanical properties (hardness of 14.2 ± 0.191 GPa), and the lowest friction coefficient (0.142 ± 0.003). Furthermore, the colour of the film changed from grey-black to white after annealing at 800 °C for 6 h. The oxygen vacancy of the thin film increased, with improving crystallinity, decreasing hardness and elastic modulus, and increasing grain size, friction coefficient and wear rate. The film exhibited the best tribological properties at 25 °C.

Substrate controlled hydrophobicity of the Y2O3 films

The development of hydrophobic surfaces is an important factor for clean energy production from solar arrays, enabling their operation at the highest possible efficiencies for the longest possible time, without the need for physical intervention. This work reports the development of hydrophobic Y2O3 thin films on a range of transparent glass substrates. The growth of the Y2O3 films from the mono-hydrate yttrium (III) complex of 1,3-diphenyl-1,3-propanedione [Y(dbm)3(H2O)] is studied using the aerosol-assisted chemical vapor deposition (AACVD) technique. The qualitative evaluation of the deposited films and their hydrophobicity is assessed using several materials characterization techniques, such as scanning electron microscopy, grazing incident X-ray diffraction, Fourier-transform infrared, X-Ray photoelectron spectroscopy, in addition to a surface free energy and water contact angle measurements. This work demonstrates experimentally a relationship between the Y2O3 wettability and its physico-chemical characteristics in terms of surface energy, chemical composition, and morphology which is controlled by the type of glass support used. The water contact angle of the hydrophobic Y2O3 coating grown on the F-doped tin oxide glass reached 128°; currently the first deposited on transparent glass. This film exhibits the highest WCA reported up to date without the need for performing post-reaction surface treatment processes. The hydrophobic nature of the transparent Y2O3 films marks a significant leap forward in the field of anti-soiling coatings suitable for photovoltaic technology.

The use of He buffer gas for moderating the plume kinetic energy during Nd:YAG-PLD growth of EuxY2−xO3 phosphor films

We have investigated the He buffer gas process of moderating the kinetic energy of the pulsed laser deposition (PLD) plume during EuxY2−xO3 phosphor film growth. When using a neodymium yttrium aluminum garnet laser for PLD thin film growth, the kinetic energy of the ablation plumes can be high enough to cause the formation of point defects in the film. The buffer gas pressure is an important process parameter in PLD film growth. We find that the presence of the He buffer gas reduces the kinetic energy of the laser deposition plume through many low-angle collisions in the gas phase by a factor of 7 without reducing the deposition rate. This is because He is much lighter than any of the elements in the plume and it does not affect the composition of the oxide films. Consequently, the resputtering of the Y2O3 film surface by the plume was significantly suppressed in the presence of the He gas moderator, leading to a decrease of the defect density in the Y2O3 films. The improvement of the film quality was verified by a systematic analysis of time-resolved photoluminescence (PL) data for EuxY2−xO3 composition–gradient films. The PL lifetime and intensity of Eu0.2Y1.8O3, which shows the highest PL intensity, increased by 13.3% and 36.4%, respectively, when the He gas moderation process was used. The He buffer gas process is applicable to the PLD growth of the other oxide materials as well, where the reduction of the kinetic energy of the plume would bring the PLD process closer to the molecular beam epitaxy growth condition.

UV/Ozone-Treated and Sol-Gel-Processed Y2O3 Insulators Prepared Using Gelation-Delaying Precursors.

In this study, a Y2O3 insulator was fabricated via the sol-gel process and the effect of precursors and annealing processes on its electrical performance was studied. Yttrium(III) acetate hydrate, yttrium(III) nitrate tetrahydrate, yttrium isopropoxide oxide, and yttrium(III) tris (isopropoxide) were used as precursors, and UV/ozone treatment and high-temperature annealing were performed to obtain Y2O3 films from the precursors. The structure and surface morphologies of the films were characterized via grazing-incidence X-ray diffraction and scanning probe microscopy. Chemical component analysis was performed via X-ray spectroscopy. Electrical insulator characteristics were analyzed based on current density versus electrical field data and frequency-dependent dielectric constants. The Y2O3 films fabricated using the acetate precursor and subjected to the UV/ozone treatment showed a uniform and flat surface morphology with the lowest number of oxygen vacancy defects and unwanted byproducts. The corresponding fabricated capacitors showed the lowest current density (Jg) value of 10-8 A/cm2 at 1 MV/cm and a stable dielectric constant in a frequency range of 20 Hz-100 KHz. At 20 Hz, the dielectric constant was 12.28, which decreased to 10.5 at 105 Hz. The results indicate that high-quality, high-k insulators can be fabricated for flexible electronics using suitable precursors and the suggested low-temperature fabrication methods.

Atomic layer deposition of Y2O3 as high-k dielectrics by using a heteroleptic yttrium precursor and water

Atomic layer deposition (ALD) of Y2O3 thin films was performed on Si substrate by pulsing an unconventional heteroleptic yttrium precursor Y(MeCp)2(Me2Pz) and H2O alternatively. The thin film grew 0.26–0.28 Å per cycle at relatively low temperature of 195–225 °C in a self-limiting manner with negligible nucleation delay, and is close to stoichiometric (O/Y = 1.48, C, 2.56 at%; N, 1.81 at%) in as-deposited form. Integration of the post-annealed ALD Y2O3 film in a metal oxide semiconductor (MOS) capacitor structure exhibits representative electrical properties including a high dielectric constant k of 11.4, high electrical breakdown field of 6.1 MV cm−1 and low leakage current density of 9.1 × 10−8 A cm−2 at − 2 MV cm−1.

A strain density function to analyze particle size effects during high velocity impacts of yttria

AbstractThe impact behavior of a single yttria (Y2O3) nanoparticle onto a Y2O3 substrate is studied as a function of particle velocity (300–1200 m/s) and diameter (12–50 nm) using molecular dynamics simulations. To analyze the results, a strain density function is developed to provide both quantitative and qualitative information about the deformation mechanisms that contribute to the final state of the system. This function provides both clear evidence of shear localization and insight into the conditions for which localization occurs during the impact of Y2O3 particles as they approach experimentally relevant sizes. Further analysis shows that localization and fragmentation only occur for Y2O3 impacts with diameters of at least 50 nm, while particles with diameters of 25 nm and smaller deform primarily by amorphization and viscous flow. Implications for the deposition of films of Y2O3 and other rare‐earth oxides via the micro cold spray process are discussed.

Formation of yttrium oxalate phase filled by carbon clusters on the surface of yttrium oxide films

In the current paper, we report the results of surface modification of cubic Y2O3 films employing carbon-ion implantation. The characterization results demonstrate the formation of a stable yttrium oxalate-based structure with cavities filled with carbon clusters. Theoretical simulations demonstrate that the incorporation of eighteen-atom carbon clusters into the cavities of Y2(C2O4)3 does not lead to valuable changes in the crystal structure of yttrium oxalate. X-ray diffraction and optical measurements demonstrate that the subsurface bulk area of cubic yttrium oxide remains unperturbed. The oxalate “skin” thickness with embedded carbon clusters is estimated to be approximately 10 nm. The prospective employing the method to manage optical properties and increase the biocompatibility of yttria and lanthanide oxides are discussed.

High temperature optical performance of MgO:Y2O3 films for space applications

As a species we are pushing the bounds of possibility as we seek to venture beyond our solar system. With the pursuit of interstellar space comes a need for spacecraft that can reach unprecedented speeds. For this purpose, a passive gravity assist around a planet such as Jupiter has become commonplace by NASA. However, it is limited by the orbital velocity of that planet. In order to reach greater speeds, it is desirable to perform a powered gravity assist around the Sun, in which a spacecraft falls into its gravitational well and performs an impulsive burn at the perihelion. To achieve this feat, spacecraft must pass closer to the Sun than ever before withstanding temperatures exceeding 2000 K. This will require thermal barrier coatings that are both highly emissive in the infrared and highly reflective in the visible. Since development costs associated with fabricating and testing these materials at elevated temperatures can be prohibitive, models describing the high temperature optical properties of candidate coating materials can play an important role in the overall design process. This paper discusses the use of Kubelka Munk theory to model the reflectance spectra over a range of temperatures for a MgO:Y2O3 film on a tungsten substrate and demonstrates an approach for determining the efficacy of various thermal barrier coatings for passive cooling under solar loading.

Edge cracking behavior of Y2O3 films based on the stress intensity factor

Hastelloy C-276 alloy is the preferred substrate for YBa2Cu3O7-δ (YBCO) coated conductors prepared by Ion-beam-assisted deposition (IBAD) route, but its surface is too rough to meet application requirements. Y(CH3COO)3·4H2O precursor solution has a low flattening efficiency, and its film edges are prone to crack formations. In this paper, a model for the stress intensity factor was established to study the effect of the presence of cracks on film stress. The simulation results showed that increasing the coating thickness reduced the overall stress, but increased the stress concentration at the crack. The larger bottom layer defects also made it easier for cracks to be generated. Then, 10-m long Hastelloy C-276/Y2O3 strips were prepared by colloidal-solution deposition planarization (CSDP), with an average surface roughness Rq of 0.427 and only 10 coating layers. This improved the flattening efficiency by 40 %, and a CeO2 layer with a good biaxial texture was finally prepared.

Atomic Diffusion Bonding in Air Using Oxide Films

Atomic diffusion bonding (ADB) of wafers is a promising process to achieve room-temperature wafer bonding [1]. For ADB processing, thin films are fabricated on two flat wafer surfaces using sputter deposition, with subsequent bonding of the two films on the wafers in vacuum. In addition to thin metal films [1], both oxide [2] and nitride [3] thin films are useful for bonding.For this study, after demonstrating ADB “in air” using oxide films, we compared the resultant bonding performance to that obtained using ADB “in vacuum” with the oxide films. Table 1 presents the surface free energy values at the bonded interface γ for quartz glass wafers bonded using 5-nm-thick Y2O3 film on each side. Using ADB in vacuum, great bonding strength was achieved for as-bonded wafers: the blade could not be inserted between the wafers. Using ADB in air, γ for as-bonded wafers was small, only 0.25 J/m2, but low-temperature annealing at 150 °C enhanced γ to 1.6 J/m2. At 200 °C, γ becomes greater than 2 J/m2. The annealing was conducted in air using a hot plate. Figure 2 portrays STEM cross-section images of Y2O3(5 nm)/Y2O3(5 nm) films (A) bonded in vacuum (as-bonded) and (B) bonded in air (annealed at 150 °C). The bonded interface is not visible in image (A). However, a slightly low-density bonded interface is partially visible in image (B). The difference of the bonded interface structure is consistent with that of γ presented in Table 1.Various oxide films such as TiO2, ITO, SiO2, and WO3 are useful for ADB in air, as is true also for ADB in vacuum, although post-bonded annealing at a low temperature of 150 °C is necessary for ADB in air to achieve γ greater than 1 J/m2. The bonding process of ADB in air is more convenient to execute than that in vacuum. Moreover, any mirror-polished wafer can be bonded using ADB in air, as is true also using ADB in vacuum. It is likely that H2O gas in air can adsorb on the fresh surface of oxide films efficiently and that well-hydrophilic films surfaces can be obtained easily when the deposited oxide films are removed from the vacuum chambers; in fact, low-temperature annealing at 150 °C enhanced γ remarkably. ADB in air using oxide films is useful for some applications if post-bonded annealing at low temperatures is acceptable for bonding processes. T. Shimatsu and M. Uomoto, ECS Trans., 33 (4), 61 (2010).T. Shimatsu, H. Yoshida, M. Uomoto, T. Saito, T. Moriwaki, N. Kato, Y. Miyamoto, and K. Miyamoto, Proceedings of Seventh LTB-3D 2021. p.51 (2021).M. Uomoto, H. Yoshida, T. Shimatsu, T. Saito, T. Moriwaki, N. Kato, Y. Miyamoto, and K. Miyamoto, Proceedings of Seventh LTB-3D 2021. p.45 (2021). Figure 1

Preparation of MgO Self-Epitaxial Films for YBCO High-Temperature Coated Conductors.

Ion beam-assisted deposition (IBAD) has been proposed as a promising texturing technology that uses the film epitaxy method to obtain biaxial texture on a non-textured metal or compound substrate. Magnesium oxide (MgO) is the most well explored texturing material. In order to obtain the optimal biaxial texture, the actual thickness of the IBAD-MgO film must be controlled within 12nm. Due to the bombardment of ion beams, IBAD-MgO has large lattice deformation, poor texture, and many defects in the films. In this work, the solution deposition planarization (SDP) method was used to deposit oxide amorphous Y2O3 films on the surface of Hastelloy C276 tapes instead of the electrochemical polishing, sputtering-Al2O3 and sputtering-Y2O3 in the commercialized buffer layer. An additional homogeneous epitaxy MgO (epi-MgO) layer, which was used to improve the biaxial texture in the IBAD-MgO layer, was deposited on the IBAD-MgO layer by electron-beam evaporation. The effects of growth temperature, film thickness, deposition rate, and oxygen pressure on the texture and morphology of the epi-MgO film were systematically studied. The best full width at half maximum (FWHM) values were 2.2° for the out-of-plane texture and 4.8° for the in-plane texture for epi-MgO films, respectively. Subsequently, the LaMnO3 cap layer and YBa2Cu3O7-x (YBCO) functional layer were deposited on the epi-MgO layer to test the quality of the MgO layer. Finally, the critical current density of the YBCO films was 6 MA/cm2 (77 K, 500 nm, self-field), indicating that this research provides a high-quality MgO substrate for the YBCO layer.

Mg dopant induced ultra-high HRS resistance and striking switching window characteristics in amorphous Y2O3 film-based memristors

Y2O3 has attracted attention as the representative emerging candidate of a resistive switching (RS) medium in memristors due to its excellent electrical properties and good thermal stability. However, many challenges for Y2O3 film-based memristors remain to be resolved, particularly for the small switching window. Here, the doping engineering strategy is proposed, and in particular, the Mg doped amorphous Y2O3 film is adopted as the RS layer to construct memristors. The prepared Pt/Mg:Y2O3/Pt memristor exhibits a typical reproducible bipolar switching behavior with ultra-high HRS resistance and excellent switching window (>105), compared with the undoped counterparts (∼50). In addition, the multilevel storage capability is also achieved by controlling compliance current. Furthermore, the mechanisms and corresponding physical models for the striking RS characteristics for Pt/Mg:Y2O3/Pt memristors, stemming from the Mg dopant, are discussed and illustrated in detail. This work affords a deep understanding of RS mechanisms for Mg-doped Y2O3 film-based memristors and provides an effective strategy to enlarge the switching window for other transition metal oxide memristors.

Diverse Coordination Chemistry of the Whole Series Rare-Earth L-Lactates: Synthetic Features, Crystal Structure, and Application in Chemical Solution Deposition of Ln2O3 Thin Films.

Rare-earth (RE, Ln) carboxylates are widely studied as precursors of RE oxide-based nanomaterials; however, no systematic studies of RE L-lactates (HLact = 2-hydroxypropanoic acid) have been reported to date. In the present work, a profound structural investigation of RE L-lactates is carried out. A family of RE lactate complexes of the general formula LnLact3∙nH2O (Ln = La, Ce-Nd, Sm-Lu, Y; n = 2-3) are synthesized and characterized by CHN, TGA, and FTIR as well as by powder and single-crystal XRD methods.The existence of four novel structural types (1-Ln-4-Ln) is revealed. Compounds of the 1-Ln type (Ln = La, Ce, Pr) exhibit a chain polymeric structure, whereas 2-Ln-4-Ln compounds are molecular crystals consisting of dimeric (2-Ln; Ln = La, Ce-Nd) or monomeric (3-Ln-Ln = Sm-Lu, Y; 4-Ln-Ln = Sm-Gd, Y) species. The crystal structures of 1-Ln-4-Ln compounds are discussed in terms of their coordination geometry and supramolecular arrangement. Solutions of yttrium and lanthanum lactates with diethylenetriamine are applied for the chemical deposition of Y2O3 and La2O3 thin films.

Fluorination behavior of Y2O3-MgO nanocomposite films irradiated by CF4/O2 plasma

In this study, the Y2O3-MgO (YM) nanocomposite film was prepared using radio frequency magnetron sputtering. The microstructures, chemical compositions, and fluorination behavior of YM films were systematically investigated and compared to those of Y2O3 and MgO films. After exposure to CF4/O2 etching plasma, the surface morphology of the YM nanocomposite film exhibited uniform etching behavior and preserved its original smooth surface. Energy dispersive X-ray spectroscopy mapping and transmission electron microscopy revealed that fluorine atoms present near surface region of the YM nanocomposite film and formed a thin homogeneous fluorinated layer having an average thickness of approximately 20 nm. Furthermore, the fluorinated layer of the YM nanocomposite film did not expand with prolonged plasma exposure. These results demonstrate that the chemical stability of the fine-grained YM nanocomposite film against damage due to the suppression of surface fluorination during CF4/O2 plasma etching.

Structural Defect Effect on the Concentration Quenching of TbxY2–xO3 Phosphor Thin Films

This study investigates the structural defect effect on the luminescence properties of TbxY2–xO3 (x = 0–0.5) composition-gradient films using combinatorial pulsed laser deposition (PLD). TbxY2–xO3 films were grown on a SrTiO3 (001) substrate in an O2/He mixed atmosphere at PO2 = 1 × 10–4 Torr. A He buffer gas moderated the kinetic energy of the PLD plume and suppressed the resputtering of the film surface, resulting in the fabrication of defect-rich and poor TbxY2–xO3 films. The TbxY2–xO3 composition-gradient films exhibited varying green emissions from the Tb-doped Y2O3 films. The luminescence intensity of the defect-rich film was significantly weaker than that of the defect-poor film. Furthermore, concentration quenching of the luminescence occurred at high Tb concentrations. The analysis of the decay profiles of the luminescence as a function of the Tb concentration suggested two possible reasons for luminescence quenching: dynamic quenching induced by structural defects and static quenching induced by the shorter average distance of adjacent Tb ions. The investigation of the structural defect effect on the luminescence properties provides insights into the primary material parameters of phosphor materials and offers a pathway for enhancing their luminescence properties.

Microstructural characterization, mechanical properties and erosion behavior of Y2O3–MgO nanocomposite films by magnetron sputtering

The effect of Y2O3: MgO ratio on the microstructures, mechanical properties, and plasma erosion behaviors of Y2O3–MgO (YM) nanocomposite films were investigated. The columnar growth structure of the YM nanocomposite film is disrupted as the MgO content increases, resulting in the refinement of the Y2O3 grains. When the Y2O3: MgO ratio is 40 : 60, the columnar crystal structure of the YM nanocomposite film can be refinement effectively due to thermodynamic incompatibility of Y2O3 and MgO. As a result, YM nanocomposite film is strengthened significantly with the maximum hardness and elastic modulus of 16.78 ± 0.8 GPa and 149.24 ± 4.7 GPa, respectively. X-ray photoelectron spectroscopy revealed few changes in the elemental and chemical compositions of the surface layer after fluorination in the YM nanocomposite film, confirming the chemical stability of the YM nanocomposite samples. The etching depth is ∼48% lower on the YM nanocomposite film (with a MgO content of 60%) than on the commercial Y2O3 film. The findings show that the strengthened YM nanocomposite film is more erosion resistant than the commercial Y2O3 coating.

Thickness dependence of resistive switching characteristics of the sol–gel processed Y2O3 RRAM devices

In this study, yttrium oxide (Y2O3)-based resistive random-access memory (RRAM) devices were fabricated using the sol–gel method. The fabricated Y2O3 RRAM devices exhibited conventional bipolar RRAM device characteristics and did not require a forming process. The Y2O3 film thickness was controlled by varying the liquid-phase precursor concentration. As the concentration increased, thicker Y2O3 films were formed. In addition, the concentration of oxygen vacancies increased. The RRAM device properties were not observed for thin Y2O3 films, which had the lowest oxygen vacancy concentration. Moreover, RRAM devices, which consisted of the thickest Y2O3 films with the largest oxygen vacancy concentration, showed poor non-volatile properties. The optimized Y2O3-based RRAM devices with a thickness of 37 nm showed conventional bipolar RRAM device characteristics, which did not require an initial forming process. The fabricated RRAM devices showed a high resistance state to low resistance state ratio of over 104, less than +1.5 V of SET voltage, and −15.0 V of RESET voltage. The RRAM devices also showed promising non-volatile memory properties, without significant degradation after 103 s retention and 102 cycle endurance tests.