Y2O3 Thin Films Research Articles

Rare Earth‐Diamond Hybrid Structures for Optical Quantum Technologies

AbstractDiamond containing nitrogen‐vacancy centers (NV−) is one of the most investigated materials for quantum technologies, because of this system's exceptional spin properties. Although the NV− optical transition is very bright, it suffers from spectral diffusion and weak zero‐phonon line, and is in the visible range. This limits integration into quantum photonic structures and interfacing with optical fiber networks. In contrast, rare earth (RE) ions exhibit extremely narrow and stable optical transitions, including erbium's 1.5 µm telecom wavelength. Combining RE with NV− properties through short‐range interactions is however challenging as RE do not readily enter the diamond lattice. In this work, a thin‐film‐based architecture in which RE and NV− centers can interact while preserving their unique properties is introduced. Thin films of Er3+:Y2O3 are grown by chemical vapor deposition on diamond substrates with well‐crystallized and highly textured structures. An extensive spectroscopic study of Er3+ transitions at room and low temperatures further reveals that photoluminescence spectra and decays are close to bulk materials. It is also shown that Y2O3 thin film deposition has no detrimental effects on NV− optical and spin properties. RE thin films deposited on diamond can thus be suitable for building hybrid materials for new functionalities in quantum sensing, communication, and processing.

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.

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.

Luminescence enhancement of Y2O3 thin films based on LSPR effect of Ag nanolayers

Based on the local surface plasmon resonance effect of Ag nanolayer, the luminescence enhancement in the visible light range of multilayer thin film has been investigated combined with metal/spacer molecule/photoluminescence material structure. The luminescence enhancement effect of multilayer thin films can be improved by adjusting the spin-coating number of Ag nanolayer and SiO2 spacer in the multilayer structure. At the same time, the mechanism of enhanced luminescence has been analyzed according to the change in fluorescence lifetime. The effect of the coupling between Ag nanolayer and luminescence layer on the radiative transition rate and fluorescence quantum yield have been discussed. The up-conversion luminescence intensity of the noble metal-modified multilayer thin film can be further improved by combining the multilayer structure with sensitized layer.

Chemical characteristics via quantitative photoelectron analysis of chemical-solution-deposited yttrium oxide thin films for metal-insulator-metal capacitor applications

A cost-effective chemical bath deposition coupled with an annealing methodology is presented for obtaining yttrium oxide (Y2O3) thin films. The resultant thin films are homogeneous, free of pinholes, and show a relatively low surface roughness. The detailed characterization of the as-deposited thin film and the determination of optical, structural, and chemical characteristics of the films upon thermal transformation at 500 °C for 2 h was done with thermogravimetric analysis, X-ray diffraction, UV–Vis spectroscopy, surface topology analysis, and X-ray photoelectron spectroscopy. The results reveal that the as-deposited thin film is composed of an amorphous YOOH compound intrinsic to the synthesis process. However, with annealing, it is crystallized and transformed into a Y2O3 thin film showing a high optical transparency. The characteristics of the film are found to be influenced by the Y‒OH and Y‒O content with direct influence on the shape of the photoelectron spectra of the thin films showing a binding energy downshift of 1.6 eV from the 158.84 eV peak position found for the YOOH sample after annealing. The estimated surface roughness for the as-deposited YOOH and annealed Y2O3 samples resulted in 2.7 and 3.8 nm, respectively. The electrical characteristics and potential performance as a dielectric layer have been assessed in a Metal-Insulator-Metal configuration, where the acceptable values for leakage current in the 6 × 10−4 − 3 × 10−6 A/cm2 range and a capacitance of 218 and 80 nF/cm2 were measured for the YOOH and Y2O3 thin films, respectively. The latter indicates that these films are suitable candidates for gate dielectric transistor applications with the advantage of them being films produced via an economical and technically simple scalable process.

Photoluminescence of combinatorically sputtered Al2O3–Y2O3 thin films with a Cr3+ and Nd3+ co-doping concentration gradient

The characterization of a wide range of luminescent thin films can be a long and tedious endeavor. With reactive combinatorial sputtering of multiple metal targets, it possible to fabricate thin films with a gradient in composition simply by not rotating the substrate. In this work, combinatorically sputtered thin films of Cr3+ and Nd3+ doped in the Al2O3–Y2O3 system (YAlO) are studied for thin film based luminescent solar concentrators (TFLSCs) application. Contrary to mm's thick plate type LSC's, TFLSCs of just several 100 nm thick require much higher Cr3+ concentration to achieve 40% absorption which can enable several 10's of W/m2 LSC power efficiencies. Our transmission measurements on a Cr2O3 film with a thickness gradient result in an absorption cross section at 460 nm of 1.3 ± 0.7 × 10−19 cm2 showing that the TFLSC absorption requirement can be fulfilled provided that the Cr3+ concentration is in the order of 1022 ions/cm3. The Y:Al ratio of the YAlO host in our films ranged between 0.5 and 3.5, thereby including the monoclinic (Y4Al2O9), perovskite (YAlO3) and garnet (Y3Al5O12) stoichiometry's on a single film. Position dependent XRD, EDX, excitation, emission and lifetime measurements of Cr3+ and Nd3+ show that the unique gradient film sputtering method is able to characterize thin films as a function of host composition and doping concentration. Energy transfer between Cr3+ and Nd3+ in co-doped YAlO films is concluded from Cr3+ excitation bands observed while monitoring Nd3+ emission and from the matching of the rise-time of Nd3+ 1340 nm emission (4F3/2 ->4I11/2) and the decay time of Cr3+ 840 nm emission (4T2 ->4A2). Nd3+ lifetime systematically decreases from 0.24 to 0.05 ms with increasing Cr3+ concentration in Y3Al5-xCrxO12:Nd (0.05 < x < 2). The constraints of heavily doped Cr3+ thin films for enabling adequate absorption and energy transfer to Nd3+ in TFLSC applications are the subjects of the discussion.

Effects of HfO2 addition on the plasma resistance of Y2O3 thin films deposited by e-beam PVD

Ceramic Y2O3 thin films are often used to coat the inner walls of etching equipment during semiconductor manufacturing to protect them from bombardment by high-energy plasma ions, which can degrade the equipment and cause semiconductor contamination. In this study, the effects of HfO2 addition to the Y2O3 thin film on the plasma resistance were investigated. Thin films were fabricated using electron beam-physical vapor deposition. The addition of HfO2 maintained the cubic Y2O3 crystalline structure while substantially improving the etch resistance during fluorine-based plasma etching. X-ray photoelectron spectroscopy analysis of the etched surface showed that HfO2 addition resulted in a lower F/(O + F) ratio, thus promoting the formation of more Y–O bonds that are more resistant to physical sputtering. Additionally, the analysis indicated that Hf4+ was more likely to be removed from the etched surface than Hfx+ (x < 4). This novel strategy is expected to aid in the development of improved plasma-resistant ceramic materials.

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.

Carbon nanotube network film-based field-effect transistor interface state optimization by ambient air annealing

Carbon nanotube field-effect transistors (CNTFETs) have been considered a strong candidate for post-Si era electronics due to the virtues of higher speed, lower power consumption, and multiple functionalities. The interface analysis based on the top gate structure has made little progress and lacks a reliable charge trap characterization model suitable for carbon tube devices. Quantitative extraction and analysis of the interface state are crucial for the integration of top-gate devices. Herein, a 5 nm thick Y2O3 thin film was selected as the gate dielectric layer in the top-gate CNTFETs device, and a post-annealing process in air ambience was utilized to optimize the Y2O3-CNT interface. A series of device performance evaluation results indicated that the post-annealing process in air ambience can effectively improve the on-state current and reduce the threshold voltage and subthreshold swing of the device, which are derived from diffusion of oxygen atom in the Y2O3 layer and optimization of the interface of Y2O3-CNT. Specifically, the maximum mobility, subthreshold swing, and threshold voltage are calculated to be 29 cm2/V s, 103 mV/dec, and −0.1 V, respectively, and the interface state density is reduced from 2.68 × 1012 to 1.51 × 1012 cm−2 in the gate insulator. These results not only are important to understand the dielectric impact on CNTFET devices but also are useful for future materials’ development and device optimization for high-performance CNT-based electronics.

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.

Atomic layer deposition of Y2O3 films using a novel liquid homoleptic yttrium precursor tris(sec-butylcyclopentadienyl)yttrium [Y(sBuCp)3] and water.

Atomic layer deposition (ALD) of Y2O3 thin films was studied using a novel homoleptic yttrium ALD precursor: tris(sec-butylcyclopentadienyl)yttrium [Y(sBuCp)3]. Y(sBuCp)3 is a liquid at room temperature. The thermogravimetry curve for Y(sBuCp)3 is clean, with no indication of decomposition or residue formation. Thermogravimetry-differential thermal analysis measurements showed that Y(sBuCp)3 is stable for 18 weeks at 190 °C. Y(sBuCp)3 has a homoleptic structure. Thus, a reduction in manufacturing costs is expected compared to those associated with heteroleptic precursors because additional chemical synthesis steps are usually necessary to produce heteroleptic compounds. In addition, ALD of Y2O3 was demonstrated using Y(sBuCp)3 and water as a co-reactant. The deposition temperature was varied from 200 to 350 °C. The growth rate was 1.7 Å per cycle. In addition, neither carbon nor nitrogen contamination was detected in the Y2O3 films by X-ray photoelectron spectroscopy. Furthermore, smooth films were confirmed by X-ray secondary-electron microscopy. The root-mean-square roughness was measured to be 0.660 nm by atomic force microscopy. Metal-insulator-semiconductor (MIS) Pt/Y2O3/p-Si devices were fabricated to evaluate the electrical properties of the Y2O3 films. An electric breakdown field of -6.5 MV cm-1 and a leakage current density of ∼3.2 × 10-3 A cm-2 at 1 MV cm-1 were determined. The permittivity of Y2O3 was estimated to be 11.5 at 100 kHz. Therefore, compared with conventional solid precursors, Y(sBuCp)3 is suitable for use in ALD manufacturing processes.

Pr3+-doped Y2O3 nanocrystals embedded in Y2O3 thin films as a sandwich-like structure prepared by pulsed laser deposition

Pr3+-doped yttria (Y2O3) nanocrystal layers embedded in between pure yttria thin films were prepared on four different substrates. Pulsed laser deposition was used to fabricate this sandwich-like structure. An exhaustive structural and optical characterization of the initial nanocrystals was performed to study their preservation once incorporated between the deposited thin films. We demonstrate that the prepared Y2O3:Pr3+ nanocrystals can be integrated into the thin films after the pulsed laser deposition process, retaining their original crystal structure and luminescent features regardless of the number of deposition cycles and the nature of the substrate. In this sense, we present a novel method to embed and protect the luminescent material, paving the way for developing future optoelectronic applications.

Effects of the Deposition Mode and Heat Treatment on the Microstructure and Wettability of Y2O3 Coatings Prepared by Reactive Magnetron Sputtering

A robust hydrophobic Y2O3 coating at high temperatures is important for industrial applications. In this study, Y2O3 thin films on Si substrates were prepared by reactive direct current magnetron sputtering. By changing the deposition power, Y2O3 thin films with different microstructures were obtained in poison mode and metallic mode, respectively. In order to understand the effect of heat treatment on the microstructure and hydrophobicity of Y2O3, the samples were annealed at 400 °C in the air. Compared to metallic mode, no crack was formed on the surface of the Y2O3 film prepared in poison mode. In addition, the water contact angle on the surface of the Y2O3 thin film deposited in poison mode was above 90° before and after annealing at 400 °C. It has been demonstrated that the initial high concentration of physically absorbed oxygen and its slow desorption process in a Y2O3 thin film prepared in poison mode contributes to the hydrophobicity of the thin film at high temperatures. These results can provide insights into the large-scale fabrication of hydrophobic Y2O3 coatings for high-temperature applications.

Density of states and interband light absorption in Y2O3 and Sc2O3 thin films

The long-wavelength edge of the fundamental absorption band of thin Y2O3 and Sc2O3 films obtained by the method of discrete evaporation in vacuum is investigated. On the basis of its temperature dependence, the excitons - phonon interaction is investigated, which made it possible to interpret the absorption edge as the absorption of self-trapped excitons. To analyze the experimental results, we used a model of a heavily doped or defective semiconductor in the quasi-classical approximation. The use of this model made it possible to estimate the radius of the ground electronic state a and the screening radius rS and the concentration of free charge carriers N in the films under study.&#x0D;

Effects of substrate temperature on the structure and luminescence of transparent red-emitting Eu-doped Y2O3 thin films

Effects of substrate temperature on the structure and luminescence of transparent red-emitting Eu-doped Y2O3 thin films

Influence of the Composition of the Radio-Frequency Sputtering Atmosphere on the Density of States and Interband Light Absorption in thin Y2O3 Films

Influence of the Composition of the Radio-Frequency Sputtering Atmosphere on the Density of States and Interband Light Absorption in thin Y2O3 Films

INFLUENCE OF THE COMPOSITION OF THE RADIO-FREQUENCY SPUTTERING ATMOSPHERE ON THE DENSITY OF STATES AND INTERBAND LIGHT ABSORPTION IN THIN Y2O3 FILMS

The long-wavelength edge of the fundamental absorption band of thin Y2O3 films obtained by radiofrequency ion-plasma sputtering is investigated. The edge of interband absorption after annealing of the films in an atmosphere of argon, oxygen, or a mixture of these gases is shown to be approximated well by the&#x0D; Urbach empirical rule. Diffractograms of the obtained films were studied and a model of a heavily doped or defective semiconductor in the quasi-classical approximation was used to analyze the experimental results. This model allows determining the radius of the basic electronic state, the screening radius, and the rootmean-square potential depending on the sputtering atmosphere.

Influence of Ar-impurities on the wettability of IBS-deposited Y2O3 thin films

The wettability and the control of the contact angle of surfaces are important for various applications. Materials with a water contact angle less than or greater than 90 deg are hydrophilic or hydrophobic, respectively. Most of the binary oxides are hydrophilic, but oxides of rare earth metals and metal atoms with low electronegativity have hydrophobic surfaces. Yttria is one of the materials predicted to have hydrophobic properties. In this work, we investigated the wettability of ion-beam-sputtered Yttria thin films. The measured water contact angles were between 67° and 96°. The concentration of the embedded argon atoms was found to influence the contact angle.

Optical and Mechanical Properties of ZnS/Ge0.1C0.9 Antireflection Coating on Ge Substrate

In this work, we designed, fabricated, and characterized a ZnS single-layer antireflection coating on Ge substrate, suitable for infrared range. To improve the coatings hardness, Ge0.1C0.9 film was deposited on the prepared coating. Y2O3 thin film was applied as adhesive layer between the ZnS film/Ge substrate and the Ge1-xCx film/ZnS film. The morphology and surface roughness of the samples were studied by FE-SEM and AFM analyses. The optical and mechanical properties of the resultant multilayer sample were investigated. The results showed that Ge0.1C0.9 coating does not change the refractive index of the antireflection coating. The indentation test showed that the hardness is improved from 5.9 to 7.8 GPa. After coating Ge0.1C0.9 layer, the sample successfully passed the environmental and durability tests.

Electrical Properties of Amorphous Indium Zinc Tin Oxide Thin Film Transistor with Y₂O₃ Gate Dielectric.

High-k Y₂O₃ thin films were investigated as the gate dielectric for amorphous indium zinc tin oxide (IZTO) thin-film transistors (TFTs). Y₂O₃ gate dielectric was deposited by radio frequency magnetron sputtering (RF-MS) under various working pressures and annealing conditions. Amorphous IZTO TFTs with SiO₂ as the gate dielectric showed a high field-effect mobility (μFE) of 19.6 cm²/Vs, threshold voltage (Vth) of 0.75 V, on/off current ratio (Ion/Ioff) of 2.0×106, and subthreshold swing (SS) value of 1.01 V/dec. The IZTO TFT sample device fabricated with the Y₂O₃ gate dielectric showed an improved subthreshold swing value compared to that of the IZTO TFT device with SiO₂ gate dielectric. The IZTO TFT device using the Y₂O₃ gate dielectric deposited at a working pressure of 5 mtorr and annealed at 400 °C in 6 sccm O₂ for 1 hour showed a high μFE of 51.8 cm²/Vs, Vth of -0.26 V, Ion/Ioff of 6.0×10³, and SS value of 0.19 V/dec. With the application of a Y₂O₃ gate dielectric, the Vth shift improved under a positive bias stress (PBS) but was relatively unaffected by negative bias stress (NBS). These shifts were attributed to charge traps within the gate dielectric and/or interfaces between the channel and gate dielectric layer.