Er2O3 Films Research Articles

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.

Relationship between oxidation, stresses, morphology, local resistivity, and optical properties of TiO2, Gd2O3, Er2O3, SiO2 thin films on SiC

The relationship between internal mechanical stresses, surface morphology, nanoscale electrical properties, and optical characteristics in TiO2, Gd2O3, Er2O3, and SiO2 thin films on SiC substrates was investigated. The oxide films were synthesized using the rapid thermal annealing and analyzed through scanning spreading resistance microscopy, photoluminescence, and absorption spectroscopy. Tensile stresses were found in the films, they are attributed to thermal and lattice mismatch, oxidation, and grain boundaries. These stresses influence on surface morphology, resistivity variations, and photoluminescence intensity. Surface roughness and grain structure were found to correlate with variations in resistivity, which were attributed to conductive pathways along grain boundaries and possible metallic phases. Photoluminescence intensity was also observed to correlate with estimated lattice mismatch strain. Gd2O3/SiC exhibited the fewest defects, while Er2O3 and TiO2 showed more, with Er2O3 being the most mismatched and roughest. The results indicate that internal strains in oxide thin films on SiC substrates can influence on surface morphology, leading to formation of defects and spatial inhomogeneity. These fluctuations in local conductivity and luminescence center density have significant implications for dielectric and optical applications. The study provides insights for future processing refinements to mitigate internal strains and enhance the performance of oxide thin films in semiconductor and optical technologies.

Effect of oxygen/argon ratio on microstructure, compositon and optical properties of erbium oxide anti-reflection films on CVD diamond

Optical erbium oxide (Er2O3) films were prepared by radio frequency (RF) magnetron sputtering to improve the infrared (IR) transmittance of chemical vapor deposition (CVD) diamond. This study aims to analyze the microstructure, composition and optical properties of Er2O3 anti-reflection films at various oxygen/argon ratios. Atomic force microscopy (AFM) analysis was used to detect the surface morphology of chemical oxidation CVD diamond and Er2O3 films. The surface roughness of Er2O3 films decreased with an increase in the oxygen/argon ratio. The crystalline structure of Er2O3 films was analyzed by using X-ray diffraction. Meanwhile, a gradual decrease was observed when the crystallite size and its strain were calculated. This was due to the transformation of partial phases from monoclinic to cubic structures. The chemical composition of Er2O3 films was analyzed by X-ray photoelectron spectroscopy (XPS). The surface of Er2O3 films underwent a transformation from the unstable structure of nonstoichiometric Er2O3-x to the stable structure of Er2O3 with an increase in the level of oxygen. Defect behavior was determined by transmission electron microscopy (TEM). Specifically, dislocation and twinning were observed at a high oxygen/argon ratio, which was mainly attributed to the competitive growth of polycrystalline Er2O3 films. The optical constants of Ψ and △ were shifted to lower wavelengths with increase oxygen/argon ratio. The maximum transmittance of the Er2O3/diamond film was 79% in the long-wavelength infrared (LWTR) range of 8–12 μm at an oxygen/argon ratio of 1:35. This value was significantly higher than that of the high oxygen/argon ratio. The present study concludes that a low oxygen/argon ratio promotes the growth and IR transmittance of Er2O3 films.

Effects of processing parameters on the morphologies of complex sesquioxide thin films

Controlling and predicting the morphology of lanthanide sesquioxides in thin film form is vital to their use in current applications. In the present study, single and codeposited Sm2O3, Er2O3, and Lu2O3 thin films were grown on yttria-stabilized zirconia (8%) substrates by radio frequency magnetron sputtering at room temperature and 500 °C. The effect of two different substrate temperatures and altering the oxide cation on the structural and morphological properties of the films was analyzed. The thin films were characterized by profilometry, scanning electron microscopy, transmission electron microscopy, and x-ray diffraction. The single-component Lu2O3 and Sm2O3 films obtained were of the cubic phase, and the Er2O3 was a mix of cubic and monoclinic phases. It was observed for both the Er2O3 and Lu2O3 films that increasing the substrate temperature to 500 °C resulted in larger grained polycrystalline films. In contrast, large grained polycrystalline films were obtained at both room temperature and 500 °C for Sm2O3 and uneven granularity increased as temperature increased. Codeposition of Lu2O3 and Sm2O3, and Lu2O3 and Er2O3 resulted in a cubic bixbyite phase (the C phase of the lanthanide sesquioxide) solid solution. It was observed that the structure and morphology of the films can be controlled by manipulating deposition parameters. Both substrate temperature and altering the oxide cation contributed to changes in crystallinity and grain structure, which can modify the chemical and physical properties of the films for their applications.

Thermal atomic layer deposition of Er2O3 films from a volatile, thermally stable enaminolate precursor.

Thin films of Er2O3 films were grown by atomic layer deposition using the Er precursor tris(1-(dimethylamino)-3,3-dimethylbut-1-en-2-olate)erbium(III) (Er(L1)3), with water as the co-reactant. Saturative, self-limited growth was observed at a substrate temperature of 200 °C for pulse lengths of ≥4.0 s for Er(L1)3 and ≥0.2 s for water. An ALD window was observed from 175 to 225 °C with a growth rate of about 0.25 Å per cycle. Er2O3 films grown at 200 °C on Si(100) and SiO2 substrates with a thickness of 33 nm had root mean square surface roughnesses of 1.75 and 0.75 nm, respectively. Grazing incidence X-ray diffraction patterns showed that the films were composed of polycrystalline Er2O3 at all deposition temperatures on Si(100) and SiO2 substrates. X-ray photoelectron spectroscopy revealed stoichiometric Er2O3, with carbon and nitrogen levels below the detection limits after argon ion sputtering to remove surface impurities. Transmission electron microscopy studies of Er2O3 film growth in nanoscale trenches (aspect ratio = 10) demonstrated conformal coverage.

Effects of Helium on the creep resistance of Er2O3 films

The nanostructured Er2O3 thin films implanted by Helium (He) were prepared by magnetron sputtering under different He partial pressure. The creep properties of the Er2O3 films under different temperatures ranging from ambient temperature to 450 °C were investigated systematically by nanoindentation measurements. The morphology and microstructure of the films were determined by a scanning electron microscope (SEM) and an X-ray diffractometer (XRD), respectively. The effects of He on the creep properties of the Er2O3 film were discussed by using a slope (dε˙/dσ) of the creep rate stress curve at the steady-state creep stage. The results show that the crystallinity of the films became weak with the He partial pressure. Furthermore, the implanting He has a strong impact on the creep resistance of the Er2O3 thin films.

Comprehensive investigation of Er2O3 thin films grown with different ALD approaches

The effect of Er precursor nature (Er(CpMe)3 or Er(tmhd)3) and annealing treatment at 500–1100 °C on the structural and optical properties of Er2O3 films grown on Si substrates by thermal or O2-plasma-assisted atomic layer deposition was studied by means of spectroscopic ellipsometry, Fourier-transform infrared spectroscopy, X-ray diffraction, transmission electron microscopy coupled with energy dispersive X-ray spectroscopy as well as photoluminescence method. An annealing at 500–800 °C resulted in the film crystallization mainly. Thermal treatment at high temperatures caused the formation of Er silicate phase due to the diffusion of Si atoms from the substrate in the films depth. This phase was found to be Er2SiO5 being crystallized at 1100 °C. Light emitting properties of the films are determined by Er2O3 native defects (like oxygen vacancies) and intra-4f shell transition in Er3+ ions. The latter dominated in the films annealed at 1000–1100 °C. The most intense Er3+ emission, observed in the films grown with O2-plasma-assisted approach, was explained by a lower contribution of oxygen vacancies as well as by pronounced crystallization of Er silicate phase. In this latter, the effect of concentration quenching of Er3+ luminescence was lower due to a larger distance between Er3+ neighbor ions.

Microstructure and properties of La-doped Er2O3 anti-reflection films on CVD diamond

The composition and microstructure consisting of anti-reflection films was obtained by the power of magnetron sputtering. X-ray photoelectron spectroscopy (XPS) and High-resolution transmission electron microscopy (HRTEM) provided evidence to support that the doping La element exists as oxide in the grain boundaries of the matrix Er2O3 films. The undoped and La-doped Er2O3 films show a columnar crystal structure of the main cubic (222) plane. Twinning and a large number of dislocations show up in the undoped Er2O3 films due to the competitive growth of the columnar crystal. In addition, the La-doped Er2O3 films show a lower roughness (RMS) value in comparison with undoped Er2O3 films. The grain size of columnar crystals decreases significantly with increasing La concentration in the La-doped Er2O3 films. The fine grains resulted in the La-doped Er2O3 films developing high mechanical and impact resistance properties, with an increase in hardness from 12.6 ± 2.1 GPa to 26.1 ± 3.4 GPa and the eroding area rate decreasing from 38.9 % to 1.9 %. Moreover, the La-doped Er2O3 anti-reflection films on the chemical vapor deposition (CVD) diamond substrate maintained 74 % transmittance in the long-wavelength infrared range of 8–12 μm after sand eroding.

The relationship between structural and electrical properties of the post-deposition annealed Er2O3/n-Si hetero-structures

This study presents comprehensive results on the structural modifications of Er2O3/n-Si hetero-structures under post-deposition annealing (PDA) and the effects of these changes on the electrical characteristics of the Al/Er2O3/n-Si/Al MOS capacitors. The Er2O3 films were grown on n-Si substrate with RF magnetron sputtering and annealed under nitrogen at RT, 300 °C, 500 °C, 600 °C, 700 °C. The increasing grain size of the films up to 300 °C did not show a significant change in other annealing temperatures. The erbium silicate content in the RT and 600 °C-Er2O3/n-Si interface is quite higher than those of 500 °C and 700 °C, while a silicate-like layer was not found at 300 °C. The highest dielectric constant (ε) value was obtained from the 500 °C-Er2O3 MOS capacitor due to the lowest oxygen deficient bond content. It was found that Qeff values tend to increase as the oxygen concentration decreases in the film. It was determined that Er-Er oxygen deficient bonds may have acted as negative charge trap centers. Although the Er-M content in the 700 °C-Er2O3/n-Si is higher than that of 500 °C, lower Qeff values were obtained from the 700 °C-Er2O3 MOS capacitor due to the higher Si-Si oxygen deficient bond content, which is most likely act as a positive charge trap center. It was concluded that the contributions of oxide trap and interface trap charges should be evaluated together in establishing a link between electrical characteristics and structural analyses.

Effect of annealing temperature on the electrical characteristics of Al/Er2O3/n-Si/Al MOS capacitors

In this work, Er2O3 films deposited by electron beam (E-beam) evaporation technique were annealed at 450 °C, 550 °C, and 650 °C in N2 atmosphere for 30 min. We then compared the electrical properties, the frequency dependency of the density of interface states, and series resistance of as-deposited and annealed Al/Er2O3/n-Si/Al MOS capacitors. The grain size measurements carried out by X-ray diffractometer (XRD) and the root mean square (RMS) surface roughness values obtained by atomic force microscopy (AFM) increased with an increase of annealing temperature. The C-V and G/ω-V measurements were carried out at a frequency of 1 MHz for as-deposited and annealed MOS capacitors. The capacitance in the accumulation region decreased with an increase in annealing temperature, and the capacitor film annealed at 450 °C had the highest capacitance in the accumulation region as well as high-k value, and low barrier height. In addition, the C-V and G/ω-V measurements carried out in the frequency range of 20 kHz to 1 MHz were analyzed to understand the effect of frequency on the series resistance Rs and interface states Dit. The measured and calculated results reveal a significant influence of frequency on both Rs and Dit of the fabricated MOS capacitor characteristics.

Effect of in-flight particle behavior on the morphology of flame sprayed Er2O3 splats

The morphology and microstructure of splats impact the comprehensive capability of a new coating methodology called chelate flame spraying (CFS). This study addresses the quantitative characterization of the spread morphologies of flame sprayed Er2O3 splats directly deposited under different spray conditions on aluminum alloy substrates with a mirror finish. The influence of the in-flight particle temperature and velocity, carrier gas type, and carrier gas ratio on the solidification mechanism of molten droplets was investigated. Image analysis methods were employed to identify single splats from the morphology observed with field-emission scanning electron microscopy (FE-SEM). In addition, Er2O3 films were synthesized on an Al–Mg alloy (A5052) substrate using N2 or O2 as the carrier gas. When O2 was used as the carrier gas, 109-μm-thick films were deposited on the A5052 substrate. The cross-sectional porosity of the films was 3.8%. In contrast, films with 101-μm thickness were synthesized on the A5052 substrate when N2 was used as the carrier gas. The cross-sectional porosity of these films was 13.8%. The results showed that the carrier gas type (N2) and carrier gas ratio had a significant effect on the flattening behavior of the molten droplets. A spraying method combined with multidimensional modes is proposed to control the morphology of the splats.

Microstructure, hardness and optical properties of Er2O3 films deposited on diamond-coated and Si(100) substrates by radio frequency magnetron sputtering

Er2O3 anti-reflection films were deposited on the surface of the chemical vapor deposited diamond films and Si(100) substrates by radio frequency magnetron sputtering. The microstructure of the Er2O3 thin films and the interfacial layer were investigated by means of scanning electron microscopy, X-ray diffraction, atomic force microscopy and transmission electron microscopy. The refractive index, hardness and transmittance of the films were measured by ellipsometry, nanoindentation measurements, and Fourier transformed infrared spectroscopy. Results revealed that the bias induces the formation of a monoclinic phase and the nucleation of the Er2O3 thin films is mainly observed along the (222) plane. A high-resolution TEM image revealed a 2.5-nm-thick amorphous layer at the interface between the Si substrate and Er2O3 film. Notably, monoclinic Er2O3 films can considerably improve the transmittance of the diamond film in the long-wavelength infrared range of 8–12 μm via the reduction of the refractive index. However, the introduction of the monoclinic phase led to the decrease of the hardness and elastic modulus of the films; hence, controlling a suitable amount of the monoclinic phase may play an extremely important role in the mechanical and optical properties of the Er2O3 films.

Thermally induced evolution of optical and structural properties of Er2O3 films grown on Si substrates by thermal atomic layer deposition

Thermally induced evolution of structural and optical properties of Er2O3 films prepared by atomic layer deposition was investigated. The films were grown on Si substrates by water-assisted approach from (tris(methylcyclopentadienyl)erbium(III). As-deposited films showed cubic Er2O3 phase, and compressive stress. Isochronal (30 min) heating at 600–1100 °C in nitrogen flow caused strain relaxation, decrease of the lattice parameters and the increase of coherent domain size. Besides, in the films annealed at 1000–1100 °C, the formation of Er silicate phase was observed. This phase formed due to Si diffusion from substrate in film volume, and the presence of Si was found not only at the film/substrate interface, but also on the top surface of the film. This fact was explained by spinodal decomposition of Er silicate with the formation of Er2SiO5 phase on top surface. It was shown that both oxygen vacancies and Er3+ ions contribute to light emission, however, no energy transfer from vacancies to Er3+ ions was detected.

Preparation and characterization of Er2O3 films on CLAM steel via sol-gel method

Er2O3 coating is one of the candidate tritium permeation barriers (TPB) to reduce tritium permeation and leakage in fusion reactors. A series of Er2O3 coatings were synthesized on China Low Activation Martensitic (CLAM) steel via sol-gel method, and systematic investigate the influence of synthesis parameters for on microstructure and properties of the Er2O3 coatings. The results showed that no cracks were observed in Er2O3 coatings as chosen 11 vol.% diethanolamine. The best heat treatment temperature could be thought 600 °C, in order to obtain a homogeneous and dense Er2O3 coating with high hardness, good crystallization and strong bonding to the substrate.

Synthesis and photoluminescence properties of erbium oxide thin films prepared by sol-gel method

This study used the sol-gel reaction to synthesize an erbium oxide precursor. The precursor was coated on a hydrophilic SiO2/Si substrate by using spin coating technology, which was then processed at the temperature of 600–1100°C for 45min to form erbium oxide and erbium silicate thin films. The film obtained from a 600°C reaction is smooth and crack-free, and it binds well to the substrate. A grazing incidence X-ray diffractometer, scanning electron microscope, and photoluminescence spectrometer were used to analyze the material structure, appearance, and optical properties of each film that was obtained and to compare the effects of different reaction conditions on material structure and optical properties. The results indicated that the Er2O3 films fabricated by 1000°C annealing will subsequently form Er2SiO5 after reacting with SiO2 and were characterized by optimal luminescent properties, which made them applicable for use in future optoelectronic devices.

Preparation of Er2O3 and TiO2 Multilayer Films as Optical Filter Using Magnetron Sputtering Deposition

Dispersion relations of refractive indexes and extinction coefficients of constituent materials were obtained by comparing the experimental and simulated transmission spectra of single-layer Er2O3 and TiO2 films. We designed multilayer thin films of [Er2O3/TiO2]6/[Er2 O3]2/[TiO2/Er2O3]6 such that they can act as photonic crystals exhibiting a resonance wavelength of 514 nm. We prepared single-layer TiO2 and Er2O3 thin films on quartz glass substrates by employing a magnetron sputtering deposition method. Uniform films exhibiting very high transmittance values were obtained. Deposition rates of the TiO2 and Er2O3 films were 0.44 and 0.82 nm/s, respectively. [Er2O3/TiO2]6/[Er2 O3]2/[TiO2/Er2O3]6 multilayer films, to be used for optical bandpass filter applications, were also prepared using a multitarget sputtering deposition method. Uniform and transparent films were obtained; however, the wavelength corresponding to the highest transmittance was observed around 490 nm through ultraviolet-visible near-infrared spectroscopic measurements. The shift in the wavelength can be attributed to the low crystallinity and variations in the thicknesses of Er2O3 and TiO2 films.

Nanoscale investigations: Surface potential of rare-earth oxide (Re2O3) thin films by kelvin probe force microscopy for next generation CMOS technology

Here, the surface morphology, quantitative surface charge injection in nanoscale regime, spreading, decay and physical significance of trap charges are systematically investigated on furnace annealed (FA) and rapid thermal annealed (RTA) ultrathin rare earth oxide (Re2O3), Er2O3/Si structure by Kelvin probe force microscopy (KPFM). The computed charge decay and contact potential difference (CPD) are found as a strong function of injected charges along with the type of subjected post deposition annealing treatment. The RTA treated Er2O3 films showed higher CPD value (∼266mV) and lowest charge spreading (∼2.1µm) for trapped holes than the FA (CPD ∼196mV and charge spreading ∼2.27µm). The CPD for negative bias are computed higher (∼196mV and ∼266mV) than that of the corresponding positive (∼–184mV and ∼-229mV) in both FA and RTA treated Er2O3/Si structures, respectively. It reveals easier holes trapping than electrons and n-type nature of sputtered Er2O3 ultrathin films. There is a significant ∼80% vertical charge decay and ∼20% lateral spreading for first 60min due to conjunction of effective injected and polarization charges. Thus, the FA and RTA treated Er2O3 films are potential candidates for CMOS and NVRAM applications, respectively.

Fabrication and Hydrogen Permeation Properties of Epitaxial Er2O3 Films Revealed by Nuclear Reaction Analysis

In order to evaluate the potential of erbium oxide films in applications such as hydrogen (H) permeation barriers, we fabricated high-quality Er2O3 thin films by ion beam sputter deposition on Si(100) as an epitaxial substrate. The physical structures of the thin films were characterized by scanning X-ray diffraction, and the process of hydrogen permeation through the Er2O3 films upon annealing in H2 was elucidated by H depth profiling with nuclear reaction analysis. The results show that quasi-single-crystalline Er2O3(110) thin films can be produced that feature a hydrogen solubility, diffusivity, and permeability at 873 K of (1.1 ± 0.2) × 102 mol m–3, (7.2 ± 1.4) × 10–22 m2 s–1, and (3.8 ± 1.5) × 10–22 mol Pa–1/2 m–1 s–1, respectively. The remaining difference in hydrogen permeability between our quasi-single-crystalline Er2O3(110) thin films and that expected for ideal bulk Er2O3 attests to the negative role of residual defects (e.g., pores) that exist in the thin films.

Study on the Structural Properties of Polycrystalline Er<sub>2</sub>O<sub>3</sub> Films on SI(001) Substrates by Raman Spectra

The Raman spectra of polystalline Er2O3 films on Si (001) substrates annealed at different temperatures in O2 atmosphere were investigated. Seven Raman lines are identified in annealed Er2O3 films on Si (001) substrates. Two broad peaks larger than 600 cm-1 are detected, and their origination is discussed. Raman spectroscopy is proved to be a simple and sensitive method to characterize the structures of Er2O3 films on Si substrates.

Features of phase formation of Er2O3 films during electron-beam evaporation

Crystalline Er2O3 films on sapphire and silicon substrates have been prepared by electron beam evaporation technique in vacuum. Preparation of a single-phase erbium oxide film with a cubic lattice and preferred (400) orientation was achieved by means of growth rate decrease. Structural and optical properties of obtained films before and after short-time annealing were investigated. It is shown that the preparation of a single-phase erbium oxide film with a cubic lattice and preferred (222) orientation can be achieved by post-growth annealing of the films grown at usual rates.