Sm2O3 Thin Films Research Articles

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.

The Sensitivity of V2O5:Sm2O3 Thin Films against NO2 Toxic Gas

Vanadium oxide V2O5 thin films with variation doping ratios of Sm2O5 (2, 4, 6, and 8 % wt.) on corn glass and p- type silicon substrates were prepared by pulsed laser method. The X-ray diffraction peaks for V2O5 decreases with doping ratio of Sm2O3. FESEM images for V2O5 and doped thin films illustrates clusters with a homogeneous distribution in nano scale. The energy gap varied upon the increment of doping concentration, starting from 2.610 eV to 2.7 eV. Gas sensor measurement of pure and doped V2O5 demonstrated a sensitivity to NO2 gas, and the sensitivity expanded upon the increment of operation temperature. The greatest sensitivity was found to be about 99%, while best response time of 10s and recovery time of 18s were recorded using the 4% Sm2O3 sample at 50 °C.

Bipolar resistive switching characteristics of samarium oxide solid electrolyte thin films for non-volatile memory applications

In this paper, we report the bipolar resistive switching behaviors in Ag/Sm2O3/Pt structures where the Sm2O3 thin films act as solid electrolyte layer of electrochemical metallization memory (ECM) devices. The memory devices show reproducible and stable bipolar resistive switching over 1000 cycles with a resistance ratio (high-resistance state to low-resistance state) of over 4 orders of magnitude and stable retention for over 104[Formula: see text]s at room temperature. Moreover, the benefits of high yield and multilevel storage possibility make the device promising in the next generation non-volatile memory application.

Trap-assisted tunneling, capacitance–voltage characteristics, and surface properties of Sm2O3 thin film on Si substrate

The morphology, topography, and electrical properties of sputtered pure samarium metal film on silicon substrates which thermal oxidized in oxygen ambient at various temperatures (600–900 °C) for 15 min had been investigated quantitatively. Effects of oxidation temperature on the morphology, topography, and electrical properties of Sm2O3 thin film were reported. Metal–oxide–semiconductor capacitors were fabricated before current–voltage measurement and capacitance–voltage measurement. The roughness and uniformity of Sm2O3 thin films were revealed by scanning electron microscope and atomic force microscopy analysis. The sample oxidized at 700 °C demonstrated the highest electrical breakdown field (0.7 MV cm−1), lowest leakage current density (10−4 A cm−2), highest barrier height value (2.13 eV), highest trap energy (0.00075 eV), lowest trap density (6.88 × 1021 cm−3), highest capacitance (1050 pF), and highest effective dielectric constant (214). This is attributed to the lowest effective oxide charge (2.81 × 1013 cm−2), slow trap charge density (5.56 × 1012 cm−2), average interface trap density (~1014 eV−1 cm−2), and total interface trap density (7.31 × 1013 cm−2).

Optical characteristics of transparent samarium oxide thin films deposited by the radio-frequency sputtering technique

Transparent metal oxide thin films of samarium oxide (Sm2O3) were prepared on pre-cleaned fused optically flat quartz substrates by radio-frequency (RF) sputtering technique. The as-deposited thin films were annealed at different temperatures (873, 973 and 1073 K) for 4 h in air under normal atmospheric pressure. The topological morphology of the film surface was characterized by using atomic force microscopy (AFM). The optical properties of the as-prepared and annealed thin films were studied using their reflectance and transmittance spectra at nearly normal incident light. The estimated direct optical band gap energy ( $E_{\mathrm {g}}^{\mathrm {d}}$ ) values were found to increase by increasing the annealing temperatures. The dispersion curves of the refractive index of Sm2O3 thin films were found to obey the single oscillator model.

Methanol Adsorption and Reaction on Samaria Thin Films on Pt(111).

We investigated the adsorption and reaction of methanol on continuous and discontinuous films of samarium oxide (SmOx) grown on Pt(111) in ultrahigh vacuum. The methanol decomposition was studied by temperature programmed desorption (TPD) and infrared reflection absorption spectroscopy (IRRAS), while structural changes of the oxide surface were monitored by low-energy electron diffraction (LEED). Methanol dehydrogenates to adsorbed methoxy species on both the continuous and discontinuous SmOx films, eventually leading to the desorption of CO and H2 which desorbs at temperatures in the range 400–600 K. Small quantities of CO2 are also detected mainly on as-prepared Sm2O3 thin films, but the production of CO2 is limited during repeated TPD runs. The discontinuous film exhibits the highest reactivity compared to the continuous film and the Pt(111) substrate. The reactivity of methanol on reduced and reoxidized films was also investigated, revealing how SmOx structures influence the chemical behavior. Over repeated TPD experiments, a SmOx structural/chemical equilibrium condition is found which can be approached either from oxidized or reduced films. We also observed hydrogen absence in TPD which indicates that hydrogen is stored either in SmOx films or as OH groups on the SmOx surfaces.

Samarium oxide thin films deposited by reactive sputtering: Effects of sputtering power and substrate temperature on microstructure, morphology and electrical properties

In this study, the effects of increase in sputtering power and substrate temperature on the microstructural, morphological and electrical characteristics of Sm2O3 thin films have been reported. All films were deposited at 50°C with varying in sputtering power from 100 to 250W in 50W steps by the reactive sputtering technique. The crystallization, grain size, and d-spacing of the films were determined by an X-ray diffractometer (XRD). The semi-quantitative compositional changes were investigated by energy-dispersive X-ray (EDX) spectroscopy while microstructural and morphological modifications were studied by atomic force microscopy (AFM). In addition, the electrical evolutions of the films were determined by alternating current (a.c.) conductivity. It was observed that the crystallization of the films was increased with increase in sputtering power up to 200W and decreased at the power of 250W. Therefore, the films deposited at 200W were annealed at 50°C, 125°C, and 200°C, and a continuous crystallization improvement was observed. The composition of the films was improved by both sputtering power and increase in substrate temperature. The grain boundaries and surface roughness of the films were also found to be significantly affected by the change in substrate temperature. The a.c. conductivity of the films gradually decreases from 1.10×108Ω−1cm−1 to 2.50×106Ω−1cm−1 by increase in sputtering power and substrate temperature. The results show that the Sm2O3 thin films fabricated at 200W sputtering power and 200°C substrate temperature exhibit requested structural and morphological characteristics.

Optical Properties of RF Sputtered Samarium Oxide Thin Films

This paper reports the optical properties of prepared samarium oxide Sm2O3 thin films nanoparticles using RF sputtering technique. X-ray diffraction is used to examine and characterize the prepared films. Optical measurements are carried out by employing U...

Current conduction and resistive switching characteristics of Sm2O3 and Lu2O3 thin films for low-power flexible memory applications

In this article, the current conduction and resistive switching (RS) behavior in flexible Sm2O3 and Lu2O3 resistive random access memories (ReRAM) are investigated. Amorphous Sm2O3 and Lu2O3 thin films were deposited at room temperature by radio-frequency magnetron sputtering on flexible polyethylene terephthalate substrate. The structural morphologies of the Sm2O3 and Lu2O3 thin films strongly depend on the lattice energy of the oxides. The dominant current conduction mechanism in the oxide layer changes from electrode control Schottky emission in Sm2O3 to bulk controlled space-charge-limited-current in Lu2O3. The barrier height extracted from Schottky emission model is 0.96 eV in Sm2O3 thin film, while the activation energy of traps calculated from the Arrhenius plots is about 0.23 eV in Lu2O3 thin film. Additionally, the Ni/Sm2O3/ITO flexible memory device shows promising RS behavior with very low power of operation (∼30 μW) and small distribution of switching parameters. The memory reliability characteristics of switching endurance, data retention, good flexibility, and mechanical endurance show promising for future memory applications. The filament conduction model is adopted to describe the RS behavior in the Sm2O3 and Lu2O3 ReRAM devices. The improved RS performance in Sm2O3 thin film is attributed to the different physical properties of the thin films.

Growth and Partial Reduction of Sm2O3(111) Thin Films on Pt(111): Evidence for the Formation of SmO(100)

We investigated the growth and partial reduction of Sm2O3(111) thin films on Pt(111) using low energy electron diffraction (LEED) and scanning tunneling microscopy (STM). We find that the Sm2O3(111) films are high quality and grow in a defective fluorite structure wherein the Sm cations adopt a hexagonal (1.37 × 1.37) lattice in registry with the Pt(111) surface, while oxygen vacancies are randomly distributed within the film. STM measurements show that Sm2O3(111) film growth on Pt(111) occurs by the Stranski-Krastanov mechanism, in which a single O–Sm–O trilayer initially forms, followed by the growth of well-defined, multilayer islands. The Sm2O3(111) films undergo partial reduction during annealing at 1000 K in ultrahigh vacuum. LEED and STM provide evidence that a fraction of the Sm2O3 in the first layer, closest to the Pt(111) substrate, decomposes to produce well-ordered domains of rocksalt SmO(100) during reduction, and that Sm2O3 from the third and higher layers concurrently spreads onto the first layer to form a more contiguous second layer of Sm2O3(111). We show that the SmO(100) and Sm2O3(111) lattices can form a coincidence structure with minimal strain to the Sm-atom sublattices, and that satellite features observed in the LEED patterns are consistent with the coexistence of SmO(100) and Sm2O3(111) domains as well as the proposed Sm2O3(111)/SmO(100) coincidence structure. Lastly, we find that reoxidation of the partially reduced films restores the original Sm2O3(111) crystal structure, and significantly improves the film quality, as reflected by a flatter film morphology and better connectivity among oxide domains. An implication from this study is that the formation of (100)-oriented monoxide structures is a general characteristic of the reduction of rare-earth oxide thin films on hexagonally close-packed metal surfaces.

Influence of deposition conditions on electrical and mechanical properties of Sm2O3-doped CeO2 thin films prepared by EB-PVD (+IBAD) methods. Part 1: Effective relative permittivity

Study is devoted to the effective relative permittivity ɛr of CeO2+x. Sm2O3 thin films prepared by electron-beam physical vapour deposition and ionic beam-assisted deposition methods; ɛr was investigated by three independent ways from the bulk parallel capacitance Cp, impedance capacitance Cimp, and accumulation capacitance Cacc in dependence on the deposition conditions (deposition temperature, dopant amount x and Ar+ ion bombardment during the film deposition) used. Investigations were performed using impedance spectroscopy, capacitance–voltage and current–voltage characteristics as well as deep level transient spectroscopy. Results obtained are described and discussed.

Dynamic superparamagnetism in cobalt doped Sm2O3 thin films

We report on the magnetic properties of insulating Sm1.9Co0.1O3 films grown on a SrTiO3 substrate. A pulsed laser deposition technique was used to grow the films under varied oxygen pressure. The films were characterized using several techniques, including x-ray diffraction, high-resolution transmission electron microscopy, and magnetic property measurements. Films prepared at lower oxygen pressures were found to be monoclinic, whereas the films prepared at high oxygen pressures were cubic. Both film phases exhibited superparamagnetic-like responses, with the monoclinic films showing a very high coercive field at low temperatures. Careful microstructural analysis showed no secondary phases or compositional variation that could account for the observed magnetic response. A model, based on the widely accepted bound polaron theory for insulating ferromagnets, is proposed to explain the magnetic behavior of Co doped Sm2O3 films. In this model, exchange mediating defects form magnetically active regions that behave like superparamagnetic clusters; however, unlike in superparamagnetic systems, the size of magnetically active regions is not static but changes dynamically with temperature.

Solution Derived ${\rm Sm}_{2}{\rm O}_{3}$ Films on Biaxially Textured Ni-W Substrates

Sm2O3 thin films have been prepared on biaxial textured Ni-5%W metallic substrates by chemical solution deposition. Precursor film crystallizes at 1000°C in reduced atmosphere and forms a pure Sm2O3 cubic phase with (004) orientation. The Sm2O3 film shows an excellent biaxial texture. A homogenous and crack-free surface is observed.

Effects of post-deposition annealing temperature and ambient on RF magnetron sputtered Sm2O3 gate on n-type silicon substrate

Samarium oxide (Sm2O3) thin films with thicknesses in the range of 15–30 nm are deposited on n-type silicon (100) substrate via radio frequency magnetron sputtering. Effects of post-deposition annealing ambient [argon and forming gas (FG) (90% N2 + 10% H2)] and temperatures (500, 600, 700, and 800 °C) on the structural and electrical properties of deposited films are investigated and reported. X-ray diffraction revealed that all of the annealed samples possessed polycrystalline structure with C-type cubic phase. Atomic force microscope results indicated root-mean-square surface roughness of the oxide film being annealed in argon ambient are lower than that of FG annealed samples, but they are comparable at the annealing temperature of 700 °C (Argon—0.378 nm, FG—0.395 nm). High frequency capacitance–voltage measurements are carried out to determine effective oxide charge, dielectric constant and semiconductor-oxide interface trap density of the annealed oxide films. Sm2O3 thin films annealed in FG have smaller amount of effective oxide charge and semiconductor-oxide interface trap density than those oxide films annealed in argon. Current–voltage measurements are conducted to obtain barrier heights of the annealed oxide films during Fowler–Nordheim tunneling.

Orientation Growth and Optical Properties of Sm<sub>2</sub>O<sub>3</sub> Thin Films

Sm2O3 optical thin film is a new photovoltaic material and has potential applications in optical switches, date recording device and magnetic device. Using samarium dichloride as raw material, Sm2O3 optical thin films were prepared by sol-gel and hydrothermal process on glass and Si (100) substrates. The phase compositions, morphologies and optical properties of the as-prepared thin films were analyzed by X-ray diffraction (XRD), atomic force microscope (AFM) and UV-vis spectrophotometer (UV-vis). Results show that the Sm2O3 thin films prepared by sol-gel method exhibit an obvious (110) orientation growth on glass substrates, while the Sm2O3 thin films prepared with hydrothermal method have no obvious orientation. The as-prepared films have excellent absorbency of UV light and are transparent to visible light. The band gap of the Sm2O3 films prepared by hydrothermal method is narrower than that of those obtained by sol-gel method. The absorbency of UV light and transparence to visible of the Sm2O3 films prepared by sol-gel method are obviously improved in comparison with those deposited by hydrothermal process.

Temperature Dependence of the Current Conduction Mechanisms in Sm2O3 Thin Films

Metal-oxide-semiconductor capacitors with dielectric film were fabricated and the temperature dependence of the conduction mechanisms was studied. The films were deposited by radio frequency magnetron sputtering. The thickness of was . The dielectric permittivity and the equivalent oxide thickness of capacitors with film were 15.0 and , respectively. The X-ray photoelectron spectroscopy analysis showed a silicate interfacial layer formed between and Si. When the aluminum electrode was biased positive, the dominant conduction mechanism was Schottky emission in the temperature range and at an electrical field of . In the temperature range , the dominant conduction mechanism was most likely space-charge-limited conduction. When the aluminum electrode was biased negative, the dominant conduction mechanism in the temperature range from and at an electrical field from was Schottky emission. At and with the electrical field above , the conduction mechanism was Fowler—Nordheim (F–N) tunneling. The electron barrier height and the effective electronic mass calculated from Schottky emission and F–N tunneling were and , respectively.

Structural and dielectric properties of epitaxial Sm2O3 thin films

Epitaxial Sm2O3 thin films were deposited on (001) SrTiO3 substrates by pulsed laser deposition. The structural and dielectric properties were investigated. Microstructural studies by x-ray diffraction and transmission electron microscopy showed that the Sm2O3 thin films have a cubic structure and an epitaxial relationship of (004)Sm2O3∥(002)SrTiO3 and [440]Sm2O3∥[200]SrTiO3. A high dielectric constant of 30.5 was found, which can be attributed to the cubic structure and the high crystalline quality and shows a potential application of epitaxial Sm2O3 thin film for high-k material.

Influence of hydrothermal reaction time on phases, morphologies and optical properties of Sm2O3 thin films

The Sm2O3 thin films were deposited on glass substrates by hydrothermal method using samarium dichloride as a raw material. The influences of the hydrothermal reaction time on the phases, microstructures and optical properties of the thin films were investigated. The as prepared thin films were characterised by X-ray diffraction, atomic force microscopy and UV–Vi absorption. Results show that the grain size, peak intensity and orientation growth of Sm2O3 crystallites thin films increase with reaction time during a 48 h period, and then decrease with further time. The band gap of the as prepared thin films measured by UV–Vi absorption reveals that the variation of the band gap of the thin film with reaction time shows an opposite trend compared with that of the grain size, and the band gap of the thin films is calculated to be 3˙79–3˙95 eV.