Er2O3 Films Research Articles

Atomic layer deposition and characterization of stoichiometric erbium oxide thin dielectrics on Si(1 0 0) using (CpMe)3Er precursor and ozone

Thin stoichiometric erbium oxide films were atomic layer deposited on p-type Si(100) substrates using tris(methylcyclopentadienyl)erbium and ozone. The film growth rate was found to be 0.12±0.01nm/cycle with an atomic layer deposition temperature window of 170–330°C. X-ray photoelectron spectral (XPS) analysis of the resulting Er2O3 films indicated the as-deposited films to be stoichiometric with no evidence of carbon contamination. Studies of post deposition annealing effects on resulting films structures, interfaces, surface morphologies, and electrical properties were done using Fourier transform infrared spectroscopy, XPS, glancing incidence X-ray diffraction, optical surface profilometry, and C–V/I–V measurements. As-deposited Er2O3 films were found to start crystallizing in the cubic structure with dominant (222) orientation; no erbium silicate was found at the interface. After annealing at 800°C in N2, a new XPS feature was found and it was assigned to the formation of erbium silicate. As the annealing temperature was increased, the interfacial erbium silicate content was found to increase in the temperature range studied. Electrical characterization of Er2O3 thin gate dielectrics annealed at 600°C exhibited higher dielectric constant (κ=11.8) than that of as-deposited films (9.8), and a remarkably low hysteresis voltage of less than 50mV along with a leakage current density of 10−7Acm−2 at 1MVcm−1.

Response to “Comment on ‘Forming-free resistive switching in Nd2O3, Dy2O3, and Er2O3 films fabricated in full room temperature’” [Appl. Phys. Lett. 100, 076101 (2012)

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Comment on “Forming-free resistive switching behavior in Nd2O3, Dy2O3, and Er2O3 films fabricated in full room temperature” [Appl. Phys. Lett. 99, 113509 (2011)

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The characteristics of the high-[formula omitted] Er2O3 (erbium oxide) dielectrics deposited on polycrystalline silicon

The high-k Er2O3 films deposited on polycrystalline silicon treated with various post-rapid thermal annealing (RTA) temperatures were formed as high k dielectrics. In order to study the annealing effects, electrical measurements, optical characterizations, and multiple material analyses techniques including X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and atomic force microscopy (AFM) were performed to examine the differences between the samples in various annealing conditions. The annealing temperature at 800 °C was the optimal condition to form a well-crystallized Er2O3 film with excellent material quality and electrical properties. RTA annealing at an appropriate annealing temperature of 800 °C might effectively mitigate the dangling bonds and traps and improve electrical and material properties of the dielectric.

Sc2O3, Er2O3, and Y2O3 thin films by MOCVD from volatile guanidinate class of rare-earth precursors

Alternative novel precursor chemistries for the vapor phase deposition of rare-earth (RE) oxide thin films were developed by synthesising the homoleptic guanidinate compounds tris(N,N'-diisopropyl-2-dimethylamidoguanidinato)-scandium(III) [Sc(DPDMG)(3)] (1), tris(N,N'-diisopropyl-2-dimethylamidoguanidinato)-erbium(III), [Er(DPDMG)(3)] (2) and tris(N,N'-diisopropyl-2-dimethylamidoguanidinato)-yttrium(III), [Y(DPDMG)(3)] (3). All three compounds are monomeric as revealed by single crystal X-ray diffraction (XRD) analysis, nuclear magnetic resonance (NMR) and electron impact mass spectrometry (EI-MS). The thermal analysis revealed that the compounds are volatile and very stable under evaporation conditions. Therefore the complexes were evaluated as precursors for the growth of Sc(2)O(3), Er(2)O(3) and Y(2)O(3) thin films, respectively, by metal-organic chemical vapor deposition (MOCVD). Uniform Sc(2)O(3), Er(2)O(3) and Y(2)O(3) films on Si(100) substrates with reproducible quality were grown by MOCVD by the combination of the respective guanidinate precursors and oxygen in the temperature range 350-700 °C. The structural, morphological, compositional and electrical properties of the films were investigated in detail. The most relevant film properties are highlighted in relation to the distinct advantages of the novel precursor chemistries in comparison to the commonly used literature known RE precursors. This study shows that compounds 1-3 are very good precursors for MOCVD yielding Sc(2)O(3), Er(2)O(3) and Y(2)O(3) thin films which are stoichiometric and display suitable electrical properties for their potential use as high dielectric constant (high-k) materials.

Temperature effects on the growth and electrical properties of Er2O3 films on Ge substrates

Er2O3 films were grown on Ge (001) substrates at different temperatures by molecular beam epitaxy using metallic Er and molecular oxygen sources with otherwise identical conditions. High-resolution transmission electron microscopy and X-ray photoelectron spectroscopy were used to characterize the microstructures and compositions of the films. The film deposited at room temperature is found to be composed of an Er2O3 layer and an ErGexOy interface layer with a thickness of 5.5nm; the film grown at 300°C has a mixed structure of Er2O3 and ErGexOy and the thickness was found to be reduced to 2.2nm; the film grown at 450°C becomes much rougher with voids formed underneath the film, having a mixed structure of three compounds of Er2O3, GeO and ErGexOy. The growth mechanisms of the films at different temperatures are suggested. Current images obtained by tunneling atomic force microscopy show that the film grown at 450°C has much more leaky spots than those grown at RT and 300°C, which may arise from the formation of volatile GeO in the film.

Forming-free resistive switching behavior in Nd2O3, Dy2O3, and Er2O3 films fabricated in full room temperature

In this study, we reported the forming-free resistive switching behavior in the Ru/RE2O3/TaN (RE = Nd, Dy, and Er) memory devices using thin Nd2O3, Dy2O3, and Er2O3 films fabricated with full room temperature process. The dominant conduction mechanisms of the Ru/RE2O3/TaN devices in the low-resistance state and high-resistance state are Ohmic behavior. The Ru/Dy2O3/TaN memory device exhibited high resistance ratio, nondestructive readout, reliable data retention, and good endurance. Ru/Dy2O3/TaN memory device has a great potential for the application in nonvolatile resistive switching memory.

Photo- and Electro-Luminescence at 1.54 μm from Er3+ in SiC:Er2O3 Films and Structures

SiC:Er2O3 films with different ratios of SiC to SiC:Er2O3 are deposited on p-type Si substrates by the magnetron co-sputtering technique, which was fully compatible with current Si processing technologies. Intense room temperature 1.54 μm photoluminescence (PL) from Er3+ ions in the SiC:Er2O3 films is observed and the PL intensity at 1.54 μm is enhanced by about 40 times with increasing Er concentration in the films from 0.8 to 22 at.% under both direct and indirect excitations. The 1.54 μm electroluminescence from the structure of indium tin oxide (ITO)/n+ -Si/SiC:Er2O3/p-Si with suitable ratios of SiC to SiC:Er2O3 is measured under forward biases.

Study on the Growth of Crystalline Er<sub>2</sub>O<sub>3</sub> Films on Si Substrates by RHEED Patterns

Er2O3 films with good crystallinity have been achieved on an oxidized Si (111) surface by molecule beam epitaxy. The initial growth of Er2O3 films epitaxially grown on Si surfaces is investigated by in situ reflection high energy electron diffraction. An interface layer was formed at the very beginning of the growth of Er2O3 film on Si, which is supposed to be attributed to the Er atom catalytic oxidation effect. The results obtained indicate that with the film growth process continued, oxygen deficient Er oxide captures oxygen from the interface layer which is formed inevitably at the initial growth of Er2O3 film and thus reduce and even remove the interface layer if the condition of O2 pressure is insufficient at a high substrate temperature such as 700°C in our case.

Study on the Luminescence and Reflection Spectra of Al2O3 Doped Er2O3 Films on Si Substrates

Amorphous Al2O3 doped Er2O3 films were deposited on Si(001) substrates by radio frequency magnetron sputtering technique. Emission spectra exhibit a strong emission band around 410 nm and a series of emission band near 970, 980, 1018, 1042 and 1080nm. Ellipsometry measurements show that the refractive indexof the ErAlO films in the region of 400～1000 nm is between 1.76-1.83. The reflectivity of the ErAlO on Si is much smaller than that of clean Si and pure Er2O3 films. All the results indicate that ErAlO could be a promising material for Si solar cells.

Epitaxial Growth of Si(111)/Er2O3 (111) Structure on Si(111) by Molecular Beam Epitaxy

The Si overlayers are grown by molecular beam epitaxy on atomically smooth Er2O3 (111) films prepared on Si(111) substrates. Single crystalline Si overlayers are achieved and are evident due to the spot-like reflective high energy electron diffraction (RHEED) patterns and x-ray diffraction patterns. The epitaxial relationship of the Si overlayer along the surface with respect to the orientation of Er2O3 and the Si substrate is as follows: overgrown Si(111)//Er2O3(111)//Si(111). The rough surface of Si overlayers, as identified by both RHEED patterns and atomic force microscopy images, indicates a three-dimensional growth mode. The reason for this is based on the interfacial energy argument. Further growth of Er2O3 films on this rough Si overlayer leads to the polycrystalline nature of the topmost Er2O3 layer.

Structural and microstructural analyses of crystalline Er2O3 high-k films grown on Si (0 0 1) by laser molecular beam epitaxy

Erbium oxide (Er2O3) films are well regarded as being suited for high-k replacement of SiO2 in endeavors to further miniaturize and enhance the performance of microelectronics. Er2O3 films were deposited on Si (001) substrates by laser molecular beam epitaxy. The structures and microstructures of the films and the interfacial layers were characterized by means of X-ray diffraction (XRD) and transmission electron microscopy (TEM). The results from the XRD and selected area electron diffractions of Er2O3 films with thicknesses of 30 and 100nm indicate that the films are polycrystalline, with dominant (111) textures of Er2O3 {111} // Si (001). Amorphous layers dotted with small ordered islands were observed and confirmed to be located at the interfaces between the films and the Si substrates with dark-field image and high-resolution TEM. High-resolution Z-contrast imaging, energy dispersive X-ray spectroscopy and energy-filtered imaging were applied to identify the compositions of the interfacial layers. The salient feature is that the layers consist primarily of Er and O, with a very small amount of Si. This kind of Er–O-based interface layer may play a very important role in the electrical and optical properties of the films.

Study on the Energy Structure of Amorphous Antireflection Er<sub>2</sub>O<sub>3</sub> Films on Si(001) Substrates

Er2O3 films were deposited on Si(001) substrates by radio frequency magnetron technique. X-ray photoelectron spectroscopy, x-ray diffraction and atomic force microscopy show the Er2O3 films obtained are stoichiometric, amorphous, and uniform. The electronic structure is studied which shows a large energy gap value of the Er2O3 film, indicating Er2O3 film could be a promising antireflection coating for solar cells.

Optical Constants of Al-Doped Er<sub>2</sub>O<sub>3</sub> Films Prepared by Radio Frequency Reactive Magnetron Sputtering

Al doped Er2O3 films were deposited on Si(001) substrates by radio frequency magnetron technique. X-ray diffraction and atomic force microscopy show the Al doped Er2O3 films obtained are amorphous and uniform. The optical constants are studied which shows a proper value of refractive index and a lower reflectivity, indicating it could be a usefully material for solar cells.

Amorphous Er2O3 films for antireflection coatings

This paper reports that stoichiometric, amorphous, and uniform Er2O3 films are deposited on Si(001) substrates by a radio frequency magnetron sputtering technique. Ellipsometry measurements show that the refractive index of the Er2O3 films is very close to that of a single layer antireflection coating for a solar cell with an air surrounding medium during its working wavelength. For the 90-nm-thick film, the reflectance has a minimum lower than 3% at the wavelength of 600 nm and the weighted average reflectances (400–1000 nm) is 11.6%. The obtained characteristics indicate that Er2O3 films could be a promising candidate for antireflection coatings in solar cells.

Photoluminescence of erbium in polycrystalline ceramics and in crystalline film of erbium oxide

Structural, optical, and electric properties of Er2O3 films obtained from Er2O3 ceramic target by the method of vacuum electron-beam deposition on sapphire substrates have been investigated. Optical characteristics of the films are studied in the range from UV up to IR using techniques of absorption, reflection, and emission spectroscopy; specific resistance of the obtained films was also measured. After excitation with the radiation of semiconductor diode laser at 980 nm, IR glow has been obtained at room temperature at the wavelength of approximately 1550 nm from Er3+ ions in polycrystalline ceramic target and in crystalline films. In addition, fluorescence was observed, in the visible range of spectrum, from ceramic target; this fluorescence corresponds to two-step mechanism of excitation with frequency up-conversion.

Leakage current mechanisms of ultrathin high-k Er2O3 gate dielectric film

A series of high dielectric material Er2O3 thin films with different thicknesses were deposited on p-type Si (100) substrate by pulse laser deposition at different temperatures. Phase structures of the films were determined by means of X-ray diffraction (XRD) and high resolution transmission electron microscopy (HRTEM). Leakage current density was measured with an HP4142B semiconductor parameter analyzer. The XRD and HRTEM results reveal that Er2O3 thin films deposited below 400 °C are amorphous, while films deposited from 400 to 840 ° are well crystallized with (111)-preferential crystallographic orientation. I-V curves show that, for ultrathin crystalline Er2O3 films, the leakage current density increases by almost one order of magnitude from 6.20 × 10−5 to 6.56 × 10−4 A/cm2, when the film thickness decreases by only 1.9 nm from 5.7 to 3.8 nm. However the leakage current density of ultrathin amorphous Er2O3 films with a thickness of 3.8 nm is only 1.73 × 10−5 A/cm2. Finally, analysis of leakage current density showed that leakage of ultrathin Er2O3 films at high field is mainly caused by Fowler–Nordheim tunneling, and the large leakage of ultrathin crystalline Er2O3 films could arise from impurity defects at the grain boundary.

Annealing effects on the structure and electrical characteristics of amorphous Er2O3 films

Amorphous Er2O3 films are deposited on Si (001) substrates by using reactive evaporation. This paper reports the evolution of the structure, morphology and electrical characteristics with annealing temperatures in an oxygen ambience. X-ray diffraction and high resolution transimission electron microscopy measurement show that the films remain amorphous even after annealing at 700 °C. The capacitance in the accumulation region of Er2O3 films annealed at 450 °C is higher than that of as-deposited films and films annealed at other temperatures. An Er2O3/ErOx/SiOx/Si structure model is proposed to explain the results. The annealed films also exhibit a low leakage current density (around 1.38 × 10−4 A/cm2 at a bias of −1 V) due to the evolution of morphology and composition of the films after they are annealed.

Charge conduction mechanisms of atomic-layer-deposited Er2O3 thin films

The charge transport mechanism through atomic-layer-deposited erbium oxide thin films has been analyzed with current-voltage (I-V) measurements. At low electric field, i.e., below 3 MV/cm, the charge conduction through 10 nm thick Er2O3 films is dominated by Poole–Frenkel electron injection. However, Fowler–Nordheim tunneling of holes also occurs at higher electric fields through the oxide. Various electronic and material parameters such as the trap density, activation energy of the traps, and interface defect density are extracted from the I-V and parallel conductance (GP) measurements as a function of frequency.

Enhanced photoluminescence in [Er2O3/TiO2]m photonic crystals

We survey optical properties of [Er2O3/TiO2]6/Er2O32/[TiO2/Er2O3]6 photonic crystals (PCs) pulsed laser deposited on to the glass substrates. The dispersion relations of refractive indexes and extinction coefficients of the constituent materials were obtained from the comparison of experimental and simulated transmission spectra of single layer Er2O3 and TiO2 reference films. Based on these data several PCs have been designed and grown to match stop band and cavity mode resonance at wavelengths close to the 523 nm Er3+-ion Fraunhofer S43/2 absorption line. Precise control of chemical composition and uniform multilayer thickness enable achievement of superior optical performance of sintered PCs. Obtained dispersion relations were combined with the 2×2 transfer matrix formalism to compute PC transmittance that appeared to be in a good agreement with the experimental spectra. Pumping PCs with 514 nm light source we observed a strong photoluminescence (PL) at 1535 nm. In PC specially designed for the resonance wavelength λres=514 nm, C-band PL intensity experiences fivefold enhancement compared to a single layer Er2O3 film of equivalent thickness.