Amorphous Tantalum Oxide Films Research Articles

Electrochemically Induced Stresses in Amorphous Tantalum Oxide Films

Hydration processes were previously thought to be limited in amorphous tantalum oxide (ATO) capacitors. However, in-situ measurements show that hydration can produce substantial stresses in ATO. These measurements were also used to systematically investigate several important factors during hydration: the ATO thickness, electrolyte pH, annealing, and electrical field variations. Analysis of these data indicates that hydration in aqueous electrolytes is a diffusion limited process with diffusivities of 2–3 (10)−15 cm2/sec. Pulsed electric fields with different strengths were also applied to further elucidate stress contributions from different mechanisms. Heat treatments up to 400°C produce changes in the structure of the ATO that leads to significant variations in the electrochemical hydration behavior.

Preparation and Biocompatibility of Tantalum Oxide Films Containing the Hydroxyl Group

Amorphous Ta-O films were synthesized by reactive pulse unbalanced magnetron sputtering system in this paper. Then the well-crystallized Ta-O films were obtained after they were annealed in vacuum at 800°C for 1h. Hydroxyl group on the surface of amorphous tantalum oxide films was prepared by plasma hydrogenation method. The phase structure was investigated by X-ray diffraction (XRD). The hydroxyl group was characterized using Fourier transform infrared spectroscopy (FTIR). The morphology and growth behavior of the vitro platelet adhesion on the as-deposited, annealed and plasma hydrogenated Ta-O films were analyzed through scanning electron microscope (SEM). The results showed that the quantity of platelet adhered onto the annealed surface were less than as-deposited and hydrogenised films. A new method of preparing hydroxyl group without coupling agents on the inorganic biomaterials has been studied by plasma hydrogenation.

Determining the optical constants of thin oxide films

This paper discusses a technique for determining the dispersion of the optical constants and the thickness of thin, weakly absorbing oxide films from the experimental interference transmission spectra. Formulas and techniques are given for calculating the film parameters, based on a numerical iterative solution of a system of transcendental equations. A mathematical model of the transmission spectrum is obtained by the authors and is used to set up the equations. Examples are considered of determining the optical constants and the thickness of amorphous tantalum oxide films from the transmission spectra in the wavelength region 0.3-1.1 µm.

Intense photoluminescence from amorphous tantalum oxide films

Tantalum oxide films were deposited on silicon substrates at a temperature of ∼450°C by heating a pure tantalum foil in a rough vacuum. The films were amorphous in structure and consisted of fully oxidized Ta2O5 and (TaOx, x<2.5) suboxides. This feature resulted in strong visible light emission from the films further oxidized in the air at temperatures of 200–300°C. The mechanism for this photoluminescence behavior of the amorphous tantalum oxide films was also investigated and discussed. This study suggests that wide-band-gap materials could act as effective visible light emitters and provides a simple route to synthesize such materials.

The proton diffusivity of amorphous tantalum oxide thin films

AbstractProton diffusion in tantalum oxide thin film is of significant interest because of its importance in barrier, sensor, and catalytic‐coating applications. In this study, a novel method based on potential‐pH response measurement was used to determine proton diffusivity of amorphous tantalum oxide thin films. This technique is based on the model of diffusion‐controlled proton transport in the oxide surface, measures the potential‐pH response in a thermostatic measurement set‐up. The proton diffusivity of amorphous tantalum oxide films obtained from this method was 4 × 10–21 cm2/s. The novel method is a relatively simple experimental procedure, which eliminates complications arising from surface‐related effects and/or the presence of hydrogen traps in the metal such as those found in the conventional permeation method. (© 2003 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Surface Roughness Evolution in Amorphous Tantalum Oxide Films Deposited by Pulsed Reactive Sputtering

ABSTRACTThe growth front roughness of Ta2O5 amorphous films grown by pulsed plasma d.c. reactive sputtering has been investigated using atomic force microscopy. Film deposition during reactive sputter deposition is explained based on dynamic scaling hypothesis in which both time and space scaling are considered simultaneously. The interface width w increases as a power law with deposition time t, w ∼ tβ, with β = 0.45 ± 0.03. The lateral correlation length ξ grows as ξ ∼ t1/z, with 1/z = 0.61 ± 0.07. The roughness exponent extracted from the slope of height-height correlation analysis is α = 0.79 ± 0.04. The results are similar to that obtained by sputtering of elemental materials, and do not fit to any of the presently known growth models. Monte Carlo simulations were carried out based on a recently developed re-emission model, where incident flux distribution, shadowing, sticking coefficient, and surface diffusion mechanisms were accounted for in the deposition process. An important finding is that sticking coefficient must be less than unity to obtain the observed β value (∼0.45).

Li Conduction in Sputtered Amorphous Ta2 O 5

Electron and Li ion conducting properties of room temperature sputtered amorphous tantalum oxide films were studied in order to evaluate the feasibility of using in electrochromic device applications. The films were investigated using the galvanostatic intermittent titration technique, impedance spectroscopy, and isothermal transient ionic current measurements. It was found that the met two out of three requirements posed on a Li ion conductor in a based electrochromic device. There was a negligible intercalation in the potential window used in -based electrochromic devices (above 2.4-2.5 V vs. Furthermore, in this potential region, the chemical diffusion coefficient for Li was larger than the corresponding quantity in However, there was a nonzero electron conductivity in the films, not observed in the chemical vapor deposition-made investigated earlier. Still, the ionic conductivity was approximately one order of magnitude larger than the electronic one. © 2001 The Electrochemical Society. All rights reserved.

High frequency response of amorphous tantalum oxide thin films

Amorphous tantalum oxide films were deposited using a pulsed dc reactive magnetron sputtering technique at low temperature (/spl les/200/spl deg/C). A test vehicle (metal-insulator-metal structure) was designed and fabricated for the high frequency characterization of the dielectric thin film. The dielectric constant and loss tangent of the amorphous tantalum oxide thin film were measured using dc, time domain reflectometry (TDR), and network analyzer up to 10 GHz. The measured dielectric constant and loss tangent was 22 and 0.007, respectively from 1 KHz to 10 GHz. The high frequency properties of the amorphous tantalum oxide thin film show little dispersion up to 10 GHz. However, the resonance oscillation due to the parasitics is evident between 10 GHz and 40 GHz and depends on the capacitor area. Modeling of the equivalent circuits would allow us to identify the parasitic components and their effects on the measured scattering parameters.

MOCVD of High-K Dielectrics and Conductive Metal Nitride Thin Films

AbstractA known liquid mixture of [(CH3CH2)2N]3 Ta=NCH2CH3 and [(CH3CH2)2N]3Ta[ð2-CH3CH2N=CH(CH3)] was studied to deposit Ta2O5 and TaN thin films by CVD. Films were deposited at temperatures below 400°C using oxygen for oxide and ammonia for nitride, respectively. XRD analysis revealed that as-deposited amorphous tantalum oxide films were converted to hexagonal Ta2O5 after annealing under oxygen, while tantalum nitride thin films contained cubic TaN as deposited. The low viscosity, thermal stability, and sufficient volatility of the precursor allows direct liquid injection to deliver the precursor, which results in high deposition rate and uniformity of the deposited films.

Tantalum oxide film deposition by laser ablation

Amorphous tantalum oxide films have been prepared by the ArF excimer laser ablation of Ta 2O 5 in the presence of O 2. The deposition rate increases linearly with an increase in the laser energy. The substrate temperature does not influence the deposition rate at an O 2 flow rate of 5 sccm. But at an O 2 flow rate of 100 sccm, the deposition rate decreases strikingly with the substrate temperature. The refractive indices to the films tend to be low under mild deposition conditions.

Deposition of tantalum oxide films by ArF excimer laser chemical vapour deposition

Amorphous tantalum oxide films have been prepared by the ArF excimer laser photodissociation of Ta(OC 2H 5) 5 in the presence of N 2O. Film formation is observed at substrate temperatures above 150 °C. The film thickness reaches a maximum at substrate temperatures around 200 °C, and then it has a tendency to decrease slightly with temperature. The refractive indices of the films change from 1.85 to 2.30 when the substrate temperature is raised from 150 °C to 300 °C. O( 1D) atoms produced from photolysis of N 2O contribute significantly to the formation of tantalum oxide films.

The crystallisation of thin amorphous tantalum oxide films heated in air or vacuo, and the structure of the crystalline oxide

The crystallisation of thin amorphous tantalum oxide films heated in air or vacuo, and the structure of the crystalline oxide