Plasma Enhanced Atomic Layer Deposition of Tantalum (V) Oxide

Abstract

The tantalum oxide thin films are promising materials for various applications: as coatings in optical devices, as dielectric layers for micro and nanoelectronics, and for thin-films solid-state lithium-ion batteries (SSLIBs). This article is dedicated to the Ta-O thin-film system synthesis by the atomic layer deposition (ALD) which allows to deposit high quality films and coatings with excellent uniformity and conformality. Tantalum (V) ethoxide (Ta(OEt)₅) and remote oxygen plasma were used as tantalum-containing reagent and oxidizing co-reagent, respectively. The influence of deposition parameters (reactor and evaporator temperature, pulse and purge times) on the growth rate were studied. The thickness of the films were measured by spectroscopic ellipsometry, scanning electron microscopy and X-ray reflectometry. The temperature range of the ALD window was 250–300 °C, the growth per cycle was about 0.05 nm/cycle. Different morphology of films deposited on silicon and stainless steel was found. According to the X-ray diffraction data, the as-prepared films were amorphous. But the heat treatment study shows crystallization at 800 °C with the formation of the polycrystalline Ta₂O₅ phase with a rhombic structural type (Pmm2). The results of the X-ray reflectometry show the Ta-O films’ density is 7.98 g/cm³, which is close to the density of crystalline Ta₂O₅ of the rhombic structure (8.18 g/cm³). The obtained thin films have a low roughness and high uniformity. The chemical composition of the surface and bulk of Ta-O coatings was studied by X-ray photoelectron spectroscopy and energy-dispersive X-ray spectroscopy. Surface of the films contain Ta₂O₅ and some carbon contamination, but the bulk of the films does not contain carbon and any precursor residues. Cyclic voltammetry (CVA) showed that there is no current increase for tantalum (V) oxide in a potential window of 3–4.2 V and has prospects of use as protective coatings for cathode materials of SSLIBs.

1. Introduction

Thin films of tantalum oxide are used for antireflection coatings for strongly curved glass lenses [1], as dielectric layers for micro and nanoelectronics [2]. They also have great prospects for solid-state lithium-ion batteries (SSLIB) [2] as a solid-state electrolyte and functional coatings for cathodes.

It is important to use low deposition temperatures to prevent structural and chemical changes in the surface of the coated material while obtaining films for previously mentioned purposes. The ability to cover 3D-oriented surfaces with precise thickness control is also important. All these tasks can be solved by the Atomic Layer Deposition (ALD) [3]. The essence of the method lies in the chemical interaction of reagent vapors with the substrate and subsequent purging with an inert gas. Due to its peculiarities, the method makes it possible to obtain uniform films and high-quality coatings on surfaces of both flat and bulk three-dimensional substrates. It allows controlling the thickness of the films with a high accuracy, and also provides good reproducibility of the resulting structures characteristics [4].

Both inorganic (TaF₅, TaCl₅), and a number of organometallic precursors (TBTEMT, Ta(NtBu)Me(dmaema)₂, (t-BuN)(Et₂N)₂CpTa, TBTMET, TBTDET, TAIMATA, PDMAT, Ta(OEt)₅) are used to obtain tantalum oxides by the ALD (

Table 1. Comparative characteristics of the tantalum binary compounds obtaining processes by the ALD method.

Precursor A CAS No	Precursor B	Reagent Temperature °C	Reactor Temperature °C	Substrate	Growth Per Cycle (GPC) nm/cycle	Chemical Compound	Ref.
Ta(OEt)5 6074-84-6	O2 plasma	110	220	Si, TiN	0.09	Ta2O5	[7]
	O2 plasma	-	260	Si	0.075	Ta2O5	[8]
	H2O2	185	300	Si	0.049	Ta2O5	[1]
	H2O	70	200–350	Si	0.040 ± 0.001	Ta2O5	[9]
	H2O	190	225	Si	0.05	Ta2O5	[10]
	O2 plasma, H2O	-	300	SiO2, Si	-	Ta2O5	[11]
	H2O	-	250	SiO2, Si	-	Ta2O5	[12]
	H2, H2O	-	300	Si, TiN	-	Ta2O5	[13]
	H2	-	300	Si	0.052	Ta2O5	[14]
	H2O	-	250	Si	-	Ta2O5	[15]
	O3	95	300	SiO2	0.035	Ta2O5	[16]
	O3	160	100–400	TiN/SiO2	0.095–0.113	Ta2O5	[17]
TBTEMT Ta[N(CH3)(C2H5)]3[=NC(CH3)3] 511292-99-2	H2O	90	210	Al2O3, SiO2	0.051	Ta2O5	[18]
	H2, Ar:H2	-	150–350	Si	-	TaN	[19]
TaF5 7783-71-3	H2, Ar plasma	70	350	-	0.035	TaN	[20]
	Mixed H2 + Ar + N2	70	350	SiO2, Si	0.041	TaN	[21]
TBTMET, TBTDMT, Ta[N(CH3)2]3[=NC(CH3)3] 69039-11-8	O2 plasma	60	250	Si	0.01	Ta2O5	[22]
	N2:H2, NH3, O2	-	300–400	SiO2, Si	-	Ta2O5	[23]
	O2 plasma	55	300	Si	0.11	Ta2O5	[24]
TBTDET, Ta[N(C2H5)2]3[=NC(CH3)3] 169896-41-7	H2O	100	150–350	Si	0.077	Ta2O5	[25]
TAIMATA 629654-53-1	N2+H2 plasma	60	230	SiO2, Si(100)	0.13	TaN	[26]
	Ar + H2	-	300	SiO2, Si(100), HfO2	-	TaC, TaN	[27]
	Ar+H2	70	350	SiO2, Si	0.09–0.1	TaN	[28]
	H2	60	230	SiO2, Si	0.13	TaN, TaC	[29]
	H2O	-	200	Si	-	TaN	[30]
PDMAT, Ta[N(CH3)2]5 19824-59-0	O2 plasma	65	100–225	Si(100)	0.08–0.087	Ta2O5	[31]
(t-BuN)(Et2N)2CpTa 852212-55-6	H2O	-	200	-	-	Ta2O5	[32]
Ta(NtBu)Me(dmaema)2	NH3 plasma	100–120	200–250	SiO2, Si	0.062	TaN	[33]
TaCl5 7721-01-9	H2O	90	250–450	Si	0.011–0.065	Ta2O5	[6]
	H2:N2	90	300	Si(001), SiO2	0.024	TaN	[34]
	H2:N2	-	300	Si	0.008–0.01	TaN	[35]
	H2:N2	100	100–400	Si(001), SiO2	0.024	TaN	[36]
	H2:N2	110	300	SiO2	-	TaN	[37]
	Atomic H	100	25–300	SiO2, Si	0.008	Ta	[38]
	Atomic H	100–120	25–400	Si	0.016–0.16	Ta	[2]
	Atomic H	100	400	Si(001), SiO2	0.008	Ta	[39]

). The metal halide precursors have high vapor pressure are stable, reactive and therefore widely used. But the use such inorganic reagents lead to formation of corrosive byproducts (e.g., HCl) which may cause possible etching of growing film and damage hardware of the ALD tools. Alkylamides such as (t-BuN)(Et₂N)₂CpTa, TBTEMT, TBTMET, PDMAT have limited thermal stability and low reactivity which can be improved by increasing the ALD temperature, but this can lead to thermal decomposition of the metalorganic precursors. Tantalum (V) ethoxide (Ta(OEt)₅) is a liquid with a saturated vapor pressure high enough for ALD processes (6 mm Hg at 190 °C) [5]. The reagent is relatively stable during storage and it does not decompose in the ALD “window” temperature range [6] and can be successful used for the ALD. To date, a number of researchers have shown that both water and oxygen plasma can be successfully used as co-reagents for Ta(OEt)₅ (Table 1). However, despite the existence of a number of studies, the features of the growth, structure, composition and morphology of tantalum oxide films using Ta(OEt)₅ and remote oxygen plasma have not been studied in detail.

This work is devoted to studying the ALD growth parameters of tantalum (V) oxide thin films using tantalum (V) ethoxide and remote oxygen plasma by different methods. The chemical composition at the surface and in-depth, structure (phase composition, thin films density, roughness), the morphology of Ta-O thin films on the silicon and stainless steel substrates were studied. The electrochemical performance is provided by cyclic voltammetry.

2. Materials and Methods

Ta(OEt)₅ (Sigma Aldrich, 99.98% trace metal basis) was used to obtain tantalum ox-ide films on a Picosun R-150 set up in the reactor temperature range from 225 to 350 °C. Ta(OEt)5 was stored in a stainless steel bottle (PicohotTM 200, Picosun Oy, Espoo, Finland) and heated during synthesis to 70, 90, 110, 160, and 190 °C. The pulse time was varied from 0.5 s to 2 s, and purge time was changed from 5 s to 15 s. At an inert nitrogen purge, the gas pressure of 8–12 hPa is combined with vacuum pumping. The number of cycles for the samples ranged from 50 to 1000. Remote oxygen plasma was used as a co-reagent (oxidizer). Plasma power was 3000 W, and the frequency was 1.9–3.2 MHz. The total plasma pulse time was 19.5 s. First, Ar purge was carried out for 0.5 s at a flow rate of 40 sccm, Ar and O₂ plasma purge was carried out for 14 s at a flow rate of 90 sccm. And the last part was Ar purge for 5 s at a flow rate flow 40 sccm. Thus, the number of cycles for the samples ranged from 50 to 1000.

Monocrystalline silicon substrates (surface orientation (100), 40 × 40 mm, TelecomSTV Co., Ltd., Zelenograd, Russia) and stainless-steel disks (316SS, 16 mm diameter, Tob New Energy Technology Co., Ltd., Xiamen, China) were used in experiments as substrates for the ALD. Before deposition, the stainless-steel substrates were cleaned in an ultrasonic bath filled with acetone and then deionized water for 5 min.

Spectroscopic ellipsometry (SE) [40,41] was used to determine the thickness of the resulting films and to calculate the growth per cycle (GPC). Ellipsometric measurements were performed with a spectroscopic ellipsometer Ellips-1891 SAG (CNT, Novosibirsk, Russia) at wavelengths in the range λ = 250–900 nm (photon energy E = 1.4–5.0 eV) and light incidence angle φ = 70° relative to the normal to the surface, from an external medium (air). Spectral dependences of both ellipsometric angles ψ and Δ were measured simultaneously. The probe spot diameter was 3 mm. The calculations were carried out using the procedure for finding the model (Supplementary file) coefficients and film thickness using the software supplied with the ellipsometer. The thickness measurement error was ±1 nm.

X-ray reflectometry (XRR) and X-ray diffraction (XRD) studies were performed on a Bruker D8 DISCOVER diffractometer (Bruker, Billerica, MA, USA), Cu-Kα = 1.5406 Å. Grazing incidence XRD (GIXRD) modes, that are surface sensitive, were used for XRD measurements using a 2θ range of 20–65° in 0.1° steps and 1 s exposure at each step. The angle of incidence of the primary X-ray beam was 0.7°. XRR measurements were carried out over an angular range of 0.2–5° (0.01° step) using symmetric scattering geometry. The results were processed by the Rietveld method using the TOPAS software package (version 5, Bruker, Billerica, MA, USA) and LEPTOS (version 7.7, Bruker, Billerica, MA, USA) for XRD and XRR, respectively. The approximate thickness, density, and the number of coatings and instrumental parameters (radiation wavelength, goniometer radius, slit width, etc.) were set using the LEPTOS software. Based on these data, the theoretical curve was modeled and fitted to best match with experimental data using the simplex method by varying the characteristics of the samples (roughness, thickness, and density). The χ² value for the modeled curve was 8.080 × 10⁻³.

X-ray photoelectron spectra (XPS) were obtained on an Escalab 250Xi spectrometer (Thermo Fisher Scientific, Waltham, MA, USA). To obtain information about inner layers of the deposited film the Ar+ sputtering (500 eV for 90 s) was performed. The samples were excited by the X-ray radiation Al-Kα (1486.7 eV) at a pressure of 7 × 10⁻⁸ Pa.

The scanning electron micrographs of flat and cross-sections were obtained by a Supra 55 VP scanning electron microscope (SEM, Zeiss, Oberkochen, Germany) with a Gemini-I column and a field emission cathode. The spatial resolution was about 1.3 nm at an accelerating voltage of 3 kV. A total of 3 randomly selected positions on the sample surface were examined. An Everhart-Thornley and an InLens secondary electron detectors were used for SEM studies. Energy Dispersive X-ray (EDX) analysis was performed using an INCA X-Max system (Oxford Instruments, High Wycombe, UK) mounted on a Supra 55 VP SEM.

Stainless steel plates (SS) with deposited films were used for electrochemical studies. Lithium foil, polyolefin porous film 2325 (Celgard, Charlotte, NC, USA), and TC-E918 (Tinci, Guangzhou, China) were used as a counter electrode, a separator and an electrolyte, respectively. The composition TC-E918 was a 1M solution of LiPF₆ in a mixture of organic carbonates (ethylene carbonate, propylene carbonate, diethyl carbonate, ethyl methyl carbonate, vinyl carbonate). The coin cells (CR2032) were assembled in OMNI-LAB (VAC) glove box under argon atmosphere. Cyclic voltammetry (CV) was performed using a PGSTAT302N + potentiostat (Autolab, Utrecht, The Netherlands) in the range 0.01–4.30 V with a scan rate of 0.5 mV/s.

3. Results and Discussions

3.1. Atomic Layer Deposition of Ta-O Thin Films

To determine the optimal conditions for the tantalum oxide growth, the effect of the Ta(OEt)₅ evaporator temperature, the time of pulsing, purging and the reactor temperature on the GPC were studied (

Table 2. Conditions of the ALD process for obtaining the Ta-O system.

No	Reagent Temperature °C	Time Pulse/Purge, s	Reactor Temperature °C	Number of Cycles	GPC nm/cycle
Ta-O_1	70	1/5	300	500	0.0041
Ta-O_2	90	1/5	300	500	0.0057
Ta-O_3	110	1/5	300	500	0.0093
Ta-O_4	160	1/5	300	500	0.0433
Ta-O_5	190	1/5	300	500	0.0486
Ta-O_6	190	1.5/5	300	1000	0.0463
Ta-O_7	190	0.5/5	300	500	0.0426
Ta-O_8	190	2/5	300	500	0.0464
Ta-O_9	190	1/10	300	500	0.0439
Ta-O_10	190	1/15	300	500	0.0472
Ta-O_11	190	1.5/10	300	500	0.0501
Ta-O_12	190	1/5	225	500	0.0547
Ta-O_13	190	1/5	250	500	0.0502
Ta-O_14	190	1/5	350	500	0.0467
Ta-O_15	190	1/5	300	50	0.0780
Ta-O_16	190	1/5	300	100	0.0600
Ta-O_17	190	1/5	300	200	0.0505

).

There was a low growth per cycle (less than 0.01 nm/cycle) at the evaporator temperatures from 70 °C to 110 °C, indicating that the evaporator temperature is insufficient for the required amount of the reagent enters the reactor (Figure 1a). At 160 °C and 190 °C, the average growth per cycle increases up to 0.043–0.049 nm/cycle and begin to stabilize. The further increasing temperature is not technically possible because of equipment limitations. Thus, it is necessary to heat the evaporator to at least 190 °C to carry out the tantalum oxide synthesis.

The dependences of the average growth per cycle from the Ta(OEt)₅ pulse time were studied to determine the reactor filling time required to reach saturation. The experiments were carried out at a constant reactor temperature (300 °C) and purging times (after Ta(OEt)₅ pulse in 5 s, after plasma treatment in 15 s). With an increase of the Ta(OEt)₅ pulse duration from 0.5 to 1.0 s, the value of the average growth per cycle augments from 0.042 to 0.049 nm/cycle, and after subsequent pulse time increase GPC does not grow (Figure 1b). Further increases pulse up to 2 s resulted in a slight decrease in the average growth per cycle. Thus, the saturation of the substrate precursor vapors under synthesis conditions can be achieved with a Ta(OEt)₅ pulse time of more than 1.0 s.

To determine the effect of purge duration two series of samples were prepared with 1.0 s and 1.5 s of reactor filling time of Ta(OEt)₅ were chosen (Figure 1c). The purge duration for both series of samples was set to 5 s, 10 s, 15 s. For both series of samples, the average growth rate was almost the same. Thus, neither adsorption time nor desorption time doesn’t influence on the growth rate. We can assume that all available functional groups react during adsorption carried out during 1 s. And 5 s is sufficient to eliminate all excess of Ta(OEt)₅ adsorbed during less or equal 1.5 s.

The average growth per cycle dependences on the reactor temperature were studied to determine the temperature window of the synthesis (Figure 1d). With an increase of the reactor temperature from 225 °C to 350 °C, the average growth per cycle value decreases from 0.055 to 0.047 nm/cycle. It was determined that the largest growth per cycle was at 225 °C (0.055 nm/cycle). The high average growth per cycle value is probably a consequence of the precursor condensation on the substrate surface due to the relatively low reactor temperature and the small difference between the temperatures in the Ta(OEt)₅ evaporator and the reactor. The average growth per cycle values decreases to 0.049–0.050 nm/cycle in the 250 °C. After which in the temperature range of 250–300 °C remains close to constant. The growth per cycle decreases with an increase in temperature, which may be caused by a decrease in the number of functional groups.

The interval in the temperature range 250–300 °C can be considered as a “synthesis window” for ALD processes using Ta(OEt)₅ and oxygen plasma because of the constant growth rate (0.049–0.050 nm/cycle). The linear dependence of the tantalum oxide layer thickness on the number of ALD cycles indicates the absence of nucleation growth effects and the possibility of the film thickness precise control (Figure 1d inset). The obtained growth per cycle values are less than GPC showed in [8] (0.075 nm/cycle), where Ta(OEt)₅ and oxygen plasma were used as reagents. However, they are very close to the growth per cycle values (0.049 nm/cycle) obtained with water as a co-reagent at a temperature of 300 °C (Table 1). The slight difference between the experimental and published data is probably due to the design differences of the used setups, the thickness measurement techniques.

3.2. Morphology of Films on Si

Top view and cross-sectional images of Ta-O films on a Si substrate, obtained using scanning electron microscopy, are shown in Figure 2. The resulting tantalum oxide films were smooth and homogeneous, without visible defects and inclusions. The average thickness sample of Ta O_6 is about 46.3 nm. The smoothness of the film indicates the absence of nucleation effects during synthesis in the ALD “window”.

3.3. Chemical Composition of the Films

The EDX analysis was carried out to determine the chemical composition. It showed that the atomic concentration ratio of Ta:O in the film (with a thickness of 46.3 nm) is approximately 1:2.7. The observed ratio indicates the formation of tantalum (V) oxide during the synthesis. It can be concluded that there is no reduction of tantalum during the synthesis since Ta(OEt)₅ was used for the deposition. The slight excess of the oxygen atomic concentration over ratios 2:5 may be due to a natural oxide layer on the silicon substrate surface.

A decrease in the energy of exciting radiation during the EDX makes it possible to reduce the depth of the analyzed region. Considering the small thickness of the analyzed coatings (3.9–46.3 nm), the minimum accelerating voltage of 3 kV was chosen to study the samples.

A clear signal from tantalum is observed even on the X-ray spectra with a coating thickness of 6 nm (Figure 3). As the film thickness increases, the main peak of tantalum (M-series) shifts to the low-energy side due to the decrease in the effect of the silicon substrate. The intensity of the peaks in the spectral regions of 1.335 and 1.96 keV also increases. The intensity of the maxima corresponding to silicon atoms decreases.

A sample of tantalum oxide (Ta-O_11), obtained at the reactor temperature of 300 °C during 500 cycles, was investigated by the XPS method for a detailed study of the chemical composition. Both the external surface and the coating volume were studied after etching the surface layer with argon ions. Tantalum, oxygen, and carbon were found on the sample surface (

Table 3. Atomic ratios of elements before and after etching according to XPS data.

Spectra	Before Etching, at. %	After Etching, at. %
O1s	52.46	48.89
Ta4f	20.64	51.11
C1s	26.90	0

). After the surface layer etching, carbon peaks in the spectrum are no longer observed, indicating that there is no carbon in the coating. Presumably, the sample surface is contaminated with organic and inorganic carbon compounds deposited from the air.

Based on the C1s level peak position and shape, carbon on the sample surface is predominantly in the C–C, C–H state (Figure 4). In addition, there is a small amount of C–OH. There are no compounds with C=O bonds, COOH, and carbonates on the surface. The O1s spectra of the surface exhibit an intense peak corresponding to Ta₂O₅ and a small shoulder corresponding to compounds with C–O bonds. This peak shifts toward the higher energies during etching. According to the fact that no carbon was found in the etched sample and it cannot contain oxygen-containing phases C–O and C=O, the shift is caused by the reduction of Ta₂O₅ to intermediate oxide phases TaO, Ta₂O₃.

According to the XPS spectra of the Ta4f level, Ta₂O₅ is located on the sample surface. The Ta to O 2:5 ratio also corresponds to this compound and coincides with the data obtained by the EDX. The peaks shift to the lower energies after etching, their maxima correspond to the TaO compound, and the Ta to O ratio becomes 1:1. According to the XRD data, the film volume consists of Ta₂O₅. Judging by that, it is likely that TaO was a result of the Ta⁵⁺ reduction upon bombardment with the argon ions.

3.4. Crystal Structure

The XRD of the sample showed that the resulting films in ALD “window” are amorphous, Figure 5. In the range from 20 to 40° 2θ, a diffuse halo is noticeable. It signifies the crystallization onset of the tantalum (V) oxide phase. The fact that there are no metallic tantalum peaks indicates its absence in the film composition. It correlates with the data obtained by the XPS, in the spectra, the maxima corresponding to tantalum in the zero-oxidation state were not found. After heat treatment (HT) at 800 °C for 15 min, intense peaks appeared in the diffractogram at 23, 29, 37.5, 45, 47, 51, and 56°, corresponding to the crystalline phase of Ta₂O₅ (orthorhombic, Pmm2). According to the ellipsometry data, the films’ thickness before and after HT is not changed within the measurement accuracy (Supplementary file, Figure S3) thus we can assume that remains stable and cover substrate even after calcination at high temperature.

The X-ray reflectometry of the sample before HT (Figure 6) showed that the films have a uniform density equal to 7.98 g/cm³, close to 7.96 g/cm³ [42], and close to the crystal Ta₂O₅ density of 8.18 g/cm³ [43]. The lower density is due to the amorphous state of the tantalum (V) oxide. According to the XRR data, the films have low roughness, which is also confirmed by the SEM photography. The film thickness was 46.8 nm, close to the data obtained by spectral ellipsometry (46.3 nm).

3.5. SEM of Tantalum Oxide Coated Steel

The surface of coatings deposited on the steel substrates differs from the sample deposited on silicon. The densely spaced particles ranging in size from several tens to one hundred nanometers (Figure 7) are presented on the surface. The average thickness of Ta-O_6 coating on the stainless steel is about 61.4 nm. The difference in the morphology of coatings on silicon and steel may be due to different surface roughness and functional groups of a different nature. The average growth per cycle is 0.0614 nm/cycle, that more GPC on the silicon surface (0.0463 nm/cycle).

3.6. Electrochemical Studies

Cyclic voltammetry (CV) was carried out for samples of amorphous tantalum (V) oxide on steel substrates (TaO_9). The results of 5 cycles of CV are shown in Figure 8.

During CV scans of nanofilms, a pronounced current increase appeared in the 3.0–0.1 V range. It was caused by conventional reactions and lithiation of Ta-O nanofilms [44], and a partial reduction in organic solvents (ethylene carbonate, propylene carbonate, diethyl carbonate, ethyl methyl carbonate) and functional additives (vinylene carbonate) of electrolytes with the formation of a gel-like solid electrolyte interface (SEI) film on the active layer [45]. However, there is no current amplification in the cathode potential range (4.3–3.0 V) (inset in Figure 8). Thus, the investigated coatings do not affect the electrochemical capacity in the region of cathodic potentials and do not interact with the electrolyte. In the works, the stabilization of Ni-rich cathodes is shown both when doping with tantalum [46] and when applying tantalum-containing oxide coatings [47]. Thus, they can be used as protective coatings for cathode materials [2].

4. Conclusions

As a result, the optimal conditions for the production of tantalum (V) oxide nanofilms by the ALD were determined. The temperature effect of the container’s evaporator with the reagent Ta(OEt)₅, the time of its pulsing, purging, and the reactor temperature on the growth per cycle were studied. The results showed that to achieve the ALD growth of the substrate surface with Ta(OEt)₅ vapors, an evaporator temperature above 190 °C and an pulse time of at least 1 s are required. A 5 s purge is sufficient to remove excess reagent and reaction products. The ALD temperature window is 250–300 °C, with an average growth per cycle at 0.043–0.050 nm/cycle.

The study of the obtained nanofilms by XPS and EDX showed that the films contain no unreacted carbon-containing residues of the Ta(OEt)₅ precursor, and the stoichiometric ratio of tantalum and oxygen is close to Ta₂O₅. The nanofilms deposited on Si substrates have homogeneous morphology, low roughness, and the density (7.98 g/cm³) are close to bulk tantalum (V) oxide (8.18 g/cm³). The nanofilms obtained at 300 °C with a thickness of 46–47 nm are X-ray amorphous. However, they crystallize upon annealing at 800 °C with the formation of orthorhombic Ta₂O₅.

The average growth per cycle of nanofilms on stainless steel is 0.0614 nm/cycle, which is more than GPC on the silicon surface (0.0463 nm/cycle). This nanofilms are not homogenous and consist of densely spaced particles ranging from several tens to one hundred nanometers.

The obtained cyclic voltammograms analysis of the nanofilms deposited on steel substrates showed that the coatings in the cathode potential range (4.3–3.0 V) do not interact with the electrolyte and do not contribute to the electrochemical capacity.