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1.
The electrical as well as the structural properties of La2O3 thin films on TiN substrates were investigated. Amorphous stoichiometric La2O3 thin films were grown at 300 °C via atomic layer deposition technique by using lanthanum 2,2,6,6-tetramethyl-3,5-heptanedione [La(TMHD)3] and H2O as precursors. Post-annealing of the grown film induced dramatic changes in structural and the electrical properties. Crystalline phases of the La2O3 film emerged with the increase of the post-annealing temperature. Metal-insulator-metal (MIM) capacitor was fabricated to measure the electrical properties of the grown film. The dielectric constant of the La2O3 thin films increased with annealing temperature to reach the value of 17.3 at 500 °C. The leakage current density of the film post-annealed at 400 °C was estimated to be 2.78 × 10−10 and 2.1 × 10−8 A/cm2 at ±1 V, respectively.  相似文献   

2.
TiO2 thick films deposited on macroporous reticulated Al2O3 foams with pore size of 10 ppi and 15 ppi were prepared using dip coating from slurries of Aeroxide® P25 nanopowder and precipitated titania. All prepared films have sufficiently good adhesion to the surface of the substrate also in case of strongly cracked films. No measurable release of deposited TiO2 after repeated photocatalytic cycles was observed. The photocatalytic activity was characterized as the rate of mineralization of aqueous phenol solution under irradiation of UVA light by TOC technique. The best activity was obtained with Aeroxide® P25 coated Al2O3 foam with the pore size of 10 ppi, annealed at 600 °C. The optimal annealing temperature for preparation of films from precipitated titania could be determined at 700 °C. Films prepared by sol-gel deposition technique were considerably thinner compared to coatings made of suspensions and their photocatalytic activity was significantly smaller.  相似文献   

3.
Indium tin oxide (ITO) and titanium dioxide (TiO2) single layer and double layer ITO/TiO2 films were prepared using reactive pulsed laser ablation deposition (RPLAD) with an ArF excimer laser for applications in dye-sensitized solar cells (DSSCs). The films were deposited on SiO2 substrates either at room temperatures (RT) or heated to 200-400 °C. Under optimized conditions, transmission of ITO films in the visible (vis) range was above 89% for films produced at RT and 93% for the ones deposited at higher temperatures. Increasing the substrate temperature from RT to 400 °C enhances the transmission of TiO2 films in the vis-NIR from about 70% to 92%. High transmission (≈90%) was observed for the double layer ITO/TiO2 with a transmission cut-off above 900 nm. From the transmission data, the energies gaps (Eg), as well as the refractive indexes (n) for the films were estimated. n ≈ 2.03 and 2.04, respectively for ITO films and TiO2 film deposited at 400 °C in the visible region. Post-annealing of the TiO2 films for 3 h at 300 and 500 °C was performed to enhance n. The refractive index of the TiO2 films increases with the post-annealing temperature. The direct band gap is 3.6, 3.74 and 3.82 eV for ITO films deposited at RT, 200, and 400 °C, respectively. The TiO2 films present a direct band gap of 3.51 and 3.37 eV for as deposited TiO2 films and when annealed at 400 °C, respectively. There is a shift of about 0.1 eV between ITO and ITO/TiO2 films deposited at 200 °C. The shift decreases by half when the TiO2 film was deposited at 400 °C. Post-annealing was also performed on double layer ITO/TiO2.  相似文献   

4.
The article reports on correlations between the process parameters of reactive pulsed dc magnetron sputtering, physical properties and the photocatalytic activity (PCA) of TiO2 films sputtered at substrate surface temperature Tsurf ≤ 180 °C. Films were deposited using a dual magnetron system equipped with Ti (Ø50 mm) targets in Ar + O2 atmosphere in oxide mode of sputtering. The TiO2 films with highly photoactive anatase phase were prepared without a post-deposition thermal annealing. The decomposition rate of the acid orange 7 (AO7) solution during the photoactivation of the TiO2 film with UV light was used for characterization of the film PCA. It was found that (i) the partial pressure of oxygen pO2 and the total sputtering gas pressure pT are the key deposition parameters influencing the TiO2 film phase composition that directly affects its PCA, (ii) the structure of sputtered TiO2 films varies along the growth direction from the film/substrate interface to the film surface, (iii) ∼500 nm thick anatase TiO2 films with high PCA were prepared and (iv) the structure of sputtered TiO2 films is not affected by the substrate surface temperature Tsurf when Tsurf < 180 °C. The interruption of the sputtering process and deposition in long (tens of minutes) pulses alternating with cooling pauses has no effect on the structure and the PCA of TiO2 films and results in a decrease of maximum value of Tsurf necessary for the creation of nanocrystalline nc-TiO2 film. It was demonstrated that crystalline TiO2 films with high PCA can be sputtered at Tsurf ≤ 130 °C. Based on obtained results a phase zone model of TiO2 films was developed.  相似文献   

5.
The layered perovskite type oxides, K2La2Ti3O10 and zinc(Zn)-doped K2La2Ti3O10 were prepared by sol-gel method and were characterized by power X-ray diffraction, UV-vis diffuse reflectance and X-ray photoelectron spectroscopy. The photocatalytic activity for water splitting of the catalyst powders was investigated with I as electron donor under ultraviolet and visible light irradiation respectively. The electronic structure of the powders has been analyzed by the first principles calculation, which reveals the photo responses in the visible region and the improvement of the photocatalytic activity of K2La2Ti3O10. Conclusions were made that zinc(Zn)-doped K2La2Ti3O10 exhibited higher reactivity for hydrogen production. When I was used as electron donor, the optimum doping concentration of zinc(Zn) was found to be 0.015:1 (nZn:nTi). The average hydrogen production rates were 126.6 μmol/(gcat h) under ultraviolet irradiation and 55.5 μmol/(gcat h) under visible light irradiation which were raised by 131% and 251% compared with undoped K2La2Ti3O10 photocatalyst, respectively.  相似文献   

6.
La-doped HfO2 gate dielectric thin films have been deposited on Si substrates using La(acac)3 and Hf(acac)4 (acac = 2,4-pentanedionate) mixing sources by low-pressure metal-organic chemical vapor deposition (MOCVD). The structure, thermal stability, and electrical properties of La-doped HfO2 films have been investigated. Inductive coupled plasma analyses confirm that the La content ranging from 1 to 5 mol% is involved in the films. The films show smaller roughness of ∼0.5 nm and improved thermal stability up to 750 °C. The La-doped HfO2 films on Pt-coated Si and fused quartz substrates have an intrinsic dielectric constant of ∼28 at 1 MHz and a band gap of 5.6 eV, respectively. X-ray photoelectron spectroscopy analyses reveal that the interfacial layer is Hf-based silicate. The reliable value of equivalent oxide thickness (EOT) around 1.2 nm has been obtained, but with a large leakage current density of 3 A/cm2 at Vg = 1V + Vfb. MOCVD-derived La-doped HfO2 is demonstrated to be a potential high-k gate dielectric film for next generation metal oxide semiconductor field effect transistor applications.  相似文献   

7.
Anatase thin films (<200 nm in thickness) embedding Degussa P25 TiO2 were prepared by sol-gel method. TiO2-anatase thin films were deposited on a fiberglass substrate and then ground to obtain glass microrods containing the composite films. The film structure was characterized using Raman spectroscopy, atomic absorption and UV-vis spectrophotometry, and atomic force microscopy. The photocatalytic activity of the composite films, calcined at 450 °C, and the regeneration of the activity under the same experimental conditions, were assessed using gas chromatography to study the photodegradation of phenol, an industrial pollutant, in water under 365 nm irradiation. The film with 15.0 wt.% of P25 TiO2 was found to be more photoactive (54 ppm of degraded phenol at 6 h of illumination) than the other ones.  相似文献   

8.
The paper reports on thermal stability of alumina thin films containing γ-Al2O3 phase and its conversion to a thermodynamically stable α-Al2O3 phase during a post-deposition equilibrium thermal annealing. The films were prepared by reactive magnetron sputtering and subsequently post-deposition annealing was carried out in air at temperatures ranging from 700 °C to 1150 °C and annealing times up to 5 h using a thermogravimetric system. The evolution of the structure was investigated by means of X-ray diffraction after cooling down of the films. It was found that (1) the nanocrystalline γ-Al2O3 phase in the films is thermally stable up to 1000 °C even after 5 h of annealing, (2) the nanocrystalline θ-Al2O3 phase was observed in a narrow time and temperature region at ≥1050 °C, and (3) annealing at 1100 °C for 2 h resulted in a dominance of the α-Al2O3 phase only in the films with a sufficient thickness.  相似文献   

9.
To use solar irradiation or interior lighting efficiently, we sought a photocatalyst with high reactivity under visible light. Nitrogen and carbon doping TiO2−xyNxCy films were obtained by heating the TiO2 gel in an ionized N2 gas and then were calcined at 500 °C. The TiO2−xyNxCy films have revealed an improvement over the TiO2 films under visible light (wavelength, 500 nm) in optical absorption and photocatalytic activity such as photodegradation of methyl orange. X-ray photoemission spectroscopy, infrared spectrum and UV-visible (UV-vis) spectroscopy were used to find the difference of two kinds of films. Nitrogen and carbon doped into substitutional sites of TiO2 has been proven to be indispensable for band-gap narrowing and photocatalytic activity.  相似文献   

10.
Rare-earth oxide films for gate dielectric on n-GaAs have been investigated. The oxide films were e-beam evaporated on S-passivated GaAs, considering interfacial chemical bonding state and energy band structure. Rare-earth oxides such as Gd2O3, (GdxLa1−x)2O3, and Gd-silicate were employed due to high resistivity and no chemical reaction with GaAs. Structural and bonding properties were characterized by X-ray photoemission, absorption, and diffraction. The electrical characteristics of metal-oxide-semiconductor (MOS) diodes were correlated with material properties and energy band structures to guarantee the feasibility for MOS field effect transistor (FET) application.Gd2O3 films were grown epitaxially on S-passivated GaAs (0 0 1) at 400 °C. The passivation induced a lowering of crystallization temperature with an epitaxial relationship of Gd2O3 (4 4 0) and GaAs (0 0 1). A better lattice matching relation between Gd2O3 and GaAs substrate was accomplished by the substitution of Gd with La, which has larger ionic radius. The in-plane relationship of (GdxLa1−x)2O3 (4 4 0) with GaAs (0 0 1) was found and the epitaxial films showed an improved crystalline quality. Amorphous Gd-silicate film was synthesized by the incorporation of SiO2 into Gd2O3. These amorphous Gd-silicate films excluded defect traps or current flow path due to grain boundaries and showed a relatively larger energy band gap dependent on the contents of SiO2. Energy band parameters such as ΔEC, ΔEV, and Eg were effectively controlled by the film composition.  相似文献   

11.
Highly ordered titanium oxide (TiO2) nanotubes were prepared by electrolytic anodization of titanium electrodes. Morphological evolution and phase transformations of TiO2 nanotubes on a Ti substrate and that of freestanding TiO2 membranes during the calcinations process were studied by scanning electron microscopy, transmission electron microscopy, and X-ray diffraction microscopy. The detailed results and mechanisms on the morphology and crystalline structure were presented. Our results show that a compact layer exists between the tubular layer and Ti substrate at 600 °C, and the length of the nanotubes shortens dramatically at 750 °C. The freestanding membranes have many particles on their tubes during calcinations from 450 to 900 °C. The TiO2 nanotubes on the Ti substrate transform to rutile crystals at 600 °C, while the freestanding TiO2 membranes retain an anatase crystal with increasing temperature to 800 °C. The photocatalytic activity of TiO2 nanotubes on a Ti substrate annealed at different temperatures was investigated by the degradation of methyl orange in aqueous solution under UV light irradiation. Due to the anatase crystals in the tubular layer and rutile crystals in the compact layer, TiO2 nanotubes annealed at 450 °C with pure anatase crystals have a better photocatalytic activity than those annealed at 600 °C or 750 °C.  相似文献   

12.
A series of ZnO films with TiO2 buffer on Si (1 0 0) substrates were prepared by DC reactive sputtering. Growth temperature of TiO2 buffer changed from 100 °C to 400 °C, and the influence on the crystal structures and optical properties of ZnO films have been investigated. The XRD results show that the ZnO films with TiO2 buffer have a hexagonal wurtzite structure with random orientation, and with the increase of growth temperature of TiO2 buffer, the residual stresses were released gradually. Specially, the UV emission enhanced distinctly and FWHMs (full width half maximum) decreased linearly with the increasing TiO2 growth temperature. The results all come from the improvement of crystal quality of ZnO films.  相似文献   

13.
TiO2 sol-gels with various Ag/TiO2 molar ratios from 0 to 0.9% were used to fabricate silver-modified nano-structured TiO2 thin films using a layer-by-layer dip-coating (LLDC) technique. This technique allows obtaining TiO2 nano-structured thin films with a silver hierarchical configuration. The coating of pure TiO2 sol-gel and Ag-modified sol-gel was marked as T and A, respectively. According to the coating order and the nature of the TiO2 sol-gel, four types of the TiO2 thin films were constructed, and marked as AT (bottom layer was Ag modified, surface layer was pure TiO2), TA (bottom layer was pure TiO2, surface layer was Ag modified), TT (pure TiO2 thin film) and AA (TiO2 thin film was uniformly Ag modified). These thin films were characterized by means of linear sweep voltammetry (LSV), X-ray diffraction (XRD), scanning electron microscopy (SEM), electrochemical impedance spectroscopy and transient photocurrent (Iph). LSV confirmed the existence of Ag0 state in the TiO2 thin film. SEM and XRD experiments indicated that the sizes of the TiO2 nanoparticles of the resulting films were in the order of TT > AT > TA > AA, suggesting the gradient Ag distribution in the films. The SEM and XRD results also confirmed that Ag had an inhibition effect on the size growth of anatase nanoparticles. Photocatalytic activities of the resulting thin films were also evaluated in the photocatalytic degradation process of methyl orange. The preliminary results demonstrated the sequence of the photocatalytic activity of the resulting films was AT > TA > AA > TT. This suggested that the silver hierarchical configuration can be used to improve the photocatalytic activity of TiO2 thin film.  相似文献   

14.
The impact of the ZrO2/La2O3 film thickness ratio and the post deposition annealing in the temperature range between 400 °C and 600 °C on the electrical properties of ultrathin ZrO2/La2O3 high-k dielectrics grown by atomic layer deposition on (1 0 0) germanium is investigated. As-deposited stacks have a relative dielectric constant of 24 which is increased to a value of 35 after annealing at 500 °C due to the stabilization of tetragonal/cubic ZrO2 phases. This effect depends on the absolute thickness of ZrO2 within the dielectric stack and is limited due to possible interfacial reactions at the oxide/Ge interface. We show that adequate processing leads to very high-k dielectrics with EOT values below 1 nm, leakage current densities in the range of 0.01 A/cm2, and interface trap densities in the range of 2-5 × 1012 eV−1 cm−2.  相似文献   

15.
Silver nanorods with average diameters of 120-230 nm and aspect ratio of 1.7-5.0 were deposited on the surface of TiO2 films by photoelectrochemical reduction of Ag+ to Ag under UV light. The composite films prepared on soda-lime glass substrates were characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM) and atomic force microscopy (AFM). The results show that the TiO2 film after UV irradiation in AgNO3 solution is composed of anatase phase TiO2 and metallic silver with face centered cubic structure. Other compounds cannot be found in the final films. The maximum deposition content of silver particles on the surface of TiO2 film was obtained with the AgNO3 concentration of 0.1 M. The kinetic growth rates of silver particles can be controlled by photocatalytic activity of TiO2 films. The studies suggest that the growth rates of silver particles increase with the enhancement of photocatalytic activity of TiO2 films. The maximum growth rate of silver particles loaded on TiO2 films can be up to 0.353 nm min−1 among samples 1#, 2# and 3#, while the corresponding apparent rate constant of TiO2 is 1.751 × 10−3 min−1.  相似文献   

16.
Epitaxial In2O3 films have been deposited on Y-stabilized ZrO2 (YSZ) (1 0 0) substrates by metalorganic chemical vapor deposition (MOCVD). The films were deposited at different substrate temperatures (450-750 °C). The film deposited at 650 °C has the best crystalline quality, and observation of the interface area shows a clear cube-on-cube epitaxial relationship of In2O3(1 0 0)||YSZ(1 0 0) with In2O3[0 0 1]||YSZ[0 0 1]. The Hall mobility of the single-crystalline In2O3 film deposited at 650 °C is as high as 66.5 cm2 V−1 s−1 with carrier concentration of 1.5 × 1019 cm−3 and resistivity of 6.3 × 10−3 Ω cm. The absolute average transmittance of the obtained films in the visible range exceeds 95%.  相似文献   

17.
The diamond abrasive particles were coated with the TiO2/Al2O3 film by the sol-gel technique. Compared with the uncoated diamonds, the TiO2/Al2O3 film was excellent material for the protection of the diamonds. The results showed that the incipient oxidation temperature of the TiO2/Al2O3 film coated diamonds in air atmosphere was 775 °C, which was higher 175 °C than that of the uncoated diamonds. And the coated diamonds also had better the diamond's single particle compressive strength and the impact toughness than that of uncoated diamonds after sintering at 750 °C. For the vitrified bond grinding wheels, replacing the uncoated diamonds with the TiO2/Al2O3 film coated diamonds, the volume expansion of the grinding wheels decreased from 6.2% to 3.4%, the porosity decreased from 35.7% to 25.7%, the hardness increased from 61.2HRC to 66.5HRC and the grinding ratio of the vitrified bond grinding wheels to carbide alloy (YG8) increased from 11.5 to 19.1.  相似文献   

18.
Nb-doped TiO2 (TNO) thin films were prepared by sol-gel dip-coating method with Nb content in a wide range of 0-20 at.%. The prepared films were preheated at 400 °C and then undertaken by two different post-annealing processes: (a) three times vacuum annealing and (b) multi-round annealing. The designed multi-round annealing was shown to be an effective way to improve the conductive properties of the films, compared to the traditional vacuum annealing process. The minimum resistivity reached approximately 0.5 Ω cm with Nb doping concentration around 12 at.%, and the carrier density increased with Nb-doping concentration until the critical point of 12 at.%, which might be the optimal doping content for our TNO films prepared by sol-gel method.  相似文献   

19.
The effect of thickness of TiO2 coating on synergistic photocatalytic activity of TiO2 (anatase)/α-Fe2O3/glass thin films as photocatalysts for degradation of Escherichia coli bacteria in a low-concentration H2O2 solution and under visible light irradiation was investigated. Nanograined α-Fe2O3 films with optical band-gap of 2.06 eV were fabricated by post-annealing of thermal evaporated iron oxide thin films at 400 °C in air. Increase in thickness of the Fe2O3 thin film (here, up to 200 nm) resulted in a slight reduction of the optical band-gap energy and an increase in the photoinactivation of the bacteria. Sol-gel TiO2 coatings were deposited on the α-Fe2O3 (200 nm)/glass films, and then, they were annealed at 400 °C in air for crystallization of the TiO2 and formation of TiO2/Fe2O3 heterojunction. For the TiO2 coatings with thicknesses ≤50 nm, the antibacterial activity of the TiO2/α-Fe2O3 (200 nm) was found to be better than the activity of the bare α-Fe2O3 film. The optimum thickness of the TiO2 coating was found to be 10 nm, resulting in about 70 and 250% improvement in visible light photo-induced antibacterial activity of the TiO2/α-Fe2O3 thin film as compared to the corresponding activity of the bare α-Fe2O3 and TiO2 thin films, respectively. The improvement in the photoinactivation of bacteria on surface of TiO2/α-Fe2O3 was assigned to formation of Ti-O-Fe bond at the interface.  相似文献   

20.
The effect of N2 treatment on the photocatalytic activity of Pt0/TiO2 was investigated. The results showed that after treatment at 500 °C in N2, 70% of the photocatalytic activity of 1.0 wt.% Pt0/TiO2 was lost by the evaluation of photocatalytic oxidation reaction of C3H6. Transmission electron microscopy (TEM) and Ar+ ion sputtering tests revealed that in the course of high-temperature N2 treatment, the size of Pt0 particles on TiO2 increases and a strong interaction between metal and support, i.e. Pt0 particles encapsulated by TixOy, happens, which are the reasons for the deactivation of Pt0/TiO2 photocatalyst treated by high-temperature N2.  相似文献   

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