Influence of annealing temperature on the structural, mechanical and wetting property of TiO2 films deposited by RF magnetron sputtering

TiO₂ films have been deposited on silicon substrates by radio frequency magnetron sputtering of a pure Ti target in Ar/O₂ plasma. The TiO₂ films deposited at room temperature were annealed for 1 h at different temperatures ranging from 400 °C to 800 °C. The structural, morphological, mechanical properties and the wetting behavior of the as deposited and annealed films were obtained using Raman spectroscopy, atomic force microscopy, transmission electron microscopy, nanoindentation and water contact angle (CA) measurements. The as deposited films were amorphous, and the Raman results showed that anatase phase crystallization was initiated at annealing temperature close to 400 °C. The film annealed at 400 °C showed higher hardness than the film annealed at 600 °C. In addition, the wettability of film surface was enhanced with an increase in annealing temperature from 400 °C to 800 °C, as revealed by a decrease in water CA from 87° to 50°. Moreover, the water CA of the films obtained before and after UV light irradiation revealed that the annealed films remained more hydrophilic than the as deposited film after irradiation.     

CF4 plasma effect combined with rapid thermal annealing for high-k Er2O3 dielectrics

In this study, the influence of the duration of CF₄ plasma treatment of rapid thermal annealing on high-k Er₂O₃ dielectrics deposited on polycrystalline silicon was investigated using electrical and material analyses. Results demonstrate that Er₂O₃ dielectric films annealed at 800 °C and plasma treated with CF₄ for a period of 1 min exhibited excellent dielectric performance, including a higher breakdown electric field, lower charge trapping rate, and a larger charge-to-breakdown than the as-deposited sample. Performance improvements were caused by the incorporation of fluorine atoms and the reduction of dangling bonds and defect traps.     

Preparation of cobalt-zinc ferrite (Co0.8Zn0.2Fe2O4) nanopowder via combustion method and investigation of its magnetic properties

Cobalt-zinc ferrite (Co_0.8Zn_0.2Fe₂O₄) was prepared by combustion method, using cobalt, zinc and iron nitrates. The crystallinity of the as-burnt powder was developed by annealing at 700 °C. Crystalline phase was investigated by XRD. Using Williamson-Hall method, the average crystallite sizes for nanoparticles were determined to be about 27 nm before and 37 nm after annealing, and residual stresses for annealed particles were omitted. The morphology of the annealed sample was investigated by TEM and the mean particle size was determined to be about 30 nm. The final stoichiometry of the sample after annealing showed good agreement with the initial stoichiometry using atomic absorption spectrometry. Magnetic properties of the annealed sample such as saturation magnetization, remanence magnetization, and coercivity measured at room temperature were 70 emu/g, 14 emu/g, and 270 Oe, respectively. The Curie temperature of the sample was determined to be 350 °C using AC-susceptibility technique.     

Hydrophilic properties of nano-TiO2 thin films deposited by RF magnetron sputtering

Microstructure and hydrophilicity of nano-titanium dioxide (TiO₂) thin films, deposited by radio frequency magnetron sputtering, annealed at different temperatures, were studied by field emission scanning electron microscopy (SEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and water contact angle methods. It is found that the crystal phase transforms from amorphous to rutile structure with increase of annealing temperature from room temperature to 800 °C. It is also indicated that the organic contaminants on the surface of the films can be removed and the oxygen vacancies can be reduced by the annealing treatment. Annealed at the temperature below 300 °C, amorphous TiO₂ thin films show rather poor hydrophilicity, and annealed at the temperature range from 400 to 650 °C, the super hydrophilicity anatase of TiO₂ thin films can be observed. However, when the annealing temperature reaches 800 °C, the hydrophilicity of the films declines mainly derived from the appearance of rutile.     

Broad band optical characterization of sol-gel TiO2 thin film microstructure evolution with temperature

Titanium dioxide (TiO₂) thin films have been produced by spin coating a titanium isopropoxide sol on silicon wafer substrates. The structural evolution of the thin films in terms of decomposition, crystallization and densification has been monitored as a function of annealing temperature from 100 to 700 °C using optical characterization and other techniques. The effect of annealing temperature on the refractive index and extinction coefficient of these TiO₂ thin films was studied in the range of 0.62 to 4.96 eV photon energy (250-2000 nm wavelength) using spectroscopic ellipsometry. Thermal gravimetric analysis and atomic force microscopy support the ellipsometry data and provide information about structural transformations in the titania thin films with respect to different annealing temperatures. These data help construct a coherent picture of the decomposition of the sol-gel precursors and the creation of dense layers of TiO₂. It was observed that the refractive index increased from 2.02 to 2.45 at 2.48 eV (500 nm) in sol-gel spin coated titania films for annealing temperatures from 100 °C to 700 °C.     

Characterization and optoelectronic properties of sol-gel-derived CuFeO2 thin films

In this study, CuFeO₂ thin films were deposited onto quartz substrates using a sol-gel and a two-step annealing process. The sol-gel-derived films were annealed at 500 °C for 1 h in air and then annealed at 600 to 800 °C for 2 h in N₂. X-ray diffraction patterns showed that the annealed sol-gel-derived films were CuO and CuFe₂O₄ phases in air annealing. When the films were annealed at 600 °C in N₂, an additional CuFeO₂ phase was detected. As the annealing temperature increased above 650 °C in N₂, a single CuFeO₂ phase was obtained. The binding energies of Cu-2p_3/2, Fe-2p_3/2, and O-1s were 932.5 ± 0.1 eV, 710.3 ± 0.2 eV and 530.0 ± 0.1 eV for CuFeO₂ thin films. The chemical composition of CuFeO₂ thin films was close to its stoichiometry, which was determined by X-ray photoelectron spectroscopy. Thermodynamic calculations can explain the formation of the CuFeO₂ phase in this study. The optical bandgap of the CuFeO₂ thin films was 3.05 eV, which is invariant with the annealing temperature in N₂. The p-type characteristics of CuFeO₂ thin films were confirmed by positive Hall coefficients and Seebeck coefficients. The electrical conductivities of CuFeO₂ thin films were 0.28 S cm^− 1 and 0.36 S cm^− 1 during annealing at 650 °C and 700 °C, respectively, in N₂. The corresponding carrier concentrations were 1.2 × 10¹⁸ cm^− 3 (650 °C) and 5.3 × 10¹⁸ cm^− 3 (700 °C). The activation energies for hole conduction were 140 meV (650 °C) and 110 meV (700 °C). These results demonstrate that sol-gel processing is a feasible preparation method for delafossite CuFeO₂ thin films.     

Annealing effects on microstructure and mechanical properties of sputtered multilayer Cr(1 − x)AlxN films

Multilayer Cr_(1 − x)Al_xN films with a total thickness of 2 μm were deposited on high-speed steel by medium frequency magnetron sputtering from Cr and Al-Cr (70 at.% Al) targets. The samples were annealed in air at 400 °C, 600 °C, 800 °C and 1000 °C for 1 hour. Films were characterized by cross-sectional scanning electron microscopy and X-ray diffraction analysis. The grain size of the as-deposited multilayer films is about 10 nm, increasing with the annealing temperature up to 100 nm. Interfacial reactions have clearly changed at elevated annealing temperatures. As-deposited films' hardness measured by nanoindentation is 22.6 GPa, which increases to 26.7 GPa when the annealing temperature goes up to 400 and 600 °C, but hardness decreases to 21.2 GPa with further annealing temperature increase from 600 to 1000 °C. The multilayer film adhesion was measured by means of the scratch test combined with acoustic emission for detecting the fracture load. The critical normal load decreased from 49.7 N for the as-deposited films to 21.2 N for the films annealed at 1000 °C.     

Structural, thermal and optical characterization of TiO2:ZrO2 thin films prepared by sol-gel method

We have studied the structural and optical properties of thin films of TiO₂, doped with 5% ZrO₂ and deposited on glass substrate (by the sol-gel method). The dip-coated thin films have been examined at different annealing temperatures (350 to 450 °C) and for various layer thicknesses (63-286 nm). Refractive index and porosity were calculated from the measured transmittance spectrum. The values of the index of refraction are in the range of 1.62-2.29 and the porosity is in the range of 0.21-0.70. The coefficient of transmission varies from 50 to 90%. In the case of the powder of TiO₂, doped with 5% ZrO₂, and aged for 3 months in ambient temperature, we have noticed the formation of the anatase phase (tetragonal structure with 14.8 nm grains). However, the undoped TiO₂ exhibits an amorphous phase. After heat treatments of thin films, titanium oxide starts to crystallize at the annealing temperature 350 °C. The obtained structures are anatase and brookite. The calculated grain size, depending on the annealing temperature and the layer thickness, is in the range (8.58-20.56 nm).     

High dielectric tunability of Ba0.6Sr0.4TiO3 thin film deposited by radio-frequency magnetron sputtering

In microwave tunable devices, one of the major challenges encountered is the simultaneous minimization of the material's dielectric loss and maximization of dielectric tunability. In this work, Ba_0.6Sr_0.4TiO₃ thin film with the thickness of 300 nm was deposited on Pt/SiO₂/Si substrates using radio-frequency magnetron sputtering technique, and its dielectric properties were investigated. Due to the high temperature annealing process at substrate temperature of 600 °C, well-crystallized Ba_0.6Sr_0.4TiO₃ film was deposited. The dielectric constant and dielectric loss of the film at 100 kHz are 300 and 0.033, respectively. Due to the good crystallinity of the Ba_0.6Sr_0.4TiO₃ films deposited by radio-frequency magnetron sputtering, high dielectric tunability up to 38.3% is achieved at a low voltage of 4.5 V.     

Effects of post-deposition surface treatment on the optical, structural and hydrogen sensing properties of TiO2 thin films

TiO₂ thin films were prepared by DC reactive magnetron sputtering in a mixture of oxygen and argon on glass and oxidized silicon substrates. The effect of post-deposition annealing (300 °C, 500 °C and 700 °C for 8 h in air) on the structural and morphological properties of TiO₂ thin films is presented. In addition, the effect of Pt surface modification (1, 3 and 5 nm) on hydrogen sensing was studied. XRD patterns have shown that in the range of annealing temperatures from 300 °C to 500 °C crystallization starts and the thin film structure changes from amorphous to polycrystalline (anatase phase). In the case of samples on glass substrate, optical transmittance spectra were recorded. TiO₂ thin films were tested as sensors of hydrogen at concentrations 10,000-1000 ppm and operating temperatures within the 180-200 °C range. The samples with 1 nm and in particular with 3 nm of Pt on the surface responded to hydrogen fast and with high sensitivity.     

Correlation study between structural, magnetic and transport properties of annealed Co thin films

This paper presents structural, magnetization and transport properties measurements carried out on as-deposited Co (400 Å) thin film as well as samples annealed in the temperature range 100-500 °C in steps of 100 °C for 1 h. The samples used in this work were deposited on float glass substrates using ion beam sputtering technique. The magnetization measurements carried out using MOKE technique, clearly indicates that as-deposited as well as annealed samples up to 500 °C show well saturation magnetization with applied magnetic field. The as-deposited sample shows coercivity value (H_c) of 26 Oe, and it is increased to 94 Oe for 500 °C-annealed sample. A minimum coercivity value of 15 Oe is obtained for 200 °C annealed sample. The XRD measurements of as deposited films show microcrystalline nature of Co film, which becomes crystalline with increase in annealing temperature. The corresponding resistivity measurements show gradual decrease in resistivity. AFM technique was employed to study the surface morphology of as deposited film as well as annealed thin films. Observed magnetization, and resistivity behaviour is mainly attributed to the (i) change in crystal structure (ii) increase in grain size and (iii) stress relaxation due to the annealing treatment.     

Deposition and post-deposition annealing of thin Y2O3 film on n-type Si in argon ambient

Thin (∼5.0 nm) Y₂O₃ films were deposited on n-type Si (1 0 0) substrate using RF magnetron sputtering. Detailed studies on the effects of post-deposition annealing (PDA) temperatures (400, 600, 800, and 1000 °C) in argon ambient on these films were performed by X-ray diffraction (XRD), Fourier transform infrared spectrometer (FTIR), field emission scanning electron microscopy, and atomic force microscopy. Interfacial layer (IL) of SiO₂ in between Y₂O₃ and the Si substrate for sample annealed from 400 to 800 °C had been suggested from the results of FTIR. As for sample annealed at 1000 °C, presence of IL might consist of both Y₂Si₂O₇ and/or SiO₂ through the detection of Y₂Si₂O₇ compound and Si–O chemical bonding from XRD and FTIR analysis, respectively. For as-deposited sample, no detectable chemical functional group at the IL was recorded. Electrical characteristics of the Y₂O₃ films were acquired by fabricating metal-oxide–semiconductor capacitor as test structure. An improvement in the breakdown voltage (V_B) and leakage current density (J) was perceived as the PDA temperature increased. Of the PDA samples, the attainment of the lowest effective oxide charge, interface trap density, total interface trap density, and the highest barrier height at 1000 °C had contributed to the acquisition of the highest V_B and lowest J.     

Enhanced photocatalytic activity of TiO2 by polydimethylsiloxane deposition and subsequent thermal treatment at 800 °C

A thin film of polydimethylsiloxane (PDMS) was coated on TiO₂ nanoparticles (P-25, Dagussa), and surface structures of the thin films were analyzed by Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy. Furthermore, photocatalytic activity of PDMS-coated TiO₂ samples with various annealing temperatures was determined using UV irradiation. We show that the 800 °C-annealed sample of PDMS-coated TiO₂ showed a two-fold higher photocatalytic activity with respect to the bare TiO₂. The enhanced photocatalytic activity was attributed to the greater hydrophilicity of the annealed PDMS coating.     

Formation and transformation of ZnTiO3 prepared by sputtering process

Zinc titanate (ZnTiO₃) films were prepared using RF magnetron sputtering at substrate temperatures ranging from 30 to 400 °C. Subsequent annealing of the as-deposited films was performed at temperatures ranging from 600 to 900 °C. It was found that all as-deposited films were amorphous, as confirmed by XRD. This was further confirmed by the onset of crystallization that took place at annealing temperatures 600 °C. The phase transformation for the as-deposited films and annealed films were investigated in this study. The results revealed that pure ZnTiO₃ (hexagonal phase) can exist, and was obtained at temperatures between 700 and 800 °C. However, it was found that decomposition from hexagonal ZnTiO₃ to cubic Zn₂TiO₄ and rutile TiO₂ took place with a further increase in temperature to 900 °C.     

Annealing temperature effects on ferromagnetism and structure of Si1−xMnx films prepared by magnetron sputtering

Si_1−xMn_x diluted magnetic semiconductor films were deposited on the p-Si (100) single crystal wafer using magnetron sputtering method. Post-rapid thermal annealing treatments were performed at temperatures of 700 °C, 800 °C, and 900 °C in an argon atmosphere for approximately 5 min. Alternating gradient magnetometer, scanning electron microscope, atomic force microscope, X-ray diffraction and X-ray absorption near-edge structure spectra were employed to characterize magnetic properties and structure of the as-grown and annealed films. The films were about 2.8 μm thick and the RMS roughness of the surface was about 5-10 nm. All samples exhibit ferromagnetism at room temperature and the saturation magnetization reaches at the maximum value for the sample annealed at 700 °C. The silicide MnSi_1.7 was observed in the annealed samples. X-ray absorption near-edge structure spectra indicated that Mn atoms preferred to occupy substitutional or interstitial sites instead of precipitating to form silicide when annealing at 700 °C. It is inferred that the observed ferromagnetism is attributed to the interstitial and substitutional Mn dimers, which existed mostly in the sample annealed at 700 °C. The weaker ferromagnetism of the 900 °C annealed sample was closely related to the increased content of Mn₄Si₇ compound.     

Effects of oxygen flow ratios and annealing temperatures on Raman and photoluminescence of titanium oxide thin films deposited by reactive magnetron sputtering

Titanium oxide (TiO_x) thin films were deposited on the Si(100) substrates by direct-current reactive magnetron sputtering at 3-15 % oxygen flow ratios (FO₂% = FO₂/(FO₂ + FAr) × 100%), and then annealed by rapid thermal annealing (RTA) at 350-750 °C for 2 min in air. The phase, bonding and luminescence behaviors of the as-deposited and annealed TiO_x thin films were analyzed by X-ray diffraction (XRD), Raman spectroscopy and photoluminescence (PL) spectroscopy, respectively. The as-deposited TiO_x films were amorphous from XRD and showed weak Raman intensity. In contrast, the distinct crystalline peaks of anatase and rutile phases were detected after RTA at 550-750 °C from both XRD and Raman spectra. A mixture of anatase and rutile phases was obtained by RTA at 3 FO₂% and its amount increased with annealing temperature. Only the anatase phase was detected in the 6-15 FO₂% specimens after RTA. The PL spectra of all post-annealed TiO_x films showed a broad peak in visible light region. The PL peak of TiO_x film at 3 FO₂% at 750 °C annealing can be fitted into two Gaussian peaks at ~ 486 nm (2.55 eV) and ~ 588 nm (2.11 eV) which were attributed to deep-level emissions of oxygen vacancies in the rutile and anatase phases, respectively. The peak around 550 nm was observed at 6-15 FO₂% which is attributed to electron-hole pair recombination from oxygen vacancy state in anatase phase to valence band. The variation of intensity of PL peaks is concerned with the formation of the rutile and anatase phases at different FO₂% and annealing temperatures.     

Effect of postdeposition annealing on the structural and electrical properties of thin Dy2TiO5 dielectrics

This paper describes the effect of postdeposition annealing on the structural and electrical characteristics of high-k Dy₂TiO₅ dielectric films deposited on Si (100) through reactive cosputtering. We used X-ray diffraction, X-ray photoelectron spectroscopy, secondary ion mass spectrometry, and atomic force microscopy to investigate the structural and morphological features of these films after they had been subjected to annealing at different temperatures. The Dy₂TiO₅ dielectrics annealed at 800 °C exhibited excellent electrical properties such as high capacitance value, small density of interface state, almost no hysteresis voltage, and low leakage current. This phenomenon is attributed to a rather well-crystallized Dy₂TiO₅ structure and the reduction of the interfacial layer at oxide/Si interface. This film also shows almost negligible charge trapping under high constant voltage stress.     

Influence of annealing treatments for ZnO-doped Zr0.8Sn0.2TiO4 thin films by RF magnetron sputtering

Zirconium tin titanium oxide doped 1 wt.% ZnO thin films on n-type Si substrate were deposited by rf magnetron sputtering at a fixed rf power of 300 W, a substrate temperature of 450 °C, a deposition pressure of 5 mTorr and an Ar/O₂ ratio of 100/0 with various annealing temperatures and annealing times. Electrical properties and microstructures of 1 wt.% ZnO-doped (Zr_0.8Sn_0.2)TiO₄ thin films prepared by rf magnetron sputtering on n-type Si(100) substrates at different annealing temperatures (500 °C-700 °C) and annealing times (2 h-6 h) have been investigated. The structural and morphological characteristics analyzed by X-ray diffraction (XRD) and atomic force microscope (AFM) were sensitive to the treatment conditions such as annealing temperature and annealing time. At an annealing temperature of 600 °C and an annealing time of 6 h, the ZnO-doped (Zr_0.8Sn_0.2)TiO₄ thin films possess a dielectric constant of 46 (at f = 10 MHz), a dissipation factor of 0.059 (at f = 10 MHz), and a low leakage current density of 3.8 × 10^− 9 A/cm² at an electrical field of 1 kV/cm.     

Dye-sensitized solar cells with TiO2 nanocrystalline films prepared by conventional and rapid thermal annealing processes

Titanium oxide (TiO₂) thin films are prepared by the sol-gel method and annealed at 600 °C by conventional (CTA) and rapid thermal annealing (RTA) processes on fluorine-doped tin oxide -coated glass substrates for application as the work electrode for the dye-sensitized solar cells (DSSC). TiO₂ thin films are crystallized using a conventional furnace and the proposed RTA process at annealing rates of 5 °Cmin⁻¹ and 600 °Cmin⁻¹, respectively. The TiO₂ thin films are characterized by X-ray diffraction, scanning electron microscopy and Brunauer-Emmett-Teller analysis. Based on the results, the TiO₂ films crystallized by RTA show better crystallization, higher porosity and larger surface area than those of CTA. The short-circuit photocurrent and open-circuit voltage values increased from 5.2 mAcm⁻² and 0.6 V for the DSSC with the CTA-derived TiO₂ films to 8.3 mAcm⁻² and 0.68 V, respectively, for the DSSC containing RTA-derived TiO₂ films.     

Effect of process parameters and post deposition annealing on the optical, structural and microwave dielectric properties of RF magnetron sputtered (Ba0.5,Sr0.5)TiO3 thin films

Thin films of (Ba_0.5,Sr_0.5)TiO₃ (BST5) in the thickness range 400-800 nm have been deposited by RF magnetron sputtering on to quartz substrates at ambient temperature. All the properties investigated, i.e. structure, microstructure, optical and microwave dielectric, show a critical dependence on the processing and post processing parameters. The surface morphology as studied by atomic force microscopy reveals ultra fine grains in the case of as deposited films and coarse grain morphology on annealing. The as-deposited films are X-ray amorphous and exhibit refractive index in the range 1.9-2.04 with an optical absorption edge value between 3.8 and 4.2 eV and a maximum dielectric constant of 35 at 12 GHz. The dispersion in refractive index fits into the single effective oscillator model while the variation in the optical parameters with oxygen percentage in the sputtering gas can be explained on the basis of packing fraction changes. On annealing the films at 900 °C they crystallize in to the perovskite structure accompanied by a decrease in optical band gap, increase in refractive index and increase in the microwave dielectric constant. At 12 GHz the highest dielectric constant achieved in the annealed films is 175. It is demonstrated that with increasing oxygen-mixing percentage in the sputtering gas, the microwave dielectric loss decreases while the dielectric constant increases.