Evolution of structural and optical properties of rutile TiO2 thin films synthesized at room temperature by chemical bath deposition method

Nanocrystalline thin films of TiO₂ were prepared on glass substrates from an aqueous solution of TiCl₃ and NH₄OH at room temperature using the simple and cost-effective chemical bath deposition (CBD) method. The influence of deposition time on structural, morphological and optical properties was systematically investigated. TiO₂ transition from a mixed anatase–rutile phase to a pure rutile phase was revealed by low-angle XRD and Raman spectroscopy. Rutile phase formation was confirmed by FTIR spectroscopy. Scanning electron micrographs revealed that the multigrain structure of as-deposited TiO₂ thin films was completely converted into semi-spherical nanoparticles. Optical studies showed that rutile thin films had a high absorption coefficient and a direct bandgap. The optical bandgap decreased slightly (3.29–3.07 eV) with increasing deposition time. The ease of deposition of rutile thin films at low temperature is useful for the fabrication of extremely thin absorber (ETA) solar cells, dye-sensitized solar cells, and gas sensors.     

Influence of solvent on solution processed Cu2ZnSnS4 nanocrystals and annealing induced changes in the optical,structural properties of CZTS film

The well-known quaternary Cu₂ZnSnS₄ (CZTS) chalcogenide thin films are playing an important role in modern technology. The CZTS nanocrystal were successfully prepared by solution method using water, ethylene glycol and ethylenediamine as different solvent. The pure phase material was used for thin film coating by thermal evaporation method. The prepared CZTS thin films were characterized by XRD, Raman spectroscopy, FESEM, XPS and FT-IR spectroscopy. The XRD and Raman spectroscopy analysis revealed the formation of polycrystalline CZTS thin film with tetragonal crystal structure after annealing at 450 ^°C. The oxidation state of the annealed film was studied by XPS. A direct band gap about 1.36 eV was estimated for the film from FT-IR studies, which is nearly close to the optimum value of band gap energy of CZTS materials for best solar cell efficiency. The CZTS annealed thin films are more suitable for using as a p-type absorber layer in a low-cost solar cell.     

Modulating microstructure and optical properties of hydrogenated nanocrystalline silicon photovoltaic materials prepared under hydrogen diluted silane PECVD by various DC bias

Hydrogenated nanocrystalline silicon (nc-Si:H) thin films were fabricated by plasma enhanced chemical vapor deposition under the various negative substrate bias voltages with hydrogen as a diluent of silane. The microstructure and optical properties of nc-Si:H thin films were studied by Raman scattering spectroscopy, X-ray diffraction (XRD), transmission electron microscopy, and optical transmission spectroscopy. Raman spectra and XRD pattern reveal that applying negative bias voltages at the moderate level favors the enhancement of crystalline volume fraction, increase of crystallite sizes and decrease of residual stress. We also demonstrated that the negative direct current bias can be used to modulate the volume fraction of voids, refractive index, absorption coefficient, compactness and ordered degree of nc-Si:H films. It is found that the film deposited at −80 V shows not only high crystallinity, size of crystallite, and static index n₀ but also low residual stress and volume fraction of voids. Furthermore, the microstructural evolution mechanism of nc-Si:H thin films prepared at different bias voltages is tentatively explored.     

Research on Raman-scattering and Fabrication of Multilayer Thin Film with Different Structures and Components Based on Pt/Ti/Si3N4/SiO2/Si Substrate

选用三水醋酸铅、乙酰基丙酮酸锆、四异丙氧基钛、乙酰丙酮作初始材料,用同样的方法分别制备了锆钛酸铅(PZT)和钛酸铅(PT)两种固体前驱物. 采用改良型的溶胶-凝胶工艺技术,分别在不同的Pt-Ti-Si₃N₄-SiO₂-Si基底上,按照不同的组合方式,制备了三种多层薄膜：PZT、PT/PZT-PZT/PT、PT/PZT/-/PZT/PT. 较详细地讨论了薄膜制备的工艺技术,发现当凝胶通过烧结和干燥后变成固态物质时,薄膜内部存在着较大的残余应力,当薄膜在600 ºC下退火时其内部残余应力可以被减小. 通过拉曼     

Rare earth doped cobalt ferrite thin films deposited by PLD

CoFe₂O₄ thin films with preferential texture structure, small grain size, and perpendicular magnetic anisotropy can be obtained by the pulsed laser deposition (PLD) technique. In this work, we studied the influence of the Fe³⁺ ions substitution by three elements from lanthanide group (Dy, La, and Gd) on the structural properties of the thin films. The samples were deposited by Nd:YAG laser (λ=532 nm, 10 ns) ablation of CoFe_1.8RE_0.2O₄, (RE=Dy, La, Gd) targets at various substrate temperatures ranging from room temperature to 600 °C. The microstructure and chemical composition of the thin films were investigated by Raman spectroscopy, XRD, SEM-EDS, and ToF-SIMS. The XRD patterns and Raman spectra of the thin films indicated the formation of a single spinel structure. Thus, the desired substitution of the iron ions in the spinel lattice with the RE elements was achieved in the thin films, although in the bulk material, their presence determined the formation of a residual phase with a perovskite-type structure.     

The effects of thermal annealing on the obliquely deposited Ag-Ge-S thin films

Obliquely deposited thin films of ternary Ag-Ge-S glasses are characterized in this work. Thin films are fabricated in a vacuum thermal evaporator at different evaporation angles and examined by Raman spectroscopy. The Raman mode frequency of GeS₄ corner-sharing (CS) structure of the as-deposited films display a red-shift as a function of Ag content due to reduced global connectivity, and therefore decreased network stress. Film thickness of normally deposited thin films is significantly less when compared against obliquely deposited ones. Sulfur-ring (S₈) modes are observed in thin films but not in corresponding bulk material. Thermal annealing of thin films results in the disappearance of Sulfur-ring (S₈) modes, while the temperature required for this phenomenon is deposition angle dependent. Thickness of the obliquely deposited films shrinks significantly after thermal annealing, which indicates a collapse of the micro-column structure introduced by oblique deposition.     

Characterization of Cu(In,Ga)Se2 thin films prepared by evaporationfrom ternary compounds

Thin films of Cu(In,Ga)Se₂ were fabricated by evaporation from ternary CuGaSe₂ and CuInSe₂ compounds for photovoltaic device applications and their properties were investigated. From XRF analysis, the Cu:(In+Ga):Se atomic ratio in all thin films was approximately 1:1:2. The Ga/(In+Ga) atomic ratio in the thin films changed linearly from 0 to 1.0 with increasing the [CGS]/([CGS]+[CIS]) mole ratio in the evaporating materials. However, for thin films prepared at the [CGS]/([CGS]+[CIS]) mole ratio above 0.4, the composition by EPMA analysis was not consistent with that by XRF analysis. The result of EPMA analysis showed that the surface of a thin film was Cu-rich. XRD studies demonstrated that the thin films prepared at the [CGS]/([CGS]+[CIS]) mole ratio under 0.2 had a chalcopyrite Cu(In,Ga)Se₂ structure and the preferred orientation to the 112 plane. On the other hand, XRD patterns of the thin films produced at the [CGS]/([CGS]+[CIS]) mole ratio above 0.6 showed the diffraction lines from a chalcopyrite Cu(In,Ga)Se₂ and a foreign phase. The separation of a peak was observed near 2θ=27°, indicative the graded Ga concentration in Cu(In,Ga)Se₂ thin film.     

Cu2ZnSnSe4 thin films prepared by selenization of co-electroplated Cu-Zn-Sn precursors

A novel technique for growth of high quality Cu₂ZnSnSe₄ (CZTSe) thin films is reported in our work. The CZTSe thin films were fabricated onto Mo layers by co-electroplating Cu-Zn-Sn precursors followed by annealing in the selenium vapors at the substrate temperature of 550 °C. The morphology and structure of CZTSe thin films were characterized using scanning electron microscopy (SEM), energy dispersive spectrometer (EDS), X-ray diffraction (XRD) and Raman scattering spectrum, respectively. The results revealed that the single phase was in the CZTSe thin films, and the other impurities such as ZnSe and Cu₂SnSe₃ were not existed though they were difficult to distinguish both from EDS and XRD.     

Raman-spectroscopy study of PbTiO3 thin films grown on Si substrates by metalorganic chemical vapor deposition

Raman spectra have been investigated in PbTiO₃ thin films grown on Si by metalorganic chemical vapor deposition. A large grazing-angle scattering technique was taken to measure the temperature dependence of Raman spectra below room temperature. All Raman modes in the thin films are assigned and compared with those in the bulk single crystal, a newA ₁(TO) soft mode at 104 cm^–1 was recorded which satisfies the Curie-Weiss relation ² =A(T _c –T). Intensities of theA ₁(1TO) andE(1TO) modes were anomalously strengthened with increasing temperature. Raman modes for the thin films exhibit remarkable frequency downshift and upshift which is related to the effect of internal stress.     

Influence of nanocrystalline structure and composition on hardness of thin films based on TiO<Subscript>2</Subscript>

In this work, the influence of Tb-doping on structure, and especially hardness of nanocrystalline TiO₂ thin films, has been described. Thin films were formed by a high-energy reactive magnetron sputtering process in a pure oxygen atmosphere. Undoped TiO₂-matrix and TiO₂:Tb (2 at. % and 2.6 at. %) thin films, had rutile structure with crystallite sizes below 10 nm. The high-energy process produces nanocrystalline, homogenous films with a dense and close packed structure, that were confirmed by X-ray diffraction patterns and micrographs from a scanning electron microscope. Investigation of thin film hardness was performed with the aid of a nanoindentation technique. Results of measurements have shown that the hardness of all manufactured nanocrystalline films is above 10 GPa. In the case of undoped TiO₂ matrix, the highest hardness value was obtained (14.3 GPa), while doping with terbium results in hardness decreasing down to 12.7 GPa and 10.8 GPa for TiO₂:(2 at. % Tb) and TiO₂:(2.6 at. % Tb) thin films, respectively. Incorporation of terbium into TiO₂-matrix also allows modification of the elastic properties of the films.     

Preparation and characterization of electrodeposited Sb2Se3 thin films from non-aqueous media

Semiconducting Sb₂Se₃ thin films have been prepared onto the stainless steel and fluorine doped tin oxide coated glass substrates from non-aqueous media using an electrodeposition technique. The electrodeposition potentials for different bath compositions and concentrations of solution have been estimated from the polarization curves. SbCl₃ and SeO₂ in the volumetric proportion as 1:1 with their equimolar solution concentration of 0.05 M form good quality films. The films are characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD) and optical absorption techniques. The SEM studies show that the film covers the total substrate surface with uneven surface morphology. The XRD patterns of the films obtained by varying compositions and concentrations show that the as-deposited films are polycrystalline with relatively higher grain size for 1:1 composition and 0.05 M concentration. The optical band gap energy for indirect transition in Sb₂Se₃ thin films is found to be 1.195 eV.     

Ferroelectric SrxBa1-xNb2O6 optical waveguiding thin films on SiO2-coated Si(100) substrates

x Ba_1-xNb₂O₆ (x=0.5) films (abbreviated as SBN:0.5) on SiO₂-coated Si substrates are potential components for the application of integrated electro-optics devices. SBN:0.5 optical waveguiding thin films on SiO₂-coated Si substrates with a very thin MgO diffusion buffer have been successfully prepared by pulsed laser deposition. The as-grown films have a refractive index of 2.28, which is close to that of bulk SBN. X-ray analysis showed that the as-grown films have a single-phase tetragonal tungsten bronze structure. The SBN:0.5 thin films prepared by PLD exhibit favorable ferroelectric and optical waveguiding properties. The composition and the morphology of the films were also examined by XPS and by SEM, respectively. Ferroelectric SBN:0.5 optical waveguiding thin films on SiO₂-coated Si substrates are expected to be used in integrated electro-optic devices. Received: 27 February 1997/Accepted: 17 October 1997     

Influences of the iron ion (Fe)-doping on structural and optical properties of nanocrystalline TiO2 thin films prepared by sol-gel spin coating

Titanium dioxide (TiO₂) thin films doping of various iron ion (Fe³⁺) concentrations were deposited on silicon (Si) (100) and quartz substrates by sol-gel Spin Coating technique followed by a thermal treatment at 600 °C. The structure, surface morphology and optical properties, as a function of the doping, have been studied by X-ray diffractometer (XRD), Raman, ultraviolet-visible (UV-vis) and Spectroscopic Ellipsometry (SE). XRD and Raman analyzes of our thin films show that the crystalline phase of TiO₂ thin films comprised only the anatase TiO₂, but the crystallinity decreased when the Fe³⁺ content increased from 0% to 20%. During the Fe³⁺ addition to 20%, the phase of TiO₂ thin film still maintained the amorphous state. The grain size calculated from XRD patterns varies from 29.3 to 22.6 nm. The complex index and the optical band gap (E_g) of the films were determined by the spectroscopic ellipsometry analysis. We have found that the optical band gap decreased with an increasing Fe³⁺ content.     

Nanoindentation on carbon thin films obtained from a C60 ion beam

Raman spectra, atomic force microscope (AFM) images, hardness (H) and Young's modulus (E) measurements were carried out in order to characterize carbon thin films obtained from a C₆₀ ion beam on silicon substrates at different deposition energies (from 100 up to 500 eV). The mechanical properties were studied via the nanoindentation technique. It has been observed by Raman spectroscopy and AFM that the microstructure presents significant changes for films deposited at energies close to 300 eV. However, these remarkable changes have not been noticeable on the mechanical properties: apparently H and E increase with higher deposition energy up to ∼11 and ∼116 GPa, respectively. These values are underestimated if the influence of the film roughness is not taken into account.     

Raman spectroscopy study of REH3 under pressure

The Raman spectroscopic studies of two rare earth trihydrides: Y H₃, HoH₃, have been performed in the pressure range from ambient up to 16 GPa and 25 GPa respectively. For the first time samples of REH₃ in the form of powder have been studied by Raman spectroscopy using the Diamond Anvil Cell (DAC) technique. A rapid decrease of Raman activity has been observed for the hydrides under pressure values in the vicinity of structural phase transition. Metallization as a possible reason for the observed dramatic change of the REH₃ Raman activity has been discussed.     

Temperature dependent Raman scattering in polycrystalline Bi4Ti3O12 thin films

Polycrystalline Bi₄Ti₃O₁₂ thin films were prepared on quartz substrates by pulsed laser deposition. The films were crystallized in the orthorhombic layer perovskite structure confirmed by X-ray diffraction and Raman spectroscopy. The Raman spectra are strongly dependent on temperature. A subtle phase transition in the temperature range 473-573 K exists in polycrystalline BTO thin films, which is evidenced by the disappearance of the Raman band at 116 cm⁻¹ and appearance of a new Raman band at 151 cm⁻¹. The two broad Raman bands centered at the 57 and 93 cm⁻¹ at 300 K break up into clusters of several sharp Raman peaks at 77 K, due to monoclinic distortion of orthorhombic structure at low temperature in the as-prepared Bi₄Ti₃O₁₂ thin films.     

Electrosynthesis and characterization of CdSe thin films: Optimization of preparative parameters by photoelectrochemical technique

CdSe thin films have been electrodeposited potentiostatically onto stainless-steel and fluorine-doped tin oxide-coated glass substrates from an aqueous acidic bath using cadmium acetate ((CH₃COO)₂Cd·2H₂O) as a Cd ion source. Preparative parameters such as deposition potential, solution concentration, bath temperature, pH of the electrolytic bath and deposition time have been optimized by using photoelectrochemical (PEC) technique to obtain well adherent and uniform thin films. The electrodeposits were dark brown in colour. The films have been characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and optical absorption techniques. XRD studies reveal that films are polycrystalline, with hexagonal crystal structure. SEM shows that the films are compact, with spherical grains. Optical absorption studies reveal that the material exhibits a direct optical transition having band gap energy ∼1.72 eV. PEC study shows that the films are photoactive.     

Effect of nitrogen content on phase configuration, nanostructure and mechanical behaviors in magnetron sputtered SiCxNy thin films

SiC_xN_y thin films with different nitrogen contents were deposited by way of incorporation of different amounts of nitrogen into SiC_0.70 using unbalanced reactive dc magnetron sputtering method. Their phase configurations, nanostructures and mechanical behaviors were investigated by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), Raman spectroscopy, high-resolution transmission electron microscopy (HRTEM) and microindentation methods. The result indicated SiC_0.70 and all SiC_xN_y thin films exhibited amorphous irrespective of the nitrogen content. The phase configuration and mechanical behaviors of SiC_xN_y thin films strongly depended on nitrogen content. SiC_0.70 exhibited a mixture consisting of SiC, Si and a small amount of C. Incorporated nitrogen, on one hand linked to Si, forming SiN_x, on the other hand produced CN_x and C at the expense of SiC. As a result, an amorphous mixture consisting of SiC, SiN_x, C and CN_x were produced. Such effects were enhanced with increase of nitrogen content. A low hardness of about 16.5 GPa was obtained at nitrogen-free SiC_0.70. Incorporation of nitrogen or increase of nitrogen content increased the film hardness. A microhardness maximum of ∼29 GPa was obtained at a nitrogen content of 15.7 at.%. This value was decreased with further increase of N content, and finally a hardness value of ∼22 GPa was obtained at a N content of ∼25 at.%. The residual compressive stress was consistent with the hardness in the nitrogen content range of 8.6-25.3 at.%.     

Chemical bath-deposited ZnS thin films: Preparation and characterization

Chemical bath deposition of ZnS thin films from NH₃/SC(NH₂)₂/ZnSO₄ solutions has been studied. The effect of various process parameters on the growth and the film quality are presented. The influence on the growth rate of solution composition and the structural, optical properties of the ZnS thin films deposited by this method have been studied. The XRF analysis confirmed that volume of oxygen of the as-deposited film is very high. The XRD analysis of as-deposited films shows that the films are cubic ZnS structure. The XRD analysis of annealed films shows the annealed films are cubic ZnS and ZnO mixture structure. Those results confirmed that the as-deposited films have amorphous Zn(OH)₂. SEM studies of the ZnS thin films grown on various growth phases show that ZnS film formed in the none-film phase is discontinuous. ZnS film formed in quasi-linear phase shows a compact and a granular structure with the grain size about 100 nm. There are adsorbed particles on films formed in the saturation phase. Transmission measurement shows that an optical transmittance is about 90% when the wavelength over 500 nm. The band gap (E_g) value of the deposited film is about 3.51 eV.     

Probing the ferroelectric phase transition in sol–gel‐derived polycrystalline bismuth ferrite thin films

Polycrystalline BiFeO₃ (BFO) thin films were successfully grown on Pt/Ti/SiO₂/Si(100) and SrTiO₃ (STO) (100) substrates using the chemical solution deposition (CSD) technique. X‐ray diffraction (XRD) patterns indicate the polycrystalline nature of the films with rhombohedrally distorted perovskite crystal structure. Differential thermal analysis (DTA) was performed on the sol–gel‐derived powder to countercheck the crystal structure, ferroelectric (FE) to paraelectric (PE) phase transition, and melting point of bismuth ferrite. We observed a significant exothermic peak at 840 °C in DTA graphs, which corresponds to an FE–PE phase transition. Raman spectroscopy studies were carried out on BFO thin films prepared on both the substrates over a wide range of temperature. The room‐temperature unpolarized Raman spectra of BFO thin films indicate the presence of 13 Raman active modes, of which five strong modes were in the low‐wavenumber region and eight weak Raman active modes above 250 cm⁻¹. We observed slight shifts in the lower wavenumbers towards lower values with increase in temperature. The temperature‐dependent Raman spectra indicate a complete disappearance of all Raman active modes at 840 °C corresponding to the FE–PE phase transitions. There is no evidence of soft mode phonons. Copyright © 2008 John Wiley & Sons, Ltd.