Structural,electrical and optical properties of p-type transparent conducting SnO2:Al film derived from thermal diffusion of Al/SnO2/Al multilayer thin films

Highly transparent, p-type conducting SnO₂:Al films derived from thermal diffusion of a sandwich structure Al/SnO₂/Al multilayer thin films deposited on quartz substrate have been prepared by direct current and radio-frequency magnetron sputtering using Al and SnO₂ targets. The deposited films were annealed at various temperatures for different durations. The effect of thermal diffusing temperature and time on the structural, electrical and optical performances of SnO₂:Al films has been studied. X-ray diffraction results show that all p-type conducting films possessed polycrystalline SnO₂ with tetragonal rutile structure. Hall-effect results indicate that 450 °C for 4 h were the optimum annealing parameters for p-type SnO₂:Al films, resulting in a relatively high hole concentration of 7.2 × 10¹⁸ cm^?3 and a low resistivity of 0.81 Ω cm. The transmission of the p-type SnO₂:Al films was above 80%.     

The influence of the transformation of electronic structure and micro-structure on improving the thermoelectric properties of zinc antimonide thin films

Measurements of electronic structure, microstructure and thermoelectric properties of zinc antimonide thin films prepared by direct current magnetron co-sputtering were carried out. The as-deposited zinc antimonide thin film had a very high resistivity similar to insulating ceramics, which was due to a low binding energy of both zinc and antimony, with the electron scattering increases and impedes the current transport. With the increase in annealing temperature, the films became more crystalline and the thermoelectric properties were also improved. The resistivity of the film decreased rapidly with its crystallinity when the annealing temperature was above 350 °C. The Seebeck coefficients of the thin films were positive, indicating that the films were P-type. The Seebeck coefficient of those samples increased with increasing annealing temperature. The thin film annealed at 400 °C has an optimal power factor of 1.87 × 10⁻³ Wm⁻¹ K⁻² with a Seebeck coefficient of 300 μVK⁻¹ and a resistivity of 4.82 × 10⁻⁵ Ωm at 573 K.     

Effects of defects generated in ALD TiO<Subscript>2</Subscript> films on electrical properties and interfacial reaction in TiO<Subscript>2</Subscript>/SiO<Subscript>2</Subscript>/Si system upon annealing in vacuum

Thin TiO₂ layers grown at 130°C on SiO₂-coated Si substrates by atomic layer deposition (ALD) using TTIP and H₂O as precursors were annealed, and the effects of the annealing temperature on the resulting electrical properties of TiO₂ and the interface properties between a Pt electrode and TiO₂ were examined using transmission line model (TLM) structures. The as-deposited TiO₂ thin film had an amorphous structure with OH groups and a high resistivity of 6×10³Ω-cm. Vacuum annealing at 700 °C transformed the amorphous film into an anatase structure and reduced its resistivity to 0.04Ω-cm. In addition, the vacuum-annealing of the TiO₂/SiO₂ structure at 700°C produced free silicon at the TiO₂-SiO₂ interface as a result of the reaction between the Ti interstitials and SiO₂. The SiO₂ formed on the TiO₂ surface caused a Schottky contact, which was characterized by the TLM method. The use of the TLM method enabled the accurate measurement of the resistivity of the vacuum-annealed TiO₂ films and the characterization of the Schottky contacts of the metal electrode to the TiO₂.     

Thermal stability of tungsten nitride films deposited by reactive magnetron sputtering

The studies of thermal stability of nitride coatings are important since their structural, thermal, electrical and optical properties are drastically modified by the oxidation layer formed on the top of these coatings. Tungsten nitride films were deposited from metallic tungsten target using reactive pulsed d. c. magnetron sputtering. The films were annealed in air at different temperatures for 1 h. The structural, electrical resistivity and optical properties of the annealed films were analyzed. Besides the film analysis, powder of tungsten nitride was obtained by scratching the coating from the glass substrates. The oxidation kinetics of the scratched powder was studied using simultaneous thermal gravimetric/deferential thermal analysis measurements. X-ray diffraction patterns revealed that W₂N oxidizes to the two different phases WO₃ and WO_2.92. The oxide diffraction peaks appeared upon annealing at 773 K and the relative intensities increased with annealing temperature. The tungsten nitride was found to oxidize according a parabolic relation between mass gain and oxidation time. The activation energy of oxidation was evaluated by analyzing the Arrhenius relation from the temperature dependence of the weight gain. The obtained value was 1.76 eV. The activation energies of crystallization of the two phases were calculated. The electrical resistivity was found to increase drastically upon oxidation. The optical properties of the films are very sensitive to the oxidation temperature. The optical band gap values for the film oxidized at 773 K and 823 K are 2.71 and 2.58 eV, respectively.     

Annealing time dependent structural,morphological, optical and electrical properties of RF sputtered p-type transparent conducting SnO2/Al/SnO2 thin films

Transparent p-type conducting SnO₂/Al/SnO₂ multilayer films were fabricated on quartz substrates by radio frequency (RF) sputtering using SnO₂ and Al targets. The deposited films were annealed at a fix temperature of 500 °C for different time durations (1–8 h). The effect of annealing time on the structural, morphological, optical and electrical performances of SnO₂/Al/SnO₂ multilayer films was studied. X-ray diffraction (XRD) results show that all the p-type conducting films possess polycrystalline SnO₂ with tetragonal rutile structure. Hall-effect results indicate that 500 °C for 1 h is the optimum annealing condition for p-type SnO₂/Al/SnO₂ multilayer films, resulting in a hole concentration of 1.14×10¹⁸ cm^–3 and a low resistivity of 1.38 Ω·cm, respectively. The optical transmittance of the p-type SnO₂/Al/SnO₂ multilayer films is above 80% within annealing time range of 1–8 h, showing maximum for the films annealed for 1 h.     

Elaboration and characterization of nanocrystalline TiO2 thin films prepared by sol–gel dip-coating

Nanocrystalline TiO₂ thin films were deposited on a ITO coated glass substrate by sol–gel dip coating technique, the layers undergo a heat treatment at temperatures varying from 300 to 450 °C. The structural, morphological and optical characterizations of the as deposited and annealed films were carried out using X-ray diffraction (XRD), Raman spectroscopy, Atomic Force Microscopy (AFM), visible, (Fourier-Transform) infrared and ultraviolet spectroscopy, Fluorescence and spectroscopic ellipsometry. The results indicate that an anatase phase structure TiO₂ thin film with nanocrystallite size of about 15 nm can be obtained at the heat treatment temperature of 350 °C or above, that is to say, at the heat treatment temperature below 300 °C, the thin films grow in amorphous phase; while the heat treatment temperature is increased up to 400 °C or above, the thin film develops a crystalline phase corresponding to the titanium oxide anatase phase. We have accurately determined the layer thickness, refractive index and extinction coefficient of the TiO₂ thin films by the ellipsometric analysis. The optical gap decreases from 3.9 to 3.5 eV when the annealing temperature increases. Photocatalytic activity of the TiO₂ films was studied by monitoring the degradation of aqueous methylene blue under UV light irradiation and was observed that films annealed above 350 °C had good photocatalytic activity which is explained as due to the structural and morphological properties of the films.     

Ferroelectric properties of dysprosium-doped Bi4Ti3O12 thin films crystallized in various atmospheres

Dysprosium-doped Bi4Ti3O12 （Bi3.4Dy0.6Ti3O12, BDT） ferroelectric thin films were deposited on Pt（111）/Ti/SiO2/Si（111） substrates by chemical solution deposition （CSD） and crystallized in nitrogen, air and oxygen atmospheres, respectively. X-ray diffraction （XRD） and scanning electron microscopy （SEM） were used to identify the crystal structure, the surface and cross-section morphology of the deposited ferroelectric films. The results show that the crystallization atmosphere has significant effect on determining the crystallization and ferroelectric properties of the BDT films. The film crystallized in nitrogen at a relatively low temperature of 650 ℃, exhibits excellent crystallinity and ferroelectricity with a remanent polarization of 2Pr = 24.9 ℃/cm^2 and a coercive field of 144.5 kV/cm. While the films annealed in air and oxygen at 650 ℃ do not show good crystallinity and ferroelectricity until they are annealed at 700 ℃. The structure evolution and ferroelectric properties of BDT thin films annealed under different temperatures （600-750 ℃） were also investigated. The crystallinity of the BDT films is improved and the average grain size increases when the annealing temperature increases from 600 ℃ to 750 ℃ at an interval of 50 ℃. However, the polarization of the films is not monotonous function of the annealing temperature.     

Characterization of rapid thermally processed LiMn204 thin films derived from solution deposition

Cathode material LiMn₂O₄ thin films were prepared through solution deposition followed by rapid thermal annealing. The phase identification and surface morphology were studied by X-ray diffraction and scanning electron microscopy. Electrical and electrochemical properties were examined by four-probe method, cyclic voltammetry and galvanostatic charge-discharge experiments. The results show that the film prepared by this method is homogeneous, dense and crack-free. As the annealing temperature and annealing time increase, the electronic resistivity decreases, while the capacity of the films increases generally. For the thin films annealed at different temperatures for 2 min, the thin film annealed at 800 °C has the best cycling behavior with the capacity loss of 0.021% per cycle. While for the thin films annealed at 750 °C for different times, the film annealed for 4 min possesses the best cycling performance with a capacity loss of 0.025% per cycle. For the lithium diffusion coefficient in LiMn₂O₄ thin film, its magnitude order is 10⁻¹¹ cm²·s⁻¹.     

Effect of annealing temperature on optical band-gap of amorphous indium zinc oxide film

The effect of annealing temperature on the electrical and optical properties of indium zinc oxide (IZO) (In₂O₃:ZnO = 90:10 wt.%) thin films has been investigated. The IZO thin films were deposited on glass substrates by radio frequency magnetron sputtering and then subjected to annealing in a mixed ambient of air and oxygen at 100, 200 and 300 °C. All the IZO films were found to have amorphous structure. With the increase of the annealing temperature, the carrier concentration decreased and the resistivity increased. The average transmittance of IZO thin films decreased slightly with annealing temperature. Interestingly, a systematic reduction of the optical band-gap from 3.79 eV to 3.67 eV was observed with annealing temperature. The change in optical band-gap was observed to be caused predominantly by Burstein-Moss band-gap widening effect suggesting unusual absence of band narrowing effect. The effects on optical and electrical properties of IZO films have been discussed in detail.     

The effects of vacuum annealing on the structure of VO2 thin films

Noncrystalline VO_x thin films were deposited onto p-doped Si (100) substrates at 400 °C using magnetron sputtering. By vacuum annealing, we obtained polycrystalline VO₂ thin films with two different structures under a variety of annealing conditions. With the annealing temperature increasing and the annealing time developing, structures of the films underwent the following transformation: amorphous structure→metastable VO₂ (B)→VO₂ (B) + VO₂ (M). Vacuum annealing is useful of acquiring VO₂ thin films with high surface quality, but too high annealing temperature (500 °C) and too long time (15 h) are harmful, which make the surface degenerate.     

P-type transparent conducting SnO2:Zn film derived from thermal diffusion of Zn/SnO2/Zn multilayer thin films

Highly transparent, p-type conducting SnO₂:Zn thin films are prepared from the thermal diffusion of a sandwich structure of Zn/SnO₂/Zn multilayer thin films deposited on quartz glass substrate by direct current (DC) and radio frequency (RF) magnetron sputtering using Zn and SnO₂ targets. The deposited films were annealed at various temperatures for thermal diffusion. The effect of annealing temperature and time on the structural, electrical and optical performances of SnO₂:Zn films was studied. XRD results show that all p-type conducting films possessed polycrystalline SnO₂ with tetragonal rutile structure. Hall effect results indicate that the treatment at 400 °C for 6 h was the optimum annealing parameters for p-type SnO₂:Zn films which have relatively high hole concentration and low resistivity of 2.389 × 10¹⁷ cm^− 3 and 7.436 Ω cm, respectively. The average transmission of the p-type SnO₂:Zn films was above 80% in the visible light range.     

Amorphous hafnium oxide thin films for antireflection optical coatings

Hafnium oxide (HfO₂) thin films were grown on silicon and quartz substrates by radio frequency reactive magnetron sputtering at temperature < 52 °C. X-ray diffraction of the films showed no structure, suggesting that the films grown on the substrates are amorphous. The optical properties of these films have been investigated using spectroscopic ellipsometry with wavelength range 200-1400 nm and ultraviolet-visible spectrophotometer techniques. Also, the effects of annealing temperatures on the structure and optical properties of the amorphous HfO₂ (a-HfO₂) have been investigated. The films appeared to be monoclinic structure upon high temperature (1000 °C) annealing as confirmed by X-ray diffraction. The results show that the annealing temperature has a strong effect on the optical properties of a-HfO₂ films. The optical bandgap energy of the as-deposited films is found to be about 5.8 eV and it increases to 5.99 eV after the annealing in Ar gas at 1000 °C. The further study shows that the measurement of the optical properties of the amorphous films reveals a high transmissivity (82%-99%) and very low reflectivity (< 8%) in the visible and near-infrared regions at any angle of incidence. Thus, the amorphous structure yields HfO₂ film of significantly higher transparency than the polycrystalline (68%-83%) and monoclinic (78%-89%) structures. This means that the a-HfO₂ films could be a good candidate for antireflection (AR) optical coatings.     

Defect and electronic structures in TiSi2 thin films produced by co-sputtering: Part 1: Defect analysis by transmission electron microscopy

Phase transformation and defect structures in thin-film TiSi₂ produced by co-sputtering have been investigated as a function of annealing temperature by transmission electron microscopy. Metastable C49 crystallites nucleate first in the amorphous matrix from as low as 100°C. This is due to the lower surface energy of C49 crystallites arising from the similarity in electronic structure, chemical bonding and atomic density between the C49 and amorphous modifications. All C49 crystallites contain numerous (010) faults, which are boundaries between two differently oriented domains related to each other by a 90° rotation about [010]. Stable C54 crystallites nucleate in the C49 matrix above 700°C and most C54 crystallites contain twins with the twin habit plane parallel to (001), which is perpendicular to the {110} twinning plane. Ternary additions to TiSi₂ thin films to reduce the C49→C54 transformation temperature are discussed on the basis of the results from electron energy-loss spectroscopy (EELS) analyses described in the companion paper.     

Effects of annealing temperature and time on microstructure and magnetic properties of Pr-Co thin films

A series of Pr-Co thin films were deposited on the Si (100) substrates with Cr underlayer by magnetron sputtering. The effects of both the post-annealing temperature and the annealing time on the microstructure and magnetic properties for the Pr-Co films were studied systemati- cally. The as-deposited Pr-Co thin films are mostly amorphous and tend to crystallize after annealing at temperatures above 600 C. When the annealing time is increased, the films show a complicated structure with various phases coexisting. Accordingly, the as-deposited film and low temperature annealed films are soft magnets and films annealed at temperatures beyond 600 C tend to be hard magnets. When the annealing time is increased from 5 min to 2 h, the films transfer from hard magnets to soft again. The sample annealed at 600 C for 10 min shows the largest coercivity of 0.59 T.     

Effect of annealing on pulsed laser deposited zirconium oxide thin films

Zirconium oxide thin films were deposited using pulsed laser ablation from a ceramic ZrO₂ target on unheated substrates. Subsequently, the films were annealed in air in the temperature range 400-800 °C. The films were characterized by X-ray diffraction, atomic force microscopy, X-ray photoelectron spectroscopy, and optical spectroscopy to investigate the variation of the structural, chemical, and optical properties upon annealing. As-deposited films were amorphous and had a large surface density of ablated particles. Annealing resulted in the growth of monoclinic nano-crystalline, uniform, and transparent films that were slightly sub-stoichiometric. The annealed films were compact and had high values of the refractive index. Extinction coefficients were small, and may be related to the presence of defects. The films exhibited the presence of an indirect band gap, related to defects, and a direct band gap, related to fundamental absorption.     

Influence of Annealing Temperature on the Microstructure and Electrical Properties of Indium Tin Oxide Thin Films

Indium tin oxide(ITO) thin films were prepared on alumina ceramic substrates by radio frequency magnetron sputtering.The samples were subsequently annealed in air at temperatures ranging from 500 to 1,100 °C for 1 h.The influences of the annealing temperature on the microstructure and electrical properties of the ITO thin films were investigated,and the results indicate that the as-deposited ITO thin films are amorphous in nature.All samples were crystallized by annealing at 500 °C.As the annealing temperature increases,the predominant orientation shifts from(222)to(400).The carrier concentration decreases initially and then increases when the annealing temperature rises beyond1,000 °C.The resistivity of the ITO thin films increases smoothly as the annealing temperature increases to just below900 °C.Beyond 900 °C,however,the resistivity of the films increases sharply.The annealing temperature has a significant effect on the stability of the ITO/Pt thin film thermocouples(TFTCs).TFTCs annealed at 1,000 °C show improved hightemperature stability and Seebeck coefficients of up to 77.73 μV/°C.     

Recent studies on photoconductive thin films of binary compounds

In this paper a review of recent progress achieved in the domain of MX₂ films (M=Mo, W; X=Se, S) is presented. The MoS₂ is essentially discussed. It is shown that the emerging interest in the use of MX₂ thin films as absorbing layer in photovoltaic cells has induced significant improvements of the crystalline and optoelectrical properties of these films. Some years ago the films obtained were crystallized in the 2H-MoS₂ structure but the size of their crystallites was small and the samples were poorly photoconductive. Recently many works have shown that, whatever the deposition technique used, textured films with large grains and good photoconductive properties could be obtained when a thin nickel layer is used. During the post annealing treatment, this thin nickel layer diffuses all over the thickness of the films. It is proposed that systematically the crystallization process of MX₂ films is a two-step process. The primary crystallization corresponds to small crystallites formation and the secondary crystallization corresponds to large ordered domains growth by coalescence of the small crystallized domains. This secondary crystallization process is facilitated by the presence of Van der Waals surfaces parallel to the plane of the substrate. Moreover, this effect is strongly improved in the presence of nickel which allows the obtention of high quality films. The electrical properties of these films are interpreted with the help of grain boundary theories.     

Photoluminescence in laser ablated nanostructured indium oxide thin films

Nanocrystalline indium oxide films have been deposited using pulsed laser ablation technique at different substrate temperatures and the films are post-annealed at different temperatures. The structural, optical and electrical properties of the films are investigated by XRD, SEM, AFM, UV–vis spectra, photoluminescence spectra and electrical conductivity measurements. X-ray diffractograms of the as-deposited and post-annealed films A–C show that films are amorphous at lower substrate temperatures and transform to mixture of amorphous and crystalline phases. The grain size determination based on Debye Scherrer's formula shows that the average grain size of the crystallites in the films ranges from 6 to 32 nm. Dislocation density, biaxial strain, lattice strain and lattice stress of the films are also calculated. SEM micrographs show that all the films are densely packed with the crystallites in the nanodimensions. SEM images show porous nanocrystalline nature for the films of samples B and C which make them suitable for gas sensing. The as-deposited samples show decrease in resistivity with increase in substrate temperature and the lowest resistivity obtained is 6.6 × 10^?5 Ω m for the as-deposited films at substrate temperature 773 K. Efficient photoluminescence emission is observed in all the films and this can be attributed to higher values of rms surface roughness exhibited by these films. In₂O₃ films exhibit a PL emission property in the UV region at room temperature which suggests possible applications in nanoscale optoelectronic devices in the future.     

Nanocrystalline LiMn2O4 thin film cathode material prepared by polymer spray pyrolysis method for Li-ion battery

Nanocrystalline cubic spinel lithium manganese oxide thin film was prepared by a polymer spray pyrolysis method using lithium acetate and manganese acetate precursor solution and polyethylene glycol-4000 as a polymeric binder. The substrate temperature was selected from the thermogravimetric analysis by finding the complete crystallization temperature of LiMn₂O₄ precursor sample. The deposited LiMn₂O₄ thin films were annealed at 450, 500 and 600 °C for 30 min. The thin film annealed at 600 °C was found to be the sufficient temperature to form high phase pure nanocrystalline LiMn₂O₄ thin film. The formation of cubic spinel thin film was confirmed by X-ray diffraction study. Scanning electron microscopy and atomic force microscopy analysis revealed that the thin film annealed at 600 °C was found to be nanocrystalline in nature and the surface of the films were uniform without any crack. The electrochemical charge/discharge studies of the prepared LiMn₂O₄ film was found to be better compared to the conventional spray pyrolysed thin film material.     

Annealing temperature dependence of the optical and structural properties of selenium-rich CdSe thin films

Structural and optical properties of selenium-rich CdSe (SR-CdSe) thin films prepared by thermal evaporation are studied as a function of annealing temperature. X-ray diffraction (XRD) patterns show that the as-prepared films were amorphous, whereas the annealed films are polycrystalline. Analyzing XRD patterns of the annealed films reveal the coexistence of both (hexagonal) Se and (hexagonal) CdSe crystalline phases. Surface roughness of SR-CdSe films is measured using atomic force microscope (AFM). Analyses of the absorption spectra in the wavelength range (200-2500 nm) of SR-CdSe thin films indicates the existence of direct and indirect optical transition mechanisms. The optical band gap (E_g) of as-prepared film is 1.92 and 2.14 eV for the indirect allowed and direct allowed transitions respectively. After annealing, the absorption coefficient and optical band gap were found to decrease, while the values of refractive index (n) and the extinction coefficient (k_ex) increase. The dispersion of the refractive index is described using the Wimple-Di Domenico (WDD) single oscillator model and the dispersion parameters are calculated as a function of annealing temperature. Besides, the high frequency dielectric constant (?_∞) and the ratios of the free carrier concentration to its effective mass (N/m*) are studied as a function of annealing temperature. The results are discussed and correlated in terms of amorphous-crystalline transformations.