Spray Pyrolysis Deposition Technique Research Articles

Structural, optical and electrical properties of Cu:MnO2 nanostructured thin films for glucose sensitivity measurements

In the present investigation, pure MnO2 and Cu doped MnO2 (Cu:MnO2) thin films were successfully prepared by the spray pyrolysis deposition technique. Different Cu concentrations were used to analyze the morphological, structural, optical, electrical properties and as well glucose sensitivity measurement has been performed. MnO2 doped with Cu induces microstructure and is set in the lattice by keeping Mn+2 leading to the micro spherical shape of the samples highlighted from a scanning electron microscope. X-ray diffraction analysis has confirmed the tetragonal MnO2 crystal structure with α-phase. The crystallite size, crystal structure, texture, and nanoparticle formation in MnO2 films have been influenced by Cu dopant. The maximum optical transmittance is found to be about 83%. The energy band gap associated with the allowed direct transition is found to increase from 3.82 to 3.96 eV with increasing Cu doping concentration up to 4 at%. Glucose sensitivity was measured by the four-probe technique. Notably, 4 at% Cu:MnO2 films have demonstrated the superior sensing ability of glucose of 29%.

Spray Angle Dependence for the Growth of Terrace-truncated Nanocone Structure of Gallium-doped Zinc Oxide by Advanced Spray Pyrolysis Deposition Technique

Spray Angle Dependence for the Growth of Terrace-truncated Nanocone Structure of Gallium-doped Zinc Oxide by Advanced Spray Pyrolysis Deposition Technique

Al0.75Ga0.25N/AlxGa1-xN/Al0.75Ga0.25N/AlN/SiC Metal–Oxide–Semiconductor Heterostructure Field-Effect Transistors With Symmetrically-Graded Widegap Channel

Novel Al 0.75 Ga 0.25 N/Al x Ga 1-x N/Al 0.75 Ga 0.25 N/AlN metal-oxide-semiconductor heterostructure field-effect transistors (MOS-HFETs) with symmetrically-graded widegap Al x Ga 1-x N channel (x = 0.75 → 0.25 → 0.75) grown on a SiC substrate are investigated. Al 2 O 3 was devised as the gate dielectric by using a non-vacuum ultrasonic spray pyrolysis deposition (USPD) technique. Device characteristics with respect to different etch depths of the source/drain recesses were studied. For a 2-μm gate length (L G ), the present widegap V-shape-channel MOS-HFET has shown improved maximum drain-source current density (I DS,max ) of 299.3 A/mm at V DS = 20 V, I DS density at V GS = 0 V (I DSS0 ) of 153.9 mA/mm, on/off-current ratio (I on /I off ) of 1.4 × 10 7 , extrinsic transconductance (g m , max ) of 16.7 mS/mm, two-terminal off-state gate-drain breakdown voltage (BV GD ) of -379 V, and three-terminal on-state drain-source breakdown voltage (BV DS ) of 339 V. Besides, superior deep-UV sensing performance with high spectral responsivity (SR) of 1780 (810.2) A/W at wavelength λ = 250 (300) nm are also achieved.

Enhancement of Solar Cell Efficiency by Using TiO2 Nanostructure Doped Fe2O3 Dye and Effect Concentration of Solvent on Optical Properties

Solar energy has the greatest potential of all the sources of renewable energy, as only a small amount of this form of energy could be used, especially when other sources (coal, oil or gas) in the country have depleted. A solar cell is a solid electrical device that converts solar energy directly to electricity. Hybrid solar cells based on inorganic and organic compounds are a promising renewable energy source.
 Aims: The aim of this study was to prepare a nanostructured thin film of titanium oxide: doped iron oxide for enhancement of solar cell efficiency. In addition to studying the effect doped on optical properties of titanium oxide nanostructure thin film.
 Study Design: The spray pyrolysis deposition method used for preparation the nanostructure material.
 Place and Duration of Study: This study was conducted in the department of physics and department of materials sciences, Al-neelain university, between January 2016 and January 2019.
 Methodology: Thin films of Titanium Oxide (TiO2) doped Iron Oxide (Fe2O3) have been prepared by chemical spray pyrolysis deposition technique. A laboratory designed glass atomizer was used for spraying the aqueous solution. Which has an output nozzle about 1mm then the film was deposited on preheated cleaned glass substrates at the temperature of 400ºC. we used different concentration to study optical parameters. A 1.5 g TiO2 powder of anatase structure doped with 1.5 g of Fe2O3 was mixed with 2 ml of ethanol and stirred using a magnetic stirrer for 30 minutes to form TiO2 paste to obtain the starting solution for deposition and spray time was 10 s and spray interval 2 min was kept constant. The carrier gas (filtered compressed air) was maintained at a pressure of 105 Nm-2, and distance between nozzle and substrate was about 30 cm ± 1 cm. The thickness of the sample was measured using the weighting method and was found to be around 400 nm. Optical transmittance and absorbance were records in the wavelength range of (200-1100) nm using UV-Visible spectrophotometer (Shimadzu Company Japan).
 Results: The results obtained showed that the optical band gap decreased from 5.58 eV before doping to (3.9, 3.81, 3.81 and 3.81 eV) after doped for TiO2:Fe2O3 thin films, this result refers to the broadening of secondary levels that product by TiO2: doping to the Fe2O2 thin films. Also, the results showed the variation of refractive index with wavelength for different concentration after doped of TiO2:Fe2O3 films from this figure, it is clear that n decrease with low concentration and increase with high concentration after doped that mean the density is decreased of this films. In addition the extinction coefficient of TiO2:Fe2O3 thin films recorded before doped and with different concentration (1.1, 1.2, 1.5 and 1.6 mol/L) and in the range of (300 – 1200) nm and after doped it observed from that the extinction coefficient, decrease sharply with the increase of wavelength for all prepared films and all the sample after doped is interference between them accept the sample before annealing is far from the other sample.
 Conclusion: Based on the results obtained doping of titanium oxide increases the efficiency of TiO2 thin film in DSSC. It also proves that the fabrication of TiO2 thin films by spray pyrolysis deposition method is successful.

Effect of Annealing Temperature in Improvement the Optical Properties of TiO2 Doped Fe2O3 to Use in Thin Film

Solar energy is already has being widely successfully used in residential and industrial setting for thermal and electrical application such as space technology, communication, etc. I.
 Aims: The aim of this study the effect of the annealing temperature in improvement optical properties of titanium oxide nanostructure doped iron oxide for use in thin film.
 Study Design: The spray pyrolysis deposition method used for preparation the nanostructure material.
 Place and Duration of Study: This study was conducted in department of physics and department of materials sciences, Al-Neelain University, between January 2016 and January 2019. 
 Methodology: Thin films of Titanium Oxide (TiO2) doped Iron Oxide (Fe2O3) have been prepared by chemical spray pyrolysis deposition technique. A laboratory designed glass atomizer was used for spraying the aqueous solution. Which has an output nozzle about 1 mm. then film were deposited on preheated cleaned glass substrates at temperature of 400°C. we used different concentration to study optical parameters. A 1.5 g TiO2 powder of anatase structure doped with 1.5 g of Fe2O3 was mixed with 2 ml of ethanol and stirred using a magnetic stirrer for 30 minutes to form TiO2 paste to obtain the starting solution for deposition and spray time was 10 s and spray interval 2 min was kept constant. The carrier gas (filtered compressed air) was maintained at a pressure of 105 Nm-2, and distance between nozzle and substrate was about 30 cm ± 1 cm. Thickness of sample was measured using the weighting method and was found to be around 400nm. Optical transmittance and absorbance were record in wavelength range of (200-1100) nm using UV-Visible spectrophotometer (Shimadzu Company Japan).
 Results: The results obtained showed that the optical band gap decreased from 5.6eV before annealing to (3.9, 3.26, 3.24 and 3.27 eV) after annealing temperature at(450° – 500°) for TiO2:Fe2O3 thin films, this result refer to the broadening of secondary levels that product by TiO2: doping to the Fe2O2thin films. Also the results showed the variation of refractive index with wavelength for different concentration after annealing temperature at (450° – 500°) of TiO2: Fe2O3 films from this figure, it is clear that n decrease with low concentration and increase with high concentration after annealing temperature that mean the density is decreased of this films. In addition the extinction coefficient of TiO2:Fe2O3 thin films recorded before annealing and with different concentration (1.1, 1.2, 1,5 and 1,6) and in the range of (300 – 1200) nm and at annealing temperature from (450° – 500°). It observed from that the extinction coefficient, decrease sharply with the increase of wavelength for all prepared films and all the sample after annealing is interference between them accept the sample before annealing is far from the other sample.
 Conclusion: The TiO2 thin film shows better result after annealing; By exposing temperature during annealing process degree at (450o- 500o) is found to be the best temperature for annealing TiO2 thin film. The study concluded that an annealing temperature Contributes to the improvement of optical properties related to increasing the efficiency of the solar cell, especially the refractive index, energy gap, extinction coefficient.

Synthesis and characterization of Al-doped ZnO terrace-truncated nanocone structure by the advanced spray pyrolysis deposition technique

We have synthesized a terrace-truncated nanocone structure of Al-doped ZnO using the advanced spray pyrolysis deposition technique. In this study, we proposed the growth mechanism of a terrace-truncated nanocone structure. The average top diameter is 35–40 nm and the height of the structure varies between 600–650 nm. The nanostructure was favored along the c-axis as confirmed by X-ray diffraction patterns. The electrical conductivity and optical transmittance in the visible range are 5.1 × 103 Ω−1 cm−1 and 80%, respectively. The proposed terrace-truncated nanocone structure of Al-doped ZnO has suitable characteristics for use as a transparent conductive oxide material.

Impact of Trivalent Metal Ion Doping on Structural, Photoluminescence and Electric Properties of NiFe2O4 Thin Films

Nickel aluminum ferrite thin films of chemical formula NiFe2−xAlxO4 (0.0 ≤ x ≤ 1.0 in the step 0.2) were deposited on glass substrate using the spray pyrolysis deposition technique. The x-ray diffraction patterns exhibited single phase cubic spinel structure with space group Fd-3m. The Fourier-transform infrared spectroscopy (FTIR) spectra shows fundamental absorption bands related to octahedral and tetrahedral sites. The average surface roughness of all the thin films was estimated from AFM study, and is found on the order of 13–52 nm. The grain size is in nanosize dimensions and distributed homogeneously over the surface of the thin film to analyze by the FE-SEM. The PL spectra obtained at room temperature showed the characteristic near-band-edge emission at around 680 nm and 780 nm. The DC electrical resistivity (ρdc) as the function of temperature was studied for various Al3+ substitutions that indicated the decreasing trend with the increasing temperature, which exhibited a semiconducting nature of thin film. The dielectric properties decreased with increase in the Al3+ ions. The dielectric behavior of Al3+ substituted nickel ferrite thin films was explained by using Koop’s phenomenological model. The dielectric parameters, such as the dielectric constant (e′), dielectric loss (e″) and loss tangent (tan δ) decreased with increase in the Al3+ ions substitution as well as showing normal behavior with frequency.

Palladium enriched tungsten oxide thin films: an efficient gas sensor for hazardous gases

Palladium enriched tungsten trioxide thin films were prepared by spraying solution of ammonium tungstate as a precursor on glass substrates using spray pyrolysis deposition technique. Palladium chloride as a precursor for palladium was introduced in the precursor solution during refluxing process before deposition. The catalyst Pd with different concentrations was introduced on series of WO3 films. X-ray diffractometry (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and Raman spectroscopy were applied to analyze structure and morphology of the deposited thin films. The effect of Pd enrichment on the microstructure, electrical and gas sensing properties of the as-synthesized WO3 thin films was studied. Variation in the electrical conductivity of pure and Pd supplemented WO3 films was measured in air and in the presence of hazardous gases such as NO2, SO2 and NH3. The addition of 3 w/o Pd in WO3 raised the gas response of the film to 1.1 towards NO2 at lowest operating temperature of 100 °C. The film shows adequate response towards SO2 (0.32) and NH3 (0.27) at 200 °C and 225 °C, respectively. The response and recovery time ranged in 0.5–1.25 s and 1–6.7 s respectively even for high gas concentrations upto 750 ppm.

Temperature dependence of Raman spectra and first principles study of NiMn2O4 magnetic spinel oxide thin films. Application in efficient photocatalytic removal of RhB and MB dyes.

Magnetic spinel oxide NiMn2O4 thin films were grown on glass substrates using the spray pyrolysis deposition technique at 350 °C. First, structural optimization, electronic structure and vibrational properties were obtained for NiMn2O4 by density functional theory (DFT) with an all electron basis set and the hybrid functional B3LYP implemented in the CRYSTAL14 code. Our DFT results show good agreement with previous experimental and theoretical data. Second, Raman spectra of as-prepared thin films have been measured over the temperature range from 100 K to 620 K. We report on the temperature dependence of their dominant first-order scattering F2g and A1g phonons modes. The phonon dynamic behavior is well described by a model taking into account explicit lattice anharmonicity associated to both cubic and quartic phonon decay processes and thermal expansion related quasiharmonicity. Finally, the photocatalytic activities of the obtained thin films were evaluated through the photocatalytic degradation of Rhodamine B (RhB) and methylene blue (MB) solutions under solar light irradiation as a function of time. All the results indicate that NiMn2O4 thin film can be used as a potential solar-light-driven photocatalyst.

Synthesis, characterization, and optical properties of copper oxide thin films obtained by spray pyrolysis deposition


 
 
 
 Copper oxide thin films were synthesized by using spray pyrolysis deposition technique, in the temperature around 400°C in atmosphere from alcoholic solutions. Copper (II) chloride as precursor and glass as a substrate. The textural and structural properties of the films were characterized by atomic force microscopy (AFM), X-ray diffraction (XRD). The average particle size determined from the AFM images ranged from 30 to 90 nm and the roughness average was equal to 9.3 nm. The XRD patterns revealed the formation of a polycrystalline hexagonal CuO. The absorption and transmission spectrum, band gap, film thickness was investigated. The films were tested as an optical limiter. The experiments were performed using Q-switched Nd:YAG laser at 532nm and 1064 nm at different intensities. Copper oxide thin films appear to be attractive candidates for optical limiting application and sensor application.
 
 
 

Synthesis and physical characterization of Sr2FeMoO6 and Sr3FeMoO7 thin films

Quaternary oxides based on strontium, iron, and molybdenum elements such as Sr2FeMoO6 (SFMO) and its analog n = 2 Ruddlesden-Popper (R-P) phase Sr3FeMoO7 were synthesized using chemical spray pyrolysis deposition technique. Optical band gap values, thermal conductivity and thermal diffusivity of both spray-deposited films were investigated. The results confirm that the above properties are considerable factors in forecasting the appropriate perovskite compound for future thermal barrier coating applications.

Effect of low level nozzle height on properties of copper oxide absorption layer prepared by fully computerized spray pyrolysis depositions

The effect of approaching nozzle jet from the deposition surfaceon structural, optical and morphology properties of copper oxide thinfilms was studied. The film was prepared by homemade fullycomputerized CNC spray pyrolysis deposition technique atpreparations speed (3, 4, 5, and 6 mm/sec). The repeated line modewas used at deposition temperature equal 450 °C whereas thespraying time was in the range of (15-30 min) according to thedeposition speed. The film exhibit polycrystalline structure withpreferred orientation along (-111), (022) and (011), (002) at a 2θvalue of (35.63o) and (38.8o) respectively. Optical band gaps wererecorded at these speed shows variance in value from (1.53-2.08 eV).Films thickness were found to be in the range (128-412 nm) whichdepends on preparation speed.

Influence of annealing temperature on tuning the band gap of Mn-doped ZnS thin films deposited by spray pyrolysis technique

Transition metal (Mn)-doped II–VI binary (ZnS) semiconductor (Zn1−xMnxS, where, x = 0.1, 0.3, 0.5 and 0.7 M) thin films were deposited onto glass substrates using a spray pyrolysis deposition technique at 350 °C. The as-deposited film was found to be homogeneous and smooth for x = 0.3 M. Annealing temperature greatly affects the film morphology. So the effect of annealing temperature on the structural, optical and electrical properties of the Zn0.70Mn0.30S thin films was studied to explore the suitable application of these films in optoelectronics devices. The lattice defects and the internal dislocation density are found to decrease with the annealing temperature, causing improved crystallinity of the film. The decrease in dislocation density suggests an increase in the crystallinity of the film. The optical transmittance of the thin films increases with increasing annealing temperature, and the optical band gap is found to be red-shifted from 3.45 to 3.05 eV. The redshift in the band gap is due to the decrease in the amorphous phase in the thin film owning to annealing. The electrical conductivity of the films was also found to be improved by thermal treatment which may be attributed to the increased crystallinity.

Plasmonic Ag@Nb2O5 surface passivation layer on quantum confined SnO2 films for high current dye-sensitized solar cell applications

Quantum-confined SnO2 nanoparticles of size <6 nm are synthesized by a hydrothermal process and these nanoparticles are dispersed in a colloidal solution to deposit onto transparent conductive glasses (FTO) via spray-pyrolysis deposition (SPD) technique. The spray-pyrolysis deposited SnO2 films are used as photoanode in dye-sensitized solar cells (DSSCs). Very high current and improved conversion efficiencies are the characteristic of these SnO2 solar cells compared to those from literature. Applying an Nb2O5 energy layer on top of SnO2 films via RF sputtering resulted in an improvement in performance of these solar cells. Ag nanoparticle/Nb2O5 composite is applied as plasmonic surface passivation layer on SnO2 photoanodes which improved the absorption spectra of the dye-sensitized photoanodes and the current density (17.44–23.12 mA/cm2) and power conversion efficiencies (4.36%–6.47%) of the DSSCs. This article thus focuses on synthesis and quantum confinement properties of SnO2 nanoparticles, the effect of Nb2O5 and Ag nanoparticles on the optical and electronic properties of the SnO2 photoanodes and finally the photovoltaic properties of the SnO2 photoanodes with Nb2O5/Ag-Nb2O5 surface passivation layers.

Compact TiO2/Anatase TiO2 Single-Crystalline Nanoparticle Electron-Transport Bilayer for Efficient Planar Perovskite Solar Cells

Electron-transport layer (ETL)/perovskite interface modification plays a key task for producing efficient planar perovskite solar cells (PSCs). In this study, interfacial modification of compact TiO2 using novel, one-step hydrothermally synthesized single-crystalline anatase (AT) titania nanoparticles (TiO2 NPs) (average diameter = 6–10 nm) was applied as an ETL bilayer to enhance the efficient charge generation and extraction and eliminate the electron–hole recombination ratio. We report here an easy approach for enhancing the performance of planar PSCs by introducing a compact TiO2/AT TiO2 NPs bilayer through spray pyrolysis (SP) deposition and spin-coating (SC) techniques, respectively. The enhanced performance of the devices with an SP-TiO2/SC-AT TiO2 NPs bilayer facilitated more efficient electron transport, charge extraction, and low interfacial recombination. Ultimately, the best device had a 17.05% power conversion efficiency resulting from the significant decrease in J–V hysteresis, presenting al...

Synthesis, structural, optical and magnetic properties in the sprayed ZnO: Fe3+: explanations of the origin of the tuned ferromagnetism and optical parameters by first principle

Fe3+ doped ZnO was elaborated using spray pyrolysis deposition technique with different concentrations of the doping element then characterized by the x-ray diffraction for the structural characterizations of our samples. We investigated optical properties using Uv-Vis spectrophotometer in the wavelength range of 200–880 nm and also magnetic properties by first principal density functional theory electronic structure calculations to estimate the sample magnetic properties and the Curie temperature. The change in the physical parameters and its relation with the measured optical band gap were investigated in detail to understand the cause and to improve the optical and magnetic properties. The measured optical absorption spectra and band gap values are in agreement with the Ferromagnetic stability of the magnetic dopants charge states. The magnetic interaction was explained by the Zener p-d double exchange. The optimized structure was confirmed using the first-principle stability calculations.

Comparative Study on Graded-Barrier AlxGa1−xN/AlN/GaN/Si Metal-Oxide-Semiconductor Heterostructure Field-Effect Transistor by Using Ultrasonic Spray Pyrolysis Deposition Technique

Comparative study on a novel Al2O3-dielectric graded-barrier (GB) AlxGa1−xN/AlN/GaN/Si (x = 0.22 ∼ 0.3) metal-oxide-semiconductor heterostructure field-effect transistor (MOS-HFET) formed by using the ultrasonic spray pyrolysis deposition (USPD) technique has been made with respect to a conventional-barrier (CB) Al0.26Ga0.74N/AlN/GaN/Si MOS-HFET and the reference Schottky-gate HFET devices. The GB AlxGa1−xN was devised to improve the interfacial quality and enhance the Schottky barrier height at the same time. A cost-effective ultrasonic spray pyrolysis deposition (USPD) method was used to form the high-k Al2O3 gate dielectric and surface passivation on the AlGaN barrier of the present MOS-HFETs. Comprehensive device performances, including maximum extrinsic transconductance (gm,max), maximum drain-source current density (IDS,max), gate-voltage swing (GVS) linearity, breakdown voltages, subthreshold swing (SS), on/off current ratio (Ion/Ioff), high frequencies, and power performance are investigated.

Physical, optical and sensing properties of sprayed zinc doped tin oxide films

Zn doped SnO2 films have been prepared on Si (100) and glass substrates by ultrasonic spray pyrolysis deposition technique from tin chloride dehydrate doped with different Zn acetate concentration. EDX techniques employed to investigate the elements contents. Zn element in the prepared films increased from 0 to about ∼5 at.% as the Zn acetate solution concentration increased from 0 to 20%. XRD pattern showed four orientations (110), (101), (200) and (211). Average grain size decreased with Zn concentration, and texture factor (TC) evaluated from intensity of the diffraction peaks. Raman spectrua correlate with XRD results. Thickness and morphology of the films explored from cross section and surface SEM images, respectively. 2D AFM images clarify the modifications of the morphology with adding Zn acetate. The values of roughness (Ra and RMS) are decreased with Zn concentrations. The band gap (Eg) and transparency of the films have been deduced from UV spectra, where Eg declined with Zn concentration. Acetone, ethanol, methanol, humidity (H2O) and NH3 vapor gases confirmed the sensing properties at room temperature of the deposited films. SnO2 films doped with Zn are exhibited enhanced response in humidity and ethanol vapors at room temperature.

Al2O3-Dielectric In0.18Al0.82N/AlN/GaN/Si Metal-Oxide-Semiconductor Heterostructure Field-Effect Transistors With Backside Substrate Metal-Trench Structure

This paper investigates novel Al2O3-dielectric In0.18Al0.82N/AlN/GaN metal-oxide-semiconductor heterostructure field-effect transistors (MOS-HFETs) with backside metal-trench structure grown by using a non-vacuum ultrasonic spray pyrolysis deposition technique. 3- $\mu \text{m}$ deep metal trenches coated with 150-nm thick Ni were formed on the backside of the Si substrate to improve the heat dissipation efficiency. The present In0.18Al0.82N/AlN/GaN MOS-HFET (Schottky-gate HFET) has demonstrated improved maximum drain–source current density ( $I_{\mathrm{ DS, \max }}$ ) of 1.08 (0.86) A/mm at $\textit{V}_{\mathrm{ DS}}=$ 8 V, gate-voltage swing of 4 (2) V, on/off-current ratio ( $I_{\mathrm{ on}} /I_{\mathrm{ off}} $ ) of $8.9\times 10^{8}$ ( $7.4 \times 10^{4} $ ), subthreshold swing of 140 (244) mV/dec, two-terminal off-state gate-drain breakdown voltage (BVGD) of −191.1 (−173.8) V, turn-on voltage ( $V_{\mathrm{ on}} $ ) of 4.2 (1.2) V, and three-terminal on-state drain-source breakdown voltage (BV $_{DS}$ ) of 155.9 (98.5) V. Enhanced power performances, including saturated output power ( $\textit{P}_{out}$ ) of 27.9 (21.5) dBm, power gain ( $\textit{G}_{a}$ ) of 20.3 (15.5) dB, and power-added efficiency (PAE) of 44.3% (34.8%), are achieved.

Influence of spray-pyrolysis deposition parameters on the electrical properties of aluminium zinc oxides thin films

In the current work, we evaluate the influence of the processing parameters on the electrical properties of aluminium zinc oxide (AZO) thin films produced by airbrush spray-pyrolysis deposition technique. Spray-deposited AZO thin-films were produced with Al:Zn molar ratios varying from 0 % (pure ZnO) up to 30 %, using aluminium acetate and zinc acetate as organic precursors and water as solvent. Thermogravimetric analysis (TGA) and infrared spectroscopy (FTIR-ATR) were used to monitor the metal-oxide formation from the organic precursors as a function of the temperature. The results show that a temperature of 400 °C is necessary to completely degrade the organic phase and to obtain the desired inorganic metal-oxides films. The electrical properties of the TMOs were evaluated by d.c. current-voltage (I-V) analysis using planar thermally evaporated Al electrodes on top of the TMO layer, with different aspect ratios (1/18, 2/9, 5/13, 5/9 and 8/9). The lowest sheet resistance was obtained for AZO films at a molar Al concentration of 5 %. We also observed that, after carrying out a post-annealing treatment (30 mbar, 150 °C) the samples presented a decrease on the sheet resistance superior to 60 %, in comparison to the samples before the treatment.