Optical and electrical properties of ZnO:Al thin films synthesized by low cost spray pyrolysis (original) (raw)
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INFLUENCE OF ALUMINUM CONCENTRATION ON THE ELECTRICAL AND OPTICAL PROPERTIES OF ZnO THIN FILMS
Journal of the Turkish Chemical Society, Section A: Chemistry, 2016
Al:ZnO (AZO) thin films having with different Al concentrations were deposited on glass substrates by a sol-gel technique. The effects of Al doping on the structural, optical, and electrical properties of Al:ZnO were investigated using with XRD, optical transmittance, and sheet resistance measurements. The concentration of zinc acetate was 0.1 M. Al content in the starting solution was varied from 0 to 20% as the molarity range. Optical transmittance spectra of the films in the form of Film/Glass were used to determine the film thickness and optical band gaps. The optical transmissions of Al:ZnO thin films were higher than 80% in the visible and near infrared region. The optical band gaps of Al:ZnO films decrease with increase of Al content. In order to obtain the average sheet resistance of the films the current and voltage through the probes have been measured for five different position by four-point probe method. The results showed that the sheet resistances of Al:ZnO thin films increased with the Al concentration. Considering the film thickness and geometric factor, the electrical resistivity values were computed. It was observed that the sheet resistance of AZO films up to 10% molarity of Al in the starting solution increased.
EPJ Web of Conferences, 2012
Transparent conducting thin films of aluminum-doped zinc oxide (ZnO:Al) have been deposited on SnO 2 :F/glass by the chemical spray technique, starting from zinc acetate (CH 3 CO 2) 2 Zn.2H 2 O and aluminum chloride AlCl 3. The effect of changing the aluminum-to-zinc ratio y from 0 to 3 at.%, has been thoroughly investigated. It was found that the optical and electrical properties of Al doped ZnO films improved with the addition of aluminum in the spray solution until y=2%. At this Al doping percentage, the thin layers have a resistivity equal to 4.1 x 10-4 Ω.cm and a transmittance of about 90 % in the region [600-1000] nm. XRD patterns confirm that the films have polycristalline nature and a wurtzite (hexagonal) structure which characterized with (100), (002) and (101) principal orientations. The undoped films have (002) as the preferred orientation but Al doped ones have (101) as the preferred orientation. Beyond y= 1%, peak intensities decrease considerably.
Electrical and optical properties of ultrasonically sprayed Al-doped zinc oxide thin films
Materials Science and Engineering: B, 2010
Aluminium-doped ZnO (AZO) films were deposited by ultrasonic spray pyrolysis (USP) technique to investigate its potential application as antireflection coating and top contact layer for copper indium gallium diselenide (CIGS) based photovoltaic cells. The solution used to prepare AZO thin films contained 0.2 M of zinc acetate and 0.2 M of aluminium pentanedionate solutions in the order of 2, 3 and 4 at.% of Al/Zn. AZO films were deposited onto glass substrates at different substrate temperatures starting from 450 • C to 500 • C. XRD and FESEM analysis revealed the structural properties of the films and almost all the films possessed crystalline structure with a preferred (0 0 2) orientation except for the 4 at.% of Al. Grain size of AZO films varied from 29.7 to 37 nm for different substrate temperatures and atomic percentage of aluminium. The average optical transmittance of all films with the variation of doping concentration and substrate temperature was 75-90% in the visible range of wavelength 600-700 nm. Optical direct band gap value of 2, 3 and 4 at.% Al-doped films sprayed at different temperatures varied from 3.32 to 3.46 eV. Hall studies were carried out to analyze resistivity, mobility and carrier concentration of the films. AZO films deposited at different substrate temperatures and at various Al/Zn ratios showed resistivity ranging from 0.12 to 1.0 × 10 −2 cm. Mobility value was ∼5 cm 2 /V s and carrier concentration value was ∼7.7 × 10 19 cm −3 . Minimum electrical resistivity was obtained for the 3 at.% Al-doped film sprayed at 475 • C and its value was 1.0 × 10 −2 cm with film thickness of 602 nm. The electrical conductivity of ZnO films was improved by aluminium doping.
Preparation and characteristics study of ZnO: (Al, Cu, I) thin films by chemical spray pyrolysis
e-Journal of Surface Science and Nanotechnology, 2006
Spray pyrolysis deposition technique has been used to grow ZnO thin films doped with different dopant species (Al, Cu, I). The optical and electrical properties of films were investigated as function of dopant type and concentration. The structural characteristics of undoped and doped ZnO films were studied using X-ray diffraction (XRD). The electrical resistivity as low as 4 × 10 −2 Ωcm was obtained for ZnO:Al with 5 at.% dopant concentration. ZnO:Cu films prepared at specific conditions exhibited p-type conductivity. The optical band gap of doped ZnO films varied from 3.09 eV to 3.2 eV. XRD investigation confirmed that the doped ZnO films had preferred orientation in the direction of (101) plane.
Applied Sciences, 2021
ZnO thin films with oxygen vacancies and doped with Al, Ga, and In (Zn1-xMxO1−y (x = 0.03)) have been successfully deposited on soda-lime glass substrates using a simple soft chemical method. The crystalline structure shows a single hexagonal phase of wurtzite with preferred crystal growth along the 002 plane. The surface morphology, characterized by SEM, revealed that the grain shape varies depending on the dopant agent used. Optical measurements displayed an increase in the bandgap values for doped films from 3.29 for ZnO to 3.35, 3.32, and 3.36 for Al, Ga, and In doped films, respectively, and an average transmittance superior to 90% in some cases (in the range between 400 and 800 nm). The electrical response of the films was evaluated with a four-point probe being 229.69, 385.71, and 146.94 Ω/sq for aluminium, gallium, and indium doped films, respectively.
Al Doped ZnO Thin Films; Preparation and Characterization
2018
ZnO is a promising material suitable for variety of novel electronic applications including sensors, transistors, and solar cells. Intrinsic ZnO film has inferiority in terms of electronic properties, which has prompted researches and investigations on doped ZnO films in order to improve its electronic properties. In this work, aluminum (Al) doped ZnO (AZO) with various concentrations and undoped ZnO films were coated on glass substrates by a sol–gel spin coating technique. The samples were analyzed by X-ray diffraction (XRD), scanning electron microscopy (SEM), Uv-Vis spectrometer and four point probe technique to investigate the structural, surface morphology, optical transmittance, and electronic properties of the thin films. The optical transmittances of these samples in the visible region are in the range of 85-95% and the SEM images showed the size of nanoparticles were decrease with doping. Also 2% Al doped ZnO thin films had a lowest resistivity of all the samples that prepa...
Impact of Aluminum Oxide Content on the Structural and Optical Properties of ZnO: AlO Thin Films
Iraqi Journal of Physics, 2021
Article info. AlO-doped ZnO nanocrystalline thin films from with nano crystallite size in the range (19-15 nm) were fabricated by pulsed laser deposition technique. The reduction of crystallite size by increasing of doping ratio shift the bandgap to IR region the optical band gap decreases in a consistent manner, from 3.21to 2.1 eV by increasing AlO doping ratio from 0 to 7wt% but then returns to grow up to 3.21 eV by a further increase the doping ratio. The bandgap increment obtained for 9% AlO dopant concentration can.be clarified in terms of the Burstein-Moss effect whereas the aluminum donor atom increased the carrier's concentration which in turn shifts the Fermi level and widened the bandgap (blue-shift). The engineering of the bandgap by low concentration of AlO dopant makes ZnO: AlO thin films favorable for the fabrication of optoelectronic devices. The optical constants were calculated and was found to be greatly affected by the increasing the doping ratio.
Growth and Characterization of ZnO and Al-Doped ZnO Thin Films by a Homemade Spray Pyrolysis
Semiconductors, 2020
In this work, we have prepared the undoped and Al-doped ZnO thin films by a homemade spray pyrolysis method at 450°C onto glass substrates. The X-ray diffraction patterns of undoped ZnO and aluminized zinc-oxide (AZO) thin films exhibit hexagonal wurtzite crystal structure with high crystalline quality, the crystallite size is nanometric. The morphology of the undoped and Al-doped ZnO thin films also indicate that all samples have a nanoscale grain size around 50 nm, and the microstructure of ZnO films is highly influenced by the aluminum doping. The two films are characterized by UV-visible spectrophotometry showing that the films have a whole optical transmission above 85% in the visible range. The composition of our films is obtained by energy dispersive spectrum, confirmed by Auger electron spectroscopy (AES) and by Rutherford back-scattering spectrometry (RBS) techniques.
Journal of Materials Science: Materials in Electronics, 2014
Al-doped zinc oxide (AZO) thin films are prepared on polycrystalline fluorine-doped tin oxide-coated conducting glass substrates from nitrates baths by the electrodeposition process at 70°C. The electrochemical, morphological, structural and optical properties of the AZO thin films were investigated in terms of different Al concentration in the starting solution. It was found that the carrier density of AZO thin films varied between -3.11 and -5.56 9 10 20 cm -3 when the Al concentration was between 0 and 5 at.%. Atomic force microscopy images reveal that the concentration of Al has a very significant influence on the surface morphology and roughness of thin AZO. X-ray diffraction spectra demonstrate preferential (002) crystallographic orientation having c-axis perpendicular to the surface of the substrate and average crystallites size of the films was about 33-54 nm. With increasing Al doping, AZO films have a strong improved crystalline quality. As compared to pure ZnO, Al-doped ZnO exhibited lower crystallinity and there is a shift in the (002) diffraction peak to higher angles. Due to the doping of Al of any concentration, the films were found to be showing [80 % transparency. As Al concentration increased the optical band gap was also found to be increase from 3.22 to 3.47 eV. The room-temperature photoluminescence spectra indicated that the introduction of Al can improve the intensity of ultraviolet (UV) emission, thus suggesting its greater prospects in UV optoelectronic devices. A detailed comparison and apprehension of electrochemical, optical and structural properties of ZnO and ZnO:Al thin films is done for the determination of optimum concentration of Al doping.
Plasma Processes and Polymers, 2007
The effect of annealing temperature ranged from 200 to 600 °C on the structural, optical and electrical properties of aluminum doped zinc oxide (ZnO:Al) films was reported. The thin films were deposited on glass and silicon substrates by rf magnetron sputtering method using ZnO target (diameter 7,5 cm) mixed with 2 wt.% Al2O3. It has been found that the crystal structure of ZnO:Al films is hexagonal with c-axis preferential orientation. With an increase in the annealing temperature the intrinsic compressive stress was found to decrease, and near stress-free film was obtained after annealing at 600 °C. A resistivity of 1.25x10 -3 cm and an average transmittance above 90 % in visible range were obtained for films prepared at room temperature.