Successive Chemical Solution Deposition Research Articles

Characterization of tin (II) sulphide thin film synthesized by successive chemical solution deposition

In the present work, tin (II) sulphide (SnS) thin films were grown on glass substrate by successive chemical solution deposition method using ammonium sulphide as anionic precursor solutions. Characterization techniques of X-ray diffraction, scanning electron microscopy, field emission scanning electron microscopy and energy-dispersive x-ray were utilized to study the microstructure of the films. Energy-dispersive x-ray confirmed formation of nearly stoichiometric film with slight excess of tin under optimized deposition conditions. Particle size estimated from Rietveld refinement of X-ray diffraction data using MAUD software was ~41 nm which compared well with field emission scanning electron microscopy measurements. The value of the energy gap of ~1.51 eV was found to be near the optimum needs for photovoltaic solar energy conversion (1.5 eV) with high absorption in the visible region. An enhancement in energy gap was observed for tin-enriched films.

ZnO:Al Thin Films by Successive Chemical Solution Deposition for Transistors Applications

ABSTRACTHere, we show results on the deposition of ZnO:Al thin films by the successive ionic layer adsorption and reaction method. The growing of the films was performed by sequentially immersing glass and SiO2/Si substrates in water at temperatures close to the boiling point, a precursor reaction solution, water at room temperature and ultrasonic water bath. The resulting ZnO:Al films were transparent and well adhered to the substrates. From X-ray diffraction analysis was determined that the ZnO:Al films had hexagonal wurtzite structure with preferential orientation along the c-axis. Changes in the morphology of the films were obtained from ellipsoidal-shaped aggregates for the undoped ZnO films to spherical-shaped aggregates for the ZnO:Al films. The optical transparency and bandgap of the ZnO:Al films was about 85% and 3.28 eV, respectively. Thin film transistors were fabricated with ZnO:Al films as active layers. The characterized device had a saturation mobility of 0.048 cm2/V-s, threshold voltage of approximately 16.1 V and a drain current on-to-off ratio (Ion/Ioff) in the order of 103.

Visible light emission and UV light detection properties of solution-grown ZnO/polymer heterojunction diodes on stainless steel foil

Abstract Heterojunction devices were prepared from ZnO films grown by successive chemical solution deposition on flexible stainless steel substrate and from p-type polymer films of PEDOT:PSS. The effect of air annealing and H 2 O 2 treatment of ZnO on the optoelectronic properties of devices were investigated. Various techniques were utilized for the characterization of ZnO films and the evaluation of devices. Devices with diode type current–voltage and capacitance–voltage characteristics can be fabricated if the hydroxyl content of the as-grown ZnO is removed by annealing the film in air (400 °C, 20 min). H 2 O 2 treatment of ZnO for 10 min followed by air annealing yields a high resistivity interfacial layer required for the device to exhibit visible electroluminescence. A typical light emitting diode shows a current rectification factor of ∼100 (±2 V), ideality factor of 3.0, barrier height of 1.1 eV and reverse-bias breakdown voltage of −36 V. Fabricated diodes show self-powered visible-blind UV photodetection characteristics in the wavelength range of 274–375 nm.

Study of ZnO Nanoparticles Growth Through Successive Chemical Solution Deposition onto Solid Substrates Patterned with Metallic Nanoparticles

We investigate the ability of gold nanoparticles of different size, shape, and organization to control the growing process of ZnO semiconductor nanoparticles onto solid substrates through the successive chemical solution deposition (SCSD) method. Flower-like assemblies of ZnO nanostructures were grown successfully on periodic arrays of triangular gold nanoparticles fabricated by nanosphere lithography and randomly deposited colloidal gold nanospheres. Their morphology, crystallinity, phase purity, and vibrational properties were correlated with the metallic features of the substrates.

Synthesis of nanostructured Al-doped zinc oxide films on Si for solar cells applications

Al-doped ZnO thin films have been prepared by a novel successive chemical solution deposition technique. The variation in morphological, structural, electrical, and optical properties of nanostructured films with doping concentration is investigated in details. It was demonstrated that rapid photothermal processing (RPP) improves the quality of nanostructured ZnO films according to the enhancement of resonant Raman scattering efficiency, and the suppression of the visible luminescence with the increase of RPP temperature. It was found from the I– V characteristics of ZnO/Si heterojunction that the average short-circuit current density is about 8 mA/cm 2. For 1%Al-doped ZnO/SiO 2/Si structure, the short-circuit current density is about 28 mA/cm 2. The improvement shown in the characteristics may be assigned partially to the reduction of the defect density in the nanostructured Al-doped ZnO films after RPP. The correlations between the composition, microstructure of the films and the properties of the solar cell structures are discussed. The successive chemically deposited Al-doped ZnO thin film offers wider applications of low-cost solar cells in heterojunction structures.

Characteristics of aligned ZnO nanorods grown on stainless‐steel foil by successive chemical solution deposition

AbstractWell‐aligned ZnO nanorods with a hexagonal cross section of size 200–300 nm and length 1000–1400 nm were grown along their c‐axis normal to the stainless steel substrate. The growth was performed for the first time by successive chemical solution deposition. Their structure, photoluminescence and electrical properties were characterized. Schottky diodes could be fabricated on nanorods which have a high optical transmittance and a band gap energy 3.25–3.28 eV. The Ag Schottky contacts have a large barrier height 0.99 eV and an ideality factor 2.35. The density of uncompensated donors in nanorods is 7 × 1014 cm–3. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Schottky diodes on ZnO rods grown homoepitaxially by successive chemical solution deposition

ZnO-rod samples are grown homoepitaxially by successive chemical solution deposition on a ZnO-coated stainless steel foil substrate. Samples are composed from closely packed ZnO rods aligned along their c-axes perpendicular to the substrate. The structure, morphology, composition and the photoluminescence properties of samples are presented. Gold and silver Schottky diodes are prepared on the untreated and H2O2-treated (0 0 2) facets of the rods, and their parameters are determined from their current–voltage and capacitance–voltage characteristics. Au diodes with a low rectification factor (200 at ±2 V) but a large barrier height (0.78–0.98 eV) and Ag diodes with a high rectification factor (106 at ±2 V) and a large barrier height (0.98–1.10 eV) are achieved. The density of uncompensated donors in ZnO rods is measured to be in the range 1014–1017 cm−3.

Al-doped zinc oxide films grown by successive chemical solution deposition

Films of ZnO were grown and doped by the successive chemical solution deposition technique from a zincate solution containing aluminum (Al/Zn molar ratio in the range 2–10%). To our knowledge, this is the first report of its kind. A post-deposition heat treatment in argon (500 °C, 20 min) was performed for the activation of incorporated Al donors. Films were characterized by using scanning electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy, optical transmittance, photoluminescence and Hall-effect measurement. Films with a resistivity 0.2 Ω cm, carrier concentration 1.2×1018 cm-3 and mobility 26 cm2/V s can be grown from a solution with Al/Zn = 10%. Further reduction in resistivity is plausible by using more heavily doped solutions and by the optimization of annealing parameters. Although the doping process does not change the films’ structure and surface morphology, it slightly lowers the optical transparency in the visible region and blue shifts the room-temperature photoluminescence peak to 378 nm.

Nanostructured zinc oxide films synthesized by successive chemical solution deposition for gas sensor applications

Nanostructured ZnO thin films have been deposited using a successive chemical solution deposition method. The structural, morphological, electrical and sensing properties of the films were studied for different concentrations of Al-dopant and were analyzed as a function of rapid photothermal processing temperatures. The films were investigated by X-ray diffraction, scanning electron microscopy, energy dispersive X-ray spectroscopy, X-ray photoelectron and micro-Raman spectroscopy. Electrical and gas sensitivity measurements were conducted as well. The average grain size is 240 and 224 Å for undoped ZnO and Al-doped ZnO films, respectively. We demonstrate that rapid photothermal processing is an efficient method for improving the quality of nanostructured ZnO films. Nanostructured ZnO films doped with Al showed a higher sensitivity to carbon dioxide than undoped ZnO films. The correlations between material compositions, microstructures of the films and the properties of the gas sensors are discussed.

Boron-doped ZnO films grown by successive chemical solution deposition

ZnO films are deposited on various substrates from zincate solutions (0.1 M) containing boron with a B/Zn atomic ratio of 5%. These films show an optimum n-type resistivity of 40–60 Ω cm. The composition, structure and morphology of the films are studied using x-ray photoelectron spectroscopy, x-ray diffraction (XRD) and scanning electron microscopy. The optical properties of the films are investigated by transmittance and photoluminescence (PL) spectroscopy. The XRD results reveal that the films consist of only hexagonal ZnO with no other crystalline trace compounds. Boron enters the film with almost the same ratio as added into the solution. Other impurities such as Cl and N can also enter the film from the bath solution. Films contain, most likely, zinc hydroxide but in the amorphous phase. The films' hexagonal lattice constants match those for un-doped films. The as-grown films have optical transmittance ≈80% (800 nm) and a direct band gap energy of 3.35 ± 0.05 eV, which reduces to 3.24 ± 0.04 eV upon thermal annealing. The room-temperature PL properties of the films prepared from different bath solutions are presented. The effect of thermal annealing and the bath composition on the UV and visible emissions are discussed.

ZnO films grown by successive chemical solution deposition

ZnO films were grown from 0.1-M zincate solutions on stainless-steel and aluminosilicate glass substrates by the successive chemical solution deposition method. The structure, morphology, composition, and optical emission properties of the films were studied by X-ray diffraction, scanning electron microscopy, X-ray photoelectron spectroscopy, and photoluminescence techniques. Results revealed that the as-grown film contains a substantial amount of amorphous zinc hydroxide (15–25%), at least on its surface. This can be reduced to 7% by annealing the film in argon (350 °C, 1 h). Despite the presence of the hydroxide phase, the films hexagonal lattice constants match the standard values. The films surface texture and the grains shape and preferential orientation depend on the type of the substrate and its surface conditioning. The UV photoluminescence emission from as-grown films at 3.22±0.04 eV (380–390 nm) and its suppression due to the effect of chlorine are addressed.

Successive chemical solution deposition of ZnO films on flexible steel substrate: structure, photoluminescence and optical transitions

Zinc oxide is an attractive optoelectronic material with wide applications. Thin ZnO films were prepared on steel foil by successive chemical solution deposition (SCSD). The film structure, room-temperature photoluminescence (PL) and optical absorption characteristics were investigated. This study revealed that films of high structural and optical quality can be prepared by the SCSD method. PL of as-grown films shows a weak green peak at 560 nm and a strong UV peak at 380 nm. Annealing in either air or argon suppresses the green peak and red shifts the UV emission towards 390 nm. The presence of chlorine in the deposition solution destroys the PL of as-grown films. A strong UV emission, however, develops after annealing the films in air. Several optical transitions measured from the film PL and optical absorption coefficients are shown to be related to transitions through the known defect levels in ZnO, such as E1, L1, E3 and VO2+ levels.