Wet Chemical Deposition Method Research Articles

Surface photovoltage analysis of ZnO nanorods/p-Si heterostructure

In this work, n-type ZnO nanorods (NRs) were fabricated on a p-type Si substrate to form a ZnO NRs/Si structure using a low-temperature wet chemical bath deposition method. Kelvin-probe-based surface photovoltage (KP-based SPV) technology was used to study the behavior of surface photogenerated charges for the as-grown heterostructure. In general, the KP-based SPV response range of the ZnO NRs/Si structure was significantly expanded compared with the bare Si substrate, due to the incorporation of ZnO NRs. Moreover, the SPV response amplitude for ZnO NRs/Si structure also depended on the length and diameter of the NRs, and the corresponding mechanism was elucidated in terms of O2 adsorption. The photovoltaic application of the ZnO NRs/Si based structure would benefit significantly from these achievements.

Synthesis of Nest-Like NiO and its Application on P-Type Dye-Sensitized Solar Cell

The nest-like NiO was successfully prepared by calcining the Ni(OH)2 precursor synthesized using wet chemical deposition method. A NiO-based p-type dye-sensitized solar cell was fabricated. The photocathode films were coated by doctor-blading NiO paste onto the FTO substrates. The thickness of NiO film was controlled by repeatedly blade coating using one layer of tape. The results manifested that the thickness of the NiO film significantly influenced the photoconversion efficiency. The solar cell based on the NiO film with 13 μm thickness showed the highest photoconversion efficiency. In addition, the influence of the dye is also investigated. The NiO films were sensitized with C343, N3, and Z907, respectively. The measurement of photocurrent density-voltage characteristics indicated that the highest photoconversion efficiency is about 0.027% using C343 sensitized.

A wet chemical preparation of transparent conducting thin films of Al-doped ZnO nanoparticles

A wet chemical deposition method for preparing transparent conductive thin films on the base of Al-doped ZnO (AZO) nanoparticles has been demonstrated. AZO nanoparticles with a size of 7 nm have been synthesised by a simple precipitation method in refluxed conditions in ethanol using zinc acetate and Al-isopropylate. The presence of Al in ZnO was revealed by the EDX elemental analysis (1.8 at.%) and UV–Vis spectroscopy (a blue shift due to Burstein–Moss effect). The obtained colloid solution with the AZO nanoparticles was used for preparing by spin-coating thin films on glass substrates. The film demonstrated excellent homogeneity and transparency (T > 90%) in the visible spectrum after heating at 400 °C. Its resistivity turned to be excessively high (ρ = 2.6 Ω cm) that we ascribe to a poor charge percolation due to a high film porosity revealed by SEM observations. To improve the percolation via reducing the porosity, a sol–gel solution was deposited “layer-by-layer” in alternation with layers derived from the AZO colloid followed by heating. As it was shown by optical spectroscopy measurements, the density of thus prepared film was increased more than twice leading to a significant decrease in resistivity to 1.3 × 10−2 Ω cm.

Concepts of inorganic solid-state nanostructured solar cells

The development of inorganic solid-state nanostructured solar cells over the last years has been reviewed with respect to concepts and materials. Major attention has been paid to solar cells with extremely thin absorber, solar cells with ultra-thin nano-composite absorber and solar cells with quantum dot absorber layers. The focus has been set to structured transparent electron conductors and absorber materials prepared by mainly low-temperature and wet chemical deposition methods. The great potential of inorganic solid-state nanostructured solar cells is discussed.

Photovoltaic properties of the copper-phthalocyanine and ZnO nanorod array system affected by ethanol

Well-aligned ZnO nanorod array, fabricated on conductive indium-tin-oxide (ITO) substrate by wet chemical bath deposition (CBD) method, was characterized by scanning electron microscopy (SEM) and X-ray diffraction (XRD). Surface photovoltage (SPV) technique was employed to study the photovoltaic properties of the copper-phthalocyanine (CuPc) and ZnO nanorod array system affected by ethanol. Prior to ethanol adsorption, two pronounced SPV response bands were exhibited for this system in the range 300–410 and 540–760 nm, respectively. Post-adsorption measurements reveal that the SPV intensity of the former band is enhanced, while that of the latter band is suppressed if ethanol was used to modify CuPc surface. Moreover, both of the SPV intensity of two response bands is enhanced if ethanol was used to modify ZnO and CuPc interface. Mechanisms of these phenomena were suggested.

Characterization of optoelectronic properties of the ZnO nanorod array using surface photovoltage technique

Well-aligned ZnO nanorod array, synthesized by wet chemical bath deposition (CBD) method on conductive indium–in-oxide (ITO) substrate, was characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD) and photoluminescence (PL) spectroscopy. Surface photovoltage (SPV) technique based on a scanning Kelvin Probe system was employed to investigate the optoelectronic behavior of ZnO nanorod array. The surface photovoltage and its time-resolved evolution process are used to determine the energy level structure of the ZnO nanorod array.

Controllable growth of well-aligned ZnO nanorod arrays by low-temperature wet chemical bath deposition method

Well-aligned ZnO nanorod arrays were synthesized by low-temperature wet chemical bath deposition (CBD) method on Si substrate under different conditions. Results illustrated that dense ZnO nanorods with hexagonal wurtzite structure were vertically well-aligned and uniformly distributed on the substrate. The effects of precursor concentration, growth temperature and time on nanorods morphology were investigated systematically. The mechanism for the effect of preparation parameters was elucidated based on the chemical process of CBD and basic nucleation theory. It is demonstrated that the controllable growth of well-aligned ZnO nanorods can be realized by readily adjusting the preparation parameters. Strong near-band edge ultraviolet (UV) emission were observed in room temperature photoluminescence (PL) spectra for the samples prepared under optimized parameters, yet the usually observed defect related deep level emissions were nearly undetectable, indicating high optical quality ZnO nanorod arrays could be achieved via this easy process chemical approach at low temperature.

Cracking of n-heptane over Brønsted acid sites and Lewis acid Ga sites in ZSM-5 zeolite

A series of gallium-containing ZSM-5 zeolites prepared by wet impregnation, ion-exchange and chemical vapor deposition (CVD) methods are compared in the cracking of n-heptane. Impregnation results in the dispersion of some of the gallium oxide clusters into the zeolite pore network as charge-compensating Ga species after calcination. Reduction of impregnated Ga/HZSM-5 catalysts leads to complete transformation of the oxidic Ga precursors to charge-compensating Ga + and GaH 2+ species. A small amount of divalent GaH 2+ species can be stabilized; however, with increasing Ga/Al ratio monovalent cations dominate. While a model Ga/HZSM-5 catalyst prepared by CVD of Ga(CH 3) 3 containing mainly charge-compensating Ga cations displays high selectivity to dehydrogenated products (olefins, toluene and coke), catalysts with a lower Ga/Al ratio display improved activity with a product mixture resulting from contributions of Ga sites (dehydrogenation, aromatization, olefin cracking) and of Brønsted acid sites (protolytic cracking, olefin cracking). The synergy between Ga dehydrogenation sites and Brønsted acid sites is proposed to improve the dehydrogenation rate: the high acidity of the zeolitic proton facilitates hydrogen recombination and concomitant removal of product olefin from the Ga active sites. Ion-exchanged Ga/HZSM-5 catalyst which combines a difficult to reduce gallium oxide phase and high Brønsted acidity has the highest activity with relatively weak coke formation.

Anatase TiO2 nanoparticles immobilized on ZnO tetrapods as a highly efficient and easily recyclable photocatalyst

Anatase TiO2 nanoparticles in the size of ca. 6nm were immobilized on the single-crystalline tetrapod-like ZnO (denoted as T-ZnO in the text) with dimensions up to 20–50μm by vapor hydrolysis method (VHM). Compared to the wet chemical deposition method, more uniform TiO2 layers with a tunable thickness were achieved by VHM. T-ZnO showed a relatively low efficiency in the photooxidation reaction of phenol. After coating of anatase nanoparticles, the photocatalytic activity of the nanocomposite (TiO2/T-ZnO) was significantly enhanced in photooxidation of phenol. Moreover, in contrast to the discrete nanoparticles, TiO2/T-ZnO could be very easily recovered from the treated solution by a most common filter paper. The easily recyclable feature and the high efficiency made TiO2/T-ZnO act as low-cost and feasible photocatalysts for the large-scale applications.

Preparation of Yellow Color Pearlescent Pigments of CeO<sub>2</sub>-Mica

A wet-chemical deposition method was developed to synthesize CeO2-mica pearlescent pigment using CeO2 as the coating material and mica as the base material. The main factors affecting the synthesis processes were studied. The optimum conditions were obtained were as: the coating reaction temperature is 70 ~ 80°C, cover ratio is 30 ~ 40%, stirring velocity is about 170 r/min, pH value is 6.50 ~ 7.50, heating rate is 3 ~ 5°C/min and heat treatment temperature is 800°C. The crystal phases and the microstructure of the pearlescent pigment powders were also analyzed by DTA-TG, XRD and SEM.

Preparation of Color Pearlescent Pigment Using Rare-Earth Oxide and Titanium Oxide to Coat Mica

The rare earth of Er2O3, Nd2O3, Pr6O11 as pigmentation-type coating materials was used to coat the surface of mica by wet chemical deposition method. Then the color pearl luster pigment was synthesized by heat treatment. The coating was carried out by multiple-coating technique and the influence of technique parameters on the coating was studied systematically.

Multi-Nucleation-Based Formation of Oriented Zinc Oxide Microcrystals and Films in Aqueous Solutions

A wet-chemical deposition method of synthesizing highly oriented, transparent ZnO films on a crystalline template is described. Multi-nucleation and the subsequent growth of ZnO nanodomains at an early stage of wet-chemical deposition leads to the formation of thin hexagonal platelike ZnO crystals spread over the template film. A subsequent temperature increase allows the growth of oriented rods, whose size depends on that of the platelike crystals. Consequently, oriented ZnO films with various microstructures can be synthesized by controlling the size of the ZnO plates at an early stage of deposition.

Nanoparticle Arrays on Surfaces Fabricated Using Anodic Alumina Films as Templates

AbstractHigh density nanoparticle arrays on surfaces have been created using a template‐assisted approach. Templates were produced by evaporating aluminum onto substrates and subsequently anodizing the aluminum to produce nanoporous alumina films. The resulting templates have a narrow distribution of pore sizes tunable from ∼ 25 to ∼ 70 nm. To demonstrate the flexibility of this approach for producing nanoparticle arrays on various substrates, templates have been fabricated on silicon oxide, silicon, and gold surfaces. In all cases, a final chemical etching step yielded pores that extended completely through the template to the underlying substrate. Because the templates remain in intimate contact with the substrate throughout processing, they may be used with either vacuum‐based or wet chemical deposition methods to direct the deposition of nanoparticles onto the underlying substrates. Here we have produced gold nanodot arrays using evaporation and gold nanorod arrays by electrodeposition. In each case, the diameter and height of the nanoparticles can be controlled using the confining dimensions of the templates, resulting in high density (∼ 1010 cm–2) arrays of nanoparticles over large areas (> 1 cm2).

Use of electroless Pd/Sn/Au films for ohmic contacts on n-GaAs

We describe the technique of obtaining ohmic contacts onto n-GaAs by using a wet chemical deposition method ( = electroless deposition). Electrical and morphological characteristics of electroless Pd/Sn/Au multilayers deposited onto n-GaAs are presented. It is shown that good quality contacts can be obtained by using this simple, fast and low cost method.

Use of electroless Pd/Sn/Au films for ohmic contacts on n-GaAs

We describe the technique of obtaining ohmic contacts onto n-GaAs by using a wet chemical deposition method ( = electroless deposition). Electrical and morphological characteristics of electroless Pd/Sn/Au multilayers deposited onto n-GaAs are presented. It is shown that good quality contacts can be obtained by using this simple, fast and low cost method.