Abstract:Zinc oxide (ZnO) was synthesized by chemical bath deposition (CBD) technique at two temperatures (70°C and 90°C). Chemical analysis was carried out on the Zn-NH3-OH zone growth using the species distribution diagrams and the solubility curves in order to determine the parameters to obtain good quality ZnO films. Results show that ZnO films can be obtained when the pH solution is up than 7. Three different pH zones between 7 and 12 were selected for deposition. ZnCl2, NH4NO3, and KOH were the chemical reagents … Show more
“…Zinc oxide is an n-type conductivity semiconductor with a wide band gap of 3.37 eV, strong luminescence at room temperature, high conductivity and optical transparency [1,2]. Due to its unique electrical, optical, luminescent and catalytic properties, ZnO is a promising material for various applications [3], including chemical sensors [4,5], transparent field effect transistors [6], transparent conducting oxide [7], atomic force microscopy cantilever [8], nanopiezoelectric devices [9], UV detectors [10], etc. [11,12].…”
Zinc oxide is a promising multifunctional material. The practical use of nano- and polycrystalline ZnO devices faces a serious problem of instability of electrical and luminescent characteristics, due to the adsorption of oxygen by the surface during aging. In this paper, the aging effect in ZnO films and nanorod arrays was studied. It was found that ZnO samples demonstrate different behavior of the degradation process, which corresponds to at least two different types of adsorbing surface sites for O2, where O2 adsorption is of a different nature. The first type of surface sites is rapidly depassivated after hydrogen passivation and the aging effect takes place due to these centers. The second type of surface sites has a stable structure after hydrogen passivation and corresponds to HO–ZnO sites. The XPS components of these sites include the Zn2p3/2 peak at 1022.2 ± 0.2 eV and Zn2p1/2 peak at 1045.2 ± 0.2 eV, with a part of the XPS O1s peak at 531.5 ± 0.3 eV. The annealing transforms the first type of site into the second one, and the subsequent short-term plasma treatment in hydrogen results in steady passivation, where the degradation of characteristics is practically reduced to zero.
“…Zinc oxide is an n-type conductivity semiconductor with a wide band gap of 3.37 eV, strong luminescence at room temperature, high conductivity and optical transparency [1,2]. Due to its unique electrical, optical, luminescent and catalytic properties, ZnO is a promising material for various applications [3], including chemical sensors [4,5], transparent field effect transistors [6], transparent conducting oxide [7], atomic force microscopy cantilever [8], nanopiezoelectric devices [9], UV detectors [10], etc. [11,12].…”
Zinc oxide is a promising multifunctional material. The practical use of nano- and polycrystalline ZnO devices faces a serious problem of instability of electrical and luminescent characteristics, due to the adsorption of oxygen by the surface during aging. In this paper, the aging effect in ZnO films and nanorod arrays was studied. It was found that ZnO samples demonstrate different behavior of the degradation process, which corresponds to at least two different types of adsorbing surface sites for O2, where O2 adsorption is of a different nature. The first type of surface sites is rapidly depassivated after hydrogen passivation and the aging effect takes place due to these centers. The second type of surface sites has a stable structure after hydrogen passivation and corresponds to HO–ZnO sites. The XPS components of these sites include the Zn2p3/2 peak at 1022.2 ± 0.2 eV and Zn2p1/2 peak at 1045.2 ± 0.2 eV, with a part of the XPS O1s peak at 531.5 ± 0.3 eV. The annealing transforms the first type of site into the second one, and the subsequent short-term plasma treatment in hydrogen results in steady passivation, where the degradation of characteristics is practically reduced to zero.
“…Readers are referred to section F of the Supplementary Information for the specific details of each step presented in Figure 7. Also, a detailed discussion of the use of SDDs and SCs for the study of ZnS, ZnO and Zn(OH) 2 [156-181] are also presented at such section in the Supplementary Information. Figure 7 Generalized algorithm for obtaining the SDDs and SCs for depositing M 2+ (M = Zn, Cd) for CBD technique.…”
Section: The Algorithm For Calculating the Optimized Chemical Conditi...mentioning
The material deposition in aqueous solution, also known as chemical bath deposition (CBD), is a well-established technique for the fabrication of semiconducting thin films. The success of the CBD technique is mainly based on the relatively easy implementation and operation requirements. The CBD has importantly contributed to the development of sensors, optical devices and solar cells applications. In this review, the origins and current state of the art of the CBD technique, the involved physicochemical processes, the growing mechanisms, and the analytical techniques for the estimation of optimal physicochemical conditions for the film deposition are discussed. Emphasis on authors' experience on CBD of CdS, ZnS, Zn (OH) 2 , and ZnO films are here highlighted, following methodologies for a high control of the deposited materials, such as the species distribution diagrams and the solubility curves.
“…The canonical method for the estimation of film synthesis parameters from an initially homogeneous solution at elevated temperatures is the thermodynamic analysis of the considered chemical system [4,5]. The distribution diagrams of complex ions and calculation of solubility curves at different temperatures for predicting the region of ZnO film production in the system "ZnCl 2 -NH 3 -OH-H 2 O -temperature" showed [19] that ZnO films can be obtained at solution pH above 7. The morphology of such films depends on the pH of the solution, the polycrystals of nanoparticles in the form of flowers or columnar structures growing in the area where Zn(NH 3 ) 2+ 4 complexes predominate.…”
Section: Introductionmentioning
confidence: 99%
“…ZnO films deposited at high temperature (90 • C) have an oriented hexagonal structure (zincite) and [Zn]/[O] ≈ 1 stoichiometry, while at lower temperatures (70 • C) flaky amorphous films are formed. The main reaction that accompanies film growth is heterogeneous decomposition of ammonia or zinc hydroxo-complex in alkaline medium [19][20][21]. The cited papers note the thermodynamic probability of formation of ammonia molecules during decomposition of ammonia zinc complexes in an initially homogeneous solution, but the role of the gas phase in the growth mechanism of colloidal particles in solution and in the film is not considered.…”
Thermodynamic and experimental studies of Zn(OH) 2 /ZnO particle formation conditions in the model of closed system Zn 2+ -NH 3,aq -NH 3,gas -H + -OH − -H 2 O-N 2,gas (1), which often occurs in the process of synthesis of zinc oxide nanoparticles and films by chemical bath deposition (CBD) methods, were carried out. It was shown that the driving force for the formation and growth of Zn(OH) 2 /ZnO particles in the initially homogeneous system (1) at 25 • C is the difference in the chemical potential of particles at the initial temperature (unsaturated system) and the synthesis temperature (supersaturated system). Using vibrational spectroscopy, X-ray phase and chemical analysis, diffuse light scattering and electrophoresis methods, it was found that the phase transformation of Zn(OH) 2 into ZnO takes place in the region of 85 -90 • C. The colloid-chemical transformation of Zn(NH 3 ) 2+ 4 ionic particles into colloidal polycrystals of Zn(OH) 2 /ZnO composition was established for the first time to be a staged process. The first stage of the process in the solution volume is localized at the gas nanobubble-solution interface as a result of rapid formation, growth and removal of gas nanobubbles from the solution. The interaction of positively charged Zn(OH) 2 nanoparticles with the surface of larger negatively charged gas nanobubbles creates colloidal aggregates "bubble||surface film of hydroxide nanoparticles". Their adhesion forms an openwork foam-like structure of the colloid in the solution and in the film on the interfaces at the first stage of synthesis. After degassing of the electrolyte solution, the second stage develops, consisting of the nucleation and ionic-molecular growth of Zn(OH) 2 /ZnO particles from the supersaturated solution, their distribution between the solution and the electrolyte -reactor wall -air interfaces. The film growth at this stage is regulated by the difference in surface charges of the double electric layer of the interface and polycrystalline colloidal particles. In the solution and on the interface, columnar Zn(OH) 2 /ZnO structures grow as volumetric stars with conical hexagonal spikes. KEYWORDS Zn(OH) 2 , ZnO, layer, formation, glass, interface, mechanism, colloidal-chemical, NH 3 solution ACKNOWLEDGEMENTS This study was performed in the framework of the state-financed topic AAAA-A19-119031890028-0 at ISSC UB RAS.
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