Thin film growth quartz crystal microbalance

Phosphonate salte of tetravalent, trivalent, and divalent metal ions contain strong ionic-covalent bonds within the metal-oxygen sheets that determine the details of their lamellar structures. Tbe divalent metal (Zn2+ and Cu2+) compounds can be made nanoporous by various techniques, and subsequent intercalation by small molecules such as ammonia, amines, and other small molecules forms the basis for size- and shiqw-selective piezoelectric sensors. Several techniques have been developed for depositing these materials as thin Hlms on quartz crystal microbalance (QCM) devices. The most successful of these, in terms of eliminating interferences and speed of device response, involves layer-by-layer growth of films through adsorption of their components from non-aqueous solutions. 

Lincot D, Ortega-Borges R (1992) Chemical bath deposition of cadmium sulfide thin films. In situ growth and structural studies by Combined Quartz Crystal Microbalance and Electrochemical Impedance techniques. J Electrochem Soc 139 1880-1889... 

It has been shown that the TEA process leads to high-quality films [43—45]. The mechanism involving the CBD of CdS thin films from the ammonia-thiourea system have been studied in situ by means of the quartz crystal microbalance technique (QCM) [25]. The formation of CdS was assumed to result from the decomposition of adsorbed thiourea molecules via the formation of an intermediate surface complex with cadmium hydroxide. This mechanism is different from the dissociation mechanism involving the formation of free sulfide ions in solution, and which had previously been reported [46-49]. Thus, the influence of growth parameters such as bath temperature, deposition rate, bath composition, etc., on various film properties has been studied [37, 39, 41, 50, 51], and the main parameters which determine the quality of the films were deduced. The chemical deposition of CdS thin films generally consisted of the decomposition of thiourea in an alkaline solution containing a cadmium salt The deposition process was based on the slow release of Cd and S ions in solution which then condensed on an ion-by-ion basis on the substrate. The reaction process for the formation of CdS may be described by the following steps [25, 35, 36, 43, 52-54]. 

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