Dynamic Speciation Modeling to Guide Selection of Complexing Agents for Chemical Bath Deposition: Case Study for ZnS Thin Films
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- 作者：Borirak Opasanont ; Jason B. Baxter
- 刊名：Crystal Growth & Design
- 出版年：2015
- 出版时间：October 7, 2015
- 年：2015
- 卷：15
- 期：10
- 页码：4893-4900
- 全文大小：458K
- ISSN：1528-7505
文摘
The dynamic behavior of complexing agents often governs the kinetics of chemical bath deposition (CBD), but dynamics are frequently overlooked in favor of a more simplified description of only initial conditions. Here we demonstrate the importance of complexing agent dynamics using a combination of equilibrium speciation modeling and experiments for the case of ZnS thin films grown with three common complexing agents: ethylenediaminetetraacetate (EDTA), nitrilotriacetate (NTA), and citrate, using a reference recipe that ensured fair comparison. Complexing agents control the deposition rate by limiting the availability of free cations. Speciation modeling was used to simulate the free Zn2+ concentration as a function of total Zn2+ for baths with the individual agents. On the basis of the primary stability constants, deposition rate was predicted to decrease abruptly with reaction time for the EDTA bath, whereas baths with NTA or citrate should provide deposition rates that decrease only slightly over time. The predicted deposition profiles of the three baths were observed experimentally using a continuous-flow microreactor for CBD and were supported by the measured total Zn2+ concentration profiles. Understanding and predicting the dynamic behavior of complexing agents by simulation enables strategic design of CBD processes for many material systems.