Implementing the Reactor Geometry in the Modeling of Chemical Bath Deposition of ZnO Nanowires

Abstract

The formation of nanowires by chemical bath deposition is of great interest for a wide variety of optoelectronic, piezoelectric, and sensing devices, from which the theoretical description of their elongation process has emerged as a critical issue. Despite its strong influence on the nanowire growth kinetics, reactor size has typically not been taken into account in the theoretical modeling developed so far. We report a new theoretical description of the axial growth rate of nanowires in dynamic conditions based on the solution of Fick’s diffusion equations, implementing a sealed reactor of finite height as a varying parameter. The theoretical model is applied in various chemical bath deposition conditions in the case of the growth of ZnO nanowires, from which the influence of the reactor height is investigated and compared to experimental data. In particular, it is found that the use of reactor heights smaller than 2 cm significantly decreases the ZnO nanowires’ axial growth rate in typical experimental conditions due to the faster depletion of reactants. The present approach is further used predictively, showing its high potential for the design of batch reactors for a wide variety of chemical precursors and semiconductor materials in applied research and industrial production.

Effects of Zinc Nitrate and HMTA on the Formation Mechanisms of ZnO Nanowires on Au Seed Layers

“…A slight increase in the pH during the CBD process can however be observed for C 0 values ranging from 1 to 30 mM. This can be attributed to the progressive hydrolysis of HMTA molecules yielding the formation of additional HO – ions according to the following chemical reactions , This increase in pH value can also be associated with a slower kinetics of consumption of HO – ions at the growing facets of ZnO NWs, which is directly related to the crystallization process as indicated by the following chemical reactions , The rate of ZnO crystallization in the chemical bath is indeed known to decrease over time due to the progressive depletion of the reactants, as evidenced in refs , .…”

Mapping the Optomechanical Coupling Mediated by Light among Mechanical Resonators Including Multilayer Cavity and Molecules

“…The multishape features start growing after nucleation, and the micrograph in Figure b indicates that after 22 min from AgNO 3 addition in the reaction vessel, their length is L = 1 μm. Under the hypothesis of static growth described by the equation L = k C scriptD ϱ Ag scriptD + ϱ Ag k S t (section S1 of the Supporting Information), the elongation mechanism is slightly underestimated, and the length reaches 1 μm 26 min after the start of the reaction (Figure c). The difference in length might be attributed to the model’s simplification of the static hypothesis, which overlooks the mixing effect that is maximized during the trials.…”

“…Ag Ag 34 (section S1 of the Supporting Information), the elongation mechanism is slightly underestimated, and the length reaches 1 μm 26 min after the start of the reaction (Figure 1c). The difference in length might be attributed to the model's simplification of the static hypothesis, which overlooks the mixing effect that is maximized during the trials.…”

Highly C-oriented (002) plane ZnO nanowires synthesis

“…The positions of the lines and their widths at mid-height corresponding to the vibrational mode assignments are summarized in Table 3. 11,19 The modes observed at 115, 300, 520 and 970 cm −1 are assigned to silicon substrate specic modes. 21,22 As shown in Fig.…”

“…[15][16][17] The chemical bath deposition (CBD) technique has attracted the interest of the research community due to its simplicity, cost efficiency, low temperature and environmentally friendly growth deposition, as well as its ability to scale up to large areas for commercial production. 18,19 However, the relationships between the buffer layer and C-oriented NWs properties with preferential (002) planes are rather few addressed in the literature.…”