The structure, photoluminescence, optical and magnetic properties of ZnO films doped with ferromagnetic impurities

Controlling the Structural Properties of Single Step, Dip Coated ZnO Seed Layers for Growing Perfectly Aligned Nanowire Arrays

“…It is well-known that mixing zinc acetate dihydrate (ZAD, Zn­(CH 3 COO) 2 ·2H 2 O) and monoethanolamine (MEA, C 2 H 7 NO) in absolute ethanol, for instance, can produce fairly well-textured ZnO thin films. This can further be enhanced by the use of standard annealing process such as baking for 10 min at 300 °C and then annealing at high temperature around 500 °C (i.e., close to the highest temperature achievable on a hot plate) for 1 h. ,− However, the fundamental mechanisms responsible for the film formation and structural ordering are still not completely understood. The texture along the c -axis as a critical requirement has, for example, been found to increase, decrease − or only vary ,,,, with the solution concentration.…”

“…This can further be enhanced by the use of standard annealing process such as baking for 10 min at 300 °C and then annealing at high temperature around 500 °C (i.e., close to the highest temperature achievable on a hot plate) for 1 h. ,− However, the fundamental mechanisms responsible for the film formation and structural ordering are still not completely understood. The texture along the c -axis as a critical requirement has, for example, been found to increase, decrease − or only vary ,,,, with the solution concentration. Particle/substrate interactions or particle/particle interactions have been suggested as playing an important role here.…”

“…Similarly, although widely supported by the experimental results (see, for instance, ref and therein), the Landau–Levich theory has been unable to predict the thickness of ZnO thin films deposited by dip coating. , Currently, the occurrence of controversial results can mainly be explained by the systematic use of multi-dip processes (i.e., multi-layers), leading to fairly thick ZnO thin films and, correlatively, to cross-studied parameters. Furthermore, standard annealing processes have been shown to be insufficient owing to the resulting high porosity and roughness of ZnO thin films, for instance, limiting in turn their efficient integration as seed layers into ZnO NW-based devices. − The use of high-temperature annealing process has recently been applied to thick films deposited by dip coating through multi-dip processes to form strongly textured films. ,,,− , By combining multi-dip processes with an annealing temperature higher than 800 °C, the formation of thick films consisting of ZnO NPs with an average diameter of almost 200 nm has been reported. ,, In such processes, the film thickness or other parameters such as the solution concentration or the withdrawal speed may only affect slightly the ZnO film texture and its surface morphology. ,, However, despite their high potential, the use of multi-deposit films is strongly detrimental for their integration into ZnO NW-based devices owing to their large thickness and, correlatively, high roughness. The large film thickness can also enhance the optical absorption of these multi-deposit films when used in nanostructured solar cells, which should be avoided as much as possible.…”

Effects of sol concentration on structural, morphological and optical waveguiding properties of sol-gel ZnO nanostructured thin films

“…For example, effect of sol concentration on c axis orientation was studied by several groups. Some studies have shown that the best c axis orientation is obtained from the films deposited at 0.3 M [27,28,30]. These authors have…”

“…However, the properties of the prepared films by sol-gel can be affected by several factors. These factors include sol aging time [22,23], nature of the precursor and its concentration [24][25][26][27][28][29][30][31][32][33], type of solvent [34], stabilizer agents [35], preheating temperature [36] and post-annealing temperature [37]. Moreover, the optical waveguiding properties of the film strongly depend on the microstructure of the material, surface roughness, porosity and grain size which are connected to the fabrication process parameters such as dip-coated speed, sol concentration, treatment temperature and number of coating layers.…”