Preparation and Characterization of ZnO: In Transparent Conductor by Low Cost Dip Coating Technique

Abstract

Transparent conducting oxide (TCO) based on indium doped zinc oxide films in the nano scale were successfully prepared using combination between dip coating and thermal decomposition process. Structural investigations confirm the polycrystalline ZnO hexagonal wurtzite phase grown along the c-axis with nano crystallite size about 10 nm. Morphology investigation shows that ZnO films consist of fine grains of average size 40 nm. This indicates that each grain contains several crystallites with different orientations. Cross sectional image presents good adhesion of the films with the substrate and the film thickness has been determined. Compositional analysis detects the indium content in the host ZnO matrix, the In/Zn ratio is close to the calculated concentration ratios of the precursor. The optical transmittance shows that the films are transparent in the UV and VIS-IR spectral region and interference fringes were observed to be thickness dependent. Preparation parameters were investigated and optimized such as dipping rate, number of deposition cycles, precursor concentration, annealing process and In/Zn ratio. Optimization process was investigated for low resistivity, high optical spectral window transmission and easy preparation process. Dipping rate in the range 2 - 38 mm/s is the most suitable range for good film quality while dipping rate range 30 - 38 mm/s produces thicker films in lower deposition cycles. The higher dipping rate produces films with lower transparency (milky films) while the small deposition rate rate requires large number of deposition cycles in order to increase the thickness. Besides, the higher dipping rate reflects lower resistivity of the deposited films. Precursor molar concentration was observed to have an essential effect on the film thickness, film quality and transparency. Lower precursor concentration requires also large number of deposition cycles for thickening the films. The higher concentration results also milky films (high scattering process by powder film). Precursor concentrations in the range 0.7 - 0.9 mol/liter were found to be the optimal for better quality and for faster deposition process. The resistivity of the films has been reduced from the range 1.5 - 2.5 kW?cm to the range 100 - 400 W.cm as the molar concentration reaches the range 0.07 - 0.09 mol/liter. The resistivity of films increases from 330 to 1686 <img src="http://chart.googleapis.com/chart?cht=tx&chl=%5COmega%20" style="border:none;" />.cm as the decomposition temperature increases from 200<img src="http://chart.googleapis.com/chart?cht=tx&chl=%5Ccirc%20" style="border:none;" />C to 350<img src="http://chart.googleapis.com/chart?cht=tx&chl=%5Ccirc%20" style="border:none;" />C. Annealing at 450<img src="http://chart.googleapis.com/chart?cht=tx&chl=%5Ccirc%20" style="border:none;" />C process after completing the decomposition at 200?C results the lowest resistivity with annealing time in the range 1.5 - 2 h. In/Zn percentage in the range 1.5% - 5% produces the low...

Electron mobility in oxide heterostructures

“…Introducing other potential dopants into the ZnO thin film have previously been studied for e.g. In-doped ZnO (IZO) [109] and In-and Ga-doped ZnO (IGZO) [110]. The Al-doped ZnO (AZO) has been considered to be one of the best candidates as a transparent conductor due to the relative low cost, the natural abundance of Zn and Al as well as the good optical transmission of this compound in the visible range.…”

“…The dependence of electron mobility with The dependence of the room temperature electron mobility, µ, on the corresponding bulk carrier density, n 3D , for bulk conducting ZnO-based systems. The data is obtained from: Aldoped ZnO (AZO)/Glass [111]; In-and Ga-codoped ZnO (IGZO) on yttrium-stabilied zirconium (YSZ) [79]; Ga-doped ZnO (GZO)/ ZnO [112]; ZnO/SCAM [109]; ZnO/Sapphire [109], Ga-doped ZnO/Sapphire (Ga-ZnO/Sapphire) [108].…”

Influence of precursor concentration on the structural, optical and electrical properties of indium oxide thin film prepared by a sol–gel method

“…As observed from Fig. 4, 0.30 M indium oxide thin film didn't show the complete absorption edge and this is due to the small film thickness [29].…”

Indium doped ZnO nano-powders prepared by RF thermal plasma treatment of In2O3and ZnO

“…7) In addition, the use of high crystalline IZO nano-particles was also shown to be preferable for efficient deposition of IZO films by ink-jet, dip-coating, and spin-coating, which employ well-dispersed IZO solution to obtain crystalline thin films through a drying process at relatively low temperatures. [10][11][12] IZO nano-powders for TCO applications have mainly been prepared by conventional wet-chemical processes, such as the co-precipitation, sol-gel and hydro thermal synthesis methods. [13][14][15][16] Depending on the preparation method used, a variety of resulting morphologies have been reported, including sphere, 16) prism-like, 15) flake-shaped, 14,15) and multi-pods, 17,18) which are also influenced by the indium content.…”