Doping strategies for highly conductive Al-doped ZnO films grown from aqueous solution

Abstract

Aluminum‐doped zinc oxide (AZO) thin films are prepared by a low temperature (100 °C) aqueous solution deposition method with a subsequent UV post‐deposition treatment at 140 °C. Film growth is governed by the retrograde solubility of zinc–ammine complexes at basic conditions (pH 11.4). Aluminum was introduced into the film as a dopant by co‐precipitation, either using an aluminum metal foil or aluminum nitrate as a precursor. As the presence of Al ions in the solution influences the film morphology as well as the opto‐electronic properties, different profiles of the dopant supply were examined and optimized with respect to the optical and electrical properties of the AZO layer. It was found that independent of the chosen aluminum precursor a linearly increasing dopant concentration in the solution is favorable for achieving dense, highly transparent (<8% absorption between 400 and 900 nm) AZO thin films with a lowest resistivity of 3.4 × 10−3 Ω cm.

Highly transparent and conductive indium-doped zinc oxide films deposited at low substrate temperature by spray pyrolysis from water-based solutions

“…The most prominent absorption peak is located at 1117 cm -1 and corresponds to the Si-O stretching vibration of the substrate (m SiO ) [27]. Further peak assignment was conducted according to the literature [28]. A broad minimum located around 3600 cm -1 is observed, which can be attributed to O-H stretching vibrations (m OH ).…”

Polyol synthesized aluminum doped zinc oxide nanoparticles - influence of the hydration ratio on crystal growth, dopant incorporation and electrical properties

“…Since the price for the most commonly used TCO Indium Tin Oxide (ITO) rises enormously due to a rapidly growing demand and rare earth abundance of Indium, a cost effective alternative with comparable quality is needed. Aluminum Zinc Oxide (AZO) as alternative TCO reaches the most interest, because the precursors are nontoxic, cheap and earth-abundant [1,2,3]. There are diverse established physical and chemical techniques as sputtering, evaporation, pulsed laser deposition, chemical vapour deposition or sol-gel technique to deposit thin TCO films directly on substrate [4,5].…”

Comparison of chemical bath-deposited ZnO films doped with Al, Ga and In

“…This concept was used by several groups to deposit intrinsic [9] and doped ZnO thin films [10][11][12][13][14]. The key to obtain dense materials rather than nanorods was in all approaches the use of citrate as structuredirecting agent, which selectively decelerates crystal growth along the ZnO c-axis [9,15].…”

“…Hagendorfer et al reported Al-doped ZnO layers with resistivity values in the range of 10 -3 X cm, using the aforementioned CBD chemistry. To achieve low resistivity values, ultraviolet (UV)-light annealing instead of thermal annealing was used, permitting to maintain the temperature below 85°C during the whole production process [10,11].…”