Stability of Sputter Deposited ZnO:Cr Films Against Acids

Abstract

ZnO:Cr films were deposited on water-cooled soda-lime glass substrates at room temperature in an Ar atmosphere by rf magnetron sputtering of a ZnO target on which Cr chips were placed. The films exhibited extraordinary stability against acids such as HCl or HNO3, and also high resistivities similar to those of ZnO films. The addition of Cr suppressed the growth of ZnO grains which resulted in the formation of a dense film with a smooth surface. The stability ahd high resistivity displayed by the ZnO:Cr films can be attributed to the formation of a chromium-oxide-rich grain boundary.

Solid State Reactions in Cr<sub>2</sub>O<sub>3</sub>-ZnO Nanoparticles Synthesized by Triethanolamine Chemical Precipitation

“…Besides, it was observed at room temperature using a higher chromium content (16.0 at%), the presence of a second compound, probably of the form 2ZnO·Cr 2 O 3 ·nH 2 O, transforming at 400˚C into a Cr-ZnO solid solution incorporating 16.0 at% chromium in the wurtzite ZnO structure and remaining in the nanometric domain (30 nm). The most plausible solid state reactions involved during thermal treatment were proposed according to reactions (4) and (5). Finally, crystalline strain-free ZnCr 2 O 4 nanoparticles can be promoted with annealing treatment at 400˚C.…”

“…It has been established that some spinels have advanced gas sensing and catalytic properties [4], so ZnCr 2 O 4 could be a suitable sensors for aggressive environments because chromium improves the stability of ZnO films against diluted hydrochloric and nitric acid media [5]. Besides Cr 2 O 3 -ZnO materials, specially prepared in nanocrystalline state are interesting systems for H 2 production via photoelectrochemical splitting of water [6].…”

Low wet etching rates of ZnO films prepared by sputtering of mixed ZnO and AlN powder targets

“…These properties can be modified by the addition of insoluble inclusions. For instance, Cr-doped ZnO films possessed the high stability against acidic solutions through the formation of Cr 2 O 3 , which was responsible for an increase of the resistivity, 0.71-32.3 Ω cm [8,9]. The addition of insoluble inclusions to a ZnO film can't satisfy the requirement of a low etching rate and a high conductivity.…”

Influence of hydrogen peroxide solution on the properties of ZnO thin films

“…Research indicates that ZnO has high decomposition temperature of 1800 C, melting point of 1975 C, and a resistance to megaelectron-volt(MeV) proton irradiation at room temperature [4]. But it can react with acid and alkali, especially to acid [5]. So it is worthwhile to study the cleaning solution used for ZnO surfaces.…”