Sains Malaysiana 43(7)(2014): 1077–1082

Fabrication of Porous ZnO Thin Films via Ammonium Hydroxide: Effects of

Etching Time and Oxidizer on Surface Morphology and Surface Roughness

(Fabrikasi Filem Nipis ZnO Berliang melalui Ammonium Hidroksida: Kesan Masa Punaran dan Pengoksida

 ke atas Morfologi dan Kekasaran Permukaan)

S.S. NG*, P.K. OOI, S. YAAKOB, M.J. ABDULLAH, H. ABU HASSAN & Z. HASSAN

Nano-Optoelectronics Research and Technology Laboratory, School of Physics,

Universiti Sains Malaysia, 11800, Penang, Malaysia

Received: 28 March 2013/Accepted: 27 December 2013

ABSTRACT

The effects of the etching time and oxidizer on the surface morphology and surface roughness of the porous zinc oxide (ZnO) thin films, which were formed using ammonium hydroxide (NH₄OH) were investigated. The etching time was varied from 1 to 5 min. The oxidizer used was hydrogen peroxide (H₂O₂) solution. The ZnO thin films were obtained using radio- frequency magnetron sputtering on n-type silicon (111) substrate. The thickness of the ZnO thin films was approximately 1.34 μm. The morphology, topography and surface roughness of the porous ZnO were characterized using scanning electron microscope (SEM) and atomic force microscope. The SEM results showed that the surface morphology of the as-grown ZnO film has a leaf-like structure. However, this structure transformed into irregularly shaped pores upon exposure of the ZnO thin films to the etchant solutions. Increased etching time corresponded to increased pore size, which concurrently resulted in the formation of granular ZnO. Finally, it was found that the etching rate increases with the addition of H₂O₂ in the NH₄OH solution.

Keywords: Ammonium hydroxide; hydrogen peroxide; porous ZnO; wet etching

ABSTRAK

Kesan masa punaran dan pengoksida ke atas morfologi dan kekasaran permukaan filem nipis zink oksida (ZnO) berliang yang dihasilkan dengan amonium hidroksida (NH₄OH) telah dikaji. Masa punaran diubah daripada 1 ke 5 min. Pengoksida adalah larutan hidrogen peroksida (H₂O₂). Filem nipis ZnO disediakan dengan menggunakan percikan pemagnetan frekuensi radio atas substrat silikon (111) jenis-n. Ketebalan filem nipis ZnO adalah lebih kurang 1.34 μm. Morfologi, topografi dan kekasaran permukaan ZnO berliang dicirikan dengan menggunakan mikroskop elektron imbasan (SEM) dan mikroskop daya atom. Keputusan SEM menunjukkan bahawa ZnO filem yang disediakan terdiri daripada lapisan struktur seperti dedaun. Walau bagaimanapun, struktur ini bertukar kepada bentuk liang yang tidak teratur apabila filem nipis ZnO terdedah kepada larutan pemunar. Peningkatan masa punaran sejajar dengan peningkatan saiz liang, yang serentak mengakibatkan pembentukan ZnO berbutir. Akhirnya, didapati bahawa kadar punaran meningkat dengan penambahan H₂O₂ dalam larutan NH₄OH.

Kata kunci: Amonium hidroksida; hidrogen peroksida; punaran basah; ZnO berliang

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*Corresponding author; email: shashiong@yahoo.com