Sains Malaysiana 42(12)(2013): 1781–1786

Effect of Annealing Temperature on the Structural and Optical Properties of

Nanocrystalline ZnO Thin Films Prepared by Sol-gel Method

(Kesan Suhu Sepuhlindap Terhadap Struktur dan Sifat Optik Filem Nipis ZnO Nanohablur

Disediakan dengan Kaedah Sol-gel)

N.B. IBRAHIM¹*, S.M. Al-Shomar² & S.H. AHMAD¹

¹School of Applied Physics, Faculty of Science and Technology, Universiti Kebangsaan Malaysia

43600 UKM Bangi, Selangor, Malaysia

²Physics Department, Faculty of Science, Hail University, Kingdom of Saudi Arabia  

Diserahkan: 19 November 2012/Diterima: 1 April 2013

ABSTRACT

Undoped zinc oxide (ZnO) thin films were prepared by a sol-gel method. The effect of annealing temperature from 500 to 700°C on the structural and optical properties of the films was studied. The films nanostructure characterized by  the X-ray diffraction method showed that the films were single phase ZnO with wurtzite structure. The surface morphology studied using the field emission scanning electron microscope showed that the thickness of the films increased with the increment of annealing temperature. The grain size of the films increased with the increment of the annealing temperature. The film surface roughness measured using the atomic force microscope showed that the surface roughness of the film decreased (from 2.3 to 1.02 nm ), when the annealing temperature increased from 500 to 600°C then it increased to 3.06 nm at 700°C. The optical properties were studied by the UV-Vis spectrophotometer. The results showed that the films had high transmittance (above 80%) in the visible range and the exciton absorption occurred at a wavelength of 379 nm. The energy gap decreased with the increment of annealing temperature.

Keywords: Annealing; optical; sol-gel; XRD; ZnO films

ABSTRAK

Filem nipis ZnO tak terdop telah disediakan dengan kaedah sol-gel. Kesan suhu sepuhlindap daripada 500 to 700°C terhadap struktur dan sifat optik filem telah dikaji. Nanostruktur filem yang dicirikan dengan kaedah pembelauan sinar-X menunjukkan bahawa filem adalah ZnO sefasa dengan struktur wurtzit. Morfologi permukaan yang telah dikaji dengan mikroskop elektron imbasan pancaran medan menunjukkan bahawa ketebalan filem bertambah dengan pertambahan suhu sepuhlindap. Saiz butiran filem meningkat dengan pertambahan suhu sepuhlindap. Kekasaran permukaan filem telah diukur dengan mikroskop daya atom menunjukkan bahawa kekasaran permukaan filem berkurangan (daripada 2.3 ke 1.02 nm) apabila suhu sepuhindap bertambah daripada 500 ke 600°C kemudian meningkat ke 3.06 nm pada 700°C. Sifat optik telah dikaji dengan spektrofotometer UV-Vis. Hasil menunjukkan bahawa filem mempunyai transmisi yang tinggi (lebih 80%) dalam julat nampak dan penyerapan eksiton berlaku pada panjang gelombang 379 nm. Jurang tenaga berkurangan dengan penambahan suhu sepuhlindap.

Kata kunci: Filem ZnO; optik; sepuhlindap; sol-gel; XRD

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*Pengarang untuk surat-menyurat; email: baayah@ukm.my