Sains Malaysiana 42(9)(2013): 1327–1332
Effects
of the Nitric Acid Concentrations on the Etching Process, Structural
and
Optical Properties of Porous Zinc Oxide Thin Films
(Kesan Kepekatan Asid Nitrik Terhadap Proses Pemunaran, Ciri-ciri
Struktur
dan Optik Filem Nipis Zink Oksida Berliang)
C.G. Ching*, Leonard Lu, C.I. Ang, P.K. Ooi, S.S. Ng, Z. Hassan
& H. Abu Hassan
Nano-Optoelectronic Research and Technology Laboratory, School of
Physics,
Universiti Sains Malaysia, 11800, Penang, Malaysia
Diserahkan: 1 Ogos 2012/Diterima:
16 Disember 2012
ABSTRACT
The present study reports on the fabrication of porous zinc oxide
by wet chemical etching. ZnO thin films were deposited via radio-frequency
magnetron sputtering on p-type silicon with (111) preferred orientation. The
etchants used in the present work were 0.1% and 1.0% nitric acid (HNO3)
solutions. ZnO were etched at various times and were characterized by X-ray
diffraction (XRD), scanning electron microscopy (SEM)
and photoluminescence (PL) spectroscopy to allow the
examination of their structural and optical properties. The XRD results
revealed that the intensity of ZnO(002) decreased when the thin films were
etched in varying HNO3 concentrations
over different periods of time. The above observation is attributed to the
dissolution of the ZnO(002). The SEM images showed that the
thickness of the ZnO layers decreased over the etching time, which resulted
from the isotropic etching by the HNO3 solution.
The PL emission intensity initially increased with increasing
etching time. However, with further etching of the samples, the PL spectra
showed a decreasing trend in intensity as a result of the decrease in the
surface-to-volume ratio. All results lead to the conclusion that 1.0% HNO3 has
the capability to change the ZnO surface significantly.
Keywords: Photoluminescence spectroscopy; scanning electron
microscope; wet chemical etching; X-ray diffraction; zinc oxide
ABSTRAK
Penyelidikan ini melaporkan fabrikasi struktur zink oksida
berliang melalui proses punaran basah. Filem nipis ZnO dienapkan ke atas
substrat silikon (111). Larutan pemunar yang digunakan dalam kajian ini adalah
larutan asid nitrik (HNO3) yang berkepekatan 0.1%
dan 1.0%. Filem nipis ZnO dipunarkan selama beberapa jangka waktu yang
ditetapkan dan ciri-ciri struktur dan optik dikaji dengan menggunakan
pembelauan sinar-X (XRD), mikroskop elektron imbasan (SEM)
dan spektroskopi fotoluminesens (PL). Keputusan XRD menunjukkan
bahawa keamatan bagi puncak ZnO(002) menurun selepas filem nipis ZnO dipunarkan
dalam larutan yang berkepekatan berlainan untuk jangka waktu yang berlainan.
Pemerhatian ini adalah disebabkan penguraian ZnO(002) semasa proses punaran
filem nipis. Imej-imej daripada SEM pula menunjukkan ketebalan
filem nipis ZnO berkurangan dengan peningkatan masa punaran. Pemerhatian ini
adalah disebabkan proses punaran isotropik oleh larutan HNO3.
Manakala spektrum PL pada peringkat awal punaran
menunjukkan peningkatan keamatan puncak apabila masa punaran meningkat. Namun
begitu, proses punaran yang berterusan menunjukkan keamatan puncak PL mula
menunjukkan trend menurun dan fenomena ini adalah disebabkan penurunan nisbah
luas permukaan terhadap isi padu dalam filem nipis ZnO.
Kata kunci: Mikroskop elektron
pengimbas; pembelauan sinar-X; punaran basah; spektroskopi fotoluminesen;, zink
oksida
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*Pengarang untuk surat-menyurat; email: chingchinguan@gmail.com
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