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Sains Malaysiana 47(11)(2018): 2863–2867 http://dx.doi.org/10.17576/jsm-2018-4711-29
Effect of Radio Frequency Power on a-CNx
Film Properties and Its Performance as Humidity Sensors (Kesan Kuasa Frekuensi
Radio terhadap Sifat Filem Nipis a-CNx dan Prestasinya sebagai Pengesan Kelembapan) ROZIDAWATI AWANG*,
NOORAIN
PURHANUDIN
& NUR SAKINAH SALMAN Pusat Pengajian
Fizik Gunaan, Fakulti Sains & Teknologi, Universiti Kebangsaan
Malaysia, 43600 UKM Bangi, Selangor Darul Ehsan, Malaysia Received: 14 March
2017/Accepted: 26 July 2018 ABSTRACT A series of amorphous carbon
nitride (a-CNx) thin films were deposited on
silicon (111) substrates using a home-built radio frequency plasma
enhanced chemical vapor deposition (RF-PECVD) system. The a-CNx
thin films were deposited from a mixture of a fixed flow-rate
of ethane (C2H6,
20 sccm) and nitrogen (N2, 47 sccm) gases with varying RF
power. A higher ratio of C to H (C to H ratio is
1:3) atoms in C2H6 as
compared to the ratio in methane (CH4) gas (C to H ratio is 1:4) is
expected to produce an interesting effect to the film properties
as humidity sensor. The characterization techniques used to determine
the morphology and chemical bonding of the thin films are field
emission scanning electron microscopy (FESEM)
and Fourier transform infrared spectroscopy (FTIR),
respectively. The variation of morphology and the existence of
nitrile band in these samples are correlated with the electrical
properties of a-CNx
thin films. Using humidity sensing system, the sensing performance
of the samples was examined. It was found that the response of
sensors towards the percentage of relative humidity (% RH) change is good resistive responses
and good repeatability. The sensitivity of the prepared a-CNx
thin films is significantly higher (up to 79%) as compared to
previous studies using CH4 or acetylene as precursor gas. Based on these results,
the properties and the sensitivity of the a-CNx
thin films towards humidity can be tailored by using an appropriate
precursor gases and deposition parameters. Keyword: Chemical bonding;
electrical properties; nitrile band; PECVD ABSTRAK Satu siri filem nipis nitrida
karbon amorfus (a-CNx) telah dimendapkan di
atas substrat silikon (111) menggunakan sistem pemendapan wap
kimia secara peningkatan plasma berfrekuensi radio (RF-PECVD) yang dibangunkan sendiri.
Filem nipis a-CNx ini dimendapkan daripada
campuran gas etana (C2H6, 20
sccm) dan nitrogen (N2, 47 sccm) pada kadar aliran gas malar
dengan ubahan kuasa RF. Nisbah atom C terhadap atom H yang
lebih tinggi dalam (C2H6, nisbah
C kepada H ialah 1:3) berbanding nisbah tersebut untuk gas metana
(CH4,
nisbah C kepada H ialah 1:4) dijangka memberi kesan yang lebih
baik kepada sifat filem nipis a-CNx sebagai
pengesan kelembapan. Teknik pencirian yang telah digunakan untuk
menentukan morfologi dan ikatan kimia filem nipis a-CNx
masing-masing ialah mikroskop imbasan elektron pancaran medan
(FESEM)
dan spektroskopi transformasi Fourier inframerah (FTIR).
Perubahan morfologi permukaan dan kewujudan kumpulan berfungsi
ikatan nitril di dalam sampel filem nipis ini dikaitkan dengan
sifat elektriknya. Prestasi sampel sebagai pengesan kelembapan
diuji dengan menggunakan sistem pengesan kelembapan. Pengujian
tersebut menunjukkan tindak balas yang jelas iaitu berlaku perubahan
rintangan sampel dan kebolehulangan pengesanan oleh sampel dalam
peratus kelembapan relatif (% RH) yang berbeza. Kepekaan filem
nipis a-CNx yang disediakan dalam kajian
ini terhadap kelembapan adalah lebih tinggi (sehingga 79%) berbanding
kepekaannya dalam kajian sebelum ini yang menggunakan gas CH4 atau
asetilena sebagai gas pelopor. Berdasarkan keputusan ini, sifat
dan kepekaan pengesanan kelembapan filem nipis a-CNx boleh
diubah suai dengan menggunakan gas pelopor dan parameter pemendapan
yang tertentu. Kata kunci: Ikatan kimia; ikatan nitril; PECVD;
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Surface and Coatings Technology 258: 716-721. *Corresponding author; email: rozida@ukm.edu.my
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