Sains Malaysiana 46(3)(2017): 509–514

http://dx.doi.org/10.17576/jsm-2017-4603-20

Characterization of a-CNxThin Films Prepared by RF-PECVD Technique for

Humidity Sensor

(Pencirian ke atas Filem Nipis a-CNx daripada Teknik RF-PECVD sebagai Pengesan Kelembapan)

R. AWANG*, N.F.H AZIZ, N. PURHANUDIN & Z. ZALITA

Pusat Pengajian Fizik Gunaan, Fakulti Sains dan Teknologi, Universiti Kebangsaan Malaysia,

43600 UKM Bangi, Selangor Darul Ehsan, Malaysia

Received: 1 June 2013/Accepted: 1 June 2016

ABSTRACT

In this work, amorphous carbon nitride (a-CNx) thin films were deposited by radio frequency (RF) plasma enhanced chemical vapor deposition (RF-PECVD) technique. The RF power and gas mixture of methane (CH₄) and nitrogen (N₂) flow was kept constant, while the electrode distance was varied from 1 to 6 cm. The effect of electrode distance on the chemical bonding, morphology and humidity sensing responses of the films were investigated. Fourier transform infra-red spectroscopy (FTIR) studies showed a systematic change in the spectra and showed three main peaks namely the G and D-peak, C≡N triple bonds and C-H/O-H groups. Uniform and porous morphology was observed for films deposited at smallest distance followed by non-porous cubicle-like grain as electrode distance increased. Subsequently formation of vertically aligned nanostructures apparent both from its surface and cross section images by increasing of electrode distance to the fullest. The humidity sensing property has been studied by recording their resistance response to relative humidity (RH) at room temperature. It was found that the resistance value decreases from 15.4 to 3.6 kΩ with the increase in RH from 9 to 85%, with the highest sensitivity of 77% for film deposited at smallest distance of 1 cm.

Keywords: Electrode distance; nitrile bands; resistance

ABSTRAK

Dalam penyelidikan ini, filem nipis karbon nitrida amorfus (a-CNx) disediakan menggunakan teknik pemendapan wap kimia secara peningkatan plasma (RF-PECVD) berfrekuensi radio (RF). Kuasa RF dan kadar aliran campuran gas yang terdiri daripada metana (CH₄) dan nitrogen (N₂) dikekalkan malar, manakala jarak elektrod diubah pada 1 hingga 6 cm. Kesan perubahan jarak elektrod semasa proses pemendapan filem ke atas ikatan kimia, morfologi dan tindak balas pengesanan kelembapan filem dikaji. Pencirian menggunakan spektroskopi transformasi Fourier inframerah (FTIR) menunjukkan perubahan sistematik pada spektrum dan menunjukkan tiga puncak utama yang dikenali sebagai puncak G dan D, ikatan ganda tiga C≡N dan kumpulan C-H/O-H. Filem a-CNx menunjukkan morfologi berongga apabila filem dimendapkan pada jarak elektrod paling hampir diikuti dengan morfologi filem tidak berliang dan butiran berbentuk kubus apabila jarak elektrod ditingkatkan. Pembentukan struktur-nano yang menegak dan sejajar amat jelas kelihatan pada kedua-dua imej daripada permukaan dan keratan rentas filem yang dimendapkan pada jarak elektrod paling jauh. Sifat pengesanan kelembapan dikaji dengan merekodkan nilai rintangan filem dalam kelembapan relatif (RH) yang berbeza pada suhu bilik. Nilai rintangan didapati berkurang daripada 15.4 kepada 3.6 kΩ dengan peningkatan kelembapan relatif (RH), 9 hingga 85%. Kepekaan terhadap kelembapan tertinggi dicapai sebanyak 77% oleh filem yang dimendap pada jarak elektrod yang terhampir iaitu 1 cm.

Kata kunci: Ikatan nitril; jarak elektrod; rintangan

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*Corresponding author; email: rozida@ukm.edu.my