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

 

Diserahkan: 14 Mac 2017/Diterima: 26 Julai 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; sifat elektrik

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

 

 

 

 

 

 

 

 

 

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