Sains Malaysiana 46(10)(2017): 1951–1958

http://dx.doi.org/10.17576/jsm-2017-4610-34

 

Kesan Kuasa Frekuensi Radio terhadap Komposisi Ikatan Kimia Filem Nipis a-CNx sebagai Pengesan Kelembapan

(Influence of RF Power on Chemical Bonding Composition on a-CNx Thin Films as Humidity Sensor)

 

SITI AISYAH ABD AZIZ & ROZIDAWATI AWANG*

 

Pusat Pengajian Fizik Gunaan, Fakulti Sains dan Teknologi, Universiti Kebangsaan Malaysia, 43600 UKM Bangi, Selangor Darul Ehsan, Malaysia

 

Diserahkan: 30 Jun 2017/Diterima: 7 September 2017

 

ABSTRAK

Filem nipis a-CN_x mempunyai ikatan kimia C-N (sp³), C=N (sp²) dan C≡N (sp¹). Ikatan C=N dan C≡N mudah diputuskan oleh serangan hidrogen semasa proses pemendapan filem untuk membentuk ikatan C-H dan N-H. Pembentukan komponen sp² grafit dalam filem nipis a-CN_x yang disebabkan oleh kewujudan atom nitrogen menyumbang kepada penurunan rintangan elektrik dan peningkatan kekonduksian elektrik. Ciri ini adalah penting untuk aplikasi filem nipis a-CN_x sebagai pengesan kelembapan. Dalam kajian ini, filem nipis karbon nitrida amorfus (a-CN_x) disediakan di atas substrat kuartza dan silikon (111) menggunakan teknik PECVD. Sampel disediakan pada kuasa frekuensi radio (RF) yang berbeza iaitu pada 40, 50, 60, 70 dan 80 W dan dikaji kesannya ke atas komposisi ikatan kimia dan morfologi filem serta keupayaannya sebagai pengesan kelembapan. Puncak D (sp²C) dan G (sp³C) yang jelas dicerap menggunakan spektroskopi Raman dalam semua filem nipis a-CN_x yang disediakan dengan keamatan tertinggi didapati pada kuasa RF 70 W. Mikrokgraf daripada mikroskop elektron imbasan pancaran medan (FESEM) menunjukkan morfologi permukaan semua sampel mempunyai struktur butiran berbentuk seperti kobis bunga yang seragam. Spektroskopi fotoelektron sinar X (XPS) mengesahkan kehadiran ikatan C-C/C=C, C=N dan C≡N dalam filem nipis a-CN_x. Kesemua filem nipis a-CN_x yang dihasilkan menunjukkan tindak balas terhadap kelembapan berbeza dengan kepekaan antara 60-70%. Filem nipis a-CN_x yang disediakan pada kuasa RF 70 W menunjukkan kepekaan tertinggi kesan daripada ketakteraturan karbon dan kandungan sp³C yang lebih tinggi.

 

Kata kunci: Karbon nitrida; PECVD; saiz kelompok

 

ABSTRACK

The a-CN_x thin film has chemical bonding of C-N (sp³), C=N (sp²) and C≡N (sp¹). C=N and C≡N bonds are easily resolved by hydrogen attack during the film deposition process to form C-H and N-H bonds. The formation of graphite sp² components in the a-CN_x thin film caused by the presence of nitrogen atom contributes to the reduction of the electrical resistance and enhances the electrical conductivity. These features are essential for a-CN_x thin film application as a humidity sensor. In this study, amorphous carbon nitride films (a-CN_x) are deposited on the quartz and silicon (111) substrate using PECVD techniques. The samples were deposited at different RF power at 40, 50, 60, 70 and 80 W and analyzed their effects on film chemical composition and films morphology as well as their ability as humidity sensor. D (sp²C) peak and G (sp³C) peak are clearly observed using Raman spectroscopy in all a-CN_x thin films with the highest intensity obtained at RF 70 W. Films micrograph observed by field emission scanning electron microscopy (FESEM) show that surface morphology of all samples have a uniform structural shape of cauliflower. X-ray photoelectron spectroscopy (XPS) confirmed the presence of C-C/C=C, C=N and C≡N bonds in the a-CN_x thin film. All the a-CN_x thin films showed a response to different humidity with sensitivity between 60-70%. The a-CN_x thin film deposited at RF 70 W power indicates the highest sensitivity due to carbon disorder and higher sp³C content.

Keywords: Carbon nitride; cluster size; PECVD

 

 

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