Sains Malaysiana 42(5)(2013): 643–648

 

Formation of Porous Silicon: Mechanism of Macropores Formation

in n-Type Si

(Pembentukan Silikon Berliang: Mekanisme Pembentukan Liang Makro dalam Si Jenis-n)

 

 

Nurul Izni Rusli, Mastura Shafinaz Zainal Abidin, Budi Astuti & Nihad K. Ali

Faculty of Electrical Engineering, Universiti Teknologi Malaysia, 81310 Skudai, Johor, Malaysia

 

Abdul Manaf Hashim*

Malaysia-Japan International Institute of Technology (MJIIT)

Universiti Teknologi Malaysia International Campus, Jalan Semarak 54100 Kuala Lumpur

Malaysia

 

Received: 7 January 2012/Accepted: 21 May 2012

 

ABSTRACT

We report the formation of macropores in n-Si (100) substrates for different etching times of 20, 40 and 60 min at a constant current density of 25 mA/cm2 under front-side illumination in HF:ethanol (1:4) solution. After etching for 20 min, four-branch-shaped pores of various sizes were observed at discrete locations. Etching time of 40 min led to the formation of highly connected four-branch-shaped pores as the branches of adjacent pores appeared to connect to each other. As the etching time was increased further to 60 min, the density of interconnected branches increased remarkably. The macropore formation process occurred in three consecutive phases. The current burst model was used to discuss this process. Formation of four-branch-shaped pores at random locations were observed because current bursts are more likely to nucleate where other current bursts took place initially.

 

Keywords: Electrochemical etching; etching time; illumination; porous silicon

 

ABSTRAK

Kami melaporkan pembentukan liang makro dalam substrat Si(100) jenis-n untuk masa punaran yang berbeza iaitu 20, 40 dan 60 min pada ketumpatan arus malar sebanyak 25 mA/cm2 di bawah pencahayaan arah depan dalam larutan HF:etanol (1:4). Selepas punaran selama 20 min, liang-liang bercabang-empat pelbagai saiz dapat diperhatikan pada lokasi tertentu. Masa punaran 40 min menyebabkan pembentukan liang-liang bercabang-empat yang bersambungan kerana cabang pada liang-liang bersebelahan telah muncul untuk menyambung antara satu sama lain. Apabila masa punaran dilanjutkan kepada 60 min, ketumpatan cabang-cabang yang saling bersambungan meningkat dengan ketara. Pembentukan liang makro ini berlaku dalam tiga fasa berturut-turut. Model limpahaan arus telah digunakan untuk membincangkan proses ini. Pembentukan liang-liang bercabang-empat pada lokasi rawak telah diperhatikan kerana limpahan arus lebih cenderung untuk terbentuk pada tempat limpahan arus yang telah berlaku sebelumnya.

 

Kata kunci: Masa punaran; pencahayaan; punaran elektrokimia; silikon berliang

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*Corresponding author; email: manaf@fke.utm.my

 

 

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