Sains Malaysiana 42(12)(2013): 1811–1814

Clusters of GaAs Prepared by Quantum Mechanical DFT and the Nanowire Raman Spectra

(Penyediaan Kluster GaAs Menggunakan DFT Kuantum Mekanik dan Spektrum Raman Nano Wayar)

AHMAD NAZRUL ROSLI¹*, HASAN ABU KASSIM² & KESHAV N. SHRIVASTAVA²

¹Faculty Science and Technology, Universiti Sains Islam Malaysia (USIM), 71800 Nilai,

Negeri Sembilan, Malaysia

²Department of Physics, University of Malaya, 50603 Kuala Lumpur, Malaysia  

Diserahkan: 19 November 2012/Diterima: 1 April 2013

ABSTRACT

We studied the clusters of GaAs by using the density functional theory simulation to optimize the structure. We determined the binding energy, bond lengths, Fermi energy and vibrational frequencies for all of the clusters. We use the Raman data of nanowires of GaAs to compare our calculated values with the experimental values of the vibrational frequencies. The nanowire of GaAs gives a Raman line at 256 cm^-1 whereas in the bipyramidal Ga₂As₃ the calculated value is 256.33 cm^-1. Similarly 285 cm^-1 found in the experimental Raman data agrees with 286.21 cm-1 found in the values calculated for Ga₂As₂ (linear) showing that linear bonds occur in the nanowire. The GaAs is found in two structures zinc-blend as well as wurtzite structures. In the nanowire mixed structures as well as clusters are formed.

Keywords: Cluster; DFT; GaAs; raman spectra; vibrational frequencies

ABSTRAK

Kluster GaAs menggunakan simulasi teori fungsi ketumpatan untuk mengoptimumkan struktur telah dikaji. Tenaga ikatan, panjang ikatan, tenaga Fermi dan frekuensi getaran untuk semua kluster telah diperoleh. Kami menggunakan data Raman untuk nano wayar bagi GaAs untuk membuat perbandingan frekuensi getaran antara hasil pengiraan kami dengan hasil eksperimen. Garis Raman bagi GaAs nano wayar adalah pada 256 cm-1 manakala hasil pengiraan kami untuk Ga₂As₃ dwi-piramid adalah 256.33 cm^-1. Begitu juga dengan nilai 285 cm^-1 yang dijumpai pada data eksperimen Raman yang setara dengan hasil pengiraan kami 286.21 cm^-1 yang dijumpai daripada pengiraan untuk Ga₂As₂ (linear) yang menunjukkan ikatan linear wujud dalam nano wayar. GaAs ditemui dalam dua struktur iaitu zink-blende serta dalam struktur wurtzite. Dalam nano wayar, struktur campuran dan kluster didapati wujud.

Kata kunci: DFT; frekuensi getaran; GaAs; kluster; spektra Raman

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*Pengarang untuk surat-menyurat; email: anazrul84@yahoo.com