Sains Malaysiana 40(1)(2011): 35–37

Theoretical and Experimental Studies of Polarized Infrared Reflectance of Bulk Wurtzite ZnO Semiconductor

(Kajian Teori dan Eksperimen bagi Spektrum Pantulan Inframerah Terkutub untuk Semikonduktor ZnO Wurtzit Pukal)

S.C. Lee*, S.S. Ng, Z. Hassan & H. Abu Hassan

Nano-Optoelectronics Research and Technology Laboratory, School of Physics

Universiti Sains Malaysia, 11800 Minden, Penang, Malaysia

Diserahkan: 7 Disember 2009 / Diterima 13 Julai 2010

ABSTRACT

Polarized infrared (IR) reflectance spectrum studies of bulk wurtzite ZnO are presented. The features of the polarized IR reflectance spectra and the optical characteristics of ZnO were investigated. Based on the anisotropic dielectric function model, the experimental IR reflectance spectra were numerically fitted by the theoretical IR reflectance spectra. The obtained transverse optical (TO) and longitudinal optical (LO) frequencies, i.e., ωTO⊥(ωTO||) and ωLO⊥(ωLO|| ) are 411 cm-1 (384 cm-1) and 589.8 cm-1 (572 cm-1), respectively. These results are compared with the reported values measured from the other techniques. Good agreement has been obtained.

Keywords: Dielectric function; polarized infrared reflectance; wurtzite; ZnO

ABSTRAK

Kajian spektrum pantulan inframerah (IR) terkutub untuk ZnO wurtzit pukal dibentangkan. Ciri-ciri spektrum pantulan IR terkutub dan sifat-sifat optik ZnO telah dikaji. Berdasarkan model fungsi dielektrik anisotropi, spektrum pantulan IR eksperimen telah dipadankan dengan spektrum pantulan IR teori. Frekuensi-frekuensi melintang optik (TO) dan membujur optik (LO) yang diperoleh, iaitu ωTO⊥(ωTO||) dan ωLO⊥(ωLO||) ialah 411 cm^-1 (384 cm^-1) dan 589.8 cm^-1 (572 cm^-1), masing-masing. Keputusan ini telah dibandingkan dengan nilai-nilai yang dilaporkan daripada teknik-teknik ukuran yang lain. Persetujuan yang baik telah diperoleh.

Kata kunci: Fungsi dielektrik; pantulan inframerah terkutub; wurtzit; ZnO

RUJUKAN

Ashkenov, N., Mbenkum, B.N., Bundesmann, C., Riede, V., Lorenz, M., Spemann, D., Kaidashev, E.M., Kasic, A., Schubert, M., Grundmann, M., Wagner, G., Neumann, H., Darakchieva, V., Arwin, H. & Monemar, B. 2003. Infrared dielectric functions and phonon modes of high-quality ZnO films. J. Appl. Phys. 93: 126-133.

Dumelow, T., Barker, T.J., Smith, S.R.P. & Tilley, D.R. 1993. Far-infrared spectroscopy of phonons and plasmons in semiconductor superlattices. Surf. Sci. Rep. 17: 151-212.

Engelbrecht, F. & Helbig, R. 1993. Effect of crystal anisotropy on the infrared reflectivity of 6H-SiC. Phys. Rev. B 48: 15698-15707.

Gervais, F. & Piriou, B. 1974. Anharmonicity in several-polar-mode crystals: adjusting phonon self-energy of LO and TO modes in Al₂O₃ and TiO₂ to fit infrared reflectivity. J. Phys. C: Solid State Phys. 7: 2374-2486.

Kasic, A., Schubert, M., Einfeldt, S., Hommel, D. & Tiward. T.E. 2000. Free-carrier and phonon properties of n- and p-type hexagonal GaN films measured by infrared ellipsometry. Phys. Rev. B 62: 7365-7376.

Kim, J.D., Yun, J.H., Kim, C.H., Park, Y.C., Woo, J.Y., ParK, J.H., Lee, J.H., Yi, J.S. & Han, C.S. 2010. ZnO nanowire-embedded Schottky diode for effective UV detection by the barrier reduction effect. Nanotechnology 21: 115-205.

Klingshirn, C. 2007. ZnO: From basics towards applications. Phys. Stat. Sol. B 244: 3027-3073.

Lockwood, D.J., Yu, G. & Rowell, N. L. 2005. Optical phonon frequencies and damping in AlAs, GaP, GaAs, InP, InAs and InSb studied by oblique incidence infrared spectroscopy. Solid State Communications 136: 404-409.

Ozgur, U., Alivov, Y.I., Liu, C., Teke, A., Reshchikov, M.A., Dogan, S., Avrutin, V., Cho, S.J. & Markoc, H. 2005. A comprehensive review of ZnO materials and devices. J. Appl. Phys. 98: 041-301.

Venger, E.F., Melnichuk, A.V., Melnichuk, L.Y. & Pasechnik, Y.A. 1995. Anisotropy of the ZnO single crystal reflectivity in the region of residual rays. Phys. Stat. Sol. (b) 188: 823-831.

Wang, Z.L. 2007. Novel nanostructures of ZnO for nanoscale photonics, optoelectronics, piezoelectricity, and sensing. Appl. Phys. A 88: 7-15.

*Pengarang untuk surat-menyurat; email: saicheonglee86@yahoo.com