Solid State Science and Technology, Vol. 15, No 2 (2007) 16-21

ISSN 0128-7389


Chan Kok Sheng1, W. Mahmood Mat Yunus1, Wan Md. Zin Wan Yunus2,

Zainal Abidin Talib1 and Anuar Kassim2

1Department of Physics, 2Department of Chemistry

Faculty of Science

Universiti Putra Malaysia

43400 UPM Serdang, Malaysia.



The porous silicon layer was prepared on n-type Si wafers using electrochemical-etching method. The current density was varied from 16 mA/cm2 to 40 mA/cm2. The surface morphology measured using SEM confirms the formation of porous layer on the silicon substrate. The photoacoustic (PA) absorption band and optical band gap energy were determined from PA signal intensity spectra measured at three different modulation frequencies (i.e. 15 Hz, 23 Hz and 33 Hz). The absorption band and energy gap of porous silicon gradually shifted towards higher energy region as the increase of current density thus confirming the porosity dependence of band gap on sample porosity.



[1]. Canham, L. T. 1990. Silicon quantum wire array fabrication by electrochemical and chemical dissolution of wafers. Appl. Phys Lett. 57:1046-1048.

[2]. Da Silva, F, A., N. Veissid, C. Y. An, J. Caetano de Souza, A. V. Batista da Silva, P. Cesar Farias and M. T. F. Z Da Cruz. 1995. Optical band gap of the α - mercuric iodide. J. Appl. Phys. 78:5822.

[3]. Hipwell, M. C. and C. L. Tien. 1999. Short time-scale radiative transfer in light emitting porous silicon. Heat and Mass Transf. 42:249-251.

[4]. Loni, A., A. J. Simons, L. T. Canham, H. J. Philips and L. G. Earwaker. 1994. Compositional variations of porous silicon layers prior to and during ion-beam analyses. J. Appl. Phys. 76:2825-2832.

[5]. Marin, E., I. Riech, P. Diaz and H. Vargas. 2001. Influence of carrier recombination on the thermodiffusion, thermoelastic and electronic strain photoacoustic signal generation mechanisms in semiconductor. Analytical Sciences. 17: 284-287.

[6]. Todorovic, D.M., P.M. Nikolic, A. I. Bojicic, J. Elazar, M. Smiljanic, R. Petrovic, D. G. Vasiljevic-Radovic and K. T. Radulovic. 2001. Investigation of ion-modificated silicon by photoacoustic frequency transmission technique. Analytical Sciences. 17:295-298.

[7]. Toyoda, T., T. Hayakawa, K. Abe, T. Shigenari and Q. Shen. 2000a. Photoacoustic and photoluminescence characterization of highly porous, polycrystalline TiO2 electrodes made by chemical synthesis. J. Lumin. 87-89: 1237-1239.

[8]. Toyoda, T., T. Takahashi and Q. Shen. 2000b. Photoacoustic and photoluminescence studies of porous silicon etched by low-concentration hydrofluoric acid. J. Appl. Phys. 88:6444-6450.

[9]. Rosencwaig, A. and G. Gersho. 1976. Theory of the photoacoustic effect with solid. J. Appl. Phys. 47(1): 64-69.

[10]. Rosencwaig, A. 1980. Photoacoustic and Photoacoustic spectroscopy. New York: John Wiley.

[11]. Smith, R. L. and S. D. Collins. 1992. Porous Silicon Formation Mechanisms. J. Appl. Phys. 8:R1-R22.