Structural and Optical Characterization of Electrochemically-etched Porous Silicon
Lorenzo P. Lopez Jr.b*, Maria Angela B. Faustinoa, Niel Gabriel E. Saplagioa,
Arvin I. Mabilanganb, Neil Irvin F. Cabellob, Rhona Olivia M. Gonzalesa,
Arnel A. Salvadorb, and Armando S. Somintaca,b
aMaterial Science and Engineering Program – College of Science,
University of the Philippines – Diliman, Quezon City, 1101 Philippines
bCondensed Matter Physics Laboratory, National Institute of Physics,
Diliman, Quezon City, 1101 Philippines
corresponding author:This email address is being protected from spambots. You need JavaScript enabled to view it. or This email address is being protected from spambots. You need JavaScript enabled to view it.
ABSTRACT
This study have investigated the structural and optical properties of porous silicon on silicon substrate and of free-standing porous silicon layers. Porous silicon samples were fabricated through electrochemical etching of boron doped silicon wafer in 12% HF solution. For pore formation, current densities of 1.875 mA/cm2, 5 mA/cm2, and 15 mA/cm2 were applied to vary the porosity of the samples. To lift the porous silicon layer off the silicon substrate, an abrupt increase to 31.25 mA/cm2 was supplied at the end of pore formation. The porosities were calculated using Bruggeman effective medium approximation yielding 37.08 %, 76.12%, and 89.25%. Broadening of Raman and x-ray diffraction peaks was observed with increasing porosity, and is attributed to the increase of strain/stress present in porous silicon. The absorbance was calculated from the reflectance and transmittance of the samples, and was found within the range of the full-width-at-half-maximum of the photoluminescence spectrum. Surface states model was used to explain the mechanism of visible luminescence of the porous silicon samples.
INTRODUCTION
Porous silicon (pSi) is a sponge-like structure in the nanometric scale. It is formed through electrochemical etching of silicon (Si) wafer in hydrofluoric acid (HF) ethanoic solution. Some parameters that affect pSi formation are the electrolyte concentration, etching time, and current density. The porosity is dependent on the concentration and applied anodic current, and effective thickness on the etching time. At a critical current during electrochemical etching, electropolishing of the Si surface occurs where pSi is lifted off from the surface and is referred to as free-standing pSi (FS pSi) (Bisi et al. 2000; Sailor 2012). . . . . [DOWNLOAD FULL TEXT HERE]
REFERENCES
ABRAMOF PG, BELOTO AF, UETA AY, FERREIRA NG. 2006. X-ray investigation of nanostructured stain-etched porous silicon. Journal of Applied Physics 99(2):024304.
BARLA K, HERINO R, BOMCHIL G, PFISTER JC, FREUND A. 1984. Determination of lattice parameter and elastic properties of porous silicon by X-ray diffraction. Journal of Crystal Growth 68(3):727-732.
BISI O, OSSICINI S, PAVESI L. 2000. Porous silicon: a quantum sponge structure for silicon based optoelectronics. Surface Science Reports 38(1):1-126.
BRASS M, LI G, STRYLAND EV. 2009. Handbook of Optics, 3rd ed. New York, USA: McGraw-Hill. 1152p.
CASTRO K, PÉREZ-ALONSO M, RODRIGUEZ-LASO MD, FERNÁNDEZ LA, MADARIAGA JM. 2005. On-line FT-Raman and dispersive Raman spectra database of artists’ materials (e-VISART database). Analytical and Bioanalytical Chemistry 382(2):248-258.
CULLIS AG, CANHAM LT, CALCOTT PDJ. 1997. The structural and luminescence properties of porous silicon. Journal of Applied Physics 82(3):909-965.
DITTRICH TH, KONSTANTINOVA EA, TIMOSHENKO VY. 1995. Influence of molecule adsorption on porous silicon photoluminescence. Thin Solid Films 255(1):238-240.
FAHR S, ULBRICH C, KIRCHARTZ T, RAU U, ROCKSTUHL C, LEDERER F. 2008. Rugate filter for light-trapping in solar cells. Optics Express 16(13): 9332-9343.
HAMMOND C. 2009. The basics of crystallography and diffraction. Oxford, UK: Oxford University Press. 256p.
HARRAZ FA. 2014. Porous silicon chemical sensors and biosensors: A review. Sensors and Actuators B: Chemical 202: 897-912.
KANEMITSU Y. 1995. Light emission from porous silicon and related materials. Physics Reports 263(1): 1-91.
KARACALI T, CAKMAK B, EFEOGLU H. 2003. Aging of porous silicon and the origin of blue shift. Optics express 11(10): 1237-1242.
KOCH F. 1993. Models and mechanisms for the luminescence of porous Si. In: Tischler MA, Collins RT, Thewalt MLW, Abstreiter G. Editors. Proceedings of a Symposium B on the Silicon-based Optoelectronic Materials of the Materials Research Society. 1993 April 8-14; San Francisco, California, USA: Cambridge University Press. p319-329.
KUMAR P, HUBER P. 2007. Effect of etching parameter on pore size and porosity of electrochemically formed nanoporous silicon. Journal of Nanomaterials 2007: 1-4.
LAMMEL G, RENAUD PH. 2000. Free-standing, mobile 3D porous silicon microstructures. Sensors and Actuators A: Physical 85(1):356-360.
MABILANGAN AI, SAPLAGIO NGE, ANGULUAN EP, CABELLO NIF, GONZALES ROM, SOMINTAC AS, SALVADOR AA. 2013. Fabrication and Characterization of Porous Silicon for Photonic Applications. Science Diliman 25(1):15-28.
MARTÍN-PALMA R. PASCUAL L, HERRERO P, MARTÍNEZ-DUART JM. 2005. Monte Carlo determination of crystallite size of porous silicon from x-ray line broadening. Applied Physics Letters 87(21):211906.
MÜNDER H, ANDRZEJAK C, BERGER MG, KLEMRADT U, LÜTH H, HERINO R, LIGEON M. 1992. A detailed Raman study of porous silicon. Thin Solid Films 221(1):27-33.
PAPADIMITRIOU D, BITSAKIS J, LOPEZ-VILLEGAS JM, SAMITIER J, MORANTE JR. 1999. Depth dependence of stress and porosity in porous silicon: a micro-Raman study. Thin Solid Films 349(1): 293-297.
PECKHAM J, ANDREWS TG. 2012. Simple optical method to determine the porosity of porous silicon films. Thin Solid Films 520(7):2526-2531.
PRABAKARAN R, KESAVAMOORTHY R, SINGH A. 2005. Optical and microstructural investigations of porous silicon. Bulletin of Materials Science 28(3):219-225.
SAILOR MJ. 2012. Porous silicon in practice: preparation, characterization and applications. Germany: John Wiley & Sons. 130p.
SCHRODER DK. 2006. Semiconductor material and device characterization. New Jersey, USA: John Wiley & Sons. 608-610p.
SETZU S, ROMESTAIN R, CHAMARD V. 2004. Determination of the refractive index of n+-and p-type porous Si samples. Thin solid films 460(1): 53-57.
STEINER P, LANG W. 1995. Micromachining applications of porous silicon. Thin Solid Films 255(1): 52-58.
VON BEHREN J, TSYBESKOV L, FAUCHET PM. 1995. Preparation and characterization of ultrathin porous silicon films. Applied physics letters 66(13): 1662-1664.
YOSHIZAWA T. 2009. Handbook of Optical Metrology: Principle and Applications. New York, USA: CRC Press. 744p.
