Study of electrodeposition lead telluride films on poroussilicon / Estudo de filmes de telureto de chumbo eletrodepositados sobre silício poroso

AUTOR(ES)
DATA DE PUBLICAÇÃO

2005

RESUMO

This work investigates by the first time PbTe films growth on porous silicon substrate by electrodeposition technique. It was studied porous silicon layer obtained from stain etching by using a HF:HNO3 mixtures at different etching times between 1 and 10 min. Surface morphology analyzed by scanning electron microscopy (SEM) has evidenced Si nanocrystallites and columnar porous, which are characteristics of the etched p+ (100) silicon wafers. The samples presented a non uniform porous distribution and two crystallites average size may be associated. In deed, SEM images reveal a surface fractal structure that increases its non homogeneity as the etching time increases. The crystallite average size increases, but two maximum peaks are well defined in this etching range correlated to an oscillatory behavior of such morphology. The photoluminescence (PL) response, measured from Raman scattering spectroscopy, shows a PL intensity increases as a function of the etching time up to a maximum at 7 min. For etching times of 8, 9 and 10 min this behavior is reversed. This effect can be explained due to the possible porous layer damage that can peel off on the surface for strong etching. In this case, the etching process is in progress again by forming a second porous layer. The process reproducibly was also studied for different samples sets, produced in similar experimental procedure, from MEV and PL measurements. The relative intensity Irel (PL/Si peak) for different samples sets have shown the same physical characteristics, resulting from similar structures, where the same maximum and minimum points are observed as a function of the etching time. PbTe films were electrodeposited from aqueous alkaline solutions of Pb(CH3COO)2, disodium salt of ethylendiaminetetraacetic acid (EDTA) and TeO2 by galvanostatic method with current density in the range of 0.14 up to 0.20 mA/cm2, or by potentiostatic growth process in the potencial range between -1.0 and -0.8 V x Ag/AgCl. It was obtained nanostructured thin films with polycrystalline morphology, average grain size of 100 nm and thickness between 100 up to 400 nm, observed from topographic and cross section SEM images, respectively. The x-ray spectra confirm the polycrystalline structure for films grown on monocristalline Si and porous silicon substrates, formed in the etching time between 1 and 5 min. PbTe peaks of (200), (220), (222) e (400) are presented besides the Pb peak. This peak is attributed to the high negative potential for electrodepositing PbTe is also favorable for Pb deposition. Thus, the deposition potential control influences the film stoichiometry, which is not affected by small variations of the film precursors.

ASSUNTO(S)

semicondutores electrochemical cells silício poroso fotoluminescência semiconductors porous silicon estrutura nanocristalina célula eletroquímica photoluminescence electroless deposition deposição eletrolítica nanocrystalline structure

ACESSO AO ARTIGO

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