Abstract
The aim of the presented work is to combine luminescent porous silicon (PSi) with a ferromagnetic metal (Ni) to modify on the one hand the photoluminescence by the presence of metal deposits and on the other hand to influence the optical properties by an external magnetic field. The optical properties are investigated especially with respect to the wavelength-shift of the photoluminescence due to the metal filling. With increasing metal deposits within PSi the photoluminescence peak is blue-shifted and furthermore an increase of the intensity is observed. Photoluminescence spectra of bare PSi show a maximum around 620 nm whereas in the case of Ni filled samples the peak is blue-shifted to around 580 nm for a deposition time of 15 min. Field dependent magnetic measurements performed with an applied field parallel and perpendicular to the surface, respectively, show a magnetic anisotropy which is in agreement with a thin film. This film-like behavior is caused by the interconnected Ni structures due to the branched porous silicon morphology. The coercivity increases with increasing metal deposition from about 150 Oe to about 450 Oe and also the magnetic anisotropy is enhanced with the growth of metal deposits. Within this work the influence of the magnetic metal filling on the optical properties and the magnetic characterization of the nanocomposites are discussed. The presented systems give not only rise to optoelectronics applications but also to magneto optical integrated devices.
Highlights
Porous silicon in the nanoporous regime with pore diameters of 2–5 nm is known to emit light in the visible since 1990 (Canham, 1990) and it is still under intense investigation (Joo et al, 2016)
In the frame of this work the optical characteristics of luminescent PSi compared with Ni filled porous silicon is discussed especially with respect to the position of the photoluminescence peak and its intensity
The PL peak is blue-shifted and the luminescence intensity is increased with increasing metal filling within the pores which is attributed to the coupling of the silicon emitter with the plasmons of the metal structures
Summary
Porous silicon in the nanoporous regime with pore diameters of 2–5 nm is known to emit light in the visible since 1990 (Canham, 1990) and it is still under intense investigation (Joo et al, 2016). The light emission can be classified mainly in three bands, the red-, the blue, and the infrared band (Canham, 1995). The origin of the red emission is explained by quantum confinement (Lehmann and Gösele, 1991), the blue emission occurs in oxidized samples (Kanemitsu et al, 1993) and is attributed either to defects in SiO2 (Ito et al, 1992) or to OH groups adsorbed on structural defects in SiO2 (Tamura et al, 1994). The high surface area of this nanostructured material which depends on the morphology (nanoporous silicon ∼1,000 m2/cm, mesoporous silicon ∼100 m2/cm, macroporous silicon ∼1 m2/cm3) makes it suitable for pore filling using various materials with specific properties
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