Photoluminescence and Raman Scattering in Arrays of Silicon Nanowires

Abstract

Arrays of silicon (Si) nanowires with mean diameters of about 50-100 nm formed by wet-chemical etching of crystalline silicon wafers with low and high doping levels were investigated by means of photoluminescence and Raman spectroscopy. The photoluminescence bands in the spectral ranges of 650-900 nm and about 1100 nm were detected and explained by the radiative recombination of excitons confined in Si nanocrystals on the surface of Si nanowires and by the interband photoluminescence in the volume of Si nanowires, respectively. The intensities of the band-gap related photoluminescence and Raman scattering under excitation at 1064 nm were significantly larger for the Si nanowire samples in comparison with that for the crystalline Si substrates. This fact is explained by strong scattering of the excitation light, which results in partial light trapping in silicon nanowire arrays. The doping level and surface orientation of the substrate were found to influence the photoluminescence and Raman scattering in Si nanowire arrays

Photon lifetime correlated increase of Raman scattering and third-harmonic generation in silicon nanowire arrays

“…This dependence demonstrates the tendency to saturation at a thickness of more than 2 μm. A similar signal increase was obtained in previous works and is explained by the enlargement of the photon path in SiNW arrays caused by multiple scattering [14,16,17]. However, to the present day, an approximately fivefold increase of the Raman signal in comparison to that of the initial c-Si substrate is the largest that has been observed [17].…”

“…MACE allows straight or zigzag SiNWs to be formed [11]. The very interesting features of the formed SiNW arrays are: (i) visible photoluminescence (PL), caused by the occurrence of Si nanocrystals during the etching process at the nanowire walls [12,14]; (ii) extremely low total reflection (up to 1% in the visible range) [15][16][17]; and (iii) highly efficient interband PL and Raman scattering compared with c-Si [14,16,17]. 1 , L A Golovan 1 and P K Kashkarov 1,2 The latter two effects are often connected with the enlargement of the photon path in scattering media such as SiNW arrays [16][17][18][19].…”

Optical properties of silicon nanowire arrays formed by metal-assisted chemical etching: evidences for light localization effect

“…This fact is well understood by taking into account that the SiNW’s diameter, D , at approximately 100 nm and it is far from the quantum confinement regime [22]. The bimolecular mechanism of the interband radiative recombination in SiNWs with similar D has been recently demonstrated in our previous work [11]. …”

“…The enhancement of the Raman scattering in SiNWs can be interpreted as increasing the excitation intensity of SiNWs because of the partial light localization in inhomogeneous optical medium [11]. Such kind of light localization was observed in different porous semiconductors as GaP, TiO 2 , and Si (see for example a review in [20] and references therein); and it is analogous for the Anderson localization for electrons in amorphous semiconductors [23].…”

“…In particular, SiNWs exhibit a strong optical absorption and rather low reflectance in the visible spectral range [4,6] as well as in room temperature photoluminescence (PL) [10,11]. There are several ways to form SiNWs, and the first method is based on vapor–liquid-solid or bottom-up growth catalyzed by noble metal (mostly gold, Au), as firstly proposed by Wagner and Ellis in 1964 [12].…”