Photoluminescence and formation mechanism of chemically etched silicon

Shih, S.; Jung, Keun Hwa; Hsieh, T. Y.; Sarathy, J.; Campbell, Joe C.; Kwong, Dim‐Lee

doi:10.1063/1.107162

Cited by 127 publications

(72 citation statements)

References 13 publications

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“…As known HNO 3 is an oxidizing agent for Si and the formation of the (NH 4 ) 2 SiF 6 requires reduction of nitrogen. By referring to the mechanisms proposed in the case of stain-etching [4] we can write:…”

Section: Methodsmentioning

confidence: 99%

Structural and luminescence properties of vapour‐etched porous silicon and related compounds

Aouida

Saadoun

Saad

et al. 2005

phys. stat. sol. (c)

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Porous silicon (PS) is usually prepared by the electrochemical anodization or the stain etching techniques. Recently, a new method consisting of exposing silicon substrates to acid vapours issued from a mixture of HNO 3 /HF was employed to generate highly luminescent PS layers. The so-called HNO 3 /HF vapour etching (VE) technique can be easily applied in various large area of silicon-based devices. Depending on the HNO 3 /HF volume ratio, we found that VE silicon results in the formation of PS and/or a luminescent (NH 4 ) 2 SiF 6 powder-like phase. FTIR spectra of VE-based PS layers formed at HNO 3 /HF volume ratio ranging between 1/100-1/3 contain N-H and Si-F bonds related to NH 4 + and SiF 6 2-ions in addition to the conventional SiH x species. These nitride and fluoride groups were identified to be associated to the (NH 4 ) 2 SiF 6 powder-like phase which in turn contains small Si nanoparticles embedded in a SiO x matrix. The presence of such structures was explained as being the product of the VE technique itself. For vapours rich in HNO 3 (HNO 3 /HF volume ratio > 1/4), the VE method can produce almost only the luminescent (NH 4 ) 2 SiF 6 compound. The VE-based PS is essentially composed of dot-like Si particles with sizes not exceeding 5 nm and emitting a photoluminescence (PL) band around 1.93 eV. The PL band of the VE-based PS presents a shoulder at 2.09 eV, which becomes more significant after oxidation in air. This shoulder at 2.09 eV was attributed to an excitonic emission from the energy levels of the SiO x surrounding the smallest Si nanocrystallites. The PL band emission of the (NH 4 ) 2 SiF 6 powder presents two peaks. The first one was attributed to Si nanocrystallites emitting at 1.98 eV. The second peak could be associated to the smallest nanocrystallites (≤ 1.5 nm). For these crystallites, excitons are trapped on the SiO x energy levels, leading to a maximum PL band emission around 2.1 eV. This PL band seems to have the same origin than the small shoulder observed in the PL emission of PS.

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Section: Methodsmentioning

confidence: 99%

Structural and luminescence properties of vapour‐etched porous silicon and related compounds

Aouida

Saadoun

Saad

et al. 2005

phys. stat. sol. (c)

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“…3͑a͒ and 3͑c͔͒ exhibit a broad emission peaking at ϳ2.0− 2.1 eV, which is typically observed in stain etched PSi samples in HF/ HNO 3 -based solutions. 3,[9][10][11][12][13][14] The stain etched sample in the 47 wt % solution ͓Fig. 3͑d͔͒ also exhibits a broad peak at ϳ2 eV.…”

Section: A Photoluminescencementioning

confidence: 99%

Properties of light-emitting porous silicon photoetched in aqueous HF∕FeCl3 solution

Adachi

2007

Journal of Applied Physics

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The formation of yellow-light-emitting porous silicon ͑PSi͒ layers in a HF solution with adding an oxidizing agent FeCl 3 is presented. The PSi layers are formed by photoetching under Xe lamp illumination. The photoluminescence ͑PL͒ intensity is strongly dependent on the FeCl 3 concentration and shows a maximum at x ϳ 25 wt % ͓50 wt % HF: ͑x wt % FeCl 3 in H 2 O͒ =1:1͔. The surface topography as characterized by atomic force microscopy reveals features on the order of 20Ϫ100 nm with a root-mean-squares roughness of Յ2 nm. The Fourier-transform infrared spectroscopy shows a new absorption peak at ϳ1100 cm −1 , which is assigned to the surface oxide stretching mode and grows larger with increasing etching time. The stain etched samples also show PL emission, but they are synthesized only at higher x concentrations ͑Ն20 wt %͒. The PSi formation mechanism can be explained with the aid of a surface energy-band diagram of n-type silicon in the HF/ FeCl 3 electrolyte.

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“…However, a careful comparison with a micrograph of a conventionally anodized sample revealed that the surface morphologies are similar, suggesting that the stain etching can produce a lightemitting PSi layer on the surface. 4,6 Furthermore, the AFM and TEM of conventionally anodized, laterally anodized, and stain-etched silicon layers showed that these porous layers have a "fractal-type" surface morphology. 23 The schematic energy band configurations in the vicinity of the surface of a n-type silicon before and after photoetching in 1 M NaF solution are shown in Fig.…”

Section: Fig 2 Large-scale Afm Images Ofmentioning

confidence: 99%

Ultraviolet emission from porous silicon photosynthesized in aqueous alkali fluoride solutions

Uchida

Tomioka

Adachi

2006

Journal of Applied Physics

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Stable ultraviolet ͑UV͒ photoluminescence ͑PL͒ has been observed at room temperature in porous silicon ͑PSi͒ fabricated by photoetching in aqueous alkali fluoride solutions. The aqueous solutions used are 1 M NaF and 1 M KF. They give an alkaline reaction caused by partial hydrolysis. The PL peaks at ϳ3.3 eV have a full width at half maximum of ϳ0.1 eV, which is much smaller than those reported previously ͑ജ0.5 eV͒. Spectral analyses suggest that both quantum confinement and surface passivation effects enable the observation of UV emission in NaF-and KF-prepared PSi samples.

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Photoluminescence and formation mechanism of chemically etched silicon

Cited by 127 publications

References 13 publications

Structural and luminescence properties of vapour‐etched porous silicon and related compounds

Structural and luminescence properties of vapour‐etched porous silicon and related compounds

Properties of light-emitting porous silicon photoetched in aqueous HF∕FeCl3 solution

Ultraviolet emission from porous silicon photosynthesized in aqueous alkali fluoride solutions

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