Photoluminescence Change of As‐Prepared and Aged Porous Silicon with NaOH Treatment

Abstract

Porous silicon (PS) formed electrochemically on crystalline silicon shows visible photoluminescence (PL) at room temperature. 1 It is widely acknowledged that the visible PL can be explained basically in terms of the quantum confinement model. 1,2 However, a number of experimental data inconsistent with this model have also been observed and alternative explanations proposed. Koch et al. 3 proposed the radiation recombination model involving surface-confined states on the nanocrystals. In addition, siloxene derivatives, 4 SiH 2 , 5 or oxide defects 6 on the surface of Si particles are suggested to be the origin of the PL. Many researchers 7-11 demonstrated PL quenching by a variety of chemical modification of the internal surface of PS. Recently, Gole et al. 12 have proposed surface-bounded Si oxyhydride moieties as the source of the PL. The authors 13 reported that the Si-O bond content in PS increases with aging time and correlates to the PL intensity. It is therefore considered that the visible PL may be ascribed to not only the nanosize effect but also to some surface state. Qin and Jia 14 suggested the quantum confinement/ luminescence center model. However, few studies have been reported on the PL properties related to both the chemical states and structures of PS layer. This paper presents an analysis of as-prepared low resistivity p-type PS and PS aged for 15 months, which are chemically etched with aqueous NaOH. Also the correlations among PL properties, chemical states, and microstructures of the PS layer are investigated to clarify the origin of PL.Experimental PS samples were prepared by anodizing boron-doped p-type Si(100) wafers with resistivity of 0.04-0.06 ⍀ cm and size of 13 ϫ 13 ϫ 0.5 mm. The anodization was carried out in a 50% HF-ethanol (1:1) solution at room temperature (297 K) and at a constant current density of 0.35 A/cm 2 for 10 s. An electrical contact was made to the back of the wafer, and only an area of the front surface of 10 mm in diam was exposed to the anodizing solution using a sample holder made of Teflon. The anodized samples were rinsed with deionized water and ethanol, and dried under air blow (as-prepared PS). The resultant PS layer thickness, observed with a scanning electron microscope, was approximately 2.2 m. In addition, PS samples aged in a desiccator at room temperature for 15 months were used (aged PS). The chemical etching treatment of PS samples was carried out by immersion in 0.05% aqueous NaOH at room temperature for 10 to 450 s. The treated samples were rinsed in deionized water, and dried in air after absorbing water on their surfaces with filter paper. The 1 M (ca. 4%) aqueous NaOH treatment of n-and p-type PS layers was reported to have the effect of dissolving the surface oxide completely. 15 The NaOH solution used in this work was much more dilute than the one above.PL spectroscopy was performed at room temperature by using a photoluminescence-lifetime measurement system with a streak scope (Hamamatsu Photonics, C4780). Excitation source was a nitrogen l...

In Situ Silanization Reaction on the Surface of Freshly Prepared Porous Silicon

“…Comparing Figure a with Figure b, we can see that the PL stability is enhanced after in situ modification. This result further demonstrates the role of the bonded silane to the stability of the modified PS …”

“…Stability Test. The freshly prepared PS layer can be dissolved in an aqueous solution of base, which is applied to measure the thickness of the PS layer, and the PL will be quenched after immersion in base solution even for the oxidized PS. , Here, the stability of the modified layers and their PL properties were studied after corroding the samples in an aqueous NaOH solution. Figure shows the FTIR spectra of the modified sample before (curve A) and after (curve B) immersion in 0.1 M NaOH for about 30 min.…”

“…This result further demonstrates the role of the bonded silane to the stability of the modified PS. 35 3.3. A Proposed Mechanism.…”

Vapor-phase silanization of oxidized porous silicon for stabilizing composition and photoluminescence

“…56 Here, the stability of the o-PSi and the silane modified o-PSi and their PL properties were studied after corroding the samples in an aqueous NaOH solution. Figure 7 shows the FTIR spectra of the pristine o-PSi and the silane modified sample before and after immersion in 1 M NaOH for about 3 h. From Fig.…”

Morphological and Structural Properties of Amino-Functionalized Fumed Nanosilica and Its Comparison with Nanoparticles Obtained by Modified Stöber Method

“…The absorption bands at around 1100 cm −1 and 809 cm −1 are attributed to the stretching and bending vibration of the siloxane groups (Si–O–Si), respectively [ 66 , 67 ]. Compared to the unmodified NPs, two new adsorption bands at 3446 cm −1 and 1649 cm −1 are observed on the IR spectrum of the A200A NPs ( Figure 8 b), which are assigned to the stretching vibration of the silanol group (Si–OH) [ 68 , 69 ] and adsorbed water in the sample [ 70 ], respectively. These results confirm the presence of hydroxyl groups on the surface of the NPs.…”