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

Abstract

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.

Porous Silicon Formation by Photoetching

“…2c). It is to be noted that the larger the E o value is in the positive (negative) scale, the stronger is the oxidation (reduction) agent (Adachi and Kubota 2007;Xu and Adachi 2007;Tomioka et al 2007). The absorption of photons results in the generation of electron-hole pairs.…”

“…In (Xu and Adachi 2007), the atomic force microscopy images were reported to show many irregularly shaped hillocks and voids distributed randomly over the entire PS surface. The observed root-mean-squares roughnesses were a few nanometers.…”

Porous Silicon Formation by Stain Etching

“…The etch rate is also directly proportional to the concentration of either Fe 3+ or VO 2 + ; however, unlike HNO 3 , there is no threshold concentration below which stain etching does not occur. The formation of por-Si films in Fe 3+ + HF solutions under illumination with a Xe lamp has also been studied (Xu and Adachi 2007). Kolasinski and Barclay (2013a) have demonstrated that the stoichiometry of stain etching is distinct from that of anodic por-Si formation.…”

Spectroscopic investigation of light-emitting porous silicon photoetched in aqueous HF∕I2 solution

“…Some authors also demonstrated the formation of a luminescent PSi by photoetching in HF-based solutions under HeϪNe laser illumination. [5][6][7][8][9] More recently, we reported the formation of luminescent PSi layers by photoetching in a HF solution containing some oxidizing agents, such as KIO 3 , 10 I 2 , 11 and FeCl 3 , 12 and using an incoherent light source ͑Xe lamp͒. This method enabled to obtain a large ͑Ն20ϫ 20 mm 2 ͒, homogeneous PSi layer in a very short time ͑Ͻ10 min͒.…”

“…This method enabled to obtain a large ͑Ն20ϫ 20 mm 2 ͒, homogeneous PSi layer in a very short time ͑Ͻ10 min͒. [10][11][12] The stain and photoetched PSi films have been suggested as being similar in nature to the anodically etched PSi films. [4][5][6][7][8][9][10][11][12] The purpose of this article is to make clear the optical properties of PSi photoetched in aqueous HF/ I 2 solution.…”