Enhancement of porous silicon photoluminescence by NF₃/UV photo-thermal surface treatment

Abstract

A NF3/UV photo-chemical surface treatment of porous silicon is presented. The UV photons are provided by an excimer lamp. This treatment strongly enhances the photoluminescence of porous silicon. The increase of PL intensity is about 1-2 orders of magnitude at treatment temperatures in the range of 300-400°C. Using AFM and Auger measurements, it is found that the PL enhancement can be correlated with the growth of about micron thick SiOx layer with the x value close to 2, and incorporation of fluorine. The overall effect of photoluminescence enhancement is suggested to be due to the NF3/UV photothermal etching of the as-formed native oxide, as well as to the cleaning and passivation of the porous silicon surface with fluorine, followed by a rapid growth of a more stoichiometric oxide SiOx(x≈2) layer in air.

Photoinduced fluorescence enhancement and energy transfer effects of quantum dots porous silicon

“…Generally, the larger the blue shift the thicker the oxide. Thermal oxidation produces a quality oxide that both increases and stabilizes the PL from PSi nanostructures [10][11][12]. We observe that PL from native oxide PSi is detectable but photobleaching occurs under continuous laser illumination.…”

“…Passivation of nonradiative surface states is an established strategy to enhance PL from semiconductor nanoparticles [9]. Surface oxidation of PSi has been shown by Posada [10,11] and others [12] to stabilize and significantly enhance PSi PL emission. Results show that encapsulating PSi nanocrystals in a silica gel film produced a 20-fold enhancement effect [10].…”

Enhanced crystallization on porous silicon: Facts and models

“…Indeed, this structure is typical for p-type porous silicon (Fig. 1a), which provided enhanced nucleation and crystallization of proteins [12] and crystalline oxide growth [14,15]. In the extreme case of a vertical deep pore with large diameter (Fig.…”

“…have been grown on the same p-type porous silicon with 5-10 nm pore sizes fabricated by electrochemical etching [12]. Room-temperature crystallization of silicon dioxide in air on NF 3 treated p-type porous silicon [14,15]. No crystallization was observed on flat silicon surface as well as on p þ þ -type porous silicon at the same treatment conditions.…”

NF3 induced photoluminescence enhancement and crystalline oxide growth in porous silicon

“…1c). Evidently, the treatment at higher temperature provides more crystallization centers due to the etching of the PS surface by NF 3 at 400 °C [1]. In contrast, the treatment at 300 °C is expected only to remove native oxide and contaminants from the PS surface.…”