Untitled

Light and thermally induced metastabilities in electrochemically etched nanocrystalline porous silicon

“…Annealing at 150 There are various similarities between porous silicon and amorphous silicon. C. An exposure to ammonia vapor increases dark current of porous silicon [8]. A similar increase in dark current in a-Si:H was observed by Tanielian [16].…”

“…These give rise to metastabilities which persist for a long time even at room temperature. For example, short exposures to light produce a state whose dark current (DC) is higher than annealed state DC (persistent photoconductivity, PPC) and persists for several days at room temperature [6,7,8]. Xu et al and Tischler et al [9,10] have found that PL does not change when light soaking is done in vacuum or nitrogen atmosphere respectively.…”

Arresting photodegradation of porous silicon by a polymer coating

“…Although light emitting devices made from PS have been prepared in research labs [3], no PS based optoelectronic devices have become technically viable, primarily because of the degradation of such devices. PS surfaces are naturally terminated with a covalently bonded monolayer of hydrogen [4], but this monolayer does not give protection against chemical absorption [5] and exposure to light [6,7]. Several groups have studied [8 -13] the degradation of PS with a view towards stabilizing the efficiency of the light emission.…”

Role of surface in light induced degradation of porous silicon

“…Free standing PS samples were prepared by [8,11] electrochemical anodization of boron doped (100) silicon wafers having resistivity ~ 1 Ω-cm in the electrolyte C 2 H 5 OH:HF = 1:1. An Argon Ion laser (488 nm, 4 mW) was used to excite the samples for PL measurements.…”

“…The large surface to volume ratio of PS plays an important role, as the surface provides the competing defect centers for radiative recombination channels. The as prepared PS surfaces are naturally terminated with a covalently bonded monolayer of hydrogen but this monolayer does not give protection against chemical absorption [2,[5][6][7] and exposure to light [8][9][10][11]. Therefore, passivation of surface is necessary to make stable PS based devices.…”