Luminescence from plasma deposited silicon films

Abstract

We report the observation of room-temperature and low-temperature visible photoluminescence from nanocrystalline silicon (nc-Si) thin films produced by plasma-enhanced chemical vapor deposition (PECVD) through a gas discharge containing SiH4 diluted in Ar and H2. The nanocrystalline silicon films were characterized using transmission electron microscopy, spectroscopic ellipsometry, infrared and Raman spectroscopy, and were examined for photoluminescence. Luminescent films consisted of dense silicon nanocrystals that grew in a columnar structure with approximately 20%–30% void space dispersed inside the film. Aside from having small crystalline silicon regions, the structure of the nc-Si films is different than that of porous Si, another luminescent Si material generally produced by electrochemical anodization. Yet, the photoluminescence spectra of the thin nc-Si films were found to be similar to those observed from porous silicon. This similarity suggests that the same mechanism responsible for light emission from porous silicon may also be responsible for emission from nc-Si. The photoluminescence spectra are analyzed in terms of a simple quantum confinement model. Although the mechanism of visible luminescence from porous Si is still a point of controversy, our results support the hypothesis that some of the luminescence from porous silicon and nc-Si films is due to quantum confinement of electrons and holes in crystals with dimensions 2–15 nm.

Optical properties of photo-electrochemical etching of anisotropic silicon (110)

“…Apart from that, the Raman spectra for 5 and 10 min etched Si show an extra peak at around 940 cm −1 . This additional peak is induced by transverse-optical (2TO) phonon overtones [15,16]. The intensity of the 2TO phonon mode was lower than that of longitudinal-optical (LO) phonon in 5 and 10 min etched Si.…”

Air Exposure Improvement of Optical Properties of Hydrogenated Nanostructured Silicon Thin Films for Optoelectronic Application

“…1, the Raman peak arising from crystalline phases shifts toward a low frequency side with decreasing deposition temperature. Supposing that the peak shift is due only to the confinement of optical phonons in spherical nanocrystals, we can estimate the crystallite size in diameter, D R , as (Edelberg et al, 1997):…”

“…Fig. 9 shows a relationship between <δ(111)> and <δ (110) Using the values of D R for the individual samples, we can evaluate the lowest excitation energy, E, under a simple confinement theory for electron and hole (Efros et al, 1982;Kayanuma, 1988;Edelberg et al, 1997) as follows:…”

“…The value of E correspond to the band gap of the films .In the later two terms, 3.572e 2 / r D R corresponds to the coulomb term and 0.284E Ry gives the spatial correlation energy. The later two terms are minor corrections, so we neglected them in the calculation used in this work, because the contribution of these two terms to the total energy will be less than 5% (Edelberg et al, 1997). As shown in Fig.…”

<title>Effect of stress on defect transformation in hydrogen-implanted silicon and SOI structures</title>

“…This SOI technology includes the bonding of hydrogen implanted wafer with another substrate at relatively low temperatures (400 -600 0 C) and demands the high temperature (1 100'C) annealing of SOI to improve structural and electrical properties 1,3. Furthermore, silicon layers oversaturated with hydrogen are seemed to be perspective for optical applications 4 . The utilisation of high pressure (HP) at the stage of high temperature (1HT) treatments can affect defect transformation '-7.…”