dc.description.abstract | Silicon has been the backbone of the mainstream electronics of the last fifty
years. It is however, used in conjunction with other matierals, mainly with its
oxides and nitrides. Germanium, on the other hand, is also a group IV element and
has been used in the early stages of transistor and detector development. In addition
to Si/Ge heterojunctions, bandgap engineering through SiGe alloys has also been
used in photodetectors. Recent progress in light emitting devices utilizing Si
nanocrystals suggest the use of Ge1-xNx layers as barriers due to its suitable band
offsets [1]. Experiments have shown that Ge1-xNx is also a promising material for
applications in photodiodes, amplifiers, optic fibers, protective coatings, etc [1].
Both Si and Ge are, however indirect bandgap semiconductors, lacking efficient
light emission. On the other hand, strong light emission observed in Si nanocrystals
has made the study of semiconductor nanocrystals an expanding field of interest
due to potential applications in novel optoelectronic devices [2]. These nanocrystals
exhibit strong luminescence and nonlinear optical properties that usually do not
appear in the bulk materials [2]. SiGe nanocrystals attract attention due to the
possibility of a tunable band gap with composition. In this study, formation of Ge1-xNx thin films and SiGe nanocrystals by plasma
enhanced chemical vapor deposition (PECVD) reactor has been studied. We present
the growth conditions and experimental characterization of the resulting thin films
and nanocrystals. We used ellipsometry, Raman Spectrometry, Fourier Infrared
Spectrometry (FTIR) and X-ray photoelectron Spectroscopy (XPS). For SiGe
nanocrystals, 4 peaks in the Raman Spectra were observed around 295 cm-1, 400
cm
-1, 485 cm-1 and 521 cm-1. These peaks are assigned to the Ge-Ge, Si-Ge, local
Si-Si and crystalline Si-Si vibrational modes, respectively [3]. For the Ge1-xNx thin
films FTIR spectrum showed the existence of the Ge-N bonds and its band offsets
determined by XPS confirm its suitability for optoelectronic devices. | en_US |