Luminescent nanostructures based on Ge nanoparticles embedded in an oxide matrix

Abstract

Ge nanoparticles embedded in an oxide matrix have been obtained by (a) steam thermal oxidation at 650 • C of polycrystalline SiGe layers and (b) deposition of discontinuous Ge films/SiO 2 multilayers by low pressure chemical vapour deposition at 390 • C and thermal annealing at 700 • C. These two approaches are compared in terms of the composition and size of the nanoparticles and the luminescence properties of the structures. In both cases violet luminescence peaking at 3.1 eV is detected. The origin of this emission in both types of structures is the same and it will be related to defects at the interface between the nanocrystalline Ge and the dielectric matrix. Thinking about future applications, the second approach is found to be much more attractive from the technological point of view, even considering that the first one gives a more intense luminescence emission, since the structure can be fabricated in a single-run process; these structures are currently being investigated to improve their luminescence emission.

Intense Ultraviolet-Blue Photoluminescence from SiO2 Embedded Ge Nanocrystals Prepared by Different Techniques

“…22 However, our results indicate that ∼400 nm emission is not unique to the presence of Ge in the SiO 2 , since it is found in Ge free SiO 2 sample as well. Note that ∼400 nm band is very intense in both SPT1 and Ar1 as compared to a lower intensity peak in SPT2.…”

Effects of temperature and deposition time on the structural and optical properties of Si1−Ge nanoparticles grown by low pressure chemical vapor deposition

“…This fact can be explained from observing the AFM images, where the highest density of nanoparticles was observed for the samples grown for 30 s. Therefore, it is to be expected that the number of Ge atoms present in these samples is higher than that presented by the samples grown for 10 s (which showed the formation of a lower density of nanoparticles), and, consequently, there is a bigger contribution to the Ge\O\Ge vibrational modes, resulting in a more intense absorption peak [21]. Another peak observed in all samples corresponds to the Si\O\Si stretching vibrational mode (TO 2 ) at 1077 cm −1 [26], which significantly decreases in intensity when compared with the peak observed in the SiO 2 spectrum. This may be due to the following: during the FTIR measurement, as a result of the dispersion that experiences the light along its passage through the sample because of the presence of SiGe nanoparticles on SiO 2 , there is a decrease in the amount of light absorbed by the Si\O\Si bonds that the equipment detector is capable of registering, thus leading to a peak of low intensity that appears in the spectrum.…”

“…Peaks at 810 cm −1 corresponding to the Si\O\Si bending vibrational mode (TO 1 ) [26] and at 1260 cm −1 corresponding to the longitudinal optical mode of the high frequency vibration of SiO 2 (LO) [27] are also observed in the SiO 2 spectrum. Fig.…”

Growth Mechanism and Surface Structure of Ge Nanocrystals Prepared by Thermal Annealing of Cosputtered GeSiO Ternary Precursor

“…During the last couple of years germanium nanocrystals (Gencs) have attracted increasing research interest as a promising material for optoelectronics and charge storage applications [1][2][3][4][5]. To this day, two approaches have been predominantly used for the fabrication of Ge-ncs.…”