Effect of Quantum Confinement on Optical Properties of Ge Nanocrystals in GeO[sub 2] Films

Theoretical study of the insulating oxides and nitrides: SiO2, GeO2, Al2O3, Si3N4, and Ge3N4

“…These nanocrystals are embedded in an insulating matrix which is usually chosen to be silica 4,5,6,7 . However, other wide bandgap materials are also employed such as germania 8,9 , silicon nitride 10,11,12 , and alumina 13,14,15 . As a matter of fact, the effect of different host matrices is an active research topic in this field.…”

Enhanced formation of Ge nanocrystals in Ge : SiO2 layers by swift heavy ions

“…The important point here is that the Ge NC peak is red-shifted in comparison with that of the bulk crystalline Ge (300.5 cm −1 ). The estimation of the NCs' diameters was then done using the relation between the crystallite size and the corresponding peak position in the Raman spectra (see, for example, [13][14][15][16]). Using the confinement model, for spherical and fully relaxed NCs, the diameter of the nanocrystallites is estimated to be about 2-5 nm for the 600 • C annealed sample (G-3) and 5-7 nm for the 700 • C annealed sample (G-4).…”

“…In figure 5 we derive the size and the integrated intensities of the NC peaks from the measured spectra of sample Ge-6, as a function of the Ge content. The size of the NCs is estimated, as above, from the redshift of the NC peak in the Raman spectra [13][14][15][16] while the integrated intensities are proportional to the concentration of the NCs. We then note of course that the nearly constant value of the NC concentration for Ge contents higher than 40% in figure 5(b) is a reflection of the constant optical density of the Raman signal, which results from the increase in the Ge content that leads to a decrease in the effective thickness tested by the Raman signal on the one hand, and an increase in the concentration of the Raman excited NCs on the other hand.…”

Anomalous temperature dependence of photoluminescence in GeO x films and GeO x /SiO2 nano-heterostructures

“…Photoluminescence of Si suboxide films is quite well studied [1][2][3][4], but similar Ge subox ide films are poorly studied. Optical properties of Ge suboxide films containing Ge nanocrystals were stud ied experimentally [5][6][7][8]. It is known that defects play important role in photoluminescence of dielectrics.…”

“…The confinement effect shifts the position of Raman peak to low frequencies from bulk Ge Raman peak position (about 301 cm -1 ). The nanocrystal sizes can be esti mated from position of Raman peaks [5]. The Raman spectra of the films and mono crystalline Si substrate are shown in Fig.…”