Spectroscopic ellipsometry of composite thin films with embedded Bi nanocrystals

Abstract

Spectroscopic ellipsometry together with an effective medium model is used to determine simultaneously the effective refractive index, thickness, and metal volume fraction of thin nanocomposite films. The films are formed by Bi nanocrystals embedded in amorphous matrices, either semiconducting ͑Ge͒ or dielectric (Al 2 O 3 ). For the Bi:Ge films ͑metal in an absorbing host͒, the values obtained for both the real and imaginary parts of the refractive index vary continuously from that of Ge to that of Bi. The metal contents determined from the ellipsometry analysis are in excellent agreement with those obtained from direct measurements of the composition. For the Bi:Al 2 O 3 films ͑metal in a nonabsorbing host͒, the extinction coefficient (k) exhibits a maximum around 360 nm which is related to the metal plasmon resonance frequency of Bi nanocrystals. The metal content determined from the ellipsometry analysis in this case is underestimated, probably due to interaction of the Bi crystals with the Al 2 O 3 host.

Peculiarities of Bi0 nanowire arrays growth within the alumina template pores by ac electrolysis

“…Note that the region of this shoulder is close to the absorption peaks reported in Ref. [34]. Furthermore, a vs. hn plots, calculated from the experimental transmittance spectra for various + Bi , demonstrate an obvious blue shift in the absorption threshold (E A ) with decrease in + Bi .…”

“…From theory [30] in case of wires with a diameter less than 100 nm, the confinement of charge carriers leads to considerable changes in the electronic structure and in the red shift of the plasma resonance frequency (o p ), being for Bi 0 at room temperature at about 330 cm À1 [31]. For Bi 0 particles, becoming a semiconductor at room temperature when the size of crystals decreases down to 200 nm [32], this resonance has been observed and reported earlier in several works at 250 [33], 370 [34], $280 [35] and 302 nm [21], depending on the synthesis method applied, particle size and environment. Also, it is known that for Bi 0 nanostructures, due to energy bands splitting into subbands [36] and the related band-edge shifts, the thresholds for various transitions blue shift with the particle size decrease.…”

Quantification of self-sputtering and implantation during pulsed laser deposition of gold

“…3 Using this mean value together with a density of 2.95 g cm −3 for a-Al 2 O 3 , 20 and the SRIM2003 software, 21 the calculated implantation depth h of gold in a-Al 2 O 3 is shown in Fig. 6͑b͒ where it is seen that it approaches saturation for fluences higher than 3 J cm −2 .…”

Ellipsometry and Its Applications in Stoichiometry

“…R. Serna et al investigated the optical properties of Bi:Ge composite thin films using SE [113]. The films, grown on chemically cleaned Si (100) substrates at room temperature and produced by pulse laser deposition (PLD) in vacuum, were formed by Bi nanocrystals embedded in amorphous Ge matrices.…”