Band-edge absorption spectroscopy of multilayer nanocomposites

Quantum confinement effect in multilayer structure of alternate CdSe and SiOx insulator matrix thinfilms

“…6) observed in the absorption onset of all the ML samples. This might be due to the electron transitions between valence and conduction bands of CdSe nanocrystals and due to the splitting of valence band in CdSe [14,23]. The shift in the absorption onset of ML samples correlate well with thickness of CdSe sublayers, i.e., gradual red shift in this region is observed from 550 to 630 nm in ML samples S1, S2 and S3 as the sublayer thickness of CdSe increases from 5 to 30 nm.…”

“…CdSe/SiO x multilayer thin film shows interesting and peculiar properties in absorption and emission spectra due to its type II band structure alignment [14,15,24]. As the electron mobility in SiO x matrix layers is very low due to large number of defects in them, the carrier (electrons and holes) transport takes place only through CdSe sublayers exclusively [25,26].…”

“…4. Since the excited electrons are probably trapped in the traps of SiO x matrices, size dependent shift in absorption edges of CdSe/SiO x ML thinfilms is caused by hole confinement in CdSe nanocrystals [14]. Absorption spectra of single layer and multilayer samples of CdSe and SiO x materials are shown in Figs.…”

“…CdSe offers the possibility of studying quantum confinement effects in higher cluster size regimes as it is having large Bohr exciton diameter [10][11][12]. Mechanism of nanocluster formation, band edge absorption spectroscopy, photoluminescence and photoreflectance properties of CdSe/SiO x multilayer (d SiOx > d CdSe ) systems have already been studied by various research groups [13][14][15][16]. Preparation of Multilayer (ML) thin films showed that the layers deposited in a step-by-step manner were smoother than those made in one step [17].…”

“…Real space band diagram of CdSe/SiO x multilayers with direct and indirect electronic transitions[14,15].…”