Optical properties of confined polaronic excitons in spherical ionic quantum dots

Senger, R. T.; Bajaj, K. K.

doi:10.1103/physrevb.68.045313

Cited by 145 publications

(45 citation statements)

References 47 publications

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“…Figure 7 shows the EDS spectra taken from the two regions ͑the polycrystalline film on the sample surface and a group of nanoparticles inside the ma-trix͒ of the annealed ZnO-SiO 2 sample. This was expected considering that the bulk ZnO excitonic Bohr radius is about 2.3 nm, 30 i.e., much smaller than the average ZnO nanocluster size found by GIXRD and TEM in the present work. Figure 8 compares the optical absorption spectra ͑solid line͒ and the RT photoluminescence ͑solid+ symbol line͒ of the fully oxidized ZnO-SiO 2 samples implanted with a fluence of 1.0ϫ 10 17 ions/ cm 2 ͓Fig.…”

Section: -2supporting

confidence: 48%

Size-dependent oxidation in ZnO nanoparticles embedded in ion-implanted silica

Tagliente

Massaro

Mattei

et al. 2008

Journal of Applied Physics

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ZnO-SiO(2) nanocomposites were synthesized by ion implanting a Zn(+) beam in a silica slide and by annealing in oxidizing atmosphere at 800 C. A detailed structural and optical characterization was performed by using glancing incidence x-ray diffraction, transmission electron microscopy combined with selected area electron diffraction and energy dispersive spectrometry, optical absorption, and photoluminescence spectroscopies. Samples obtained with three different Zn+ fluences in the range 1-2 x 10(17) ions/cm(2) have been investigated. According to the results, Zn crystalline nanoparticles were found in the as-implanted Zn-SiO(2) samples. The size of the Zn nanoparticles was proportional to the implantation fluence. The annealing in oxidizing atmosphere promotes the total oxidation of the Zn nanoparticles with a preferential migration of the nanoparticles toward the surface of the sample along with an opposite and less pronounced diffusion toward the bulk of the matrix. A relatively strong excitonic peak from the ZnO nanoparticles was observed both in the optical absorption and photoluminescence spectra. We found that the oxidation of the Zn nanoparticles is size-dependent because the time necessary for the total oxidation of the nanoparticles increases with the decreasing in the size of the nanoparticles. This size-oxidation correlation has been explained in terms of arguments related to the stress of the Zn nanoparticles

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Section: -2supporting

confidence: 48%

Size-dependent oxidation in ZnO nanoparticles embedded in ion-implanted silica

Tagliente

Massaro

Mattei

et al. 2008

Journal of Applied Physics

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“…According to the quantum confinement effect, the bandgap of ZnO NWs becomes larger than that of the bulk counterpart [33]. However, no quantum confinement effects were discovered in this study because the ZnO NWs have radii larger than 50 nm, whereas the bulk ZnO exciton Bohr radius is ~2.34 nm [34].…”

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confidence: 71%

Controllable growth of ZnO nanowires grown on discrete islands of Au catalyst for realization of planar-type micro gas sensors

Nguyen

Quy

Hòa

et al. 2014

Sensors and Actuators B: Chemical

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Controllable growth of ZnO nanowires grown on discrete islands of Au catalyst for realization of planar-type micro gas sensors. Chemical, http://dx.doi. org/10.1016/j.snb.2013.11.043 Access to the published version may require subscription. N.B. When citing this work, cite the original published paper. Sensors and actuators. B, Abstract:The proper engineering design of gas sensors and the controlled synthesis of sensing materials for the high-performance detection of toxic gas are very important in the fabrication of handheld devices. In this study, an effective design for gas sensor chips is developed to control the formation of grown ZnO nanowires (NWs). The design utilizes the dendrite islands of Au catalyst deposited on and between Pt electrodes of a planar-type micro gas sensor so that NWs can grow on instead of a continuous Au seed layer. This method results in an increase of NW-NW junctions on the device and also eliminates current leakage through the seed layer, which results in a higher sensitivity. The results show that the developed gas-sensing devices could be used to monitor NO 2 at moderate temperature (~250 °C) and/or ethanol at a high temperature (~400 °C).

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“…though clearly mentioned by Lopez-Ponceet et al[64] that BER increases for Cd doped ZnO alloy with increasing Cd concentration, indicating the relatively larger BER in CdO than ZnO[65]. Similarly, in case of NiO, however, quantitative information available regarding BER is scarce but quantitatively it is reported that BER of NiO is 0.13 nm which is even further lower than ZnO[66,67].…”

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confidence: 95%

Orbital hybridization-induced band offset phenomena in Ni_xCd_1−xO thin films

et al. 2020

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We present the cationic impurity assisted band offset phenomena in NixCd1-xO (x= 0, 0.02, 0.05, 0.1, 0.2, 0.4, 0.8, 1) thin films and further discussed in the light of orbital hybridization modification. Compositional and structural studies revealed that cationic substitution of Cd 2+ by Ni 2+ ions leads to a monotonic shift in (220) diffraction peak, indicating the suppression of lattice distortion while evolution of local strain with increasing Ni concentration mainly associated to the mismatch in electro-negativity of Cd 2+ and Ni 2+ ion. In fact, Fermi level pinning towards conduction band minima takes place with increasing Ni concentration at the cost of electronically compensated oxygen vacancies, resulting modification in the distribution of carrier concentration which eventually affects the band edge effective mass of conduction band electrons and further endorses band gap renormalization. Besides that, the appearance of longitudinal optical (LO) mode at 477 cm -1 as manifested by Raman spectroscopy also indicate the active involvement of electron-phonon scattering whereas modification in local coordination environment particularly anti-crossing interaction in conjunction with presence of satellite features and shake-up states with Ni doping is confirmed by X-ray absorption near-edge and X-ray photoelectron spectroscopy studies. These results manifest the gradual reduction of orbital hybridization with Ni incorporation, leading to decrement in the band edge effective mass of electron. Finally, molecular dynamics simulation reflects 13% reduction in lattice parameter for NiO thin film as compared to undoped one while projected density of states calculation further supports the experimental observation of reduced orbital hybridization with increasing Ni concentration.Inter university accelerator centre) between the localized d states rather than between band like states like usual semiconductors [20]. So the term "optical gap" instead of "band gap" will be better to be casted off.In the present report, we have synthesized the NixCd1-xO (NDO) thin films for the whole composition range and a detailed study has been carried out on their structural, optical and chemical properties. In particular, we demonstrate the doping induced local strain, electron-electron, electron-ionized impurity interaction and strong electron phonon coupling leads to renormalization of band gap in NDO thin films.The dramatic dependence of the optical gap, moreover, with composition also has a strong correlation with phonon scattering such as optical phonon deformation potential, charged impurity scattering and also phonon stiffening as evidenced by Raman spectroscopy. Moreover, we consider the p-d hybridization between O p and Ni/Cd d orbitals in order to determine the CBM and VBM energy levels, suggesting that p-d hybridization becomes less effective with increasing Ni doping and subsequently affects band gap renormalization by reducing the effective mass of electron at conduction band edge. Complementary Xray absorption near-edge sp...

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Optical properties of confined polaronic excitons in spherical ionic quantum dots

Cited by 145 publications

References 47 publications

Size-dependent oxidation in ZnO nanoparticles embedded in ion-implanted silica

Size-dependent oxidation in ZnO nanoparticles embedded in ion-implanted silica

Controllable growth of ZnO nanowires grown on discrete islands of Au catalyst for realization of planar-type micro gas sensors

Orbital hybridization-induced band offset phenomena in Ni_xCd_1−xO thin films

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Optical properties of confined polaronic excitons in spherical ionic quantum dots

Cited by 145 publications

References 47 publications

Size-dependent oxidation in ZnO nanoparticles embedded in ion-implanted silica

Size-dependent oxidation in ZnO nanoparticles embedded in ion-implanted silica

Controllable growth of ZnO nanowires grown on discrete islands of Au catalyst for realization of planar-type micro gas sensors

Orbital hybridization-induced band offset phenomena in NixCd1−xO thin films

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Orbital hybridization-induced band offset phenomena in Ni_xCd_1−xO thin films