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Past research has shown that indirect excitation of Er3+ ions in SiO2 solid-state matrix with Si nanocrystals can be achieved by different pathways. Here, we investigate the impact excitation mechanisms in detail by means of time-resolved photoluminescence spectroscopy. We explicitly demonstrate that the free carrier impact excitation mechanism is activated as soon as the carriers obtain sufficient excess energy. The “hot” carriers with the above-threshold energy can be created upon optical pumping in two ways: either upon absorption of (i) a single photon with an energy exceeding a certain threshold hν > Eth or (ii) following absorption of multiple photons of lower energy in a single nanocrystal, hν < Eth, followed by an Auger recombination of the generated multiple e-h pairs. In addition, we show that the impact excitation dynamics by hot carriers are similar, regardless of the mode in which they have been created. [ABSTRACT FROM AUTHOR]

Highly crystalline and smooth 1% Ho3+ doped ZnO microspheres with diameters ranging from 0.5 to 15 μm were synthesized using laser ablation technique. Near band edge whispering gallery mode (WGM) resonances from Ho:ZnO microspheres with a single oscillation route in the UV range are observed with 355 nm excitation. Apart from the significantly enhanced visible WGM resonances associated with intrinsic oxygen vacancy defects by Ho3+ doping, the visible range WGM resonances associated with the Ho3+ 5F5 → 5I8 emission at 629–690 nm are also observed with a 488 nm excitation. The WGMs of Ho3+ f-f emission possess lower threshold and high Q-factor values. [ABSTRACT FROM AUTHOR]

We report studies of the excitation mechanism of Eu ions in situ doped during organometallic vapor-phase epitaxy (OMVPE) of GaN. We find that the bright red emission under above-band gap excitation originates primarily from an incorporation site that exhibits high excitation efficiency but occurs in low relative abundance (<3%). The latter represents a device efficiency bottleneck, limiting the emission at high excitation intensities. The majority site, which scales well with the total Eu concentration, exhibits low energy transfer efficiency but dominates the emission under direct excitation in the visible spectral region due to high relative abundance (>97%). [ABSTRACT FROM AUTHOR]

Modifications of direct transition energies by crystal lattice deformations were confirmed in β-FeSi2 epitaxial films on Si(111) substrates. With an increasing of annealing temperature (Ta), lattice constants of a-axis expanded, and those of b- and c-axis shrank, resulting in the volume reduction in -0.2%. In photoreflectance measurements, the direct transition energy at Y point in the Brillouin zone of β-FeSi2 (∼0.92 eV) was shifted to lower photon energy with the increase in Ta. These results revealed that the band-gap energy was modulated systematically by the lattice deformation, which suggests a possibility of band-gap engineering by the lattice deformation in β-FeSi2 epitaxial films on Si(111) substrates. [ABSTRACT FROM AUTHOR]

Secondary ion mass spectrometry analyses were carried out using a metal cluster complex ion of Ir4(CO)7+ as a primary ion beam. Depth resolution was evaluated as a function of primary ion species, energy, and incident angle. The depth resolution obtained using cluster ion bombardment was considerably better than that obtained by oxygen ion bombardment under the same experimental condition due to reduction of atomic mixing in the depth. The authors obtained a depth resolution of ∼1 nm under 5 keV, 45° condition. Depth resolution was degraded by ion-bombardment-induced surface roughness at 5 keV with higher incident angles. [ABSTRACT FROM AUTHOR]

3C-SiC was grown on Si(100) substrates by low-pressure chemical vapor deposition using a C3H8-SiH4-H2 reaction gas system in the pressure range between 1.5 and 100 Torr. The dependences of the crystal structures, growth rates, thickness distributions, and electrical properties of the SiC layers on growth conditions were investigated. At low pressure, it was found that the thickness uniformity was improved, especially at 1.5 Torr compared to atmospheric pressure. The epitaxially grown 3C-SiC layers at 100 Torr have smooth surfaces and high crystalline quality and showed almost the same electrical properties as those of the epilayers by atmospheric pressure chemical vapor deposition. [ABSTRACT FROM AUTHOR]

The In concentration dependence of newly observed Cr-related luminescence lines has been systematically investigated by a low-temperature photoluminescence (PL) method in In,Cr-codoped GaAs. As a result, it has been found that the luminescence center of these In,Cr-related PL lines is a complex of InGa-CrGa-VAs. Furthermore, their relative peak positions with respect to the well-known Cr-VAs PL line have been analyzed by using uniaxial stress data, the result suggesting that local lattice distortion of about 1% is induced by In doping in GaAs. [ABSTRACT FROM AUTHOR]

Presents a corrected reprint of a study on InGaAs/InP multiple quantum wells published in an issue of "Applied Physics Letters".