| 1. |
- Astrath, N. G. C., et al.
(författare)
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Thermal lens and photoacoustic spectroscopy to determine the thermo-optical properties of semiconductors
- 2005
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Ingår i: Journal de Physique IV. - : EDP Sciences. - 1155-4339 .- 1764-7177. ; 125, s. 181-183
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Tidskriftsartikel (refereegranskat)abstract
- In this work we used photoacoustic and thermal lens spectroscopy to study four different semiconductor samples: PbI2, 4HSiC, NiCrO and NiO. The results showed that the combination of these two techniques provided the values of the band gap energies and the thermal diffusivities.
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| 2. |
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| 3. |
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| 4. |
- Belonoshko, Anatoly B., et al.
(författare)
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High-pressure melting of MgSiO3
- 2005
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Ingår i: Physical Review Letters. - 0031-9007 .- 1079-7114. ; 94:19
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Tidskriftsartikel (refereegranskat)abstract
- The melting curve of MgSiO3 perovskite has been determined by means of ab initio molecular dynamics complemented by effective pair potentials, and a new phenomenological model of melting. Using first principles ground state calculations, we find that the MgSiO3 perovskite phase transforms into post perovskite at pressures above 100 GPa, in agreement with recent theoretical and experimental studies. We find that the melting curve of MgSiO3, being very steep at pressures below 60 GPa, rapidly flattens on increasing pressure. The experimental controversy on the melting of the MgSiO3 perovskite at high pressures is resolved, confirming the data by Zerr and Boehler.
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| 5. |
- Da Silva, A. F., et al.
(författare)
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Electronic and optical properties of TiO2
- 2005
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Konferensbidrag (refereegranskat)abstract
- The electronic and optical properties of the rutile titanium dioxide compound have been investigated experimentally by absorption measurements and theoretically by a full-potential linearized augmented plane wave (FPLAPW) method within the local density approximation (LDA). The thin films for the absorption measurements were prepared by DC magnetron sputtering. The theoretical results for the absorption compared qualitatively well with the experimental findings. The dielectric functions and band-structure have also been calculated, and the LDA band-gap energy is corrected by an on-site Coulomb potential.
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| 6. |
- da Silva, A. F., et al.
(författare)
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Electronic and optical properties of wurztzie and zinc-blende TlN and AlN
- 2005
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Ingår i: Journal of Crystal Growth. - : Elsevier BV. - 0022-0248 .- 1873-5002. ; 281:1, s. 151-160
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Tidskriftsartikel (refereegranskat)abstract
- We present calculations of the band structure, density of states and the real and imaginary parts of the dielectric functions in intrinsic TIN and AlN, both for wurtzite and the zinc-blende polytypes. They are based on the local density approximation (LDA) within the density functional theory (DFT), employing the first-principles, full-potential linearized augmented plane wave (FPLAPW) method. We correct the band gap of the AlN by using a quasi-particle method proposed by Bechstedt and Del Sole. The calculated energy gaps, lattice constants and dielectric constants for AlN are in good agreement with available experimental values while for TIN there is no experimental investigation.
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| 7. |
- Da Silva, A. F., et al.
(författare)
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Linear optical response of Si1-xGex compounds
- 2005
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Ingår i: Quantum Sensing and Nanophotonic Devices II. - : SPIE - International Society for Optical Engineering. - 081945706X ; 5732:1, s. 556-564
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Konferensbidrag (refereegranskat)abstract
- Si1-xGex is a good candidate as a substitute material for Si in a low-power and high-speed semiconductor device technologies. Optical devices, such as heterojunction bipolar transistors, are already in industrial production. The samples are grown on Si(001) with both n-and p-type impurities and with different Ge concentrations. The linear optical response of Si 1-x Gex is investigated theoretically using a full-potential linearized augmented plane wave method with respect to composition x. The calculated real and imaginary parts of the dielectric function ε e(ω) = ε1(ω) + iε 2(ω) were found to be in good agreement with recent spectroscopic ellipsometry measurements performed by Bahng et al., J. Phys.: Condens. Matter 13, 777 (2001). We also perform absorption measurements for different type of samples showing the variation of energy gaps as a function of Ge concentrations.
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| 8. |
- Dantas, N. S., et al.
(författare)
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Novel semiconducting materials for optoelectronic applications : Al1-xTlxN alloys
- 2008
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Ingår i: Applied Physics Letters. - : AIP Publishing. - 0003-6951 .- 1077-3118. ; 92:12
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Tidskriftsartikel (refereegranskat)abstract
- We proprose the ternary semiconducting Al1-xTlxN alloys as new material for optoelectronic applications. Ab initio calculations have been performed to study structural, electronic, and optical properties of the theoretically designed thallium-aluminum based nitride alloys. We found that the lattice constants vary linearly with thallium composition whereas the band gap and absorption edge span from ultraviolet to infrared energy region by increasing thallium content which make the predicted material interesting for infrared optical devices among other technological applications.
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| 9. |
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| 10. |
- Dubrovinskaia, N., et al.
(författare)
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Beating the miscibility barrier between iron group elements and magnesium by high-pressure alloying
- 2005
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Ingår i: Physical Review Letters. - : American Physical Society. - 0031-9007 .- 1079-7114. ; 95:24
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Tidskriftsartikel (refereegranskat)abstract
- Iron and magnesium are almost immiscible at ambient pressure. The low solubility of Mg in Fe is due to a very large size mismatch between the alloy components. However, the compressibility of Mg is much higher than that of Fe, and therefore the difference in atomic sizes between elements decreases dramatically with pressure. Based on the predictions of ab initio calculations, we demonstrate in a series of experiments in a multianvil apparatus and in electrically and laser-heated diamond anvil cells that high pressure promotes solubility of magnesium in iron. At the megabar pressure range, more than 10 at. % of Mg can dissolve in Fe and then the alloy can be quenched to ambient conditions. A generality of the concept of high-pressure alloying between immiscible elements is demonstrated by its application to two other Fe group elements, Co and Ni.
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