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| 2. |
- Engelbrecht, J. A. A., et al.
(författare)
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Assesment of a model to calculate the refractive index of AlXGa1-XN epilayers using the multi-oscillator model simulation of the infrared reflectance
- 2022
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Ingår i: Physica. B, Condensed matter. - : ELSEVIER. - 0921-4526 .- 1873-2135. ; 625
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Tidskriftsartikel (refereegranskat)abstract
- A formula for the calculation of the refractive index of AlXGa1-XN in the infrared region has previously been proposed. In this paper, the validity of the proposed model is assessed against the multi-oscillator model which simulates the infrared reflectance of AlXGa1-XN epilayers. Acceptable agreement was found between the two models for wavenumbers greater than 3500 cm(-1). Additional validation for the earlier proposed formula is obtained by the calculation of epilayer thicknesses of AlXGa1-XN samples in the infrared region.
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| 3. |
- Engelbrecht, J. A. A., et al.
(författare)
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Comparison of experimental results with theoretical models for the temperature dependence of the band gap of AlxGa1-xN epilayers
- 2022
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Ingår i: Journal of materials science. Materials in electronics. - : SPRINGER. - 0957-4522 .- 1573-482X. ; 33, s. 22492-22498
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Tidskriftsartikel (refereegranskat)abstract
- The band gap energies AlxGa1-xN epilayers prepared on two different substrates were assessed using Fourier Transform Infrared (FTIR) reflectance spectroscopy, photoluminescence (PL) and scanning electron microscopy electron dispersive spectroscopy (SEM-EDS). The results were compared to various theoretical formulae to calculate the band gap, and deviations elucidated.
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| 4. |
- Engelbrecht, J. A. A., et al.
(författare)
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Notes on the plasma resonance peak employed to determine doping in SiC
- 2015
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Ingår i: Infrared physics & technology. - : ELSEVIER SCIENCE BV. - 1350-4495 .- 1879-0275. ; 72, s. 95-100
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Tidskriftsartikel (refereegranskat)abstract
- The doping level of a semiconductor material can be determined using the plasma resonance frequency to obtain the carrier concentration associated with doping. This paper provides an overview of the procedure for the three most common polytypes of SiC. Results for 3C-SiC are presented and discussed. In phosphorus doped samples analysed, it is submitted that the 2nd plasma resonance cannot be detected due to high values of the free carrier damping constant gamma. (C) 2015 Elsevier B.V. All rights reserved.
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| 5. |
- Vaughan, A., et al.
(författare)
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Regolith of the Crater Floor Units, Jezero Crater, Mars : Textures, Composition, and Implications for Provenance
- 2023
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Ingår i: Journal of Geophysical Research - Planets. - : John Wiley and Sons Inc. - 2169-9097 .- 2169-9100. ; 128:3
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Tidskriftsartikel (refereegranskat)abstract
- A multi-instrument study of the regolith of Jezero crater floor units by the Perseverance rover has identified three types of regolith: fine-grained, coarse-grained, and mixed-type. Mastcam-Z, Wide Angle Topographic Sensor for Operations and eNgineering, and SuperCam Remote Micro Imager were used to characterize the regolith texture, particle size, and roundedness where possible. Mastcam-Z multispectral and SuperCam laser-induced breakdown spectroscopy data were used to constrain the composition of the regolith types. Fine-grained regolith is found surrounding bedrock and boulders, comprising bedforms, and accumulating on top of rocks in erosional depressions. Spectral and chemical data show it is compositionally consistent with pyroxene and a ferric-oxide phase. Coarse-grained regolith consists of 1–2 mm well-sorted gray grains that are found concentrated around the base of boulders and bedrock, and armoring bedforms. Its chemistry and spectra indicate it is olivine-bearing, and its spatial distribution and roundedness indicate it has been transported, likely by saltation-induced creep. Coarse grains share similarities with the olivine grains observed in the Séítah formation bedrock, making that unit a possible source for these grains. Mixed-type regolith contains fine- and coarse-grained regolith components and larger rock fragments. The rock fragments are texturally and spectrally similar to bedrock within the Máaz and Séítah formations, indicating origins by erosion from those units, although they could also be a lag deposit from erosion of an overlying unit. The fine- and coarse-grained types are compared to their counterparts at other landing sites to inform global, regional, and local inputs to regolith formation within Jezero crater. The regolith characterization presented here informs the regolith sampling efforts underway by Perseverance. © 2023. The Authors.
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