The effects of boron and arsenic doping in β-FeSi2 have been studied by theoretical simulations and electrical characterization. First-principles calculations revealed that B and As were energetically favorable to occupy the SiII and SiI sites, respectively. The impurity doping was found to induce structural relaxation via lattice distortion, with As doping causing elongation of the AsSi bonds and contraction of the As–Fe bonds while B doping resulting in both inward and outward relaxations of the neighboring Si and Fe host atoms. p-type and n-type conductivities were suggested for the B- and As-doped β-FeSi2, respectively, and confirmed experimentally by Hall effect measurements. B and As were shown to introduce shallow impurity levels in the forbidden gap of β-FeSi2 and therefore could be effective dopants for β-FeSi2. A carrier concentration in a tunable range of 1017 cm−3 and a mobility in the order of 100 cm2/V s were consistently obtained.
Structural, electrical, and optical properties of transparent conductive oxide ZnO:Al films prepared by dc magnetron reactive sputtering Optical and electrical properties of sputter-deposited FeSi 2 thin films on p-Si͑100͒ and SiO 2 / p-Si͑100͒ substrates as well as their evolution with rapid thermal annealing ͑RTA͒ temperature have been investigated. Optical absorption measurements were carried out to determine the absorption spectra of FeSi 2 based on the proposed optical absorption model for the double-layer and triple-layer structures. A direct band gap behavior was concluded for both amorphous and polycrystalline semiconducting FeSi 2 . An absorption coefficient in the order of 10 5 cm −1 at 1 eV and a band gap value of ϳ0.86 eV were obtained for the -FeSi 2 . Hall effect measurements at room temperature indicate heavily doped and n-type conductivity for the FeSi 2 films on p-Si, whose residual carrier concentration was found to be closely correlated with the observed subgap optical absorption via band tailing. The carrier mobility was shown to increase with decreasing residual carrier concentration when the RTA temperature was increased.
The effect of oxidation of 10nm Ni∕Si0.75Ge0.25 and 10nm Ni(10at.%Pt)∕Si0.75Ge0.25 thin films at annealing temperatures ranging from 400to800°C has been studied in detail by Rutherford backscattering spectrometry analysis, cross-sectional transmission electron microscopy, energy dispersive x-ray, and sheet resistance measurements. It is observed that for the films without Pt incorporation, almost two-thirds of the germanosilicide is oxidized. The incorporation of a Pt(10at.%) into Ni not only dramatically reduces the oxidation of the germanosilicides, but also improves the interfacial roughness and morphology. The integral amount of oxygen found in the germanosilicide in the Ni(10at.%Pt)Si0.75Si0.25 films [(1.1±0.17)×1017at.∕cm2] is approximately four times less than that of NiSi0.75Si0.25 [(4.0±0.28)×1017at.∕cm2]. This result is explained in terms of the roles of the higher melting point and bond energy of PtSi in NiSi and NiGe, and much lower free energy of the formation of platinum oxide.
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