Cosmochemical and geochemical studies suggest sulfur (S) as a light alloying element in the iron‐rich cores of telluric planets, but there is no report of sulfur's alloying effect on the electrical and thermal transport properties of iron (Fe); a subject that is closely related to the dynamo action and thermal evolution of planetary cores. We measured the electrical resistivity of hexagonal‐closed‐packed (hcp) structured Fe alloy containing 3 wt. % silicon (Si) and 3 wt. % S up to 110 GPa at 300 K. Combined with the reported resistivities of hcp Fe and hcp Fe‐Si alloy, we determined the impurity resistivity of S in a hcp Fe matrix at high pressures. The obtained impurity resistivity of S is found to be smaller than that of Si. Therefore, S is a weaker influence on the conductivity of Fe alloy, even if S is a major light element in the planetary cores.

Pressure-volume-temperature (P-V-T) experiments on Fe 3 S were conducted to 126 GPa and 2500 K in laser-heated diamond anvil cells (DAC) with in-situ X-ray diffraction (XRD). Seventy nine high-T data as well as four 300-K data were collected, based on which new thermal equations of state (EoS) for Fe 3 S were established. The room-T data together with existing data were fitted to the third order Birch-Murnaghan EoS, which yielded, K 0 = 126 ± 2 GPa and K' = 5.1 ± 1 with V 0 fixed at 377.0 Å 3 . A constant αK T term in the thermal pressure equation, Pth = αK T (T-300K), fitted the high-T data well to the highest temperature, which implies that the contributions from the anharmonic and electronic terms should be minor in the thermal pressure term. The high-T data were also fitted to the Mie-Grüneisen-Debye model; γ 0 = 1.01 ± 0.03 with θ 0 and q fixed at 417 K and 1 respectively. Calculations from the EoS show that crystalline Fe 3 S at 4000-5500 K is denser than the Earth's outer core and less dense than the inner core. Assuming a density reduction due to melting, liquid Fe 3 S would meet the outer core density profile, which however suggests that no less than 16 wt%S is needed to reconcile the observed outer core density deficit. The S-rich B2 phase, which was suggested to be a potential liquidus phase of an Fe 3 S-outer core above 250 GPa, namely the main constituent of its solid inner core, would likely be less dense than the Earth's inner core. As such, while the outer core density requires as much sulphur as 16 wt%, the resulting liquidus phase cannot meet the density of the inner core. Any sulphur-rich composition should therefore be rejected for the Earth's core.

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Growth conditions of metalorganic chemical vapor deposition have been investigated for the purpose of obtaining abrupt InGaP/GaAs interfaces. Photoluminescence (PL) spectra of InGaP/GaAs quantum wells (QWs) are used to characterize these interfaces. The conventional gas switching sequence, i.e., simultaneously switching on group-III and -V gases, is found to provide only a broad peak at wavelengths longer than those of near-band-edge emissions from GaAs in the PL spectrum of the InGaP/GaAs QW. PL studies using QWs having an AlGaAs barrier, for example, AlGaAs/GaAs/InGaP and InGaP/GaAs/AlGaAs, show that the GaAs-on-InGaP interface is responsible for this broad peak. A novel gas switching sequence where group-III gas is switched on first results in sharp peaks corresponding to 5.7- and 2.8-nm-thick wells in the PL spectrum of InGaP/GaAs QW. Preflow of TMGa on InGaP surface is effective in suppressing the substitution of P atoms in InGaP to As atoms at the GaAs-on-InGaP interface.

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