Tellurium-modified silicon nanowires with a large negative temperature coefficient of resistance Appl. Phys. Lett. 101, 133111 (2012) Tapered and aperiodic silicon nanostructures with very low reflectance for solar hydrogen evolution Appl. Phys. Lett. 101, 133906 (2012) Minimizing scattering from antireflective surfaces replicated from low-aspect-ratio black silicon Appl. Phys. Lett. 101, 131902 (2012) Robust hydrophobic Fe-based amorphous coating by thermal spraying Appl. Phys. Lett. 101, 121603 (2012) Influence of high temperature on solid state nuclear track detector parameters Rev. Sci. Instrum. 83, 093502 (2012) Additional information on Appl. Phys. Lett.

A parametric study of the etch characteristics of Ga-based (GaAs, GaSb, and AlGaAs) and In-based (InGaP, InP, InAs, and InGaAsP) compound semiconductors in BCl 3 /Ar planar inductively coupled plasmas (ICPs) was performed. The Ga-based materials etched at significantly higher rates, as expected from the higher volatilities of the As, Ga, and Al trichloride, etch products relative to InCl 3 . The ratio of BCl 3 to Ar proved critical in determining the anisotropy of the etching for GaAs and AlGaAs, through its effect on sidewall passivation. The etched features in In-based materials tended to have sloped sidewalls and much rougher surfaces than for GaAs and AlGaAs. The etched surfaces of both AlGaAs and GaAs have comparable root-mean-square (RMS) roughness and similar stoichiometry to their unetched control samples, while the surfaces of In-based materials are degraded by the etching. The practical effect of the Ar addition is found to be the ability to operate the ICP source over a broader range of pressures and to still maintain acceptable etch rates.

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We investigated dry etching of GaAs in a planar inductively coupled plasma ͑ICP͒ reactor with BCl 3 gas chemistry. The process parameters included planar ICP source power, chamber pressure, reactive ion etching ͑RIE͒ chuck power, and gas flow rate. The ICP source power was varied from 0 to 500 W. Chamber pressure was changed from 5 to 20 mTorr. RIE chuck power was controlled from 0 to 150 W. The gas flow rate was varied from 10 to 40 sccm. We found that a process condition at 20 sccm BCl 3 , 300 W ICP, 100 W RIE, and 7.5 mTorr chamber pressure gave an excellent etch result. The etched GaAs feature showed extremely smooth surface (rms roughness Ͻ 1 nm), vertical sidewall, relatively fast etch rate ͑Ͼ3000 Å/min͒ and good selectivity to a photoresist ͑Ͼ3:1͒. X-ray photoelectron spectroscopy study on the surface of processed GaAs proved a very clean surface of the material after dry etching. We also noticed that our planar ICP source was successfully ignited both with and without RIE chuck power, which was generally not the case with a typical cylindrical ICP source, where assistance of RIE chuck power was required for turning on a plasma and maintaining it. These results indicate that the planar ICP source could be a very versatile tool for advanced dry etching of damage-sensitive compound semiconductors.

PACS. 32.80Pj -Optical cooling of atoms; trapping. PACS. 32.80−t -Photon interactions with atoms.Abstract. -Ultracold cesium atoms are stored in a novel dipole-force trap, which provides long storage times of spin polarization and facilitates easy Stern-Gerlach selection. The trap consists of a far red-detuned standing light wave, oriented vertically in the field of gravity. By comparing the trapping of a single magnetic substate (F =4, mF =0) with the simultaneous storage of all sublevels, we measure the decay of spin polarization that results from photon scattering of trap light. We furthermore observe spin precession in an optically induced "fictitious magnetic field".c EDP Sciences