Controllable biaxial and uniaxial nanowrinkles (see figure) are fabricated by a simple two‐step approach — metal deposition and subsequent heating — based on shape memory polymer (prestressed polystyrene) sheets. The wavelengths of the wrinkles can be tuned by controlling the thickness of deposited metal. The ready integration of the nanowrinkles into microchannels and their effectiveness in surface enhanced sensing is demonstrated.

Electrically-induced electron spin polarization is imaged in n-type ZnSe epilayers using Kerr rotation spectroscopy. Despite no evidence for an electrically-induced internal magnetic field, currentinduced in-plane spin polarization is observed with characteristic spin lifetimes that decrease with doping density. The spin Hall effect is also observed, indicated by an electrically-induced out-ofplane spin polarization with opposite sign for spins accumulating on opposite edges of the sample. The spin Hall conductivity is estimated as 3 ± 1.5 Ω −1 m −1 /|e| at 20 K, which is consistent with the extrinsic mechanism. Both the current-induced spin polarization and the spin Hall effect are observed at temperatures from 10 K to 295 K. PACS numbers: 75.25.Pn, 75.25.Dc, 71.70.Ej, 78.47.+p The ability to manipulate carrier spins in semiconductors through the spin-orbit (SO) interaction is one of the primary motivations behind the field of spintronics. SO coupling provides a mechanism for the generation and manipulation of spins solely through electric fields [1,2,3], obviating the need for applied magnetic fields. Much of the recent interest in the consequences of SO coupling in semiconductors surrounds the production of a transverse spin current from an electric current, known as the spin Hall effect. Though predicted three decades ago [4], the first experimental observations of the spin Hall effect have appeared only recently [5,6,7]. Subsequent work into the spin Hall effect has addressed the importance of extrinsic or intrinsic mechanisms of the spin Hall conductivity [7,8,9,10], the nature of spin currents [11,12], and the potential ability both to produce and to detect spin Hall currents using only electric fields [13,14].Previous experiments showing electrical generation of spin polarization in semiconductors through SO coupling have been performed at cryogenic temperatures in GaAs, the archetypical III-V zincblende semiconductor. In contrast, the wide band gap and long spin coherence times of II-VI semiconductors allow many spin-related effects to persist to higher temperatures than typically observed in the GaAs system [15]. Many of the effects of SO coupling on the electrical manipulation of spin polarization have not been studied in detail in these compounds. In ZnSe, the extrinsic SO parameter λ ZnSe = 1.06 eÅ 2 , as calculated from an extended Kane model, is five times less than that in GaAs, with λ GaAs = 5.21 eÅ 2 [10, 16]. Despite weaker SO coupling, large extrinsic SO skewscattering has been observed in the anomalous Hall effect in magnetically doped ZnSe [17]. In this Letter we optically measure electrically-induced spin polarization in ZnSe epilayers that persists to room temperature. We observe in-plane current-induced spin polarization (CISP) in ZnSe with n-doping ranging over two orders of magnitude and out-of-plane electrically-induced spin accumulation at the edges of an etched channel, providing evidence for the extrinsic spin Hall effect. Unlike in previous studies of CISP and the spin Hall eff...

The performance of chemically synthesized lead sulfide ͑PbS͒ quantum dots ͑QDs͒ in planar, nontracking luminescent solar concentrators ͑LSCs͒ is evaluated using spectroscopic and photovoltaic techniques. Spatially resolved measurements are used to investigate and analyze the role of reduced self-absorption on the LSC efficiency. From comparative measurements of samples with Rhodamine B and CdSe/ZnS QDs it is established that PbS LSCs generate nearly twice the photocurrent in silicon cells than the other materials, achieving an integrated optical efficiency of 12.6%. This is attributed primarily to the broadband absorption of PbS which allows optimum harvesting of the solar spectrum.

Time-resolved optical techniques are used to explore electron spin dynamics in bulk and epilayer samples of n-type ZnO as a function of temperature and magnetic field. The bulk sample yields a spin coherence time T * 2 of 20 ns at T = 30 K. Epilayer samples, grown by pulsed laser deposition, show a maximum T * 2 of 2 ns at T = 10 K, with spin precession persisting up to T = 280 K.A lot of attention has been focused on zinc oxide (ZnO) because of material properties that make it well-suited for applications in ultra-violet light emitters, transparent high-power electronics and piezoelectric transducers. In addition, the theoretical work of Dietl et al ., 1 predicting room temperature ferromagnetism for Mn-doped p-type ZnO, has revealed the possibility that ZnO may be an appropriate candidate for spintronics. 2 The magnetic properties of thin films of ZnO with transition ion doping, 3,4,5 are being widely investigated, but practical spintronics applications would also require long spin coherence time and spin coherence length.