Quantum confinement in EuO heterostructures
Quantum wells are created from ultrathin single-crystalline EuO layers to study the evolution of the opticalband gap down to the single nanometer regime. We find that the EuOband gap is indirect —independent ofquantum well thickness —and increases from 1.19 eV for bulk-like (d = 32 nm) to ≈1.4 eV in the ultrathin films (d = 1.1 nm). The observedband-gap widening is a clear sign of a quantum confinement effect, which can be used to control and modify theband gap in EuO-based all-oxideheterostructures. (Source: Applied Physics Letters)
Source: Applied Physics Letters - November 14, 2016 Category: Physics Authors: G ünther M. Prinz, Timm Gerber, Axel Lorke and Martina Müller Source Type: research
Selective growth of fully relaxed GeSn nano-islands by nanoheteroepitaxy on patterned Si(001)
In this letter, we explore in detail the potential ofnanoheteroepitaxy to controllably fabricate high quality GeSn nano-structures and to further improve the crystallinity of GeSn alloys directlygrown on Si(001). The GeSn wasgrown bymolecular beam epitaxy at relatively high temperatures up to 750 °C on pre-patterned Si nano-pillars embedded in a SiO2 matrix. The best compromise between selective GeSngrowth and homogenous Sn incorporation of 1.4% was achieved at agrowth temperature of 600 °C.X-ray diffraction measurements confirmed that ourgrowth approach results in both fully relaxed GeSn nano-islands and negligibl...
Source: Applied Physics Letters - November 14, 2016 Category: Physics Authors: V. Schlykow, W. M. Klesse, G. Niu, N. Taoka, Y. Yamamoto, O. Skibitzki, M. R. Barget, P. Zaumseil, H. von K änel, M. A. Schubert, G. Capellini and T. Schroeder Source Type: research
Off-state current reduction in NbO2-based selector device by using TiO2 tunneling barrier as an oxygen scavenger
We report a significant off-state current reduction by an order of magnitude in the NbO2-based selectordevices by inserting an ultrathin TiO2 ( ∼2 nm)tunneling barrier. Moreover, the ultrathin TiO2 layer improves the reliability and uniformity of voltage-inducedinsulator-to-metal transition (IMT) in the NbO2 selectordevices by thermodynamically suppressing the formation of asurfaceNb2O5 layer. Our study suggests that the suitable combination oftunneling barrier and IMT materials can minimize the “off” current of IMT selectordevices and improve their applicability in high-density three dimensional cross point arraym...
Source: Applied Physics Letters - November 14, 2016 Category: Physics Authors: Minkook Kang and Junwoo Son Source Type: research
Spontaneous cracking of amorphous solid water films and the dependence on microporous structure
Vapor-deposited, porous,amorphous, water-icefilms, also calledamorphous solid water (ASW),crack spontaneously duringgrowth when thefilm thickness exceeds a critical value (Lc). We measured theLc duringgrowth of ASWfilms as a function ofgrowth temperature (Tg = 10 K, 30 K, and 50 K) and deposition angle (θ = 0°, 45°, and 55°) using a quartz crystal microbalance, an optical interferometer, and an infrared spectrometer. The critical thickness, 1–5 μm under our experimental conditions, increases withTg andθ, an indication offilm porosity. We suggest that ASWfilms undergo tensile stress due to the mismat...
Source: Applied Physics Letters - November 14, 2016 Category: Physics Authors: Caixia Bu, Catherine A. Dukes and Ra úl A. Baragiola Source Type: research
Selective growth of epitaxial Sr2IrO4 by controlling plume dimensions in pulsed laser deposition
We report thatepitaxial Sr2IrO4thin-films can be selectivelygrown usingpulsed laser deposition(PLD). Due to the competition between the Ruddlesden-Popper phases of strontium iridates (Srn+1IrnO3n+1), conventionalPLD methods often result in mixed phases of Sr2IrO4 (n = 1), Sr3Ir2O7 (n = 2), and SrIrO3 (n = ∞). We have discovered that reducedPLD plume dimensions and slow deposition rates are the key for stabilizing pure Sr2IrO4 phasethin-films, identified by real-timein-situ monitoring of their optical spectra. The slow film deposition results in athermodynamically stable TiO2\\SrO\IrO2\SrO\SrO configuration...
Source: Applied Physics Letters - November 14, 2016 Category: Physics Authors: S. S. A. Seo, J. Nichols, J. Hwang, J. Terzic, J. H. Gruenewald, M. Souri, J. Thompson, J. G. Connell and G. Cao Source Type: research
Curvature effects in two-dimensional optical devices inspired by transformation optics
Light transport in curved quasi two-dimensionalwaveguides is considered theoretically. Within transformation optics andtensortheory, a concise description of curvature effects on transverse electric and magnetic waves is derived. We show that the curvature can induce light focusing andphotonic crystal properties, which are confirmed byfinite element simulations. Our results indicate that the curvature is an effective parameter for designing quasi two-dimensional optical devices in the fields of micro and nanophotonics. (Source: Applied Physics Letters)
Source: Applied Physics Letters - November 14, 2016 Category: Physics Authors: Shuhao Yuan, Yongyou Zhang, Qingyun Zhang, Bingsuo Zou and Udo Schwingenschlogl Source Type: research
Tradeoffs between oscillator strength and lifetime in terahertz quantum cascade lasers
We present evidence that the failure of high diagonality alone as a design strategy is due to a fundamental trade-off between large opticaloscillator strength and long upper-level lifetime. We hypothesize that diagonality needs to be paired with increaseddoping in order to succeed, and present evidence that highly diagonal designs can benefit from much higherdoping than normally found in terahertzquantum cascade lasers. In assuming the benefits of high diagonality paired with highdoping, we also highlight important challenges that need to be overcome, specifically the increased importance of carrier induced band-bending an...
Source: Applied Physics Letters - November 14, 2016 Category: Physics Authors: Chun Wang I. Chan, Asaf Albo, Qing Hu and John L. Reno Source Type: research
A patch-array antenna single-mode low electrical dissipation continuous wave terahertz quantum cascade laser
We introduce a double metal terahertzquantum cascade laser meant for astrophysical heterodyne measurements. The laser ridge is embedded in benzocyclobutene, and the device exhibits single mode, continuouswave operation around 4.745 THz with a peak power of almost 1.8 mW at 10 K and a power consumption of ≈1.6 W. Moreover, thanks to the integration of a top metal contact with a patch arrayantenna for light out-coupling the beam of the emitted light has a low-divergence single-lobe profile and an FWHM of ≈30°. (Source: Applied Physics Letters)
Source: Applied Physics Letters - November 14, 2016 Category: Physics Authors: L. Bosco, C. Bonzon, K. Ohtani, M. Justen, M. Beck and J. Faist Source Type: research
Strong amplitude-phase coupling in submonolayer quantum dots
Submonolayerquantum dots promise to combine the beneficial features of zero- and two-dimensional carrier confinement. To explore their potential with respect to all-optical signal processing, we investigate the amplitude-phase coupling (α-parameter) insemiconductor optical amplifiers based on InAs/GaAssubmonolayerquantum dots in ultrafastpump-probe experiments. Lateral coupling provides an efficient carrier reservoir and gives rise to a largeα-parameter. Combined with a high modal gain and an ultrafast gain recovery, this makes thesubmonolayerquantum dots an attractive gain medium for nonlinear optical signal processing....
Source: Applied Physics Letters - November 14, 2016 Category: Physics Authors: Bastian Herzog, Benjamin Lingnau, Mirco Kolarczik, Y ücel Kaptan, Dieter Bimberg, André Maaßdorf, Udo W. Pohl, Ricardo Rosales, Jan-Hindrik Schulze, Andre Strittmatter, Markus Weyers, Ulrike Woggon, Kathy Lüdge and Nina Owschimikow Source Type: research
Plasmonic hole arrays for combined photon and electron management
Material architectures that balance optical transparency and electrical conductivity are highly sought after forthin-filmdevice applications. However, these are competingproperties, since the electronic structure that gives rise to conductivity typically also leads to optical opacity. Nanostructuredmetalfilms that exhibit extraordinary optical transmission, while at the same time being electrically continuous, offer considerable flexibility in the design of their transparency and resistivity. Here, we present design guidelines formetalfilms perforated with arrays of nanometer-scale holes, discussing the consequences of the...
Source: Applied Physics Letters - November 14, 2016 Category: Physics Authors: Andreas C. Liapis, Matthew Y. Sfeir and Charles T. Black Source Type: research
Erratum: “Magnetoelectric properties of flexible BiFeO3/Ni tapes” [Appl. Phys. Lett. 101, 012908 (2012)]
(Source: Applied Physics Letters)
Source: Applied Physics Letters - November 14, 2016 Category: Physics Authors: L. Yan, M. Zhuo, Z. Wang, J. Yao, N. Haberkorn, S. Zhang, L. Civale, J. Li, D. Viehland and Q. X. Jia Source Type: research
First-principles investigation on solar radiation shielding performance of rutile VO2 filters for smart windows
Vanadium dioxide (VO2) undergoing reversiblemetal-insulator phase transition could allow for the formation of an efficient thermochromic material for smart windows. However,solar radiation shielding performance is determined by transparent rutile VO2 filters, and the puzzlingmetal-insulator transition mechanism makes it challenging to explain the origin of the coexistence of strongnear infraredabsorption with high optical transparency. Theband structure, the density of states, and theoptical properties of rutile VO2 were calculated using the first-principles calculations. The calculated results of the structural andoptical...
Source: Applied Physics Letters - November 11, 2016 Category: Physics Authors: Lihua Xiao, Yuchang Su, Wei Qiu, Jingyu Ran, Yike Liu, Jianming Wu, Fanghai Lu, Fang Shao and Ping Peng Source Type: research
Aberration-free and functionality-switchable meta-lenses based on tunable metasurfaces
Constructing a meta-lens with tunable meta-atoms with varactor diodes incorporated, we can precisely control the phase profile of the meta-lens by varying the external voltages imparted on the diodes, such that the dispersion-induced phase distortions at off-working frequencies can be rectified and the functionality of the meta-lens can be dynamically changed. As an illustration, we design and fabricate a tunable meta-lens in themicrowave regime and employ both experiments and numerical simulations to demonstrate the aberration-free and dynamically switchable focusing performances of the meta-lens. Our approach paves the r...
Source: Applied Physics Letters - November 11, 2016 Category: Physics Authors: He-Xiu Xu, Shaojie Ma, Weijie Luo, Tong Cai, Shulin Sun, Qiong He and Lei Zhou Source Type: research
Gate dielectric ion implantation to modulate the threshold voltage of In2O3 nanowire field effect transistors
In this report, N+ion implantation of gatedielectric was conducted to modulate the threshold voltage of In2O3nanowireFET. Electrical measurements reveal that the threshold voltage can be reduced to as low as −2.0 V from the initial −23.2 V afterion implantation. This can be attributed to the effects ofimplantation induced electron traps. Moreover, it is found that the stability of threshold voltage can be improved byion implantation. This simple and convenient method indicates that gatedielectricion implantation may be a potential way to realize the low voltage operation and uniform In2O3nanowireFETs. (Source: Applied Physics Letters)
Source: Applied Physics Letters - November 11, 2016 Category: Physics Authors: Yang Yu, Wenqing Li, Pengcheng Wu, Changzhong Jiang and Xiangheng Xiao Source Type: research
Image pixel device using integrated organic electronic components
We report a solution processed, monolithically integrated device similar to animaging pixel element used in complementary metal-oxidesemiconductor (CMOS) based cameras. This integrated pixel essentially consists of a pair of organic photodiode (OPD) and organic field effect transistor(OFET). The signal generated by the light responsive OPD drives theOFET to different output states to quantify the light intensity. The prerequisite of a low operating voltageOFET ( (Source: Applied Physics Letters)
Source: Applied Physics Letters - November 11, 2016 Category: Physics Authors: K. Swathi and K. S. Narayan Source Type: research
