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Christopher F Ahles, Jong Youn Choi, Steven F Wolf, Andrew C Kummel
The selective etching characteristics of silicon, germanium and Si0.5Ge0.5 subjected to a downstream H2/CF4/Ar plasma have been studied using a pair of in-situ quartz crystal microbalances (QCMs) and x-ray photoelectron spectroscopy (XPS). At 50 °C and 760 mTorr, Si may be etched in preference to Ge and Si0.5Ge0.5 with an essentially infinite Si:Ge etch rate ratio (ERR), while for Si:Si0.5Ge0.5, the ERR is also infinite at 22 °C and 760 mTorr. XPS data shows the selectivity is due to differential suppression of etching by a ~2 ML thick CxHyFz layer formed by the H2/CF4/Ar plasma on Si and Ge or Si0...
May 24, 2017: ACS Applied Materials & Interfaces
Thibault Alphazan, Adrian Diaz Alvarez, Francois Martin, Helen Grampeix, Virginie Enyedi, Eugenie Martinez, Névine Rochat, Marc Veillerot, Marc Dewitte, Jean-Philippe Nys, Maxime Berthe, Didier Stiévenard, Chloé Thieuleux, Bruno Grandidier
Functionalization of Ge surfaces with the aim of incorporating specific dopant atoms to form high quality junctions is of particular importance for the future generation of solid state devices. We report the shallow doping of Ge wafers with a monolayer doping strategy that is based on the controlled grafting of Sb-precursors and the subsequent diffusion of Sb into the wafer upon annealing. We highlight the key role of citric acid to passivate the surface prior to its reaction with the Sb-precursors and the benefit of a protective SiO2 overlayer that enables the efficient incorporation of Sb dopants with a concentration higher than 1020 cm-3...
May 23, 2017: ACS Applied Materials & Interfaces
Guk-Tae Kim, Tadhg Kennedy, Michael Brandon, Hugh Geaney, Kevin M Ryan, Stefano Passerini, Giovanni Battista Appetecchi
The electrochemical behavior of binder-free, germanium and silicon nanowires as high capacity anode materials for lithium-ion battery systems are investigated in an ionic liquid electrolyte. Cyclic voltammetry, cycling tests and impedance spectroscopy reveal a highly reversible lithium alloying / de-alloying process, as well as promising compatibility between the Ge and Si materials and the electrolyte components. Reversible capacities of 1,400 and 2,200 mA h g-1 are delivered by the Ge and Si anodes, respectively, matching the values exhibited in conventional organic solutions...
May 22, 2017: ACS Nano
Adrian Gómez Herrero, Lamia Hammoudi, Mohammed Kars, Thierry Roisnel, L Carlos Otero-Diáz
Single crystals of anti-mony-doped germanium, Ge1-x Sb x+0.01 (x ≃ 0.0625), were grown by chemical transport reaction. The alloy crystallizes as a superstructure of diamond-type α-Ge. All atoms in the asymmetric unit lie on special positions and are characterized by strong covalent bonds. The anti-mony atoms substitute for one germanium atom at full occupancy at Wyckoff position 4a (site symmetry -43m), and are also at an adjacent tetra-hedral inter-stitial site with partially occupation (16%) at position 4c (or 4d) (site symmetry -43m)...
May 1, 2017: Acta Crystallographica. Section E, Crystallographic Communications
Fang Niu, Rainer Schulz, Arcesio Castañeda Medina, Rochus Schmid, Andreas Erbe
The electrode potential dependence of the hydration layer on an n-Ge(100) surface was studied by a combination of in situ and operando electrochemical attenuated total reflection infrared (ATR-IR) spectroscopy and real space density functional theory (DFT) calculations. Constant-potential DFT calculations were coupled to a modified generalised Poisson-Boltzmann ion distribution model and applied within an ab initio molecular dynamics (AIMD) scheme. As a result, potential-dependent vibrational spectra of surface species and surface water were obtained, both experimentally and by simulations...
May 17, 2017: Physical Chemistry Chemical Physics: PCCP
Xiaobo Chen, Song Li, Lili Hu, Kezhi Wang, Guoying Zhao, Lizhu He, Jinying Liu, Chunlei Yu, Jingfu Tao, Wei Lin, Guojian Yang, Gregory J Salamo
The multiphoton near-infrared, quantum cutting luminescence in Er(3+)/Tm(3+) co-doped telluride glass was studied. We found that the near-infrared 1800-nm luminescence intensity of (A) Er(3+)(8%)Tm(3+)(0.5%):telluride glass was approximately 4.4 to 19.5 times larger than that of (B) Tm(3+)(0.5%):telluride glass, and approximately 5.0 times larger than that of (C) Er(3+)(0.5%):telluride glass. Additionally, the infrared excitation spectra of the 1800 nm luminescence, as well as the visible excitation spectra of the 522 nm and 652 nm luminescence, of (A) Er(3+)(8%)Tm(3+)(0...
May 16, 2017: Scientific Reports
Martin Glavinović, Michael Krause, Linju Yang, John A McLeod, Lijia Liu, Kim M Baines, Tomislav Friščić, Jean-Philip Lumb
Replacing molecular chlorine and hydrochloric acid with less energy- and risk-intensive reagents would markedly improve the environmental impact of metal manufacturing at a time when demand for metals is rapidly increasing. We describe a recyclable quinone/catechol redox platform that provides an innovative replacement for elemental chlorine and hydrochloric acid in the conversion of either germanium metal or germanium dioxide to a germanium tetrachloride substitute. Germanium is classified as a "critical" element based on its high dispersion in the environment, growing demand, and lack of suitable substitutes...
May 2017: Science Advances
Xiaolong Zhu, Wei Yan, Uriel Levy, N Asger Mortensen, Anders Kristensen
Man-made structural colors, which originate from resonant interactions between visible light and manufactured nanostructures, are emerging as a solution for ink-free color printing. We show that non-iridescent structural colors can be conveniently produced by nanostructures made from high-index dielectric materials. Compared to plasmonic analogs, color surfaces with high-index dielectrics, such as germanium (Ge), have a lower reflectance, yielding a superior color contrast. Taking advantage of band-to-band absorption in Ge, we laser-postprocess Ge color metasurfaces with morphology-dependent resonances...
May 2017: Science Advances
Simin Janitabar-Darzi, Reza Rezaei, Kamal Yavari
Purpose: Study on gold based therapeutic agents for cancer cells deracination has become under scrutiny in recent years owing to effective treatments are not available for rapidly progressive cancers. The aim of present study was to examine efficiency of radioactive (198)Au/PAMAMG4 and non-radioactive (197)Au/PAMAMG4 nancomposites against 4T1 and MCF7 breast cancer cell lines. Methods: The PAMAMG4 dendrimer was treated with the gold anions and then, the mixture was chemically reduced by NaBH4. Prepared (197)Au/PAMAMG4 was bombarded by thermal neutrons in the Tehran Research Reactor to (198)Au/PAMAMG4 be produced...
April 2017: Advanced Pharmaceutical Bulletin
Z Sanjabi Eznaveh, J E Antonio-Lopez, J Anderson, A Schülzgen, R Amezcua-Correa
We present a novel design of a micro-structured large-pitch, large-mode-area (LMA) asymmetric rod-type fiber. By reducing the cladding symmetry through six high-refractive index germanium-doped silica inclusions, the fiber features strong higher-order mode (HOM) delocalization, leading to a potentially enhanced preferential gain for the fundamental mode in active fibers. In addition, high resolution spatially and spectrally (S<sup>2</sup>) resolved mode analysis measurements confirm HOM contributions below 1% and LP<sub>1m</sub>-like HOM contributions below the detection limit...
May 15, 2017: Optics Letters
Wei Wang, Dian Lei, Yuan Dong, Xiao Gong, Eng Soon Tok, Yee-Chia Yeo
We developed a new digital etch process that allows precise etching of Germanium or Germanium-tin (Ge1-x Sn x ) materials. The digital etch approach consists of Ge1-x Sn x oxide formation by plasma oxidation and oxide removal in diluted hydrochloric acid at room temperature. The first step is a self-limiting process, as the thickness of oxide layer grows logarithmically with the oxidation time and saturates fast. Consistent etch rates in each cycle were found on the Ge1-x Sn x samples, with the surfaces remaining smooth after etch...
May 12, 2017: Scientific Reports
Grace Flynn, Kumaranand Palaniappan, Martin Sheehan, Tadhg Kennedy, Kevin Ryan
Herein, we report the high density growth of lead seeded germanium nanowires (NWs) and their development into branched nanowire networks suitable for application as lithium ion battery anodes. The synthesis of the nanowires from lead seeds occurs simultaneously in both the liquid zone (SLS growth) and solvent rich vapor zone (VLS growth) of a high boiling point solvent growth system. The reaction is sufficiently versatile to allow for the growth of nanowires directly from either an evaporated catalyst layer or from pre-defined nanoparticle seeds and can be extended to allowing extensive branched nanowire formation in a secondary reaction where these seeds are coated onto existing wires...
May 12, 2017: Nanotechnology
Zhigang Gao, Yinyao Liu, Jing Ren, Zaijin Fang, Xiaosong Lu, Elfed Lewis, Gerald Farrell, Jun Yang, Pengfei Wang
Selective doping of Ni(2+) in octahedral sites provided by nanocrystals embedded in glass-ceramics (GCs) is crucial to the enhancement of broadband near-infrared (NIR) emission. In this work, a NIR emission with a full-width-at-half-maximum (FWHM) of 288 nm is first reported from ZnGa2O4: Ni(2+) nano-spinels embedded GCs with excellent transparency. A comparison is made of the NIR luminescence properties of Ni(2+) doped GCs containing ZnGa2O4, germanium-substituted ZnGa2O4 nano-spinels (Zn1+x Ga2-2x Ge x O4), and Zn2GeO4/Li2Ge4O9 composite nanocrystals that are free of Ga(3+)...
May 11, 2017: Scientific Reports
Brandon Bonham, Gregory Guisbiers
Silicon-germanium is an important alloy mainly used in thermoelectricity and electronics. However, its thermal and optical properties still need further investigation at the nanoscale. That is why in this study, the size and shape effect on the silicon-germanium phase diagram is investigated through the nano-thermodynamics methodology. As expected, the phase diagram undergoes a shift down in temperature when the size decreases. However, it is demonstrated and explained why the size effect on the solidus-liquidus curves is much stronger than the one on the miscibility gap...
May 11, 2017: Nanotechnology
Joshua Demuth, Eli Fahrenkrug, Luyao Ma, Titilayo Shodiya, Julia I Deitz, Tyler J Grassman, Stephen Maldonado
Deposition of epitaxial germanium (Ge) thin films on silicon (Si) wafers has been achieved over large areas with aqueous feedstock solutions using electrochemical liquid phase epitaxy (ec-LPE) at low temperatures (T ≤ 90 °C). The ec-LPE method uniquely blends the simplicity and control of traditional electrodeposition with the material quality of melt growth. A new electrochemical cell design based on the compression of a liquid metal electrode into a thin cavity that enables ec-LPE is described. The epitaxial nature, low strain character, and crystallographic defect content of the resultant solid Ge films were analyzed by electron backscatter diffraction, scanning transmission electron microscopy, high resolution X-ray diffraction, and electron channeling contrast imaging...
May 9, 2017: Journal of the American Chemical Society
Tingyi Gu, Jia Gao, Evgeny E Ostroumov, Hyuncheol Jeong, Fan Wu, Romain Fardel, Nan Yao, Rodney D Priestley, Gregory D Scholes, Yueh-Lin Loo, Craig B Arnold
Embedding metallic and semiconductor nanoparticles in a chalcogenide glass matrix effectively modifies the optical properties. Such nanostructured materials could play an important role in optoelectronic devices, catalysis and imaging applications. In this work, we fabricate and characterize germanium nanocrystals (Ge NCs) embedded in arsenic sulfide thin films by pulsed laser ablation in aliphatic amine solutions. Unstable surface termination of aliphatic groups and stable termination by amine on Ge NCs are indicated by Raman and Fourier-transform infrared spectroscopy measurements, respectively...
May 9, 2017: ACS Applied Materials & Interfaces
Yuzhong Wang, Hunter P Hickox, Yaoming Xie, Pingrong Wei, Soshawn A Blair, Michael K Johnson, Henry F Schaefer, Gregory H Robinson
Sulfurization of anionic N-heterocyclic dicarbene, [:C{[N(2,6-Pr(i)2C6H3)]2CHCLi}]n (2), with elemental sulfur (in a 1:2 ratio) in Et2O at low temperature gives 3 by inserting two sulfur atoms into the Li-C (i.e., C2 and C4) bonds in polymeric 2. Further reaction of 3 with 2 equiv of elemental sulfur in THF affords 4(•) via unexpected C-H bond activation, which represents the first anionic dithiolene radical to be structurally characterized in the solid state. Alternatively, 4(•) may also be synthesized directly by reaction of 1 with sulfur (in a 1:4 ratio) in THF...
May 12, 2017: Journal of the American Chemical Society
F Bottegoni, C Zucchetti, S Dal Conte, J Frigerio, E Carpene, C Vergnaud, M Jamet, G Isella, F Ciccacci, G Cerullo, M Finazzi
We exploit the spin-Hall effect to generate a uniform pure spin current in an epitaxial n-doped Ge channel, and we detect the electrically induced spin accumulation, transverse to the injected charge current density, with polar magneto-optical Kerr microscopy at a low temperature. We show that a large spin density up to 400  μm^{-3} can be achieved at the edges of the 100-μm-wide Ge channel for an applied electric field lower than 5  mV/μm. We find that the spin density linearly decreases toward the center of the Ge bar, due to the large spin diffusion length, and such a decay is much slower than the exponential one observed in III-V semiconductors, allowing very large spin accumulations over a length scale of tens of micrometers...
April 21, 2017: Physical Review Letters
Richard Rojas Delgado, Robert M Jacobberger, Susmit Singha Roy, Vijay Saradhi Mangu, Michael S Arnold, Francesca Cavallo, Max G Lagally
The oxidation of Ge covered with graphene that is either grown on or transferred to the surface is investigated by X-ray photoelectron spectroscopy, Raman spectroscopy, and transmission electron microscopy. Graphene properly grown by chemical vapor deposition on Ge(100), (111), or (110) effectively inhibits room-temperature oxidation of the surface. When graphene is transferred to the Ge surface, oxidation is reduced relative to that on uncovered Ge but has the same power law dependence. We conclude that access to the graphene/Ge interface must occur via defects in the graphene...
May 15, 2017: ACS Applied Materials & Interfaces
Zhaowen Dong, Crispin R W Reinhold, Marc Schmidtmann, Thomas Müller
The synthesis of a new type of silylene 1 is reported. It adopts a bicyclo[2.1.1]hexene structure in which a hafnocene group is incorporated. The silylene is stabilized by homoconjugation with the remote C═C double bond. This is indicated by its highly shielded (29)Si NMR chemical shift (δ(29)Si = -155) and is firmly established by its experimental molecular structure from XRD analysis. The results of a detailed bonding analysis based on DFT calculations suggest for model compounds of silylene 1 and for its heavier germanium, tin, and lead homologues uniformly electronic structures of carbene analogues that are stabilized by homoconjugation...
May 12, 2017: Journal of the American Chemical Society
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