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Browsing Articole din publicaţii internaţionale by Author "FÖLL, H."

Browsing Articole din publicaţii internaţionale by Author "FÖLL, H."

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  • Cathodoluminescence microanalysis of porous GaP and InP structures 
    TIGINYANU, I. M.; LANGA, S.; SIRBU, L.; MONAICO, E.; STEVENS-KALCEFF, M. A.; FÖLL, H. (EDP Sciences, 2004)
    Electron microscopy and cathodoluminescence (CL) microanalysis were used for a comparative study of porous layers fabricated by electrochemical etching of n-GaP and n-InP substrates in aqueous solutions of sulfuric and ...
  • A comparison of pores in silicon and pores in III–V compound materials 
    CHRISTOPHERSEN, M.; LANGA, S.; CARSTENSEN, J.; TIGINYANU, I. M.; FÖLL, H. (WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim, 2003)
    This paper compares the morphologies of porous silicon and porous III–V compounds and discusses their growth mechanisms. Looking into the fine structure of pores, in silicon (meso)pores with intercalating octahedra are ...
  • Correlation between morphology and cathodoluminescence in porous GaP 
    STEVENS-KALCEFF, M. A.; TIGINYANU, I. M.; LANGA, S.; FÖLL, H.; HARTNAGEL, H. L. (American Institute of Physics, 2001)
    Porous layers fabricated by anodic etching of n-GaPn-GaP substrates in a sulfuric acid solution were studied by electron microscopy and cathodoluminescence (CL) microanalysis. The morphology of porous layers was found to ...
  • Design and Characterization of Novel Focusing Elements Based on Photonic Metamaterials 
    TIGINYANU, I. M.; FOCA, E.; SERGENTU, V. V.; URSAKI, V. V.; DASCHNER, F.; KNÖCHEL, R.; FÖLL, H. (American Scientific Publishers, 2009)
    New results in the development of photonic metamaterials based on two dimensional periodic dielectric structures are reported. We show that concave and flat lenses consisting of homogeneous or inhomogeneous dielectric rods ...
  • Design of negative-refractive-index materials on the basis of rods with a gradient of the dielectric constant 
    SERGENTU, V. V.; URSAKI, V. V.; TIGINYANU, I. M.; FOCA, F.; FÖLL, H.; BOYD, Robert W. (American Institute of Physics, 2007)
    The authors propose an approach to the design of negative-refractive-index materials based on the use of dielectric rods with a gradient of the dielectric constant. A triangular-lattice photonic crystal assembled from ...
  • Efficient focusing with a concave lens based on a photonic crystal with an unusual effective index of refraction 
    FOCA, E.; FÖLL, H.; DASCHNER, F.; SERGENTU, V. V.; CARSTENSEN, J.; FREY, S.; KNÖCHEL, R.; TIGINYANU, I. M. (WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim, 2005)
    This work reports measurements with a concave lens based on a photonic crystal (PC) structure, which was designed to have an effective index of refraction neff < 1 or even < 0, and which is intended as a model system for ...
  • Electrochemical pore etching in Ge 
    LANGA, S.; CHRISTOPHERSEN, M.; CARSTENSEN, J.; TIGINYANU, I. M.; FÖLL, H. (WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim, 2003)
    Nucleation and growth of electrochemically obtained pores on (111) and (100) oriented n-Ge in different electrolytes was investigated. On rough surfaces pore density increases as the current density increases, whereas on ...
  • Electrochemical pore etching in Ge – An overview 
    FANG, C.; FÖLL, H.; CARSTENSEN, J.; LANGA, S. (WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim, 2007)
    While electrochemical pore etching in semiconductors has become a thriving field for research (and applications) in the past 15 years or so, little work has been done in Ge. Besides Si, Ge is the only semiconductor with a ...
  • Engineering porous III-Vs 
    FÖLL, H.; LANGA, S.; CARSTENSEN, J.; LÖLKES, S.; CHRISTOPHERSEN, M.; TIGINYANU, I. M (ELSEVIER, 2003)
    Porous semiconductors exhibit new and unexpected properties compared to the bulk materials. In III-Vs, many, many new features with respect to optical properties have emerged during the last few years for certain pore ...
  • Engineering the morphology of porous InP for waveguide applications 
    LANGA, S.; LÖLKES, S.; CARSTENSEN, J.; HERMANN, M.; BÖTTGER, G.; TIGINYANU, I. M.; FÖLL, H. (WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim, 2005)
    We research the possibilities for engineering the morphology of porous structures in n-InP. Lithographic patterning of the sample surface before anodic etching is shown to modify considerably the electric field distribution ...
  • Fast pore etching 
    FREY, S.; KEMELL, M.; CARSTENSEN, J.; LANGA, S.; FÖLL, H. (WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim, 2005)
    The growth of silicon macropores under high current densities and high HF concentrations is studied. A new growth mode for porous Si has been found where pores resemble the so-called current line oriented pores previously ...
  • Focusing effect of photonic crystal concave lenses made from porous dielectrics 
    SERGENTU, V. V.; FOCA, E.; LANGA, S.; CARSTENSEN, J.; FÖLL, H.; TIGINYANU, I. M. (WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim, 2004)
    In the present paper we show the photonic band structure and transmittance spectra of photonic crystal (PC) consisting of porous dielectric and compare the results with the earlier published. Frequency ranges, where PC can ...
  • Focusing slabs made of negative index materials based on inhomogeneous dielectric rods 
    SERGENTU, V. V.; URSAKI, V. V.; TIGINYANU, I. M.; FOCA, E.; FÖLL, H.; BOYD, Robert W. (WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim, 2006)
    We show the advantages of using inhomogeneous dielectric rods to design photonic crystals that behave as materials with negative refractive index. We found that the analysis of light scattering properties of inhomogeneous ...
  • Formation of metal wire arrays via electrodeposition in pores of Si, Ge and III–V semiconductors 
    FANG, C.; FOCA, E.; SIRBU, L.; CARSTENSEN, J.; FÖLL, H.; TIGINYANU, I. M. (WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim, 2007)
    Deep straight macropores in n-type Si have been completely filled with copper (Cu). Homogeneous metal deposition inside the deep pores was achieved by means of electroplating using a solution containing only CuSO4 mixed ...
  • Formation of Porous Layers with Different Morphologies during Anodic Etching of n-InP 
    LANGA, S.; TIGINYANU, I. M.; CARSTENSEN, J.; CHRISTOPHERSEN, M.; FÖLL, H. (The Electrochemical Society, 1999)
    Two different morphologies of porous layers were observed in (100)-oriented anodically etched in an aqueous solution of . At high current density anodization leads to the formation of so-called current-line oriented ...
  • The Impact of Porosity upon the Cathodoluminescence from III-V Compounds 
    STEVENS-KALCEFF, M. A.; TIGINYANU, I. M.; LANGA, S.; FÖLL, H. (Cambridge University Press, 2002)
    The development of applications involving porous materials requires understanding of their special properties. Most published investigations have used photoluminescence (PL) techniques to determine the average emission ...
  • Impedance Spectroscopy as a Powerful Tool for Better Understanding and Controlling the Pore Growth Mechanism in Semiconductors 
    COJOCARU, A.; FOCA, E.; CARSTENSEN, J.; LEISNER, M.; TIGINYANU, I. M.; FÖLL, H. (Springer, Berlin, Heidelberg, 2009)
    This work shows new results towards a better understanding of macropore growth in semiconductor phenomenology by using in-situ FFT impedance spectroscopy. A new interpretation of the voltage impedance is proposed. In ...
  • Large area etching for porous semiconductors 
    CARSTENSEN, J.; CHRISTOPHERSEN, M.; LÖLKES, S.; OSSEI-WUSU, E.; BAHR, J.; LANGA, S.; POPKIROV, G.; FÖLL, H. (WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim, 2005)
    While electrochemical etching of small samples in the 1 cm region is relatively easy, this is not true for large areas, i.e. standard wafer sizes up to 300 mm. The paper outlines the specific demands and difficulties in ...
  • Luminescence of GaN nanocolumns obtained by photon-assisted anodic etching 
    TIGINYANU, I. M.; URSAKI, V. V.; ZALAMAI, V. V.; LANGA, S.; HUBBARD, S.; PAVLIDIS, D.; FÖLL, H. (American Institute of Physics, 2003)
    GaN nanocolumns with transverse dimensions of about 50 nm were obtained by illumination-assisted anodic etching of epilayers grown by metalorganic chemical vapor deposition on sapphire substrates. The photoluminescence ...
  • Morphology and chemical composition microanalysis of 2D and 3D ordered structures on porous InP 
    LANGA, S.; SIRBU, L.; MONAICO, E.; CARSTENSEN, J.; FÖLL, H.; TIGINYANU, I. M. (WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim, 2005)
    Porous InP proves to be promising for use in nanotechnologies due to the possibility to fabricate ordered structures like two-dimensional (2D) single crystals of nanopores. The main goal of this paper is to demonstrate ...

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