Very thin,highly‐conductive ZnO:Al front electrode on textured glass as substrate for thin‐film silicon solar cells

A very thin (250 nm), highly conductive (annealed), non‐texturized DC‐sputtered aluminum‐doped zinc oxide layer (ZnO:Al) deposited on a textured glass is used as substrate for thin‐film silicon solar cells. Compared to the classical approach, where wet‐chemically texturized ZnO:Al on planar glass is used, this approach allows a reduction in the as‐deposited ZnO:Al thickness of almost 70% while at the same time, thanks to the good light trapping capability of the glass texture the efficiency of the cells was maintained at the high level of 10.9%.

     

Preparation of <Emphasis Type="Italic">p</Emphasis>-type conducting transparent CuCrO<Subscript>2</Subscript> and CuAl<Subscript>0.5</Subscript>Cr<Subscript>0.5</Subscript>O<Subscript>2</Subscript> thin films by sol–gel processing

CuCrO₂ and CuAl_0.5Cr_0.5O₂ thin films were prepared by sol–gel processing and subsequent two-step annealing in air and inert gas atmosphere. Phase pure films with delafossite structure were obtained by adjusting the respective temperatures. The related phase development strongly affects the optical and electrical performance, giving leeway for optimization. The resulting CuCrO₂ (16 Ωcm, transmittance 21%) and CuAl_0.5Cr_0.5O₂ (11 Ωcm, transmittance 49%) films showed p-type conductivity by their positive Seebeck coefficients. The microstructure of the systems was characterized by scanning and transmission electron microscopy and correlated to the growth of different crystalline phases during the annealing steps. Thereby, crystal thermodynamics also affects the respective film performance, alleviating delafossite formation from the amorphous phase.     

Die Diffusionskoeffizienten und mittleren freien Weglängen der geladenen und neutralen Radon-Folgeprodukte in Luft

The knowledge of the diffusion coefficients of radioactive atoms and ions in air is very important in a number of investigations on and computations of the attachment of radon decay products to aerosol particles. In this work measurements of the diffusion coefficients of neutral and charged²¹²Pb atoms are reported. The values found areD ₀=(7.6±0.4)·10^?2cm²s^?1 for neutral atomsD=(5.0±0.3)·10^?2cm²s^?1 for charged atoms The used method of measurement allowed to determine these constants 1–5 seconds after the formation aged²¹²Pb atoms, so that a “cluster” formation was improbable. The mean free path for neutral (λ₀=(4.9±0.3)·10^?6cm) and charged (λ=(3.2±0.2)· 10^?6cm) lead 212 atoms in air were computed from the measured diffusion coefficients. All obtained results were compared with values, calculated from theory.     

Consequences of nuclear electron capture in core collapse supernovae

The most important weak nuclear interaction to the dynamics of stellar core collapse is electron capture, primarily on nuclei with masses larger than 60. In prior simulations of core collapse, electron capture on these nuclei has been treated in a highly parametrized fashion, if not ignored. With realistic treatment of electron capture on heavy nuclei come significant changes in the hydrodynamics of core collapse and bounce. We discuss these as well as the ramifications for the postbounce evolution in core collapse supernovae.     

Phase-stabilized 4-fs pulses at the full oscillator repetition rate for a photoemission experiment

Compressing pulses of a mode-locked extended-cavity Ti:sapphire laser using a standard single-mode fiber and tilted-front-interface chirped mirrors yields phase-stabilized 4-fs, 3-nJ light pulses at the full, 24-MHz, repetition rate. The demonstrated source paves the way towards exploring interactions sensitive to the carrier-envelope-offset phase, such as, for example, photoemission from solid targets at moderate intensities (∼10¹² W/cm²). Received: 13 December 2002 / Published online: 26 February 2003 RID="*" ID="*"Corresponding author. Fax: +43-1/58801-38799, E-mail: apolonski@tuwien.ac.at     

A new ferroelectric compound: Methylammonium trichloromercurate (CH3NH3HgCl3)

Measurements of the dielectric constants revealed a ferro- to paraelectric transition in methylammonium trichloromercurate (CH₃NH₃HgCl₃). Thermal analysis by differential scanning calorimetry indicates a transition temperature of Tc ≈ 60°C. The structures of both phases were determined from single crystal X-ray measurements. The ferroelectric phase crystallizes at room temperature in the polar trigonal space group $\text{P}\text{3}{}_2\text{(a = b =}\text{7.8117(3)}\text{, c =}\text{9.826(3)}\text{A}\text{?}\text{, Z =}\text{3}\text{)}$. The refinement of the ferroelectric structure included the fractional contribution of the two domains present. The paraelectric phase has monoclinic symmetry (space group C2 with $\text{a =}\text{13.816(2)}\text{, b =}\text{7.880(1)}\text{, c =}\text{9.734(3)}\text{A}\text{?}\text{, β =}\text{90.49(5)°}\text{, Z =}\text{6}\text{)}$ and contains an almost completely disordered methylammonium group while order with pronounced thermal motion is observed in the ferroelectric phase.     

Observation of light-phase-sensitive photoemission from a metal

We demonstrate that multiphoton-induced photoelectron emission from a gold surface caused by low-energy (unamplified) 4-fs, 750-nm laser pulses is sensitive to the timing of electric field oscillations with respect to the pulse peak. This observation confirms recent theoretical predictions and opens the door to measuring the absolute value of the carrier-envelope phase difference of few-cycle light pulses with a solid-state detector.     

Characterisation of a laser droplet formation process by acoustic emission

The aim of this article is to describe an application of acoustic emission to characterise a process of laser droplet formation from a metal wire. Laser droplet formation is a crucial process in new laser droplet welding technology, where parts are joined by means of the heat content of a liquid metal droplet deposited onto the parts to be joined. A laser beam is used for heating and melting the wire tip, and for detaching the molten pendant droplet. Depending on the process parameters, three different outcomes of the process can be observed: (1) no droplet formed; (2) a droplet formed but not detached; (3) a droplet formed and detached from the wire. It is shown that AE can be used to monitor the process and to indicate the different process outcomes.