Progress in the growth of YBa2Cu3O7−x thin films by MOCVD and prospects for large area, low temperature deposition AIP Conf.

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An arrangement for large area PLD on 3-inch wafers is proposed. In order to get a homogeneous stoichiometry and thickness distribution and small variations of superconducting properties on the 3-inch diameter, the substrate is foreseen to be rotated and additionally laterally moved up to 45 mm during deposition whereas the laser plume remains fixed.YSZ buffer layers showed thickness homogeneity of 1% within 10 mm, of 4% within 2 inch and of 8% within 3 inch diameter, respectively. For in-situ deposited YBCO thin films on r-plane sapphire with YSZ buffer layer we inductively measured within 3 inch diameter values of the critical temperature Tc(90%) from 85.9 K to 86.7 K and values of the critical current density jc(77 K) from 1 × 106 to 2 × 106 A/cm2. However, up to now the degree of epitaxy of the YBCO thin films on r-plane sapphire with YSZ buffer layer is lower compared to YBCO on MgO(100) as determined by Raman spectroscopy. Nevertheless, large area PLD seems to be a very promising technique for homogeneous coating of 3-inch wafers by epitaxial oxide thin films.

semiconductors show interesting optical properties (1 to 3 and references therein). In this note we report photoluminescence spectra of tetragonal CdP2 single crystals at 4.2 K which show much more fine structure than the spectra published so far (3, 4).CdP single crystals were grown from the gaseous phase (2) without intentional doping. They were immersed in liquid He and excited with the light of a high pressure mercury lamp. 2 With low spectral resolution our spectra a r e identical with those of (4): two broad bands peaked a t 2.09 and 1.85 eV. With high resolution the high energy part of the 2.09 eV peak shows pronounced fine structure (Fig. 1). This fine structure is very similar to the near gap luminescence of tetragonal ZnP an indirect gap semiconductor with E = 2.200 eV a t T = 4.2 K (1). In ZnP this luminescence is 2' g 2 i ( n m ) Fig. 1. Photoluminescence spectrum of CdP2, T = 4.2 K

The capacitance—voltage characteristics of a quantum well inside a depletion layer is computed self‐consistently by simultaneous integration of Poisson's and Schrönger's equations. Based on the numerical results a method is developed for the determination of the position of the quantum well and the carrier concentration in it from measured C—V profiles.