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Energy Systems and Technologies for the Coming Century ...

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our study to a single set of deposition parameters. The tested changes of <strong>the</strong> targetcomposition from stoichiometric YBa 2 Cu 3 O x are small (≤ 5% of overall cationcomposition), <strong>and</strong> <strong>the</strong> effect of <strong>the</strong> target composition on <strong>the</strong> composition of <strong>the</strong> film isconsidered to be linear.Two self-made targets (Ba-excess <strong>and</strong> Cu-deficient) were used <strong>for</strong> tests of <strong>the</strong> transfer ofelement composition from <strong>the</strong> target to <strong>the</strong> growing film, toge<strong>the</strong>r with a commerciallyavailable stoichiometric YBa 2 Cu 3 O x target. The accuracy of <strong>the</strong> film elementcomposition measurement was 3-4% of <strong>the</strong> signal, i.e., better than 2% of <strong>the</strong> overallcation composition.The nominal compositions of <strong>the</strong> targets <strong>and</strong> <strong>the</strong> results of <strong>the</strong> measurements aresummarized in Table 1. All films contain an excess of Ba, with almost <strong>the</strong> same relativecontent of Ba in all films. The heaviest element, Ba, is least scattered by <strong>the</strong> thinatmosphere in <strong>the</strong> chamber <strong>and</strong>, hence, we observe a higher amount of Ba on <strong>the</strong>substrate surface, compared to Y <strong>and</strong>, especially, Cu (lightest element). A probablereason <strong>for</strong> <strong>the</strong> almost constant Ba contents is re-sputtering or re-evaporation of Ba <strong>and</strong>BaO (Ba is not incorporated into less volatile oxides).Ano<strong>the</strong>r important feature of <strong>the</strong> transfer of composition to YBCO films is <strong>the</strong> essentialdependence of <strong>the</strong> composition on <strong>the</strong> contents of yttrium in <strong>the</strong> target (Fig. 1). Theyttrium content in <strong>the</strong> film increases almost linearly with an increase of <strong>the</strong> nominalyttrium content in <strong>the</strong> target, while <strong>the</strong> copper content decreases. This is probably a resultof <strong>the</strong> scattering on <strong>the</strong> way from target to substrate: <strong>the</strong> higher <strong>the</strong> concentration ofheavy atoms in <strong>the</strong> plume, <strong>the</strong> stronger <strong>the</strong> scattering of <strong>the</strong> lighter copper atoms.Table 1. Cation compositions of (Y,Ba,Cu)O z targets <strong>and</strong> corresponding films (~0.5 μmthick). All cation compositions, except target nominal composition, are normalized to 6.Sample Target composition Film composition Excessmaterialnominal normalized by 6 by ICP by EDAX *HLP09 1/2.3/3 0.952:2.191:2.857 0.897:2.188:2.915 0.947:2.268:2.785 0:0.394:0.224 #HLP08 1/2/3 1.000:2.000:3.000 0.972:2.275:2.753 0.950:2.263:2.787 0.054:0.439:0 #HLP10 1/2/2.85 1.026:2.051:2.923 1.048:2.308:2.644 1.016:2.257:2.727 0.167:0.546:0 #HLP07 1.5/2/3 1.385:1.845:2.770 1.349:1.932:2.719 0.443:0.120:0@* calibrated using ICP data# calculated on ICP data@ calculated using EDAX dataRisø International <strong>Energy</strong> Conference 2011 Proceedings Page 240

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