Deposition of copper oxide (Cu2O,CuO) thin films at high temperatures by plasma-enhanced CVD

Copper-oxide films are deposited by plasma-enhanced CVD using copper acetylacetonate as a precursor. The influence of various experimental parameters on deposition rate, film composition and resistivity have been studied. The substrate temperature and the bias are the parameters which affect these properties the most. An increase of the substrate temperature changes the phases of the deposit from Cu₂O-CuO over Cu₂O to Cu. At temperatures 500° C the deposition rates are high but the films consist mainly of metallic Cu. A negative bias enhances the deposition rate only slightly but has a strong effect on the film composition and can completely balance the oxygen deficiency. At a bias of –120 V the films consist of pure CuO even at temperatures 500° C.     

Determination of the gravitational constant with a beam balance

The Newtonian gravitational constant G was determined by means of a novel beam-balance experiment with an accuracy comparable to that of the most precise torsion-balance experiments. The gravitational force of two stainless steel tanks filled with 13 521 kg mercury on 1.1 kg test masses was measured using a commercial mass comparator. A careful analysis of the data and the experimental error yields G=6.674 07(22)x10(-11) m(3) kg(-1) s(-2). This value is in excellent agreement with most values previously obtained with different methods.     

Application of μ SR to radiation damage in metals

Proton-irradiated Al, Cu and Ni foils have been investigated by the SR technique. No trapping of ⁺ has been observed in the temperature range investigated (<300 K). In Ni a temperature-independent increase of the depolarisation rate by a factor of three is found for the irradiated target. This change is attributed to field inhomogeneities produced by defects.     

Muon site determination in orthoferrites

SR measurements in various orthoferrites are described. By comparing the measured internal fields with calculated dipolar fields the muon position was found to be in thez=1/4 mirror plane, 1 å from the nearest oxygen ion, implying the formation of an O ^– ion.     

AμSR apparatus with high time resolution

A high time resolutionSR apparatus is described. The set up is mainly used for precision measurements of the muonium hyperfine interaction.     

Initial or thermally controlled impurity trapping of muons in niobium?

We have studied muon depolarization in some very well characterized samples of niobium (pure Nb with <1 ppm impurities and Nb doped with 15 at.ppm N and 53 at.ppm Ta, respectively). This has allowed us to separate the influence of substitutional and interstitial impurities on theSR linewidth. The purest sample shows a low but non-zero linewidth from 0.1 to 70 K. Ta-doping increases the width strongly below 20 K. while N-doping gives a broad maximum between 30–70 Kand a considerable width below 20 K.Conventional two-trap models cannot explain the occurrence of a linewidth significantly lower that that predicted for static ⁺ and constant over a wide temperature range. A consistent explanation of these three observations can however be obtained from the following model: In pure Nb only a fraction of the muons is self-trapped thermally; the other muons do not form small polarons but remain in a propagating metastable nonlocalized state. Impurities can catalyse further initial polaron formation, decreasing the metastable fraction. This process causes temperature-independent plateaus in up to the detrapping temperature. The muons localized at shallow traps (Ta induced) can diffuse at higher temperatures and be trapped again at deeper traps (associated with the N-impurities).