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High-resolution Laplace deep-level transient spectroscopy (LDLTS) and thermal admittance spectroscopy (TAS) have been used to determine the effect of boron (B) concentration on the electronic states in polycrystalline chemical vapour deposition diamond thin films grown on silicon by the hot filament method. A combination of high-resolution LDLTS and direct-capture cross-sectional measurements was used to investigate whether the deep electronic states present in the layers originated from point or extended defects. There was good agreement between data on deep electronic levels obtained from DLTS and TAS experiments. Two hole traps, E1 (0.29 eV) and E2 (0.53 eV), were found in a film with a boron content of 1 × 10 19 cm −3. Both these levels and an additional level, E3 (0.35 eV), were found when the B content was increased to 4 × 10 19 cm −3. Direct capture cross-sectional measurements of levels E1 and E2 show an unusual dependence on the fill-pulse duration which is interpreted as possibly indicating that the levels are part of an extended defect. The E3 level found in the more highly doped film consisted of two closely spaced levels, both of which show point-like defect characteristics. The E1 level may be due to B-related extended defects within the grain boundaries, whereas the ionization energy of the E2 level is in agreement with literature values from ab initio calculations for B-H complexes. We suggest that the E3 level is due to isolated B-related centres in bulk diamond.

Superconducting Tl-Ca-Ba-CuO thin films less than 1 pm thick have been prepared on Y-stabilized ZrO, (100). MgO (100). and SrTiO, (100) substrates using thermal evaporation and a two-step annealing process involving the growth of BaCuO, films followed by exsilu crystallization and thalliation under thallium oxide vapours. We have been able to fabricate reasonably uniform films of t h e TI,Ca, Ba,Cu,O. (2122) and Ti,Ca,Ba,Cu,O, (2223) superconducting phases, and have successfully reduced the density of impurity phases by controlling the stoichiometry and morphology of the precursor films and the thalliation conditions. In addition, a 150 pm wide, and 1 cm long, track patterned in one of these films using standard photolithography techniques shows a T,, of 102 K. a J, in excess of IO4 A cm-' at 90 K and a strong bolometric response when illuminated with an He-Ne 1 mW laser