J. M. Philippoz

Selective low-pressure chemical vapor deposition of copper and platinum

The low pressure chemical vapor deposition of copper and platinum is studied on SiO2 substrates which have been locally prenucleated with ultrathin metal layers of Pt, Cu, Pd, Au, and W. These layers were between 0.1 and 30 A thick and were produced by vacuum evaporation. Copper metal is deposited selectively on top of the prenucleation layers from the gaseous bis‐hexafluoroacetylacetonate {Cu(hfa)2} diluted in hydrogen. High quality copper could be grown at temperatures in the range of 300–400 °C with electrical resistivities as low as 2.5 times the bulk copper value. In contrast, platinum deposited from gaseous Pt(hfa)2 in H2 grows selectively on the clean oxide surface rather than on the areas prenucleated with vacuum evaporated platinum.

Copper Film Growth by Chemical Vapor Deposition Electrical and Optical Measurements in Real Time, and Studies of Morphology

The deposition of copper by low pressure chem. vapor deposition (CVD) from Cu bis-hexafluoroacetylacetonate is monitored in real time and in situ by the measurement of the optical reflectivity and elec. resistance of the growing metal film. Changes of the deposit morphol. during growth were analyzed by interrupting the CVD process at different stages and observing the samples by transmission electron microscopy. Pure copper is deposited at 400 Deg and 1 mbar total reactor pressure of helium, precursor, and water vapor. Two successive regimes are distinguished in the deposition: island formation and continuous film growth. The transition between these two regimes is visible in the real time specular reflectance measurement. The copper deposition rate is twice higher during the island growth than during the continuous film growth at the applied conditions. The influence of a metal seeding layer (from 0.001 monolayer to 1 monolayer) on the Cu deposition is shown both in the real time measurements and in the ex situ anal. of films.

The Raman spectroscopy of diamond films deposited on metal and insulator substrates with varying thermal expansion coefficient

Polycryst. diamond films were deposited by hot filament assisted chem. vapor deposition on five metal and insulator substrates. The films obtained were studied by Raman spectroscopy. The position of the Raman line shifts to higher wavenumbers when the thermal expansion coeff. of the substrate material increases. This effect is interpreted as a result of the internal stress in the diamond films induced by the cooling from the deposition temp. to room temp. The width of the Raman peak ranges from 10.9 to 16.6 cm-1, with a min. when the thermal expansion coeff. of the substrate is close to that of diamond.

Infrared vibrational predissociation spectroscopy of (SF6)mArn clusters: Implications for effective laser isotope separation

Selective infrared vibrational predissociation (IRVP) of Van der Waals clusters in a free jet is shown to be an effective way to separate isotopes. Absolute separation factors α in excess of 1.1 are observed upon irradiation of a beam of SF6 diluted in argon with a 20 W cw CO2 laser. Selection of the wavelength permits enrichment or depletion of any one of the sulfur isotopes in the mixture. In order to understand the observed wavelength dependence of the isotope enrichment we have measured the effective IRVP spectra of the individual Van der Waals clusters (SF6)mArn with 1 ⩽ m ⩽ 3 and n ⩽ 9. A systematic study of these spectra reveals a significant red-shift which occurs upon attaching Ar atoms to (SF6)m. Such shifts can attain as much as 10 cm−1, as in the case between SF6 and SF6Ar9.

Clinical LIF pharmacokinetic measurements with Photofrin II for optimizing the photodetection of early cancer

New results are presented on the pharmacokinetics of the fluorescing fraction of Photofrin II in patients with an early cancer in the oesophagus or the buccal cavity. The light-induced fluorescence signal shows a relatively high contrast between tumor and surrounding normal tissue at short times after i.v. injection. The magnitude of this contrast appears to correlate with the staging of the cancer, the more invasive tumors showing the highest contrast. Some early results on the ex vivo fluorescence analysis of biopsies taken on patients injected with the new sensitizer meta-tetra(hydroxyphenyl)chlorin (mTHPC) demonstrate the selectivity of this efficient second generation photosensitizer for advanced lung cancer. mTHPC appears to have good properties for photodetection and has a rather high rate of photobleaching. The significant of the latter is discussed in relation to simplifying light application in PDT.

A laser-induced chemical transport reaction method for diamond deposition

Diamond growth on a (100) oriented Si substrate by a laser-induced chem. transport reaction (LICTR) method is described. SEM indicated that the LICTR-deposited diamonds had a cubic structure. Their Raman spectrum obsd. at Stokes shifts between 1300 and 1370 cm-1 showed a single sharp line with the position and full width at half-max. very close to those of natural diamond. These results contrast with those obtained for diamond produced by hot-filament CVD.