H. Van Den Bergh

Kinetic and thermodynamic properties of INO and INO2 intermediate complexes in iodine recombination

The recombination of iodine atoms after laser flash photolysis has been studied in the presence of NO or NO2 at 320–450 K and 0–200 atm of He. The reaction proceeds in two stages. The first stage is governed by the recombination I+NO(+He) →INO(+He) or I+NO2(+He) →INO2(+He), for which the full falloff curves are derived. The second stage is governed either by reaction between two INO (or INO2) molecules, or, at higher temperatures, by thermal decomposition of INO (or INO2). The reaction involves the elementary steps of a typical intermediate complex mechanism of atom recombination. The rates of all of these elementary steps can be separated. From the I+NO⇄INO and I+NO2⇄INO2 equilibrium constants the enthalpies of formation of INO and INO2 of ΔHfo298(INO) =29.0±1 kcal mol−1 and ΔHfo298(INO2) =14.4±1 kcal mol−1, respectively, are derived.

Electric and magnetic field effects in the infrared multiphoton dissociation of CF3D

The effect of static elec. and magnetic fields on the IR multiphoton dissocn. (IRMPD) yield of CF3D was investigated in the range 0-4.3 kV cm-1 and 0-17.3 kG. The applied static fields induced increases in the reaction yield of up to a factor of 5 at moderate energy fluences in the essentially collision free dissocn. For all cases considered, the field effects were independent of the orientation of the laser beam polarization relative to the direction of the applied elec. and magnetic fields. At higher pressures, where collisions enhanced the reaction yield, lower yields were obsd. in the 17.3 kG magnetic field than in the magnets residual field of .apprx.100 G. The measurements on the magnetic field effect were completed with new results on the IRMPD of CF2HCl. Possible IR spectral changes induced by a 5 kV cm-1 field in CF3D, CF3H, and CF2HCl were investigated at a resoln. of 0.06 cm-1.

Temperature effect on photolytic deposition of platinum ohmic contacts and schottky diodes

An argon laser is used to induce Laser Chemical Vapor Deposition (LCVD) of platinum using platinum bihexafluoroacetyl-acetonate as precursor. The process can be photolytic or pyrolytic depending on the laser power used. These processes are studied by recording the laser light transmitted through of deposit and substrate. Photolytic deposition takes place either in the adsorbed phase or in the gaseous phase depending on the temperature induced by radiation absorption. The induced-temperature calculation using a model developed by us confirms the experimental results obtained. The influence of the substrate base temperature and the precursor product vapour pressure confirms photolytic deposition from the adsorbed phase for low powers and from the vapour phase onwards for high powers. The deposits obtained present a typical 96% Pt composition and its use in Schottky diode manufacture permit obtaining devices with good characteristics in spite of experimental limitations.

Laser Induced Chemical Vapour Deposition Of Platinum Spots On Glass

Laser induced pyrolytic deposition of platinum spots on glass is studied for different laser powers, beam diameters and irradiation time. Laser powers up to 500 mW give deposition rates of typically 0.5 μm/s. Temperature calculations as a function of the time allows study of the process kinetics according to the thickness and diameter of the spots. Resistivity measurements of platinum lines give comparable values to those of bulk material.