A sol-gel procedure using acetic anhydride as a substitute for water using a condensing reagent for the tetraethoxysilane (TEOS) to silica conversion is reported. The mixed solution obtained from the reaction of TEOS and acetic anhydride at 110 °C was allowed to stand in air for several weeks, resulting in gel formation of the solution. This prepared silica was mesoporous based on the nitrogen adsorption-desorption isotherms. Even when the gelation was performed in the presence of a large amount of benzene, silica was also obtained. The immobilization of a cubic µ-oxo Si-Ti complex, which is a good homogeneous catalyst for the epoxidation of olefins, in a silica matrix was achieved by using this technique. Although the complex readily afforded TiO 2 anatase on treatment with water, no free TiO 2 phase was found in the solid obtained by this procedure according to XRD, DR-UV-vis, and Raman spectra. The titanium was highly dispersed in the silica matrix. On the other hand, a solid prepared by the same procedure using titanium tetra-isopropoxide as the titanium source contained the TiO 2 anatase phase. The obtained SiO 2 -TiO 2 mixed oxide solid was an effective heterogeneous catalyst for the highly efficient epoxidation of cyclohexene in the liquid phase by tert-butylhydroperoxide.

In recent years, there has been a great interest in new routes for depositing GaN films in the application of III-V semiconductors. We report herein on the deposition of highly crystalline GaN films by low-pressure MOCVD (in the low-temperature range of 500-700 °C and the pressure range of 77-177 mbar) using the single-source precursor (Et 2 GaNH 2 ) 3 . This process was investigated for a variety of substrates (Si(100) and polycrystalline Al 2 O 3 ) using a cold wall chemical vapor deposition reactor. The thickness of films grown under these conditions ranged from 6 to 8 µm, and the growth rates varied from 7 to 8 µm/h. Films deposited at lower temperatures (500-550 °C) had a pale yellowish color and were amorphous. At 600 °C slightly gray colored films were obtained, while above 650 °C highquality crystalline films were formed, which show diffraction patterns characteristic of the hexagonal wurtzite structure. The films are consistent with the 1:1 stoichiometry of GaN and have carbon and oxygen as impurities; however, cracks were not evident on the surface by SEM examination up to a magnification of 30 000. In contrast, samples of GaN deposited under high-vacuum conditions (up to 10 -2 mbar) have neither a 1:1 stoichiometry nor a smooth surface morphology. Atomic force microscopy, scanning electron microscopy, Auger electron microscopy, and energy-dispersive X-ray analyses were used for the study of the structure, composition, and morphology of the films.

AlSb films have been grown on Si (100) (2) without any carrier gas. The best condition for a high quality AlSb film depends on the ligands of the precursor. The AlSb film is deposited at a temperature about 50 C lower when precursor 1 is used instead of 2. The films are consistent with the 1:1 stoichiometry in the optimized temperature range of 375±425 C for 1 and 425±475 C for 2, whereas at other temperatures the films are contaminated with Si. The deposition rate is mainly kinetics limited and ranges from 5 to 9 mm/h. X-ray diffraction (XRD), scanning electron microscopy (SEM), atomic force microscopy (AFM), energy dispersive X-ray spectrometry (EDS), and wavelength dispersive spectrometry (WDS) were used to characterize the films.

Dedicated to Professor Guy Ourisson on the occasion of his 75th birthday In 2 O 3 films have been grown on polycrystalline Al 2 O 3 using low-pressure metal±organic (LP-MO) CVD in the temperature range 250±400 C with the new single-source precursors [Et 2 InOH´Et 2 InNH 2 ] (1) and [ i Pr 2 InOH´iPr 2 InNH 2 ] (2), using a purified nitrogen stream as the carrier gas. The preparation and properties of compounds 1 and 2 are reported. X-ray diffraction (XRD), scanning electron microscopy (SEM), ultraviolet-visible (UV-vis) spectroscopy, and energy dispersive X-ray (EDX) spectrometric analyses were used to characterize the films.

CdSe is one of the most promising photoelectrochemical materials. A common problem of the CVD of multicomponent systems is obtaining the appropriate stoichiometry in the gas phase. This can be overcome by using single source precursors containing the required elements. This communication reports on an improved precursor of this type. The figure shows an AFM image of a layer of CdSe on silica. Conclusions are drawn about the growth mechanism.