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Gate dielectrics composed primarily of lanthana and zirconia were prepared by reactive evaporation. The stability of the layers during high temperature anneals was investigated. By controlling the oxygen partial pressure during heat treatment, lanthana and zirconia films could be protected against reaction with the underlying Si substrate and against the growth of low-interface layers. The electrical thickness of the dielectrics could be maintained after a 900°C exposure. The critical oxygen pressure at 900°C for low-interface formation beneath ZrO 2 and La 2 O 3 dielectrics was ϳ2e Ϫ4 Torr. The interfaces that formed beneath the ZrO 2 and La 2 O 3 layers are distinctly different. The sub-ZrO 2 interface, influenced primarily by phase separation, tends towards pure SiO 2 , while the sub-La 2 O 3 interface, influenced primarily by silicate formation, tends towards a La-Si-O alloy. For both materials, reducing the oxygen pressure to values below 10 Ϫ7 Torr resulted in rapid degradation of the metal oxide. This dielectric degradation is believed to be linked to SiO evaporation. These results suggest that at high temperatures, a window of optimal oxygen partial pressure exists in which the stability of many oxides in contact with silicon can be achieved.

High‐temperature Fischer–Tropsch synthesis for the production of short‐chain olefins over iron catalysts supported on multiwalled carbon nanotubes (CNTs) was investigated under industrially relevant conditions (340 °C, 25 bar, H2/CO=1) to elucidate the influence of nitrogen and oxygen functionalization of the CNTs on the activity, selectivity, and long‐term stability. Surface functionalization of the CNTs was achieved by means of a gas‐phase treatment using nitric acid vapor at 200 °C for oxygen functionalization (O‐CNTs) and ammonia at 400 °C for the subsequent nitrogen doping (N‐CNTs). Ammonium iron citrate impregnation followed by calcination was applied for the deposition of iron nanoparticles with particle sizes below 9 nm. Subsequent to reduction in pure H2 at 380 °C, the Fe/N‐CNT and Fe/O‐CNT catalysts were applied in Fischer–Tropsch synthesis, in which they showed comparable initial conversion values with an excellent olefin selectivity [S(C3–C6)>85 %] and low chain growth probability (α≤0.5). TEM analysis of the used catalysts detected particle sizes of 23 and 26 nm on O‐CNTs and N‐CNTs, respectively, and Fe5C2 was identified as the major phase by using XRD, with only traces of Fe3O4. After 50 h time on stream under steady‐state conditions, an almost twofold higher activity compared to the Fe/O‐CNT catalysts had been maintained by the Fe/N‐CNT catalysts, which are considered excellent Fischer–Tropsch catalysts for the production of short‐chain olefins owing to their high activity, high selectivity to olefins, low chain growth probability, and superior long‐term stability.

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