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Growth, thermal reaction, and crystalline structure of ultrathin iron silicide films on Si͑111͒ are studied by low-energy electron diffraction ͑LEED͒ and Auger electron spectroscopy ͑AES͒. The structural development of silicide layers is monitored in dependence on iron coverage and annealing temperature. Below approximately 10 monolayers ͑ML͒ of iron, two film structures appear, that are not stable in bulk material, while above that limit a switch to the bulk structures is observed. The morphology of the films is strongly dependent on the growth conditions. Their homogeneity can be considerably improved by simultaneous deposition ͑coevaporation͒ of Fe and Si in the desired stoichiometry compared to annealing predeposited Fe films. This improvement is accompanied by the suppression of pinholes in the film. The Fe:Si stoichiometry of the (1ϫ1) and (2ϫ2) phase can be assigned 1:1 and 1:2, respectively. The crystal structure of the former was previously determined to be CsCl, so called c-FeSi. For codeposition in 1:2 stoichiometry an initially disordered (1ϫ1) phase transforms to a well ordered (2ϫ2) phase after annealing. For these phases, ␥-FeSi 2 in CaF 2 structure, the tetragonal ␣-FeSi 2 or an iron depleted variant of the CsCl structure are compatible with LEED and angle resolved AES results. In case of 1:2 stoichiometric films, the stability range of the (2ϫ2) periodic phase can be extended to more than 60 Å ͑equivalent to more than 20 ML Fe͒ by coevaporation.

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In this paper we report on the transport properties of hydrogenated amorphous carbon (a-C:H) which is an attractive material for strain gauges and can also be used in flow meters, accelerometers and vibrational sensors. The a-C:H films were deposited at −350 V bias voltage on silicon (Si) substrates using plasma assisted chemical vapor deposition (PACVD). Current–voltage characteristics of a-C:H/n-Si heterojunctions show ohmic behavior within operating voltages of ±1 V. In the higher voltage range the Frenkel–Poole mechanism is dominant. Conduction is thermally activated at temperatures ranging from 23 °C to 150 °C. The activation energy amounts to 0.48 eV. A-C:H resistors are successfully integrated as strain gauges in Si bulk micromachined force sensors. Piezoresistive gauge factors are measured for the a-C:H strain gauge resistors in the temperature range 23–60 °C. The measured piezoresistive gauge factors are in between 40 and 90 for a-C:H with resistivities in the range 100–700 MΩ cm.