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We have studied the humidity dependence of the electrical properties in hydrogenated amorphous carbon (a-C:H) films. The films were prepared in two stages combining the techniques of physical deposition in vapor phase evaporation (PAVD) and plasma pulsed nitriding. They were deposited over printed circuit boards made of synthetic resin FR2, predesigned to measure DC and AC transport. The Raman spectrum showed a broad peak whose two components are characteristics of a-C:H. By treating the sample in N 2 -H 2 plasma, the impedance became intrinsically sensitive to the relative humidity (RH) of the surrounding media. We observed that when RH increased, the electrical impedance (Z) of the films diminished. The complex impedance spectroscopy method was used to analyze the interaction between the water molecules and the a-C:H film. The main contribution to the humidity dependency of Z came from the resistivity component. The present work provides a fundamental support to develop humidity sensors based on the variation of the impedance of a-C: H films.

In the present paper, five different operating conditions of a plasma nitriding process on annealed AISI H13 were investigated. A systematic variation of processing parameters such as gas mixture, time of processing and current density has been carried out in order to study their effect on microstructure. X-ray diffraction, microhardness testing and scanning electron microscopy techniques coupled with semiquantitative energy dispersive X-ray analysis were used to characterise the nitrided samples. The results revealed that the current density during plasma processing has a considerable influence on both the compound layer formation and depth of the diffusion zone. Also, it has been shown that the geometrical configuration of the workload may affect the uniformity of the diffusion zone, giving rise to the presence of heterogeneous nitrogen distribution zones along it.

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