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5,10,15,20 meso-tetraphenyl porphyrin (H2TPP) and copper phthalocyanine (CuPc) films have been deposited by means of a recently developed plasma based technique named glow discharge induced sublimation (GDS). The two macrocycles have been deposited by vacuum evaporation (VE) and H2TPP by spin coating (SPIN) as well for comparison. The physical properties of the films have been characterized by means of scanning electron microscopy (SEM) and nitrogen physisorption measurements. SEM images and physisorption isotherms highlight both the much higher surface roughness and specific surface area of GDS samples with respect to the VE and SPIN ones. Optical sensing measurements, performed in differently concentrated ethyl alcohol atmospheres, highlight that GDS samples yield much higher response intensities than SPIN and VE films, short response times and complete recovery.
Ternary W-Si-N thin films have been reactively sputter-deposited from a
W5Si3 target at different nitrogen partial pressures. The composition has
been determined by 2.2 MeV4He+ beam, the structure by
x-ray diffraction and transmission electron microscope, the chemical bonds
by Fourier transform - infrared spectroscopy and the surface morphology by
scanning electron microscopy. Electrical resistivity was measured by four
point probe technique on the as grown films. The film as-deposited is
amorphous with the Si/W ratio increasing from about 0.1 up to 0.55 with the
nitrogen content going from 0 to 60 at%. The heat treatments up to 980 °C
induce a loss of nitrogen in the nitrogen rich samples. Segregation of
metallic tungsten occurs in the sample with low nitrogen content
(W58Si21N21). Samples with high nitrogen
content preserve the amorphous structure, despite of the precipitation of a
more ordered phase inferred by FT-IR absorbance spectrum of the layer
treated at highest temperature. The surface morphology depends upon the
nitrogen content; the loss of nitrogen induces the formation of blistering
and in the most nitrogen rich sample the formation of holes. Electrical
resistivity preliminary results on the as grown layers range between 500 and
4750 μωcm passing from the lowest to the highest N concentration.
The Mo-W-O thin films were deposited by RF reactive sputtering from composite target of W and Mo (20:80 weight ratio). Structural characterisation was carried out by X-ray diffraction spectroscopy and the composition of the film was obtained by Rutherford backscattering analysis. The layers were investigated by volt-amperometric technique for electrical and gas-sensing properties. The films were capable of sensing CO. No effect of poisoning of the surface was recorded and recovery of the resistance was complete. A concentration of CO as low as 15 ppm produced a relative variation in the conductance of 390% with response and recovery times of about 2 minutes at a working temperature of 200°C.
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