Thin plasma-polymerized layers of hexamethyldisiloxane for humidity sensor development

The response of resistive-type sensors based on thin hexamethyldisiloxane layers to relative humidity (RH) was evaluated. Humidity sensitive layers were plasma polymerized at low frequency glow discharge using a capacitively coupled parallel plate reactor. The sensor design comprises the absorbing l...

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Bibliographic Details
Published in:Thin solid films 2009-06, Vol.517 (15), p.4455-4460
Main Authors: Guermat, N., Bellel, A., Sahli, S., Segui, Y., Raynaud, P.
Format: Article
Language:English
Subjects:
Cross-disciplinary physics: materials science
rheology
Electric discharges
Exact sciences and technology
Fourier transform infrared spectroscopy
Glow
corona
Humidity
Ion and electron beam-assisted deposition
ion plating
Materials science
Methods of deposition of films and coatings
film growth and epitaxy
Organosilicon
Physics
Physics of gases, plasmas and electric discharges
Physics of plasmas and electric discharges
Plasma applications
Plasma deposition
Plasma-based ion implantation and deposition
Sensor
Thin films
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Summary:The response of resistive-type sensors based on thin hexamethyldisiloxane layers to relative humidity (RH) was evaluated. Humidity sensitive layers were plasma polymerized at low frequency glow discharge using a capacitively coupled parallel plate reactor. The sensor design comprises the absorbing layer deposited on clean glass substrate with comb-shape aluminum electrodes (interdigitated structure). The change in electrical impedance of the sensing film was monitored as the device was exposed to humidity. The variation of the plasma-polymerization parameters resulted in different humidity sensing properties which could be correlated to the results of Fourier transform infrared spectroscopy (FTIR). The deposited films exhibited a detectable response to RH ranging from 30 to 95% with low hysteresis, good reproducibility and stability in long-term use. Films with a greater thickness showed a significant decrease in the humidity sensing capability. FTIR analysis revealed the presence of SiH bonding groups, which are frequently linked to the film density. The increase in the plasma discharge power induced also a significant decrease in the diffusion process of water vapor inside the sensitive layer bulk.
ISSN:0040-6090
1879-2731
DOI:10.1016/j.tsf.2009.01.084