Papers by Keyword: HMDSO

Abstract: Humidity sensitive layers elaborated from pure HMDSO and TEOS by PECVD technique have been studied. Humidity sensing properties including impedance relative humidity (RH) and current RH characteristics were investigated. TEOS films show higher sensitivity and excellent linearity over the explored range of humidity (20–95% RH). However, HMDSO films exhibits a small response and recovery of about 8 and 34 s for humidification and desiccation, respectively, in addition to very low hysteresis (2%). Structural analyses of sensitive layers were characterized by Fourier transform infrared spectroscopy (FTIR).

Abstract: Hexamethyldisiloxane (HMDSO) thin films coated quartz crystal microbalance (QCM) electrodes have been characterized for the detection of volatile organic compounds (VOCs). The sensitive coatings were plasma polymerized in pure vapor of HMDSO at different flow rates. The QCM based sensors responses were found to be linearly correlated with the concentration of VOCs vapor. It was shown that it is possible to tune the chemical affinity of the sensor by changing the HMDSO flow rate. Contact angle measurements, Fourier transform infrared spectroscopy and scanning electron microscopy were used to study surface wettability, chemical composition and surface morphology of the coated QCM electrodes.

Abstract: SiOF like films have been elaborated in microwave excited DECR plasma reactor (Distributed Electron Cyclotron Resonance) from a mixture of oxygen-hexamethyldisiloxane (HMDSO/O2) and CF4. The fluorine contents in the precursor mixture were adjusted by varying the CF4 gas flow ratio in the range of 10% - 70%. Optical emission spectroscopy (OES) and Fourier transform infrared (FTIR) have been used for the plasma diagnostic and the deposited films structure analysis, respectively. Actinometric technique was used to find trends in the concentrations of species present in the plasma. A large number of species have been detected, such as F, Si, O, C and H. Depending on the gas mixture composition, FTIR spectra revealed the presence of several chemical bonds such as Si-F and Si-O.

Abstract: Humidity sensors are widely used in industry production, process control, environment monitoring, medical and electrical applications. In this study, water molecule sensitive layers have been elaborated by plasma enhanced chemical vapor deposition PECVD technique, from a mixture of hexamethyldisiloxane (HMDSO) and oxygen (O2) in different proportions. The films were deposited on a comb-shape aluminum electrode evaporated on glass substrate. Electrical and structural characteristics of the elaborated humidity sensors were evaluated by humidity-impedance characteristics, infrared spectroscopy FTIR and ellipsometric analysis. Electrical analysis showed that the elaborated humidity sensor exhibited a detectable response to relative humidity ranging from 35 to 95%. However, increasing O2 concentration in the mixture during deposition, leads to a significant decrease of the sensor sensibility. A sensor elaborated with pure vapor of HMDSO exhibited a better sensibility. FTIR analysis revealed that increasing O2 concentration induces a decrease of methyl groups CH3 and the formation of Si-O groups leading to film densification. Besides, the values of the refractive index deduced from ellipsometric data indicated that the refractive index increases with increasing the O2% in the mixture. This observation may be considered as further evidence to film densification.

Abstract: Thin SiOF films were elaborated in microwave excited DECR plasma reactor (Distributed Electron Cyclotron Resonance) from a mixture of hexamethyldisiloxane (HMDSO) and oxygen (O2) (in 1: 9 proportion) with the presence of various CF4 concentrations. The fluorine contents in the films composition were adjusted by the CF4 gas flow ratio (in the range of 10 - 70%). The refractive index and the deposition rate were estimated from ellipsometric data and the film chemical structure was studied by FTIR analysis technique. The deposition rate increases with increasing CF4 flow and then decreases after reaching a maximum value for 20% of CF4. The decrease in the deposition rate may be attributed to the etching effect by CF4 plasma during the deposition process. As the additive fluorine concentration increases, the intensity of Si–F peak stretching vibrations located at 930 cm-1 increases and the frequency of the Si–O stretching vibration mode centered at 1060 cm-1 shifts towards higher wavenumber.

Abstract: After reviewing most of the recent developments performed on hybrid processes, basic physical phenomena of PVD-PECVD processes are detailed with the help of a model showing the different influences of main process parameters. Ti-Si-O and Zn-Si-O thin films are synthesized as possible examples of composite thin films. Limitations of the model developed are also discussed with respect to the composition and structure of deposited thin films.

Abstract: Silicon oxide deposition on fine alumina powders by plasma-enhanced chemical vapor deposition (PECVD) at atmospheric pressure was carried out in a circulating fluidized bed reactor. To deposit silicon oxide on alumina powders, the organo-silicon source precursors (tetraethoxysilane (TEOS) and hexamethyldisiloxane (HMDSO)) and oxygen were used as the reactant gases while helium and argon were used as the dilute gases. The surface property of plasma-treated alumina powder varies from hydrophobic to hydrophilic in the surface composition with variation of the discharge power. In oxygen-containing atmospheres, chemical composition of the deposited film is more inorganic with increasing the discharge power and the flow ratio of O2/precursor for both organo-silicon precursors.