J. Podlecki

X-ray diffraction studies of electrostatic sprayed SnO2: F films

Fluorine-doped tin oxide films were deposited by electrostatic spray pyrolysis technique (ESP), on 1cmx1cm Corning 7059 substrates. The structural and electrical properties of the deposited films with different doping levels are studied. Relative variations in the structural properties were explained on the basis of structural factor calculations. The results show that the incorporation of fluorine atoms took place only at substitutional sites leading to an increase in free carrier concentration.

MEMS Scanning Calorimeter With Serpentine-Shaped Platinum Resistors for Characterizations of Microsamples

We report a new design and operation of a microelectromechanical systems (MEMS) differential scanning calorimeter (DSC) for heat-capacity measurements. The sensor consists of a 500-nm silicon nitride membrane supported by four bridges on a silicon wafer. On one side of the membrane, a serpentine-shaped platinum layer is deposited and used as both a resistive heater and a thermometer during the DSC measurement. This MEMS design can provide a self-alignment between the DSC cell and the material to be analyzed in order to prevent its deposition on the sloping side walls of the silicon frame. According to FEM calculations, the system exhibits good thermal isolation and high uniformities in the temperature field in the sensing area of the device. To evaluate the use of this calorimetric device for liquid samples, we measure the heat of vaporization of nanoliter-scale water droplets with high preciseness using the calorimeter in both scanning and heat conduction modes.

Characterization of LiTaO3 thin films fabricated by sol-gel technique

Lithium tantalite (LiTaO3) thin films have been fabricated by sol-gel technique and crystallized by RTA process. The effect of heating temperature on the structural properties of LiTaO3 is investigated. The thin films are characterized by means of X-ray diffraction, Raman spectroscopy and thermal analysis (DCA/DTA). After the optimization of the growth parameters of LiTaO3 prepared by sol-gel processing, the pyroelectric property of LiTaO3 thin films deposited on Si (100) substrates have been also investigated.

Hyper frequency modeling of resonated systems based on piezoelectric LiTaO 3 thin layers

In this work, we discuss the piezoelectric activity of lithium tantalite (LiTaO3) thin layers and to more understand this phenomenon we have developed a model for our LiTaO3 resonators based on mason model and simulated the hyper frequency behavior. Our LiTaO3 resonators are made from three layers staked on silicon substrates. The aluminum thin film constitutes the external electrode, the platinum forms the internal electrode and the lithium tantalite constitutes the piezoelectric layer. Each element of these layers is represented by an arrangement of impedances. The simulation shows the reflection coefficient, ρ, as a function of the frequency. We observe a resonant frequency that decreases with the increase of the thickness of the piezoelectric LiTaO3 layers. A slight variation of this resonant frequency is obtained when comparing it with that of the uncharged piezoelectric device, which is due to the different layers loading the system. Over oscillations superposing to the envelope are observed and found to be related to the propagation of the acoustic wave in the silicon substrate. From these over oscillations one can see that this system can be used as an efficient method to calculate the thickness of any substrate.