We present a comprehensive study of atomic layer deposited materials for ethanol gas sensing with large-scale fabrication techniques. Ultra-thin nickel oxide and cobalt oxide films show very promising performance in ethanol sensing. The films were measured at different temperatures and humidity levels. Unlike most semiconducting metal oxides used for gas sensing, nickel and cobalt oxide are p-type materials. The reactivity and sensitivity of p-type metal oxides offer their full potential only in thin compact form, where the highly resistive bulk does not dominate the current. Atomic layer deposition is an excellent method of fabrication for ultra-thin films and offers a versatile palette of potential semiconducting metal oxides materials for more target gases.

The development of a silicon-only capacitive dew point sensor is described in this paper. The principle of operation is based on the change in capacitance of an interdigitated parallel plate capacitor due to the condensation of water below dew point temperature. The proposed sensor element is simple in fabrication, with only one lithography step and no metal or polymer usage. The experiments show good repeatability and baseline stability, whereas detection accuracy needs to be further improved. The influence of condensed water on the capacitance is investigated at different frequencies and cooling rates. It is expected that replacing air with water increases the capacitance by a factor of 80, due to the ratio of relative permittivity of water to ambient air. However, at low frequencies, the conducting properties of water in combination with the ultra-thin oxide coating on the electrodes result in a more complex capacitance behavior and an increase of up to four orders of magnitude has been measured. This additional and more rapid increase in capacitance may be utilized for faster dew point detection. In the current stage of development, the accuracy of the dew point temperature reading is equal to or better than the reference sensor (+/- 2 degrees C), with a response time of < 40 s, and is expected to be further improved with a more accurate test setup.

In this work we study a silicon parallel plate capacitor as a dew point sensor. Accumulation of water between the parallel plates below dew point temperature leads to an increase in capacitance. The expected 80-fold increase in capacitance (ratio of relative permittivity of water to air) holds true at high frequencies while at low frequencies an increase up to four orders of magnitude has been measured. We report that the condensed water models more as a conductor than as a dielectric at low frequencies, which, along with the native oxide of silicon, explains the unexpected increase in capacitance.

In this work we present migration phenomenon of throughholes in silicon membranes.The sealing of through-holes in hydrogen ambient at high temperature (1130°C) with various dimensions and annealing time durations was investigated in both singlecrystalline silicon (sc-Si) and poly-crystalline silicon (poly-Si) membranes.The sealing process in silicon was observed as highly dependent on local crystal grain geometry, leading to more distributed, unpredictable migration rates and shape evolutions in poly-Si compared to holes in sc-Si.These findings can be leveraged in fabrication processes that require a balance between silicon migration and deposition.

The invention concerns an ellipsometer comprising a source (S) supplying at least an infrared radiation, a sample-holder (PE), a sensor (D), a first optical system mounted between the source (S) and the sample-holder (PE), so as to illuminate a sample placed on the sample-holder, under oblique view with a polarised light beam and a second optical system mounted between the sample-holder (PE) and the sensor (D) for collecting the light reflected by the sample. The ellipsometer further comprises a blocking device (F2) mounted on the reflection path in the focal plane of the focusing device (M2) of the second optical system, and adapted to block parasite rays (RP) derived from the rear surface (FAR) of the sample and to allow through useful rays (RU) derived from the front surface (FAV) of the sample towards the sensor (D), thereby enabling to obtain a resolution with respect to the sample front and rear surfaces.

An ellipsometry device includes first focusing means (L1), combined with a first optical system (10), for focusing the light beam from said first optical system (10) onto the sample, second focusing means (L2), combined with a second optical system, for focusing the beam reflected by the sample surface onto the input of the second optical system, and optical correction means (PT) for correcting, together with the first and second focusing means (L1, L2), the position of the focused reflected beam so as to reject the interference reflections generated by the surface of the sample opposite the light beam receiving surface, and to obtain a maximum signal level at the photodetector (7).