Search

We report on the fabrication and characterization of Si/SiO 2 Fabry-Perot microcavities. These structure are used to enhance the external quantum emission along the cavity axis and the spectral purity of emission from Rare earth doped and undoped SiOx (x ≤ 2) films that are used as active media to fabricate a Si based RCLED (Resonant Cavity Light emitting Devices). These structures are fabricated by chemical vapour deposition on a silicon substrate. The microcavities are tuned at different wavelengths: 540 nm, 980 nm, 1540 nm, 780 nm and 850 nm (characteristic emission wavelength respectively for Tb, Yb and Er and Silicon Rich Oxide (SRO)). The reflectivity of the microcavities is of 97% and the quality factor ranges from 50 (for the cavity tuned at 540nm) to 95 (for the cavities tuned at 980 nm and 1540 nm) and 150 (for the cavity tuned at 780 nm and 850 nm). These cavities have been characterized by TEM analysis to evaluate film uniformity, thickness and densification after annealing process for temperature ranging from 800° to 1100°C. The reflectivity and photoluminescence spectra show resonant wavelengths in agreement with the calculated values. A new structure to electrically pump the active media has been designed. The electrical properties of the active media have been analysed. An enhancement of the photoluminescence signal of twenty times have been achieved for the selected emission wavelength.

The increasing interest for light and movable electronic systems, cell phones and small digital devices, drives the technological research toward integrated regenerating power sources with small dimensions and great autonomy. Conventional batteries are already unable to deliver power in more and more shrunk volumes maintaining the requirements of long duration and lightweight. A possible solution to overcome these limits is the use of miniaturized fuel cell. The fuel cell offers a greater gravimetric energy density compared to conventional batteries. The micromachining technology of silicon is an important tool to reduce the fuel cell structure to micrometer sizes. The use of silicon also gives the opportunity to integrate the power source and the electronic circuits controlling the fuel cell on the same structure. This paper reports preliminary results concerning the micromachining procedure to fabricate an arrays of microchannels for a Si-based electrocatalytic membrane for miniaturized Si-based proton exchange membrane fuel cells. Several techniques are routinely used to fabricate arrays of microchannels embedded in crystalline silicon. In this paper we present an innovative microchannel formation process, entirely based on surface silicon micromachining, which allows us to produce rhomboidal microchannels embedded on (100) silicon wafers. Compared to the traditional techniques, the proposed process is extremely compatible with the standard microelectronics silicon technology. The kinetics of rhomboidal microchannel formation is monitored by cyclic voltammetry measurements and the results are compared with a detailed structural characterisation performed by scanning electron microscopy. The effectiveness of this process is discussed in view of the possible applications in the fuel cell application.