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We have applied real time spectroscopie ellipsometry (RTSE) to monitor the successive growth of p-type a-Si1-xCx:H and i-type a-Si:H on specular SnO2:F (i.e., the superstrate solar cell configuration) in a single-chamber deposition system. Both the microstructural evolution, which includes the surface roughness and bulk layer thicknesses versus time and bulk layer void volume fraction, as well as the optical properties, which include the dielectric function (1.5–4.0 eV) and optical gap of the individual layers, were determined from RTSE data collected during growth. The accuracy of our approach is demonstrated by correlating structural parameters obtained both by RTSE and atomic force microscopy. Based on prior information deduced by RTSE, the TCO/p/i structure was fabricated with optimized procedures that have sought to minimize TCO/'p and p/i interfacial problems. These studies illustrate that RTSE can be a valuable tool for identifying problems in the fabrication of a-Si:H solar cells and ultimately improving cell performance.

Incorporation of ferroelectric thin films into integrated microelectronics requires deposition temperatures compatible with back-end processing. Pb(Zr,Ti)O3 (PZT) thin films have been deposited at low temperatures by a thermal chemical vapor deposition process using flash-vaporized metalorganic precursors. Deposition temperatures, A-site to B-site ratios in the precursor solution, and bottom electrodes have been surveyed. Stoichiometric perovskite films with (Zr/Ti) ratios ranging from 20/80 to 50/50 were obtained. Films deposited at temperatures below 500°C possess very fine grain structures. Capacitor structures were fabricated by depositing top electrodes using electron-beam evaporation, followed in some cases by a post-electrode anneal at 650°C. Remanent polarizations greater than 20 μC/cm2 were observed on films deposited on Pt at temperatures as low as 475°C. Perovskite films were obtained on Ir electrodes at temperatures as low as 450°C, with remanent polarization greater than 10μC/cm2 in the as-deposited condition.

Chemical sensors based on a microhotplate platform generally function via a conductometric or calorimetric transduction mechanism. In addition to these mechanisms, a mechanical transduction mechanism is proposed based on the detection of the microhotplate bending due to volume change of functional layers. In this letter, we demonstrate sensing of gaseous hydrogen based on volumetric expansion of Pd∕Y functional layers. In this case, the embedded polysilicon heater element also serves as the piezoresistive strain-detecting element, changing its resistance as the microhotplate bends. This transduction mechanism can be used independently of, or in conjunction with, a simultaneous conductometric or calorimetric mechanism.