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Nanocrystalline diamond films have been grown in a hot filament CVD (HFCVD) system allowing BEN, textured growth and HOD growth of diamond on 4″ silicon (100). The growth process of nanocrystalline diamond discussed here consists of a BEN process for diamond nucleation on silicon, with a density of more than 10 10 cm -2 across the entire wafer surface. The subsequent growth of the nanocrystalline diamond films is achieved by addition of nitrogen into the gas phase with a relative concentration to carbon of 1 : 1.At substrate temperatures between 680 °C and 740 °C, closed diamond films are grown with thicknesses between 1 µm and 20 µm. At low nitrogen concentrations the nanocrystalline diamond films exhibit still a columnar structure with a lateral grain size below 200 nm whereas the vertical grain size can reach several microns. Higher nitrogen concentrations lead to a nanocrystalline diamond growth mode with no columnar structure and a grain size is no longer detectable by SEM.The advantages of diamond in MEMS technology rely on its outstanding mechanical and thermal properties. Additionally, the stress distribution inside the diamond films due to thermal expansion as well as the polycrystalline nature of the film has to be taken into account.Applying different test structures we could measure fracture strength of more than 4.0 GPa and elasticity moduli of up to 1020 GPa for these nanocrystalline films. The intrinsic vertical and horizontal stress remains in most cases below the detection limit of 5 MPa, so that freestanding structures with a length of several millimeters can be fabricated without noticeable bending.

Organic silicone compounds, used in a wide range of household and commercial products, ultimately make their way into landfills and wastewater treatment facilities. Many of these compounds are volatilized into the methane-rich biogas produced by landfills and anaerobic digesters of wastewater treatment plants. The biogas, a valuable source of renewable energy, can be collected and used as a fuel for combustion engines. During combustion, volatile silicon compounds (VSiCs), including siloxanes, are converted into silica particles that can coat surfaces, mask catalyst pores, cause abrasion damage and increase maintenance costs. Scrubbers used to control VSiC levels in the biogas must be evaluated regularly, so a variety of sample collection and quantification methods have been investigated. There is also interest in quantifying siloxanes in air and gas streams that are regulated for photochemical smog precursors. Fully methylated siloxanes are exempt from the photochemically reactive volatile organic compound (VOC) compound list but are measured using standard methods for the analysis of non-methane non-ethane organic compounds (NMNEOCs). Accurately quantifying NMNEOCs without including the VOC-exempt fully methylated siloxanes requires an accurate and sensitive method for VSiC analysis. This paper describes a method of analysis for VSiCs that allows the use of a sample preconcentration system with gas chromatography/mass spectrometry (GC-MS). This method can detect low concentrations of VSiCs, including eight relevant fully methylated siloxanes, in biogas. We are also developing a method for the use of a gas chromatograph/inductively coupled plasma/mass spectrometer (GC-ICP-MS) to speciate VSiCs and quantify the silicon levels of each compound, as well as total silicon concentration in the sample.