CIP (cleaning-in-place) stability of AlGaN/GaN pH sensors.

The CIP stability of pH sensitive ion-sensitive field-effect transistors based on AlGaN/GaN heterostructures was investigated. For epitaxial AlGaN/GaN films with high structural quality, CIP tests did not degrade the sensor surface and pH sensitivities of 55-58 mV/pH were achieved. Several different passivation schemes based on SiO(x), SiN(x), AlN, and nanocrystalline diamond were compared with special attention given to compatibility to standard microelectronic device technologies as well as biocompatibility of the passivation films. The CIP stability was evaluated with a main focus on the morphological stability. All stacks containing a SiO2 or an AlN layer were etched by the NaOH solution in the CIP process. Reliable passivations withstanding the NaOH solution were provided by stacks of ICP-CVD grown and sputtered SiN(x) as well as diamond reinforced passivations. Drift levels about 0.001 pH/h and stable sensitivity over several CIP cycles were achieved for optimized sensor structures.

Piezoelectric actuated micro-resonators based on the growth of diamond on aluminum nitride thin films.

Unimorph heterostructures based on piezoelectric aluminum nitride (AlN) and diamond thin films are highly desirable for applications in micro- and nanoelectromechanical systems. In this paper, we present a new approach to combine thin conductive boron-doped as well as insulating nanocrystalline diamond (NCD) with sputtered AlN films without the need for any buffer layers between AlN and NCD or polishing steps. The zeta potentials of differently treated nanodiamond (ND) particles in aqueous colloids are adjusted to the zeta potential of AlN in water. Thereby, the nucleation density for the initial growth of diamond on AlN can be varied from very low (10(8) cm(-2)), in the case of hydrogen-treated ND seeding particles, to very high values of 10(11) cm(-2) for oxidized ND particles. Our approach yielding high nucleation densities allows the growth of very thin NCD films on AlN with thicknesses as low as 40 nm for applications such as microelectromechanical beam resonators. Fabricated piezo-actuated micro-resonators exhibit enhanced mechanical properties due to the incorporation of boron-doped NCD films. Highly boron-doped NCD thin films which replace the metal top electrode offer Young's moduli of more than 1000 GPa.

Sapphire-GaN-based planar integrated free-space optical system.

We report on the design and fabrication of a planar integrated free-space optical system working on the basis of binary phase diffractive optical elements (DOEs) realized in GaN on a sapphire substrate. Group III-nitride/sapphire substrates enable the parallel monolithic integration of passive microoptical elements like lenses and gratings as demonstrated here and optoelectronic devices like light emitters and photodetectors on a single wafer. We present an approach for the simultaneous optimization of the efficiency of transmissive and reflective diffractive optical elements processed in a single lithographic etching step.

N-Methylmorpholine-N-oxide ring cleavage registration by ESR under heating conditions of the Lyocell process.

Thermal cleavage processes of N-methylmorpholine-N-oxide monohydrate (NMMO) were observed in pure NMMO as well as in cellulose/NMMO solutions by ESR at temperatures of the industrial Lyocell process ( approximately 370K). Generated radicals were attributed to the alkylnitroxyl type radicals -CH(2)-NO-CH(3) in NMMO and additional (and dominated) -CH(2)-NO-CH(2)- in cellulose/NMMO solutions. Formation of both radical types formed due to NMMO ring scission is suggested.

Analysis of nanocrystalline films on rough substrates.

In this work, we propose a method to estimate basic parameters like the rms roughness and the mean grain size of nanocrystalline thin films on rough substrates. The method is based on the analysis of the power spectral density (PSD) of the surface profile, which allows distinguishing between the two participating components from surface and film. The effectiveness will be demonstrated for thin NiO(x) layers for gas sensing on Al(2)O(3) ceramic substrates, and for protective WC coatings on steel.

Using defined structures on very thin foils for characterizing AFM tips.

Knowledge of tip geometry is necessary for reproducible atomic force microscope (AFM) measurements. This is particularly important for measurements in contact mode, in which a certain wear of the tip will always occur. For small or flat structures or for structures of larger dimensions, knowledge of the tip radius and the entire tip geometry is important. Additionally, the tilt of the tip in relation to the sample is of importance. Normally, very complicated lithographically manufactured structures for tip characterization are used. In contrast, the structures shown in this work are very simple. For measuring the tip geometry very thin foils patterned by focused ion beam (FIB) were used. In this work we demonstrate the possibility of determining the AFM tip geometry and the tilt based on several different large structures. A proven algorithm was developed for the reconstruction of the tips. The shape of FIB-structured foils was determined by electron microscopy prior to AFM measurements. This new method for determining tip shape is also presented as it compares to other current methods. In this case a discussion on the stability and advantages of the new method is presented.