Polydimethylsiloxane (PDMS) is a promising biomaterial for generating artificial extracellular matrix (ECM) like patterned topographies, yet its hydrophobic nature limits its applicability to cell-based approaches. Although plasma treatment can enhance the wettability of PDMS, the surface is known to recover its hydrophobicity within a few hours after exposure to air. To investigate the capability of a novel PDMS-type (X-PDMS) for in vitro based assessment of physiological cell properties, we designed and fabricated plane as well as nano- and micrometer-scaled pillar-patterned growth substrates using the elastomer types S-, H- and X-PDMS, which were fabricated from commercially available components. Most importantly, we compared X-PDMS based growth substrates which have not yet been investigated in this context with H- as well as well-known S-PDMS based substrates. Due to its applicability to fabricating nanometer-sized topographic features with high accuracy and pattern fidelity, this material may be of high relevance for specific biomedical applications. To assess their applicability to cell-based approaches, we characterized the generated surfaces using water contact angle (WCA) measurement and atomic force microscopy (AFM) as indicators of wettability and roughness, respectively. We further assessed cell number, cell area and cellular elongation as indirect measures of cellular viability and adhesion by image cytometry and phenotypic profiling, respectively, using Calcein and Hoechst 33342 stained human foreskin fibroblasts as a model system. We show for the first time that different PDMS types are differently sensitive to plasma treatment. We further demonstrate that surface hydrophobicity changes along with changing height of the pillar-structures. Our data indicate that plane and structured X-PDMS shows cytocompatibility and adhesive properties comparable to the previously described elastomer types S- and H-PDMS. We conclude that nanometer-sized structuring of X-PDMS may serve as a powerful method for altering surface properties toward production of biomedical devices for cell-based applications.

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In this work, hafnium silicate layers on Si and Ge wafers for gate dielectric application in metal-oxide-semiconductor devices are investigated. Films are deposited by metal-organic (MO)CVD using the single-source precursor Hf(acac) 2 (OSi t BuMe 2 ) 2 .This precursor exhibits good properties in terms of hydrolysis stability, volatility, and deposition. However, precursor decomposition is affected by surface conditions. Films deposited on Si wafers reveal high C contamination (up to 20 at %) and low Si content (up to 20 at %). In contrast, for film deposition on Ge wafers, no C contamination can be detected and Si incorporation is delayed until after about 15 nm HfO 2 dielectric growth. Post-deposition rapid thermal annealing in an O 2 atmosphere causes crystallization of deposited films, Si and Ge redistribution in the dielectric, respectively, and interfacial layer growth. However, oxygen annealing was also found to reduce effective oxide thickness (EOT) significantly compared to as-deposited films, which is attributed to crystallization effects. However, scaling of EOT is limited by that interfacial layer growth. Leakage currents are mainly caused by trap-related conduction mechanisms. Energy levels of involved traps decrease with increasing crystallization and/or Hf content, and values of 0.5 eV and 1 eV related to Hf and Si bonds, respectively, are obtained.

The influence of photoresist pattern on charging damage of gate oxides during high current arsenic implantation is studied. Metal-oxide- semiconductor (MOS) capacitors of 10 mu m/sup 2/ active area and 4.5 nm oxide thickness connected with various types of poly antennas and resist patterns on top were processed, whereby the resist overlapped and/or enclosed the gate electrode during ion implantation. The evaluation of the devices was performed by leakage current and charge to breakdown (Qbd) measurements. The influence of resist size, perimeter, and coverage of polyelectrodes is described in detail

In this study, we show the design and manufacturing of microfluidic deterministic lateral displacement (DLD) devices for sub-micrometer particle separation. For that purpose, devices with pillar gaps of 4 µm and a periodicity of 50 were designed. After photolithographic manufacturing of SU-8 masters with different heights (15 and 30 µm) and vertical sidewalls for soft-lithographic replication with polydimethylsiloxane (PDMS) the influence of flow rate on the separation efficiency of 0.45 and 0.97 µm particles was investigated. The 15 µm devices were operated at 0.125 and 0.5 µl/min sample flow rate and the 30 µm devices at 0.5 and 2.0 µl/min, respectively. Excellent separation efficiencies were observed for both device heights at the lower sample flow rates, while separation efficiencies decreased at the respective higher sample flow rates. The decrease in separation efficiency was attributed to deformation of the soft PDMS pillars, which causes an increase in pillar gaps at the higher sample flow rates as shown by microscopy imaging. The advantage of the 30 µm devices over the 15 µm devices is clearly shown by the separation of 0.45 and 0.97 µm particles at 0.5 µl/min. Due to reduced hydrodynamic resistance in the 30 µm devices and thus less pillar deformation, the displacement efficiency of 0.97 µm particles was above 99% compared to 46–57% for the 15 µm devices. Our 30 µm devices demonstrated excellent separation at a tenfold higher sample flow rate with 0.5 µl/min compared to comparable PDMS-based devices operating in the same size regime.