Dieter Schmeißer

We report on the electrospinning of poly(vinylidene fluoride–hexafluoropropylene) [P(VDF–HFP)] nanofibers doped with silver nanoparticles for the preparation of a polymer based nanogenerator (PNG). It has been found that the yield of the piezoelectric phase is increased by the addition of silver nanoparticles. Furthermore, defects in the P(VDF–HFP) electrospun fibers are removed resulting in a significant enhancement in the output power of the PNG. A maximum generated PNG output voltage of 3 V with a current density of 0.9 μA cm⁻² is achieved.

With photoelectron spectroscopy, we study the interface chemistry of the copolymer poly(vinylidene fluoride trifluoroethylene) (P(VDF-TrFE)) and different electrode materials. We compare the interfaces aluminum/P(VDF-TrFE) and PEDOT:PSS/P(VDF-TrFE). PEDOT:PSS is a conductive polymer (Poly(3,4-ethylenedioxythiophene): poly(styrenesulfonate)). The data sug-gest that we have an interface layer for electrodes, made of aluminum. An interface reaction occurs in both cases: for aluminum as top and as bottom electrode. In contrast, the organic PE-DOT:PSS electrode shows no chemical interaction with the P(VDF-TrFE) polymer. The much lower reactivity of organic electrodes, compared to aluminum, gives a direct hint to im-proved functional properties of thin organic ferroelectric films.

We investigate the dielectric properties of Praseodymium based oxides and silicates by preparing MIS structures consisting of a metal layer (M), PrO_X (praseodymium oxide) as a high-k insulating layer (I), and silicon (Si) or silicon carbide (SiC) as semiconductor substrates (S).The use of a buffer layer between PrO_X and SiC is necessary as we found destructive interactions like silicate and graphite formation between these materials. Based on a higher permittivity value than SiO₂ and a good lattice matching in conjunction with nearly the same thermal expansion coefficient to SiC, we focus on aluminum oxynitride (AlON) as a suitable buffer layer for this high-k/wide-bandgap system. We report on results achieved by Synchrotron Radiation Photoemission Spectroscopy (SRPES) and by electrical measurements.In our spectroscopic investigations we found a stable AlON/3C-SiC interface as well as no elemental carbon and silicate contributions in the core levels after thin PrO_X deposition and annealing up to 900°C.In electrical characterizations of PrO_X/AlON stacks on silicon we already found a strong improvement in the leakage current down to values of 10^-7 A/cm² at an CET of 4nm. We observed an interface state density in the range of 5x10¹¹-1x10¹²/eVcm² and 1-5x10¹²/eVcm² on Si and SiC, respectively.

The use of low dielectric constant materials in the on-chip interconnect process reduces interconnect delay, power dissipation and crosstalk noise. To achieve the requirements of the ITRS for 2007-2009 minimal sidewall damage from etch, ash or cleans is required. In chemical vapor deposited (CVD) organo-silicate glass (OSG) which are used as intermetal dielectric (IMD) materials the substitution of oxygen in SiO² by methyl groups (-CH₃) reduces the permit-tivity significantly (from 4.0 in SiO² to 2.6-3.3 in the OSG), since the electronic polarizability is lower for Si-C bonds than for Si-O bonds.However, plasma processing for resist stripping, trench etching and post-etch cleaning removes C and H containing molecular groups from the near-surface layer of OSG. Therefore, compositional analysis and chemical bonding characterization of structured IMD films with nanometer resolution is necessary for process optimization.OSG thin films as-deposited and after plasma treatment are studied using X-ray absorp-tion spectroscopy (XAS) and electron energy loss spectroscopy (EELS). In both techniques, the fine structure near the C1s absorption or energy loss edge, respectively, allows to identify C-H, C-C, and C-O bonds. This gives the opportunity to differentiate between individual low-k mate-rials and their modifications. The O1s signal is less selective to individual bonds. XAS spectra have been recorded for non-patterned films and EELS spectra for patterned structures. The chemical bonding is compared for as-deposited and plasma-treated low-k materials. The Fluo-rescence Yield (FY) and the Total Electron Yield (TEY) recorded while XAS measurement are compared. Examination of the C 1s near-edge structures reveal a modified bonding of the re-maining C atoms in the plasma-treated sample regions.