ICMCTF2012 Session PD-1: Post Deadline Discoveries and Innovations

Thanks to the latest development of ultra compact and reliable microwave ion sources^1,2 it is now possible to build an ion beam sputterring system composed of an arbitrary large number of simple ion sources that can be individually tuned. With this new concept of Multi Beam Sputtering (MBS) device, new possibilities are conceivable for the Ion Beam Sputtering (IBS) technology^3,4, especially for thin film deposition on large size substrates with high uniformity. With MBS, the deposition profile is not defined by the shape and the tuning of a unique large beam, but by the sum of the contributions of a great number of small, well controlled in size, sputterring spots. The uniformity is the consequence of the geometric sum of all sputterring lobes obtained by each sputtering spot. The ion sources units can be distributed along a circle or a line and each ion beam delivered by an ion source impinges its own target. An individual source of a typical size 3x3x3 cm uses a few watts of microwave power for producing a beam up to 1 mA with energy in the range of 5 to 15 keV. The first operational device, MBS-20, uses 20 of such ion sources distributed on a circle around a 70 mm diameter multi-target holder allowing thin film deposition on 100 to 300 mm diameter substrates with deposition rates in the range of 0 to 1 µm/h. An important point, since each ion source uses an individual target, is that co-evaporation of several components can be done simultaneously. By the way, the deposition of alloys with a controlled stoechiometry is easier than with any other method and without uniformity loss. We will show preliminary results for Cu, Ta, Ta₂O₅, C, Si0₂, Ti, TiN, TiO2, TiAlN and Th on 100 or 200 mm glass substrate diameters, Mylar 0.5 µm or Si substrates. All these processes can be done with reactive atmosphere allowing oxide or nitride deposition.

¹P. Sortais, T. Lamy, J. Médard, J. Angot, L. Latrasse, and T. Thuillier, Rev. Sci. Instrum. 81 (2010) 02B31

²P. Sortais, T. Lamy, J. Médard, J. Angot, P. Sudraud et al., Rev. Sci. Instrum. 83, 02B912 (2012

³Patent pending N° 1150981.

⁴Under Grant Grenoble Alpes Valorisation Innovation Technologies (GRAVIT) 080606, may 2009.

Molecular dynamics simulation of the nanoindentation was used to investigate mechanical properties of single layer silicon carbide coatings on silicon substrates. Indenter load-penetration depth relation was determined and put into relation to the internal coating structure and the substrate behavior. In order to reach this objective, an indenter tip in the form of a Berkovich indenter was introduced, a discrete indenter motion of 0.2 Å was imposed. For the modeling of the Si-C system, well known bond-order Tersoff potential was used, while the substrate-indenter interaction was modeled by a self-developed short range repulsive pair potential. From the indenter load-penetration depth relation, mechanical values of hardness and Young modulus for the coatings could be obtained. Hardness values determined by molecular dynamics simulations were in the range between 26.4 GPa and 34.4 GPa. These results are in good agreement with experimental measurements using UMIS 2000 system delivering values between 20.1 GPa and 35 GPa in dependence of the micro structure of the coating, the deposition temperature and maximum indentation depth.

The first use of mesoporous TiO₂ beads in plastic substrate flexible dye-sensitized solar cell (FDSC) is demonstrated. Pure anatase TiO₂ beads with various sizes (250 to 750 nm) and characteristics are obtained using a modified and efficient two-step method. The concept of chemical sintering, eliminating the step of additive removal, is used to prepare bead-containing paste for room temperature fabrication of photoanode having good adhesion to the substrate. The obtained photoanodes are examined for their dye loadings and light absorbance properties. Various plastic substrate FDSCs having commercial P25- and bead-containing photoanodes are fabricated and evaluated. The resulting cells are evaluated for the J-V characteristics, electron diffusion time, electron lifetime, charge-collection efficiency, electron-injection efficiency and incident photon-to-electron conversion efficiency. The bead-only cells not only have better efficiencies, as high as ~5%, but also exhibit ultra-fast electron diffusion rates, less than 1 ms. The best efficiency and electron diffusion rates are respectively 15% higher and two-order of magnitude faster than the P25-only cell. The effects of the bead characteristics on the cell performance is presented and discussed.