Condensation and solid phase reactions of Fe in Mg silicate systems

Transcription

1 Condensation and solid phase reactions of Fe in Mg silicate systems S. Wetzel1 1 Kirchhoff 2 Institut A. Tamanai1 H.-P. Gail2 A. Pucci1 Institut fu r Physik, Universita t Heidelberg fu r theoretische Astrophysik, Universita t Heidelberg 09. November 2011

2 Outline Introduction Measurement technique and Experimental setup Results Summary & Outlook 2 / 20

3 Introduction Introduction R. van Boekel et. al., Nature, 2004 IRAS Fried Egg Nebula, This is a post-red Supergiant star. The emission spectrum was obtaines at VLT (ESO) in Chile (provided by H.-P. Gail) Silicates are among the most abundant minerals 10µm feature Crystallinity, material composition, shape, formation conditions 3 / 20

4 Introduction What we can study in our lab Evaporation Condensation Annealing Knudsen method vapour pressure evaporation coefficients gas phase components optical properties (dielectric function) condensing material Infrared spectroscopy time scale typical energies typical temperatures Input for: chemical disc models, fit of observations, composition of the disc,. 4 / 20

5 Measurement technique and Experimental setup Measurement technique and Experimental setup Introduction Measurement technique and Experimental setup Results Summary & Outlook 5 / 20

6 Measurement technique and Experimental setup In situ IR spectroscopy 6 / 20

7 Measurement technique and Experimental setup Experimental setup 7 / 20

8 Results Results Introduction Measurement technique and Experimental setup Results Summary & Outlook 8 / 20

9 Results Studies on SiO and SiO 2 evaporation 1, c m c m 0 n m -1 1,0 0 0 n m c m c m -1 re l. tra n s m itta n c e a ) 0,9 5 0,9 0 0,8 5 S io e v a p o ra tio n S io 2 e v a p o ra tio n 9 0 n m w a v e n u m b e rs [c m -1 ] re l. tra n s m itta n c e re l. re fle c ta n c e 0,9 8 0,9 6 0,9 4 0,9 2 re l. tra n s m itta n c e S io e v a p o ra tio n S io 2 e v a p o ra tio n n m b ) w a v e n u m b e rs [c m ] Klevenz et al. Appl. Spectrosc., 64(3) (2010) (left) Klevenz et al. Phys. Status Solidi B, 247(9), (2010) (right) 9 / 20

10 Results Varying substrate temperature: SiO on Si(111) rel. transmittance a) cm nm -233 C cm cm cm cm nm 47 nm -180 C 30 C 100 C 47 nm 200 C 48 nm wavelength [ m] [cm -1 ] b) peak position temperature [K] [ m] Disproportionation proccesses Already at room temperature? Influence for very low temperatures unclear 10 / 20

11 Results Single layers of Fe, Mg, and SiO 10µm feature of the SiO stretching vibration (left) Island growth, percolation and Drude-like behaviour of metal 11 / 20

12 Results Modelling of Spectra - SiO and Fe Brendel dielectric function for Si-O vibration (Klevenz et al. 2010) Drude-model for metal films (beyond percolation) 12 / 20

13 Results Multilayers - Fe, Mg on SiO Additional feature around 10µm from Fano-type interaction of plasmonic excitation of the metal film with SiO phononic excitation: lineshape is asymmetric, intensity depends on film morphology 13 / 20

14 Results Fano-type interaction Scattering cross section (after U. Fano) σ = (ɛ+q) ɛ 2 +1 Phenomelogical asymmetry parameter q From A. E. Miroshnichenko et al. Reviews of Modern Physics 82, 2257 (2010) 14 / 20

15 Results Plasmonic interaction with surface polaritons F. Neubrech et. al., J, Phys. Chem C, 114, 7299 (2010) Enhanced Fano-type signal in surface polariton region of Si-O stretching vibration of SiO 2. Position different to finding with Fe islands Detailed analysis in progress 15 / 20

16 Results Coevaporation - Mg and SiO Redshift of the Si-O stretching vibration (from 10µm to 11µm) and broadening are confirmed. Metal itself seems to be invisible. 16 / 20

17 Summary & Outlook Summary & Outlook Introduction Measurement technique and Experimental setup Results Summary & Outlook 17 / 20

18 Summary & Outlook Summary In situ IR spectroscopy during film growth under UHV conditions Optical properties from transmittance measurements Influence of substrate temperature and interface effects Triple evaporator: Single layer, Multilayer & Coevaporation experiments possible Single layer: Mg, Fe and SiO show IR spectra in accordance to literature data Mulltilayer: Fano-type interaction of metal island films with Si-O stretching vibration, at higher coverages conducting layers are formed Coevaporation: Significant redshift of the resonance and a broadening has been observed 18 / 20

19 Summary & Outlook Outlook Detailed data analysis in progress Continue Multilayer & Coevaporation experiments for Fe and SiO with special attention to the influence of Fe on the 10µm feature. Surface analysis by means of SEM & EDX in cooperation with partners Annealing experiments with layers produced by subsequent or simultaneous evaporation of Fe, SiO, Mg (MgO) Annealing experiments with amorphous silicate layers with varying Fe content produced by cooperation partners Implementation of results into theoretical models by H.-P. Gail 19 / 20

20 e st Acknowledgement Summary & Outlook Thank you for your attention. t s ir F 1 0 Million Years of the So SPP 1385 la r S y h T - a P l a n e ta r y M a te DFG r ia ls A p r p o a c h e m - Financial support by Prof. Tetsuo Yamamoto - Hokkaido University SPP The first 10 Million years of the Solar system Reserach Group FOR759 - Planet formation 20 / 20