Microstructure and Surface Morphology of Ag and Au Films Grown on Hydrogen-Terminated Si(111) Substrates
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growth of Cu and Ag on hydrogen terminated Si(100) and Si(1 11) surfaces [6,7]. HREM
and RHEED studies on Cu/Si(100) revealed the formation of an interfacial Cu silicide
region during deposition. This Cu silicide layer appears to aid in proper lattice matching for the growth of Cu(100) lattice rotated 450 with respect to Si lattice. For Cu deposited on Si(1 11), no significant interdiffusion region was detected. However, only epitaxial Cu crystallites with distinct orientational variants were observed [6]. RHEED and XRD studies on Ag/Si(l1l) indicated a Ag growth with [011] Ag II [011] Si both at room temperature and at 275 0 C. Scanning electron microscopy studies showed islands (- 3000 A) separated by canal like structures for films grown at 275 0 C. Such features were not observed for films grown at room temperature and then annealed at 275 0 C for 15 minutes [7]. In the present study we have employed HREM to examine Ag and Au films grown on hydrogen terminated Si(1 11) substrates at room temperature by molecular beam epitaxy (MBE). The films were annealed under ultra high vacuum conditions for 1 hour at 275 0 C for Ag/Si(l 11) and at 175 0 C for Au/Si(1 11). RHEED was used to monitor in situ the growth of the films. AFM was used to examine surface morphology of the films before and after annealing. Differences in the growth of Ag and Au on Si(1 11) are discussed.
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Mat. Res. Soc. Symp. Proc. Vol. 355 ©1995 Materials Research Society
Experimental The films were grown under ultra high vacuum using an MBE deposition system with a base pressure < 1 xl0-10 torr. The chamber is equipped with a RHEED unit (15kev) and electron beam evaporator sources with computer controlled pneumatic shutters. The rate of deposition and total thickness were measured with quartz crystal thickness monitors. The deposition rates were 0.5 - 1 A/s. During deposition the base pressure in the growth chamber was maintained < 2 xl0-9 Torr with the aid of a liquid nitrogen cryostatic shroud. Further details of the deposition system and silicon substrate preparation by HF etching are ' given elsewhere [6,7]. HREM studies were carried out using a JEOL 4000 EX HREM operating at 400
kV. Details on sample preparation and operating conditions are reported elsewhere [6]. Standard x - ray diffraction (0-20) scans and rocking curves were performed on a Rigaku powder diffractometer, using Cu Ka radiation. Samples were also analysed using a Digital Instruments Nanoscope II AFM, operating in the contact mode.
Results and Discussion RHEED patterns were monitored along the two major azimuths and of Si at various stages of the growth of Ag and Au films deposited on hydrogen terminated Si(1 11). Our previous RHEED data for Ag growth [7] demonstrated the formation of bright and distinct Ag(1 11) diffraction patterns even for a 3 A thick Ag film. The closely spaced spots on the vertical streaks observed along the Si azimuth indicated a 1800 twinning of epitaxial Ag crystallites about the Ag(l 11) plane. Upon annealing a 500 A thick film at 275 0 C for
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