Browsing by Author "Pan, SY"

Now showing 1 - 3 of 3

Atomistics of Ge deposition on Si(100) by atomic layer epitaxy
(2003-01-31)
Lin, DS
;
Wu, JL
;
Pan, SY
;
Chiang, TC
;
物理研究所
Chlorine termination of mixed Ge/Si(100) surfaces substantially enhances the contrast between Ge and Si sites in scanning tunneling microscopy observations. This finding enables a detailed investigation of the spatial distribution of Ge atoms deposited on Si(100) by atomic layer epitaxy. The results are corroborated by photoemission measurements aided by an unusually large chemical shift between Cl adsorbed on Si and Ge. Adsorbate-substrate atomic exchange during growth is shown to be important. The resulting interface is thus graded, but characterized by a very short length scale of about one monolayer.
Chlorine-induced Si surface segregation on the Ge-terminated Si/Ge(100) surface from core-level photoemission
(2001-12-15)
Lin, DS
;
Pan, SY
;
Wu, MW
;
物理研究所
;
Institute of Physics
This study investigated the thermal reactions on the Cl-terminated Si/Ge(100)-2x1 surface using synchrotron radiation photoemission spectroscopy. Populations of surface Cl-Ge and CI-Si bonds during annealing are monitored by measuring the intensities of their corresponding Ge 3d, Si 2p, and Cl 2p core-level components. Experimental results clearly demonstrate that no Si atoms are present on the surface after the deposition of 0.8 monolayer Si on the Ge(100) surface at 730 K and that CI termination pulls out the indiffused Si of about two atomic layers deep to form Cl-Si bonds upon annealing at 550-690 K. We attribute such chlorine induced Si segregation to a thermodynamic driving force that favors the CI-Si surface species. Above 680 K, chlorine is desorbed in the form of SiCl2, although the top surface layer of the starting Si/Ge(100) sample consists of Ge-Ge dimers only.
Stability and mechanism of selective etching of ultrathin Ge films on the Si(100) surface upon chlorine adsorption
(2004-01-01)
Wu, JL
;
Pan, SY
;
Lin, DS
;
物理研究所
;
Institute of Physics
This work investigates the effect of chlorine termination on the stability and the etching of ultra thin Ge layers on a Si(100) surface, using scanning tunneling microscopy (STM) and synchrotron radiation photoemission spectroscopy. The initial growth of Ge on the Si(100) surface is known to occur layer by layer. The intensities of the Ge 3d, Si 2p, and Cl 2p core levels, after the chlorine passivation of Ge/Si(100) surfaces, together with the STM images reveal that most of the deposited Ge atoms have been randomly dispersed on the surface layer during initial submonolayer growth. They occupy only similar to90% of the surface after a 2-ML (monolayer) coverage. Chlorine termination drastically alters the atomic composition of the surface (dimer) layer and in the thin films when annealing at elevated temperatures occurs. Specifically, Cl termination of the Ge/Si(100) surfaces causes Ge, which initially form Cl-Ge bonds in the surface layer, to move into the subsurface layers after annealing at 650-750 K. Silicon is extracted from the subsurface layers to form Cl-Si bonds. Above 900 K, chlorine is desorbed in the form of SiCl2, leaving the initial thin Ge films on the Si(100) surface almost intact.