Interaction of in Atom Spin-Orbit States with Si(100) Surfaces
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INTERACTION OF In ATOM SPIN-ORBIT STATES WITH Si(100)
SURFACES
DOEKE J. OOSTRA, RUSSELL V. SMILGYS AND STEPHEN R. LEONEt Joint Institute for Laboratory Astrophysics, University of Colorado and National Institute of Standards and Technology, and Department of Chemistry and Biochemistry, University of Colorado, Boulder, CO, 80309 tStaff member, Quantum Physics Division, National Institute of Standards and Technology.
ABSTRACT
Scattering and desorption of In from Si(100) is investigated. Laser induced fluorescence is used to probe the desorbing and or scattered species. Auger Electron Spectroscopy is used to study the composition on the surface. The results show that at surface temperatures below 820 K a two dimensional layer of In desorbs by a half order mechanism. This is explained by assuming two dimensional In islands on the surface. Above 820 K, desorption takes place by a first order mechanism. The desorption parameters appear to be spin-orbit state specific. The desorption energy for In 2 2 P3 / 2 is 2.8 ± 0.4 eV and for In P, 1 2 2.5 ± 0.2 eV. The difference is equal to the difference in the spin-orbit energy. So far no specular scattering of In is observed, suggesting that the sticking coefficients are unity.
INTRODUCTION
The interaction of molecular beams of group III elements with Si surfaces is being investigated extensively. The possibility to grow high quality GaAs layers on Si has stimulated detailed studies of adsorption, desorption and growth of Ga on Si(lll) and Si(l00) surfaces [1-5]. Al, Ga and In are also used as dopants in Si-device technology. However, these metals show strong surface segregation during MBE processing, which leads to distorted dopant depth profiles [6,7]. This has motivated some studies on the interaction of In with Si surfaces [8]. In this paper we investigate adsorption and desorption of In on Si(100) 2 2 for both spin-orbit states P,/ 2 and P 3 / 2 (upper state). This is done for two reasons: Firstly, at the Si surface In is chemically bound [8] suggesting that there is no spin-orbit character present. In vacuum the energy between the two spin-orbit states, AE, is 0.27 eV. Here, we examine whether this energy difference, AE, shows up as a difference in the desorption energy between the two states. This information will provide insights into the microscopic mechanisms of thermal desorption and the influence of the electronic states on adsorption and/or desorption.
EXPERIMENTAL
The experiments are performed in a previously described UHV chamber with a base pressure of 5 x 10-11 Torr [3-5,9]. A differentially pumped chamber houses commercially obtained Knudsen evaporation sources. A silicon (100) sample is mounted on a manipulator. By simple rotation the surface is positioned in front of the In beam from a Knudsen source or is examined by low energy electron diffraction (LEED) or by auger electron spectroscopy Mat. Res. Soc. Symp. Proc. Vol. 131. 91989 Materials Research Society
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(AES). The In beam comes in at an angle of z 20° from the surface normal. Laser induce
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