in situ Observation of the surface reaction during synchrotron radiation-assisted gas source molecular beam epitaxy of silicon

We have developed a method for in situ observation of the surface reaction during synchrotron radiation-assisted gas source molecular beam epitaxy of silicon (SR-GSMBE), in which SR light optimized in photon energy and incident angle for stimulating the surface reaction with high efficiency plays another role as a probe for in situ observation. The SR irradiation condition dependence of the hydrogen removal efficiency on Si surfaces was examined by the measurement of photo-stimulated desorption yield of H+ ions and photoabsorbance. The monochromatized SR light, whose photon energy and incident angle were tuned at 23 eV and 45 degrees, respectively, for maximum efficiency of hydrogen removal, was employed as a probe beam for ultraviolet photoelectron spectroscopy (UPS). By monitoring the UPS intensity oscillation of the surface state due to dimer dangling bonds on a Si(100)2 x 1 surface during SR-GSMBE under such SR irradiation conditions, the simultaneous measurement of growth rate (GR) and surface hydrogen coverage was accomplished. The feasibility of in situ observation using the secondary electron emission near the low-energy cutoff and the Auger electron emission of Si L(II, III) Valence Valence (LVV) during nonmonochromatized SR irradiation with strong intensity was discussed because the UPS intensity oscillation method using well-monochromatized SR light is not then applicable. We point out that the removal of surface adsorbate such as hydrogen and chlorine leads to the suppression of growth defects as well as an increase in GR and therefore it is possible to suppress the growth defect generation by SR irradiation in GSMBE.