Temperature effects on synchrotron-radiation-excited Si atomic layer epitaxy using disilane

The effects of temperature on synchrotron-radiation-excited Si atomic layer epitaxy (SR-ALE) with disilane are clarified by evaluating the growth rate and crystal structure with cross-sectional transmission electron microscopy and reflection high-energy electron diffraction. At 210°C, surface roughening caused by reduced Si adatom migration resulted in a crystal-amorphous transition after deposition of 7 to 10 layers of Si. At 350°C, a planer epitaxial overlayer was grown with many V-shape defects. Above 350°C, thermal desorption occurs along with a photostimulated process which removes hydrogen atoms. This increased island formation, depending on the hydrogen coverage. If the gas exposure time is short, however, chemisorption was almost self-limiting. At 480°C, a 1 ML/growth cycle was achieved as a result of the photothermal mechanism.