Cryogenic ultra-high vacuum scanning tunneling microscopy of electron-stimulated desorption of hydrogen and deuterium from silicon(100).

摘要

A cryogenic ultra-high vacuum (UHV) scanning tunneling microscope (STM) has been developed. This design utilizes a novel vibration isolation scheme which provides excellent thermal coupling to a cooling source. The cooling scheme departs from other cryogenic UHV STMs where vibration isolation and cooling compete with each other. Variable temperature operation from 11 K to 300 K has been demonstrated. Future improvements will enable operation down to 1.5 K. This system has been used to perform low temperature desorption studies of hydrogen and deuterium from Si(100) surfaces. Comparing these results to previous room temperature studies indicates that there is no temperature dependence to the desorption in the high voltage field emission regime. However, in the low voltage vibrational heating regime a strong temperature dependence is observed, with the desorption yield for hydrogen at 11 K being 300 times greater than at 300 K. In the context of Avouris' vibrational heating model, these data are consistent with an increase in the Si-H vibrational lifetime from 10 ns at 300 K to 19 ns at 11 K. By similar analysis, the Si-D vibrational lifetime increases from 0.25 ns at 300 K to 0.85 ns at 11 K.