Stopping powers and energy straggling for 50-300 keV H+ in amorphous Si and Ge films

Stopping powers and energy straggling for 50-300 keV H+ beams in amorphous Si and Ge films were measured with a toroidal electrostatic analyzer. The samples prepared are Sb(1ML)/Si(001) and amorphous Si(a-Si)/Sb(1ML)/Si(001) and a-Ge/Si(111) formed by molecular beam epitaxy and with an electron beam evaporator, Atomic force and cross sectional transmission electron microscopes revealed the formation of uniform. and amorphous thin films with sharp interfaces. Ion scattering measurements were performed in situ first for Sb(1ML)/Si(001) and subsequently for a-Si films deposited on Sb(1ML)/Si(001) under an ultrahigh vacuum condition. The Sb peak shift and the broadening of the Sb energy spectrum give the stopping power and energy straggling, respectively. For a-Ge films, we extracted the stopping power and straggling values from the energy width and the slopes at the front and rear edges of the Ge spectrum, respectively. The present results are compared with the theoretical predictions and other experimental data.