Amorphous silicon layer characteristics during 70-2000 eV Ar+-ion bombardment of Si(100)

Spectroscopic ellipsometry (SE) has been applied to characterize the damaged, amorphous silicon (a-Si) layer created by Ar+-ion bombardment in the ion energy range of 70-2000 eV impinging at 45 Deg angle of incidence on Si(100). The dielec. functions of a-Si during ion bombardment have been detd. using the Tauc-Lorentz model for the dielec. functions e1 and e2. The dielec. functions resemble literature reports on a-Si-like dielec. functions. The a-Si layer thickness under ion bombardment conditions reaches values from ~17 A at 70 eV up to ~95 A at 2000 eV. These values compare reasonably well with SRIM and mol. dynamics simulations. The surface roughness, as detd. with SE, is typically 5-15 A during ion bombardment, with a min. roughness at Eion=250 eV. The creation of the amorphous silicon top layer upon 70 eV Ar+-ion bombardment with an ion flux of 0.07 ML s-1 has been resolved using real-time spectroscopic ellipsometry. The creation of the amorphous layer shows a double exponential ion-dose dependence: a fast, initial period of a-Si creation, with 1/e const. Dt1 = 2 ML, and a slower period, Dt2 = 9 ML, until the matrix is fully amorphous after .apprx.30 ML of Ar+ dosing. Relaxation of the a-Si top layer has been obsd. after the ions are switched off and has been analyzed with a stretched-exponential decay as a function of time, which is characteristic for a defect-controlled relaxation in the bulk a-Si layer. The corresponding time const. t is found to be .apprx.360 s, which is typically obsd. for self-annealing in amorphous silicon materials. [on SciFinder (R)