Vv. Litvinov et al., Enhancement of thermal donor formation in germanium by preliminary irradiation: infrared absorption measurements, PHYSICA B, 302, 2001, pp. 201-205
Infrared absorption at 10 K of oxygen-rich Ge crystals after irradiation wi
th fast electrons (E = 4 MeV, T approximate to 100 degreesC) and subsequent
annealing at 220-420 degreesC has been studied. It is found that upon heat
-treatments of the irradiated samples at 220-280 degreesC the simultaneous
formation of four bistable thermal donors (TD1-TD4) occurs. This process is
not accompanied by detectable changes in intensities of absorption bands a
t 780.4 and 818.0 cm(-1), which are related to the oxygen dimer. Upon follo
wing anneals of the samples at 300-420 degreesC, the strongly enhanced gene
ration of the higher order TDs is observed with a simultaneous decrease in
intensities of the bands originated from the oxygen dimer, TD1 and TD2. It
is inferred that direct transformations of some radiation-induced defects i
nto the first TD species occur in the irradiated samples. Radiation-induced
complexes giving rise to local vibrational modes in the region 570-577 cm(
-1) and/or at 729, 733.5 and 745 cm(-1) are suggested as possible precursor
s to the bistable TDs in Ge. (C) 2001 Published by Elsevier Science B.V.