The Raman signature of the local Ce-C mode for substitutional C is ide
ntified as a narrow line (8 cm(-1) full width at half maximum) near 53
0 cm(-1) in alloy films of Ge1-yCy (0 less than or equal to y less tha
n or equal to 0.07) grown on Ge (100) substrates by low-temperature (2
00 degrees C) molecular beam epitaxy. The intensity of the Ge-C line r
elative to the c-Ge line suggests that only a small fraction of the no
minal C is in substitutional sites. In ternary alloys of Ge1-x-ySixCy
with x= 0.1 and 0.2 and y = 0.03, the Ge-C mode disappears, suggesting
a strong bias towards C bonding with Si as opposed to Ge. In Ge,,Sn,
films the Ge-Sn mode is seen at 263 cm(-1). (C) 1998 American Institut
e of Physics.