Magnetic properties of germanium quantum dots

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Magnetic properties of germanium quantum dots
Yung Liou and Yen L. Shen Institute of Physics
In this study we have demonstrated that
room-temperature ferromagnetism exists in Ge
quantum dots deposited on polystyrene
nanospheres. The magnetization of Ge quantum
dots was dependent on both the thickness of the
Ge layer and the size of the polystyrene
nanosphere. A large room-temperature
magnetization was observed in the sample with a 5
nm thick Ge layer on 20 nm nanospheres. The
magnetism of Ge quantum dots was attributed to
both the quantum size effect and the magnetic
coupling among quantum dots. The magnetic
coupling was mediated through charge carriers in
junctions. By capping an extra metal layer on
top of Ge quantum dots, the magnetic coupling was
enhanced due to the additional charge carriers.
Advanced Materials 20, 779 (2008)
Figure 1. Schematic illustration of the
deposition of Ge quantum dots on polystyrene
nanospheres.
Figure 3. M-H loops measured for 3 nm thick Ge
layers grown on different nanospheres.
Figure 5. M-H loops of 3 nm thick Ge
layers capped with 3 nm thick layers of different
materials deposited onto 20 nm nanospheres.
Figure 4. M-H loops of different Ge layers grown
on 20 nm nanospheres.
Figure 2. AFM images of a) a 3 nm thick Ge layer,
b) a 3 nm thick Ge layer capped with a 3 nm Si
layer, c) a 3 nm thick Ge layer capped with a 3
nm Al layer, d) a 5 nm thick Ge layer, deposited
on 20 nm nanospheres.