tion in a polycarbonate membrane. The pulsing condition determines whether the
grown wire is single crystalline or polycrystalline. Single crystal nanowires have a
superconducting T c A 7:4 K close to the bulk value while the polycrystalline nanowire with the same dimension has a T c A 5:8 K.
The nanowires grown in these templates are often not stable initially and it
appears that there is significant current driven change in the resistance as current
is passed through them [38]. The resistance changes also do not occur smoothly
but by steps and jumps. This is shown in Figure 21.9. This is very similar to electromigration (em) phenomena that one sees in metal films when a high current is
passed through them. The difference, however, is that in metal films em leads to
mass transport, which leads to failure of the films, but in nanowires this actually
reduces the resistance and is like a recovery process.
In recent years there have been reports of photoluminescence (PL) studies on
metal oxide nanowires of In 2 O 3 [39] and ZnO [40]. In 2 O 3 nanowires of 40–90 nm
diameter were grown on alumina templates using a DC deposition (V In ¼ À1 V)
from a bath of InCl 3 (38 mM) and Na 3 C 6 H 5 O 7 Á2H 2 O (85 mM). The In 2 O 3 was
made by oxidizing In wires at 100 K in oxygen and they showed a PL band at
@425 nm.
An ordered array of ZnO nanowires on alumina membranes was prepared by
oxidizing electrodeposited Zn nanowires in air at 300
C. The electrodeposition
was carried out from an acidic bath of ZnSO 4 Á7H 2 O (0.3 M Boric acid and 0.28 M
ZnSO 4 Á7H 2 O). The grown nanowires showed PL at @55 nm.
10 nm CdS Q-dots have been deposited in alumina membranes [41] by electrolyzing the membrane with H 2 SO 4 and then dipping it in boiling CdSO 4 . The acid
treatments leave S ions on the templates. The Cd
2þ ions react with the S ions to
form CdS in the nanopores. The array of Q-dots shows Raman lines that are red
Fig. 21.9. Current induced changes in metallic silver nanowires made by template synthesis.
21.3 Fabrication of Nanostructures in the Templates 701
grown wire is single crystalline or polycrystalline. Single crystal nanowires have a
superconducting T c A 7:4 K close to the bulk value while the polycrystalline nanowire with the same dimension has a T c A 5:8 K.
The nanowires grown in these templates are often not stable initially and it
appears that there is significant current driven change in the resistance as current
is passed through them [38]. The resistance changes also do not occur smoothly
but by steps and jumps. This is shown in Figure 21.9. This is very similar to electromigration (em) phenomena that one sees in metal films when a high current is
passed through them. The difference, however, is that in metal films em leads to
mass transport, which leads to failure of the films, but in nanowires this actually
reduces the resistance and is like a recovery process.
In recent years there have been reports of photoluminescence (PL) studies on
metal oxide nanowires of In 2 O 3 [39] and ZnO [40]. In 2 O 3 nanowires of 40–90 nm
diameter were grown on alumina templates using a DC deposition (V In ¼ À1 V)
from a bath of InCl 3 (38 mM) and Na 3 C 6 H 5 O 7 Á2H 2 O (85 mM). The In 2 O 3 was
made by oxidizing In wires at 100 K in oxygen and they showed a PL band at
@425 nm.
An ordered array of ZnO nanowires on alumina membranes was prepared by
oxidizing electrodeposited Zn nanowires in air at 300
C. The electrodeposition
was carried out from an acidic bath of ZnSO 4 Á7H 2 O (0.3 M Boric acid and 0.28 M
ZnSO 4 Á7H 2 O). The grown nanowires showed PL at @55 nm.
10 nm CdS Q-dots have been deposited in alumina membranes [41] by electrolyzing the membrane with H 2 SO 4 and then dipping it in boiling CdSO 4 . The acid
treatments leave S ions on the templates. The Cd
2þ ions react with the S ions to
form CdS in the nanopores. The array of Q-dots shows Raman lines that are red
Fig. 21.9. Current induced changes in metallic silver nanowires made by template synthesis.
21.3 Fabrication of Nanostructures in the Templates 701