Plating of ferrite film on 8" disc at 70°C by "spray-spin-coating" method

We have plated Fe
3
O
4
films on 8" discs of glass and Al at 70°C. The substrate was spinned at 400 rpm, onto which a reaction solution of pH=6.9 containing FeCl
2
and CH
3
COONH
4
(a pH buffer) was sprayed. As an oxidizer, air was supplied or NaNO
2
solution was sprayed. Plating for 30 min, we got the film ∼3000 Å in thickness, having a mirror-like luster. They were polycrystalline with no preferred orientation. They had a grain size of ∼1000 Å and a columnar structure perpendicular to the film plane. The film was oxidised to γ-Fe
2
O
3
by heating in air at 300°C. All the films of Fe
3
O
4
and γ-Fe
2
O
3
had no definite magnetic anisotropy, lying in the film plane. The smoothness of the film surface improved drammatically by filtering the solutions and putting the apparatus in a clean room, getting an average asperity height less than 100 Å.