Thin hafnium films have been prepared by evaporation by electron beam heating on the following three substrates, CaF
2 (111), KBr(100) and carbon coated CaF
2 (111). The film thickness was made 500Å or 1000Å and the environment of deposition was held at an ultrahigh vacuum.
The threshold of substrate temperature required to form single crystal films were found to be about the same on the three substrates and very low compared with the hafnium melting temperature (2222°C).
In the case of CaF
2 (111) substrate, the threshold temperature was as low as 380°C, being the epitaxial temperature at which bcc (111)
Hf is parallel to (111)
CaF2.
The films took three different crystal structures, hcp (α-phase), fcc and bcc (β-phase), depending on their substrate temperatures (Ts). In the case of carbon coated CaF
2 (111) substrate, the film structures were the following; hcp structure for Ts_??_350°C, fcc structure for 300_??_Ts_??_450°C and bcc structure for Ts_??_400°C. The lattice constant of fcc structure film was found to be
a0=4.98Å.
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