Effects of dopants on the optical properties and microstructure of the high speed InSb optical recording thin film

Abstract
As the development of high density optical recording disc, studying of high speed phase change recording layer is an important goal. It had been reported that the In15Sb85 film has high speed crystallization rate(<6 ns). Because the stability of amorphous mark formed is not very stable, We doped Zn and Bi elements to stable the amorphous recording mark formed. In this study, the In15Sb85 films with 200Å thickness were produced by DC magnetron co-sputtering of In and Sb target, and investigated their application to the recording layer of high speed phase change optical recording media.

Thermal analyses show that the phase change temperature of (InSb)100-xZnx films (x=0~17.4) are between 181℃ and 221 ℃, and the activation energy are between 2.18 and 3.26eV . The phase change temperature of (InSb)100-xBix films (x=0~18.3 ) are between 181℃~167℃, and the activation energy are decreased between 2.18 and 1.50 eV. It means that Zn doping stable stabe the amorphous phase formed；Bi
doping can increase the crystallization rate. The spectrophotometer analyses show that the absorption of (InSb)100-xZnx and (InSb)100-xBix decreases with increasing Zn and Bi contents. But both of them still have good optical absorption. The optical contrast of (InSb)100-xZnx and (InSb)100-xBix films both decrease with increasing Zn or Bi contents. Their optical contrats are decreased with increasing Zn or Bi contents, but the 15% optical contrast can still be obtained when the Zn contentsequal increases 6.2 at.%.

The X-ray diffraction analysis shows that the as-deposited
(InSb)100-xZnx and (InSb)100-xBix films do not have any diffraction peak. After annealing at 250℃ for 30 min, the major crystalline phase of (InSb)100-xZnx film (x=0~9.1) are Sb and InSb. The Sb、InSb and ZnSb crystalline phases are appeared as x > 13.7. After the same annealing condition, the Sb、Bi and BiIn2 crystalline phases are found in the (InSb)100-xBix film (0 < x < 18.3 ).

The TEM analysis shows that the average grain size of the InSb film is about 30 nm after annealing at 250℃ for 30 min. After Zn doped, the average grain size of the InSb film is decreased to 22 nm as 6.2 at.% Zn is added. However, the grain size is increased to about 32 nm when
17.4 at.% Zn is added. On the other hands, as 5.5 at.% Bi is doped into the InSb film, the average grain size of the film is increases to about 50 nm. When 18.3 at.% Bi is added, the grain grows and the average grain size is about 72 nm.