Homogeneous growth of zinc oxide whiskers

 

SEM micrograph of ZnO whiskers. Bar indicates 100 mm.         Tip of the ZnO whisker. The radius of curvature is approximately 20 nm.

 

ZnO whiskers were epitaxially grown by a chemical-vapor deposition technique employed at atmospheric pressure. Highly oriented ZnO whiskers grew at a substrate temperature of 550C on (0001)a-Al2O3 substrates with a growth rate of 3.7 nm/s.  X-ray diffractometry revealed that the epitaxial relationship between the whiskers and the substrate was determined as ZnO[010](0001) // Al2O3[20](0001) or ZnO[20](0001) // Al2O3[010](0001).  In addition, the full-width at half maximum value of the (0002) reflection was as low as 0.43. Images obtained using a scanning electron microscope were analyzed and it was found that the whisker tip likely has a radius of curvature of approximately 20 nm.  The typical number density of the whiskers has reached 1.3x105mm-2. 

ZnO whiskers were prepared using an atmospheric CVD apparatus that was previously employed in obtaining epitaxial anatase films, with titanium tetra-isopropoxide as the source complex.  The reactant zinc 2,4-pentanedionate (Zn(C5H7O2)2, Soekawa Chemical Co., quoted purity of 99.9%), was loaded into a vaporizer and vaporized at 115C.  The reactant vapor was first carried by nitrogen gas flowing at a rate of 1.2 dm3/min and then sprayed from the metallic nozzle directly onto the single crystalline (0001)a-Al2O3 substrate mounted on an electric heater. Zn(C5H7O2)2 was immediately decomposed by the heat from the substrate heater.  The deposition duration of ZnO was maintained between 10 and 2500 minutes for each experiment using a metallic shutter placed below the nozzle.  The substrate was heated to 550C using an electric heater positioned behind the substrate.  The distance between the nozzle and the substrate was kept constant at 15 mm throughout the experiments. 

 

Schematic diagram of our CVD apparatus.

 

References

About  ceramics whisker

H. Saitoh, Y. Namioka, H. Sugata, S. Ohshio, gNanoindentation Analysis of Al:ZnO Epitaxial Whiskersh, Jpn. J. Appl. Phys. 40, 6024-6028 (2001).

H. Saitoh, M. Satoh, N. Tanaka, Y. Ueda, S. Ohshio, gHomogeneous growth of zinc oxide whiskersh, Jpn. J. Appl. Phys. 38 (12A) 6873-6877 (1999).

M. Satoh, N. Tanaka, Y. Ueda, S. Ohshio, H. Saitoh, gEpitaxial growth of zinc oxide whiskers by chemical-vapor deposition under atmospheric pressureh, Jpn. J. Appl. Phys. 38 (5B) L586-L589 (1999).