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Effects of Intermediate Laser Ablation of Mn on Deposition of ZnS Films on ZnO Nanorods Grown by Chemical Vapor Deposition
|Takashi Hirate , Kenta Kakio , Tomomasa Satoh|
Kanagawa University, 3-27-1 Rokkakubashi, Kanagawa-ku, Yokohama 2218686, Japan
We have studied of deposition of ZnS:Mn films on ZnO nanorods grown by low-pressure chemical vapor deposition. In this study we report on the effects of laser ablation of Mn that is performed after ZnO nanorods’ growth and before deposition of ZnS:Mn films. We call this ablation as an intermediate laser ablation. The ZnO nanorods are grown on Si(111) substrate by chemical vapor deposition (CVD) combined with laser ablation of Mn. Metal Zn vapor and O2 gas are used as precursors to synthesize ZnO and N2 is used as carrier gas. The Mn pellet is placed near a substrate in a deposition chamber and ablated by a pulsed Nd:YAG laser beam (10 shots/sec, 0.04 J/shot). Firstly, ZnO nanorods with 100 nm diameter and 1700 nm height are grown for 10 min growth-time that are vertically aligned to a substrate. The pressure is 26.6 Pa, the temperature is 550 C and O2 mass flow rate is 0.88 SCCM. Then only the laser ablation of Mn is performed for 5 min without O2. Finally, ZnS:Mn films are deposited by changing the precursor from O2 to H2S for 10 min. The pressure is 67 Pa and 133 Pa, and mass flow rate of H2S is 2.0 and 4.0 SCCM. It is found that the intermediate laser ablation of Mn has a drastic effect on growth of ZnS:Mn films. When the intermediate laser ablation is not performed, the ZnS:Mn film mainly grows along the axis-direction of ZnO nanorod. When it is performed, however, the growth for lateral direction becomes dominant, although the growth rate along the axis-direction is not so changed. For example, when the mass flow rate of H2S is 2 SCCM and pressure is 67 Pa, the total length of nanorod is 3600 nm and diameter is 100 nm when the intermediate laser ablation is not performed. On the other hand, when the intermediate laser ablation is performed the total length of nanorod is 3000 nm and diameter is 540 nm. It is concluded that the intermediate laser ablation has an effect to enhance the growth rate of ZnS:Mn layer for the lateral direction of ZnO nanorods.
Presentation: Poster at E-MRS Fall Meeting 2007, Acta Materialia Gold Medal Workshop, by Takashi Hirate
See On-line Journal of E-MRS Fall Meeting 2007
Submitted: 2007-05-15 04:08 Revised: 2009-06-07 00:44