1. Growth and Characterization of Co nanoparticles and nanowires 劉全璞國立成功大學材料科學及工程學系半導體奈米材料實驗室

2. Outline 1.Introduction : Nanoparticle; nanowire; and PVD 2.Co nanoparticle by magnetron sputtering 3.Co nanoparticle and nanotube by ion-beam deposition 4.Conclusions

3. Traditional PVDs for nanopaticle fabrication Clusters by free jet expansion Nanoparticle by low temperature deposition Quantum dot by epitaxial growth

4. Clusters by free jet expansion

5. Nanoparticle by low temperature deposition

6. Quantum dot by epitaxial growth Stranski-Krastanow growth mode What happen when together? Shape evolution

7. Traditional VLS for nanowire growth

8. Objectives Si substrate native SiO 2 Co nanoparticles These can be used for catalysts. Various types of CNT can be grown.

9. (a)(b)(c) (d) (e) (f) Deposition distance vs surface morphology AFM P W = 8 mtorr 、 P DC = 50 W 、 V bias = -100 V 、 t D = 10 sec 60mm70mm80mm 90mm100mm110mm Size =60-120nmSize =120-150nm Size = 130-170nm

10. -50V (b) 0V (c) +250V (d) +525V (e) 0 nm 17.5 nm 35 nm -100V (a) 500 nm Substrate bias vs surface morphology AFM P W = 8 mtorr 、 P DC = 50 W 、 D T, Sub = 110 mm 、 t D = 10 sec

11. (b) Substrate bias vs size and height

12. Substrate bias vs island density positive V bias obvious particles uniform distribution

13. 1μm100 nm Substrate bias vs surface morphology SEM plan view -100V -50V +250V

14. 20 nm fcc structure BF DF Substrate bias vs nanoparticle microstructure TEM plan view

15. 20 nm 100 nm 40 nm Substrate bias vs nanoparticle microstructure TEM cross sectionV sub = +250 V

16. Substrate bias – nanoparticle growth mechanism Coulomb force self-limited growth deposition e-e- e-e- crevice filling SiO 2 Si substrate repulsion deposition e-e- e-e- repulsion SiO 2 Si substrate island growth Si substrate deposition e-e- e-e- SiO 2

17. -100 V -50 V +525 V +250 V 0 V Substrate bias vs nanoparticle magnetic property

18. Growth time vs surface morphology AFM P W = 8 mtorr 、 P DC = 50 W 、 D T, Sub = 110 mm 、 t D = 10 sec 、 Vsub = +525 V (a) 20.1 ML (b) 39.8 ML (c) 59.6 ML 10 sec 20 sec30 sec

19. (a) 20 nm (b) 20 nm (a) 100 nm (c) 50 nm (b) 100 nm 20 sec fcc 30 sec fcc Growth time vs nanoparticle microstructure TEM cross sectionV sub = +250 V

20. 1 ： ANODE grid 2 ： A/D grid 3 ： Ground grid solenoid coil P waveguide gas ECR zone 1 2 3 E θ target water cooling Cu backing plate resputtered atom sputtered atom fast Ar substrate sputter voltage (positive bias) Mechanism of ion beam deposition

21. Co nanoparticle and wire by ion beam deposition SEM 2sec 、 RT2sec 、 400 ℃ ( c )( d ) 2sec 、 950 ℃

22. 10 12 cm -2 10 11 cm -2 5*10 8 cm -2 Co nanoparticle with various density

23. Co nanowire growth by ion beam deposition AFM 0.5  m Nucleation of Cobalt silicide nanowire On Si(001) 0.5  m Cobalt magnetic quantum dots on Si(001)

24. 100nm 402 111 513 311 622 222 531 220 402 222 131 440 751 660 351 042 333 - - - - - 351 000 311 622 220 531 751 440 713 - - - 131 - - - - - - - - - - - - 042- Co nanowire growth by ion beam deposition TEM

25. Conclusions Nanoparticle can be formed under negative bias at suitable conditions, however, damaged. Due to Coulomb force self-limited growth, Co nanoparticle is of very uniform distribution without obvious damage. Co nanoparticle as small as 10nm can be prepared by sputtering and exhibit superparamagnetic property

26. Conclusions By IBS, the Co dot density can be varied by 1000 with very uniform size distribution EPitaxial Cobalt silicide nanowire can be fabricated by IBS

27. Acknowledgements 1.Students : 鍾秉憲 ; 王志欽 2. 國科會 NSC 91-2120-E006-003