1. Study of surface segregation and roughness using synchrotron radiation A.Iraji zad 3.SESAME users’ meeting Antalya 2004 Physics Department, Sharif University of Technology, Tehran, Iran

2. outline Introduce some of our results on Cu surface segregation Plan for further study using SR Other fields surface roughness measurement using AFM and light scattering interface roughness photoinduced nanoparticle formation porous silicon as gas sensors

3. Surface segregation of copper We have observed Cu at the surface of V 2 O 5 /Cu/Si bi layers during room temperature deposition Ni/Cu/Si and Permalloy/Cu/Si multilayers after Electrodeposition Applications: solid state Li battery, Giant magnetoresistance (GMR), spin valve Cu Deposited layer Segregated Cu Si

4. AES spectra of V 2 O 5 (100nm)/Cu A Iraji-zad et al; J. Phys. D: Appl. Phys.; 35 (2002) 1176 Cu top layer should be very thin.

5. Depth profile using SIMS tech. V 2 O 5 (100nm)/Cu(200nm) /Si sample Segregated Cu M. M. Ahadian, A. Iraji zad, “Structure and composition of the segregated Cu layer in V2O5/Cu/Si system”, submitted to Applied Surface Science

6. Surface electronic properties using Tunneling Spectroscopy V 2 O 5 (100nm)/Cu/Si and V 2 O 5 (100nm)/Si samples The segregated Cu changes the electronic surface local density of states from semiconductor to metallic behavior

7. Surface topography The effect of segregated Cu ( Presence of Cu under layer)

8. Cu segregation in Ni/Cu and Ni-Fe/Cu samples SIMS results on permalloy(200nm)/Cu Segregated Cu glow discharge optical spectroscopy of Ni(100nm)/Cu/Si

9. AES result of electrochemical deposited Ni(100nm)/Cu The accumulation of Cu at the surface M.M. Ahadian, A. Iraji-zad, A. G. Dolati, M. Ranjbar, “Induced segregation of Cu in permalloy thin films produced by electrochemical deposition”, in preparation

10. XPS result for electrochemical deposited Ni(100nm)/Cu XPS & AES indicate the chemical state of Cu at the surface: Cu 2 O Uniform Ni layer

11. Summary of the first part Cu segregation occurs in both systems during room temperature deposition. We should know Cu depth profile near the surface to understand this phenomenon Destructive depth profile methods alter the profile.

12. XPS method is a non-destructive method depth profile measurement by –Changing incident X-ray energy –Changing incident angle Conventional XPS represents a severe limitation Synchrotron radiation source is needed for better depth profile measurement. E Photoelectron = hע- Binding Energy inelastic mean free path of electron depends on the electron energy

13. By changing the energy of incident X-ray, depth profile is possible: e.g. Al at the surface of zeolite

14. Depth profile of carbon chemical state

15. Angle resolved XPS SiO 2 layer at the surface of Si

16. Surface roughness measurement e.g. dynamic behavior of growing surface, interface effects –Methods : SPM, photon scattering,… –Interfacial roughness changes the physical properties of multilayer systems e.g. GMR, QW, spin valves,….. –Antiferromagnetic coupling is dependent on the interfacial structure, A.Iraji zad, et al, Height fluctuation and intermittency of V2O5 films by atomic force microscopy, Journal of Physics Condensed Matter, 15, 2003, pp. 1889-1898 B.Stochastic and regeneration of rough surface, Phys. Rev. Lett., 91: (22), 226101-1-226101- 4,.2003

17. AFM as surface profiler statistical parameter Disadvantage: slow,Tip effect, surface damage,….. Advantage: A direct method, good information on lateral scale

18. visible light scattering topography fast, no information on lateral scale, information in micron size G. R. Jafari, P. Kaghazchi, R. S. Dariani,A. Iraji zad, S. M. Mahdavi, M. Reza Rahimi Tabar and N. Taghavinia, Non-Pertubative Two Scale Kirchhoff Theory: Comparison of Experimental Observations with Theoretical Prediction, is submitted to Physical Review B, 2004 PMT Laser

19. Soft X ray scattering provide better information of surface and interface roughness Ni Cu Si Interface roughness measurement by AFM

20. Small angle x ray scattering (SAXS) and Grazing Incidence GISAXS good for Q dot structure h: roughness exponent Labat et al, Applied Surface Science, 188,2002,p182

21. SAXS for CoFe/Cu multilayer at different X-ray energy

22. Anodic Aluminum oxide (AAO): Fabrication, Mechanisms and Characterization as a starting material for the fabrication of several kinds of functional devices with nanometer dimensions like catalysts, filters, magnetic recording media,….

23. nanowire in AAO next step: formation of spin valve by electrodeposition Farzad Nasirpouri, Mohammad Ghorbani, Azam Irajizad, Amir Mehdí Saedi, Alain Nogaret, Growth sequences of highly ordered nano-porous anodic aluminium oxide, Trends in Nano technology (TNT2004), Spain, sept. 2004

24. Next step: Structural studies SAXS (small angle), X ray diffraction Pore characterization in the range 2-200 nm EXAFS provide information on oxidation state

25. Photochemical method Illumination is the main parameter for reaction progressing. Zn(SO4 ) Na2 S Zn S Capping agent molecules usually used to keep the sizes small. A photochemical based method for nanoparticle synthesizing and formation e.g. CdS nanoparticle Chemical method

26. Fig 2. Band gaps and sizes of the samples versus illumination time that are prepared with surfactant concentration of 0.5 Mol/lit A photochemical method for controlling the size of CdS nanoparticles M. Marandi, N. Taghavinia, A. Iraji-zad, S. M. Mahdavi, and M. R. Esmaili,is submitted to nanotechnology Adjustable parameter Illumination time, density of surfactant and PH of the solution Photoinduced nanoparticles growth: size control by UV illumination, Nima Taghavinia, Azam Iraji zad, Mohammad Mahdavi and M. Reza Esmaili, submitted to Jounal of Nanoscience & Nanotechnology. TEM image of the samples with effective band gap of 3.4

27. Light surface interaction Surface etching film deposition e. g. Ni, Pd Nanoparticle formation e. g. Au Particle size controling

28. 50  m PPS p typeN type P type Chemical etching the Si surface

29. Gas sensors based on porous silicon Chemical ecthing +Pd nano particle deposition by electroless method as hydrogen sensitive A.Iraji zad1, F.Rahimi, M.Chavoshi, M.M.Ahadian, Characterization of porous poly-silicon as a gas sensor, Sensor and Actuators B, 100( 2004) 341-346

30. Wet deposition Synchrotron x-ray can induced electroless metal deposition useful for microelectronics and x ray optics or etching over the solid surfaces Selected area new material processing method, rapid maskless patterning technique. Nano particle formation Borse et al, pH dependence of synchrotron x-ray induced electroless nickel deposition, JAP, 95,3,2004,p 1166

31. Conclusion Synchrotron radiation is a valuable source in our future research Possible to determine Thickness, composition, depth profile of segregated Cu Surface roughness measurement in nano scale Interface roughness determination in multilayer systems Light assisted nanoparticle formation & synthesis size controlling, deposition and etching Need in access, collaboration and contribution Need to train potential users as well as operators, designers,….

32. acknowledgment PhD students M. M. Ahadian M. Marandi F. Rahimi R. Tilaki F. Nasiripouri G. Jafari M. R. Rahimi Tabar N. Taghavinia S. M. Mahdavi M. Dolati M. Gorbani

33. Nitrogen at the surface of Si