Nanomateriais

1. Nanomateriais Prof. Lucas Freitas Berti Engenharia de Materiais - UFAM

2. Quantization Atom Atom Video Quantization • Quantization video

3. Nanowire

4. Synthesis; Characterization and Physical Properties of Nanowires; Applications; Nanowire

5. Synthesis; • Template-AssistedSynthesis; • VLS Method for NanowireSynthesis; • OtherSynthesisMethods; • Hierarchical Arrangement and Superstructures of Nanowires. Nanowire

6. Characterization and Physical Properties of Nanowires; • Structural Characterization; • Mechanical Properties; • Transport Properties; • Optical Properties. Nanowire

7. Applications; • Electrical Applications; • Thermoelectric Applications; • Optical Applications; • Chemical and Biochemical Sensing Devices; • Magnetic Applications. Nanowire

8. Nanowires are especially attractive for nanoscience studies as well as for nanotechnology applications. • Nanowires, compared to other low dimensional systems, have two quantum confined directions while still leaving one unconfined direction for electrical conduction. • This allows them to be used in applications which require electrical conduction, rather than tunneling transport. Nanowire

9. Tunneling Nanowire

10. Tunneling Nanowire

11. Tunneling Nanowire • Video Tunneling

12. Nanowire Because of their unique density of electronic states, nanowires in the limit of small diameters are expected to exhibit significantly different optical, electrical, and magnetic properties from their bulk 3-D crystalline counterparts.

13. Nanowire Properties • Increased surface area; • very high density of electronic states; • joint density of states near the energies of their van Hove singularities; • enhanced exciton binding energy, • diameter-dependent bandgap, • increased surface scattering for electrons and phonons Just some of the ways in which nanowires differ from their corresponding bulk materials.

14. Nanowire Not only do nanowires exhibit many properties that are similar to, and others that are distinctly different from those of their bulk counterparts, nanowires have the advantage from an applications standpoint in that some of the materials parameters critical for certain properties can be independently controlled in nanowires but not in their bulk counterparts.

15. Nanowire nanowires have been shown to provide a promising framework for applying the bottom-up approach [Feynman lecture on nanoscience] to the design of nanostructures for nanoscience investigations and for potential nanotechnology applications

16. Nanowire Driven by: • new research and development opportunities; • the smaller and smaller length scales now being used • the semiconductor; • Optoelectronics; • Magnetics industries; • the dramatic development of the biotechnology industry where the action is also at the nanoscale; Nanowire research fieldhasdeveloped with exceptional speed in the last few years

17. Nanowire A review of the current status of nanowire research is of significant broad interest at the present time. • focusing on nanowire properties that differ from those of their parent crystalline bulk; • applications that might emerge from • the unique properties of nanowires; • from future discoveries in this field.

18. Nanowire Examplesoftypicalnanowiresthat have been synthesized and studied are listed in following Table

19. Nanowire [Ref] 2010

20. Characterization ScanningTunnelingProbes Scanningtunnelingmicroscopy (STM); Electricfieldgradientmicroscopy (EFM); Magnetic field microscopy (MFM); Scanning thermal microscopy (SThM) Combined with atomic force microscopy (AFM) Nanowire • ScanningElectronMicroscopy: • SEM; • FESEM; • TEM • HRTEM;

21. Nanowire SEM • Essential components of all SEMs include the following: • Electron Source ("Gun"); • Electron Lenses; • Sample Stage; • Detectors for all signals of interest; • Display / Data output devices. • Infrastructure Requirements: • Power Supply; • Vacuum System; • Cooling system; • Vibration-free floor; • Room free of ambient magnetic and electric fields.

22. Nanowire SEM

23. Nanowire SEM

24. Nanowire Images More magnification

25. Nanowire Tungsten filament.

26. Nanowire Schematic of the self-biased thermionic tungsten electron gun.

27. Nanowire Field Emission Gun - FESEM

28. Nanowire Images More magnification

29. Nanowire

30. Nanowire Astigmatism

31. Nanowire

32. Nanowire

33. Nanowire Images More magnification

34. Nanowire Images

35. Nanowire HRTEM: • High-resolution transmission electron microscopy (HRTEM) is an imaging mode of the transmission electron microscope (TEM) that allows the imaging of the crystallographic structure of a sample at an atomic scale.

36. Nanowire HRTEM: • Because of its high resolution, it is a valuable tool to study nanoscale properties of crystalline material such as semiconductors and metals. At present, the highest resolution realised is 0.47 ångströms (0.047 nm) with double aberration-corrected JEOL R005, Cold Field Emission Gun TEM, at Tokyo Institut of Technology

37. Nanowire ScanningTunnelingProbes

38. Nanowire

39. Nanowire

40. Nanowire Images

41. Nanowire ThermalStability: • The thermal stability of nanowires is anticipated to differ significantly from that of the bulk material; • nanowire studied systems: • porous matrices impregnated with a plurality of nanowires, • individual nanowires sheathed by a thin coating, and; • individual nanowires.

42. Nanowire Pore-confined indium shows a linear dependence on inverse pore diameter, with a maximum melting point depression of 50K. They also recorded a 6K difference in the melting temperature and the freezing temperature of 12.8 nm diameter indium.

43. Nanowire Sheathed nanowires provide an opportunity to study the melting and recrystallization of individual nanowires. • The shell layer surrounding the nanowire provides confinement to keep the liquid phase within the inner cylindrical volume.

44. Yang et al. [4.130]. Nanowire the nanowires began melting from their ends, with the melting front advancing towards the center of the nanowire as the temperature was increased They reported both the largest melting point suppression recorded thus far for germanium (≈ 300 ◦C), and a large melting–recrystallization hysteresis of up to ≈ 300 ◦C. • germanium nanowires coated with a thin (1–5 nm) graphite sheath: • followed the melting and recrystallization of the germanium by variable temperature TEM; • The melting of the nanowires was followed by the disappearance of the electronic diffraction pattern.

45. Yang et al. [4.130]. Nanowire the nanowires began melting from their ends, with the melting front advancing towards the center of the nanowire as the temperature was increased They reported both the largest melting point suppression recorded thus far for germanium (≈ 300 ◦C), and a large melting–recrystallization hysteresis of up to ≈ 300 ◦C. • germanium nanowires coated with a thin (1–5 nm) graphite sheath: • followed the melting and recrystallization of the germanium by variable temperature TEM; • The melting of the nanowires was followed by the disappearance of the electronic diffraction pattern.

46. Nanowire Similarly, carbon nanotubes have been filled with various low-temperature metals [4.131]. • A nanothermometer has been demonstrated using a 10 nm liquid gallium filled-carbon nanotube, showing an expansion coefficient that is linear in temperature and identical to the bulk value [4.132].

47. A different behavior was observed in free-standing coppernanowires [4.134]. Nanowire Thermal treatment of the free-standing nanowires leads to their fragmentation into a linear array of metal spheres. • Littleinteraction between the nanowire surface and the surroundings, and the nanowire is not confined in its diameter, as in the case of the sheathed nanowires.

48. Nanowire Transport Properties: • The study of electrical transport properties of nanowires is important for nanowire characterization, electronic device applications (quantum effects):

49. Nanowire Important factors that determine the transport properties of nanowires: • wire diameter, (important for both classical and quantum size effects), • material composition, • surface conditions, • crystalquality, and the crystallographic orientation along the wire axis for materials with anisotropic material parameters, • such as the effective mass tensor, • the Fermi surface, or the carrier mobility.

50. Nanowire Electronic transport phenomena in low-dimensional systems can be roughly divided into two categories: • ballistic transport and, • diffusive transport.