This document discusses nanoscience and nanotechnology concepts. It begins with an introduction to nanoscience topics like quantum effects at the nanoscale. It then discusses various nanostructures such as nanoparticles, nanotubes, thin films and their potential applications. The document also covers magnetic nanostructures such as ferromagnetism and magnetic domains. Measurement techniques like scanning tunneling microscopy are described. Finally, the document discusses thin film fabrication and the giant magnetoresistance effect in multilayer thin films.

1. NANOSCIENCE NANOTECHNOLOGY Walkiria Eyre [email_address]

2. TOPICS Nanoscience and nanotechnology concepts The begining of the nanoscience research Abstract on some nanostructures and it´s aplications Magnetic nanostructures Part 1 Part 2

3. Nanoscience Fisics Engeneering Biology Chemistry Basic life processes Chemical reactions Medicine Classical Fisics Quantum Fisics Smart materials Technological aplications

4. Nanotechnology Using nanoscience to create: Smart materials Engines (in nanometric scale) Devices (with an enormous amount of aplications)

5. Nanostructures Between 1 a 100 nm What is smaller than 1 nanometer ? Alone atoms Small and simple molecules

8. NANO = 10 -9 Why is this size so special ? Nanostructures are the smallest solid things we can do Quantum effects start to appear Root of fundamental properties of the materials

9. Nanofabrication techniques Top-down : nanostructure is obtained by successive cuts Bottom-up : nanostructure is build in an atom by atom deposition

10. Beginning of Nanoscience 1959 – Richard Feynman “ there´s plenty of room at the bottom” New instruments: Tunneling microscopes Atomic force microscopes Near-field microscopes

11. 1981 – Gerd Binning e Heinrich Roher (laboratório IBM em Zurique) STM SCANNING TUNNELING MICROSCOPE

12. IBM Logo xenon atoms on nickel substract

13. Image obtained by scanning the exponencial decrease of the tunneling current

14. Instruments: STM: scanning tunneling microscope AFM: atomic force microscope contact AFM non contact AFM dynamic contact AFM MFM: magnetic force microscope EFM: electrostatic force microscope SVM: scanning voltage microscope KPFM: kelvin probe force microscope SCM: scanning capacitance microscope FMM: force modulation microscope SThM: scanning thermal microscope NSOM: near-field scanning optical microscope SNOM: scanning near-field optical microscope From: http://en.wikipedia.org/wiki/Scanning_probe_microscopy

15. STM From: http://en.wikipedia.org/wiki/Scanning_tunnelling_microscope

16. Piezoelectric effect The piezoel ec tric effect was discovered by Pierre e Jacques Curie in 1880 and consist s on varia tion of fisical dimens ions of cert ain materia l s subjected to an externally applied voltage. O pposite also occurs , e.g., when a mechanical stress is applied, a voltage is generated in response. The quartz and the t ourmaline, natural crystals , are piezoel ec tric.

17. Images creation process A tip scan the surface at a distance of few atomic diameters The tunneling current decreases exponentially with increasing distance From: http://www.almaden.ibm.com/vis/stm/gallery.html

18. Continue... Colors are added taking in account different properties like height, curvature, etc... From: http://www.almaden.ibm.com/vis/stm/gallery.html

19. Impurity on copper From: http://www.almaden.ibm.com/vis/stm/gallery.html

20. Sodium and iodine on copper From: http://www.almaden.ibm.com/vis/stm/gallery.html

21. Iron on copper From: http://www.almaden.ibm.com/vis/stm/gallery.html

22. “ atom” Iron on copper From: http://www.almaden.ibm.com/vis/stm/gallery.html

23. Carbon monoxide on platinum (111) From: http://www.almaden.ibm.com/vis/stm/gallery.html

24. Process: From: http://www.almaden.ibm.com/vis/stm/gallery.html

25. Examples: From: http://www.almaden.ibm.com/vis/stm/gallery.html

26. Nanostructures: The nanostructures can be divided in some classes, like: Nanoparticles Nanofilms Nanowires Nanotubes

27. Nanostructures and potencial aplications: At atomic scale: Quantum wells Extreme - thin layers of semiconductor material ( the well ) grown between barriers (gr ids ). The gr ids imprison electrons in the extreme- thin layers . CD devices, telecomunication, optics From: http://www.mct.gov.br/index.php/content/view/index.php

28. A typical configuration for a quantum well (AlIn)GaN LED on a sapphire substrate. Epitaxial layer thicknesses are exaggerated for clarity and are not to scale. From: http://www.mtmi.vu.lt/pfk/funkc_dariniai/diod/led.htm

29. Quantum dots F luorescent nanoparticles . Depending on its composition, these particles can show many different colors . Telecommunications, optics . Polymers Some organic materials emit light under electric c urrent action . informatics From: http://www.mct.gov.br/index.php/content/view/index.php

30. “ Lead selenide (PbSe) quantum dots like the ones in this image, <10nm in size, emit light in the visible regime (~1 to 3eV). The nanoparticles in this scanning tunneling electron micrograph are similar to those in the colorful photograph of CdSe quantum dot containing material. (Micrograph courtesy of Mick Thomas, Cornell University) ” From: http://instruct1.cit.cornell.edu/courses/comm494-nano/working_version/3article.htm

31. The emission from quantum dots is tuned by changing the particle size. These quantum dot solids, containing CdSe nanocrystals dispersed in a polymer matrix, span the visible spectrum when excited with ultraviolet light. For scale, containers are ~ 1 cm in diameter. From: http://instruct1.cit.cornell.edu/courses/comm494-nano/working_version/3article.htm

32. Part icles smaller than 100 nm : Nanoc a psul e s Buckminsterfullerenes are the most known . D i sco vered in 1985, these part i c le s have 1 nm width. Dry Lubri cant . C atal y tic n anopart icles In a 1-10 nm range , these particles, when manipulated, shows a great superf i cial area, improving its reactivity M aterials, fuels and foods production From: http://www.mct.gov.br/index.php/content/view/index.php

33. “ Scanning tunneling microscope (STM) image of a silver surface with adsorbed potassium atoms and two C-60 buckyballs. Using the STM tip to drag one of the buckyballs around the surface, UC Berkeley researchers were able to pick up single potassium atoms at a time, subtly altering the buckyball's electronic properties with each addition. Credit: Michael Crommie/UC Berkeley. (Image courtesy of Science) ” From: http://www.nanotech-now.com/ucb-release-03112004.htm

34. Wires with less than 100 nm di a met e r Carbon Nanotubes Two types exist: single wall nanotub e s, call ed “ buckytubes ” , and multi-wall nanotub e s. Described as the most important material in nanotec h nolog y , t hey can have big mechanical resistance , 50-100 times that steel in one sixth of its weight. S pace and electronic industries, aviation and innumerable other areas . From: http://www.mct.gov.br/index.php/content/view/index.php

35. Films with less than 100 nm thickness Self-assembled Mono layers Organic or inorg a nic substances that, spontane ously , form a layer of the thickness of a molecule A large amount of applications based on the chemical and physical properties . From: http://www.mct.gov.br/index.php/content/view/index.php

36. Self-assembled monolayer From: http://www.mtl.kyoto-u.ac.jp/english/laboratory/nanoscopic/nanoscopic.htm

37. N anopartic les coverings Stainless steel layers applied by nanocr y stalin powder confer greater hardness in comparison with conventional applications. Sensors. Fabrica tion of liquid cr y stal. M olecular wires . Lubrication, protection and anticorrosive layers . Stronger and hard er cut tools. From: http://www.mct.gov.br/index.php/content/view/index.php

38. CNT

44. MAGNETIC NANOSTRUCTURES

45. Topics Magnetism concepts Magnetic materials Magnetic nanostructured systems Thin films Giant Magnetoresistence

46. Spin Classic point of view: Rotation m ovement of the electron around a n axle, it means , an angular moment

47. Magnetic moment SPIN ( angular moment) *charge* Magnetic Moment

48. Magnetic Moment

49. Magnetization It is the total magnetic moment of a certain amount of the substance for unit of volume Due to this , electrons tend to line up when submitted to a n external magnetic field

50. MAGNETIZATION Alignment of electrons due to the field

51. In the majority of atoms total spin is null Due to the occupation of the orbital s Linus Pauling principle For some elements total spin is not null These elements have permanent magnetic moment Examples: Iron, Cobalt, Nickel, Manganese, Gadolinium, Europium.

52. Magnetic Behaviors In accordance with its behavior in the presence of a n external magnetic field, the magnetic materials can be classified in: Metamagnetic *Superparamagnetics* Spin glass Speromagnetic Helimagnetic Diamagnetic Paramagnetic Ferromagnetic Ferrimagnetic Antiferromagnetic

53. Magnetic Susceptibility For a large amount class of isotropic and linear materials, we have : Where M is the magnetization and H the magnetic intensity.

54. Diamagnetism It is Lenz law at atomic level The material charges in movement tend to cancel the effect of the variation of the magnetic flow (applied external field) magnetic susceptibility < 1

55. Examples of diamagnetic substances: water lead so di um chloride quartz sulphur diam o n d gra phi te li quid nitrogen copper = -9,8 × 10 −6

56. Interesting effects: From: http://en.wikipedia.org/wiki/Diamagnetism

57. Paramagnetism The presence of a n external magnetic field produces a torque that tends to line up the magnetic moments in the same direction of the field.

58. Examples of paramagnetic substances sodium aluminium = 2,3 × 10 −5 copper chloride nickel sulphate Liquid oxygen

59. Ferromagnetism Ferromagn e tic materials have a permanent magnetization atoms with electrons not pair uped whose spins are guided in the same direction It generates regions called DOMAINS

60. Ferromagnetic materials examples Iron = 5.500 Magnetite (Fe 3 O 4 ) Cobalt Nickel Gadolinium

61. FERROMAGNETISM Magnetic Domains

62. Magnetic Domains The domains are delineated with colloidal iron oxide particles FOTOMICROGRAFY (Bell Telephone Laboratories) From: http://www.feiradeciencias.com.br/sala13/13_38.asp

63. “ Estructura de dominios magneticos en laberinto observada mediante microscopia Bitter en una cinta amorfa de base Fe ” MICROSCOPY From: http://www.icmm.csic.es/eng/gallery/gall_omtp.htm

64. CURIE TEMPERATURE Ferromagn e tic materials acquire paramagnetic behavior. Alignment with external field 16 o C Gadolinium 358 o C Nickel 1131 o C Cobalt 770 o C Iron Curie point Element

65. Hysteresis loop It determines the characteristics of a magnetic material. It is the graph of magnetization M of the material in function of the external magnetic field applied H.

66. Hysteresis Loop It shows how much a material magnetizes under the influence of a magnetic field and how much of magnetization remains in it after the field is off.

67. Hysteresis Loop From: http://hyperphysics.phy-astr.gsu.edu/Hbase/solids/imgsol/hyloop.gif

68. Definitions: From: http://hyperphysics.phy-astr.gsu.edu/Hbase/solids/imgsol/coercivity.gif

69. Granulars: magnetic nanoparticles dispersed in a solid or liquid medium: Solid: granular solids Liquid: magnetic fluids Magnetic nanostructured systems:

70. Magnetic Behavior Configuration of minimum potential energy Magnetic domains with random orientation size temperature

71. Critical size A set of ten nanometers Random orientation is not energetically favorable **Spontaneous permanent magnetization** SINGLE-DOMAIN

72. Temperature variation: Magnetic nanoparticles small magnets Temperature increase Rotation in the magnetization direction

73. Thus... Magnetic moment direction change constantly Single vector (giant magnetic moment) Quantum force superparamagnetism

74. Thin films Materials of small thickness that can be made with one or more layers

75. Some aplications: Electronic semiconductors devices Optic devices In the ceramic thin films : Coverings against corrosion In the ferromagnetic films: Computer memories

76. Fabrication Techniques Sputtering Chemical vapor deposition Molecular beam epitaxy Sol-Gel process Spin coating Pulsed laser deposition

77. “ Ni grows in a layer-by-layer fashion on Cu(001) with the first monolayer nearly complete before second-layer growth commences. If the substrate temperature is raised to ~450K interdiffusion occurs”. From: http://www.surfaces.lsu.edu/nioncu.html

78. Ph otomicrogra phy of SBN -s trontium b arium n iobate - thin films .

79. From: http://www.liec.ufscar.br/ceramica/index.html

80. Thin films and giant magnetoresistance Thin films: Gradual deposition of atoms in a substract Simple and multilayers [ iron – cobalt – nickel ] [ chromium – copper – ruthenium ] Giant magnetoresistance

81. multilayer Transmission Electron Microscopy on an Fe/Si multilayer (photo courtesy of EPFL) From: http://www.gencoa.com/tech/f_multilayer.html

82. Giant Magnetoresistance: Discovered in 1988. Thin films multilayer structures intercalating iron and chromium.

83. Experiment: Mesure of electrical resistance of the system for different applied magnetic fields.

84. Results: When the ferromagnetics layers are with contrary alignment Device shows high electric resistance When the ferromagnetics layers are with paralel alignment The resistance falls, around 40% to 50%

85. Applications of the giant magnetoresistance effect: Magnetic writing Spintronics

86. Investiments From: http://nano.gov/ e http://www.mct.gov.br/ US$milions

87. T H E E N D !