The Applications of Nano Materials

1. The Applications of Nano Materials Department of Chemical and Materials Engineering San Jose State University Zhen Guo, Ph. D.

2. How to study Nanomaterials Part I -- Done Basic Materials Science Principles Microstructure Materials Properties Applications Processing Part III Part II – This one

3. Nano Structure and Device • Nano structure and device can be accomplished by two approaches. • -- “Bottom Up” method where small building blocks are produced and assembled into larger structures. • examples: chemical synthesis, laser trapping, self assembly, colloidal aggregation, etc • -- “Top Down” method where Large object are modified to give smaller features. • examples: film deposition and growth, nano imprint / lithography, etching technology, mechanical polishing

4. Technology and Characterization • of Nano Material Science • Session VI: Nano Technology: Bottom Up Approach • Session VII: Nano Technology: Top Down Approach • Session VIII: Nano Material Characterization

5. Session VI – Nano Materials Synthesis Nano metallic particle synthesis Nano semiconductor materials synthesis Carbon based nano structure synthesis Self assembly nano materials Challenge: The control of nano particle sizes, distributions and their locations

6. Nano Metallic Magnetic Particles • Nano metallic particles include single metals mainly transition metals, alloyed metals and metal oxide nano particles • The applications of metallic nano particles are: • -- High density magnetic data storage • -- Dilute magnetic semiconductor (DMS) • -- Biomedical applications (MRI, NMR, SQUID) • -- Highly active catalyst (large surface area) • -- Nucleus for CNT and other nano tube

7. Synthesis of Single Metal MNP-- Method I: The Reduction of Metal Salts • Size control: conducting the reaction in a confined reactor • Nano confined reactor such as water-in-oil or oil-in-water micro-emulsion system • Size of confined space can be defined by varying amount of both surfactant and solvent • Successful examples included Fe, Ni and Co particles Courtesy from Vincent Rotello, Nanoparticles

8. Synthesis of Single Metal MNP-- Method II: Thermal Decomposition • Thermal Decomposition of organo-metallic complexes can produce highly mono-disperse nano particles. • Size and dispersity control is attained through high reaction temperature • Capping ligands (e.g. Oleic Acid) can also mediate the particle growth by forming a monolayer of nano particles • Most common precursors: Metal Carbonyl complexes. • Morphology can also be controlled through various capping ligands TOPO: Trioctylphosphine Oxide Courtesy from Vincent Rotello, Nanoparticles

9. Alloyed Metal Nano Particles • Solid-solution alloyed metallic nano particles can be attained through simultaneous thermal decomposition • Core-shell alloyed nano particles are produced by a stepwise reduction process where each successive step uses larger diameter water droplet to yield the alloyed core-shell particles Courtesy from Vincent Rotello, Nanoparticles

10. Metal Oxide Nano Particles • Thermal decomposition of metal organic precursors on a hot surface. • The size of the nano particles can be controlled by reaction temperature and / or the ratios of precursor verse capping ligands

11. Nano Silicon Particles Cubic Si Nano crystals are made by PECVD method of injecting a dilute mixture (5% SiH4 and 95% of He) and applying RF power Thermal Evaporation of Si chips and collected nano particles in a cold chamberl

12. Other Nano Silicon Particles • Thermal Evaporation • Sputtering • Laser ablation • Electrochemical Etching with catalyst • Implant (Si, Ge) • Anneal from Si-rich SiOx (self assembly)

13. Semiconductor Compound Nano Particles • High Temperature Organo-Metallic Methods are still the most popular for both III-V and II-VI compound. • Thermal decomposition • Rapid injection of organometallic precursor means fast nucleation. • The following growth can be controlled and terminated by adjusting temperature

14. Carbon based nano structures Bucky ball Carbon nano tube http://www.nccr-nano.org/nccr/media/gallery/gallery_01/gallery_01_03

15. Why Ball and Tube Shape? • In Nano Material Science, high surface and even edge energy matters. • As we previously discussed, a tiny piece of graphite would have a lot of atoms at its edge which is unstable. • Giving opportunities, nano solids would roll them self up to bucky balls or tubes to minimize the total energy http://nanonet.rice.edu/intronanosci/sld005.html

16. Making Buckminsterfullerene • Carbon Arc Experiments • -- Two Carbon robs arcing in He at 100 Torr. • -- Can now be reproduced in gram level at a time • First discovered in 1985, it is most known nano particles • The round cage like structure of the fullerenes was reminiscent of the dome structures designed by the architect Richard Buckminster Fuller, and so it was named Buckminsterfullerene

17. Mechanisms of Carbon Nano tube • Root Growth Mechanism: • Transition metal as catalyst • Hydrocarbon dissociate at metal surface into H and C. • Once surface saturated with C, it starts to form as graphite sheet with fullerene cap • More C atoms can be inserted into Metal-C bond so the tube get growing longer. Courtesy from Rainer Waser Nano-electronics and Information technology

18. Synthesis Methods for CNT • Electric Arc Discharge: similar with the one for Bucky Ball • Laser Vaporization: Graphite target with Co, Ni powders sitting in 1200C furnace and hit by laser pulse. CNT collected downstream at cold finger. • CVD: pre-patterned structure with Fe, Mo nano particles in a tube furnace at 1000C and methane as precursor of carbon • Fullerene recrystallization: depositing Ni and C60 multi-layers and recrystallize at 900C Courtesy from Rainer Waser Nanoelectronics and Information technology

19. Properties of Carbon Nano Tube • There are different ways to roll up the graphite sheet to form carbon nano tube. This configuration is defined as Chirality • The electronic properties of carbon nano tube are determined by its chirality. • It can be semiconductor, semimetals or metals Courtesy from Stanley Wolfe: Advanced Silicon Processing

20. Self Assembly of Carbon Nano Tube as interconnect (Metal) Courtesy from Stanley Wolfe: Advanced Silicon Processing

21. Canbon Nano Tube Semiconductor Single or Multiple Carbon Nano Tube as FET Channel Courtesy from Stanley Wolfe: Advanced Silicon Processing

22. Self Assembly Nano Technology • Self assembly can be defined as a coordinated actions of independent entities under local control of driving forces to produce a large, ordered structures or to achieve a desired group effect. • The driving force of self assembly is usually based on an interplay of thermodynamics and kinetics. -- Chemically Controlled Self-assembly -- Physically Controlled Self-assembly -- Flip-up Principles and Spacer Techniques

23. Chemically Controlled Self Assembly Deposition of loaded diblock copolymer micelles • One block is soluble in toluene and the other is insoluble. • Spherical micelles of copolymer molecular are formed in toluene • These micelles are loaded with compounds such as HAuCl4 and deposited on planar substrate. • Oxygen plasma treatment pyrolyses the polymer and turn precursor into nano Au particles with short range regular pattern Courtesy from Rainer Waser Nano-electronics and Information technology

24. Hybrid approach for self assembly • A template with holes is created using typical lithography • The deposition process of the micelles is controlled that only those micelles into grooves and holes by caterpillar force will remain on the surface after resist removal. • Copolymer is pyrolysed and a regular Au dot array obtained Courtesy from Rainer Waser Nano-electronics and Information technology

25. Why Nano Gold Particles? The optical applications of nano materials

26. Hybrid Approach (II) • A diblock copolymer solution were spin-coated and annealed to promote phase separation into nano scale polymer domains. (Polystyrene and PMMA) • One phase is removed with an organic solvent, leaving a porous PS films. • This highly ordered porous film serve as hardmask to etch into Oxide. • Conformally deposit a:Si and etch them using an anisotropic RIE process. • Annealing to form Si Nano crystal array as floating gate Courtesy from K. W. Guarini et al, IEDM 2003

27. Physically Controlled Self Assembly • Film deposition method using Stranski Krastanov Growth. Followed by initial layer by layer growth, island-like nano dots are formed to reduce the elastic strain energy (see next session) • This technique can also combined with Lithography. Layer 2 can be conventionally patterned. Then alternative Layer 1 and 2 deposit can lead to a perfect SiGe islands at specific location. Courtesy from Rainer Waser Nano-electronics and Information technology

28. Flip-up principle and Spacer technique • Flip-up principle utilized the accurate control of film thickness at nm scale during deposition and flip it to vertical dimension • The most known method is spacer technique where a hard mask is deposited conformally over a coarse structure. • Then the film were etched anisotropically leaving only spacer to define nano feature • The next patterning used the spacer as hard mask and thus turn nano-scale controlled film thickness into vertical fine structure Courtesy from Rainer Waser Nano-electronics and Information technology