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Materials Science and Engineering Aspects of Nanostructures and Nanomaterials. Gottlieb S. Oehrlein Department of Materials & Nuclear Engineering & Institute for Research in Electronics and Applied Physics University of Maryland, College Park, MD 20742‑2115 *oehrlein@glue.umd.edu.

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materials science and engineering aspects of nanostructures and nanomaterials

Materials Science and Engineering Aspects of Nanostructures and Nanomaterials

Gottlieb S. Oehrlein

Department of Materials & Nuclear Engineering

& Institute for Research in Electronics and Applied Physics

University of Maryland, College Park, MD 20742‑2115

*oehrlein@glue.umd.edu

nanoscience and nanomaterials
Semiconducting (electronic, optoelectronic, etc.)

Magnetic

Dielectric

Metallic

Organic

Biological

Synthesis of nanoscale clusters, nanocrystalline materials

Self-assembly

Nanoscale materials characterization

Functional materials

Combinatorial synthesis

Biomimetic approaches

Top-down nanostructure fabrication, sensing, control

Nanoscience and Nanomaterials

Research Topics

Materials

nanoscience and nanomaterial activities
Mohamad Al-Sheikhly (DNA selfassembly on semiconductors and insulators)

Sreeramamurthy Ankem (Ti alloys, biocompatibility, nanoscale surface modifications)

Robert Briber* (organic nanomaterials + characterization)

Aris Christou* (inorganic selfassembly)

John Kidder* (chemical vapor deposition, nanoscale particles)

Peter Kofinas* (selfassembly of organic, templating)

Isabel Lloyd (sintering of nano particles)

Luz Martinez-Miranda (liquid crystals, nanoscale characterization)

Gottlieb Oehrlein* (plasma processing of nanomaterials and nanostructures)

Nanoscience and Nanomaterial Activities
  • Ray Phaneuf* (nanoscale characterization)
  • Ramamoorthy Ramesh* (magnetic oxides, nanoscale selfassembly, functional materials)
  • Gary Rubloff (nanoscale fabrication, sensing and control)
  • Alexander Roytburd (strain modeling of nanomaterials)
  • Ichiro Takeuchi (combinatorial synthesis)
  • Lourdes Salamanca-Riba* (characterization of nanoscale structures and materials)
  • Otto Wilson, Jr. (biomimetic approaches to novel materials)
  • Manfred Wuttig (functional materials, phase transformations in nanocrystals)
  • Examples of research will
  • be discussed in this talk
nanotechnology and nanomaterials
Nanotechnology and Nanomaterials
  • Nanoscale Characterization
  • Selfassembly
  • Organic nanomaterials & templating
  • Processing of nanomaterials & novel effects
  • Top-down nano-lithograpy - formation of nano-scale structures and devices
scanning tunneling microscopy and spectroscopy characterization of electronic devices phaneuf

Preamp

x y z actuator

STM

ADC/DAC interface

Vp

Summing # 1

p

Lock-in amp

n

Mod’n voltage

Depletion

zone

Summing # 2

Vn

0V

-10V

Vr

Scanning Tunneling Microscopy and SpectroscopyCharacterization of Electronic Devices - Phaneuf

Topography and Conductance Images of pn devices on Si under variable reverse bias

slide6

Tunable PbSe QD Superlattices with PbEuTe Spacer Layers Obtained by MBE - TEM Characterization Salamanca-Riba, Springholz, Bauer (Linz, Austria)

  • PbSe (IV-VI) Q.D. / Pb1-xEuxTe* superlattice on PbTe (111) for mid-IR lasers and detectors, thermoelectric materials
  • Exploit:

Tensile strain for PbSe Q.D.

  • (5.5% mismatch between PbSe & PbTe)
  • PbSe; 6.124Å PbTe; 6.443Å Pb1-xEuxTe (x=0.07); 6.467Å
  • High elastic anisotropy

L

  • MBE growth
    • S-K growth mode
    • Deposit 5 PbSe ML / dot
  • Variables;
  • - Spacer thickness (32-312nm)
  • - Growth temperature
  • (335oC, 380ºC)
  • Analysis
  • - TEM: Shape and size of buried dots
  • Dot stacking
  • - AFM: Shape and size of surface dots

PbSe

PbSe

Pb1-xEuxTe Spacer*

N

periods

PbSe

Pb1-xEuxTe Spacer*

D

PbSe

PbSe

PbTe buffer layer (2µm)

wetting

layer

BaF2 (111)

L: in-plane dot-to-dot distance

D: Spacer layer thickness

* x = 0.05 ~ 0.1

slide7

(b) Pyramid shape Q.D.s

(base=30nm, height=12nm)

for 35nm<D

Tunable PbSe QD Superlattices with PbEuTe Spacer Layers Obtained by MBE - TEM Characterization Salamanca-Riba, Springholz, Bauer (Linz, Austria)

1st. Q.D. layer

60th Period Q.D.

(a) In plane dot distributions for

35nm<D<69nm

slide8

Tunable PbSe QD Superlattices with PbEuTe Spacer Layers Obtained by MBE - TEM Characterization Salamanca-Riba, Springholz, Bauer (Linz, Austria)

43 nm spacer layer thickness

electron beam

Dots are placed at the minimum elastic energy density position

with respect to the dots of previous layer

3 d schematic of pseudo fcc unit cell
3-D Schematic of Pseudo fcc Unit Cell

Tunable PbSe QD Superlattices with PbEuTe Spacer Layers Obtained by MBE - TEM Characterization Salamanca-Riba, Springholz, Bauer (Linz, Austria)

where

L : closest dot-dot distance

D : the spacer thickness

 : the trigonal angle (39º)

14% compressed

along the trigonal direction

inas self assembled quantum dots qd for nano lasers christou
InAs Self Assembled Quantum Dots (QD) for Nano-LasersChristou
  • InAs/InAlAs/InGaAs on (110) InP
  • Quantum Dots via Self Assembly
  • Cathodoluminescence spectra at 10-13 meV FWHM
  • Excitonic Transitions via PL.
spontaneous assembly of pdo2 tips for field emission applications ramesh

AFM

SPONTANEOUS ASSEMBLY of PdO2 TIPS FOR FIELDEMISSION APPLICATIONS - Ramesh

Formed by oxidation

of metal film

50x50mm

PEEM

slide12

Nucleation and Morphology Evolution in Chemical Vapor Deposition -Praertchoung, Kidder

In ULSI devices, Nano-Scale Morphology and Surface Features are Critical

Atomic force microscopy images of Ta2O5 thin films grown on Si(100) by chemical vapor deposition.

Early stage of nuclei formation detected after 5 min, followed by coalescence and roughening.

NEXT STEP

Atomic Layer Deposition technique will be studied for control of nucleation and surface morphology.

1 min

5 min

5 nm islands

10 min

15 min

Work supported by University of Maryland - NSF - MRSEC  (NSF-DMR-00-80008)

block copolymer nanotemplates kofinas
Blocks of sequences of repeat units of one homopolymer chemically linked to blocks of another homopolymer sequence.

Microphase separation due to block incompatibility

Templates for synthesis of metal and metal oxide nanoclusters

A-Block

B-Block

Chemical Link

0 - 21 %

21 - 34 %

34 - 38 %

38 - 50 %

Increasing Volume Fraction of Minority component

Block Copolymer NanotemplatesKofinas
metal oxide nanoclusters kofinas
Metal Oxide NanoclustersKofinas

Mixed Metal Oxide Magnetic Nanoclusters

Piezoelectric Nanoclusters

  • CoFe2O4
    • Hard magnetic material
    • High coercivity
    • Moderate saturation magnetization
    • Can be used for high density memory devices
  • ZnO
    • Wide band gap semiconductor (3.3eV)
    • Electro-acoustic devices (Piezoelectric)
    • Conductive layer in solar cells
    • UV emitter
    • pressure sensors for tires
slide15

Nanoporous PMSSQ Synthesis Schematic

Dielectric constant vs. porogen content

Nanoporous Dielectrics by Polymer TemplatingBriber, R.L. Miller, E. Huang, P. Rice (IBM Almaden Research Center)
  • Objective:
  • Characterize nanoporous low k dielectrics for next
  • generation interlayer materials
    • Nanoporous dielectrics are synthesized from poly(methylsilsesquioxane) (PMSSQ) by templating the pore structure with polymers (termed porogens). A mixture of MSSQ and porogen is spin cast, cured and heat treated (450°C) to degrade the porogen and form the pores.
    • A nanoporous structure will lower the dielectric constant (of PMSSQ).
    • The morphology of the pores (size, shape, connectivity) will control many properties of the materials.
  • Approach:
    • Use TEM, neutron scattering and neutron reflectivity to determine the pore structure.
    • Small angle neutron scattering to follow the evolution of pore structure in-situ using deuterated porogen polymer.
slide16

TEM Results (FIB sample preparation):

Nanoporous films are formed by degradation of the porogen. A percolation transition from isolated to interconnected pores is observed at ~30% porogen content. Pore size/spacing is 6-25nm (depending on synthesis details).

SANS Results: Structural evolution is observed during cure from low temperature (green curve) to high temperature (blue curve). Upon degradation of the porogen and formation of the pores the scattering intensity is lost (open black triangles) because of the small neutron scattering contrast between the pores and the matrix.

Nanoporous Dielectrics by Polymer TemplatingBriber, R.L. Miller, E. Huang, P. Rice (IBM Almaden Research Center)
plasma based pattern transfer into nanoporous silica oehrlein standaert ibm gill plawsky rpi
Plasma-Based Pattern Transfer into Nanoporous Silica – Oehrlein, Standaert (IBM), Gill, Plawsky (RPI)

50 sccm,

10 mTorr,

1400 W

plasma based pattern transfer into nanoporous silica oehrlein standaert ibm gill plawsky rpi18
Plasma-Based Pattern Transfer into Nanoporous Silica – Oehrlein, Standaert (IBM), Gill, Plawsky (RPI)

CHF3(50 sccm, 10 mTorr, 1400 W, -125V, 40 sec)

  • Fairly satisfactory pattern transfer
  • Low etch selectivity relative to SiN etch stop layer

Photoresist

Xerogel

Si3N4

Etch Stop Layer

plasma based pattern transfer into nanoporous silica oehrlein standaert ibm gill plawsky rpi19
Plasma-Based Pattern Transfer into Nanoporous Silica – Oehrlein, Standaert (IBM), Gill, Plawsky (RPI)

50 sccm,

10 mTorr,

1400 W

plasma based pattern transfer into nanoporous silica oehrlein standaert ibm gill plawsky rpi20
Plasma-Based Pattern Transfer into Nanoporous Silica – Oehrlein, Standaert (IBM), Gill, Plawsky (RPI)
  • More CFx material on porous silica than on SiO2
  • Porous silica etch rate is suppressed as CFx material builds up

Schematic

Picture of

Surface

Rc=SiO2/nanoporous silica

etch rate ratio

fabrication of ferroelectric nano capacitors ramesh melngailis ece ireap
Fabrication of Ferroelectric Nano-capacitorsRamesh, Melngailis (ECE/IREAP)

Ferroelectric materials exhibit a broad range of valuable physical properties they exhibit, with potential applications in information storage technologies. To be competitive, ferroelectric memories have to be implemented at densities of the order of 1Gbit on a 1cm x 1cm chip. This necessitates the reduction in the lateral dimensions of the storage element into the sub-micron range. For example, it is expected that a Gbit chip will have storage capacitor areas of the order of 100nm x 100nm, in a planar arrangement.

fabrication and characterization of nanoscale wires oehrlein kuan suny rossnagel ibm
Fabrication and Characterization of Nanoscale WiresOehrlein, Kuan (SUNY), Rossnagel (IBM)
  • Electron-beam lithography of PMMA resist
  • High-density plasma etching of 20-50 nm wide trenches in SiO2
  • High-density plasma deposition of Cu
  • Removal of excess Cu by chemical mechanical planarization