Material physics - University of Virginia

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Material physics - University of Virginia

MATERIALS PHYSICS WITH COMPACT

ELECTRON LINAC

• Condensed Phase Studies

• Gas Phase Studies

Bellave Shivaram

Condensed Matter Physics

University of Virginia


What is it that is important in Condensed Matter ?

• Structure

• Broader Definition – Not just physical structure

Probes

• Light (photons)

• Electrons

• Positrons

• Neutrons


Discussion of my own work

• Growth of Nanoparticles and “Nanosystems”

• Spectroscopy of New Thin Film Materials

• Structure in k-space


Synthesis of Nanoparticles - PLD

V, Nb, Sm-V, Nb-Al etc.


V nanoparticles grown at various Ar

gas pressures.

GaAs Nanoscale

Heterostrcutures


Bonding of single Ti to C 2 H 4 – no

energy barrier.

First H 2 adsorbed dissociatively

Add 4 more molecularly

H-H ~ 0.85 A


Adam’s

experiments

Ti and other

TM ablated

by laser in a

UHV chamber

in the

presence of

ethylene

(C 2 H 4 ).


CON-CURRENT IMPORTANT WORK AT UVa

Prof. Lester Andrews’ Laboratory - Chemistry

Xuefeng Wang, Lester Andrews,Ivan Infante, and

Laura Gagliardi, J. AM. CHEM. SOC. 2008, 130, 1972-

1978.

Wt% ~ 8/188


Other characterization experiments.

TEM characterization – Ti(C 2 H 4 )

Gas phase characterization

Ti (C 2 H 4 )

76 amu


HRTEM & EELS Spectra – Ti(C 2 H 4 ) Complex

OUTSIDE THE PARTICLE

INSIDE THE PARTICLE


Pressure Dependence of H 2 Uptake

Ni – C 2 H 4

T.E.M. indicates that

nanoparticles (and

hence clustering of

metal atoms) are formed

for ablations at ethylene

pressures above 100

mtorr.

Ti –C 2 H 4

Reduced hydrogen

uptake is consistent

with cluster formation.


Structure in k-space

UPt 3

m* ~ 1000 m e

YBaCuO – High Tc

Science -2008


Other Possibilities – Based on Interests of Other Faculty

• “Artificial” and “Natural” Materials

• MBE grown thin film heterostructures

• Metamaterials

• Excitations in Superconductors

• Excitations in Spintronic Materials

• Molecular Conductors


ACKNOWLEDGEMENTS

• A. B. Phillips (U. Toledo)

• G. Myneni (JLab)

• Lester Andrews (UVa)

• David Hinks (Argonne)

• Stu Wolf (UVa)

• Mitsu Murayama (UVa)

• Taner Yildirim and Wei Zhou (NIST)

• Tom Anuniwat (UVa)

• Anjali Manivannan (CMU)


Exposing nanoparticles to air does not destroy the original

crystal structure

GaAsSb alloy

nanoparticles, 550

0

C.

0.7 J/cm2 to 1.6

J/cm2 and 600 to

900 pulses.


Pulsed Laser Deposition Apparatus


H-H Bond distances

• Continuous range possible

• Another way to characterize the “ideal” storage material


Kubas Complex - 1984

LIGAND

Some 562 of these “complexes” are known

today

What is a

“complex”?

In all of them only 1 H 2 is reversibly absorbed – with the

exception of one where 2 H 2 molecules participate…

SPECIAL BRANCH OF ORGANO-METALLIC

CHEMISTRY


How do we know it really is hydrogen (H 2 ) that is getting in ?

Independent exposure to D 2

indicates doubling of mass

accumulated on sensor.


Hydrogen Absorption in Transition Metal – Benzene (Ring) Complexes

Benzene predicted to absorb ~ 6%

by weight of hydrogen (Wecka et.

al., J. Phys. Chem., 2008)

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