Computational Materials at Texas

Professor Jim ChelikowskyRoom 4.324 ACE

Email: jrc@ices.utexas.eduPhone: 2-9083

Web site: http://www.ices.utexas.edu

Personal website: http://tesla.ices.utexas.edu

Background• PhD in Physics from University of California, Berkeley

• Postdoc at Bell Labs

• Exxon Research and Engineering

• University of Minnesota

• University of Texas, arrived January 2005. Positions in Chem E, Physics and Chemistry/Biochemistry

• Research interests: materials science and computational physics

Current Group Members

Postdocs: Tzu-Liang Chan, Amy Khoo, Jaehyeon Eom, and Na Sai (not pictured is Jonathan Moussa.)

Students: Hyunwook Kwak (ChemE), Grady Schofield (CAM), and Jason Han (Physics).

Funding Sources

• National Science Foundation: New Institute for Advanced Electronic Materials

• Department of Energy: Nanoscience

Institute for the Theory of Advanced Materials in Information

Technology

http://www.ices.utexas.edu

Genius is one percent inspiration and ninety-nine percent perspiration!- Thomas Edison

Why do simulation and modeling?

If Mr. Edison didnʼt perspire so much he would get more accomplished! - Nikola Tesla

If Edison had a needle to find in a haystack, he would proceed at once with the diligence of the bee to examine straw after straw until he found the object of his search. [...] I was a sorry witness of such doings, knowing that a little theory and calculation would have saved him ninety per cent of his labor. — Nikola Tesla

Mythbusters:Burn the stack, pickup the needle.

Role of Electronic Materials

Semiconductors have been widely recognized as a key enabler for the new economy described earlier. In a recent study on the economic impact of America's manufacturing industries, entitled "Turbocharging the U.S. Economy," the semiconductor industry was identified as the largest, contributing over 20 percent more to the U.S. GDP than the next largest sector (automobiles).

Circa 1960: Early transistors

Circa 2000: 40 million transistors

SILICON!

DALLAS (May 10, 1954) - A revolutionary new

electronic product--long predicted and awaited--

became a reality today with the announcement by

Texas Instruments Incorporated of the start of

commercial production on silicon transistors. By

using silicon instead of germanium, the initial

commercial silicon transistor immediately raises

power outputs and doubles operating

temperatures! The potential application of this

entirely new transistor is so great that major

electronics firms have been conducting silicon

experiments for some time. -- Press Release

Texas Instruments.

Silicon: 1954

From the Transistor Museum.

• “Gordon Moore made his famous observation in 1965, just four years after the first planar integrated circuit was discovered. The press called it "Moore's Law" and the name has stuck. In his original paper, Moore predicted that the number of transistors per integrated circuit would double every 18 months.” --Intel website

Moore’s Law

Intel is now a “nanotechnology company.”

Examples of Materials of Interest to Intel....

Research Goals:

• Understand properties of electronic materials

• Examine hypothetical or experimentally inaccessible regimes

• Predict properties and new materials

Semiconductor nanostructures

• Reduced size and dimensionality: quantum dots, nanowires (quantum wires), quantum wells.• Quantum confinement: electron (hole) exitations are strongly quantized – Quantum dot: 3D confinement– Nanowire: 2D confinement• Industrial applications: – Unique building blocks in nanoelectronics and photonics.– Device applications: optoelectronics, photovoltaics, thermoelectrics and sensors.

The optical properties of

semiconductors like CdSe

can be tuned to span the

optical region of the

spectrum by varying the

size of the dot. At left, the

dot size ranges from roughly

4 to 7 nm in diameter.

Optical Excitations in Semiconductor Quantum Dots

Colloidal solutions of CdSe quantun dots of different sizes

At small dimensions, electrons experience quantum confinement. This is direct consequence of the uncertainty principle. As electrons become localized their energy increases approximately as the inverse square of the dot radius.

R

Quatum dot of radius R

Quantum calculations can be used to predict electronic and optical properties at the nano-scale as well as other properties. Predictions of these calculations confirm the role of quantum confinement.

Silicon Dot

Nanowires of Semiconductors

Brian Korgel’s group

1 µm1 µm

3 µm3 µm

Ge Si

GaAs GaP

InP nanowire

d

Three layers along [111] direction is enough to converge the optical gap to 0.01 eV for pure dot.

Energy gaps of quantum dots and nanowires: 3D versus 2D confinement

Quantum confinement in the InP quantum dots is stronger than than

in the nanowires.

Active Projects• Electrical transport in nanoscale devices• New materials for spintronic applications

• Evolution of doping properties in nanocrystals and nanowires

• Magnetic materials

• Developing new algorithms for predicting the electronic and magentic properties of materials