Micky Holcomb Condensed Matter Physicist West Virginia University

1. The Physics of Faster, More Energy-Efficient Computers Micky Holcomb Condensed Matter Physicist West Virginia University http://community.wvu.edu/~mbh039/ mikel.holcomb@mail.wvu.edu

2. Who cares about Physics? Why would one study Physics?

3. The Physics of Cell Phones Power Switch Finding Signal Physics is responsible for the components in your phones and computers. GPS & WiFi Power Amplifier Runs the Screen Battery Connector Camera Audio & Charging Keeps Time The internet (formally the NSFnet*) is due to basic science funding. Memory SIM Card Connection to Other Devices Backup Battery *http://en.wikipedia.org/wiki/NSFNET

4.  Physics Helps Makes Life Better We learn about the basic products of nature and learn how to make some beefy devices.

5.  Computers Have Progressed

6.  Physics Makes Faster Computers

7. What is Electricity? In some materials, these electrons move freely under an applied voltage.

8. What is a Transistor? Time Transformative Changing Variable Resistor Resistor http://www.youtube.com/watch?v=CkX8SkTgB0g

9. Improving Transistors The number of transistors placed inexpensively on a computer chip has doubled every ~2 years (Moore’s Law) This trend has allowed massive progress in technology

10. 1) Making Them Smaller A voltage on the gate electrode can induce flow of electricity between the two other contacts called the source and drain. Area Speed Area Electron flow Thickness Electron flow Silicon The flow of electricity is affected by: the dielectric constant of the oxide, the areaof capacitor and the oxide thickness

11. Quantum Tunneling?!? Electrons are lazy! If the hill isn’t too wide, they tunnel through it. Not good.

12. 2) Replacement Oxides • High dielectric constant • Low leakage current • Works well with current Si technology • Many materials have been tried but none are as cheap and easy to manipulate as existing SiO2.

13. 3) Strain Industry found that it could improve electron travel in MOSFETs by straining (essentially squeezing) silicon. Strain can allow quicker, more efficient transfer of electrons. Strain can also affect other properties of a material.

14. Why We Care About Strain Ex: roads, airplane wings, medical inserts, building materials

15. Reaching the Limits 1) Scaling 2) Replacements 3) Strain We are reaching the limit that these strategies can continue to improve technology.

16.  4) Different Approach: Magnetism Magnetic moment electrons

17. Using Magnetism 0 0 1 Problems with Magnetic Fields Require a lot of power Heating problems Difficult to localize – limits size Magnetic field

18. 4) Different Approaches Multiferroic Ferromagnetic Ferroelectric Spontaneous polarization whose direction can be changed with an applied electricfield (voltage) Spontaneous magnetization whose direction can be changed with an applied magnetic field

19.  Bi Fe O P1+ 71° 180° P3- P1- 109° P4- Electrical Control of Magnetism? Only room temperature magnetic ferroelectric (BFO) Using an electric field to change magnetism Magnetic plane is perpendicular to the polarization direction.

20.  Physics at its Boundaries - BFO is not a good candidate - Simple idea: Grow a magnetic material on top of a ferroelectric Boundary - Problem: the physics at boundaries is not yet well understood

21. Magnetoelectric Interface Laser Molecular Beam Epitaxy (Laser MBE) A – Magnetic layer (LSMO) B – Ferroelectric layer (PZT) C – Substrate LaSrMnO3 PbZrTiO3 SrTiO3 Programmable shutter Chu YH, et. al., Materials Today 10 (10), 16 (2007)

22. Visualizing the Nano We study structures that are only several nanometers in length. 1 inch = 2.5 cm = 25 million nanometers (nm) Penny = 0.06 inches thick (or 1,550,000 nanometers) Human hair = 100,000 nm wide Nanometer objects are too small to see with our eyes. Scientists must use powerful microscopes to image objects this small.

23. Our “Laser” Femtosecond pulses, one million times smaller than nanoseconds! Power of a laser pen: 5 mW Power of our lab’s laser: 1500 mW Paper will burn at 95 mW

24. Cooling Down the Physics Cryostat Antarctica reaches temperatures of -129°F Capable of reaching temperatures of -450°F This is just above ABSOLUTE ZERO, the coldest possible temperature. Other cool features: Low vibration stage Sample rotation

25. Measurements Elsewhere Experiments At National Labs: X-ray Dichroism Photoemission Electron Microscopy (PEEM)

26. X-ray Production electrons Sample X-rays electrons Collector 150 Feet X-rays excite electrons which tell us about many properties of the material Beam of electrons forced by magnets to go around in circles

27. Electric Control of FM As grown Second E switch First E switch

28. Summary Magnetic Ferroelectric Basic physics research has allowed significant progress in computing and other modern day technologies. As computers continue to get smaller, the physics becomes more interesting. Multiferroic materials offer a pathway to new properties/devices. Magnetic and ferroelectric materials can be imaged and studied at WVU and national laboratories. Magnetic domains can be changed by an electric field.

29.  Our Science Superheroes A few of my collaborators: Left to Right: SrinivasPolisetty (post-doc), Disheng Chen (grad), Jinling Zhou (grad), Evan Wolfe (undergrad), Micky Holcomb (advisor) and Charles Frye (undergrad) National Chiao Tung University (Taiwan)