Micky Holcomb Condensed Matter Physicist West Virginia University Micky Holcomb Condensed Matter Physicist West Virginia University Green Your Machine: The Physics of More Efficient Computers and Cell Phones See the notes in the PPT file for ~script.

Progress Through Size 1950s

Shortening the Race = Faster

~ Every 2 years, Twice as many transistors can fit in the same space With the same cost! Doubling (Moore’s Law) 2 12 years later Today, >200 million transistors can fit on the head of a pin! By if trends continue - a device the size of a micro-SD card will have storage of ~ 3x the brain capacity of the entire human race!

What is Electricity? In some materials (metals), these electrons move freely under an applied voltage. Not in insulators.

Silicon In a transistor, a voltage on the metal can induce flow of electricity between the two other contacts called the source (In) and drain (Out). The flow of electricity is affected by: properties of the insulator, the area of A&B and the insulator thickness 1) Making Them Smaller Area Speed Area Electron flow ThicknessElectron flow A B In Out Voltage (C) Insulator Metal

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

Insulating properties (resists electron flow) “Plays nice” with current Si technology (temperature and quality) Many materials have been tried but none are as cheap and easy to manipulate as existing SiO 2. 2) Replacement Oxides

3) Strain Industry found that it could improve electron travel by straining (essentially squeezing) silicon. Strain can allow quicker, more efficient transfer of electrons.

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

 4) Different Approach: Magnetism

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

 Electrical Control of Magnetism - Simple idea: Grow a magnetic material on top of an electric material Materials with strong coupling between electricity and magnetism at room temperature are rare - Problem: the physics at boundaries is not yet well understood

base Modern growth techniques make fabrication of such structures possible! Pulsed Laser Deposition (PLD) Chamber

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

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

Measurements Elsewhere Experiments At National Labs: X-ray Absorption Spectroscopy Photoemission Electron Microscopy (PEEM)

Before First E switch Second E switch Electric Control of Magnetism magnetic layer Average direction Arrows indicant direction of magnetism (0 or 1) Grey (up) Black (right) electric layer underneath

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

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