September 1993 DISCOVER 1

T H E F L A T F A C E O F T E C H N O L O G Y

P H O T O G R A P H S B Y M I C H A E L W . D A V I D S O N

September 1993 DISCOVER 2

Welcome to the technology of flatland. Researchers around the world are discovering ways to create

thin films of chemicals, some only a few atoms thick, that can do many things no other substances can.

Some are semiconductors that can be made into computer chips. Others have special magnetic proper-

ties that let them act as memory storage systems. Others are superconductors-they carry electric

cureent without any resistance. And some thin films can make a knife edge as hard as a diamond. To

make a thin film, engineers fire a high-temperature beam of molecules (900 degrees Fahrenheit) into a

vacuum chamber. The beam hits the surface of a wafer made out of silicon, silicon compounds, lantha-

num aluminate, or another similiar material. If the conditions are right, the molecules from the beam

organize themselves into a crystal. Getting the conditions right is no small task.

First, the wafer’s suface has to be made of a perfect crystal similar to the one molecules will form on

top of it. (Since the structure of the crystal on the wafer pulls the falling molecules into its own order,

a hexagonal crystal on the surface could not produce a thin film with a square crystal.) Next, the

molecules have to spread evenly over the surface in a thin, perfect layer. And finally, the newly formed

thin film has to cool down without last-minute crumpling. Perfect thin films are as smooth and feature-

less as well-made mirrors. Imperfect films (like all the films in these photographs, taken at a magnifi-

cation of 100 to 1,500 at the National High Magnetic Field Laboratory) are of no practical use, but they

give engineers crucial hints for future efforts, such as which materials are the most likely to produce

successful results and which techniques for deposting the chemicals on the surface work best. And

flawed films give all of us a beautiful look at a strange two-deminsional world.

I N T H E M Y S T E R I O U S N E W W O R L D O F M O L E C U L A RA R C H I T E C T U R E , Y O U A B S O L U T E LY C A N N O T B E T O O T H I N .

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m o u n t a i n s o f b u c k y b a l l s

Researchers have discovered that several dozen-carbon atoms can form a single moleculeshaped like a soccer ball. Dubbed buckminsterfullerenes, or buckyballs, they may turn out tobe one of the most versatile substances ever to come out of the lab. They may, for example,be better than silicon for manufacturing semiconductors. Here engineers have coated silverwith a layer of buckminsterfullerenes to examine the proper ties of buckyball thin film. If thisone were smooth, it would be perfect, but its surface is flawed.

September 1993 DISCOVER 3

a t o m i c j e w e l s

The triangles in this picture are miniature diamonds, engineers created them bysowing carbon atoms on a surface of silicon carbide, where they grew intointerlocking tetrahedrons (pyramids with a triangle for a base). Diamond filmsmay soon be turned into unbreakable coatings and computer chips that can workat high temperatures. In a perfect diamond coating, the tetrahedrons would bethe same size and would line up with one another, forming a smooth layer. Herethe crystals have grown at different rates.

i m a g i n a r y s t a i r c a s e s

A compound called lanthanum aluminate (a combination of lanthanum, aluminum,and oxygen) makes a good foundation for superconducting thin films. A perfectsample is crystal clear, while flaws create patterns such as the staircase shownhere. The light and dark bands aren’t created by shadows; they actually reflectthe light differently, much the way prisms do. If a superconductor is built on suchan imperfect surface, it can handle only a low level of electric current. This film,which was formed at high temperature, cooled too quickly. Since the moleculesdidn’t have enough time to settle into their most comfortable arrangement makinga perfect crystal-flaws became locked into the structure.

September 1993 DISCOVER 4

September 1993 DISCOVER 5

m i c r o s c a p e s

Thin films can trick the eye. This is a stack of alternating nickel oxide and ironoxide layers known as a superlattice. By combining materials with differentmagnetic properties. Researchers can come up with new and unexpectedproperties in superlattices, such as enormously intense magnetic fields that mayturn out to be excellent for computer memory storage. But in this picture thesuperlattice itself, a few dozen atoms thick, is invisible. What looks like anangled photograph of miniature cliffs and ridges is actually a view of cracks inthe surface wafer from directly overhead. They were formed when researcherschiseled the wafer from a larger piece of magnesium oxide.

If the surface wafer doesn’t match the crystal structure of the molecules fallingonto it, the molecules will bond with each other instead, which is what happenedhere. Molecules of nickel oxide have collected on a surface of indium phosphide,but instead of forming a smooth sheet. They’ve bunched up into bubbles. Theresearchers who made this sample are trying to develop new kinds of magneticfilms for storing data in computers.

m a g n e t i c c h a m p a g n e

September 1993 DISCOVER 6