Weizmann Institute scientists develop a significantly improved method for evaluating ultrathin films. Potential benefits include diverse microelectronic applications and a better understanding of chemical and biological systems

New York, NY--September 25, 2000--Ever tried determining what's inside a layered chocolate cake without slicing it? Now, how about tackling a similar task, yet on a nanometer-scale.

For decades, thinking big has frequently meant pursuing smaller and smaller goals. Take ultrathin films for instance. Often less than 10-15 nanometers in width, ultrathin films are used in diverse applications, from optoelectronics to biological sensors. (A nanometer is roughly one 100,000th the width of a human hair.)

A central requirement for performing these Lilliputian feats is accurate composition and structural analysis. Yet, "looking inside" these films, which are often multi-layered, calls for highly sensitive probes. Most available techniques do not provide the depth information essential for evaluating layered structures. Similarly, X-rays offer a spectacular glimpse into the human body; however, determining the relative depth of individual structures is highly difficult. Techniques devised to solve this problem are generally complicated and frequently damage the sample, distorting the results.

Now, Dr. Hagai Cohen of the Weizmann Institute Chemical Services and Prof. Israel Rubinstein of the Materials and Interfaces Department have developed a novel method for evaluating ultrathin films, specifically, non-conducting films on conducting substrates. Recently appearing in Nature, their study builds upon X-ray Photoelectron Spectroscopy (XPS), a common surface analysis technique.

In XPS, the sample is irradiated with X-rays, causing photoelectrons to be ejected. By measuring the photoelectrons' energy, it is possible to determine the atoms from which they originated. Researchers have routinely used
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Contact: Jeffrey Sussman
jeffrey@acwis.org
212-895-7951
American Committee for the Weizmann Institute of Science
24-Sep-2000