Dr. Benjamin Ocko and Professor Moshe Deutsch

From left to right: Dr. Lilach Tamam (BIU), Dr. Ben Ocko (BNL) and Prof. Moshe Deutsch (BIU) at Brookhaven’s National Synchrotron Light Source experimental station where some of the research is carried out.

A research team lead by Dr. Benjamin Ocko from the U.S. Department of Energy’s Brookhaven National Laboratory (BNL) and Professor Moshe Deutsch of the Department of Physics from Bar-llan University (BIU) have discovered a way of making thin organic-molecule films so that they remain solid at temperatures at which the bulk material is molten. This BSF-supported research was carried out together with Dr. Diego Pontoni and Professor Harald Reichert from the European Synchrotron Radiation Facility in France.

“As we discovered in a previous study, also supported by the BSF, the free surface of a molten sample of alkanes and related materials undergoes an intriguing ‘surface freezing’ effect in which the surface layer remains frozen at temperatures well above that at which the bulk material melts,” Professor Deutsch pointed out. This contrasts with most other materials, in which the free surface would start to disorder, and eventually melt, at a temperature at which the bulk remains solid. “The reason why ‘surface freezing’ occurs only in alkanes (waxes) and their derivatives, remains somewhat of a mystery,” added Dr. Ocko.

As these researchers recently reported in the leading journal Physical Review Letters, surface freezing in the form of a thin molecular layer can also be induced at the interface between a liquid and a solid surface. Dr. Ocko described such films as “better ordered and smoother than all other organic monolayer films created to date.” These experimental results and the theoretical framework developed to explain them are expected to lead to new ideas on how to make defect-free, single­ molecule-thick films, which are of great importance for a wide range of applications in nanoscience, electronic devices, organic solar cells, and biosensors.