原子状态下实时监控材料表面变化

A team of researchers at Aix Marseille Université in Marseille, France led by Dr. Frédéric Leroy developed a technique that allows them to follow physical processes occurring at surfaces of materials at the atomic level in situ and in real time. This new process allowed the research team to study the kinetics of decomposition of a thin layer of silicon dioxide deposited onto silicon during a thermal treatment, a critical component in micro-electronics. The approach is based on the principles of electron microscopy. Silicon dioxide is one of the most important building blocks of micro-electronics and its thermal stability is critical to device performance. The decomposition of a thin layer of silicon dioxide onto silicon has been the focus of great scientific interest for four decades. Previous studies show that the decomposition occurs non-homogeneously at the surface via the local formation of holes in the oxide layer that extend laterally. Understanding the elementary atomic processes responsible for the opening velocity of these holes is necessary to improve the silicon oxide performance. 

For the research team to achieve a better understanding of nanomaterials properties, advanced characterization tools were needed. 

"We needed to be able to characterize the structural (crystallography, size, shape) and the chemical properties at the same time and to be able to follow in situ and in real time the changes during a given process for a rapid feedback on the experimental parameters," Leroy explained. "Our approach based on low energy electron microscopy is the corner stone of our achievements."

However, even with the new instrument, the team encountered challenges. Obtaining real time measurements of the thermal decomposition of the silicon dioxide was particularly difficult since the complete process occurs in just a few minutes in a narrow temperature window. 

"It was impossible to adjust all control parameters of the electron microscope before the decomposition process started since silicon dioxide is amorphous, so we had to adjust finely the settings within a few seconds as soon as the oxide decomposes in order to characterize the whole process," Leroy explained.