Advanced diffusion studies with isotopically controlled materials

Abstract

The use of enriched stable isotopes combined with modern epitaxial deposition and depth profiling techniques enables the preparation of material heterostructures, highly appropriate for self-and foreign-atom diffusion experiments. Over the past decade we have performed diffusion studies with isotopically enriched elemental and compound semiconductors. In the present paper we highlight our recent results and demonstrate that the use of isotopically enriched materials ushered in a new era in the study of diffusion in solids which yields greater insight into the properties of native defects and their roles in diffusion. Our approach of studying atomic diffusion is not limited to semiconductors and can be applied also to other material systems. Current areas of our research concern the diffusion in the silicon-germanium alloys and glassy materials such as silicon dioxide and ion conducting silicate glasses. * corresponding author IntroductionThe diffusion of atoms in materials is a fundamental process of mass transport that is important for numerous applications. For example, doping of silicon is often performed by the diffusion of the desired foreign-atom into the material. The current standard of very shallow dopant profiles of only a few tenths of nanometers by ion implantation requires a strong control of diffusion and reaction processes in order to minimize transient-diffusion effects [1]. With the down-scaling of Si-based electronic devices, interfaces are becoming more significant and can affect the diffusion in the bulk material of interest. In this context, the reactions occurring at the SiO 2 /Si interface are very important in order to understand the oxidation process of Si and the ability of the interface to act as a source of point defects. The large scale production of electronic and optoelectronic devices based on group III-V compound semiconductors also requires highly reproducible doping processes. To meet this requirement the reason for the often observed complicated shape of dopant profiles in compound semiconductors must be understood. These examples illustrate that a comprehensive understanding of the mechanisms of dopant diffusion and the properties of native point defects in the underlying material, which includes their generation, recombination and interaction with dopant atoms, are of fundamental significance for controlling the fabrication of electronic devices.

Diffusion and Point Defects in Silicon Materials

“…With the availability of isotopically controlled semiconductor multilayer structures, advanced diffusion studies became possible that provide more detailed insight on the diffusion mechanisms and properties of defects involved than earlier studies [64,76,140]. The advantage of isotopically controlled semiconductors for diffusion studies is demonstrated by experiments and simulations of the simultaneous diffusion of self-and foreign-atoms in isotope multilayer structures.…”

Lithium Diffusion in Ion-Beam Sputtered Amorphous LiAlO2

“…In the present study we used 6 LiAlO 2 / 7 LiAlO 2 isotope hetero-structures for analysis. This is a reliable method to study self-diffusion processes in solids because pure isotope interdiffusion takes place undisturbed by chemical gradients [17][18][19][20][21][22].…”

Self-Diffusion of Lithium in Amorphous Lithium Niobate Layers

“…In the present study we used 6 LiNbO 3 / 7 LiNbO 3 isotope hetero-structures for analysis. This is an extremely reliable method to study self-diffusion processes in solids because pure isotope interdiffusion takes place undisturbed by chemical gradients [16][17][18][19][20].…”