Direct observation of dopant atom diffusion in a bulk semiconductor crystal enhanced by a large size mismatch.
Diffusion is one of the fundamental processes that govern the structure, processing, and properties of materials and it plays a crucial role in determining device lifetimes. However, direct observations of diffusion processes have been elusive and limited only to the surfaces of materials. Here we use an aberration-corrected electron microscope to locally excite and directly image the diffusion of single Ce and Mn dopants inside bulk wurtzite-type AlN single crystals, identifying correlated vacancy-dopant and interstitial-dopant kick-out mechanisms. Using a 200 kV electron beam to supply energy, we observe a higher frequency of dopant jumps for the larger and heavier Ce atoms than the smaller Mn atoms. These observations confirm density-functional-theory-based predictions of a decrease in diffusion barrier for large substitutional atoms. The results show that combining depth sensitive microscopy with theoretical calculations represents a new methodology to investigate diffusion mechanisms, not restricted to surface phenomena, but within bulk materials.
Materials Science and Technology Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA and Institute of Engineering Innovation, University of Tokyo, Bunkyo, Tokyo 113-8656, Japan.
Ryo
R
Ishikawa
Materials Science and Technology Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA and Department of Physics and Astronomy, Vanderbilt University, Nashville, Tennessee 37235, USA.
Rohan
R
Mishra
Materials Science and Technology Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA.
Andrew R
AR
Lupini
School of Physics, Monash University, Victoria 3800, Australia.
Scott D
SD
Findlay
Advanced Key Technologies Division, National Institute for Materials Science, Tsukuba 305-0044, Japan.
Takashi
T
Taniguchi
Materials Science and Technology Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA and Department of Physics and Astronomy, Vanderbilt University, Nashville, Tennessee 37235, USA.
Sokrates T
ST
Pantelides
Department of Materials Science and Engineering, The University of Tennessee, Knoxville, Tennessee 37996, USA.
Stephen J
SJ
Pennycook