| AVS 57th International Symposium & Exhibition | |
| Nanometer-scale Science and Technology | Thursday Sessions |
| Session NS-ThM |
| Session: | Nanowires and Nanoparticles |
| Presenter: | S.T. Picraux, Los Alamos National Laboratory |
| Authors: | S.A. Dayeh, Los Alamos National Laboratory S.T. Picraux, Los Alamos National Laboratory |
| Correspondent: | Click to Email |
Progress in the synthesis of semiconductor nanowires has prompted intensive discussions of the science of their growth and the technological applications they promise. Fundamental aspects of their growth have been postulated for nearly five decades for larger diameter nanowires and debated more recently in detailed growth studies for different materials systems. Here, we exploit an extreme level of control over diameter, morphology, and placement in VLS synthesized germanium nanowires to establish systematic size effects on their growth at small diameters, down to sub-10 nm, where quantum effects become relevant. We observe reproducible reduction in Ge nanowire growth rates with decreased diameter coupled to a measured increase in the Ge equilibrium solubility1 for the same wires, validating the role of the Gibbs-Thomson effect in nanowire growth at small diameters. We show how this sets a practical thermodynamic limit on the lowest achievable nanowire diameters (~ 3 nm) and present comprehensive studies of the effects of temperature, pressure, and the introduction of dopant precursors on the size dependences and cutoff diameters for nanowire growth. We also discuss methods to control and eliminate Au diffusion during the growth of Ge/Si core/shell heterostructures. Single crystal core/multi-shell Ge/p+Ge/Si nanowires were grown using such a process and their transport properties benchmarked. Using field-effect transistors as a test-bed for their transport properties, we observe up to 2X mobility enhancement in such heterostructured nanowires without Au diffusion and obtain record geometry-normalized on-currents for p-type FET devices of up to 430 µA/V. These studies provide an in-depth understanding for the control of the growth of Ge/Si nanowires and for exploiting their bandgap engineering possibilities for unique nanoscale device performance.
1 E. Sutter et al., 2010 (to be published).