| About this Abstract |
| Meeting |
2011 Electronic Materials Conference
|
| Symposium
|
2011 Electronic Materials Conference
|
| Presentation Title |
KK1, Size Effects in Ni Catalyzed Germanium Nanowire Growth |
| Author(s) |
Shruti V. Thombare, Ann F. Marshall, Paul C. McIntyre |
| On-Site Speaker (Planned) |
Shruti V. Thombare |
| Abstract Scope |
The great majority of literature studies of Ge nanowire growth have used Au as a catalyst. In most cases, growth is said to have occurred by the VLS mechanism. Gold has been a popular choice as a catalyst in part because of its ability to form a eutectic with Ge, allowing nanowire growth at a temperature below 400 C. However, Au induces trap levels deep in the Si and Ge bandgaps. In order to make deposited Ge nanowires compatible with silicon-based electronics and useful for photovoltaic applications, an electronically benign metal catalyst may be required. We report an investigation of low temperature Ge nanowire growth using Ni, which is electronically more benign than Au. Ni nanoparticles in colloidal solution were drop-cast on Ge (111) substrates. Ge nanowires were grown at temperatures as low as 375°C in a cold-wall CVD reactor with hydrogen diluted Germane as reactive precursor. Nanowire growth is expected to occur by the vapor-solid-solid (VSS) mechanism with a germanide of Ni as the catalyst phase, because the growth temperature is depressed by greater than 300° C relative to the lowest eutectic temperature in the Ni-Ge binary system. We observed a great difference in the morphology of the nanowires as a function of their diameter. Their length and preferred crystallographic orientation were strongly dependent on nanowire diameter. Nanowires with diameter greater than 25-35 nm are <111>-oriented and have a high density of grown-in defects such as twins and stacking faults and exhibit frequent kinking. Transmission electron microscopy showed that nanowires with diameter smaller than 25-35 nm, which grow preferentially in the <110> direction, appear to have no kinks despite having a substantial density of crystal defects. The observed size-dependence of Ge wire morphology will be discussed in terms of wire surface energies and the structure of the catalyst/nanowire growth facet interface. |
| Proceedings Inclusion? |
Undecided |