Germanium Nanowire (GeNW) has drawn the interest for electronic device material since it has high intrinsic hole and electron mobilities compared to silicon, low growth temperature through Vapor-Liquid-Solid growth, and its compatibility with the current silicon VLSI technology. Heteroepitaxial growth of GeNW on the Si substrate is the key for a direct bottom-up self-assembly of three-dimensional device applications. In this study, we examined the effect of the annealing condition prior to the introduction of the precursor. Annealing below the Au-Si eutectic temperature (T<SUB>e</SUB>) leads to the formation of a single, well oriented interface that templates heteroepitaxial nucleation, whereas annealing above Au-Si T<SUB>e</SUB> leads the formation of multiple nucleation sites and randomly oriented growth. The Si substrate was treated under buffered hydrofluoric. A mixed solution of 40nm Au colloidal nanoparticles and 10% HF/H<SUB>2</SUB>O was dispersed on the substrate. The substrate was then loaded into hot-wall tube furnace, and annealed between 280°C to 400°C for 5 min in 100 Torr with H<SUB>2</SUB> flow. After annealing, GeNWs were grown using GeH<SUB>4</SUB> (diluted in H<SUB>2</SUB>) at 280°C. The results are observed by using scanning electron microscopy (SEM). The substrate underwent growth step without annealing step (GeH<SUB>4</SUB> is flown right after reaching the growth temperature) shows poor growth. Therefore, certain stabilization time for annealing is required for reproducible epitaxial growth of GeNW. The GeNW growth results are compared between different annealing temperatures. The GeNWs grown on Si (111) after annealing temperature of 280°C and 320°C have uniform diameters of ~50nm without significant tapering along an average length of ~2.2μm. Most of the NW is grown perpendicular to the (111) substrate and the others are also along with the other <111> direction. Transmission electron microscopy (TEM) of the GeNWs confirms the crystalline nanowires are grown along  direction. In comparison, when the substrate is annealed at 400°C for 5 min prior to GeH<SUB>4</SUB> flow, there is no successfully grown GeNW. The results suggests that the substrate annealing below the eutectic temperature (T<SUB>e</SUB>) of the substrate (Si) and catalyst (Au), 363°C, is critical for the heteroepitaxial growth of GeNWs on Si(111). When Au is annealed at below T<SUB>e</SUB> of Au-Si, a well-defined interface between Au and Si(111) is formed. However, when the substrate is annealed at above Au-Si T<SUB>e</SUB>, an Au-Si eutectic liquid alloy develops facets below the substrate. When the temperature is lowered into the growth temperature 280°C, some amount of Si from Au-Si alloy is rejected. Subsequent provision of Ge via GeH<SUB>4</SUB> to the solidified Au-Si alloy will result in non-epitaxial growth. This study shows that the annealing below T<SUB>e</SUB> of the substrate and catalyst is necessary for the heteroepitaxial GeNW growth, and it can be applied for a direct assembly of applications.