In situ control over the growth morphology of nanocones has important implications to their application in photovoltaic and thermoelectric devices. In this study, Ge nanocones were grown by an Au-catalyzed process in a chemical vapor deposition (CVD) chamber using germane (GeH4) as the source gas. The growth temperature was varied for different segments of the growth, and a corresponding variation of taper (angle of cone sidewalls relative to the axial direction) in the segments was observed. The structures obtained in these experiments reveal their temperature-dependent modes of growth. When the growth was conducted at an initial temperature of 350 degrees C then increased to 400 degrees C, faceted pillars consisting of a base segment of largely uniform diameter and a conical tapered tip were formed. When the growth was conducted at 395 and 375 degrees C, then at 350 degrees C, the nanocones featured a base with a wider taper and tips with a smaller taper. The dependence on temperature of the growth morphology is attributed to the relative influence of competing growth mechanisms at different temperature regimes: catalyzed unidirectional growth at lower temperatures approaching the Au-Ge eutectic point, and increasingly isotropic and facet-bounded epitaxial growth at higher temperatures up to 400 degrees C. The multi-step growth method also provides a reliable method of determining the rate and mode of catalyzed growth. (C) 2010 Elsevier B.V. All rights reserved.