The path of phase transformation has something to do with sample preparation and loading condition. This study results in understanding both the phase transformation path and distributions in germanium, proving that the crystalline

orientation also influences the path of phase transformation in nanoindentation of germanium. Figure 11 presents the process of phase transition in nanoindentation on the (010) plane. The bct5-Ge initially appearing under the indenter transforms into Ge-II with continuing loading, which indicates that the bct5-Ge could be an intermediate in the formation of Ge-II phase similar to silicon, as mentioned in previous researches [16, 25]. However, the bct5-Ge in the surrounding area does not transform into Ge-II find more with continuing loading. click here In addition, the bct5-Ge forming

in nanoindentation on the (101) and (111) planes does not transform into Ge-II structure either. These phenomena suggest that pressure with specific directions could induce phase transition from bct5-Ge to Ge-II structure. In other words, axial force with specific directions could trigger phase transformation from diamond cubic germanium to Ge-II phase besides the hydrostatic stress. Figure 11 The process of phase transformation in nanoindentation on the (010) germanium surface. The indentation depth is (a) approximately 1.2 nm, (b) approximately 2 nm, and (c) approximately 4.5 nm. The bct5-Ge structure always forms around the center of the transformed region and almost still exists after unloading. At the same time, the majority of the mixed structure with fourfold and fivefold coordinated atoms forming under fantofarone pressure stress recovers the diamond structure after load relief. The calculated stress in this region is about 6 GPa, which is much lower than the threshold stress initiating the phase transformation. Hence, it is suggested that the mixed structure mentioned previously is the distorted diamond cubic structure. The elastic deformation of this region arises on loading, and it returns back to the original diamond structure during unloading.

The change in the coordination number of the atoms may comes from the inappropriate cutoff radius for calculation of the nearest neighbors. The borders of the transformed regions are mostly parallel to germanium’s slip direction of < 110 >, which influences the shape of deformed layers after nanoindentation. The maximum extending depth of the deformed layers also differs based on the crystal orientation of the germanium contact surface. The distribution of deformed layers on the (111) germanium surface is more compact and has the thinnest depth from the contact surface into the substrate, while those on the (010) and (101) surfaces have great difference in depth on various regions and extend deeper into the substrate. The recovery of the central location in nanoindentation on unloading is recorded in Table 1.