Abstract
The vibrational dispersion relations of porous germanium (pGe) and germanium nanowires (GeNWs) were calculated using the ab initio density functional perturbation theory with a generalized gradient approximation with norm-conserving pseudopotentials. Both pores and nanowires were modeled using the supercell technique. All of the surface dangling bonds were saturated with hydrogen atoms. To address the difference in the confinement between the pores and the nanowires, we calculated the vibrational density of states of the two materials. The results indicate that there is a slight shift in the highest optical mode of the Ge-Ge vibration interval in all of the nanostructures due to the phonon confinement effects. The GeNWs exhibit a reduced phonon confinement compared with the porous Ge due to the mixed Ge-dihydride vibrational modes around the maximum bulk Ge optical mode of approximately 300 cm−1; however, the general effects of such confinements could still be noticed, such as the shift to lower frequencies of the highest optical mode belonging to the Ge vibrations.
Highlights
Germanium (Ge) nanomaterials, such as porous Ge and Ge nanowires (GeNWs), have become attractive due to the higher electron mobility of Ge with respect to silicon
We studied the phonon density of states of Ge nanostructures with the first principles density functional perturbation theory technique using the generalized gradient approximation and norm-conserving pseudopotentials
It can be observed that, both approaches yield results that are in reasonably good agreement with the experimental data especially near the highest optical mode, the density functional perturbation theory (DFPT) results have a better fit with the experimental results in the remaining portion of the spectrum
Summary
Germanium (Ge) nanomaterials, such as porous Ge (pGe) and Ge nanowires (GeNWs), have become attractive due to the higher electron mobility of Ge with respect to silicon. The porous case has been treated as a collection of interconnected nanowires, and the effects of such interconnection on the electronic and optical properties of nanopores and nanowires has been examined in other theoretical works [13,14]. Another important quantum mechanical feature of nanopores and nanowires is the phonon confinement effect because many material properties, such as thermal transport, can be understood in terms of phonons. We performed a comparison of the phonon confinement effects between porous structures and nanowires by comparing their respective density of states with similar confinement distances
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
