Abstract
Thin Ge films directly grown on Si substrate using two-step low temperature growth technique are subjected to low load nano-indentation at room temperature. The nano-indentation is carried out using a Berkovich diamond tip (R ~ 20 nm). The residual impressions are studied using ex-situ Raman Micro-Spectroscopy, Atomic Force Microscopy combined system, and Transmission Electron Microscopy. The analysis of residual indentation impressions and displacement-load curves show evidence of deformation by phase transformation at room temperature under a critical pressure ranging from 4.9GPa–8.1GPa. Furthermore, the formation of additional Ge phases such as r8-Ge, hd-Ge, and amorphous Ge as a function of indentation depth have been realized. The inelastic deformation mechanism is found to depend critically on the indentation penetration depth. The non-uniform spatial distribution of the shear stress depends on the indentation depth and plays a crucial role in determining which phase is formed. Similarly, nano-indentation fracture response depends on indentation penetration depth. This opens the potential of tuning the contact response of Ge and other semiconductors thin films by varying indentation depth and indenter geometry. Furthermore, this observed effect can be reliably used to induce phase transformation in Ge-on-Si with technological interest as a narrow band gap material for mid-wavelength infrared detection.
Highlights
Epitaxial Growth of Ge-on Si platform has found a tremendous research interest in novel high-speed electronic and photonic devices[1,2,3,4]
In this work we report nanoindentation of Radio-Frequency Plasma Enhanced Chemical Vapor Deposition (RF-PECVD) Ge films directly grown on Si substrate
The projected area function A for the perfect Berkovich indenter is given by Ac = 24.5 hc[2], hc is the contact depth which is not the user defined of maximum penetration depth due to the elastic recovery of the film[13,40]
Summary
Epitaxial Growth of Ge-on Si platform has found a tremendous research interest in novel high-speed electronic and photonic devices[1,2,3,4]. Instrumented nanoindentation is a widely utilized technique and a well-controlled method for measuring the mechanical properties of bulk materials and thin films[13,14,15]. This technique allows for understanding the mechanical response of materials by applying a highly localized mechanical deformation. There have been only few previous studies on the transformation paths of Ge-on-Si system[33,34] This includes the induced structural changes in the films with varying indentation process conditions. The preferred deformation mechanism is highly affected by the preparation method These include the morphological, film constituents and possible impurity[21,34]. It is critical to understand the induced structural changes of Ge-on-Si under a point indenter
Sign-in/Register to view highlights & summary 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.
