Event Title

Fabrication and Characterization Techniques for Investigating and Exploiting the Elastic Properties of Two-Dimensional Silicon Nanostructures

Mentor 1

Dr. Gokul Gopalakrishnan

Mentor 2

Dr. Lee Farina

Location

Union Wisconsin Room

Start Date

24-4-2015 10:30 AM

End Date

24-4-2015 11:45 AM

Description

Fabrication of crystalline nanomembranes provides an opportunity to develop a process to understand the fundamental physical properties of nanomaterials and how they diverge from those of macroscopic structures. We focus our attention on the elastic constants of nanoscale single crystal silicon, which are expected to vary from bulk values due to the non-negligible surface-to-volume ratio in such systems. Nanoscale membranes are produced using a combination of top-down methods including lithographic techniques in conjunction with wet and dry chemical etching processes. Fabricating ideal two-dimensional systems with small uniform biaxial strains is a challenging engineering problem requiring careful optimization of each of the processing steps. One important aspect of the fabrication is improving interfacial bonding through a controlled atmosphere thermal annealing process which preserves the crystallinity of the membrane. We discuss the steps in the fabrication process and the characteristics of the nanomembranes thus produced. In order to acquire an understanding of the membrane’s mechanical properties, two complementary techniques involving atomic force microscopy are employed. The first technique generates force-deflection curves to study the effects of in-plane stresses and the elastic modulus of silicon nanomembranes. Deflection curves are generated by using the atomic force microscope’s cantilever to directly apply a force to deform the membrane. Data obtained from these deflection curves allows the creation of force curve maps to be compared with theoretical models. Secondly, we utilize the photodetector of the atomic force microscope to measure thermally activated resonances of the membranes. This is a completely independent way of measuring the Young’s Modulus and in-plane stresses in the membrane.

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Apr 24th, 10:30 AM Apr 24th, 11:45 AM

Fabrication and Characterization Techniques for Investigating and Exploiting the Elastic Properties of Two-Dimensional Silicon Nanostructures

Union Wisconsin Room

Fabrication of crystalline nanomembranes provides an opportunity to develop a process to understand the fundamental physical properties of nanomaterials and how they diverge from those of macroscopic structures. We focus our attention on the elastic constants of nanoscale single crystal silicon, which are expected to vary from bulk values due to the non-negligible surface-to-volume ratio in such systems. Nanoscale membranes are produced using a combination of top-down methods including lithographic techniques in conjunction with wet and dry chemical etching processes. Fabricating ideal two-dimensional systems with small uniform biaxial strains is a challenging engineering problem requiring careful optimization of each of the processing steps. One important aspect of the fabrication is improving interfacial bonding through a controlled atmosphere thermal annealing process which preserves the crystallinity of the membrane. We discuss the steps in the fabrication process and the characteristics of the nanomembranes thus produced. In order to acquire an understanding of the membrane’s mechanical properties, two complementary techniques involving atomic force microscopy are employed. The first technique generates force-deflection curves to study the effects of in-plane stresses and the elastic modulus of silicon nanomembranes. Deflection curves are generated by using the atomic force microscope’s cantilever to directly apply a force to deform the membrane. Data obtained from these deflection curves allows the creation of force curve maps to be compared with theoretical models. Secondly, we utilize the photodetector of the atomic force microscope to measure thermally activated resonances of the membranes. This is a completely independent way of measuring the Young’s Modulus and in-plane stresses in the membrane.