Nanoindentation probing of high-aspect ratio pillar structures on optical multilayer dielectric diffraction gratings

2012 ◽  
Vol 1474 ◽  
Author(s):  
K. Mehrotra ◽  
H.P. Howard ◽  
S.D. Jacobs ◽  
J.C. Lambropoulos
Keyword(s):  
Aspect Ratio ◽  
Yield Stress ◽  
High Aspect Ratio ◽  
Mechanical Response ◽  
Diffraction Gratings ◽  
Material Hardness ◽  
Similar Dependence ◽  
Strain Model ◽  
Indentation Response ◽  
Multilayer Dielectric

ABSTRACTWe measure the mechanical response of optical multilayer dielectric (MLD) diffraction gratings, geometries which are constrained in only one transverse direction but free in the other, using nanoindentation. The results are explained using a stress-strain model, which reveals a uniaxial yield stress of 4.1- 4.6 GPa and predicts a similar dependence of yield stress on loads for both fully-elastic and fully-plastic solutions. Following R. Hill’s model of an expanding cavity under internal pressure, we show that the indentation response of the high-aspect ratio “pillar” geometry can be expressed in terms of uniaxial yield stress rather than material hardness.

scholarly journals Nanoindentation of high-aspect ratio pillar structures on optical multilayer dielectric diffraction gratings

AIP Advances ◽  
2011 ◽  
Vol 1 (4) ◽  
pp. 042179 ◽  
Author(s):  
K. Mehrotra ◽  
H. P. Howard ◽  
S. D. Jacobs ◽  
J. C. Lambropoulos
Keyword(s):  
Aspect Ratio ◽  
High Aspect Ratio ◽  
Diffraction Gratings ◽  
Multilayer Dielectric

Fully Lagrangian Modeling of Dynamics of MEMS With Thin Beams—Part I: Undamped Vibrations

2009 ◽  
Vol 76 (5) ◽  
Author(s):  
Ranajay Ghosh ◽  
Subrata Mukherjee
Keyword(s):  
Aspect Ratio ◽  
High Aspect Ratio ◽  
Mechanical Response ◽  
Boundary Integral ◽  
Lagrangian Description ◽  
Charge Densities ◽  
Lagrangian Modeling ◽  
Modeling Of Dynamics ◽  
Thin Beams ◽  
Element Method

Micro-electro-mechanical systems (MEMSs) often use beam or plate shaped conductors that can be very thin—with h/L≈O(10–2–10–3) (in terms of the thickness h and length L of the beam or side of a square plate). Such MEMS devices find applications in microsensors, micro-actuators, microjets, microspeakers, and other systems where the conducting beams or plates oscillate at very high frequencies. Conventional boundary element method analysis of the electric field in a region exterior to such thin conductors can become difficult to carry out accurately and efficiently—especially since MEMS analysis requires computation of charge densities (and then surface traction) separately on the top and bottom surfaces of such beams. A new boundary integral equation has been proposed to handle the computation of charge densities for such high aspect ratio geometries. In the current work, this has been coupled with the finite element method to obtain the response behavior of devices made of such high aspect ratio structural members. This coupling of electrical and mechanical problems is carried out using a Newton scheme based on a Lagrangian description of the electrical and mechanical domains. The numerical results are presented in this paper for the dynamic behavior of the coupled MEMS without damping. The effect of gap between a beam and the ground, on mechanical response of a beam subjected to increasing electric potential, is studied carefully. Damping is considered in the companion paper (Ghosh and Mukherjee, 2009, “Fully Lagrangian Modeling of Dynamics of MEMS With Thin Beams—Part II: Damped Vibrations,” ASME J. Appl. Mech. 76, p. 051008).

Fabrication of high-aspect-ratio resonance domain diffraction gratings in fused silica

2012 ◽  
Vol 51 (11) ◽  
pp. 118002 ◽  
Author(s):  
Omri Barlev ◽  
Michael A. Golub ◽  
Asher A. Friesem ◽  
Diana Mahalu ◽  
Menachem Nathan
Keyword(s):  
Aspect Ratio ◽  
High Aspect Ratio ◽  
Diffraction Gratings ◽  
Fused Silica ◽  
Resonance Domain

Mechanical characterization of “blister” defects on optical oxide multilayers using nanoindentation

2012 ◽  
Vol 1454 ◽  
pp. 215-220 ◽  
Author(s):  
K. Mehrotra ◽  
H.P. Howard ◽  
S.D. Jacobs ◽  
J.C. Lambropoulos
Keyword(s):  
Mechanical Response ◽  
Mechanical Characterization ◽  
Site Specific ◽  
Acid Cleaning ◽  
Cleaning Procedures ◽  
Indentation Response ◽  
Multilayer Dielectric

ABSTRACTWe characterize “blisters”, defects observed in multilayer dielectric (MLD) coatings after exposure to acid cleaning procedures. Nanoindentation is used to make site-specific indentations across blisters to measure the mechanical response, especially their compliance under different conditions of loading. Two regions of statistically different mechanical response are identified within a blister defect and compared to the undisturbed regions of the MLD coating. The indentation response of blisters can vary across samples, and we suggest reasons for this variation.

scholarly journals Numerical Optimization of Refractive Index Sensors Based on Diffraction Gratings with High Aspect Ratio in Terahertz Range

Sensors ◽  
2021 ◽  
Vol 22 (1) ◽  
pp. 172
Author(s):  
Oleg Kameshkov ◽  
Vasily Gerasimov ◽  
Boris Knyazev
Keyword(s):  
Refractive Index ◽  
Aspect Ratio ◽  
High Aspect Ratio ◽  
Diffraction Gratings ◽  
High Sensitivity ◽  
Label Free ◽  
Subwavelength Gratings ◽  
Refractive Index Sensors ◽  
Traditional Approaches ◽  
2D And 3D

Terahertz surface plasmon resonance (SPR) sensors have been regarded as a promising technology in biomedicine due to their real-time, label-free, and ultrasensitive monitoring features. Different authors have suggested a lot of SPR sensors, including those based on 2D and 3D metamaterials, subwavelength gratings, graphene, and graphene nanotube, as well as others. However, one of the traditional approaches to realize high sensitivity SPR sensors based on metal diffraction gratings has been studied poorly in the terahertz frequency range. In this article, a linear metal rectangular diffraction grating with high aspect ratio is studied. The influence of the grating structure parameters on the sensor sensitivity is simulated. Effects arising from different ratios of depth and width were discovered and explained. The results show that the sensitivity can be increased to 2.26 THz/RIU when the refractive index range of the gas to measure is between 1 and 1.002 with the resolution 5×10−5 RIU.

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