skip to main content
OSTI.GOV title logo U.S. Department of Energy
Office of Scientific and Technical Information

Title: Nanomechanics of hard films on compliant substrates.

Abstract

Development of flexible thin film systems for biomedical, homeland security and environmental sensing applications has increased dramatically in recent years [1,2,3,4]. These systems typically combine traditional semiconductor technology with new flexible substrates, allowing for both the high electron mobility of semiconductors and the flexibility of polymers. The devices have the ability to be easily integrated into components and show promise for advanced design concepts, ranging from innovative microelectronics to MEMS and NEMS devices. These devices often contain layers of thin polymer, ceramic and metallic films where differing properties can lead to large residual stresses [5]. As long as the films remain substrate-bonded, they may deform far beyond their freestanding counterpart. Once debonded, substrate constraint disappears leading to film failure where compressive stresses can lead to wrinkling, delamination, and buckling [6,7,8] while tensile stresses can lead to film fracture and decohesion [9,10,11]. In all cases, performance depends on film adhesion. Experimentally it is difficult to measure adhesion. It is often studied using tape [12], pull off [13,14,15], and peel tests [16,17]. More recent techniques for measuring adhesion include scratch testing [18,19,20,21], four point bending [22,23,24], indentation [25,26,27], spontaneous blisters [28,29] and stressed overlayers [7,26,30,31,32,33]. Nevertheless, sample design and test techniques mustmore » be tailored for each system. There is a large body of elastic thin film fracture and elastic contact mechanics solutions for elastic films on rigid substrates in the published literature [5,7,34,35,36]. More recent work has extended these solutions to films on compliant substrates and show that increasing compliance markedly changes fracture energies compared with rigid elastic solution results [37,38]. However, the introduction of inelastic substrate response significantly complicates the problem [10,39,40]. As a result, our understanding of the critical relationship between adhesion, properties, and fracture for hard films on compliant substrates is limited. To address this issue, we integrated nanomechanical testing and mechanics-based modeling in a program to define the critical relationship between deformation and fracture of nanoscale films on compliant substrates. The approach involved designing model film systems and employing nano-scale experimental characterization techniques to isolate effects of compliance, viscoelasticity, and plasticity on deformation and fracture of thin hard films on substrates that spanned more than two orders of compliance magnitude exhibit different interface structures, have different adhesion strengths, and function differently under stress. The results of this work are described in six chapters. Chapter 1 provides the motivation for this work. Chapter 2 presents experimental results covering film system design, sample preparation, indentation response, and fracture including discussion on the effects of substrate compliance on fracture energies and buckle formation from existing models. Chapter 3 describes the use of analytical and finite element simulations to define the role of substrate compliance and film geometry on the indentation response of thin hard films on compliant substrates. Chapter 4 describes the development and application of cohesive zone model based finite element simulations to determine how substrate compliance affects debond growth. Chapter 5 describes the use of molecular dynamics simulations to define the effects of substrate compliance on interfacial fracture of thin hard tungsten films on silicon substrates. Chapter 6 describes the Workshops sponsored through this program to advance understanding of material and system behavior.« less

Authors:
 [1];  [2]; ; ;  [3];  [1];  [2];  [4];  [1];  [5];  [6]
  1. Sandia National Laboratories, Albuquerque, NM
  2. Washington State University, Pullman, WA
  3. University of Minnesota, Minneapolis, MN
  4. Johns Hopkins University, Baltimore, MD
  5. Clemson University, Clemson, SC
  6. Erich Schmid Institute, Leoben, Austria
Publication Date:
Research Org.:
Sandia National Laboratories (SNL), Albuquerque, NM, and Livermore, CA (United States)
Sponsoring Org.:
USDOE
OSTI Identifier:
993624
Report Number(s):
SAND2009-6196
TRN: US201024%%16
DOE Contract Number:  
AC04-94AL85000
Resource Type:
Technical Report
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; 77 NANOSCIENCE AND NANOTECHNOLOGY; THIN FILMS; NANOSTRUCTURES; SUBSTRATES; FLEXIBILITY; MECHANICAL PROPERTIES; ADHESION; FRACTURE PROPERTIES; PLASTICITY; SAMPLE PREPARATION; SILICON; TUNGSTEN; FINITE ELEMENT METHOD; MOLECULAR DYNAMICS METHOD

Citation Formats

Reedy, Earl David, Jr., Emerson, John Allen, Bahr, David F, Moody, Neville Reid, Zhou, Xiao Wang, Hales, Lucas, Adams, David Price, Yeager, John, Nyugen, Thao D, Corona, Edmundo, Kennedy, Marian S, and Cordill, Megan J. Nanomechanics of hard films on compliant substrates.. United States: N. p., 2009. Web. doi:10.2172/993624.
Reedy, Earl David, Jr., Emerson, John Allen, Bahr, David F, Moody, Neville Reid, Zhou, Xiao Wang, Hales, Lucas, Adams, David Price, Yeager, John, Nyugen, Thao D, Corona, Edmundo, Kennedy, Marian S, & Cordill, Megan J. Nanomechanics of hard films on compliant substrates.. United States. https://doi.org/10.2172/993624
Reedy, Earl David, Jr., Emerson, John Allen, Bahr, David F, Moody, Neville Reid, Zhou, Xiao Wang, Hales, Lucas, Adams, David Price, Yeager, John, Nyugen, Thao D, Corona, Edmundo, Kennedy, Marian S, and Cordill, Megan J. 2009. "Nanomechanics of hard films on compliant substrates.". United States. https://doi.org/10.2172/993624. https://www.osti.gov/servlets/purl/993624.
@article{osti_993624,
title = {Nanomechanics of hard films on compliant substrates.},
author = {Reedy, Earl David, Jr. and Emerson, John Allen and Bahr, David F and Moody, Neville Reid and Zhou, Xiao Wang and Hales, Lucas and Adams, David Price and Yeager, John and Nyugen, Thao D and Corona, Edmundo and Kennedy, Marian S and Cordill, Megan J},
abstractNote = {Development of flexible thin film systems for biomedical, homeland security and environmental sensing applications has increased dramatically in recent years [1,2,3,4]. These systems typically combine traditional semiconductor technology with new flexible substrates, allowing for both the high electron mobility of semiconductors and the flexibility of polymers. The devices have the ability to be easily integrated into components and show promise for advanced design concepts, ranging from innovative microelectronics to MEMS and NEMS devices. These devices often contain layers of thin polymer, ceramic and metallic films where differing properties can lead to large residual stresses [5]. As long as the films remain substrate-bonded, they may deform far beyond their freestanding counterpart. Once debonded, substrate constraint disappears leading to film failure where compressive stresses can lead to wrinkling, delamination, and buckling [6,7,8] while tensile stresses can lead to film fracture and decohesion [9,10,11]. In all cases, performance depends on film adhesion. Experimentally it is difficult to measure adhesion. It is often studied using tape [12], pull off [13,14,15], and peel tests [16,17]. More recent techniques for measuring adhesion include scratch testing [18,19,20,21], four point bending [22,23,24], indentation [25,26,27], spontaneous blisters [28,29] and stressed overlayers [7,26,30,31,32,33]. Nevertheless, sample design and test techniques must be tailored for each system. There is a large body of elastic thin film fracture and elastic contact mechanics solutions for elastic films on rigid substrates in the published literature [5,7,34,35,36]. More recent work has extended these solutions to films on compliant substrates and show that increasing compliance markedly changes fracture energies compared with rigid elastic solution results [37,38]. However, the introduction of inelastic substrate response significantly complicates the problem [10,39,40]. As a result, our understanding of the critical relationship between adhesion, properties, and fracture for hard films on compliant substrates is limited. To address this issue, we integrated nanomechanical testing and mechanics-based modeling in a program to define the critical relationship between deformation and fracture of nanoscale films on compliant substrates. The approach involved designing model film systems and employing nano-scale experimental characterization techniques to isolate effects of compliance, viscoelasticity, and plasticity on deformation and fracture of thin hard films on substrates that spanned more than two orders of compliance magnitude exhibit different interface structures, have different adhesion strengths, and function differently under stress. The results of this work are described in six chapters. Chapter 1 provides the motivation for this work. Chapter 2 presents experimental results covering film system design, sample preparation, indentation response, and fracture including discussion on the effects of substrate compliance on fracture energies and buckle formation from existing models. Chapter 3 describes the use of analytical and finite element simulations to define the role of substrate compliance and film geometry on the indentation response of thin hard films on compliant substrates. Chapter 4 describes the development and application of cohesive zone model based finite element simulations to determine how substrate compliance affects debond growth. Chapter 5 describes the use of molecular dynamics simulations to define the effects of substrate compliance on interfacial fracture of thin hard tungsten films on silicon substrates. Chapter 6 describes the Workshops sponsored through this program to advance understanding of material and system behavior.},
doi = {10.2172/993624},
url = {https://www.osti.gov/biblio/993624}, journal = {},
number = ,
volume = ,
place = {United States},
year = {2009},
month = {9}
}