A Brittle to Ductile Transition (BDT) in Adhered Thin Films

1999 ◽  
Vol 594 ◽  
Author(s):  
W. W. Gerberich ◽  
A. A. Volinsky ◽  
N. I. Tymiak ◽  
N. R. Moody
Keyword(s):  
Thin Films ◽  
Energy Dissipation ◽  
Yield Strength ◽  
Plastic Zone ◽  
Film Thickness ◽  
Fracture Energy ◽  
Test Temperature ◽  
Plastic Energy ◽  
Order Of Magnitude ◽  
Film Substrate

AbstractIt has been long recognized that the BDT in bulk materials may be associated with enhanced plastic energy dissipation. This can be achieved by either changing the state of stress (plane strain to plane stress) or by raising the test temperature (lowering the yield stress). The situation is somewhat different in thin films where the BDT can be achieved by increasing film thickness or perhaps, even in a limited temperature range, by raising the test temperature. To study the latter we use a superlayer technique with a 1 μm tungsten film on top of thin copper films bonded to SiO2/Si wafers. This involves indenting into the superlayer which stores and then releases large amounts of elastic energy into the thin film/substrate interface. Here, preliminary data on 500 nm thick Cu demonstrates more than an order of magnitude increase in fracture energy from about 10 to 200 J/m2 as the test temperature is raised from 20°C to 130°C. As the amount of plastic energy absorption would appear to be limited by film thickness, this relatively large value was unanticipated. This interfacial fracture energy translates to a stress intensity of 5 MPa-m1/2. In context of the highest possible nanocrystalline Cu yield strength, this still represents a plastic zone of nearly 30 μm. This illustrates the quandary associated with explaining such high apparent toughness values as one generally expects plasticity to be truncated by film thickness. Is this associated with:–some artifact of assessing local stresses during nanoindentation at elevated temperature:–extending the plastic zone in the direction of crack growth much further than the film thickness;–a shielding mechanism from an organized dislocation array in a ductile film sandwiched between a brittle substrate and a higher yield strength superlayer;–some plastic energy dissipation in the superlayer;–or by enhanced mode II at higher temperatures?A few of these will be addressed in some detail with a goal of narrowing the field of the most promising candidates.

scholarly journals Enhanced Ionic Conduction at the Film/Substrate Interface in LiI Thin Films Grown on Sapphire(0001)

1993 ◽  
Vol 318 ◽  
Author(s):  
D. Lubben ◽  
F. A. Modine
Keyword(s):  
Thin Films ◽  
Film Thickness ◽  
Ionic Conduction ◽  
High Vacuum ◽  
Dislocation Motion ◽  
Ultra High Vacuum ◽  
Vacuum System ◽  
Substrate Interface ◽  
Interdigital Electrodes ◽  
Film Substrate

ABSTRACTThe ionic conductivity of LiI thin films grown on sapphire(0001) substrates has been studied in situ during deposition as a function of film thickness and deposition conditions. LiI films were produced at room temperature by sublimation in an ultra-high-vacuum system. The conductivity of the Lil parallel to the film/substrate interface was determined from frequency-dependent impedance measurements as a function of film thickness using Au interdigital electrodes deposited on the sapphire surface. The measurements show a conduction of ∼5 times the bulk value at the interface which gradually decreases as the film thickness is increased beyond 100 nm. This interfacial enhancement is not stable but anneals out with a characteristic log of time dependence. Fully annealed films have an activation energy for conduction (σT) of ∼0.47 ± .03 eV, consistent with bulk measurements. The observed annealing behavior can be fit with a model based on dislocation motion which implies that the increase in conduction near the interface is not due to the formation of a space-charge layer as previously reported but to defects generated during the growth process. This explanation is consistent with the behavior exhibited by CaF2 films grown under similar conditions.

Characterization of spray-pyrolized superconducting YBaCuO thin films on single-crystal MgO by transmission electron microscopy

1990 ◽  
Vol 5 (8) ◽  
pp. 1605-1611 ◽  
Author(s):  
S. J. Golden ◽  
H. Isotalo ◽  
M. Lanham ◽  
J. Mayer ◽  
F. F. Lange ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Thin Films ◽  
Transmission Electron Microscopy ◽  
Film Thickness ◽  
Single Crystal ◽  
Processing Parameters ◽  
Transmission Electron ◽  
Film Substrate ◽  
Mgo Substrate

Superconducting YBaCuO thin films have been fabricated on single-crystal MgO by the spray-pyrolysis of nitrate precursors. The effects on the superconductive behavior of processing parameters such as time and temperature of heat treatment and film thickness were investigated. The superconductive behavior was found to be strongly dependent on film thickness. Films of thickness 1 μm were found to have a Tc of 67 K while thinner films showed appreciably degraded properties. Transmission electron microscopy studies have shown that the heat treatments necessary for the formation of the superconductive phase (for example, 950 °C for 30 min) also cause a substantial degree of film-substrate interdiffusion. Diffusion distances for Cu in the MgO substrate and Mg in the film were found to be sufficient to explain the degradation of the superconductive behavior in films of thickness 0.5 μm and 0.2 μm. From the concentration profiles obtained by EDS analysis diffusion coefficients at 950 °C for Mg into the YBaCuO thin film and for Cu into the MgO substrate were evaluated as 3 × 10−19 m2/s and 1 × 10−17 m2/s, respectively.

Effects of substrate on determination of hardness of thin films by nanoscratch and nanoindentation techniques

2004 ◽  
Vol 19 (6) ◽  
pp. 1791-1802 ◽  
Author(s):  
Noureddine Tayebi ◽  
Andreas A. Polycarpou ◽  
Thomas F. Conry
Keyword(s):  
Thin Films ◽  
Film Thickness ◽  
Elastic Recovery ◽  
Empirical Relationship ◽  
Residual Deformation ◽  
Substrate Effect ◽  
Nanoindentation Technique ◽  
Film Substrate ◽  
Composite Hardness

A comparative study on the effects of the substrate on the determination of hardness of thin films by the use of the nanoscratch and nanoindentation techniques was conducted. Gold films deposited on fused quartz substrates and silicon dioxide films deposited on aluminum substrates with variant film thicknesses were investigated. These two systems correspond to a soft film on a hard substrate and a hard film on a soft substrate, respectively. The effect of substrate interaction on the measurement of hardness using the nanoscratch technique was found to be less pronounced compared to that of the nanoindentation technique due to: (i) the lower normal loads applied to achieve the penetration depths that occur at higher loads when using the nanoindentation method; (ii) the direct imaging of the residual deformation profile that is used in the nanoscratch technique, which allows for the effects of pileup or sink-in to be taken into account, whereas in the nanoindentation technique the contact area is estimated from the load-displacement data, which does not include such effects; and (iii) the account of elastic recovery of the plastically deformed surfaces from scratch tests. The film thickness did not appear to have any effect on the hardness of Au and SiO2 films obtained from nanoscratch data. This observation allowed, for the case of SiO2 films, the determination of the “free substrate effect region” and the derivation of an empirical relationship that relates the composite hardness of the film/substrate system to the contact-depth-to-film-thickness ratio, even when the indenter penetrates into the substrate. Such findings can allow for the determination of the intrinsic hardness of ultrathin hard films (∼1–5 nm thick), where the substrate effect is unavoidable.

The cracking and decohesion of thin films

1988 ◽  
Vol 3 (5) ◽  
pp. 1043-1049 ◽  
Author(s):  
A. G. Evans ◽  
M. D. Drory ◽  
M. S. Hu
Keyword(s):  
Thin Films ◽  
Residual Stress ◽  
Yield Strength ◽  
Film Thickness ◽  
Elastic Properties ◽  
Fracture Resistance ◽  
Critical Values ◽  
Substrate Thickness ◽  
The Status ◽  
Ductile Substrates

The cracking and decohesion of thin films can be characterized by critical values of a nondimensional parameter governed by the residual stress, the film thickness, and a fracture resistance. This article reviews the status of understanding concerning the magnitude of this number for various types of adherent film on either brittle or ductile substrates. Important effects of elastic properties, substrate thickness, and yield strength are described.

Continuous microscratch measurements of the practical and true works of adhesion for metal/ceramic systems

1996 ◽  
Vol 11 (12) ◽  
pp. 3133-3145 ◽  
Author(s):  
S. Venkataraman ◽  
D. L. Kohlstedt ◽  
W. W. Gerberich
Keyword(s):  
Thin Film ◽  
Energy Dissipation ◽  
Film Thickness ◽  
Annealing Temperature ◽  
Plastic Work ◽  
Practical Work ◽  
Work Of Adhesion ◽  
Plastic Energy ◽  
Annealing Conditions ◽  
Metal Ceramic

Using a continuous microscratch technique, the adhesion strengths of Pt, Cr, Ti, and Ta2N metallizations to NiO and Al2O3 substrates have been characterized. The practical work of adhesion was determined as a function of both thickness and annealing conditions. For all except the Ta2N films, the practical work of adhesion increases nonlinearly from a few tenths of a J/m2 to several J/m2 as the thickness of the thin film is increased, indicating that a greater amount of plastic work is expended in delaminating thicker films. Further, the practical work of adhesion also increases with increasing annealing temperature, indicating stronger bonding at the interface. In the limit that the film thickness tends to zero, the plastic energy dissipation in the film tends to zero. As a result, the extrapolation to zero thickness yields the true work of adhesion for that system.

Growth of TiO2 thin films on Si(001) and SiO2 by reactive high power impulse magnetron sputtering

2011 ◽  
Vol 1352 ◽  
Author(s):  
F. Magnus ◽  
B. Agnarsson ◽  
A. S. Ingason ◽  
K. Leosson ◽  
S. Olafsson ◽  
...  
Keyword(s):  
Thin Films ◽  
Surface Roughness ◽  
Magnetron Sputtering ◽  
Film Thickness ◽  
High Power ◽  
Amorphous Matrix ◽  
Dc Magnetron Sputtering ◽  
Tio2 Thin Films ◽  
Temperature Range ◽  
Order Of Magnitude

ABSTRACTThin TiO2 films were grown on Si(001) and SiO2 substrates by reactive dc magnetron sputtering (dcMS) and high power impulse magnetron sputtering (HiPIMS) at temperatures ranging from 300 to 700 °C. Both dcMS and HiPIMS produce polycrystalline rutile TiO2 grains, embedded in an amorphous matrix, despite no postannealing taking place. HiPIMS results in significantly larger grains, approaching 50% of the film thickness at 700 °C. In addition, the surface roughness of HiPIMS-grown films is below 1 nm rms in the temperature range 300–500 °C which is an order of magnitude lower than that of dcMS-grown films. The results show that smooth, rutile TiO2 films can be obtained by HiPIMS at relatively low growth temperatures, without postannealing.

Residual stresses in polycrystalline Cu/Cr multilayered thin films

2000 ◽  
Vol 15 (3) ◽  
pp. 756-763 ◽  
Author(s):  
A. Misra ◽  
H. Kung ◽  
T. E. Mitchell ◽  
M. Nastasi
Keyword(s):  
Thin Films ◽  
Residual Stress ◽  
Yield Strength ◽  
Residual Stresses ◽  
Layer Thickness ◽  
Growth Stresses ◽  
Cu Films ◽  
Bilayer Films ◽  
Order Of Magnitude ◽  
Substrate Curvature

Residual stresses in sputter-deposited Cu/Cr multilayers and Cu and Cr single-layered polycrystalline thin films were evaluated by the substrate curvature method. The stresses in the multilayers were found to be tensile and to increase in magnitude with increasing layer thickness (h) to a peak value of ∼1 GPa for h = 50 nm. For h > 50 nm, the residual stress decreased with increasing h but remained tensile. The same trends were observed in single-layered Cu and Cr thin films, except that the maximum stress in Cu films is 1 order of magnitude lower than that in Cr. Transmission electron microscopy was used to study the microstructural evolution as a function of layer thickness. The evolution of tensile growth stresses in Cr films is explained by island coalescence and subsequent growth with increasing thickness. Estimates of the Cr film yield strength indicated that, for h ≥ 50 nm, the residual stress may be limited by the yield strength. Substrate curvature measurements on bilayer films of different thicknesses were used to demonstrate that a non-negligible contribution to the total stress in the multilayers arises from the interface stress.

The Cracking and Decohesion of Thin Films

1987 ◽  
Vol 108 ◽  
Author(s):  
A. G. Evans ◽  
M. D. Drory ◽  
M. S. Hu
Keyword(s):  
Thin Films ◽  
Residual Stress ◽  
Yield Strength ◽  
Film Thickness ◽  
Elastic Properties ◽  
Fracture Resistance ◽  
Substrate Thickness ◽  
Dimensional Parameter ◽  
The Status ◽  
Ductile Substrates

ABSTRACTThe cracking and decohesion of thin films can be characterized by critical values of a non-dimensional parameter governed by the residual stress, the film thickness and a fracture resistance. This article describes the status of understanding concerning the magnitude of this number for various types of adherent film on either brittle or ductile substrates. Important effects of elastic properties, substrate thickness and yield strength are described.

Thickness-Dependent Radiative Properties of Y-Ba-Cu-O Thin Films

1992 ◽  
Vol 114 (1) ◽  
pp. 227-233 ◽  
Author(s):  
P. E. Phelan ◽  
G. Chen ◽  
C. L. Tien
Keyword(s):  
Thin Film ◽  
Thin Films ◽  
Film Thickness ◽  
Room Temperature ◽  
High Temperature Superconductors ◽  
Normal Incidence ◽  
Radiative Properties ◽  
Continuous Slab ◽  
Optimal Value ◽  
Film Substrate

Some applications of high-temperature superconductors where their radiative behavior is important, such as bolometers, optically triggered switches and gates, and space-cooled electronics, require the superconductor to be in the form of a very thin film whose radiative properties cannot be adequately represented by a semi-infinite analysis. Two properties of particular importance are the film absorptance and the combined film/substrate absorptance, which are crucial to the operation of many devices. Here, calculations of the spectral, normal-incidence absorptance of superconducting-state Y-Ba-Cu-O films on MgO substrates suggest that a decrease in the film thickness often leads to an increase in both the film and the film/substrate absorptance. Furthermore, both can exhibit a maximum at some optimal value of film thickness. Room-temperature experiments verify the qualitative features of the spectral film/substrate absorptance, indicating the assumption that the film is a smooth, continuous slab with a refractive index equal to that of well-aligned bulk Y-Ba-Cu-O is valid, at least in the normal state and for films as thin as 35 nm.

Experimentelle Realisierung der Beziehung I~sin2 x/x2 auf röntgenographischem Wege / Experimental Verification of I ~ sin2 x/x2 by X-Ray Diffraction Measurements

1979 ◽  
Vol 34 (11) ◽  
pp. 1369-1370 ◽  
Author(s):  
W. Fischer ◽  
P. Wissmann
Keyword(s):  
Thin Films ◽  
Film Thickness ◽  
Experimental Verification ◽  
X Ray Diffraction ◽  
X Ray ◽  
Order Of Magnitude ◽  
The Right ◽  
Right Order

It is shown that the equation I ~ sin2 x/x2 well-known from light optics can be proved experimentally even by x-ray diffraction measurements on thin films. All side maxima appear with the right order of magnitude if an optimal film thickness of about 90 Å is chosen

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