Hot deformation and dynamic recrystallization (DRX) behavior of the Cu–Cr–Zr–Ag alloy were studied by hot compressive tests in the 650–950 °C temperature and 0.001–10 s−1 strain rate ranges using Gleeble-1500D thermomechanical simulator. The activation energy of deformation was determined as Q = 343.23 kJ/mol by the regression analysis. The critical conditions, including the critical strain and stress, for the occurrence of DRX were determined based on the alloy strain hardening rate. The critical strain related to the onset of DRX decreases with temperature. The ratios of the critical to peak stress and critical to peak strain were also identified as 0.91 and 0.49, respectively. The evolution of DRX microstructure strongly depends on the deformation conditions in terms of temperature and strain rate. Dislocation generation and multiplication are the main hot deformation mechanisms for the alloy. The addition of Ag can refine the grain and effectively improve the DRX of the Cu–Cr–Zr alloy. It can also inhibit the growth of the DRX grains at 950 °C deformation temperature, making the microstructure much more stable.

To understand the impact that the growth rate has on the residual stress of chemical vapor deposition-grown 3C–SiC heteroepitaxial films on Si substrates, growth experiments were performed. The film thickness was held constant at ∼2.5 μm independent of the growth rate so as to allow for direct film comparison as a function of the growth rate. Stress analysis performed by profilometer curvature measurement, μιχρο-Raman shift analysis and micro-machined freestanding structures, show an apparent disagreement about the stress nature. This incongruity between the experimental data can be explained assuming a strong stress field located in the substrate related to defects generated in the silicon during the growth process.

Ti/AlTiN/Ti-diamondlike carbon (DLC) composite coatings were deposited by mid-frequency magnetron sputtering and Hall ion source-assisted deposition on high-speed steel W18Cr4V substrates. The coating microstructure and mechanical properties, including hardness, elastic modulus, coefficient of friction, and wear properties were investigated by scanning electron microscopy, Raman spectroscopy, scratch and ball-on-disk friction tests, respectively. Fairly smooth composite coating with strong interfacial adhesion and good mechanical properties was produced. The substrate bias increases sp3 bonds contents in the DLC layer, thus coating hardness increased from 14 to 24 GPa and elastic modulus from 190 to 230 GPa with the increased substrate bias. Adhesion of interfaces between Ti-DLC and AlTiN layer, AlTiN and the steel substrate decreased with the substrate bias. The coefficient of friction is between 0.10 and 0.15, except when the substrate bias is 500 V, it is 0.2. Composite coating wear resistance increased with the substrate bias.

The addition of water results in the higher wear rate of gold compared to experiments performed in the ambient environment (approximately 60% humidity). This higher wear rate in water has been observed with the AFM, Hysitron Triboindenter, and additionally in single pass scratch tests performed with the Taber Shear/Scratch tester. These tests were preformed using silicon nitride cantilevers on the AFM and a conical diamond tip in the Taber instrument. Tests performed in the ambient atmosphere resulted in slightly reduced surface roughness, while much higher wear rate was observed in the wear tests performed in water. Ambient scratch tests produced slightly shallower scratch trenches than wet scratches consistently as a function of the varied normal load. Single scan lines provide valuable information about the mechanisms and progression of the nanoscale wear. The different components of scratch friction are investigated to explore the main contributors to the nanoscale scratching of gold.

Having superior mechanical properties, 3C-SiC is one of the target materials for power MEMS applications. Growing 3C-SiC films on Si is challenging, as there is a large mismatch in lattice parameter and thermal expansion between the SiC film and the Si substrate that needs to be accommodated, and results in high residual stress. Residual stress control is critical in MEMS devices as upon feature release it results in substantial deformation.

3C-SiC single crystalline films were deposited on 50 mm (100) and (111) Si substrates in a hot-wall CVD reactor. The film tensile residual stress was so high that it fractured on the (111) Si wafer. The resulting film thickness on the (100) Si wafer was non-uniform, having a linear profile along the growth direction. This presented a challenge of using the substrate curvature method for calculating residual stress. Finite Element Method correction was applied to the Stoney's formula for calculating the residual stress along the wafer radius. Suggestions for reducing the amount of residual stress are made.

Nanoindentation tests using the Berkovich indenter tip were performed on 50 and 200 nm thick polycrystalline gold films deposited on hard substrates. Gold film hardness increased with the indentation depth due to the influence of the substrate. A procedure based on the Joslin-Oliver method was introduced to correct for the substrate effect. The method utilizes the fact that the measured elastic modulus does not change significantly with the indentation depth, which allows reducing the contact area variation used in the hardness calculation.

Chromium oxide coatings were deposited on low-carbon steel by radiofrequency reactive magnetron sputtering at different oxygen flux values. X-ray diffraction, x-ray photoelectron spectroscopy, and high-resolution transmission electron microscopy were used to investigate the microstructure of chromium oxide coatings. Varying oxygen flux changed the coating microstructure; as with increasing oxygen flux the chromium oxide coating undergoes amorphous-to-crystalline transformation. The coating developed strong (300) texture at higher oxygen flux. Hardness, elastic modulus, wear resistance, and adhesion were investigated by nanoindentation and pin-on-disk tests. With changes in the coating microstructure as a function of increased oxygen flux, hardness, elastic modulus, and wear resistance were improved, but its adhesion was weakened.

Electrowetting is a promising method for manipulating small volumes of liquid on a solid surface. This complex phenomenon couples electrical and fluid properties and offers many potential surprises. The complex electrical and capillary interactions in electrowetting are illustrated by an analysis of an electrowetting configuration that produces an oscillating droplet motion from a steady DC voltage input. The paper presents an analysis of the electrowetting forces to explain the oscillation and presents a new method for measuring electrowetting forces using a Hysitron Triboindenter. Initial results are compared with predictions from numerical models and simplified analytical solutions.

Wear behavior of freshly cleaved single crystal calcite (CaCO3) was investigated by continuous scanning using the Hysitron Triboindenter in ambient environment as a function of scanning frequency (1 Hz – 3 Hz) and contact load (2 µN – 8 µN). At lower loads below 4 µN, initiation of the ripples takes place at the bottom of the surface slope, which continue to propagate up the slope as scanning progresses. The orientation of these ripple structures is perpendicular to the long scan direction. As the number of scans increases, ripples become fully developed, and their height and periodicity increase with the number of scans. At 6 µN normal load, tip-induced wear occurs as the tip begins removing the ripple structures with increased number of scan cycles. As the contact load increased further, ripples did not initiate and only tip-induced wear occurred on the surface, and saturated after 20 scans. At 1 Hz frequency wear takes place as material slides towards the scan edges when the tip moves back and forth. Material removal rate increased with contact load and it is observed that the number of scans required to create a new surface is inversely proportional to the contact load. Possible mechanisms responsible for the formation of ripples at higher frequencies are attributed to the slope of the surface, piezo hysteresis, system dynamics, or a combination of effects. The wear regime is due to abrasive wear. Single crystal calcite hardness of 2.8±0.3 GPa and elastic modulus of 75±4.9 GPa were measured using nanoindentation and used to determine the wear mode.

There is a technological need for hard thin films with high elastic modulus and fracture toughness. Silicon carbide (SiC) fulfills such requirements for a variety of applications at high temperatures and for high-wear MEMS. A detailed study of the mechanical properties of single crystal and polycrystalline 3C-SiC films grown on Si substrates was performed by means of nanoindentation using a Berkovich diamond tip. The thickness of both the single and polycrystalline SiC films was around 1-2 μm. Under indentation loads below 500 μN both films exhibit Hertzian elastic contact without plastic deformation. The polycrystalline SiC films have an elastic modulus of 457 GPa and hardness of 33.5 GPa, while the single crystalline SiC films elastic modulus and hardness were measured to be 433 GPa and 31.2 GPa, respectively. These results indicate that polycrystalline SiC thin films are more attractive for MEMS applications when compared with the single crystal 3C-SiC, which is promising since growing single crystal 3C-SiC films is more challenging.

The effects of water on the wear resistance of 3 μm thick sputtered gold film on silicon substrate using contact AFM and a scanning nanoindenter were investigated. In performing wear tests on gold samples in the presence of water, a significant increase in depth of the wear area was observed compared to the same tests performed in the ambient atmosphere (∼55% humidity). These results were obtained using Hysitron Triboindenter on areas of 10×10 μm2 and an Atomic Force Microscope on areas of 1×1 μm2. Nanowear tests were preformed using silicon nitride cantilevers on the AFM and diamond Berkovich or blunt conical tips on the Hysitron. Normal loads used were 2000 μN and 10 μN, respectively. Tests performed in the ambient atmosphere resulted in a slightly reduced surface roughness, while a much higher wear rate was observed in the wear tests performed in water. Additionally, gold surface ripples formed under certain scanning conditions, in water for the Hysitron Triboindenter and in ambient atmosphere for the AFM. Nanoscale stick slip is being investigated as a possible explanation to the rippling phenomenon, and single scan line tests provide valuable information about the mechanisms and progression of the nanoscale wear.

Large out-of-plane displacements can be achieved when compliant mechanisms are utilized in MEMS. While mathematical and macroscopic modeling is helpful in building original designs, the actual MEMS device motion needs to be characterized in terms of the forces and displacements. A nanoindentation apparatus equipped with Berkovich diamond tip was used in an attempt to actuate and characterize the motion of the Bistable Spherical Compliant Micromechanism with a nonlinear (approximately cubic) mechanical response. Based on the obtained lateral force-displacement data it was concluded that the Berkovich diamond tip was too sharp, thus cutting through the polysilicon material of the MEMS device.

This paper describes the nanoindentation technique for measuring sputter-deposited Au and Cu thin films’ mechanical properties at elevated temperatures up to 130 °C. A thin, 5-nm Pt layer was deposited onto the Cu film to prevent its oxidation during testing. Nanoindentation was then used to measure elastic modulus and hardness as a function of temperature. These tests showed that elastic modulus and hardness decreased as the test temperature increased from 20 to 130 °C. Cu films exhibited higher hardness values compared to Au, a finding that is explained by the nanocrystalline structure of the film. Hardness was converted to the yield stress using both the Tabor relationship and the inverse method (based on the Johnson cavity model). The thermal component of the yield-stress dependence followed a second-order polynomial in the temperature range tested for Au and Pt/Cu films. The decrease in yield stress at elevated temperatures accounts for the increased interfacial toughness of Cu thin films.

Argon pressure significantly affects the residual stress in sputter deposited thin films and coatings. In case of W thin films, high residual stresses on the order of 1–2 GPa are quite common. With the rest of sputtering parameters being equal, argon pressure determines the sign and the value of residual stress.

When the amount of stored elastic energy in the film due to the residual stress exceeds the interfacial toughness, fracture normally occurs. Telephone cord buckling delamination blisters are commonly observed in compressed thin films. These mechanically active features form by a loss of adhesion between the film and the substrate due to residual stress relief, and exhibit directional growth under certain conditions. This paper considers telephone cord delamination channels for micro-fluidics applications, as this could to be a valuable, reliable, and inexpensive method of forming open channels.

While spacecrafts experience temperatures from -120 to 110°C on the orbit, their surface reaches extremely high temperatures, well above 1000 °C, during descent into the atmosphere due to aerodynamic heating. Sophisticated insulation systems are designed for thermal protection. One of the steps in designing a protection system is experimental temperature measurements.

Neutron flux induces point defects formation and accumulation in diamond and SiC single crystals, which causes overall lattice expansion. During thermal annealing this process is reversed, so the annealing temperature and time result in the “reduced” lattice parameter (measured by X-Ray diffraction), which allows determining the maximum temperature, if the exposure time is known. This paper describes the use of irradiated single crystal high temperature sensors for measuring temperatures in thermal protection systems during spacecraft descent, as well as other space applications. These additional applications include measuring the furnace temperature during single crystal growth in space at zero gravity, and measuring the rocket combustion chamber turbo pump temperature.

Thin film delamination can occur when the stored elastic energy per unit area in the film due to the residual stress exceeds the interfacial toughness. Telephone cord morphology is commonly observed in delaminating thin films under compressive stresses. Here, the biaxial film stress is partially relieved by film buckling in the direction perpendicular to the telephone cord propagation, and by “secondary” blister buckling in the direction of telephone cord propagation, which results in the sinusoidal fracture patterns.

A superlayer indentation test, in which additional stress is supplied to the crack tip using a nanoindenter, can be used to measure the interfacial toughness. Estimates of the energy release rate for diamond-like carbon (DLC) films on magnetic media were obtained using the superlayer indentation test, as well as the delaminated buckling profiles. The results obtained by these two independent methods are in good agreement with each other. We find the average adhesion energy to be 6 J/m2 for DLC films on magnetic media.

Normally telephone cord blisters “run out of steam” and stop once the interfacial toughness exceeds the strain energy release rate. It is possible to make blisters propagate further by either putting mechanical energy into the system, or by introducing liquids at the crack tip, thus reducing the film interfacial toughness. Environmental species can assist cracking and contribute to thin film delamination, which is readily observed in vintage mirrors. Crack propagation rates on the order of microns per minute were measured for DLC films in different fluid environments. We identify how telephone cord buckling delamination can be used as a test vehicle for studying crack propagation rates and environmentally assisted cracking in thin films.

Many microelectronic chips contain embedded memory arrays. A single SRAM bit-cell contains several transistors. Failure of any of the transistors makes the entire bit-cell inoperable. Dual-beam Focused Ion Beam (FIB) combines the slicing capability of FIB with in-situ SEM imaging. The combination offers unparalleled precision in looking for root causes of failures in microelectronic devices. Once a failure site is located, an FIB lift-off method can be used to prepare a TEM sample containing the area of interest. Further structural, elemental information can then be acquired from the failure site. We report here analyses of single and multiple bit failures in SRAM arrays carried out using FIB/SEM, and in two cases TEM imaging and EDS/PEELS. Root causes of bit failures including remnant seed-layer metal between stacked vias have been identified.

Aluminum and copper are widely used for microelectronic interconnect applications. Interfacial oxides can cause device performance degradation and failure by significantly increasing electrical resistance. Interfacial oxide layers found in Al/Ta and Ta/Cu metal stacks were studied using Transmission Electron Microscopy (TEM) combined with Energy Dispersive Spectroscopy (EDS) and Parallel Electron Energy Loss Spectroscopy (PEELS). The analysis indicates that the observed interfacial oxide layers, Al2O3 and mainly Ta2O5, result from spontaneous reductions of Ta oxide and Cu oxide, respectively. Thermodynamics enables interpretation of the results.

While there are many stress relief mechanisms observed in thin films, excessive residual and externally applied stresses cause film fracture. In the case of tensile stress a network of through-thickness cracks forms in the film. In the case of compressive stress thin film buckling is observed in the form of blisters. Thin film delamination is an inseparable phenomenon of buckling. The buckling delamination blisters can be either circular, straight, or form periodic buckling patterns commonly known as telephone cord delamination morphology.

While excessive biaxial residual stress is the key for causing thin film fracture, either in tension, or compression, it is the influence of the external stress that can control the final fracture pattern. In this paper we consider phone cord buckling delamination observed in compressed W/Si and TiWN/GaAs thin film systems, as well as spiral and sinusoidal though-thickness cracks observed in Mo/Si multilayers under 3-point high-temperature bending in tension.

Due to their highly efficient photo-luminescent (PL) characteristics, the physical properties of rare-earth polytantalates, RETa7O19 (RE=Eu and Y) were further studied. AFM, SEM, HRTEM, x-ray reflectometry, spectroscopic ellipsometry and standard dielectric testing were used to determine film thickness, roughness, index of refraction, band-gap, dielectric constant, leakage current and breakdown field for as-deposited (amorphous) and post-annealed (crystalline) films. Structural and morphological properties of the Film/SiO2/Si interfaces were also examined.