R-3 Repository :: Browsing by Author "Brotzen, Franz R."

Browsing by Author "Brotzen, Franz R."

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A study of liquid enhanced creep in porous potassium chloride
(1984) Sheikh, Gholamreza; Pharr, George M.; Brotzen, Franz R.; McLellan, Rex B.
This research was a study of liquid enhanced creep in cold compressed potassium chloride whose grain boundaries were filled with saturated aqueous solution of KC1. This liquid was found to greatly accelerate the rate of creep in the material. It was found that two independent deformation mechanisms operate. The first occurs at low stresses (.163 MPa and below) and it is characterized by a linear stress dependence. The second mechanism dominates at higher stresses (.32 MPa and above), and is characterized by a stress exponent of two. The mechanisms are documented in terms of differences in volumetric strain behavior, creep ductility, and grain size dependence. It is suggested that the low stress mechanism is a diffusional one, similar to Coble creep with the liquid acting as a rapid diffusion path for transport of the solid. The high stress mechanism is not yet clearly understood, but is shown to involve grain boundary sliding accomodated by internal cavitation.
Absorption of ultrasonic and hypersonic waves in LiF single crystals
(1964) Goodell, Joseph P. N; Roberts, John M.; Brotzen, Franz R.
Attenuation of ultrasonic-hypersonic stress waves in LiF single crystals is analyzed. As a mechanism for attenuation the vibrating pinned-dislocation model of Koehler is treated; a resonant peak in attenuation vs frequency was sought. Some other mechanisms, including temperature dependence, are considered. Various causes of modulation of the exponential decay of the acoustic wave are discussed.
An investigation of the mechanism underlying delayed electron emission
(1959) Clayton, Richard Nelson; Brotzen, Franz R.
Electron emission from aluminum was observed during isochronal annealing after deformation at a low temperature, and during isothermal annealing after quenching from a high temperature. The results were compared with theory. Approximate values of the activation energies for the process were derived. A possible mechanism underlying the phenomenon was suggested. The electrical resistance of aluminum wires was also measured during isochronal annealing after deformation at a low temperature. A mechanism was suggested to explain the results.
Characterization of VLSI interconnect materials: Mechanical behavior, time-dependent plasticity, and electromigration
(1989) Rosenmayer, Charles Thomas; Brotzen, Franz R.
Various thin film metallizations were tested in order to gain insight into their performance as VLSI interconnects. Biaxial stress-strain test results exhibited limited ductility, even for pure FCC metals such as copper and aluminum. This may be caused by the columnar structure which does not present the same resistance to crack propagation as a random polycrystalline structure. A Hall-Petch relationship determined for bulge testing of pure aluminum is comparable to another worker's results for films tested by the substrate curvature method. Al-Cu(2%) alloys are shown to have a response to precipitation hardening similar to that of bulk material of the same composition. Uniaxial tension testing of thin films is problematic because of wrinkles and edge defects associated with sample preparation. Electromigration damage in Al-Si(1%) is accelerated by the presence of a tensile stress. Activation energies for creep of aluminum and Al-Cu(2%) are nearly identical to those determined in long term electromigration testing of 5 $\mu$m interconnect stripes.
Corrosion susceptibility of thin films
(1994) Hernandez, Sandra Emilia; Brotzen, Franz R.
The corrosion susceptibility of Al thin-film metallizations in an aqueous solution containing chlorine was measured. DC polarization techniques were used to determine the corrosion behavior of Al thin-film metallizations, Al-alloy thin-film metallizations and Al thin-film metallizations deposited on CVD W and sputtered W-Ti(10%) barrier layers. A galvanic series was developed by listing the stable open-circuit potentials for several metallizations, barrier metals and metallization/barrier-layer couples immersed in a 2000 ppm NH$\sb4$Cl electrolyte. Barrier layers of CVD W and sputtered W-Ti(10%) influenced the corrosion behavior of Al metallizations deposited on their surface. Results were discussed in terms of the galvanic couple formed between the metallization and the barrier layer, as well as the difference in surface topographies of CVD W and sputtered W-Ti(10%). The rough surface inherent on CVD W causes localized variation in metallization thickness and may provide sites where the W layer is exposed to the electrolyte, thereby acting as an efficient cathode. These results were substantiated with SEM photomicrographs. Electrochemical Impedance Spectroscopy (EIS) and DC polarization techniques were used to study the effect of increasing film thickness and grain size on the corrosion behavior of Al thin films. In general, as the film thickness is increased, the overall resistance to corrosion improves. The increase in corrosion resistance is attributed to an enlargement of the grain size, a result of the thin-film deposition process. As the grain size is increased, there is a reduction in the effective grain boundary area, which is the most prominent place were defects can be created or accumulated, thus rendering the oxide layer weak and promoting corrosion. The effect of grain size on the corrosion resistance of the films could not be determined, since the films were pitting upon immersion in the electrolyte.
Diffusion of hydrogen in metal membranes deformed in tension
(1984) Lee, Kelly A. (b. 1976); McLellan, Rex B.; Brotzen, Franz R.; Walker, William F.
Three well known electrochemical techniques were used to study the diffusion of hydrogen in tensilely deformed iron and nickel membranes. Constant current permeation tests, current pulse tests and potentiostatic depletion tests were performed to determine which test produced the most reliable and reproduceable data. The bulk lattice diffusivity in annealed nickel at 22°C was found to be 3.24 X 1 cm2/sec while the bulk lattice diffusivity in annealed iron at 21°C was found to be 1.59 X 1”6 cm2/sec.
Dynamic resistivity measurements on rapidly-strained copper
(1960) Dunlap, Charles Preston; Brotzen, Franz R.
Dynamic resistivity measurements were conducted on copper wires which were rapidly deformed in the plastic range. Of major interest were the instantaneous changes in the resistivity of the metal immediately after the straining was abruptly halted. Records of resistivity change versus time were obtained at three different temperatures. At each temperature, tests were conducted for varying values of strain in an attempt to deduce any dependence of the resistivity change on strain. It was observed that at each temperature, the resistivity decreased rapidly from a maximum value to an equilibrium value. The only useable results were those obtained at room temperature, and these are interpreted in terms of the diffusion of point imperfections to sinks, where they are annihilated.
Effect of vibrations on the yield strength of a low carbon steel
(1957) Nevill, Gale E., 1933-; Brotzen, Franz R.
Experimental results show that, when a specimen is subjected to vibration in the frequency range from 15 kc to 80 kc, the steady stress necessary to cause plastic deformation is appreciably reduced. This reduction is examined under different conditions of vibrational amplitude, frequency, strain, and temperature. Several possible explanations for this decrease in yield strength have been considered on the basis of dislocation theory. A discussion and a detailed picture of the responsible mechanism are included.
Electrical resistivity measurements of deformed molybdenum crystals
(1964) Whitmire, Larry Don; Brotzen, Franz R.
Single crystals of molybdenum were deformed in tension at 195°K, 273°K, 373°K and 473°K. The influence of deformation temperature and intermediate annealing treatments at 473°K and 422°K on the electrical resistivity was investigated. All resistivity measurements were made at 4.2°K. The results indicated that: (1) Point defects are created during deformation at 195°K and 273°K; (2) The rate with respect to strain at which these defects are produced is an inverse function of the deformation temperature; (3) Some or all of the point defects are mobile at 422°K and either diffuse together or to dislocations, and (4) This movement of the point defects does not affect the flow stress. No definite conclusion was reached on the dislocation model responsible for the results.
Electron emission from aluminum as a result of plastic strain
(1958) Voss, William D. von; Brotzen, Franz R.
Aluminum was strained in tension under a Geiger counter. Electron emission associated with plastic deformation and subsequent delayed emission was observed. The specimens were illuminated during both the growth and decay cycles. The emission rate, dN/dt, increased with time, to measured from the start of the strain cycle and could be described by an equation of the form dN/dt = K tn. The emission decay was approximately exponential. The emission yield increased with higher strain rates. Prior deformation increased the emission obtained in subsequent strain increments.
Electrostatic adhesion tester for thin film conductors
(1999-12-14) Griffin, Alfred J., Jr.; Brotzen, Franz R.; Callahan, Daniel L.; Yang, Haining S.; Rice University; United States Patent and Trademark Office
A electrostatic adhesion tester for thin film conductors. In one embodiment, a device is provided for testing the adhesion strength of a thin film conductor that has been formed upon a substrate. The device includes an adhesion tester that is primarily comprised of a conducting portion. The conducting portion is applied to the thin film conductor so that it does not physically contact the thin film conductor, but leaves a small space there between. A power supply may further be provided for coupling to either the adhesion tester, the thin film conductor, or both in order to create a potential difference between the conducting portion and the thin film conductor. The potential difference creates an electric field between the conducting portion and the thin film conductor that induces stress in the thin film conductor. A measuring device may also be provided for coupling to the adhesion tester and the thin film conductor in order to measure an electrical parameter of the electric field, which is indicative of the adhesion strength.
Electrostatic adhesion testing of metallizations on silicon substrates
(1997) Yang, Haining Sam; Brotzen, Franz R.
A novel technique is developed to measure quantitatively the adhesion strength of metallizations deposited on substrates such as silicon. Electrostatic adhesion testing employs electrostatic forces to generate delaminating stresses in thin metallic films. The interfacial adhesion strength is readily calculated from the electrode geometry and the applied electrostatic field at failure. Unlike other adhesion tests, this technique does not require any mechanical contact and is virtually independent of the plastic deformation of the film. Furthermore. this test provides direct strength measurements as opposed to work or energy of adhesion measurements obtained by the common peel-test. The adhesion strengths of several metallizations (Cu, Al, Al-Cu alloy, and TiN) are characterized using this electrostatic technique. The distribution of stress-at-failure data follows Weibull statistics. Field emission scanning electron microscopy reveals that films are delaminated in a micro-blister-type mode. Annealing of metallizations causes reactions and changes flaw distributions. The presence of brittle compounds near the interface may create easy fracture paths and can act as stress concentrators to initiate and propagate the fracture. These stressed areas may lead to localized adhesion failure under applied stress. It is shown that electrostatic adhesion testing is effective in providing quantitative values for the adhesion strengths and failure probabilities of thin-film metallizations.
Impedance spectroscopy response of aluminum-copper-silicon alloys
(1991) Griffin, Alfred Joseph, Jr.; Brotzen, Franz R.
The effect of increased Cu and Si additions and heat treatment on the polarization resistance, oxide-layer/double-layer capacitance, open circuit potential and breakdown potential of Al-Cu-Si alloys was evaluated. Electrochemical impedance spectroscopy and DC polarization techniques were combined with mechanical property evaluations to determine the relationship between the microstructure of Al-Cu-Si alloys and the ability of their oxide layer to provide protection against corrosion in an aqueous 5% NH$\sb4$Cl solution. Alloys were investigated in both the solution-treated and artificially aged conditions. The solution-treatment procedure involved heating the alloys to 550$\sp\circ$C for 30 minutes and subsequently water-quenching. Artificial aging was carried out at 250$\sp\circ$C. Increased aging times of 1, 2, 8 and 32 hours at 250$\sp\circ$C were employed on Al-Cu(2%), Al-Si(2%) and Al-Cu(2%)-Si(2%) alloys in order to correlate the observed electrochemical behavior with the precipitation strengthening reactions which occur during age-hardening. These precipitation reactions govern the resultant microstructure and determine the mechanical behavior, electrochemical behavior and type of corrosion attack observed in Al-Cu-Si alloys. In general, an increase in the susceptibility to pitting corrosion was correlated to a decrease in the protective oxide layer thickness brought about as a result of increased Cu and Si additions in solution-treated alloys and the precipitation of Guinier-Preston zones in age-hardened alloys. Cu and Si atoms at the metal/oxide interface inhibit the diffusion of Al$\sp{+3}$ ions to the oxide/electrolyte interface thereby limiting the oxide-layer thickness. Increased aging times, leading to the formation of Guinier-Preston zones and a concomitant age-hardening peak, also decrease the total number of Al$\sp{+3}$ ions available for passivation and thereby decrease the oxide-layer thickness. Consequently, the oxide-layer/double-layer capacitance and the polarization resistance of the alloys are correlated to changes in the oxide-layer thickness and the loss in continuity of the oxide-layer with overaging. In addition, the open-circuit and breakdown potentials and the type of corrosion attack observed during anodic DC polarization scans was related to the type of alloying element and their distribution.
Microcreep of molybdenum crystals
(1965) Herring, Robert Bruce; Brotzen, Franz R.
Molybdenum single crystals 1/8 inch in diameter were prepared by a zone-melting technique. Crystals were tested in tension in a special creep machine using a very sensitive capacitance extensometer. Flow stress was measured on an Instron machine. Microcreep of the crystals was studied at stresses below half the macroscopic flow stress in the temperature range 200° to 300°K. at resolved shear strains of below 5%. The creep following addition of a stress increment was found to have two parts. In the initial portion the creep rate decreased rapidly, but approached a constant rate in from one to ten minutes. The stresses used produced constant creep rates in the range 10-9 to 10-6 sec.-1. The effect of temperature, strain, and effective stress on that rate was studied. The effective stress is the externally applied stress minus the internal back-stress. The internal stress was measured by finding the stress at which forward creep balanced backward strain recovery. The constant creep rate, following the initial creep, obeyed an equation of the form A sin h(v times T times * over K times T) as predicted by Alefeld and others for creep at low effective stresses. The activation volume v was found to be in the range 15 to 40 b3, decreasing with strain and decreasing at lower temperatures. The parameter A contains the number of activable dislocation segments. The increase of A with strain was proportional to the increase of dislocation density as reported by Lawley and Gaigher. From the temperature dependence of the parameter A, the activation energy for the constant rate microcreep was found to be on the order of 0.1 ev. Results indicate that higher values obtained by other investigators for deformation of b.c.c. metals arises from a neglect of the change of the internal stress. The internal stress was found to rise strongly at low temperature with the same temperature dependence as that of the macroscopic flow stress. Extrapolation showed the internal stress should approach zero at 360°K. which is the point at which the flow stress of molybdenum has been found to become temperature independent. The internal stress did not appear to be an innate property of the b.c.c. lattice, but developed during small amounts of strain. Indications were found that the internal stress then decreases after the material is unloaded or during a return of the material to higher temperature. No detailed model for the creep process or for the recovery of the internal stress is presented. However, it is thought that cross-slip of screw dislocations plays an important role. It was concluded that the strong temperature dependence of the flow stress reflects a very high rate of work-hardening which strongly increases the internal stress during strains of 10-3 or less.
Mixed P and N type conduction in RF sputtered Hg1-xCdXTe thin films
(1983) Liou, Tain-I; Wilson, William L.; Estle, Thomas L.; Brotzen, Franz R.
RF sputtered HgjCdTe thin films were deposited on <111> silicon substrates. Different values of negative bias were applied to the film during growth. X-ray diffraction was used to investigate the crystal structure of the films. Van Der Pauw and Hall measurements were used respectively to obtain resistivities and carrier concentrations of films at room temperature (3°K). Carrier concentration variation with temperature was also measured. A series of films were deposited with different substrate temperatures in order to investigate the effect on crystal structure and electrical properties. When substrate bias was increased, it was found that the film thickness decreased» the crystallographic order of the films became worse, and the room temperature resistivity increased. Measurement of carrier concentration versus temperature between 77°K and 3°K showed the films to be p type when the temperature was around 77°E and n type at high temperatures. It was also found that when the substrate temperature was increased during deposition, the crystal structure improved somewhat. Room temperature resistivity decreased, and the carrier type gradually changed from n type to p type as the deposition temperature was increased. A theoretical model using both a non-degenerate approximation as well as taking into account degenerate considerations was developed to compare with the experimental data.
Observation of dislocations in molybdenum
(1966) Loesch, Herbert William; Brotzen, Franz R.
Single crystals of molybdenum were strained in direct shear on (110) planes along the [111] direction. Crystals were sheared to approximately 5, 10, 20, and 40 percent shear strain at 195°K, 300°K, and 373°K, and to 2 and 6 percent shear strain at 78°K. Specimens taken from the (110) shear plane were examined in transmission electron microscopy. The dislocation structure was examined at each strain and temperature increment, and measurements of the dislocation density and the density of jogs on primary screw dislocations were made. The results indicated that: (1) The dislocation density of molybdenum single crystals deformed in shear increases with strain at all temperatures investigated except 300°K. (2) This increase in p was linear, and as the deformation temperature is lowered, the rate of increase is accelerated. (3) The density of jogs on primary screw dislocations varies with strain and temperature much as does the dislocation density. (4) Conservative motion of jogs on screw dislocations becomes appreciable above 300°K. (5) The ease and scale of cross-slip of screw dislocations increases with increasing temperature. (6) The amount of secondary slip in crystals oriented for direct shear on (110) planes increases as deformation temperature decreases. (7) At l95°K and 300°K, the proportion of edge dislocation length to screw dislocation length increases as strain and tangling increase. No definite conclusion was reached on the dislocation mechanism controlling the flow stress.
Primary creep of polycrystalline copper and determination of the activation volume
(1959) Youngblood, J. L. (James Luther), 1930-; Brotzen, Franz R.
Creep experiments were conducted using high-purity polycrystalline copper at 78°K and 300°K. The results arc analyzed in terms of an intersection mechanism between the moving and forest dislocations. The activation volume is found to be inversely proportional to the strain, and to increase with temperature. These effects are discussed in terms of the dislocation density and the stacking fault width.
Stacking faults in platinum
(1959) Taranto, Jak; Brotzen, Franz R.
Determination by X-ray techniques of stacking-fault densities in platinum was attempted. Heavily deformed platinum was annealed under varying conditions of temperature and time. The X-ray method used for measuring stacking-fault densities was found to lack accuracy for the unequivocal determination of the type of thermal activation process that leads to the loss of stacking faults during annealing. Results suggested that the process may be a first order process with an activation energy of 0.5 ± 0.3 ev. This activation energy is sufficient for extended dislocations to cross each other in platinum, with the formation of jogs. Quenched-in vacancies were found to have no detectable effect on X-ray reflections.
Statistical thermodynamics of one dimensional two component harmonic lattices
(1962) McNeil, Michael B. (Michael Brewer), 1938-; Curl, Robert F., Jr.; Kilpatrick, John E.; Brotzen, Franz R.
The effect of lattice vacancies on the elastic modulus
(1958) Folweiler, Robert Cooper; Brotzen, Franz R.
The effect of quenched-in vacancies upon the elastic modulus of aluminum ma investigated. Equipment for dynamically measuring the change in elastic modulus was developed for the purpose. It was demonstrated that the presence of lattice vacancies will reduce the elastic modulus. This change in elastic modulus was investigated as a function of the number of vacancies and the annealing of vacancies at room temperature. A comparison is made with theoretically derived results.

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