Selective-Area Growth of Heavily \u3cem\u3en\u3c/em\u3e–Doped GaAs Nanostubs on Si(001) by Molecular Beam Epitaxy

Using an aspect ratio trapping technique, we demonstrate molecular beam epitaxy of GaAs nanostubs on Si(001) substrates. Nanoholes in a SiO2 mask act as a template for GaAs-on-Si selective-area growth(SAG) of nanostubs 120 nm tall and ≤100 nm in diameter. We investigate the influence of growthparameters including substrate temperature and growth rate on SAG. Optimizing these parameters results in complete selectivity with GaAsgrowth only on the exposed Si(001). Due to the confined-geometry, strain and defects in the GaAs nanostubs are restricted in lateral dimensions, and surface energy is further minimized. We assess the electrical properties of the selectively grownGaAs nanostubs by fabricating heterogeneous p+–Si/n+–GaAs p–n diodes

Cirurgia para o controle de danos: Sua evolução durante os últimos 20 anos

In less than twenty years, what began as a concept for the treatment of exsanguinating truncal trauma patients has become the primary treatment model for numerous emergent, life threatening surgical conditions incapable of tolerating traditional methods. Its core concepts are relative straightforward and simple in nature: first, proper identification of the patient who is in need of following this paradigm; second, truncation of the initial surgical procedure to the minimal necessary operation; third, aggressive, focused resuscitation in the intensive care unit; fourth, definitive care only once the patient is optimized to tolerate the procedure. These simple underlying principles can be molded to a variety of emergencies, from its original application in combined major vascular and visceral trauma to the septic abdomen and orthopedics. A host of new resuscitation strategies and technologies have been developed over the past two decades, from permissive hypotension and damage control resuscitation to advanced ventilators and hemostatic agents, which have allowed for a more focused resuscitation, allowing some of the morbidity of this model to be reduced. The combination of the simple, malleable paradigm along with better understanding of resuscitation has proven to be a potent blend. As such, what was once an almost lethal injury (combined vascular and visceral injury) has become a survivable one

Interface Evolution of Au-Au Thermocompression Bonding and Nanotwins

Thermocompression bonded gold-gold (Au-Au) interfaces were investigated using electron microscopy to study the micro- and nanostructure post-bonding. Analysis of scanning electron microscopy (SEM) images of Au-Au interfaces at different bonding temperatures, ranging from 150 °C to 250 °C, produced a relationship between the size, shape and distribution of interfacial voids and the quality of the bond. The lowest bonding temperature, 150 °C, had the highest linear and area fraction of voids, as measured from cross-sectional and plan-view SEM images, respectively. The 250 °C bonded devices had the highest hermetic test yield and the lowest void linear and area fractions of the temperatures measured. Cross sectional images of the voids in the 250 °C sample show that voids appear to exist at the triple boundary between the bonding interface and two grains on one side of the interface. Transmission electron microscopy (TEM) was used to investigate the growth of grains in Au-Au thermocompression bonded interfaces where one of the Au layers is nanotwinned (ntAu). During bonding, the ntAu was shown to partially “detwin”, resulting in a large grain that extends across the bonding interface, which may be indicative of high quality bonds. TEM images of the interface identified grains in the non-nanotwinned Au layer that either did or did not extend across the interface and electron diffraction was used to determine the orientation of each grain. The grains which had (111) planes oriented within 17° of the (111) plane in the ntAu layer grew across the interface while those with larger orientation angles did not. There was no correlation between cross-interfacial growth and orientation of the (100) plane. Additionally, gallium arsenide (GaAs) nanostubs deposited on silicon (Si) were investigated to study the production of stacking faults, including nanotwins, at different growth temperatures (590 °C, 605 °C and 620 °C) and its possible role as a strain relaxation process in the latticed-mismatched GaAs-Si interface. All nanostubs imaged using TEM showed stacking faults, with the highest area fraction of stacking faults in the 605 °C sample. This sample also was the only temperature to produce imaged nanotwins. The strain the GaAs was measured using the fast Fourier transform (FFT) of the TEM lattice images and was found to be lowest in the 605 °C, leading to a potential correlation between stacking faults and/or nanotwins and strain relaxation

Interface Evolution of Au-Au Thermocompression Bonding and Nanotwins

Thermocompression bonded gold-gold (Au-Au) interfaces were investigated using electron microscopy to study the micro- and nanostructure post-bonding. Analysis of scanning electron microscopy (SEM) images of Au-Au interfaces at different bonding temperatures, ranging from 150 °C to 250 °C, produced a relationship between the size, shape and distribution of interfacial voids and the quality of the bond. The lowest bonding temperature, 150 °C, had the highest linear and area fraction of voids, as measured from cross-sectional and plan-view SEM images, respectively. The 250 °C bonded devices had the highest hermetic test yield and the lowest void linear and area fractions of the temperatures measured. Cross sectional images of the voids in the 250 °C sample show that voids appear to exist at the triple boundary between the bonding interface and two grains on one side of the interface. Transmission electron microscopy (TEM) was used to investigate the growth of grains in Au-Au thermocompression bonded interfaces where one of the Au layers is nanotwinned (ntAu). During bonding, the ntAu was shown to partially “detwin”, resulting in a large grain that extends across the bonding interface, which may be indicative of high quality bonds. TEM images of the interface identified grains in the non-nanotwinned Au layer that either did or did not extend across the interface and electron diffraction was used to determine the orientation of each grain. The grains which had (111) planes oriented within 17° of the (111) plane in the ntAu layer grew across the interface while those with larger orientation angles did not. There was no correlation between cross-interfacial growth and orientation of the (100) plane. Additionally, gallium arsenide (GaAs) nanostubs deposited on silicon (Si) were investigated to study the production of stacking faults, including nanotwins, at different growth temperatures (590 °C, 605 °C and 620 °C) and its possible role as a strain relaxation process in the latticed-mismatched GaAs-Si interface. All nanostubs imaged using TEM showed stacking faults, with the highest area fraction of stacking faults in the 605 °C sample. This sample also was the only temperature to produce imaged nanotwins. The strain the GaAs was measured using the fast Fourier transform (FFT) of the TEM lattice images and was found to be lowest in the 605 °C, leading to a potential correlation between stacking faults and/or nanotwins and strain relaxation

The Synergistic Roles of Temperature and Pressure in Thermo-Compression Bonding of Au

Abstract Au-Au thermocompression bonding is a widely used technique for a variety of applications including hermetic sealing and packaging at a fine pitch. We have investigated the roles of pressure and temperature individually at different pressures (15 -100 MPa) and temperatures (150 and 250° C) of sputter deposited 1.2 μm thick Au thin films using a flattening technique. The initial surface root mean square (RMS) roughness of deposited films was 3-5 nm. Void morphology and the evolution of the interface was studied using atomic force microscopy. Power spectral density function plots were used to study variation in asperities at the surface. The void morphology and evolution was different when flattening and bonding at different temperatures and pressures.acceptedVersio

Characterization of interfacial morphology of low temperature, low pressure Au–Au thermocompression bonding

Au-Au thermocompression bonding is a versatile technique of high interest for a variety of applications. We have investigated Au-Au bonding using sputter deposited Au films under conditions of low temperature (150-250 °C) and low bonding pressure (∼3 MPa) for short times (15 min). The combination of low temperature and short times is important for applications involving both hermetic sealing and packaging scaling. The initial surface roughness of the Au film was in the 3-5 nm range with peak-to-valley heights of 20-30 nm and a lateral correlation length of ∼400 nm. For samples bonded at 150 °C, the void morphology at the bonded interface was related to the initial surface roughness. The void morphology was different when bonding at the higher temperatures: the void length (along the bonded interface) decreased significantly but the void height (perpendicular to the interface) increased. These results can be understood in terms of a combination of increased surface Au diffusivity and decreased yield stress and elastic modulus with increased bonding temperature. © 2018 The Japan Society of Applied Physics.acceptedVersio

The Synergistic Roles of Temperature and Pressure in Thermo-Compression Bonding of Au

Abstract Au-Au thermocompression bonding is a widely used technique for a variety of applications including hermetic sealing and packaging at a fine pitch. We have investigated the roles of pressure and temperature individually at different pressures (15 -100 MPa) and temperatures (150 and 250° C) of sputter deposited 1.2 μm thick Au thin films using a flattening technique. The initial surface root mean square (RMS) roughness of deposited films was 3-5 nm. Void morphology and the evolution of the interface was studied using atomic force microscopy. Power spectral density function plots were used to study variation in asperities at the surface. The void morphology and evolution was different when flattening and bonding at different temperatures and pressures