Focused Ion Beam Preparation of Low Melting Point Metals: Lessons Learned From Indium

Indium (In) and other low melting point metals are used as interconnects in a variety of hybridized circuits and a full understanding of the metallurgy of these interconnects is important to the reliability and performance of the devices. This paper shows that room temperature focused ion beam (FIB) preparation of cross-sections, using Ga+ or Xe+ can result in artifacts that obscure the true In microbump structure. The use of modified milling strategies to minimize the increased local sample temperature are shown to produce cross-sections that are representative of the In bump microstructure in some sample configurations. Furthermore, cooling of the sample to cryogenic temperatures is shown to reliably eliminate artifacts in FIB prepared cross-sections of In bumps allowing the true bump microstructure to be observed.

Gas sensors boosted by two-dimensional h-BN enabled transfer on thin substrate foils: towards wearable and portable applications

The transfer of GaN based gas sensors to foreign substrates provides a pathway to enhance sensor performance, lower the cost and extend the applications to wearable, mobile or disposable systems. The main keys to unlocking this pathway is to grow and fabricate the sensors on large h-BN surface and to transfer them to the flexible substrate without any degradation of the performances. In this work, we develop a new generation of AlGaN/GaN gas sensors with boosted performances on a low cost flexible substrate. We fabricate 2-inch wafer scale AlGaN/GaN gas sensors on sacrificial two-dimensional (2D) nano-layered h-BN without any delamination or cracks and subsequently transfer sensors to an acrylic surface on metallic foil. This technique results in a modification of relevant device properties, leading to a doubling of the sensitivity to NO₂ gas and a response time that is more than 6 times faster than before transfer. This new approach for GaN-based sensor design opens new avenues for sensor improvement via transfer to more suitable substrates, and is promising for next-generation wearable and portable opto-electronic devices.

Nanoselective area growth of defect-free thick indium-rich InGaN nanostructures on sacrificial ZnO templates

Nanoselective area growth (NSAG) by metal organic vapor phase epitaxy of high-quality InGaN nanopyramids on GaN-coated ZnO/c-sapphire is reported. Nanopyramids grown on epitaxial low-temperature GaN-on-ZnO are uniform and appear to be single crystalline, as well as free of dislocations and V-pits. They are also indium-rich (with homogeneous 22% indium incorporation) and relatively thick (100 nm). These properties make them comparable to nanostructures grown on GaN and AlN/Si templates, in terms of crystallinity, quality, morphology, chemical composition and thickness. Moreover, the ability to selectively etch away the ZnO allows for the potential lift-off and transfer of the InGaN/GaN nanopyramids onto alternative substrates, e.g. cheaper and/or flexible. This technology offers an attractive alternative to NSAG on AlN/Si as a platform for the fabrication of high quality, thick and indium-rich InGaN monocrystals suitable for cheap, flexible and tunable light-emitting diodes.

Effects of etomidate and hypothermia on cerebral metabolism and blood flow in a canine model of hypoperfusion

Etomidate is a nonbarbiturate hypnotic agent which, like the barbiturates, decreases the cerebral metabolic rate of oxygen consumption (CMRO2) 35-50%. The present studies assessed whether etomidate decreased CMRO2 through temperature-dependent mechanisms and whether the combination of etomidate and moderate hypothermia (28 degrees C) decreased CMRO2 more than hypothermia alone. Nineteen anesthetized dogs were treated with saline, etomidate (burst-suppressive doses), etomidate with hypothermia, or hypothermia alone. Etomidate did not affect (p > 0.05) the mean arterial pressure (MAP, mm Hg) but modestly lowered the heart rate [HR; 124 +/- 6 to 105 +/- 14, (mean +/- SEM); p < 0.05] whereas hypothermia (without or with etomidate) lowered (p < 0.05) both MAP (141 +/- 4 to 116 +/- 5 and 135 +/- 6 to 81 +/- 7) and HR (135 +/- 14 to 84 +/- 3 and 135 +/- 10 to 69 +/- 5, respectively). Etomidate administration did not result in a change (p > 0.05) in the esophageal, brain parenchymal, or subdural temperature. CMRO2 (ml/100 g/min) decreased (p < 0.05) during etomidate administration (3.2 +/- 0.4 to 1.7 +/- 0.2) and hypothermia (3.5 +/- 0.2 to 1.1 +/- 0.2), but the addition of etomidate to hypothermia did not further reduce CMRO2 in the animals (3.1 +/- 0.5 to 1.3 +/- 0.2) despite decreasing their brain hemispheric electrical activity from 9 +/- 1 Hz to a burst-suppressive state.(ABSTRACT TRUNCATED AT 250 WORDS)

Laryngeal compression and stridor as the presenting feature of ruptured thoracic aortic aneurysm. Report of two cases

Two patients are reported in whom rupture of a thoracic aortic aneurysm presented with neck swelling and progressive stridor. Stridor occurred due to compression of the larynx by haematoma tracking up from the mediastinum. The presentation of thoracic aortic aneurysms and of rupture of thoracic aortic aneurysms are discussed with particular reference to mechanisms of cardiovascular and respiratory manifestations. The importance of early control of the airway is emphasised if there is to be any hope of survival from acute rupture.

Fibrous histiocytoma of the larynx

Fibrous histiocytoma is uncommon in the head and neck region and rare in the larynx. Its behaviour is unpredictable. A case is reported in a 54-year-old male which was treated conservatively initially and which recurred several times over a seven year period. During that time the appearances of the lesion changed from those of a densely collagenous, cytologically benign tumour to those of a richly cellular and potentially malignant neoplasm. Laryngectomy was eventually undertaken.