Evidence for phonon hardening in laser-excited gold using x-ray diffraction at a hard x-ray free electron laser.

Studies of laser-heated materials on femtosecond timescales have shown that the interatomic potential can be perturbed at sufficiently high laser intensities. For gold, it has been postulated to undergo a strong stiffening leading to an increase of the phonon energies, known as phonon hardening. Despite efforts to investigate this behavior, only measurements at low absorbed energy density have been performed, for which the interpretation of the experimental data remains ambiguous.

Investigation of mechanical properties and structural integrity of graphene aerogels molecular dynamics simulations.

Graphene aerogel (GA), a 3D carbon-based nanostructure built on 2D graphene sheets, is well known for being the lightest solid material ever synthesized. It also possesses many other exceptional properties, such as high specific surface area and large liquid absorption capacity, thanks to its ultra-high porosity. Computationally, the mechanical properties of GA have been studied by molecular dynamics (MD) simulations, which uncover nanoscale mechanisms beyond experimental observations.

A Laterally Vibrating Lithium Niobate MEMS Resonator Array Operating at 500 °C in Air.

This paper reports the high-temperature characteristics of a laterally vibrating piezoelectric lithium niobate (LiNbO; LN) MEMS resonator array up to 500 °C in air. After a high-temperature burn-in treatment, device quality factor () was enhanced to 508 and the resonance shifted to a lower frequency and remained stable up to 500 °C. During subsequent in situ high-temperature testing, the resonant frequencies of two coupled shear horizontal (SH0) modes in the array were 87.

Nanoarchitectonics for Wide Bandgap Semiconductor Nanowires: Toward the Next Generation of Nanoelectromechanical Systems for Environmental Monitoring.

Semiconductor nanowires are widely considered as the building blocks that revolutionized many areas of nanosciences and nanotechnologies. The unique features in nanowires, including high electron transport, excellent mechanical robustness, large surface area, and capability to engineer their intrinsic properties, enable new classes of nanoelectromechanical systems (NEMS). Wide bandgap (WBG) semiconductors in the form of nanowires are a hot spot of research owing to the tremendous possibilities in NEMS, particularly for environmental monitoring and energy harvesting.

An approach for the measurement of the bulk temperature of single crystal diamond using an X-ray free electron laser.

We present a method to determine the bulk temperature of a single crystal diamond sample at an X-Ray free electron laser using inelastic X-ray scattering. The experiment was performed at the high energy density instrument at the European XFEL GmbH, Germany. The technique, based on inelastic X-ray scattering and the principle of detailed balance, was demonstrated to give accurate temperature measurements, within [Formula: see text] for both room temperature diamond and heated diamond to 500 K.

Sensitivity of 2DEG-based Hall-effect sensors at high temperatures.

The magnetic sensitivity of Hall-effect sensors made of InAlN/GaN and AlGaN/GaN heterostructures was measured between room temperature and 576 °C. Both devices showed decreasing voltage-scaled magnetic sensitivity at high temperatures, declining from 53 mV/V/T to 8.3 mV/V/T for the InAlN/GaN sample and from 89 mV/V/T to 8.

Monolithic mtesla-level magnetic induction by self-rolled-up membrane technology.

Monolithic strong magnetic induction at the mtesla to tesla level provides essential functionalities to physical, chemical, and medical systems. Current design options are constrained by existing capabilities in three-dimensional (3D) structure construction, current handling, and magnetic material integration. We report here geometric transformation of large-area and relatively thick (~100 to 250 nm) 2D nanomembranes into multiturn 3D air-core microtubes by a vapor-phase self-rolled-up membrane (S-RuM) nanotechnology, combined with postrolling integration of ferrofluid magnetic materials by capillary force.

Significant Phonon Drag Enables High Power Factor in the AlGaN/GaN Two-Dimensional Electron Gas.

In typical thermoelectric energy harvesters and sensors, the Seebeck effect is caused by diffusion of electrons or holes in a temperature gradient. However, the Seebeck effect can also have a phonon drag component, due to momentum exchange between charge carriers and lattice phonons, which is more difficult to quantify. Here, we present the first study of phonon drag in the AlGaN/GaN two-dimensional electron gas (2DEG).

A Single Input Multiple Output (SIMO) Variation-Tolerant Nanosensor.

Successful transition to commercialization and practical implementation of nanotechnology innovations may very well need device designs that are tolerant to the inherent variations and imperfections in all nanomaterials including carbon nanotubes, graphene, and others. As an example, a single-walled carbon nanotube network based gas sensor is promising for a wide range of applications such as environment, industry, and biomedical and wearable devices due to its high sensitivity, fast response, and low power consumption. However, a long-standing issue has been the production of extremely high purity semiconducting nanotubes, thereby contributing to the delay in the market adoption of those sensors.

Characterization of the piezoresistance in highly doped p-type 3C-SiC at cryogenic temperatures.

This paper reports on the piezoresistive effect in p-type 3C-SiC thin film mechanical sensing at cryogenic conditions. Nanothin 3C-SiC films with a carrier concentration of 2 × 10 cm were epitaxially grown on a Si substrate using the LPCVD process, followed by photolithography and UV laser engraving processes to form SiC-on-Si pressure sensors. The magnitude of the piezoresistive effect was measured by monitoring the change of the SiC conductance subjected to pressurizing/depressurizing cycles at different temperatures.

In situ ultraviolet shock radiance measurements using GaN-on-sapphire photodetectors.

Gallium nitride (GaN)-on-sapphire photodetectors are used to measure the ultraviolet (UV) radiance behind a shock wave in support of atmospheric entry sensing technologies. DC spectral response characterization of the GaN-based photodetectors shows a peak response around 365 nm with an UV/visible rejection of an order of magnitude. To conduct in situ measurements of UV shock-layer radiation, the GaN-based photodetectors were installed, without protective packaging, in the test section of a shock tube.

A microfabricated sun sensor using GaN-on-sapphire ultraviolet photodetector arrays.

A miniature sensor for detecting the orientation of incident ultraviolet light was microfabricated using gallium nitride (GaN)-on-sapphire substrates and semi-transparent interdigitated gold electrodes for sun sensing applications. The individual metal-semiconductor-metal photodetector elements were shown to have a stable and repeatable response with a high sensitivity (photocurrent-to-dark current ratio (PDCR) = 2.4 at -1 V bias) and a high responsivity (3200 A/W at -1 V bias) under ultraviolet (365 nm) illumination.

Solar-blind photodetectors for harsh electronics.

We demonstrate solar-blind photodetectors (PDs) by employing AlN thin films on Si(100) substrates with excellent temperature tolerance and radiation hardness. Even at a bias higher than 200 V the AlN PDs on Si show a dark current as low as ~ 1 nA. The working temperature is up to 300°C and the radiation tolerance is up to 10(13) cm(-2) of 2-MeV proton fluences for AlN metal-semiconductor-metal (MSM) PDs.

AlN/3C-SiC composite plate enabling high-frequency and high-Q micromechanical resonators.

An AlN/3C-SiC composite layer enables the third-order quasi-symmetric (QS(3)) Lamb wave mode with a high quality factor (Q) characteristic and an ultra-high phase velocity up to 32395 ms(-1). A Lamb wave resonator utilizing the QS(3) mode exhibits a low motional impedance of 91 Ω and a high Q of 5510 at a series resonance frequency (f(s)) of 2.92 GHz, resulting in the highest f(s)·Q product of 1.

Sodium-independent active potassium reabsorption in proximal tubule of the dog.

Prior studies of proximal tubule reabsorption have failed to distinguish conclusively between a separate active K+ transport system and K+ movement linked to Na+ reabsorption. To attempt to dissociate movement of K+ from Na+ and Ca++, recollection micropuncture experiments were performed in proximal tubules of intact and thyroparathyroidectomized (TPTX) dogs under two different conditions known to inhibit Na+ reabsorption: saline expansion to 5% body wt, and 5 mg/kg acetazolamide. A control hydropenic group was also studied.

Mode of action of parathyroid hormone and cyclic adenosine 3',5'-monophosphate on renal tubular phosphate reabsorption in the dog.

To evaluate the effects of parathyroid hormone and cyclic adenosine monophosphate on proximal tubular sodium and phosphate reabsorption, micropuncture studies were performed on dogs that received a highly purified preparation of parathyroid hormone (PTH), dibutyryl cyclic 3',5'-adenosine monophosphate (cyclic AMP), 5'-AMP, and saline. PTH resulted in a 30-40% inhibition of sodium and phosphate reabsorption in the proximal tubule unassociated with a rise in either total kidney or single nephron glomerular filtration rate (GFR). The bulk of the phosphate rejected proximally was excreted in the final urine while sodium excretion rose minimally despite the marked proximal inhibition, consistent with the presence of reabsorptive sites in the distal nephron for sodium but not phosphate.