The ubiquitous low-energy excitations, known as two-level tunneling systems (TLSs), are one of the universal phenomena amorphous solids. Low temperature elastic measurements show that $e$-beam silicon ($a\text{\ensuremath{-}}\mathrm{Si}$) contains a variable density TLSs which diminishes growth reaches $400\text{ }\ifmmode^\circ\else\textdegree\fi{}\mathrm{C}$. Structural analyses these $a\text{\ensuremath{-}}\mathrm{Si}$ films become denser and more structurally ordered. We conclude...

The specific heat C of e-beam evaporated amorphous silicon (a-Si) thin films prepared at various growth temperatures T(S) and thicknesses t was measured from 2 to 300 K, along with sound velocity v, shear modulus G, density n(Si), Raman spectra. Increasing results in a more ordered network increases decrease bond angle disorder. Below 20 an excess is seen less than full where it typical solid, both linear term characteristic two-level systems (TLS) additional (non-Debye) T3 contribution....

A silicon nitride membrane-based nanocalorimeter is described for measuring the heat capacity of 30 nm films from 300 mK to 800 K and in high magnetic fields with absolute accuracy approximately 2%. The addenda less than 2 x 10(-7) J/K at room temperature 10(-10) 2.3 K. This more ten times smaller any existing calorimeter suitable thin over this wide range. capacities Cu Au are reported agree bulk values. thermal conductivity low stress substantially thicker membranes while specific enhanced...

We report $3\ensuremath{\omega}$ thermal conductivity measurements of amorphous and nanocrystalline silicon thin films from 85 to 300 K prepared by hot-wire chemical-vapor deposition, where the crystallinity is controlled hydrogen dilution during growth. The film in agreement with several previous reports a variety deposition techniques. as-grown 70% higher increases 35% more after an anneal at $600{\phantom{\rule{0.16em}{0ex}}}^{\ensuremath{\circ}}\mathrm{C}$. They all have similarly weak...

Magnetization measurements of giant negative magnetoresistive amorphous GdxSi1-x ( 0.04<x<0.19) show strong mixed ferromagnetic and antiferromagnetic interactions spin-glass freezing. The appear to be an RKKY-like indirect exchange mediated by the conduction electrons, but are strikingly independent their localization at metal-insulator (MI) transition, presumably because length exceeds inter-Gd distance. susceptibility per Gd atom in paramagnetic state shows a nontrivial dependence on...

The prototype of a radiation hard resistive bolometer has been produced. This was installed in ASDEX Upgrade to test its viability and long term stability tokamak environment.

A microfabricated amorphous silicon nitride membrane-based nanocalorimeter is proposed to be suitable for an x-ray transparent sample platform with low power heating and built-in temperature sensing. In this work, thermal characterization in both air vacuum are analyzed experimentally via simulation. Infrared microscopy thermoreflectance used imaging of the area air. While a reasonably large isothermal found on area, homogeneity entire low, limiting use device as heater stage or other gases....

We have measured the thermal conductivity of amorphous and nanocrystalline silicon films with varying crystalline content from 85 K to room temperature. The were prepared by hot-wire chemical-vapor deposition, where volume fraction is determined hydrogen (H2) dilution ratio processing silane gas (SiH4), R = H2/SiH4. varied 1 10, transform for < 3 mostly larger R. Structural analyses show that nanograins, averaging 2 9 nm in sizes increasing R, are dispersed matrix. increases 0 65% as 10....

Amorphous Nb–Si alloys have a temperature-dependent resistivity which can be tuned over many decades by controlling composition and are used for thin-film thermometers. Annealing at temperatures from 100 to 500 °C produces dramatic but easily controlled increases in resistivity, both magnitude temperature dependence, insulating metallic samples with compositions ranging 8–15 at. %Nb. A transition metal insulator is induced annealing an initially sample. thermal stability against subsequent...

We report magnetization, magnetic susceptibility, and specific-heat measurements of amorphous ${\mathrm{Gd}}_{x}{\mathrm{Y}}_{y}{\mathrm{Si}}_{1\ensuremath{-}x\ensuremath{-}y}$ ternary alloy thin films near the metal-insulator (MI) transition as a function temperature applied field. Samples same moment concentration x but varying conduction-electron $x+y$ were measured to test effect MI on properties. The effective in paramagnetic state (per Gd atom) shows strong dependence composition, with...

Abstract Specific heat measurements from 2 to 300 K of hydrogenated amorphous silicon prepared by hot-wire chemical vapor deposition show a large excess specific at low temperature, significantly larger than the Debye calculated measured sound velocity. The as-prepared films have Schottky anomaly that is associated with metastable hydrogen in network, as well linear and cubic term commonly tunneling two-level systems solids. Annealing 200 °C, temperature enables mobility but not evaporation,...

Chromium plays a key role as spacer layer in the well-studied landmark giant magnetoresistive (GMR) system, Fe/Cr. In these multilayered structures, most often produced through sputtering, density of Cr states at Fe/Cr interface is known to contribute strongly spin-dependent scattering that gives rise GMR behavior. itself holds wealth information about antiferromagnetism due its unique spin-density wave (SDW) By varying preparation conditions, we examine how stress and disorder alter SDW Cr....

The physical nature and concentration of paramagnetic point defects in the dielectrics superconducting planar microwave resonators have been determined using in-situ electron resonance spectroscopy. To perform this work, quality factor parallel plate stripline was measured as a function magnitude magnetic-field applied to electrode surfaces. YBa2Cu3O7−δ thin film electrodes proved be preferred choice over Nb MgB2 because they are readily available small surface resistance (Rs) up high...

The transport properties and microstructure of amorphous GdxSi1−x alloys are presented. conductivity increases from x=0 through the metal-insulator transition (x=14 at.%), up to a dopant concentration 25 at.%. A sharp cusp in magnitude is then observed flattening versus temperature curve occurs at higher concentrations. These results explained terms high-resolution electron micrographs which demonstrate formation nano-crystallites x≥25 identical for annealing a-GdxSi1−x with low Gd concentration.

Direct mapping of the charge transport efficiency polymer solar cell devices using a soft X-ray beam induced current (SoXBIC) method is described. By fabricating on an x-ray transparent substrate, we demonstrate ability to map composition and nanoscale structure within operating device simultaneously measure local via short-circuit current. A simple model calculated compared experimental SoXBIC data PFB:F8BT bulk-heterojunction in order gain greater insight into operation physics.

Author(s): Queen, DR; Liu, X; Karel, J; Wang, Q; Crandall, RS; Metcalf, TH; Hellman, F | Abstract: Light soaking is found to increase the specific heat C and internal friction Q−1 of pure (a-Si) hydrogenated (a-Si:H) amorphous silicon. At lowest temperatures, increases in are consistent with an increased density two-level systems (TLS). The light-induced persists room temperature. Neither sound velocity nor shear modulus change light indicating that Debye unchanged which suggests creates...

Abstract The ubiquitous low-energy excitations are one of the universal phenomena amorphous solids. These dominate acoustic, dielectric, and thermal properties structurally disordered One exception has been a type hydrogenated silicon ( -Si:H) with 1 at.% H. Using low temperature elastic measurements electron-beam evap-orated -Si), we show that TLS can be eliminated in this system as films become denser more ordered under certain deposition conditions. Our results demonstrate not intrinsic...

The nature and concentration of defects near niobium-silicon interfaces prepared with different silicon surface treatments were characterized using current-voltage (I-V), deep level transient spectroscopy (DLTS), secondary ion mass (SIMS). All samples have H, C, O, F, Cl chemical contamination in the Si within 50 nm interface electrically active activation energies 0.147, 0.247, 0.339, 0.556 eV above valence band maximum (E$_{vbm}$). In all cases, defect is dominated by hole trap at...

Specific heat measurements of hydrogenated amorphous silicon prepared by hot-wire chemical vapor deposition show a large density two-level systems at low temperature. Annealing 200 ${}^{\ensuremath{\circ}}\mathrm{C}$, well below the growth temperature, does not significantly affect already-low internal friction or sound velocity, but irreversibly reduces non-Debye specific an order magnitude 2 K, indicating reduction in systems. Comparison with suggests that are uncharacteristically...

In this study, we show that deposited Ge and Si dielectric thin-films can exhibit low microwave losses at single-photon powers sub-Kelvin temperatures (≈40 mK). This loss enables their use in a wide range of devices, including coplanar, microstrip, stripline resonators, as well layers for device isolation, interwiring dielectrics, passivation Josephson junction circuit fabrication. We coplanar resonator structures with narrow trace widths minimal over-etch to maximize the sensitivity tangent...

Germanium thin films are an excellent candidate for use as a low-loss dielectric in superconducting microwave resonators, inter-layer metal wiring dielectric, and passivation layers Josephson junction devices. In Ge/Nb structures deposited at 400 °C, we observe intermixing over much 20 nm. The addition of 10 nm Ta diffusion barrier layer reduces the superconductor/dielectric to less than 5 enhances structural properties a-Ge based on Raman spectroscopy. Additionally, resonators fabricated...