High‐quality Cu(In,Ga)Se2 (CIGS) films are deposited from hydrazine‐based solutions and are employed as absorber layers in thin‐film photovoltaic devices. The CIGS films exhibit tunable stoichiometry and well‐formed grain structure without requiring post‐deposition high‐temperature selenium treatment. Devices based on these films offer power conversion efficiencies of 10% (AM1.5 illumination).

We have used oxygen-plasma-assisted molecular-beam epitaxy (OPA-MBE) to grow CoxTi1−xO2 anatase on SrTiO3(001) for x=∼0.01–0.10, and have measured the structural, compositional, and magnetic properties of the resulting films. Whether epitaxial or polycrystalline, these CoxTi1−xO2 films are ferromagnetic semiconductors at and above room temperature. However, the magnetic and structural properties depend critically on the Co distribution, which varies widely with growth conditions. Co is substitutional in the anatase lattice and in the +2 formal oxidation state in ferromagnetic CoxTi1−xO2. The magnetic properties of OPA-MBE grown material are significantly better than those of analogous pulsed laser deposition-grown material.

The origin of spin–orbit torques, which are generated by the conversion of charge-to-spin currents in non-magnetic materials, is of considerable debate. One of the most interesting materials is tungsten, for which large spin–orbit torques have been found in thin films that are stabilized in the A15 (β-phase) structure. Here we report large spin Hall angles of up to approximately –0.5 by incorporating oxygen into tungsten. While the incorporation of oxygen into the tungsten films leads to significant changes in their microstructure and electrical resistivity, the large spin Hall angles measured are found to be remarkably insensitive to the oxygen-doping level (12–44%). The invariance of the spin Hall angle for higher oxygen concentrations with the bulk properties of the films suggests that the spin–orbit torques in this system may originate dominantly from the interface rather than from the interior of the films.

Thin-film CuIn(Se,S)2 (i.e., CIS) absorbers have been solution-deposited using a hydrazine-based approach that offers the potential to significantly lower the fabrication cost for CIS solar cells. In this method, metal chalcogenides are completely dissolved in hydrazine, forming a homogeneous precursor solution. Film deposition is demonstrated by spin-coating of the precursor solution onto various substrates, including Mo-coated glass and thermally oxidized silicon wafers. Using this approach, no postdeposition anneal in a toxic Se or S-containing environment is needed to obtain CIS films. Instead, only a simple heat-treatment in an inert atmosphere is required, resulting in CIS films with good crystallinity. Bandgap tuning can readily be achieved by varying the amount of S incorporated into the film. Complete CIS devices with glass/Mo/CIS/CdS/i-ZnO/ITO structure are fabricated using absorbers produced via this hydrazine-based approach. Air Mass 1.5G power conversion efficiencies of as high as 12.2% have been achieved, demonstrating that this new approach has great potential as a low-cost alternative for high-efficiency CIS solar cell production.

The crystallization behavior of ultrathin phase change films was studied using time-resolved x-ray diffraction (XRD). Thin films of variable thickness between 1 and 50nm of the phase change materials Ge2Sb2Te5 (GST), N-doped GST, Ge15Sb85, Sb2Te, and Ag- and In-doped Sb2Te were heated in a He atmosphere, and the intensity of the diffracted x-ray peaks was recorded. It was found for all materials that the crystallization temperature increases as the film thickness is reduced below 10nm. The increase depends on the material and can be as high as 200°C for the thinnest films. The thinnest films that show XRD peaks are 2nm for GST and N-GST, 1.5nm for Sb2Te and AgIn-Sb2Te, and 1.3nm for GeSb. This scaling behavior is very promising for the application of phase change materials to solid-state memory technology.

Magnetic media using materials with high uniaxial magneto-crystalline anisotropy, KU, combined with a thermal assist to overcome write field limitations have been proposed as one of the potential technologies to extend the areal density of magnetic disk recording beyond the limitations of current technology. Here we present an investigation on structural and temperature dependent magnetic properties of chemically ordered epitaxial Fe55−xNixPt45 thin films. Increasing Ni additions result in a steady reduction of magneto-crystalline anisotropy, saturation magnetization, and Curie temperature. The ability to control thermomagnetic properties over a wide range makes Fe55−xNixPt45 and similar FePt-based pseudo-binary alloys attractive base materials for media applications in thermally assisted magnetic recording.

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Copper ternary chalcogenide compounds and alloys are among the most promising absorber materials for solar cell application and polycrystalline Cu(In,Ga)Se 2 (CIGS) thin films, because of their direct and tunable energy band gaps, high optical absorption coefficients in the visible to near-IR spectral range, high tolerance to defects and impurities, and demonstrated power conversion efficiency approaching 20%, 1 have been the focus of extensive investigation for over two decades. 2-6 A conventional CIGS-based solar cell device consists of a substrate, a molybdenum back contact, a p-type CIGS absorber layer, a thin n-type buffer layer (typically CdS), a bilayer of intrinsic and aluminum-doped zinc oxide or ITO as a transparent conductive oxide front contact, and finally a metal grid to help collect the current generated by the cell. The CIGS absorber layer, often viewed as the most critical and complex layer of the solar cell device, contains four or more elements (usually doped with sodium and/or sulfur) while accommodating a wide range of variation in chemical composition (such as Ga content, Cu/(In þ Ga) ratio, and S content). Besides the detailed CIGS chemical composition, several other crucial parameters, including film thickness and grain structure, need to be optimized for high cell efficiency. Because grain boundaries may act as recombination centers for photogenerated charge carriers, thereby degrading device performance, it is desirable to have grain sizes on the order of the film thickness (micrometer-length scale) so as to minimize such recombination effects.The current study demonstrates significant grain size and device performance improvement through the intentional introduction of controlled Sb impurity-doping (ranging between 0.2 to 1.0 mol % relative to moles of CIGS) into the CIGS layer during film processing. Although the approach may be more generally applicable, we here use a solution-based spin-coating process developed in our lab 7-10 as a representative deposition method to demonstrate the effect of antimony-doping on the properties of the CIGS film and the corresponding solar cell device built upon it. Our approach relies on forming a soluble molecular-based metal chalcogenide precursor in hydrazine at room temperature, and device-quality CIGS films are readily attainable using this process, without the need for postdeposition selenization. [8][9][10] Similar experimental procedures to those described in our previous reports 9,10 were followed for solution preparation, film deposition, device fabrication, and measurement. An additional Sb 2 S 3 /S solution in hydrazine was used as Sb source for each film described (no intentionally added Na).CIGS films targeting a CuIn 0.7 Ga 0.3 Se 2 stoichiometry with increasing Sb content (from Sb = 0 to Sb = 1.0 mol % in 0.25 mol % increments) were deposited onto Mo-coated glass substrates and annealed at 400°C for 20 min to form the final crystalline forms. 14 The phase purity of the films was verified with X-ray diffraction, and no systematic peak p...