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Synchrotron X-ray absorption near edge structure (XANES) measurements of F K-edge in conjunction with first-principles calculations are used to identify the local structure of the fluorine (F) atom in F-doped ZnO. The ZnO film was grown by pulsed laser deposition with an Nd:YAG laser, and an oxyfluoridation method was used to introduce F ions into the ZnO films. The measured XANES spectrum of the sample was compared against the first-principles XANES calculations based on various models for local atomic structures surrounding F atoms. The observed spectral features are attributed to ZnF2 and FO defects in wurtzite bulk ZnO.

We have studied the effects of fluorine inclusion on the electrical transport characteristics and interface structure of the hafnium oxide barrier in a magnetic tunnel junction. The tunneling magnetoresistance (TMR) and resistance-area (RA) as a function of oxidation time show that the TMR ratio of the hafnium oxyfluoride barrier is higher (8.3%) than that of the hafnium oxide barrier (5.7%) at their optimum conditions, and the oxyfluoride barrier junctions maintain a high TMR ratio even when the RA product increases by three orders of magnitude. X-ray photoelectron spectroscopy analysis shows that the fluorine atoms in the oxyfluoride barrier play an important role in the formation of a barrier with uniform composition. We believe that the initial fluoride layer is causing the subsequent oxygen diffusion to slow down, resulting in the formation of a defect-free hafnium oxide layer. These results are consistent with what we have found for aluminum oxyfluoride barriers.

The electrical characteristics and the interface structure of magnetic tunnel junctions with aluminum oxyfluoride barrier were studied. Compared to conventional junctions with aluminum oxide tunnel barrier, junctions with aluminum oxyfluoride barrier exhibit larger and nearly constant tunneling magnetoresistance (TMR) values over a wide range of junction resistance and show a smaller bias dependence of TMR, a smaller temperature dependence of junction resistance, and higher effective barrier height. The cross sectional TEM image demonstrates that the junction with oxyfluoride barrier has excellent barrier flatness and smooth interfaces. X-ray photoelectron spectroscopy indicates that the fluorine forms an aluminum oxyfluoride barrier together with oxygen and that the growth of fluorine-rich oxyfluoride layer near the top surface of the barrier plays an important role in the formation of the highly insulating barrier, resulting in nearly ideal barrier/electrode interfaces without a detrimental magnetically dead layer.

SrVO3 films were grown by laser molecular beam epitaxy on LaAlO3 substrates. For a 10-nm-thick film, its resistivity could be reduced by a factor of 4 by inserting a single La–O atomic layer on an oxygen-annealed LaAlO3 substrate. X-ray diffraction and x-ray photoelectron spectroscopy measurements revealed that oxygen defect concentrations could be varied significantly by controlling the substrate terminations, i.e., interface chemistry. It was suggested that the interface chemistry could influence formation of extended defects and result in changes in electrical properties.

The design of high‐Tc superconducting bolometers for applications such as infrared imaging arrays is discussed. The dependence of bolometer sensitivity on excess voltage noise in the thermometer is a function of the detector area and thus of the wavelength to be detected. Measurements of the voltage noise in thin films of YBa2Cu3O7−δ on Si, Si3N4, and sapphire substrates are used to predict the performance of different bolometer architectures. Useful opportunities exist for bolometers made on both Si and Si3N4 membranes. A readout scheme for two‐dimensional arrays of bolometers is also described in which real‐time signal integration is performed on the chip.

Two types of sensitive high‐Tc bolometer have been fabricated on 20‐μm‐thick sapphire substrates with YBa2Cu3O7−δ thin film transition edge thermometers. The sensitivity of both devices is superior to commercially available, room temperature pyroelectric detectors. A 1×1 mm bolometer with a radiation absorber of gold black smoke has a noise equivalent power NEP=2.4×10−11 W/Hz1/2 at 10 Hz and has useful sensitivity over wavelengths 20–100 μm. A 3×3 mm bolometer with a Bi film radiation absorber has NEP=3.6×10−10 W/Hz1/2 at 10 Hz and has useful sensitivity over wavelengths 100–300 μm. Water vapor transmittance spectra were measured to demonstrate the sensitivity of both devices.

Raman spectra of YBa2 Cu3 O7 excited by different lines of Ar and Kr lasers have been studied. It was found that significant changes in relative intensity of phonon lines occurred in the spectra when the excitation frequency was shifted from the red into the blue region of the spectrum. The enhancement of high‐frequency phonons, which involves stretching of CuO bonds, was attributed to resonance with an interband transition in YBa2 Cu3 O7 .