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Selective area irradiation was used to create irradiated/unmodifïed/irradiated CDW heterostructures with well-defined interfaces on a single NbSe3crystal. The temperature dependence of the extra voltage required for carrier conversion (phase slip voltage, Vps0) is extracted from length dependent studies. We find that the temperature dependence of Vps0for the 143 K and 59 K CDW transitions are identical if properly scaled by the transition temperature. The Vps0temperature dependence is not thermally activated, but contains an upper and lower temperature branch. The crossover temperature for the two branches is 0.75TP. For the 59 K CDW we observe a zero-bias resistance anomaly near a single irradiated/unmodified interface. This anomaly abruptly changes with temperature near 44 K suggesting a qualitative change in the phase slip mechanism near 0.75TP.

Perovskite Ba 0.6 Sr 0.4 TiO 3 thin films were epitaxially grown on (001) LaAlO 3 and (001) MgO by using pulsed laser ablation. The films are single crystal cubic structure with interface relationship of (001) BST // (001) MgO and <100> BST // <100> MgO for the films on (001) MgO and (001) BST // (001) LAO and <100> BST // <100> LAO . High-resolution transmission electron microscopy studies indicated that the initially grown layer of the film on both (001) MgO and (001) LAO is TiO 2 monolayer. Equally spaced misfit dislocations were found to form at the interface to release the lattice mismatch energy. Physical property measurements show that the films exhibit excellent room temperature dielectric behavior with very low dielectric loss of 0.007 and very large tenability of 45% at 1 MHz. The figure of merit of 60°/dB has been achieved for the microwave phase shifter operated at 24 GHz and room temperature.

Antimony is known to be a donor in silicon, Low-energy implantations of Sb in Si produce very shallow profiles which have many device applications. Gibbons et al.1 calulated the projected ranges of Sb ion-implanted in Si, using the LSS (Lindhard, Scharff, and Schiott) method. Oetzmann et al.2 measured projected ranges and range straggling for several heavy ions in Si, Al, and Ge, using high-resolution backscattering; in the energy region of interest to us, e = 10-2 to 10-1, their results were about 30% higher than those reported by Gibbons et al. In the study reported here, we implanted 5 × 1014 Sb/cm2 in Si at 5-60 keV, measured the resulting depth distribution by secondary ion mass spectrometry, and checked the measurements by backscattering. Our results showed the experimental projected ranges to be about halfway between those reported in the earlier studies. The discrepancies between theoretical calculations and experimental results are due not to the electronic stopping cross section, which is negligible in the range of interest here, but to the nuclear stopping power. Using a modified nuclear scattering potential given by Wilson et al.,3 we calculated the projected range distribution according to the method described by Winterbon.4 Our results are in very good agreement with the experimental measurements.

In the study of ion implantation, electrically active ions or noble gas ions are often used for damage study, range profiling, etc. Very seldom are both electrically active ions and noble gas ions implanted at about the same depth. In the work reported here, argon and arsenic ion implants and their interference in diffusion were studied by using backscattering, electrical measurements, and transmission electron microscopy (TEM). Several unexpected phenomena were observed.First, when both Ar and As are implanted in high doses (about 1016/cm2), at depths around a few hundred nanometers, the Ar significantly hampers the As diffusion, and the As prevents the outdiffusion of the Ar. The interference occurs regardless of which ion is implanted first.Second, when Si wafers uniformly doped with about 4 × 1019 As/cm3 are ion-implanted with log16 Ar/cm2 at 130 keV, the As atoms stay uniformly distributed. When the sample is annealed at a temperature between 900 and 1100°C in a nitrogen ambient, however, double peaks for both Ar and As are observed by backscattering. The nonuniform distribution of As after the heat treatment of the uniformly distributed As is puzzling.Finally, the As profile for an As capsule diffused on a silicon wafer is greatly altered when the wafer has been pre-implanted with Ar. Arsenic atoms tend to build up at the same depth as the Ar atoms.Several other observations concerning Ar and As are equally puzzling. This paper discusses the observations and some plausible explanations.

Channeling effect measurements using MeV 4He ions were used in the study of the anneal of implantation disorder in <111> Si. The Si was implanted at LN2 temperature with arsenic or boron to dose levels sufficient for the formation of amorphous layers. We found that the residual disorder depends upon the previous annealing procedures. Samples annealed directly at temperatures up to 950°C exhibited high levels of disorder. The measurements suggest that the disordered layers can contain regions misoriented at small angles to the original substrate. Samples with sequential anneals from 450 up to 950 in 100°C increments, were essentially damage free from channeling viewpoint. We suggest that this thermal history is responsible for of some of the conflicting viewpoints in the literature.

The transport critical current Jc was measured as a function of the angle between the current and the c axis in YBa2Cu3O7-δ (110) thin films. The temperature dependence of Jc along the [110] axis fits the vortex-glass model and, along the c axis, the Josephson tunnel junction model. We explain the anisotropy of Jc, which is one order of magnitude higher than that due to the intrinsic pinning in the magnetic field, by the difference between the planar growth-defect pinning and the weak superconducting-plane pinning.

A new tin(IV) hexafluoroisopropoxide complex and a related tin(II) compound were used as low-pressure chemical vapor deposition precursors to tin oxide thin films. The films were characterized by backscattering and elastic recoil spectrometries, Auger and UV−vis spectroscopies, and nuclear reaction analysis. Sn(OCH(CF3)2)4(HNMe2)2, a volatile solid (subl 70−75 °C at 0.06 Torr), was synthesized in high yield by reacting Sn(NMe2)4 with (CF3)2CHOH. A crystal structure determination shows that it has an octahedral structure with trans-amine ligands. Low-pressure chemical vapor deposition using Sn(OCH(CF3)2)4(HNMe2)2 and air as precursors gave fluorine-doped tin oxide films (O/Sn = 1.8−2.4; F/Sn = 0.005−0.026) at substrate temperatures of 200−450 °C. The films are highly transparent in the visible region (>85%) and have resistivities as low as 2.1 × 10^-3 Ω cm. In contrast to the results obtained for the tin(IV) precursor, the tin(II) compound Sn(OCH(CF3)2)2(HNMe2) in combination with air or water vapor gave nonconductive transparent films at substrate temperatures of 180−250 °C having composition SnO0.9-1.3F0.1-0.4. These film stoichiometries suggest that hydrolysis was the primary film-forming reaction and that the tin was not oxidized in the deposition process.

A series of high-quality La_2−xSr_xCuO₄ (LSCO) superconductor crystals in the under-doping region with x &equal; 0.063, 0.07, 0.09, 0.10, 0.111 and 0.125 have been successfully prepared by the travelling-solvent floating-zone (TSFZ) technique. The crystals are large and free of subgrains and foreign phases. The high crystal quality has been revealed by double-crystal x-ray rocking curves and Rutherford backscattering spectrometry combined with ion-beam channelling effect. We find that the evolutions of the superconducting transition width and volume fraction as a function of carrier concentration exhibit interesting anomalies in the vicinity of some &lquot;magic number&rquot; doping levels such as x &equal; 1/4² (&equal;0.0625) and 1/3² (&equal;0.111). We argue that these behaviours are of intrinsic electronic origin.