Surface damage on silicon substrates caused by RSE has been investigated. Defects are classified into four categories in order of destruction, namely, precipitates surrounded by elastic strain field, surface roughness pattern, polycrystalline and amorphous silicon, and no defects, based on the results of TEM and RHEED observation. In particular, precipitates which reach a depth more than 500 Å were found to cause OSF. The surface damage consists of contamination (C, F, O) layer, C and defect mixed layer, and defect layer in order from the top. The degree of these defects and contaminations expand with increasing power density and etching duration. RSE conditions, where no defects are formed, were determined, e.g., within 1 minute at 0.4 W cm-2.
the normal state which has been proposed by theoreticians. We have succeeded in detecting the coherent Bose species in the normal state of YBa 2 Cu 3 O y . The idea ͓L. P. Levy, G. Dolan, J. Dunsmuir, and H. Bouchiat, Phys. Rev. Lett. 64, 2074 ͑1990͔͒ of having the detected oscillation of a fermion persisting current caused by the Aharanov-Bohm effect on magnetic field scanning in the assemblage of the mesoscopic rings of metal was employed in the assemblage of a ring patterned in the YB 2 Cu 3 O y film. The sensitivity of our detection system is not high enough to detect fermions, but it is high enough for detecting coherent bosons if they exist. Oscillations with flux periods corresponding to h/2e have been found at TϾTc, even at temperatures 30 K or more above T c inserted in the patterned YBa 2 Cu 3 O y film, but have not been found in the patterned Au or Pd films. To explain the coherent current circulating in a ring with a circumference as long as 40 m, presumably in the prestage to the superconducting stage, the possible coexistence of a minority of coherent bosons and a majority of incoherent bosons is discussed. The detection of minority coherent bosons in the background of a majority of incoherent species is possible in this method.
Epitaxial growth of CeO2 films on Al2O3 (11̄02) substrates and the effect of CeO2 buffer layers on the growth orientation and superconducting properties of EuBa2Cu3O7-δ (EBCO) were investigated. CeO2 and EBCO films were prepared by rf and dc magnetron sputtering, respectively, and were characterized by X-ray diffraction (θ-2θ scan and ϕ scan), atomic force microscopy (AFM) and high resolution scanning electron microscopy. Epitaxial (001) CeO2 films were obtained at an off-center distance (D
on-off) of 3.5 cm and a substrate temperature of 660°C. The structural and superconducting properties of EBCO films deposited at 650°C depended on the thickness of the CeO2 buffer layer. The EBCO films deposited on CeO2 50-400-Å-thick buffer layers had T
ce's of 90 K or above. The high-T
c EBCO films had in-plane epitaxial orientation relationships of Al2O3 [112̄0]\varparallelCeO2 [100]\varparallelEBCO[110]. The EBCO films on the thin CeO2 buffer layers had rectangular grains similar to those on MgO(001) substrates. The critical current density of the EBCO films with T
ce=90 K was about 6 ×105 A/cm2 in zero field at 77.3 K. The T
ce varied largely and decreased with increasing CeO2 buffer layer thickness above 500 Å. AFM observation of a 1000-Å-thick CeO2 film showed growth of bamboo-like crystal grains 1700 Å long and 300 Å wide along the direction of CeO2 [110]. The ravine depths were about 100 Å. The EBCO films on the thick CeO2 buffer layer (>500 Å) exhibited poor superconducting behavior and gave (103) or (110) diffraction peaks.
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