Hall effect in semiconducting epitaxial and amorphous Y-Ba-Cu-O thin films

Abstract

An experimental study of the Hall effect in nonmetallic Y-Ba-Cu-O thin films is reported. Both epitaxial crystalline YBa 2 Cu 3 O 6ϩx (xр0.5) and multiphase/amorphous Y-Ba-Cu-O thin films were studied. The structure of the samples was measured by x-ray diffraction and Raman microprobe. The amorphous Y-Ba-Cu-O samples were found to have a grain size of about 100 Å. The conduction properties were studied and analyzed for the two types of samples over a wide temperature range including room temperature. The Hall effect measurements showed positive charge carriers with a concentration ranging from 10 17 to 10 20 cm Ϫ3 at room temperature. The mobility was found to decrease with higher Hall carrier concentration. The empirical relationship for the mobility dependence on impurity concentration agreed with the relationship between mobility and the experimental Hall carrier concentration, suggesting that the same localized states were responsible for both providing the carriers and reducing the mobility through scattering. It was also observed that the mobility values for both amorphous and crystalline samples followed the same empirical curve, a result which showed that the conduction mechanisms in the epitaxial ͑tetragonal͒ and amorphous Y-Ba-Cu-O materials are very likely to be similar despite the differences in the composition and structure of the films. The similarity is consistent with other work that concludes that the conduction mechanism occurs along the copper oxide planes. Our work implies that the conduction mechanism operates over a short range, less than the 100 Å grain size of the amorphous, such that the lack of order in the amorphous samples was essentially irrelevant to the charge transport.

MgO sacrificial layer for micromachining uncooled Y-Ba-Cu-O IR microbolometers on Si/sub 3/N/sub 4/ bridges

“…The deposition rate decreased with the added oxygen, implying that the sputtering target was chemically altered and the resulting film contained more oxygen. As the oxygen content in YBCO increases, the Fermi level gets closer to the mobility edge for carriers (holes), decreasing the activation energy for conduction and therefore the TCR [38], [39].…”

Pyroelectric effect in Y–Ba–Cu–O thin films under laser illumination

“…The grain size in the YBCO thin films is estimated to be less than 10 nm from the x-ray diffraction data by using Scherr's Formula, 20 indicating the absence of long range structural order. 21,22 To allow for the propagation of high frequency electrical signals, silver ͑Ag͒ microstrips were fabricated on top of the YBCO, with a 20-m-wide gap to allow for the optical illumination of the YBCO film. The Ag microstrips were fabricated to be 100 m wide and 300 nm thick by thermal evaporation at room temperature and lift-off patterning.…”