J. Hautala

Absorption at radio frequencies in superconducting Y1Ba2Cu3Oy

The large magnetic‐field‐dependent ac absorption in superconducting Y1 Ba2 Cu3 Oy ceramics and powders decreases slowly with increasing frequency in the range 2–16 MHz. The magnetic‐field‐dependent ac absorption is observed below Tc in superconducting Y1 Ba2 Cu3 Oy ceramics, powders and twinned crystals and in (La,Sr)2 CuO4 and BaPb0.75 Bi 0.25 CuO3 powders and appears to contain distinct contributions from trapped flux and/or intragrain tunnel junctions and from ordinary superconductor surface impedance. The contribution from trapped flux and/or intragrain tunnel junctions is important in dc magnetic fields of up to approximately 20 G at all temperatures below Tc. There is an identifiable modulated ac absorption which changes slowly over more than 12 kG at low temperatures and which we propose is primarily caused by the ac surface impedance with possible contributions from the critical state. A twinned crystal of Y1 Ba2 Cu3 Oy exhibits the same ac absorption except that it has an anisotropic dependence o...The large magnetic-field-dependent ac absorption in superconducting Y/sub 1/ Ba/sub 2/ Cu/sub 3/ O/sub /ital y// ceramics and powders decreases slowly with increasing frequency in the range 2--16 MHz. The magnetic-field-dependent ac absorption is observed below /ital T//sub /ital c// in superconducting Y/sub 1/ Ba/sub 2/ Cu/sub 3/ O/sub /ital y// ceramics, powders and twinned crystals and in (La,Sr)/sub 2/ CuO/sub 4/ and BaPb/sub 0.75/ Bi /sub 0.25/ CuO/sub 3/ powders and appears to contain distinct contributions from trapped flux and/or intragrain tunnel junctions and from ordinary superconductor surface impedance. The contribution from trapped flux and/or intragrain tunnel junctions is important in dc magnetic fields of up to approximately 20 G at all temperatures below /ital T//sub /ital c//. There is an identifiable modulated ac absorption which changes slowly over more than 12 kG at low temperatures and which we propose is primarily caused by the ac surface impedance with possible contributions from the critical state. A twinned crystal of Y/sub 1/ Ba/sub 2/ Cu/sub 3/ O/sub /ital y// exhibits the same ac absorption except that it has an anisotropic dependence on the applied dc magnetic field.

n‐type doping of amorphous silicon using tertiarybutylphosphine

The use of a liquid organic source for n‐type doping in hydrogenated amorphous silicon (a‐Si:H) is described. Tertiarybutylphosphine (TBP) vapor is added to silane in a rf glow discharge process to produce doped a‐Si:H thin films. Impurity levels from parts per million to about 1% phosphorus have been incorporated into the film with this method. Measurements of dark conductivity, photoconductivity, conductivity activation energy, electron spin resonance, and sub‐gap optical absorption of the TBP‐doped films are compared to those published for films doped with phosphine.

Absorption of microwaves in superconducting YBa 2 Cu 3 O 7 and field-cooling effects

Measurements of magnetic-field-dependent microwave absorption as a function of both the temperature (4 K to Tc) and cooling field (0–10 kG) are reported. Below a certain characteristic temperature, T* < Tc, the absorption strongly depends on the magnetic field in which the samples are cooled. The characteristic temperature T* scales with Tc.

Microwave-induced voltage in superconducting YBaCuO

Abstract Dc voltage is induced across bulk samples of YBa 2 Cu 3 O 7 exposed to microwave radiation. This voltage is a function of sample temperature and microwave power level with a strong dependence on the external magnetic field, the maximum being at zero field. This is attributed to Josephson junctions in the material.