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We have explored the effects of ion beam irradiation on the electrical and structural properties of superconducting thin films of YBa2Cu3O7-δ. Damage created by nuclear energy loss processes degrades the superconducting transitions. In general, the onset temperatures do not vary significantly with ion fluence, but the transition widths broaden until the resistance no longer reaches zero. This behavior is strikingly similar to that observed in granular superconducting films where islands of superconductor are progressively decoupled from each other, destroying the phase coherence. Data from resistance measurements as well as from Rutherford Backscattering and channeling measurements suggest that ion bombardment is not changing the volume fraction of superconducting material substantially.

A modulation doped Al.35Ga.65As/GaAs single interface structure using Si delta doping setback from the two dimensional electron gas (2 DEG) by 700Å, was measured in van der Pauw geometry at 0.35K and showed an electron mobility of 1.17× 107 cm2 /V see at a carrier density of 2.2× 1011electrons/cm2. An Al.30Ga.70As/GaAs single quantum-well 250Å wide of similar structure with a 500Å setback yielded a 2 DEG mobility of 5.1× 106 cm2 /Vsec at 3.0×1011 electrons/cm2under similar measurement conditions. These mobilities exceed those previously published by more than a factor of two for the single interface structure, and by nearly an order of magnitude for the quantum-well. The samples were grown by solid source MBE in a Varian Gen II modified with He closed-cycle cryogenic vacuum pumping, and in other ways, to achieve a base pressure of 1.5× 10−12 torr, as measured on a extractor-type ionization gauge that is not subject to the usual x-ray limited reading.