| 摘要 |
<p>Josephson junction devices have been made using crystalline silicon as the barrier layer in order to obtain large critical current densities and low device capacitance. However, this has involved thinning a silicon crystal wafer to barrier thickness and forming the layers of superconductor and insulator on both sides. This is a complex and difficult process, and even when successful leads to an extremely fragile device. …<??>The present invention turns on the use of certain compounds, in particular niobium nitride, which are superconductive, refractory, and do not react with hydrogen or with silicon or germanium at temperatures at which these semiconductors can be deposited from the vapour phase. …<??>A device according to the invention comprises a first superconductive layer (10) preferably of niobium nitride, a barrier layer (12) of silicon or germanium or an alloy of these, and a second superconductive layer (11) which may also be of niobium nitride. Because of the properties of the niobium nitride, the semiconductor may be deposited from the vapour phase by well known methods, either at an elevated temperature so that it is deposited in polycrystalline form, or at room temperature as an amorphous layer which is subsequently annealed at a higher temperature to cause it to re-crystallise. …<??>Other compound refractory superconductive materials such as niobium-tin and niobium-germanium may be utilised as an alternative to niobium nitride.</p> |
