Normal–super-normal double tunneling junction fabricated in a split-gate wire
✍ Scribed by N. Aoki; T. Kikutani; A. Oki; H. Hori; S. Yamada
- Publisher
- Elsevier Science
- Year
- 1997
- Tongue
- English
- Weight
- 517 KB
- Volume
- 22
- Category
- Article
- ISSN
- 0749-6036
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✦ Synopsis
We fabricated a new class of quantum structure which has a buried superconductor dot between the split-gate wire using a new scanning tunneling microscope (STM) fabrication technique. In order to fabricate a buried dot at a desired surface position, we employed a scanning electron microscope (SEM)/STM combined system and performed a two-step fabrication process. In the first step, we used a tungsten (W) tip and placed it close to the surface between the split-gate. When a voltage pulse was applied, a small hole (80 nm deep and 150 nm in diameter at half-depth) was created by electric evaporation. Such a hole means that a pin-point deep etching for the two-dimensional electron gas (2DEG) plane can be located at a depth of 60 nm from the surface. In the second step, we changed the W tip to an indium (In) tip and placed it close to the bottom of the hole by observing the SEM image. By applying a voltage pulse, In was evaporated from the end of the tip, electrically or thermally, onto the hole structure. Such a structure is expected to form a normal (2DEG)-super (In dot)-normal (2DEG) double tunneling junction when the wire is properly squeezed at low temperature.