Microtip-controlled nanostructure fabrication and multi-tipped field- emission tool for parallel-process nanostructure fabrication

摘要

Fabrication of crystalline or molecular nanostructures with dimensions lesshan or equal to 1000 Å on a substrate surface is achieved by the indirect and/or direct action of a highly-localized field- emission current, which causes atoms of molecular gases introduced into a vacuum chamber to deposit or etch at surface atomic sites that are fixed by the emission-tip location. The tip is shaped to maintain control of the emitting region and is typically about 10 Å above the structure. The tip position is stepped in a programmed sequence, with each step taken on detecting the current increase induced by an atomic deposition below the tip. Gas sequences or mixtures can also be programmed, and microstructures of typically 10.sup.2 -10.sup.8 atoms are thereby formed with exact control of the positions and types of atomic constituents. PPThe multi-tipped tool consists of a large array of field- emitting nanostructure probe tip extensions on the end of a metal probe. The probe is tapered to a long, narrow, flat end with typical dimensions of 1 cm×1 &mgr;m. The probe tip extensions typically extend approximately 100 Å beyond the probe surface and their ends are shaped to act as independent field-emission tips, each at an exact atomic location. The nanostructures are spaced in a prescribed, repeating pattern with typical spacings on the order of 400 Å. The probe voltage, current and position, as well as CVD or etching gas pressures, are sequentially adjusted to fabricate nanostructures on a nearby substrate, which is typically 10-30 Å below the termination points of the probe tip extensions.