Mold having nanometric features, method for realizing such a mold and corresponding use of it in a method for realizing an array of carbon nanotubes

A method for making a mold for forming an array of carbon nanotubes comprising:

• providing a substrate having an upper surface;
• thermally growing, on the upper surface, a first layer of thermal oxide;
• forming, on the first layer of thermal oxide, a layer of photosensitive material;
• forming, on the layer of photosensitive material, a pattern through lithography patterning;
• developing the layer of photosensitive material and etching the first thermal oxide layer to obtain a thermal oxide mask with a geometry corresponding to the pattern;
• selectively etching the upper surface of the substrate to obtain, beneath the mask, a first plurality of projections having sloping side walls;
• etching the first plurality of projections having sloping side walls using plasma etching;
• thermally growing, on the upper surface, a second oxide layer to further etch the first plurality of projections having sloping side walls;
• and
• selectively removing said second thermal oxide layer and said mask thus freeing said upper surface of said substrate obtaining a first plurality of projections thereon, each having an end with a pointed profile.

A method for making an array of horizontally arranged carbon nanotubes comprising:

• providing a mold comprising a first layer of a first material having a surface with at least one plurality of projections arranged according to a pattern, each projection having a free end portion with a pointed profile;
• providing a dispersion of carbon nanotubes having dimensions comparable to the projections;
• wetting the projections of the first plurality of projections in the dispersion so that the projections adhere to respective carbon nanotubes;
• depositing, using the mold, the carbon nanotubes on the substrate to obtain the horizontally arranged carbon nanotubes.

A method for making an array of vertically arranged carbon nanotubes comprising:

• providing a mold comprising a first layer of a first material having a surface having at least one first plurality of projections arranged according to a pattern, the projections being conductive and having free end portions with a substantially pointed profiles;
• providing a substrate having an upper surface oxidizable with a native oxide film;
• depositing, on the substrate, a layer of catalytic nanoparticles substantially covering at least a portion of the surface of the substrate;
• arranging, in a wet environment, the mold in a spaced relation with the surface portion covered by the layer of catalytic nanoparticles, to thereby form a water meniscus between each projection and an underlying respective nanoparticle;
• applying a voltage impulse between the projections and the surface portion, thereby generating at each meniscus an oxide layer on each respective nanoparticle to attach each respective nanoparticle to the substrate;
• selectively removing the portion of nanoparticles not attached to the surface portion of the substrate to obtaining a catalytic nanoparticle pattern corresponding to the pattern of the mold;
• etching the nanopaticles fixed on the substrate to partially remove from each nanoparticle the oxide layer;
• and
• growing carbon nanotubes from the catalytic nanoparticles of the nanoparticles pattern using chemical vapor deposition (CVD) to thereby obtain the array of vertically arranged carbon nanotubes.