Massachusetts Institute of Technology

Paul R Herz

Yu-Ming Lin

Akintunde Ibitayo Akinwande

Mildred S Dresselhaus

Oded Rabin

The presently disclosed invention provides for the fabrication of porous anodic alumina (PAA) films on a wide variety of substrates. The substrate comprises a wafer layer and may further include an adhesion layer deposited on the wafer layer. An anodic alumina template is formed on the substrate. When a rigid substrate such as Si is used, the resulting anodic alumina film is more tractable, easily grown on extensive areas in a uniform manner, and manipulated without danger of cracking. The substrate can be manipulated to obtain free-standing alumina templates of high optical quality and substantially flat surfaces. PAA films can also be grown this way on patterned and non-planar surfaces. Furthermore, under certain conditions, the resulting PAA is missing the barrier layer (partially or completely) and the bottom of the pores can be readily accessed electrically. The resultant film can be used as a template for forming an array of nanowires wherein the nanowires are deposited electrochemically into the pores of the template. By patterning the electrically conducting adhesion layer, pores in different areas of the template can be addressed independently, and can be filled electrochemically by different materials. Single-stage and multi-stage nanowire-based thermoelectric devices, consisting of both n-type and p-type nanowires, can be assembled on a silicon substrate by this method.

Thick porous anodic alumina films and nanowire arrays grown on a solid substrate

The presently disclosed invention provides for the fabrication of porous anodic alumina (PAA) films on a wide variety of substrates. The substrate comprises a wafer layer and may further include an adhesion layer deposited on the wafer layer. An anodic alumina template is formed on the substrate. When a rigid substrate such as Si is used, the resulting anodic alumina film is more tractable, easily grown on extensive areas in a uniform manner, and manipulated without danger of cracking. The substrate can be manipulated to obtain free-standing alumina templates of high optical quality and substantially flat surfaces PAA films can also be grown this way on patterned and non-planar surfaces. Furthermore, under certain conditions the resulting PAA is missing the barrier layer (partially or completely) and the bottom of the pores can be readily accessed electrically. The resultant film can be used as a template for forming an array of nanowires wherein the nanowires are deposited electrochemically into the pores of the template. By patterning the electrically conducting adhesion layer, pores in different areas of the template can be addressed independently, and can be filled electrochemically by different materials. Single-stage and multi-stage nanowire-based thermoelectric devices, consisting of both n-type and p-type nanowires, can be assembled on a silicon substrate by this method.

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Paul R Herz