Massachusetts Institute of Technology

The Trustees of Boston College

University of California

Northeastern University

Mildred S Dresselhaus

Zhifeng Ren

Gang Paul Chen

Bed Poudel

Xiangzhong Sun

Takaaki Koga

Jackie Yi-Ru Ying

Yu-Ming Lin

Shankar Kumar

Akintunde Ibitayo Akinwande

Jing Kong

Lei Zhang

Theodore C Harman

Stephen B Cronin

Xiaoyuan Chen

Zhibo Zhang

Oded Rabin

Paul R Herz

Wenzhong Wang

Kang L Wang

Tomas Apostol Palacios

Yung Joon Jung

Swastik Kar

Michael P Walsh

Hyun Young Jung

Xiao Yan

Dezhi Wang

David L Spears

Bo Yu

Yucheng Lan

Qing Hao

Yuxuan Lin

Chi Won Ahn

Steven B Cronin

Paulo Antonio Trindade Araujo

Yi Ma

Xiaowei Wang

Joshi R Giri

Xi Ling

Alfonso Reina Cecco

Inter-allotropic transformations of carbon are provided using moderate conditions including alternating voltage pulses and modest temperature elevation. By controlling the pulse magnitude, small-diameter single-walled carbon nanotubes are transformed into larger-diameter single-walled carbon nanotubes, multi-walled carbon nanotubes of different morphologies, and multi-layered graphene nanoribbons.

Fabrication of carbon nanoribbons from carbon nanotube arrays

A two-dimensional heterostructure is synthesized by producing a patterned first two-dimensional material on a growth substrate. The first two-dimensional material is patterned to define at least one void through which an exposed region of the growth substrate is exposed. Seed molecules are selectively deposited either on the exposed region of the growth substrate or on the patterned first two-dimensional material. A second two-dimensional material that is distinct from the first two-dimensional material is then grown from the deposited seed molecules.

Universal methodology to synthesize diverse two-dimensional heterostructures

The present invention is generally directed to nanocomposite thermoelectric materials that exhibit enhanced thermoelectric properties. The nanocomposite materials include two or more components, with at least one of the components forming nano-sized structures within the composite material. The components are chosen such that thermal conductivity of the composite is decreased without substantially diminishing the composite's electrical conductivity. Suitable component materials exhibit similar electronic band structures. For example, a band-edge gap between at least one of a conduction band or a valence band of one component material and a corresponding band of the other component material at interfaces between the components can be less than about 5kT, wherein kis the Boltzman constant and T is an average temperature of said nanocomposite composition.

Nanocomposites with high thermoelectric figures of merit

Thermoelectric materials with high figures of merit, ZT values, are disclosed. In many instances, such materials include nano-sized domains (e.g., nanocrystalline), which are hypothesized to help increase the ZT value of the material (e.g., by increasing phonon scattering due to interfaces at grain boundaries or grain/inclusion boundaries). The ZT value of such materials can be greater than about 1, 1.2, 1.4, 1.5, 1.8, 2 and even higher. Such materials can be manufactured from a thermoelectric starting material by generating nanoparticles therefrom, or mechanically alloyed nanoparticles from elements which can be subsequently consolidated (e.g., via direct current induced hot press) into a new bulk material. Non-limiting examples of starting materials include bismuth, lead, and/or silicon-based materials, which can be alloyed, elemental, and/or doped. Various compositions and methods relating to aspects of nanostructured thermoelectric materials (e.g., modulation doping) are further disclosed.

Methods for high figure-of-merit in nanostructured thermoelectric materials

A film of single-layer to few-layer graphene is formed by depositing a graphene film via chemical vapor deposition on a surface of a growth substrate. The surface on which the graphene is deposited can be a polycrystalline nickel film, which is deposited by evaporation on a SiO/Si substrate. A protective support layer is then coated on the graphene film to provide support for the graphene film and to maintain its integrity when it is removed from the growth substrate. The surface of the growth substrate is then etched to release the graphene film and the protective support layer from the growth substrate, wherein the protective support layer maintains the integrity of the graphene film during and after its release from the growth substrate. After being released from the growth substrate, the graphene film and protective support layer can be applied onto an arbitrary target substrate for evaluation or use in any of a wide variety of applications.

Large-area single- and few-layer graphene on arbitrary substrates

Systems and methods utilizing solar-electrical generators are discussed. Solar-electrical generators are disclosed having a radiation-capture structure and one or more thermoelectric converters. Heat produced in a capture structure via impingement of solar radiation can maintain a portion of a thermoelectric converter at a high temperature, while the use of a low temperature at another portion allows electricity generation. Thus, unlike photovoltaic cells which are generally primarily concerned with optical radiation management, solar thermoelectrics converters are generally concerned with a variety of mechanisms for heat management. Generators can include any number of features including selective radiation surfaces, low emissivity surfaces, flat panel configurations, evacuated environments, and other concepts that can act to provide thermal concentration. Designs utilizing one or more optical concentrators are also disclosed.

Solar thermoelectric conversion

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 present invention generally relates to binary or higher order semiconductor nanoparticles doped with a metallic element, and thermoelectric compositions incorporating such nanoparticles. In one aspect, the present invention provides a thermoelectric composition comprising a plurality of nanoparticles each of which includes an alloy matrix formed of a Group IV element and Group VI element and a metallic dopant distributed within the matrix.

Metal-doped semiconductor nanoparticles and methods of synthesis thereof

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.

The present invention provides methods for synthesis of IV&#x2013;VI nanostructures, and thermoelectric compositions formed of such structures. In one aspect, the method includes forming a solution of a Group IV reagent, a Group VI reagent and a surfactant. A reducing agent can be added to the solution, and the resultant solution can be maintained at an elevated temperature, e.g., in a range of about 20&#xb0; C. to about 360&#xb0; C., for a duration sufficient for generating nanoparticles as binary alloys of the IV&#x2013;VI elements.

Methods for synthesis of semiconductor nanocrystals and thermoelectric compositions

A carrier pocket engineering technique used to provide superlattice structures having relatively high values of the three-dimensional thermoelectric figure of merit (Z T) is described. Also described are several superlattice systems provided in acordance with the carrier pocket engineering technique. Superlattice structures designed in accordance with this technique include a plurality of alternating layers of at least two different semiconductor materials. First ones of the layers correspond to barrier layers and second ones of the layers correspond to well layers but barrier layers can also work as well layers for some certain carrier pockets and vice-versa. Each of the well layers are provided having quantum well states formed from carrier pockets at various high symmetry points in the Brillouin zone of the structure to provide the superlattice having a relatively high three-dimensional thermoelectric figure of merit.

Superlattice structures having selected carrier pockets and related methods

A superlattice structure for thermoelectric power generation includes m monolayers of a first barrier material alternating with n monolayers of a second quantum well material with a pair of monolayers defining a superlattice period and each of the materials having a relatively smooth interface therebetween. Each of the quantum well layers have a thickness which is less than the thickness of the barrier layer by an amount which causes substantial confinement of conduction carriers to the quantum well layer and the alternating layers provide a superlattice structure having a figure of merit which increases with increasing temperature.

Superlattice structures for use in thermoelectric devices

An array of nanowires having a relatively constant diameter and techniques and apparatus for fabrication thereof are described. In one embodiment, a technique for melting a material under vacuum and followed by pressure injection of the molten material into the pores of a porous substrate produces continuous nanowires. In another embodiment, a technique to systematically change the channel diameter and channel packing density of an anodic alumina substrate includes the steps of anodizing an aluminum substrate with an electrolyte to provide an anodic aluminum oxide film having a pore with a wall surface composition which is different than aluminum oxide and etching the pore wall surface with an acid to affect at least one of the surface properties of the pore wall and the pore wall composition.

Nanowire arrays

Growing community of inventors

Arlington, MA, United States of America

Mildred S Dresselhaus