Phononic structures and related devices and methods
Phononic structures, devices related to phononic structures, and methods related to fabrication of the phononic structures are described. The phononic structure can include a sheet of material, where the sheet of material can include a plurality of regions. Adjacent regions in the sheet of material can have dissimilar phononic patterns.
1. A phononic structure, comprising:
a sheet of a first material, the sheet comprising a plurality of regions, wherein adjacent regions have dissimilar phononic patterns and are configured to carry a heat flow along the longitudinal axis of the phononic structure,
wherein:
each region has a length perpendicularly to the longitudinal axis of the phononic structure, the length being more than twice a phonon mean free path of the first material, and
the plurality of regions comprises at least a first region and a second region adjacent the first region, the first region comprising a period pattern of holes in the first material and the second region comprising the first material devoid of holes.
2. The phononic structure according to claim 1 , wherein the adjacent regions have dissimilar phonon energy band structures.
3. The phononic structure according to claim 1 , wherein the holes are filled with a second material.
4. The phononic structure according to claim 3 , wherein the second material is selected from the group consisting of thermal insulators, polymers, glasses, ceramics, aerogels, natural materials, and epoxies.
5. The phononic structure according to claim 1 , wherein distance between holes is not larger than twice a thickness of the sheet of the first material.
6. The phononic structure according to claim 1 , wherein distance between holes is not larger than twice the phonon mean free path of the first material.
7. The phononic structure according to claim 1 , wherein the first material is selected from the group consisting of silicon, graphene, germanium, silicon-germanium, and lead-telluride.
8. A phononic structure comprising:
a sheet of a first material, the sheet comprising a plurality of regions, wherein adjacent regions have dissimilar phononic patterns and are configured to carry a heat flow along a longitudinal axis of the phononic structure, and each region has a length perpendicularly to the longitudinal axis of the phononic structure, the length being more than twice a phonon mean free path of the first material,
wherein:
the plurality of regions comprises a first set of regions and a second set of regions, the first set of regions comprising a periodic pattern of holes in the first material,
regions in the first set of regions have a first phononic pattern,
regions in the second set of regions have a second phononic pattern dissimilar to the first phononic pattern,
the phononic structure alternates, along the longitudinal axis of the phononic structure, between a region from the first set of regions and a region from the second set of regions, and
the first set of regions comprises at least three regions and the second set of regions comprises at least three regions.
9. The phononic structure according to claim 1 , wherein the phononic structure has a lower thermal conductivity than the first material.
10. The phononic structure according to claim 1 , wherein the phononic structure has a lower thermal conductivity than the first material and the phononic structure has substantially the same electrical conductivity as the first material.
11. A thermoelectric device, comprising:
at least a first sheet and a second sheet of a semiconductor material, each of the first sheet and the second sheet comprising a first region and a second region adjacent the first region, wherein the first region and the second region have dissimilar phononic patterns and are configured to carry a heat flow along a longitudinal axis of the thermoelectric device;
a first electrode electrically coupled to a first side of the first sheet;
a second electrode electrically coupled to a first side of the second sheet; and
a third electrode electrically coupled to a second side of the first sheet and the second sheet,
wherein:
both the first and second regions have a length perpendicularly to the longitudinal axis of the thermoelectric device, the length being more than twice a phonon mean free path of the semiconductor material,
the first region comprises a period pattern of holes and the second region is devoid of holes, and
during operation of the thermoelectric device, the first and second sides of each sheet are adapted to exhibit different temperatures.