CVD Nanocrystalline Silicon as Thermoelectric Material

摘要

A process for forming a doped nc-Si thin film thermoelectric material. A nc-Si thin film is slowly deposited on a substrate, either by hot-wire CVD (HWCVD) with a controlled H2:SiH4 ratio R=6-10 or by plasma-enhanced (PECVD) with a controlled R=80-100, followed by ion implantation of an n- or p-type dopant and a final annealing step to activate the implanted dopants and to remove amorphous regions. A doped nc-Si thin film thermoelectric material so formed has both a controllable grain size of from a few tens of nm to 3 nm and a controllable dopant distribution and thus can be configured to provide a thermoelectric material having predetermined desired thermal and/or electrical properties. A final annealing step is used to activate the dopants and remove any residual amorphous regions.

主权项

1. A process for forming a germanium-free doped nanocrystalline silicon (nc-Si) thermoelectric material having a high electrical conductivity and a low thermal conductivity, comprising the steps of:
(1) providing a deposition mixture comprising H2 and SiH4 having a controlled H2:SiH4 ratio R of between 6 and 10, the deposition mixture being free of any added germanium; (2) controllably depositing the deposition mixture on a substrate by means of hot-wire chemical vapor deposition (HWCVD) at a growth rate of about 1-5 nm/s to form an nc-Si thin film material having a controlled grain size of about 15 nm to about 9 nm and a predetermined thermal conductivity κ, wherein the grain size is controlled by controlling the H2:SiH4 ratio R of the deposition mixture; (3) controllably doping the nc-Si thin film material by implanting dopant ions into the material to a concentration of about 1021 cm−3 to form a doped nc-Si thin film material having a controlled dopant profile and controlled electrical conductivity; and (4) annealing the doped nc-Si thin film material by first subjecting the material to a furnace annealing at a temperature between about 600 and about 800° C. for at least about 2 hours and then subjecting the material to a cycle of rapid thermal annealing at a temperature of about 800 to about 1000° C. for at least 1 minute.