Lateral Transport and Thermoelectric Performance of Silicon Nanowires

Samarelli, A., Mirza, M. M.A. , Ferre Llin, L., MacLaren, D. and Paul, D. (2014) Lateral Transport and Thermoelectric Performance of Silicon Nanowires. In: 12th European Conference on Thermoelectrics, Madrid, Spain, 24–26 Sep 2014,

Abstract

Thermoelectric materials convert thermal energy into electrical energy using the Seebeck effect. The thermodynamic conversion efficiency is related to the figure of merit ZT = α2σT/κ where α is the Seebeck coefficient, σ is the electrical conductivity, T is the temperature and κ is the thermal conduc¬tivity. Low dimensional structures allow enhancements to σ, α and κ including the potential to relax Wiedemann-Franz as first suggested by Dresselhaus [1] and initial experiments suggest nanowires can produce significant enhancements [2]. In this work, the nanowires were fabricated from SOI wafers with a top 55nm n-doped Si layer at using a Vistec VB6 electron beam lithography tool with HSQ resist, low-damage dry etching [3] and thermal oxida¬tion. Four-terminal suspended membrane Hall bar devices, were fabricated to allow accurate measurement of the thermoelectric properties. Integrated resistance thermometers and heaters were patterned at either end of arrays of one hundred nanowires of different widths before the substrate was removed using an isotropic SF6 etch. Figure 1 demonstrates a SEM image of one hundred ~20 nm wide Si nanowires after the substrate has been etched resulting in the wires being free standing on a SiO2 membrane and a TEM mage of the cross section of one of the nanowires. The variation of the electrical, the thermal conductivity and the Seebeck coefficient with doping density and nanowire physical dimension have been mapped. Initial study and development of vertical nanowire arrays for practical modules is shown together with routes for optimization of the integration process.

• Item Type: Conference Proceedings
• Status: Published
• Refereed: Yes
• Glasgow Author(s) Enlighten ID: Samarelli, Mr Antonio and Ferre Llin, Dr Lourdes and Mirza, Dr Muhammad M A and Paul, Professor Douglas and MacLaren, Professor Donald
• Authors: Samarelli, A., Mirza, M. M.A., Ferre Llin, L., MacLaren, D., and Paul, D.
• Subjects: Q Science > QC Physics
• College/School: College of Science and Engineering > School of Engineering > Electronics and Nanoscale Engineering; College of Science and Engineering > School of Physics and Astronomy