Surface matters: Huge reduction of heat conduction observed in flat silicon channels
The advent of nanotechnology, where the rules of classical physics gradually fail as the dimensions shrink, is challenging Fourier's theory of heat in several ways.
A paper published in ACS Nano and written by researchers from the Max Planck Institute for Polymer Research (Germany), the Catalan Institute of Nanoscience and Nanotechnology (ICN2, Spain) and the VTT Technical Research Centre of Finland (Finland) in the framework of the project MERGING (Membrane-based phonon engineering for energy harvesting) describes how the nanometer-scale topology and the chemical composition of the surface control the thermal conductivity of ultrathin silicon membranes.
The results show that the thermal conductivity of silicon membranes thinner than 10 nm is 25 times lower than that of bulk crystalline silicon and is controlled to a large extent by the structure and the chemical composition of their surface.
Combining state-of-the-art realistic atomistic modeling, sophisticated fabrication techniques, new measurement approaches and the latest parameter-free modeling, researchers unraveled the role of surface oxidation in determining the scattering of phonons (quantized lattice vibrations), which are the main heat carriers in silicon.
Both experiments and modeling showed that removing the native oxide improves the thermal conductivity of silicon nanostructures by almost a factor of two, while successive partial re-oxidation lowers it again.
Large-scale molecular dynamics simulations with up to 1,000,000 atoms allowed the researchers to quantify the relative contributions to the reduction of the thermal conductivity arising from the presence of native SiO2 and from the dimensionality reduction evaluated for a model with perfectly specular surfaces.
Silicon is the material of choice for almost all electronic-related applications, where characteristic dimensions below 10 nm have been reached, e.g. in the newest FET transistors, and heat dissipation control becomes essential for their optimum performance.
“The chemical nature of surfaces, therefore, emerges as a new key parameter for improving the performance of Si-based electronic and thermoelectric nanodevices”, says Dr. Davide Donadio. As a result, this work opens new possibilities for novel thermal experiments and designs directed to manipulate heat at the nanoscales.
http://www.mpip-mainz.mpg.de/Surface_matters_Donadio – Press release and original publication
http://www.mpip-mainz.mpg.de/theory_nanostructures – Information about Dr. Donadio and his research
http://www.mpip-mainz.mpg.de/home/en – Max Planck Institute for Polymer Research
All latest news from the category: Materials Sciences
Materials management deals with the research, development, manufacturing and processing of raw and industrial materials. Key aspects here are biological and medical issues, which play an increasingly important role in this field.
innovations-report offers in-depth articles related to the development and application of materials and the structure and properties of new materials.
Duke-NUS and NHCS scientists first in the world to regenerate diseased kidney
Blocking an immune-regulating protein reverses the damage caused by acute and chronic kidney disease, a preclinical study suggests. In a world first, scientists at Duke-NUS Medical School, the National Heart…
Unconventional superconductivity found in kagome metal
Physicists using advanced muon spin spectroscopy at Paul Scherrer Institute PSI make the missing link between their recent breakthrough in a kagome metal and unconventional superconductivity. The team uncovered an…
Discovery of new ice may change understanding of water
Researchers at UCL (University College London) have discovered a new type of ice that more closely resembles liquid water than any other known ices and that may rewrite our understanding…