Measurement and analysis of thermal conductivity of isotopically controlled silicon layers by time-resolved X-ray scattering

• Published in: Physica status solidi. A, Applications and materials science Vol. 213; no. 11; pp. 3020 - 3028
• Main Authors: Eon, S., Frieling, R., Plech, A., Bracht, H.
• Format: Journal Article
• Language: English
• Published: Weinheim Blackwell Publishing Ltd 01.11.2016; Wiley Subscription Services, Inc
• Subjects: Conductivity; Cooling; Cooling effects; Electronic properties; Gold; Heat conductivity; Heat transfer; Laser beam heating; Laser cooling; Measurement techniques; Multilayers; nanostructures; Scattering; Silicon; silicon isotopes; Thermal conductivity; X-ray scattering; X-rays
• ISSN: 1862-6300; 1862-6319
• DOI: 10.1002/pssa.201532607

Nanostructuring is considered to be an efficient way to tailor phonon scattering and to reduce the thermal conductivity while keeping good electronic properties. This can be ideally realized by mass modulation of chemical identical elements. In this work, we report measurements of the crossplane thermal conductivity of isotopically modulated 28Si/30Si multilayer structures and of isotopically pure 28Si layers by means of time‐resolved X‐ray scattering. Compared to earlier investigations, an improved measurement technique has been applied to determine the cooling behavior of a top gold metal layer after laser excitation with picosecond time resolution until thermal equilibration is established. Detailed analysis of the cooling behavior not only confirms a reduced thermal conductivity of 28Si/30Si multilayer structures compared to natural and isotopically enriched 28Si layers but also provides evidence of direct laser heating of the Si layer. This and extrinsic effects affecting the cooling behavior of the gold layer are taken into account to determine the thermal conductivity by means of the pump‐and‐probe measurement technique.