Probing Elastic Properties of Atomically-thin Interfacial Layer by Femtosecond Acoustics
Date Issued
2015
Date
2015
Author(s)
Chen, Hui-Yuan
Abstract
While the developing trend of modern electronic devices is toward scaling down, heat removal is a critical issue since thermal effect becomes seriously significant as dimensions shrink. Besides, many complex and denser structures such as 3D integrated circuits or FinFET were designed to exploit the limited space and optimize the overall device performance, which is a trend well-characterized by Moore’s law. However, it is well-known that an interfacial layer (IL) is usually formed between two adjacent heterogeneous materials. The existence of this unavoidable interfacial layer might hinder the heat conduction in those fabricated devices, and thus certainly diminishes their operational lifetime. Since heat is mainly carried by acoustic phonons, elastic property of materials is among the essential information for thermal management. Unfortunately, a proper technology to probe the elastic property of this atomically-thin interfacial layer has not yet been documented. In this thesis, we designed an interfacial layer (IL) model system between bulk GaN and Al2O3 film, and conducted femtosecond acoustic measurement to obtain the elastic properties of the IL. The acoustic impedance, mass density and a cross-plane elastic constant of the IL were successfully obtained. We further evaluated a 16% reduction in thermal energy transmission owing to the IL from a theoretical calculation. With the capability of probing the elastic properties across layers of only several atoms thick, our demonstration could be deemed as the first step to deal with heat dissipation issue stemming from the ILs. Hopefully, our approach will provide a better thermal management for nano-scaled devices in the future.
Subjects
interfacial layer
elastic property
femtosecond acoustics
phonon
thermal management
Type
thesis
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