Session: 08-02: Micro/Nanoscale Heat Conduction

Paper Number: 101197

101197 - Nanoscale Thermal Cloak Based on Amorphous Hole Structure of Silicon Film 

Abstract: 

With the continuous development of microelectronic devices in the direction of miniaturization, diversification and high frequencies, the excessive heat flux density within the device has a non-negligible impact on its service life and operational stability. Thermal isolation is a frequently employed method in thermal design. Researchers have built thermal cloaks by amorphizing crystalline silicon films to construct functional regions, and in the previous work, we successfully built the thermal cloak through perforation, but the perforated structure is not conducive to the stability of the system. Therefore, in this paper, we construct a thermal cloak by filling the perforated region with an amorphous structure, which can guarantee both cloaking performance and system stability. We evaluate its cloaking performance by the ratio of thermal cloaking (RTC). Compared with the perfect silicon film, the RTC of the films with amorphous hole structure is all greater than 1, which proves that the cloaking phenomenon occurs, and with the increase of the number of holes, the RTC increases, but the general trend slows down. When the number of small holes reaches a certain level, the entire region becomes amorphous, and the RTC reaches the maximum value at this time. Besides, we explain its cloaking mechanism through phonon localization theory, We first calculated the phonon density of states (PDOS), For the perfect silicon film, a low-frequency peak and a high-frequency peak appear at low frequency 5.5 THz and high frequency 17 THz, respectively, which is consistent with previous studies. The film with 8 amorphous holes also shows a low frequency peak and a high frequency peak like the perfect silicon film, but the peaks are reduced. For the silicon films with 16 and 18 amorphous holes, the low-frequency peaks and high-frequency peaks decrease, and the frequency of the peaks is shifted to the left, the PDOS increases at 0-5 THz, and a large number of phonon modes appear at 5-15 THz. Next, the mode participation rate was calculated on the basis of phonon density of states， For perfect silicon films, most of the MPR are greater than 0.6, indicating that these phonon modes have been decentralized. For silicon films with 8 amorphous holes, a small fraction is greater than 0.6. For silicon films with 16 and 24 amorphous holes, most MPR are below 0.6, demonstrating the localization of phonon modes. Furthermore, the MPR decreases with the increase in the number of amorphous holes. It shows that the main reason for the decrease of thermal conductivity in the functional region is the phonon localization in the functional region. Our study is beneficial for advancing the development of nanoscale thermal cloaks and can provide a reference for the development of other nanoscale thermal functional devices.

Presenting Author: Haochun Zhang Harbin Institute of Technology

Presenting Author Biography: Haochun Zhang is a professor and doctoral supervisor in the School of Energy of Harbin Institute of Technology. He is the director of the Institute of Nuclear Science and Technology, the head of the national first-class undergraduate major construction point of "Nuclear Engineering and Technology", and the leader of the discipline direction of "Nuclear Energy Science and Engineering". His main research interests include thermal metamaterials, advanced nuclear energy systems, and new optoelectronic countermeasure technologies. He is in charge of more than 10 national projects, including the National Natural Science Foundation of China (NSFC), National Science and Technology Major Project for Large Advanced Pressurized Water Reactor and High Temperature Gas-Cooled Reactor Nuclear Power Plant, National Key Research and Development Project, and many other key military/civilian projects, such as Beijing Institute of Space Mechanics, China Aviation Industry Corporation, China National Nuclear Corporation, and China Shipbuilding Industry Corporation. He is the executive director of the Reactor Thermodynamics Branch of the Chinese Nuclear Society and a member of the Special Committee on Optoelectronic Technology of the Chinese Society of Military Industry. He is a guest associate editor/editorial board member of 8 international and domestic journals, including Entropy, and an invited reviewer of more than 60 international journals, including Applied Energy. He has published more than 200 academic papers, with more than 700 citations, and two of them have been selected as ESI highly cited papers. He has been granted 8 national invention patents and 15 software copyrights. He has received more than 10 academic awards, including the Krupp Foundation Scholarship for Young Chinese Scholars.

Authors:

Haochun Zhang Harbin Institute of Technology
Jian Zhang Harbin Institute of Technology