title: Control of Nanoplane Orientation in voBN for High Thermal Anisotropy in a Dielectric Thin Film: A New Solution for Thermal Hotspot Mitigation in Electronics.
abstract: High anisotropic thermal materials, which allow heat to dissipate in a preferential direction, are of interest as a prospective material for electronics as an effective thermal management solution for hot spots. However, due to their preferential heat propagation in the in-plane direction, the heat spreads laterally instead of vertically. This limitation makes these materials ineffective as the density of hot spots increases. Here, we produce a new dielectric thin film material at room temperature, named vertically ordered nanocrystalline h-BN (voBN). It is produced such that its preferential thermally conductive direction is aligned in the vertical axis, which facilitates direct thermal extraction, thereby addressing the increasing challenge of thermal crosstalk. The uniqueness of voBN comes from its h-BN nanocrystals where all their basal planes are aligned in the direction normal to the substrate plane. Using the 3ω method, we show that voBN exhibits high anisotropic thermal conductivity (TC) with a 16-fold difference between through-film TC and in-plane TC (respectively 4.26 and 0.26 W·m-1·K-1). Molecular dynamics simulations also concurred with the experimental data, showing that the origin of this anisotropic behavior is due to the nature of voBN's plane ordering. While the consistent vertical ordering provides an uninterrupted and preferred propagation path for phonons in the through-film direction, discontinuity in the lateral direction leads to a reduced in-plane TC. In addition, we also use COMSOL to simulate how the dielectric and thermal properties of voBN enable an increase in hot spot density up to 295% compared with SiO2, without any temperature increase.
authors.affiliation: CINTRA CNRS/NTU/THALES, UMI 3288 , Research Techno Plaza, 50 Nanyang Drive, Border X Block, Level 6, 637553, Singapore.
authors.forename: Olivier
authors.identifier: http://orcid.org/0000-0003-0269-3624
authors.initials: O
authors.lastname: Cometto
authors.affiliation: Electronics Materials and Systems Laboratory, Department of Microtechnology and Nanoscience, Chalmers University of Technology , SE-412 96 Göteborg, Sweden.
authors.forename: Majid K
authors.initials: MK
authors.lastname: Samani
authors.forename: Bo
authors.initials: B
authors.lastname: Liu
authors.affiliation: Electronics Materials and Systems Laboratory, Department of Microtechnology and Nanoscience, Chalmers University of Technology , SE-412 96 Göteborg, Sweden.
authors.forename: Shuangxi
authors.initials: S
authors.lastname: Sun
authors.affiliation: Temasek Laboratories@NTU , 50 Nanyang Avenue, 639798, Singapore.
authors.forename: Siu Hon
authors.initials: SH
authors.lastname: Tsang
authors.affiliation: Electronics Materials and Systems Laboratory, Department of Microtechnology and Nanoscience, Chalmers University of Technology , SE-412 96 Göteborg, Sweden.
authors.forename: Johan
authors.initials: J
authors.lastname: Liu
authors.forename: Kun
authors.initials: K
authors.lastname: Zhou
authors.affiliation: School of Electrical and Electronics Engineering, Nanyang Technological University , Block S1, 50 Nanyang Avenue, 639798, Singapore.
authors.forename: Edwin H T
authors.initials: EH
authors.lastname: Teo
keywords: 3 omega; Boron nitride; COMSOL; Molecular dynamics; Thermal conductivity