Ultimate suppression of thermal transport in amorphous silicon nitride by phononic nanostructure

Abstract

Engineering the thermal conductivity of amorphous materials is highly essential for the thermal management of future electronic devices. Here, we demonstrate the impact of ultrafine nanostructuring on the thermal conductivity reduction of amorphous silicon nitride (a-Si3N4) thin films, in which the thermal transport is inherently impeded by the atomic disorders. Ultrafine nanostructuring with feature sizes below 20 nm allows us to fully suppress contribution of the propagating vibrational modes (propagons), leaving only the diffusive vibrational modes (diffusons) to contribute to thermal transport in a-Si3N4. A combination of the phonon-gas kinetics model and the Allen-Feldmann theory reproduced the measured results without any fitting parameters. The thermal conductivity reduction was explained as extremely strong diffusive boundary scattering of both propagons and diffusons. These findings give rise to substantial tunability of thermal conductivity of amorphous materials, which enables us to provide better thermal solutions in microelectronic devices.

Vertical Engineering for Large Brillouin Gain in Unreleased Silicon-Based Waveguides

“…The excess of Si in low-stress SiN x increases the refractive index slightly, which has to be taken into account when designing the devices [35], though the index will be always lower than in the silicon (either crystalline or nanocrystalline) core. Importantly, the speed of sound in amorphous SiN x layers deposited using LPCVD is quite similar to the value we use in our calculations [36], so mechanical leakage will be extremely suppressed. Once the stack with matched stress is available, the patterning of the waveguides is straightforward by optical or e-beam lithography and dry etching.…”

Phonons Manipulation in Silicon Chips Using Cavity Optomechanics

“…Typically, Si 3 N 4 layers used in integrated photonics are deposited using low-pressure chemical vapor deposition (LPCVD), since this method enables low propagation losses at telecom wavelengths [181]. Interestingly, 70 nm Si 3 N 4 layers deposited using LPCVD exhibit sound speeds quite similar to the ones we have used in our calculations [182]. This means that the intermediate layer of our waveguiding structure could be in principle built by depositing an amorphous silicon nitride layer on top of a silica substrate using LPCVD.…”

Nanoscale Thermoelasticity in Silicon Nitride Membranes: Implications for Thermal Management

“…We finally mention that this experiment constitutes a further step toward the application of EUV TG to more complex nanostructures. Indeed, the understanding of the EUV TG response on a free-standing membrane, which represents the simplest mechanically confined structure, is a prerequisite for extending this approach to, for example, thin coatings and multilayers, as well as nanostructured samples for catalysis and thermal trapping. − …”