Thermal transport properties in GaAs (110)/GaAs (100) and GaAs/InAs interfaces by Reverse Non-equilibrium Molecular Dynamics

It is well known that the physics of thermal management is quite challenging as electronic device sizes are miniaturized and new materials are developed. This study calculates the thermal interface conductance (TIC), thermal interface resistance (TIR) and thermal grain conductivity across GaAs(110)/GaAs(100) and GaAs/InAs interfaces using the reverse non-equilibrium molecular dynamics (RNEMD) technique. Data obtained showed that, at GaAs(110)/GaAs(100) the TIC increased from 0.912 x 10-9 (W/K) to 1.433 x 10-9 (W/K), the TIR decreased from 1.096 x 109 (K/W) to 0.697 x 109 (K/W) between 300 K and 1000 K, and the thermal grain conductivity increased from 7.47 (W/mK) to 15.52 (W/mK) and 7.48 (W/mK) to 80.71 (W/mK) between 15 Å and 55 Å at 300 K. At GaAs/InAs interface the TIC increased from 7.228 x -10 (W/K) to 14.498 x 10-10 (W/K) and the TIR decreased from 0.138 x 1010 (K/W) to 0.068 x 1010 (K/W) between 300 K and 700 K, respectively. It was observed that, as temperature is increased the TIC and TIR for both materials change significantly. This trend is consistent with previous molecular dynamic studies of interface materials.Keywords: Interface conductance, thermal resistance, grain conductivity, temperature.

Reliability Investigation of a Carbon Nanotube Array Thermal Interface Material

As feature density increases within microelectronics, so does the dissipated power density, which puts an increased demand on thermal management. Thermal interface materials (TIMs) are used at the interface between contacting surfaces to reduce the thermal resistance, and is a critical component within many electronics systems. Arrays of carbon nanotubes (CNTs) have gained significant interest for application as TIMs, due to the high thermal conductivity, no internal thermal contact resistances and an excellent conformability. While studies show excellent thermal performance, there has to date been no investigation into the reliability of CNT array TIMs. In this study, CNT array TIMs bonded with polymer to close a Si-Cu interface were subjected to thermal cycling. Thermal interface resistance measurements showed a large degradation of the thermal performance of the interface within the first 100 cycles. More detailed thermal investigation of the interface components showed that the connection between CNTs and catalyst substrate degrades during thermal cycling even in the absence of thermal expansion mismatch, and the nature of this degradation was further analyzed using X-ray photoelectron spectroscopy. This study indicates that the reliability will be an important consideration for further development and commercialization of CNT array TIMs.

Structural and Thermal Characterisation of Nanofilms by Time-Resolved X-ray Scattering

High time resolution in scattering analysis of thin films allows for determination of thermal conductivity by transient pump-probe detection of dissipation of laser-induced heating, TDXTS. We describe an approach that analyses the picosecond-resolved lattice parameter reaction of a gold transducer layer on pulsed laser heating to determine the thermal conductivity of layered structures below the transducer. A detailed modeling of the cooling kinetics by a Laplace-domain approach allows for discerning effects of conductivity and thermal interface resistance as well as basic depth information. The thermal expansion of the clamped gold film can be calibrated to absolute temperature change and effects of plastic deformation are discriminated. The method is demonstrated on two extreme examples of phononic barriers, isotopically modulated silicon multilayers with very small acoustic impedance mismatch and silicon-molybdenum multilayers, which show a high resistivity.