Reduction in thermal boundary conductance due to proton implantation in silicon and sapphire

Hopkins, Patrick E.; Hattar, Khalid Mikhiel; Beechem, Thomas Edwin; Ihlefeld, Jon F.; Medlin, Douglas L.; Piekos, Edward S.

doi:10.1063/1.3592822

Cited by 25 publications

(25 citation statements)

References 24 publications

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“…In general, interfacial imperfections have been observed to lead to a decrease in phonon thermal boundary conductance [1]. We have experimentally observed this decrease in thermal boundary conductance across interfaces with roughness (i.e., geometric disorder) [20,21], an amorphous layer (i.e., structural disorder) [22][23][24], dislocations [25], and elemental mixing resulting in both compositional and structural disorder [26]. In each of these cases, the disorder led to a reduction in thermal boundary conductance.…”

Section: Introductionmentioning

confidence: 79%

“…For our measurements, we use pump and probe 1/e 2 radii of 25 and 10.5 μm, respectively, and a pump-modulation frequency of 11.39 MHz. These experimental parameters not only ensure primarily one-dimensional, cross-plane conduction during our TDTR measurements [42,43], but also establish a thermal penetration depth that is less than the end of range of the irradiated ions [23]. This simplifies our analysis as we only need to consider the substrate as the ion-irradiated silicon and not as a layered system with an ion-implanted layer, a highly defected end of range, and a semi-infinite, unaffected silicon substrate.…”

Section: B Time-domain Thermoreflectance Measurementsmentioning

confidence: 89%

“…In the nonirradiated samples, the factor of nearly 2 increase in h K when the substrate is cleaned indicates the importance of cleaning as-received wafers to remove contaminants that can affect h K . The decrease in h K observed in the ion-irradiated samples that were not subjected to plasma cleaning is due to a build up of carbon contamination on the silicon surface [23,24]. When the carbonaceous layer is removed via plasma cleaning, an increase in h K is observed.…”

Section: B Time-domain Thermoreflectance Measurementsmentioning

confidence: 93%

“…of Al/Si h K when the Si contains a native oxide layer on the surface and is alcohol cleaned [22]. The decrease in h K observed in the ion-irradiated samples that were not subjected to plasma cleaning is suspected to be due to a build up of hydrocarbons on the silicon surface resulting from the ion irradiation [23,24]. We confirm the presence of this carbonaceous layer, and its increase with ion dose, with Raman spectroscopy and cross-sectional transmission electron microscopy (TEM) [24].…”

Section: B Time-domain Thermoreflectance Measurementsmentioning

confidence: 98%

“…These realizations may offer insight into variations found in literature regarding measurements of thermal boundary conductance across Al/Si interfaces. In several of our previous works [1,[20][21][22][23]66], we have measured the thermal boundary conductance across Al/native oxide/Si interfaces with different interfacial properties. In general, the measured values of h K across the various interfaces span from ∼110-200 MW m −2 K −1 .…”

Section: Additional Considerationsmentioning

confidence: 99%

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Ion irradiation of the native oxide/silicon surface increases the thermal boundary conductance across aluminum/silicon interfaces

et al. 2014

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The thermal boundary conductance across solid-solid interfaces can be affected by the physical properties of the solid boundary. Atomic composition, disorder, and bonding between materials can result in large deviations in the phonon scattering mechanisms contributing to thermal boundary conductance. Theoretical and computational studies have suggested that the mixing of atoms around an interface can lead to an increase in thermal boundary conductance by creating a region with an average vibrational spectra of the two materials forming the interface. In this paper, we experimentally demonstrate that ion irradiation and subsequent modification of atoms at solid surfaces can increase the thermal boundary conductance across solid interfaces due to a change in the acoustic impedance of the surface. We measure the thermal boundary conductance between thin aluminum films and silicon substrates with native silicon dioxide layers that have been subjected to proton irradiation and post-irradiation surface cleaning procedures. The thermal boundary conductance across the Al/native oxide/Si interfacial region increases with an increase in proton dose. Supported with statistical simulations, we hypothesize that ion beam mixing of the native oxide and silicon substrate within ∼2.2 nm of the silicon surface results in the observed increase in thermal boundary conductance. This ion mixing leads to the spatial gradation of the silicon native oxide into the silicon substrate, which alters the acoustic impedance and vibrational characteristics at the interface of the aluminum film and native oxide/silicon substrate. We confirm this assertion with picosecond acoustic analyses. Our results demonstrate that under specific conditions, a "more disordered and defected" interfacial region can have a lower resistance than a more "perfect" interface.

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