Phonon and electron transport through Ge2Sb2Te5 films and interfaces bounded by metals

Abstract

While atomic vibrations dominate thermal conduction in the amorphous and face-centered cubic phases of Ge2Sb2Te5, electrons dominate in the hexagonal closed-packed (hcp) phase. Here we separate the electron and phonon contributions to the interface and volume thermal resistances for the three phases using time-domain thermoreflectance and electrical contact resistance measurements. Even when electrons dominate film-normal volume conduction (i.e., 70% for the hcp phase), their contribution to interface heat conduction is overwhelmed by phonons for high-quality interfaces with metallic TiN.

Evaluating Broader Impacts of Nanoscale Thermal Transport Research

“…An additional (and fundamentally enticing) complexity is Downloaded by [New York University] at 07: 56 12 June 2015 the strongly differing roles of electron and phonon transport depending on the material phase, as shown by the thermal conductivity data in Figure 2c. Though atomic vibrations are responsible for heat conduction in the amorphous phase, electron heat conduction can become important in at least one of the crystalline phases [116,128]. The acoustic properties of the crystalline phases are very similar, and the difference in the thermal conductivity is attributed to the electron contribution, which is also in good agreement with predictions using the Wiedemann-Franz law and separate measurements of electrical properties [116,128].…”

“…(b) Schematic illustration of the programming pulses, which require extreme temperature transients, which involve complex electrothermal phenomena. (c) Room-temperature thermal conductivity data for Ge 2 Sb 2 Te 5 films [114][115][116][117][118][119][120][121][122][123][124][125][126][127][128][129][130]. The circles are obtained from the 3ω measurements [114, 115, 119-121, 126, 127] and the diamonds are obtained from the TDTR measurements [116-118, 122-125, 128-130].…”

“…Though atomic vibrations are responsible for heat conduction in the amorphous phase, electron heat conduction can become important in at least one of the crystalline phases [116,128]. The acoustic properties of the crystalline phases are very similar, and the difference in the thermal conductivity is attributed to the electron contribution, which is also in good agreement with predictions using the Wiedemann-Franz law and separate measurements of electrical properties [116,128]. Heat conduction across interfaces with surrounding passivation and electrode materials (SiO 2 [121,123], ZnS:SiO2 [114], TiN [125,128,130], Al [129]) is governed by acoustic properties and interfacial disorder [125,130].…”

“…The PCM research community has leveraged and extended the TDTR and 3ω methodologies to reveal a variety of the fascinating thermal transport phenomena that occur in the phase-change chalcogenides [114][115][116][117][118][119][120][121][122][123][124][125][126][127][128][129][130]. The TDTR methodology has proven useful for extracting coupled (and even decoupling [125]) film and interface properties.…”

Phase Change Dynamics and Two-Dimensional 4-Bit Memory in Ge2Sb2Te5 via Telecom-Band Encoding

“…[36][37][38] A thermal boundary resistance of 0.9 m 2 KG W was assumed between the GST and the silicon layer. 39 Further, the crystallite sizes of 14 nm and 27 nm for the face-centered cubic (fcc) and haxagonal close-packed (hcp) crystalline phases were estimated from the full width at half maximum approach on the XRD peaks of annealed GST at 170 ÂřC and 350 ÂřC, respectively. Using the local refractive indices at 1550 nm wavelength 40 as an input into the frequency-dependent electromagnetic wave simulation domain, the reflectivity of the 255 nm thick GST film was calculated to be 0.547 and 0.433 in the crystalline and amorphous phases, respectively.…”