Kapitza conductance of Bi/sapphire interface studied by depth- and time-resolved X-ray diffraction

Sheu, Yu-Miin; Trigo, M.; Chien, Yi-Jiunn; Uher, C.; Arms, D. A.; Peterson, E. R.; Walko, Donald A.; Landahl, Eric C.; Chen, J.; Ghimire, Shambhu; Reis, David A.

doi:10.1016/j.ssc.2011.03.022

Cited by 11 publications

(23 citation statements)

References 11 publications

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“…Therefore the front surface of the film has been heated much more than the back interface. This is consistent with recent time-resolved x-ray diffraction experiments on the thermal transport in Bi, in which the thermal gradient is maintained for a time on order nanoseconds for comparable thickness films 39,40 . This demonstrates that lattice heating must occur substantially faster than the time (≈ 5 ps) taken for diffusion to produce a uniform plasma in the 185 nm thick film.…”

Section: Results and Discussion For Low Excitationsupporting

confidence: 92%

Free-carrier relaxation and lattice heating in photoexcited bismuth

et al. 2013

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We report ultrafast surface pump and interface probe experiments on photoexcited carrier transport across single crystal bismuth films on sapphire. The film thickness is sufficient to separate carrier dynamics from lattice heating and strain, allowing us to investigate the time-scales of momentum relaxation, heat transfer to the lattice and electron-hole recombination. The measured electron-hole (e − h) recombination time is 12-26 ps and ambipolar diffusivity is 18-40 cm 2 /s for carrier excitation up to ∼ 10 19 cm −3 . By comparing the heating of the front and back sides of the film, we put lower limits on the rate of heat transfer to the lattice, and by observing the decay of the plasma at the back of the film, we estimate the timescale of electron-hole recombination. We interpret each of these timescales within a common framework of electron-phonon scattering and find qualitative agreement between the various relaxation times observed. We find that the carrier density is not determined by the e − h plasma temperature after a few picoseconds. The diffusion and recombination become nonlinear with initial excitation > ∼ 10 20 cm −3 .

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Section: Results and Discussion For Low Excitationsupporting

confidence: 92%

Free-carrier relaxation and lattice heating in photoexcited bismuth

et al. 2013

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“…1(a)] [26]. Therefore, as in thicker films, the ΔR=R signals measured on our thin LCMO film originate from laser heating-induced DSWT [17,18].…”

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confidence: 67%

“…However, thickness-dependent measurements on a series of LCMO films (not shown) reveal that their origin is the same [31]. This is confirmed by a numerical simulation for 1 D thermal diffusion across an interface, which demonstrates that the faster decay times in thin films result from the strong influence of the substrate thermal diffusion on thermal transport, rather than diffusion [26]. Insets show the dynamics at early times.…”

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confidence: 78%

Polaronic Transport Induced by Competing Interfacial Magnetic Order in aLa0.7Ca0.3MnO3/BiFe

Sheu

Trugman

et al. 2014

Phys. Rev. X

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Using ultrafast optical spectroscopy, we show that polaronic behavior associated with interfacial antiferromagnetic order is likely the origin of tunable magnetotransport upon switching the ferroelectric polarity in a La 0.7 Ca 0.3 MnO 3 =BiFeO 3 (LCMO/BFO) heterostructure. This is revealed through the difference in dynamic spectral weight transfer between LCMO and LCMO/BFO at low temperatures, which indicates that transport in LCMO/BFO is polaronic in nature. This polaronic feature in LCMO/BFO decreases in relatively high magnetic fields due to the increased spin alignment, while no discernible change is found in the LCMO film at low temperatures. These results thus shed new light on the intrinsic mechanisms governing magnetoelectric coupling in this heterostructure, potentially offering a new route to enhancing multiferroic functionality. The quest to achieve strong magnetoelectric coupling has driven the surge in research on multiferroic materials over the past decade. However, this has been quite difficult to accomplish using bulk materials, motivating researchers to explore other approaches, most notably the use of transition metal oxide heterostructures [1][2][3]. In these novel systems, different degrees of freedom (DOFs) (e.g., charge, spin, and orbital) are coupled at a single interface between two different oxide layers to form a new state that displays properties dramatically different from those of the individual layers [4][5][6][7][8]. Particular attention has been given to the coupling between ferromagnetic (FM), antiferromagnetic (AFM), and ferroelectric (FE) orders, as this could reveal new routes to realizing strong magnetoelectric coupling [1][2][3][9][10][11].Heterostructures consisting of manganite and multiferroic layers are particularly promising in this regard. The most extensively studied combination [2,3,9,10,12] consists of the colossal magnetoresistive manganite La 0.7 Sr 0.3 MnO 3 (LSMO) [or the similar compound La 0.7 Ca 0.3 MnO 3 (LCMO)], which is ferromagnetic below a critical temperature T c , and the canonical multiferroic BiFeO 3 (BFO), which has coexisting coupled AFM and FE phases in which the magnetization can be switched by an applied electric (E) field [13]. The combination of these materials thus has great potential for exhibiting novel phenomena by coupling different FM, AFM, and FE phases across the interface. Indeed, a new interfacial state between LSMO and BFO has been discovered experimentally and discussed theoretically [2,[14][15][16]. This state displays an exchange-bias field and magnetotransport that can be tuned by switching the FE polarization, increasing the potential for device control through interfacial coupling. However, a complete picture of the interplay between FM and AFM orders in this heterostructure has yet to be reached.Current understanding of the exchange-bias field, which arises from the interaction between FM and G-type AFM [AFMðGÞ] orders at the interface, is based on spin canting or pinning in BFO, with the assumption of negligible canting in ...

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“…Using these expressions, mean-square displacement of atoms can be evaluated. Many researcher used Debye temperature of sapphire as about 9001000 K. 21,22) Here, we also assume Figure 6 presents an Arrhenius plot of the growth rate of the LPE AlN. The apparent activation energy was determined as 220 kJ·mol ¹1 from the slope of this linear relation.…”

Section: Annealing Effectsmentioning

confidence: 99%

Elimination of Rotational Domain in AlN Layers Grown from Ga–Al Flux and Effects of Growth Temperature on the Layers

et al. 2012

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We have been investigating crystal growth of AlN on nitrided sapphire substrates, and have grown c-axis oriented AlN layers using liquid phase epitaxy (LPE) with GaAl fluxes. However, rotational domains having 1-deg difference around the c-axis exist in the AlN layers. One of the purposes of this study is to eliminate the rotational domains. To do so, an annealing process at elevated temperatures was attempted before the LPE process. Then, its effectiveness was discussed. The origin of the rotational domain was explained using distortion of O 2¹ ions arrangement in (0002) sapphire surface. The mechanism of the eliminating the domains was discussed using the lattice vibration of the sapphire at elevated temperatures. Secondly, effects of growth temperature on the AlN layers were investigated in terms of the growth rate, surface morphology and crystal quality. The growth rate of the LPE AlN layer increased concomitantly with increasing growth temperature at 1373 1673 K. The growth rate attained at 1673 K was 0.52 µm·h ¹1 . Crystal quality is almost independent of the growth temperature in that temperature range.

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Kapitza conductance of Bi/sapphire interface studied by depth- and time-resolved X-ray diffraction

Cited by 11 publications

References 11 publications

Free-carrier relaxation and lattice heating in photoexcited bismuth

Free-carrier relaxation and lattice heating in photoexcited bismuth

Polaronic Transport Induced by Competing Interfacial Magnetic Order in aLa0.7Ca0.3MnO3/BiFe

Elimination of Rotational Domain in AlN Layers Grown from Ga–Al Flux and Effects of Growth Temperature on the Layers

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Kapitza conductance of Bi/sapphire interface studied by depth- and time-resolved X-ray diffraction

Cited by 11 publications

References 11 publications

Free-carrier relaxation and lattice heating in photoexcited bismuth

Free-carrier relaxation and lattice heating in photoexcited bismuth

Polaronic Transport Induced by Competing Interfacial Magnetic Order in aLa0.7Ca0.3MnO3/BiFe

Elimination of Rotational Domain in AlN Layers Grown from Ga&ndash;Al Flux and Effects of Growth Temperature on the Layers

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Elimination of Rotational Domain in AlN Layers Grown from Ga–Al Flux and Effects of Growth Temperature on the Layers