Heterogeneous integration of single-crystalline rutile nanomembranes with steep phase transition on silicon substrates

Abstract

Unrestricted integration of single-crystal oxide films on arbitrary substrates has been of great interest to exploit emerging phenomena from transition metal oxides for practical applications. Here, we demonstrate the release and transfer of a freestanding single-crystalline rutile oxide nanomembranes to serve as an epitaxial template for heterogeneous integration of correlated oxides on dissimilar substrates. By selective oxidation and dissolution of sacrificial VO2 buffer layers from TiO2/VO2/TiO2 by H2O2, millimeter-size TiO2 single-crystalline layers are integrated on silicon without any deterioration. After subsequent VO2 epitaxial growth on the transferred TiO2 nanomembranes, we create artificial single-crystalline oxide/Si heterostructures with excellent sharpness of metal-insulator transition ($$\triangle \rho /\rho$$ △ ρ / ρ > 103) even in ultrathin (<10 nm) VO2 films that are not achievable via direct growth on Si. This discovery offers a synthetic strategy to release the new single-crystalline oxide nanomembranes and an integration scheme to exploit emergent functionality from epitaxial oxide heterostructures in mature silicon devices.

Exponential Escape Rate of Filamentary Incubation in Mott Spiking Neurons

“…Therefore, according to our model, the switching of VO 2 grown on Al 2 O 3 should display much more prominent stochastic behavior compared to the VO 2 prepared on TiO2. We note that, with the recent progress of synthesis and transfer of nanomembranes [39], highquality VO 2 films could be integrated with virtually any substrate. Using such a nanomembrane approach, it is possible to test our model at extremes, for example, synthesizing VO 2 on a sulfur crystal [thermal conductivity approximately 0.2 W/(mK), resulting in deterministic switching] or on diamond [thermal conductivity approximately 2000 W/(mK), resulting in stochastic switching].…”

Freestanding complex-oxide membranes

“…The fact that single-crystal oxide membranes transferred to flexible polymer substrates show magnetic and electrical properties comparable to their precursor epitaxial films, even under bending conditions [94,[200][201][202], opens a path toward implementing this fabrication technology in flexible, wearable electronics. In some cases, when epitaxial strain becomes detrimental to the oxides functionalities, the released membranes can even display improved performance, such as higher Curie temperature and magnetization in colossal magnetoresistance manganites [90,134] or larger resistivity modulation in rutile oxides showing metal-to-insulator transitions [95,108], which further encourages the development of multifunctional devices incorporating complex oxide membranes.…”

Anionic Flow Valve Across Oxide Heterointerfaces by Remote Electron Doping

“…Temperature-dependent sheet resistance ( R S ( T )) could sensitively investigate the modulation of the oxygen deficiency in the underlying VO 2 layers depending on the remote Nb addition in the TiO 2 capping layers (Figure d,e). In the TiO 2 /VO 2 heterostructures, the steepness of the MI transition (i.e., Δ T h ; Table S1) was substantially reduced from Δ T h = 1.61 K for VO 2 to Δ T h = 18 K for TiO 2 /VO 2 . , This result indicates that oxygen ionic transfer across the TiO 2 /VO 2 interfaces strongly suppressed the MI transition of the VO 2 layers by the V O formation. In contrast, the steepness of the MI transition was retained around the T MI value after the growth of the upper Nb:TiO 2 films (Δ T h = 1.61 K for VO 2 → Δ T h = 1.72 K for Nb:TiO 2 /VO 2 ), which indicates the occurrence of negligible ionic transfer at the Nb:TiO 2 and VO 2 interfaces.…”

“…This represents the formation of stoichiometric and tensilestrained VO 2 films with negligible V O concentration before the growth of the capping layers. 10,12,25 Subsequently, 10 nm thick TiO 2 films without dopants (denoted as TiO 2 /VO 2 ) and with Nb dopants ([Nb] = 13.5 atom %, denoted as Nb:TiO 2 /VO 2 ; Figure S1) were epitaxially grown on the (001) R -VO 2 (10 nm)/TiO 2 substrates under the growth conditions of T g ≈ 300 °C and p Od 2 ≈ 10 mTorr. The symmetriccal θ−2θ scans by synchrotron X-ray radiation exhibit the strong Bragg reflections from TiO 2 (or Nb:TiO 2 ) and VO 2 due to the perfect epitaxy of both heterostructures (Figure 1b).…”

“…Prior to the epitaxial growth of the undoped and Nb-doped TiO 2 capping layers, 10 nm thick epitaxial VO 2 layers were grown on a (001)-oriented TiO 2 substrate under optimized growth conditions (i.e., T g ≈ 300 °C; p O 2 ≈ 10 mTorr) by pulsed laser deposition (PLD). , Both X-ray diffraction and electrical measurements exhibited sharp (002) R reflection from the VO 2 epitaxial films (Figure b) and a steep MI transition with 3 orders of magnitude resistance modulation at the transition temperature ( T MI ≈ 296 K; Figure d), respectively. This represents the formation of stoichiometric and tensile-strained VO 2 films with negligible V O concentration before the growth of the capping layers. ,, …”