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

Dong Kyu Lee,Hyeji Sim,Junwoo Son,Si-Young Choi,Gi-Yeop Kim,Chang-Beom Eom,Yunkyu Park,Jinheon Park,Younghak Kim

doi:10.1038/s41467-021-24740-2

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 > 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.

Highlights

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
While crystalline materials that are intrinsically layered (e.g. two-dimensional (2D) materials) are exfoliated spontaneously due to weak van der Waals bonding between layers[22], the freestanding NM from three-dimensional (3D) oxide crystals with strong bonding is hindered by the technical challenges of lifting strongly bonded epitaxial films from the oxide substrates
Th and Tc were defined at the peak position of the Gaussian and the transition width was calculated from the difference (4H = Th − Tc)

Summary

Introduction

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. The stacking of single-crystalline oxide films on dissimilar substrates (e.g., silicon (Si)) will offer ways to integrate the emergent phenomena of oxides with mature electronic and photonic devices[9,10,11,12,13]. Physical release methods (e.g., laser lift-off20) were originally developed to release epitaxial GaN semiconductor films to break strong bonding. These methods are only applicable to the formation of thick semiconductor membranes due to the inevitable structural damage. The harsh wet condition with a strong acid or base etchant typically leaves roughening and residue on the host substrates or released membrane after the chemical etch[23,24]

Methods

Results

Conclusion