| Authors: | Bayati, Reza; Molaei, Roya; Wu, Fan; Narayan, Jagdish; Yarmolenko, Sergey |
| Title: | Dependence of Semiconductor to Metal Transition of VO2(011)/NiO{100}/MgO{100}/TiN{100}/Si{100} Heterostructures on Thin Film Epitaxy and Nature of Strain |
| Type: | Journal Article |
| Publisher: | Journal of the American Ceramic Society |
| Year: | 2015 |
| Volume: | 98 |
| Issue: | 4 |
| Start Page: | 1201 |
| End Page: | 1208 |
| DOI: | 10.1111/jace.13454 |
| WEB-link: | http://dx.doi.org/10.1111/jace.13454 |
| Abstract: | We have studied semiconductor to metal transition (SMT) characteristics of VO2(011) thin films integrated epitaxially with Si(100) through NiO{001}/MgO{001}/TiN{001} buffer layers and correlated with the details of epitaxy and nature of residual stresses and strains across the VO2/NiO interface. Thin film epitaxy at both room and elevated temperatures is studied in detail by electron microscopy and in situ high-temperature X-ray diffraction techniques. The epitaxial relationship across the interface between monoclinic VO2 and NiO is determined to be (011)VO2||{100}NiO and [01¯1]VO2||[001]NiO at room temperature. The epitaxial alignment at the temperature of growth where tetragonal VO2 is stable is determined as: (110)VO2||{100}NiO and [001]VO2||[100]NiO. A cube-on-cube crystallographic alignment is established across the NiO{100}/MgO{100}/TiN{100}/Si{100} interfaces. The misfit strains across the VO2/NiO interface at the growth temperature are calculated and the mechanism of strain relaxation is discussed. The out-of-plane orientation is found to be relaxed in both monoclinic and tetragonal states of VO2. It is shown that a compressive strain of 31.65% along the [001] direction of tetragonal VO2 is fully relaxed via matching of multiple domains. However, a small tensile misfit strain of about 5% along [11¯0] direction cannot relax and remains in the lattice. This tensile residual strain leads to a compressive strain along [001] axis which, in turn, results in an SMT temperature slightly lower than that of freestanding strain-free VO2. SMT characteristics of VO2(011) epilayers are assessed where an amplitude of near five orders of magnitude, and a hysteresis of less than 3.6 °C are obtained. This study introduces VO2/NiO thin film heterostructure integrated with silicon as a promising candidate for multifunctional devices with novel characteristics where a combination of sensing, manipulation, and response functions is needed. |
