Bulk-like dielectric and magnetic properties of sub 100 nm thick single crystal Cr2O3 films on an epitaxial oxide electrode

Abstract

The manipulation of antiferromagnetic order in magnetoelectric Cr2O3 using electric field has been of great interest due to its potential in low-power electronics. The substantial leakage and low dielectric breakdown observed in twinned Cr2O3 thin films, however, hinders its development in energy efficient spintronics. To compensate, large film thicknesses (250 nm or greater) have been employed at the expense of device scalability. Recently, epitaxial V2O3 thin film electrodes have been used to eliminate twin boundaries and significantly reduce the leakage of 300 nm thick single crystal films. Here we report the electrical endurance and magnetic properties of thin (less than 100 nm) single crystal Cr2O3 films on epitaxial V2O3 buffered Al2O3 (0001) single crystal substrates. The growth of Cr2O3 on isostructural V2O3 thin film electrodes helps eliminate the existence of twin domains in Cr2O3 films, therefore significantly reducing leakage current and increasing dielectric breakdown. 60 nm thick Cr2O3 films show bulk-like resistivity (~ 1012 Ω cm) with a breakdown voltage in the range of 150–300 MV/m. Exchange bias measurements of 30 nm thick Cr2O3 display a blocking temperature of ~ 285 K while room temperature optical second harmonic generation measurements possess the symmetry consistent with bulk magnetic order.

Defect Nanostructure and its Impact on Magnetism of α‐Cr2O3 Thin Films

“…It appears that growing the samples at 500 °C even with an additional post-annealing at 700 °C (sample #5, Table 1) is insufficient to realize an antiferromagnetic film responding to the field cooling procedure (green curve in Figure 2a). This finding is in line with the recent work by Vu et al, [43] where it is reported that a good crystallinity is observed for Cr 2 O 3 thin films grown at 700 °C (compare to the properties of thin films prepared at a lower temperature [44,45] ). While the sample grown at 800 °C (sample #3, Table 1) reveals the strongest change of the transversal resistance (red curve in Figure 2a), the film prepared at 900 °C (sample #4, Table 1, blue curve in Figure 2a) shows the weakest measured transverse resistance change among all samples.…”

“…[44,45] Good crystallinity of Cr 2 O 3 thin films is observed when they are grown at 700 °C. [43] Furthermore, post-annealing of the room temperature grown Cr 2 O 3 thin films shows an increase in the size of individual grains. [56] Transmission Electron Microscopy Studies: TEM analysis was conducted on thin cross-sections of specimens.…”

“…[ 44,45 ] Good crystallinity of Cr 2 O 3 thin films is observed when they are grown at 700 °C. [ 43 ] Furthermore, post‐annealing of the room temperature grown Cr 2 O 3 thin films shows an increase in the size of individual grains. [ 56 ]…”

Multiferroic heterostructures for spintronics

“…Linear magnetoelectric switching is defined by a critical energy product of electric field and magnetic field [10], meaning magnetoelectric switching of Cr2O3 requires either substantial static magnetic fields [106,107] or extraordinarily large voltages. This presents a significant engineering challenge for scaling of devices, as a Cr2O3 thin film must be able to withstand voltages large enough for switching, and significant work is currently focused on increasing the breakdown voltage or decreasing the switching threshold for thin films [108,109]. Thus far, magnetoelectric switching in thin film heterostructures has required substantial magnetic fields on the order of ~0.6-1 T [93,106,107], but the technology remains promising for scale multiferroic devices.…”

Porous-Spherical Cr2O3-Cr(OH)3-Polypyrrole/Polypyrrole Nanocomposite Thin-Film Photodetector and Solar Cell Applications

“…On the other hand, Cr 2 O 3 has particular photo-response properties, ensuring a good detection within a long and large optical range [11,12]. Numerous synthetic routes have been developed to obtain Cr 2 O 3 nanoparticles, such as hydrothermal, sol-gel, forced hydrolysis, radiation, sonochemical and hydrolysis-condensation processes [13][14][15].…”