On‐Demand Nanoscale Manipulations of Correlated Oxide Phases

Abstract

Controlling material properties at the nanoscale is a critical enabler of high performance electronic and photonic devices. A prototypical material example is VO 2 , where a structural phase transition in correlation with dramatic changes in resistivity, optical response, and thermal properties demonstrates particular technological importance. While the phase transition in VO 2 can be controlled at macroscopic scales, reliable and reversible nanoscale control of the material phases has remained elusive. Here, reconfigurable nanoscale manipulations of VO 2 from the pristine monoclinic semiconducting phase to either a stable monoclinic metallic phase, a metastable rutile metallic phase, or a layered insulating phase using an atomic force microscope is demonstrated at room temperature. The capability to directly write and erase arbitrary 2D patterns of different material phases with distinct optical and electrical properties builds a solid foundation for future reprogrammable multifunctional device engineering.

Reversible Nanomodulation of Thin Vanadium Dioxide Films by a Tip-Induced Electric Field

“…Because the experiments are conducted in ambient air, a thin water film presents on the surfaces of both the tip and sample, which can contribute to the hydrate formation under the action of a local electric field. However, it should be noted that the height expansion under a negative bias is different from the reported results in the literature. , In ref , a negative bias did not cause a morphology change. In ref , the authors proposed that only a negative bias following after a positive bias could induce layered expansions.…”

“…The oxygen ions provided by the VO 2 are supposed to be attracted to the top surface and react with the hydronium ions. The produced oxygen vacancies are compelled to the opposite side, which make the local VO 2 film more insulating. ,, When a negative bias is applied, the ions and vacancies may behave oppositely. As a consequence, the tip written area will have different structural, electric, or optical properties as compared with the unprocessed area.…”

“…Similar to the case of applying a positive bias, the saturation in CPD is observed when the bias voltage is smaller than −6 V. Meanwhile, the saturation in the height increment appears when the negative tip bias is smaller than −8 V. The largest increment above the unprocessed surrounding is approximately 10 nm at a −10 V bias, which is almost 50% of the pristine VO 2 film thickness. We attribute the height expansion under the negative bias to the forming of hydrates such as VO 2 ·H 2 O and V 2 O 5 ·H 2 O . Because the experiments are conducted in ambient air, a thin water film presents on the surfaces of both the tip and sample, which can contribute to the hydrate formation under the action of a local electric field.…”

Rewritable Nanoplasmonics through Room-Temperature Phase Manipulations of Vanadium Dioxide

“…Scanning probe writings are performed using an Asylum MFP-3D atomic force microscope in contact mode while applying a DC bias between the tip and sample. The detailed method is discussed in ref . s-SNOM and KPFM imaging are performed using a customized variable temperature multifunctional scanning probe system manufactured by RHK technologies.…”

“…Another tunable material that can be used in photonic applications is VO 2 . − VO 2 is a lossy dielectric , in its room-temperature monoclinic-insulator phase (MI-phase), and it turns into a rutile metal (RM-phase) − at elevated temperatures. While this high-temperature phase can support surface plasmon polaritons (SPP) at infrared frequencies, ,, its applications in chip-scale polariton manipulations have been very restricted since the thermally driven phase transition is slow, volatile, and difficult to control at nanoscales. ,,, Recently, we have discovered a new technique that allows a monoclinic-metal VO 2 phase (MM-phase) to be created at room temperature using a biased atomic force microscope (AFM) probe . Using this technique, stable nanoscale MM-phase structures with arbitrary shapes can be flexibly and reversibly patterned on the MI-phase background.…”