The present disclosure relates to magnetically tunable resonators. As used throughout the specification, the term“magnetically tunable resonator” refers to a resonator where the resonance frequency of the resonator can be adapted (within a given range) by varying a magnetic field applied to one or more components of the resonator.

According to an aspect of the present disclosure, there is provided a process of manufacturing a magnetically tunable nano-resonator. The nano-resonator comprises a nanoparticle of a crystalline magnetic material which is embedded into a cavity of a substrate. During operation, the nanoparticle may perform an oscillatory movement within the cavity, wherein the resonance frequency of the oscillatory movement may be tuned by applying a magnetic field to the nanoparticle.

The nano-resonator may be used to emit electromagnetic waves that have a wavelength which matches the resonance frequency. For example, an alternating electromagnetic field with a spectrum that includes the resonance frequency may be applied to the nanoparticle. The alternating electromagnetic field may be produced by an alternating current flown through wiring formed in the substrate.

The nano-resonator may also be used to receive electromagnetic waves that have a wavelength which matches the resonance frequency. For example, the nanoparticle may be exposed to an alternating electromagnetic field with a spectrum that includes the resonance frequency. The received electromagnetic waves may produce an alternating current flowing through wiring formed in the substrate which may be further processed.

Hence, the nano-resonator may be used within an oscillator, an antenna, a filter (tunable bandpass), a mixer, etc. BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing aspects and many of the attendant advantages will become more readily appreciated as the same becomes better understood by reference to the following detailed description, when taken in conjunction with the accompanying drawings, wherein like reference numerals refer to like parts throughout the various views, unless otherwise specified.

Fig. la, Fig. lb, Fig. 2a, Fig. 2b, Fig. 3a, Fig. 3b, and Fig. 4a to Fig. 4d schematically illustrate a process of manufacturing a magnetically tunable nano resonator;

Fig. 5 shows a block diagram of a microwave device in which the nano resonator may be integrated;

Fig. 5a, Fig. 5b, Fig. 5c, and Fig. sd show a block diagram of a receiver, an emitter, a filter and a mixer, respectively, in which the nano-resonator may be integrated;

Fig. 6 shows a flow-chart of the process; and

Fig. 7 illustrates a modification of the microwave device of Fig. 5.

Notably, the drawings are not drawn to scale and unless otherwise indicated, they are merely intended to conceptually illustrate the structures and procedures described herein.

DETAILED DESCRIPTION

Fig. la and Fig. lb show schematic cross-sectional and top views of a nanomembrane to (e.g., a silicon membrane with a thickness of about 50 microns or less). During a first processing step, two nanomembranes 10 may be provided with an array of wells 12. For example, the wells 12 may be etched into the nanomembranes 10 by applying a photolithographic process (e.g., dry reactive ion etching, DRIE, and/or nanoimprint lithography, NIL). Moreover, electrically conductive traces (wiring) 14 may be added to the layers 10a, 10b as illustrated in Fig. 2a, Fig. 2b, Fig. 3a, and Fig. 3b. Notably, the wiring 14 (electrodes) of the two layers 10a, 10b may extend in directions that are perpendicular to each other to avoid (or reduce) cross coupling. Instead of integrating the wiring 14 into the layers 10a, 10b, the wiring 14 may also be integrated into (additional) adjacent layers on a chip. For example, the nanomembranes 10 may be strain engineered and then transferred on a device compatible substrate with a patterning according to the device required. Moreover, rather than having an electrode grid (where each electrode extends over a full row/column of wells 12 as shown in Fig. 2b and Fig. 3b), one or more wells 12 in the same row/column may be provided with wiring 14 that can be operated independently from wiring 14 provided to other wells 12 in said row/column.

As illustrated in Fig. 4a, one of the layers 10a may be rinsed with a colloid including nanoparticles (metallic or semiconducting) with a magnetic moment. Such colloids are commercially available, e.g., from CAN GmbH, Hamburg, Germany. Rinsing may also be performed as batch processing, where multiple chips are rinsed in a single process step.

The chips may then be dried such that the magnetic nanoparticles 18 (e.g., spheres made from yttrium-iron-garnet, YIG, or another material) become trapped in the wells 12, as illustrated in Fig. 4b. After drying the chips, the layers 10a, 10b may be bonded together (e.g., by making use of a wafer-bonder) as illustrated in Fig. 4c, such that the magnetic nanoparticles 18 are arranged in cavities 12a formed by matching wells 12. Each cavity 12a comprising a magnetic nanoparticle 18 and wiring 14 partially encircling the cavity 12a form a nano resonator 20 as illustrated in Fig. 4d. The wiring 14 may then be contacted on the outskirts of the chips and may be addressed in parallel or separately. The micro/millimeter-wave resonators 20 (or nano-resonators for short) may be integrated into a microwave device 21, as shown in Fig. 5. For example, nano resonators 20 may be integrated into a receiver 22 or an emitter 24, as schematically illustrated in Fig. 5a and Fig. 5b. Furthermore, nano-resonators 20 may be integrated into a filter 25a or a mixer 25b as schematically illustrated in Fig. sc and Fig. sd.

The above described process allows scaling down existing YIG-microwave sources to the nanoscale, while maintaining their output power density. Furthermore, embedding the nano resonators 20 within nanomembranes 10 allows designing flexible sources/sinks of electromagnetic radiation. This may be particularly advantageous for microwave sources which require focusing the emitted radiation and for all non-planar surfaces, i.e., in sensor, smart phone, and other applications.

A flow-chart of the process is shown in Fig. 6. At step 22, the first layer 14a is formed. At step 24, a colloid 16 comprising colloidal nanoparticles 18 of a crystalline magnetic material are flown over the first layer 14a and the first layer 14a is dried such that the nanoparticles 18 become trapped in the wells 12. At step 26, the second layer 14b is added to the first layer 14a, such that the nanoparticles 18 are arranged in cavities of the flexible sheet formed by the layers 14a, 14b.

As schematically illustrated in Fig. 7, a nano-resonator 20 may be provided with a graphene layer 32 (e.g., a mono- or bilayer). The graphene layer 32 may be part of one of the nanomembrane layers 10a, 10b. Moreover, a voltage applied to the graphene layer 32 may be measured and/or controlled. Likewise, a current through the graphene layer 32 may be measured and/or controlled.

LIST OF REFERENCE NUMERALS

10 nanomembrane

ioa layer

10b layer

12 well

12a cavity

14 wiring

16 colloid

18 nanoparticle

20 nano-resonator

21 device

22 receiver

24 emitter

25a filter

25b mixer

26 process step

28 process step

30 process step

32 graphene layer