EP3874557B1

EP3874557B1 - Magnetically tunable resonator

Info

Publication number: EP3874557B1
Application number: EP19791282.7A
Authority: EP
Inventors: Robert Blick; Max Lagally
Original assignee: Universitaet Hamburg; Wisconsin Alumni Research Foundation
Current assignee: Universitaet Hamburg; Wisconsin Alumni Research Foundation
Priority date: 2018-10-29
Filing date: 2019-10-29
Publication date: 2024-04-03
Anticipated expiration: 2039-10-29
Also published as: EP3874557A1; LU101038B1

Description

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.
Prior art useful for understanding the present disclosure can be found in GB 1 268 223 A , US 7 758 919 B2 , US 3 740 675 A , US 2018/006603 A1 , Vasily N. Astratov: "Fundamentals and Applications of Microsphere Resonator Circuits", Springer Series in Optical Sciences, 1 January 2010, Springer, DE, vol. 156, pages 423-457, and C. E. Fay ET AL: "Operation of the Ferrite Junction Circulator", IEEE Transactions on Microwave Theory and Techniques, 1 January 1965, pages 15-27. According to an aspect of the present disclosure, there is provided a process of manufacturing a magnetically tunable nano-resonator as defined in claim 1, and in a another aspect there is provided a microwave device comprising a plurality of magnetically tunable nano-resonators as defined in claim 10. The nano-resonator comprises a nanoparticle of a 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. 1a, Fig. 1b, 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. 5d 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. 1a and Fig. 1b show schematic cross-sectional and top views of a nanomembrane 10 (e.g., a silicon membrane with a thickness of about 50 microns or less). During a first processing step, two nanomembranes 10 are 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 are 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 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 devicecompatible 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 are 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 are then 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 are 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, nanoresonators 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. 5c and Fig. 5d.
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
10a: 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

Claims

A method of manufacturing a magnetically tunable resonator (20), the method comprising:
forming (26) a first layer (10a) having first wells (12); and

adding a second layer (10b) having second wells (12) matching the first wells (12) to the first layer (10a);

wherein the method is characterized by

flowing (28) a colloid comprising colloidal nanoparticles (18) of a magnetic material over the first layer (10a); and

drying (30) the first layer (10a);

wherein a cavity (12a) formed by two matching wells (12) comprises a nanoparticle (18) of a magnetic material, and a resonance frequency of the nanoparticle (18) oscillating within the cavity (12a) is tunable by flowing an electrical current through two electrodes of the magnetically tunable resonator (20) which extend into directions that are perpendicular to each other and at least partially encircle the cavity (12a).
The method of manufacturing a magnetically tunable resonator (20) of claim 1, wherein the nanoparticles (18) are spheres of yttrium-iron-garnet.
The method of manufacturing a magnetically tunable resonator (20) of claim 1 or 2, further comprising:
manufacturing the first layer (10a) and the second layer (10b) from flexible nanomembranes (10).
The method of manufacturing a magnetically tunable resonator (20) of any one of claims 1 to 3,
wherein the first layer (10a) and the second layer (10b) comprise a semiconductor material.
The method of manufacturing a magnetically tunable resonator (20) of any one of claims 1 to 4, further comprising:
forming the wells (12) by applying a photolithographic process to the first and second layer (10a, 10b).
The method of manufacturing a magnetically tunable resonator (20) of any one of claims 1 to 5,
wherein the matching first and second wells (12) form cavities (12a).
The method of manufacturing a magnetically tunable resonator (20) of claim 6, wherein the cavities (12a) form a cavity array.
The method of manufacturing a magnetically tunable resonator (20) of any one of claims 1 to 7,
wherein at least one of the first and the second layer (10a, 10b) comprises electrically conductive material.
The method of manufacturing a magnetically tunable resonator (20) of any one of claims 1 to 8,
wherein the resonance frequency is tunable to frequencies above 1 Terahertz.
A microwave device, comprising:
a plurality of magnetically tunable nano-resonators (20), wherein the nanoresonators (20) comprise nanoparticles (18) of a magnetic material embedded into cavities (12a) of a flexible sheet of the microwave device;

wherein the flexible sheet comprises a first layer (10a) bonded to a second layer (10b), both layers (10a, 10b) being made from flexible semiconductor nanomembranes (10);

wherein both layers (10a, 10b) comprise electrodes and each of said cavities (12a) is at least partially encircled by two electrodes of the microwave device which extend into directions that are perpendicular to each other and which are configured for magnetically tuning the nanoresonators (20).
The microwave device of claim 10,
wherein the nanoparticles (18) are spheres of yttrium-iron-garnet.
The microwave device of claim 10 or 11,
wherein the cavities (12a) form a cavity array.
The microwave device of any one of claims 10 to 12,
wherein different nano-resonators (20) are configured to be independently tunable.
The microwave device of any one of claims 10 to 13,
wherein the microwave device is a device selected from a group consisting of a microwave receiver, a microwave emitter, a microwave filter, and a microwave mixer.
The microwave device of any one of claims 10 to 14,
wherein the first layer (10a) or the second layer (10b) comprises a graphene layer (32).