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Non-linear Hybrid Microwave Resonators Made by He-Beam Assisted Deposition of Tungsten Nanowires

J. Basset, Diana Watfa, Gianluca Aiello, Mathieu Féchant, Alexis Morvan, Jérôme Estève, Julien Gabelli, M. Aprili, Raphaël Weil, Alik Yu. Kasumov, Hélène Bouchiat, R. Deblock

Published Nov 15, 2018• 0 citations
OpenAlex

Abstract

We evaluate the performance of hybrid microwave resonators made by combining sputtered Nb thin films with Tungsten nanowires grown with a He-beam induced deposition technique. Depending on growth conditions the nanowires have a typical width $w\in[35-75]$~nm and thickness $t\in[5-40]$~nm. We observe a high normal state resistance $R_{sq}\in [65-150]$ $\Omega/sq$ which together with a critical temperature $T_c\in[4-6]~K$ ensure a high kinetic inductance fraction making the resonator strongly nonlinear. Both lumped and coplanar waveguide resonators were fabricated and measured at low temperature exhibiting internal quality factors up to $3990$ at $4.5$~GHz in the few photon regime. Analyzing the wire length, temperature and microwave power dependence we extracted a kinetic inductance for the W nanowire of $L_K\approx15$ pH/$sq$, a kinetic inductance fraction $\alpha_{W,He}=0.996$ and a Kerr non-linearity as high as $K_{W,He}/2\pi=164$~Hz/photon at $4.5$~GHz. This study allows us to conclude that the nanowires made with the helium focused ion beam are very versatile objects to engineer compact, high impedance, superconducting environments.

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Fabrication and Characterization of Superconductive Coplanar Waveguide Resonators : Fabrication and Characterization of Superconductive Coplanar Waveguide Resonators

Adem Ergül

The objective of this thesis is to evaluate a generic process for fabrication and characterization of the Superconductive coplanar waveguide (CPW) resonators. Superconductive CPW resonators with various lengths and shapes are designed to investigate their electrical and magnetic properties as well as resonance properties and sensitivities. In the first part of thesis, two different models are introduced in order to estimate the nonlinear kinetic inductance of a superconducting CPW resonator. The first model is based on Bean critical-state model and the second one is based on current dependence of London penetration depth. The existence of a shift in resonant frequency of Superconductive CPW resonator caused by a non-linear kinetic inductance is also shown experimentally. Simulations were carried out to estimate the nonlinear kinetic inductance due to the self- induced magnetic field penetration. The rest of the thesis is concerned with development of very smooth Aluminum (Al) thin films with RMS (Root Mean Square) roughness 1~nm and CAD (Computer Aid Design) of superconductive CPW resonators. Experimental investigation of a generic fabrication technique for superconductive CPW resonator is carried out. Many resonators are fabricated with different design parameters, such as centerline or gap width, film thickness and gap capacitors length. The fabrication process is described in detail. Electron Beam Lithography is used to fabricate Nb and Al CPW resonators which are coupled to outer conductors via gap capacitors. We have fabricated GHz frequency CPW resonators with quality factors, Q up 5X10^5.

•Jan 1, 2009•0 citations
We evaluate the performance of hybrid microwave resonators made by combining sputtered Nb thin films with Tungsten nanowires grown with a He-beam induced deposition technique. Depending on growth conditions the nanowires have a typical width w∈[35−75]w\in[35-75]w∈[35−75]~nm and thickness t∈[5−40]t\in[5-40]t∈[5−40]~nm. We observe a high normal state resistance Rsq∈[65−150]R_{sq}\in [65-150]Rsq​∈[65−150] Ω/sq\Omega/sqΩ/sq which together with a critical temperature Tc∈[4−6] KT_c\in[4-6]~KTc​∈[4−6] K ensure a high kinetic inductance fraction making the resonator strongly nonlinear. Both lumped and coplanar waveguide resonators were fabricated and measured at low temperature exhibiting internal quality factors up to 399039903990 at 4.54.54.5~GHz in the few photon regime. Analyzing the wire length, temperature and microwave power dependence we extracted a kinetic inductance for the W nanowire of LK≈15L_K\approx15LK​≈15 pH/sqsqsq, a kinetic inductance fraction αW,He=0.996\alpha_{W,He}=0.996αW,He​=0.996 and a Kerr non-linearity as high as KW,He/2π=164K_{W,He}/2\pi=164KW,He​/2π=164~Hz/photon at 4.54.54.5~GHz. This study allows us to conclude that the nanowires made with the helium focused ion beam are very versatile objects to engineer compact, high impedance, superconducting environments.
We evaluate the performance of hybrid microwave resonators made by combining sputtered Nb thin films with Tungsten nanowires grown with a He-beam induced deposition technique. Depending on growth conditions, the nanowires have a typical width w [35 - 75] nm and thickness t [5 - 40] nm. We observe a high normal state resistance R [65 - 150] Ω / which together with a critical temperature T c [4 - 6] K ensures a high kinetic inductance making the resonator strongly nonlinear. Both lumped and coplanar waveguide resonators were fabricated and measured at low temperature exhibiting internal quality factors up to 3990 at 4.5 GHz in the few photon regime. Analyzing the wire length, temperature, and microwave power dependence, we extracted a kinetic inductance for the W nanowire of L K 15 pH / which is 250 times higher than the geometrical inductance, and a Kerr non-linearity as high as K W, He / 2 π = 200 ± 120 Hz / photon at 4.5 GHz. The nanowires made with the helium focused ion beam are thus versatile objects to engineer compact, high impedance, superconducting environments with a mask and resist free direct write process.
We evaluate the performance of hybrid microwave resonators made by combining sputtered Nb thin films with Tungsten nanowires grown with a He-beam induced deposition technique. Depending on growth conditions, the nanowires have a typical width w∈[35−75] nm and thickness t∈[5−40] nm. We observe a high normal state resistance R◻∈[65−150] Ω/◻ which together with a critical temperature Tc∈[4−6] K ensures a high kinetic inductance making the resonator strongly nonlinear. Both lumped and coplanar waveguide resonators were fabricated and measured at low temperature exhibiting internal quality factors up to 3990 at 4.5 GHz in the few photon regime. Analyzing the wire length, temperature, and microwave power dependence, we extracted a kinetic inductance for the W nanowire of LK≈15 pH/◻, which is 250 times higher than the geometrical inductance, and a Kerr non-linearity as high as KW,He/2π=200±120 Hz/photon at 4.5 GHz. The nanowires made with the helium focused ion beam are thus versatile objects to engineer compact, high impedance, superconducting environments with a mask and resist free direct write process.
Abstract Tantalum (Ta) has recently received considerable attention in manufacturing robust superconducting quantum circuits. Ta offers low microwave loss, high kinetic inductance compared to aluminium (Al) and niobium (Nb), and good compatibility with complementary metal-oxide-semiconductor (CMOS) technology, which is essential for quantum computing applications. Here we demonstrate the fabrication engineering of thickness-dependent high-quality-factor (high-  Qi\:{Q}_{i}Qi​ ) Ta superconducting microwave coplanar waveguide resonators. All films are deposited on high-resistivity silicon substrates at room temperature without additional substrate heating. Before Ta deposition, a niobium (Nb) seed layer is used to promote a body-centred cubic lattice (  α \:\alpha\:α -Ta) formation. We further engineer the kinetic inductance (  LK\:{L}_{K}LK​ ) of the resonators by varying Ta film thicknesses. High  LK\:{L}_{K}LK​ is a key advantage for applications because it facilitates the realisation of high-impedance, compact quantum circuits with enhanced coupling to qubits. The maximum internal quality factor  Qi\:{Q}_{i}Qi​ of  ∼ \:\sim\:∼ 3.6 × 10 6 in the high power regime and  Qi\:{Q}_{i}Qi​ of  ∼ \:\sim\:∼ 4.5 × 10 5 in the single-photon regime is achieved for 100 nm Ta which represents an improvement over previous room-temperature deposited Ta resonators on silicon substrates in the single photon regime, while the highest kinetic inductance of 0.6 pH/sq is obtained for the thinnest film, which is 40 nm. This combination of high  Qi\:{Q}_{i}Qi​ and high  LK\:{L}_{K}LK​ highlights the potential of Ta microwave circuits for high-fidelity operation of compact quantum circuits.
Tantalum (Ta) has recently received considerable attention in manufacturing robust superconducting quantum circuits. Ta offers low microwave loss, high kinetic inductance compared to aluminium (Al) and niobium (Nb), and good compatibility with complementary metal-oxide-semiconductor (CMOS) technology, which is essential for quantum computing applications. Here, we demonstrate the fabrication engineering of thickness-dependent high quality factor (high-Q_i) Ta superconducting microwave coplanar waveguide resonators. All films are deposited on high-resistivity silicon substrates at room temperature without additional substrate heating. Before Ta deposition, a niobium (Nb) seed layer is used to ensure a body-centred cubic lattice (α-Ta) formation. We further engineer the kinetic inductance (L_K) resonators by varying Ta film thicknesses. High L_K is a key advantage for applications because it facilitates the realisation of high-impedance, compact quantum circuits with enhanced coupling to qubits. The maximum internal quality factor Q_i of ~ 3.6 * 10^6 is achieved at the high power regime for 100 nm Ta, while the highest kinetic inductance is obtained to be 0.6 pH/sq for the thinnest film, which is 40 nm. This combination of high Q_i and high L_K highlights the potential of Ta microwave circuits for high-fidelity operations of compact quantum circuits.
We characterize niobium nitride (NbN) λ/2 coplanar waveguide resonators, which were fabricated from a 10-nm-thick film on silicon dioxide grown by sputter deposition. For films grown at 180 °C, we report a superconducting critical temperature of 7.4 K associated with a normal square resistance of 1 kΩ, leading to a kinetic inductance of 192 pH/◻. We fabricated resonators with a characteristic impedance up to 4.1 kΩ and internal quality factors Qi>104 in the single photon regime at zero magnetic field. Moreover, in the many photon regime, the resonators present a high magnetic field resilience with Qi>104 in a 6 T in-plane magnetic field and in a 300 mT out-of-plane magnetic field. These findings make such resonators a compelling choice for circuit quantum electrodynamics experiments involving quantum systems with small electric dipole moments operated in finite magnetic fields.
The objective of this thesis is to evaluate a generic process for fabrication and characterization of the Superconductive coplanar waveguide (CPW) resonators. Superconductive CPW resonators with various lengths and shapes are designed to investigate their electrical and magnetic properties as well as resonance properties and sensitivities. In the first part of thesis, two different models are introduced in order to estimate the nonlinear kinetic inductance of a superconducting CPW resonator. The first model is based on Bean critical-state model and the second one is based on current dependence of London penetration depth. The existence of a shift in resonant frequency of Superconductive CPW resonator caused by a non-linear kinetic inductance is also shown experimentally. Simulations were carried out to estimate the nonlinear kinetic inductance due to the self- induced magnetic field penetration. The rest of the thesis is concerned with development of very smooth Aluminum (Al) thin films with RMS (Root Mean Square) roughness 1~nm and CAD (Computer Aid Design) of superconductive CPW resonators. Experimental investigation of a generic fabrication technique for superconductive CPW resonator is carried out. Many resonators are fabricated with different design parameters, such as centerline or gap width, film thickness and gap capacitors length. The fabrication process is described in detail. Electron Beam Lithography is used to fabricate Nb and Al CPW resonators which are coupled to outer conductors via gap capacitors. We have fabricated GHz frequency CPW resonators with quality factors, Q up 5X10^5.