Epitaxial NbN/AlN/NbN tunnel junctions on Si substrates with TiN buffer layers

Sun, Rui; Makise, Kazumasa; Zhang, Lu; Terai, Hirotaka; Wang, Zhen

doi:10.1063/1.4954743

Cited by 12 publications

(11 citation statements)

References 22 publications

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“…2.1 Preparation of full-epitaxial NbN/AlN/NbN tri-layer Details of the fabrication process of full-epitaxial NbN/AlN/NbN tri-layer structure on a Si (100) wafer can be found in our early report [14,15]. Firstly, a 40-nm-thick TiN film was deposited on a hydrogen-terminated Si substrate at a substrate temperature of 850°C with a total outgas pressure of 1×10 -6 Pa by dc magnetron sputtering method.…”

Section: Fabrication Processmentioning

confidence: 99%

“…However, the obtained energy relaxation time T1 was about 500 ns due to a large dielectric loss from the MgO substrate and the MgO/NbN interface [6]. To reduce the substrate related loss, we have developed the growth technique of a full-epitaxial NbN/AlN/NbN tri-layer on a single-crystal Si (100) wafer by using a (200)-oriented TiN film as a buffer layer [14,15].…”

Section: Introductionmentioning

confidence: 99%

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Fabrication of deep-sub-micrometer NbN/AlN/NbN epitaxial junctions on a Si-substrate

Qiu

Terai

2020

Appl. Phys. Express

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We have developed a novel fabrication process for ultra-small, full-epitaxial NbN Josephson junctions on a silicon (Si) substrate. A full-epitaxial NbN/AlN/NbN tri-layer was grown on a Si (100) wafer with a (200)-oriented TiN buffer layer. It was patterned into Josephson junctions by an electron beam lithography (EBL) for junction definition followed by a reactive ion etch (RIE). A chemical mechanical polishing (CMP) process and an additional RIE by using CHF3 gas formed reliable electrical contacts between the junction counter electrodes and the wiring layer. All fabricated junctions, with a junction size down to 0.27 m in diameter, showed excellent current-voltage characteristics with a clear gap structure and a small sub-gap leakage current. The dielectric layer of SiO2 that served as an insulator between base and counter electrodes was removed in a wet etching process using a buffered HF solution. We have confirmed that the quality of the junctions was maintained after the removal of the SiO2 dielectric layer.

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Section: Fabrication Processmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Fabrication of deep-sub-micrometer NbN/AlN/NbN epitaxial junctions on a Si-substrate

Qiu

Terai

2020

Appl. Phys. Express

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“…The utility of epitaxial transition metal nitride (TMN) thin films has been demonstrated in a diverse array of applications, including the fabrication of Josephson junctions [1][2][3][4], single photon detectors [5,6], acoustic resonators [7,8], thermoelectric transducers [9,10], epitaxial nucleation and sacrificial layers [11][12][13], optical metamaterials [14], and the realization of topological electronic systems [15]. In addition to their intrinsic properties, a primary reason for the interest in TMN thin films is the ability to epitaxially integrate III-N semiconductors and TMNs to create structures which include semiconductor, metallic, superconductor, and ferroelectric thin films [16].…”

Section: Introductionmentioning

confidence: 99%

Growth windows of epitaxial $\textrm{Nb}_x\textrm{N}$ films on c-plane sapphire and their structural and superconducting properties

Wright¹,

Xing²,

Jena³

2022

Preprint

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NbN films are grown on c-plane sapphire substrates by molecular beam epitaxy. The structural and superconducting properties of the film are characterized to demonstrate that growth parameters such as substrate temperature and active nitrogen flux effect the structural phase of films, and thereby the superconducting critical temperature. Four phases of NbN are identified for films grown in different conditions. In a novel finding, we demonstrate that atomically flat and highly crystalline β-Nb2N films can be grown at substrate temperatures of 1100 • C or higher, and that the superconducting critical temperature of phase pure β-Nb2N films is 0.35 K < Tc < 0.6 K, based on measurements of films grown at different substrate temperatures.

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“…Therefore, the thickness of AlN selected in this experiment is within 1 nm to ensure that the upper NbN still has a single crystal structure. The epitaxial growth of NbN on single crystal Si (200) substrate is mainly characterized by (111) and (100) cubic structure, and the AlN film is characterized by (111) hexagonal structure [ 20 , 27 , 28 ]. There is no primary orientation relationship between NbN and AlN grown under different process conditions.…”

Section: Methodsmentioning

confidence: 99%

Directly Controlling the Transport Properties of All-Nitride Josephson Junctions by N-Vacancy Defects

Qiu¹,

Sun²,

Wang³

et al. 2023

Nanomaterials

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All-nitride Josephson junctions are being actively explored for applications in superconducting quantum chips because of their unique advantages including their antioxidant chemical stability and high crystal quality. However, the theoretical research on their microstructure mechanism that determines transport properties is still absent, especially on the defects. In this paper, we apply the first principles and non-equilibrium Green’s function to calculate the electrical transport characteristics of the yellow preset model. It is first revealed that the N-vacancy defects play a crucial role in determining the conductivity of the NbN-based Josephson junctions, and demonstrate the importance for the uniformity of vacancy distribution. It is found that the uniform number of vacancies can effectively increase the conductance of Josephson junction, but the position distribution of vacancies has little effect on the conductance. The work clarifies the effect of the N-vacancy defects on the conductivity of the NbN-based Josephson junctions, which offers useful guidance for understanding the microscope mechanism of the NbN-based Josephson junction, thus showing a great prospect in the improvement of the yield of superconducting quantum chips in the future.

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Epitaxial NbN/AlN/NbN tunnel junctions on Si substrates with TiN buffer layers

Cited by 12 publications

References 22 publications

Fabrication of deep-sub-micrometer NbN/AlN/NbN epitaxial junctions on a Si-substrate

Fabrication of deep-sub-micrometer NbN/AlN/NbN epitaxial junctions on a Si-substrate

Growth windows of epitaxial $\textrm{Nb}_x\textrm{N}$ films on c-plane sapphire and their structural and superconducting properties

Directly Controlling the Transport Properties of All-Nitride Josephson Junctions by N-Vacancy Defects

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