Single photon detection performance of high ly disordered NbTiN thin films Ruoyan Ma123 Rui Shu4 Xingyu Zhang12 Aobo Yu123 Huang Jia12 You Xiao123 Huiqi n Yu12 Xiaoyu Liu12 Hao Li123 Per Eklund4 Xiaofu Zhang123 Lixing You123

2025-05-03 1 0 537.02KB 9 页 10玖币

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Single photon detection performance of highly disordered NbTiN thin films

Ruoyan Ma1,2,3, Rui Shu4, Xingyu Zhang1,2, Aobo Yu1,2,3, Huang Jia1,2, You Xiao1,2,3, Huiqin

Yu1,2, Xiaoyu Liu1,2, Hao Li1,2,3, Per Eklund4, Xiaofu Zhang1,2,3,*, Lixing You1,2,3,*

1State Key Laboratory of Functional Materials for Informatics, Shanghai Institute of Microsystem and

Information Technology, Chinese Academy of Sciences (CAS), Shanghai 200050, China

2University of Chinese Academy of Sciences, Center of Materials Science and Optoelectronics

Engineering, Beijing, China, 100049

3CAS Center for Excellence in Superconducting Electronics (CENSE), Shanghai 200050, China

4Thin Film Physics Division, Department of Physics Chemistry, and Biology (IFM), Linköping

University, Linköping SE-581 83, Sweden

E-mail: zhangxf@mail.sim.ac.cn and lxyou@mial.sim.ac.cn

Abstract

We experimentally investigated the detection performance of highly disordered

 based superconducting nanowire single photon detectors (SNSPDs). The

dependence on the composition of the transition temperature 

 for  films show

a dome-like behavior on the Nb content, with a maximal 

 at  , and the

 films also combine relatively large sheet resistance and intermediate residual

resistivity ratio. Moreover, 60-nm-wide and 7-nm-thick  nanowires show a

switching current as high as 14.5 μA, and saturated intrinsic detection efficiency with a plateau

of more than 2 μA at 2.4 K. Finally, the corresponding SNSPDs on an alternative SiO2/Ta2O5

dielectric mirror showed a system detection efficiency of approximately 92% for 1550 nm

photons, and the timing jitter is around 26 ps. Our results demonstrate that the highly disordered

 films are promising for fabricating SNSPDs for near- and middle-infrared single

photons with high detection efficiency and low timing jitter.

Introduction

Superconducting nanowire single photon detectors (SNSPDs) with high system detection

efficiency, low timing jitter, low dark counts, and high counting rate have widely been applied

in broad fields for both quantum and classical realms, such as quantum optics [1-3], quantum

information processing [4-7]. Especially for telecom-wavelength photons at 1550 nm, the

SNSPDs have shown high system detection efficiency (SDE) up to 98% for both disordered

bilayer-NbN and amorphous MoSi [8,9]. In these two systems, however, the operation

temperature and maximum applicable bias current are limited due to the suppressed

superconductivity, which subsequently limits the timing performance of SNSPDs. To further

optimize the detection performance of SNSPDs, a significant improvement in intrinsic

detection performance was recently realized in the NbTiN-based SNSPDs [10-12]. By

optionally doping Ti into NbN films, it was found that a SDE of ~90% at 1550 nm with good

timing performance was realized in NbTiN-SNSPDs operated in Gifford–McMahon

cryocoolers [11].

In NbTiN films, the additional Ti atoms are also able to largely prevent the formation of vacancy

defect and thus improve the quality of crystal grains, which in turn enhances the

superconducting and electrical properties of granular NbTiN films [13,14]. As a result, NbTiN

thin films can be deposited on various substrates without intentionally heating the substrate

[15]. However, due to the introduction of Ti, the composition and structure of ternary NbTiN

compound are more complexly dependent on the deposition conditions during the sputtering

process, which makes the optimization of NbTiN thin films towards SNSPD fabrication more

complicated. Recently, it has been experimentally demonstrated that the intrinsic

detectionefficiency (IDE) of SNSPDs may related with the sheet resistance  and the residual

resistivity ratio (RRR) [16,17]. The saturation plateau of SNSPDs was found to decrease with

the decreasing  , namely, the disorder level of superconducting thin films. In highly

disordered superconducting thin films, in which the electron-electron (e-e) interaction time 

is much shorter than the electron-phonon interaction time  [18], the non-equilibrium

quasiparticles relax mainly through the e-e interaction [19-21]. Subsequently, a higher portion

of photon energy will be transferred into the electronic system instead of the phonon system,

which drives more Cooper pairs into quasiparticles and leads to a higher intrinsic quantum

efficiency [19]. Beyond the sheet resistance or disorder level of superconducting thin films, it

has also been demonstrated that the detection performance of SNSPDs was also related to the

RRR of superconducting films [17], where the saturation of  increases in films with a

lower value of RRR. As a result of  and RRR dependence of IDE, to deposit disordered

NbTiN thin films with relatively large  and low RRR would be highly suitable for SNSPD

fabrications.

Here, we investigate the superconducting properties of highly disordered  films

with different Nb content, where  is determined by atomic percentage ratio between Nb and

total metals. From the composition dependence on superconducting critical temperature 

,

, and RRR, we figured out the optimal  films for SNSPDs fabrications among

our disordered  films. We then measured intrinsic detection performance of

-SNSPDs on SiO2/Si substrate. Finally, by fabricating -SNSPDs

on an alternative SiO2/Ta2O5 dielectric mirror, a SDE up to 92% and timing jitter of 26 ps are

simultaneously obtained at a temperature of 2.4 K.

Experimental details

The  films were deposited by reactive direct-current magnetron sputtering with

elemental Nb (purity: 99.99%) and Ti (purity: 99.99%) targets in a high vacuum chamber (base

pressure ~   Pa). During the deposition, a gas mixture of 10 sccm Ar and 2 sccm N2

was simultaneously introduced to each target, corresponding to a deposition pressure around

0.25 Pa. The NbTiN films were deposited on a constant current mode. The deposition rate was

determined by a thick film (>200 nm) with relatively long deposition time. The nominal

thickness d of the resulting thin films was inferred from the predetermined deposition rate, and

confirmed by both atomic force microscope and transmission electron microscopy. To obtain

uniform NbTiN films for device fabrications, the deposition rate was kept relatively low, around

0.04 nm/s. To investigate the physical properties and photon detection performance of the

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摘要：

SinglephotondetectionperformanceofhighlydisorderedNbTiNthinfilmsRuoyanMa1,2,3,RuiShu4,XingyuZhang1,2,AoboYu1,2,3,HuangJia1,2,YouXiao1,2,3,HuiqinYu1,2,XiaoyuLiu1,2,HaoLi1,2,3,PerEklund4,XiaofuZhang1,2,3,*,LixingYou1,2,3,*1StateKeyLaboratoryofFunctionalMaterialsforInformatics,ShanghaiInstituteofMicros...

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Single photon detection performance of high ly disordered NbTiN thin films Ruoyan Ma123 Rui Shu4 Xingyu Zhang12 Aobo Yu123 Huang Jia12 You Xiao123 Huiqi n Yu12 Xiaoyu Liu12 Hao Li123 Per Eklund4 Xiaofu Zhang123 Lixing You123.pdf

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Single photon detection performance of high ly disordered NbTiN thin films Ruoyan Ma123 Rui Shu4 Xingyu Zhang12 Aobo Yu123 Huang Jia12 You Xiao123 Huiqi n Yu12 Xiaoyu Liu12 Hao Li123 Per Eklund4 Xiaofu Zhang123 Lixing You123

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