不同溅射条件对超薄外延氮化铌薄膜超导性能的影响
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摘要
氮化铌(NbN)由于其较高的超导转变温度、较窄的转变宽度以及良好的稳定性一直被广泛地应用于低温超导器件中.因此,生长高质量的超导Nb N薄膜是制备高性能薄膜超导器件的关键及难点.本文主要介绍了利用磁控溅射法在氧化镁(MgO)<100>基底上生长厚度为5 nm的超薄超导外延NbN薄膜,并系统分析了溅射参数对薄膜性能的影响.实验结果表明,在合适的氮氩比或功率下,高真空、高溅射温度、低工作气压与NbN薄膜超导转变温度成正相关.采用综合物性测量系统(physical property measurement system, PPMS)进行电学分析,所制备的NbN薄膜超导最高转变温度为12.5 K.该工作为进一步研究超薄NbN薄膜的生长提供了理论指导,也为后期在其他基底上制备NbN超导器件提供了基础.
Superconductors are used in military and commercial applications due to the full diamagnetic and zero resistance properties. Hereinto, niobium nitride(NbN) has been extensively studied for its excellent superconducting properties, such as high transition temperature(Tc), large superconducting energy gap, narrow transition width and good stability.Superconducting NbN films are widely used in low temperature superconducting devices, for instance, hot electron bolometer, superconducting quantum interference devices and rapid single flux quantum. Especially, in 2001 Gol'tsman has successfully detected a single photon response of 810 nm near-infrared using an ultra-thin superconducting NbN,which proved that the high-quality growth of ultra-thin NbN film was the key step for high resolution and sensitivity of the superconducting detector. Up to now, atomic layer deposition(ALD), molecular beam epitaxy(MBE), pulsed laser deposition(PLD) and magnetron sputtering have been successfully used to grow NbN thin films. However, Tcis decreasing gradually as the reduced of thickness. Therefore, there is still a challenge to grow ultra-thin superconducting NbN film with high performance.In this work, 5 nm thickness of superconducting epitaxial NbN film has been grown on MgO<100> substrate by magnetron sputtering. We systematically study the effect of different sputtering parameters on the superconductivity properties of the NbN film. The experiment results show that the high vacuum, high sputtering temperature and low working pressure are positively correlated with the superconducting transition temperature of NbN film under the premise of suitable argon-nitrogen ratio or magnetron power. The analyses of physical property measurement system(PPMS)indicate that as-grown 5 nm-thick NbN film has high performance with a superconducting transition temperature as high as12.5 K under the optimum condition. Morphologic characterizations show that the ultra-thin NbN films have high density and smoothness with 0.116 nm of the surface roughness. Microstructural measurements also illustrate the epitaxial growth of NbN on MgO substrate. This work demonstrates the ultra-thin NbN films can be well controllably grown with high quality and offers a platform to fabricate the ultra-thin superconducting devices in the coming future.
Superconductors are used in military and commercial applications due to the full diamagnetic and zero resistance properties. Hereinto, niobium nitride(NbN) has been extensively studied for its excellent superconducting properties, such as high transition temperature(Tc), large superconducting energy gap, narrow transition width and good stability.Superconducting NbN films are widely used in low temperature superconducting devices, for instance, hot electron bolometer, superconducting quantum interference devices and rapid single flux quantum. Especially, in 2001 Gol'tsman has successfully detected a single photon response of 810 nm near-infrared using an ultra-thin superconducting NbN,which proved that the high-quality growth of ultra-thin NbN film was the key step for high resolution and sensitivity of the superconducting detector. Up to now, atomic layer deposition(ALD), molecular beam epitaxy(MBE), pulsed laser deposition(PLD) and magnetron sputtering have been successfully used to grow NbN thin films. However, Tcis decreasing gradually as the reduced of thickness. Therefore, there is still a challenge to grow ultra-thin superconducting NbN film with high performance.In this work, 5 nm thickness of superconducting epitaxial NbN film has been grown on MgO<100> substrate by magnetron sputtering. We systematically study the effect of different sputtering parameters on the superconductivity properties of the NbN film. The experiment results show that the high vacuum, high sputtering temperature and low working pressure are positively correlated with the superconducting transition temperature of NbN film under the premise of suitable argon-nitrogen ratio or magnetron power. The analyses of physical property measurement system(PPMS)indicate that as-grown 5 nm-thick NbN film has high performance with a superconducting transition temperature as high as12.5 K under the optimum condition. Morphologic characterizations show that the ultra-thin NbN films have high density and smoothness with 0.116 nm of the surface roughness. Microstructural measurements also illustrate the epitaxial growth of NbN on MgO substrate. This work demonstrates the ultra-thin NbN films can be well controllably grown with high quality and offers a platform to fabricate the ultra-thin superconducting devices in the coming future.
引文
1 Shurakov A,Lobanov Y,Goltsman G.Superconducting hot-electron bolometer:From the discovery of hot-electron phenomena to practical applications.Supercond Sci Technol,2016,29:023001
2 Han S,Yu Y,Chu X,et al.Time-resolved measurement of dissipation-induced decoherence in a Josephson junction.Science,2001,293:1457-1459
3 Kang L,Wu P H,Sh J R,et al.Fabrication and characterization of NbN,AlN and NbN/AlN/NbN on MgO substrates.Supercond Sci Technol,2003,16:1417-1421
4 Liu Q S,Wang H W,Zhang Q Y,et al.All-NbN DC-SQUID magnetometer based on NbN/AlN/NbN Josephson junctions.IEEE Trans Appl Supercon,2017,27:1600204
5 Gol’tsman G N,Okunev O,Chulkova G,et al.Picosecond superconducting single-photon optical detector.Appl Phys Lett,2001,79:705-707
6 Kang L,Jin B B,Liu X Y,et al.Suppression of superconductivity in epitaxial NbN ultrathin films.J Appl Phys,2011,109:033908
7 Nagai M,Nakauchi R,Ono Y,et al.CVD preparation of alumina-supported niobium nitride and its activity for thiophene hydrodesulfurization.Catal Today,2000,57:297-304
8 Zou G,Jain M,Zhou H,et al.Ultrathin epitaxial superconducting niobium nitride films grown by a chemical solution technique.Chem Commun,2008,8:6022-6024
9 Zhang W J,Li H,You L X,et al.Superconducting nanowire single-photon detector with a system detection efficiency over 80%at 940-nm Wavelength.IEEE Photom J,2016,8:4500908
10 Chang H W,Wang C L,Huang Y R,et al.Growth and characterization of few unit-cell NbN superconducting films on 3C-SiC/Si substrate.Supercond Sci Technol,2017,30:115010
11 Marsili F,Gaggero A,Li L H,et al.High quality superconducting NbN thin films on GaAs.Supercond Sci Technol,2009,22:095013
12 Saraswat G,Gupta P,Bhattacharya A,et al.Highly oriented,free-standing,superconducting NbN films growth on chemical vapor deposited graphene.APL Mater,2014,2:056103
13 Semenov A,Günther B,B?ttger U,et al.Optical and transport properties of ultrathin NbN films and nanostructures.Phys Rev B,2009,80:054510
14 Zhang L,Yan X,Jiang C,et al.SNSPDs on a magnesium fluoride substrate for high system efficiency and ultra-wide band.IEEE Photon Technol Lett,2016,28:2522-2525
15 Shiino T,Shiba S,Sakai N,et al.Improvement of the critical temperature of superconducting NbTiN and NbN thin films using the AlN buffer layer.Supercond Sci Technol,2010,23:045004
16 Krause S,Meledin D,Desmaris V,et al.Epitaxial growth of ultra-thin NbN films on AlxGa1-xN buffer-layers.Supercond Sci Technol,2014,27:065009
17 Gao B,Xiao X,Su J,et al.Synthesis of mesoporous niobium nitride nanobelt arrays and their capacitive properties.Appl Surf Sci,2016,383:57-63
18 Cui H,Zhu G,Liu X,et al.Niobium nitride Nb4N5as a new high-performance electrode material for supercapacitors.Adv Sci,2015,2:1500126
19 Ivashchenko V I,Scrynskyy P L,Lytvyn O S,et al.Investigation of NbN and Nb-Si-N coatings deposited by magnetron sputtering.Acta Phys Pol A,2015,128:949-953
20 Du N,Hao L,Liu X P,et al.Effect of nitrogen to argon ratio on microstructure and optical properties of AlNxfilms(in Chinese).Acta Energ Sol Sin,2011,32:1710-1713[杜淼,郝雷,刘晓鹏,等.氮氩比对AlNx薄膜微观结构与光学性质的影响.太阳能学报,2011,32:1710-1713]
21 Wang B,Wei S C,Wang Y J,et al.Research progress in preparation of titanium dioxide thin films by magnetron sputtering(in Chinese).Surface Technol,2018,47:257-269[王博,魏世丞,王玉江,等.磁控溅射技术制备二氧化钛薄膜研究进展.表面技术,2018,47:257-264]
22 Shi X W,Song K L,Cui L B,et al.Effect of temperature on optical properties of magnetron sputtered titanium nitride films(in Chinese).Vacuum,2013,50:18-21[史新伟,宋开兰,崔立斌,等.温度对磁控溅射氮化钛薄膜光学性能的影响.真空,2013,50:18-21]
23 Tao L C,Fan Z J,Liu Y,et al.Effect of magnetron sputtering parameter variation on superconducting characteristics of bismuth film(in Chinese).China Electric Power Educat,2011,15:179-180[陶兰初,樊振军,刘育,等.磁控溅射参数变化对铌膜超导特性的影响.中国电力教育,2011,15:179-180]
24 Cao D F,Wan X B,Xing P F,et al.Effect of working pressure on DC magnetron sputtering Mo film(in Chinese).Surface Technol,2013,42:71-74[曹德峰,万小波,邢丕峰,等.工作气压对直流磁控溅射Mo薄膜的影响.表面技术,2013,42:71-74]
25 Wang D Q,Yang F S,Xu X P,et al.Study on Nitrogen-argon gas flow ratio of magnetron sputtering silicon-based AlN thin films(in Chinese).Piezoelectr Acoustoopt,2011,33:248-250[王代强,杨发顺,徐希嫔,等.磁控溅射硅基AlN薄膜的氮-氩气体流量比研究.压电与声光,2011,33:248-250]
26 Zhang J J,Su X,Zhang L,et al.Improvement of the superconducting properties of NbN thin film on single-crystal silicon substrate by using a TiNbuffer layer.Supercond Sci Technol,2013,26:045010
27 Kelly P J,Arnell R D.Magnetron sputtering:A review of recent developments and applications.Vacuum,2000,56:159-172
2 Han S,Yu Y,Chu X,et al.Time-resolved measurement of dissipation-induced decoherence in a Josephson junction.Science,2001,293:1457-1459
3 Kang L,Wu P H,Sh J R,et al.Fabrication and characterization of NbN,AlN and NbN/AlN/NbN on MgO substrates.Supercond Sci Technol,2003,16:1417-1421
4 Liu Q S,Wang H W,Zhang Q Y,et al.All-NbN DC-SQUID magnetometer based on NbN/AlN/NbN Josephson junctions.IEEE Trans Appl Supercon,2017,27:1600204
5 Gol’tsman G N,Okunev O,Chulkova G,et al.Picosecond superconducting single-photon optical detector.Appl Phys Lett,2001,79:705-707
6 Kang L,Jin B B,Liu X Y,et al.Suppression of superconductivity in epitaxial NbN ultrathin films.J Appl Phys,2011,109:033908
7 Nagai M,Nakauchi R,Ono Y,et al.CVD preparation of alumina-supported niobium nitride and its activity for thiophene hydrodesulfurization.Catal Today,2000,57:297-304
8 Zou G,Jain M,Zhou H,et al.Ultrathin epitaxial superconducting niobium nitride films grown by a chemical solution technique.Chem Commun,2008,8:6022-6024
9 Zhang W J,Li H,You L X,et al.Superconducting nanowire single-photon detector with a system detection efficiency over 80%at 940-nm Wavelength.IEEE Photom J,2016,8:4500908
10 Chang H W,Wang C L,Huang Y R,et al.Growth and characterization of few unit-cell NbN superconducting films on 3C-SiC/Si substrate.Supercond Sci Technol,2017,30:115010
11 Marsili F,Gaggero A,Li L H,et al.High quality superconducting NbN thin films on GaAs.Supercond Sci Technol,2009,22:095013
12 Saraswat G,Gupta P,Bhattacharya A,et al.Highly oriented,free-standing,superconducting NbN films growth on chemical vapor deposited graphene.APL Mater,2014,2:056103
13 Semenov A,Günther B,B?ttger U,et al.Optical and transport properties of ultrathin NbN films and nanostructures.Phys Rev B,2009,80:054510
14 Zhang L,Yan X,Jiang C,et al.SNSPDs on a magnesium fluoride substrate for high system efficiency and ultra-wide band.IEEE Photon Technol Lett,2016,28:2522-2525
15 Shiino T,Shiba S,Sakai N,et al.Improvement of the critical temperature of superconducting NbTiN and NbN thin films using the AlN buffer layer.Supercond Sci Technol,2010,23:045004
16 Krause S,Meledin D,Desmaris V,et al.Epitaxial growth of ultra-thin NbN films on AlxGa1-xN buffer-layers.Supercond Sci Technol,2014,27:065009
17 Gao B,Xiao X,Su J,et al.Synthesis of mesoporous niobium nitride nanobelt arrays and their capacitive properties.Appl Surf Sci,2016,383:57-63
18 Cui H,Zhu G,Liu X,et al.Niobium nitride Nb4N5as a new high-performance electrode material for supercapacitors.Adv Sci,2015,2:1500126
19 Ivashchenko V I,Scrynskyy P L,Lytvyn O S,et al.Investigation of NbN and Nb-Si-N coatings deposited by magnetron sputtering.Acta Phys Pol A,2015,128:949-953
20 Du N,Hao L,Liu X P,et al.Effect of nitrogen to argon ratio on microstructure and optical properties of AlNxfilms(in Chinese).Acta Energ Sol Sin,2011,32:1710-1713[杜淼,郝雷,刘晓鹏,等.氮氩比对AlNx薄膜微观结构与光学性质的影响.太阳能学报,2011,32:1710-1713]
21 Wang B,Wei S C,Wang Y J,et al.Research progress in preparation of titanium dioxide thin films by magnetron sputtering(in Chinese).Surface Technol,2018,47:257-269[王博,魏世丞,王玉江,等.磁控溅射技术制备二氧化钛薄膜研究进展.表面技术,2018,47:257-264]
22 Shi X W,Song K L,Cui L B,et al.Effect of temperature on optical properties of magnetron sputtered titanium nitride films(in Chinese).Vacuum,2013,50:18-21[史新伟,宋开兰,崔立斌,等.温度对磁控溅射氮化钛薄膜光学性能的影响.真空,2013,50:18-21]
23 Tao L C,Fan Z J,Liu Y,et al.Effect of magnetron sputtering parameter variation on superconducting characteristics of bismuth film(in Chinese).China Electric Power Educat,2011,15:179-180[陶兰初,樊振军,刘育,等.磁控溅射参数变化对铌膜超导特性的影响.中国电力教育,2011,15:179-180]
24 Cao D F,Wan X B,Xing P F,et al.Effect of working pressure on DC magnetron sputtering Mo film(in Chinese).Surface Technol,2013,42:71-74[曹德峰,万小波,邢丕峰,等.工作气压对直流磁控溅射Mo薄膜的影响.表面技术,2013,42:71-74]
25 Wang D Q,Yang F S,Xu X P,et al.Study on Nitrogen-argon gas flow ratio of magnetron sputtering silicon-based AlN thin films(in Chinese).Piezoelectr Acoustoopt,2011,33:248-250[王代强,杨发顺,徐希嫔,等.磁控溅射硅基AlN薄膜的氮-氩气体流量比研究.压电与声光,2011,33:248-250]
26 Zhang J J,Su X,Zhang L,et al.Improvement of the superconducting properties of NbN thin film on single-crystal silicon substrate by using a TiNbuffer layer.Supercond Sci Technol,2013,26:045010
27 Kelly P J,Arnell R D.Magnetron sputtering:A review of recent developments and applications.Vacuum,2000,56:159-172