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The use of ion irradiation to control the thickness of thin superconducting films
Nuclear Inst, and Methods in Physics Research B xxx (xxxx) xxx–xxx
Contents lists available at ScienceDirect
Nuclear Inst. and Methods in Physics Research B journal homepage: www.elsevier.com/locate/nimb
The use of ion irradiation to control the thickness of thin superconducting films ⁎
B.A. Gurovicha, K.E. Prikhodkoa,b, , D.A. Komarova, M.M. Dement'evaa, L.V. Kutuzova a b
National Research Centre “Kurchatov Institute”, Kurchatov sq.1, Moscow 123182, Russia National Research Nuclear University (MEPhI), Kashirskoe sh., 31, 115409, Russia
A R T I C LE I N FO
A B S T R A C T
Keywords: Ion beam irradiation Superconductive thin films Thickness control
Low energy oxygen ion beam irradiation was used to decrease the thickness of 5 nm NbN film. It was shown that the irradiation-induced NbN oxidation thickness was controlled by the full projected range of oxygen ions. High Resolution TEM (HRTEM) images analysis and Electron Energy Loss Spectroscopy (EELS) techniques on FIB-cut cross section samples were used to monitor the process of the NbN top layer oxidation under irradiation.
1. Introduction Superconducting thin film materials are very attractive to make cryo-electronic devices with high frequency and low energy release applications [1]. The superconducting properties of thin film materials – the value of transition temperature Tc, critical current Ic and resistivity in the normal state depend on the thickness of the film [2]. Sometimes it is difficult to form areas with differing thicknesses on different parts of the plate because of the limitations of the film growing process: usually a film of uniform thickness is grown on the substrate and then the desired topology of the superconducting elements is shaped by an etching procedure. Niobium nitride has been widely studied and used for modern low-temperature superconductive devises [3] because of the high transition temperature and critical current values [4,5,6]. During last years we were developing a complex ion-irradiation based technique to make composite micro-and nanostructures for various purposes from metals, semiconductors and insulators with different chemical and physical properties. We have shown that the chemical composition and properties of materials could be controlled by means of ion beam irradiation. The technique is implemented in three ways: by selective removal of atoms (SRA) [7] – to produce metals and semiconductors from insulators; the selective displacement of atoms (SDA) – to change the atomic composition from one atom to another; and the selective association of atoms (SAA) – to produce insulators from metals and semiconductors [8]. This technique have been successfully used in different fields of nanotechnology for formation of: metal and semiconductor nanowires [9,10]; high density patterned magnetic media [11]; low temperature superconductive thin film electrical properties modification under ion ⁎
irradiation [2]. As it was shown in [12], oxygen ion beam irradiation can be used to transform 5 nm NbN to Nb2O5 up to the full film thickness without significant sputtering of the film. In the case of full thickness oxidation, it was important that the maximum projected range of oxygen ions have to be corresponded to the thickness of the film. One of the modern implementation of this technique— to tune the thickness and properties of ultrathin NbN film is the subject of this work. Because of the projected range of oxygen ions depends on the energy and may be made a few nanometers, this opens the opportunity to decrease the thickness of the original film by creating the niobium oxide at the top of the film by means of oxygen ion irradiation. 2. Materials and methods Ultrathin niobium nitride films with thickness of 5 nm were deposited by sputtering niobium target by nitrogen ions on the oxidized (∼0.15 µm amorphous SiO2) monocrystalline silicon substrate heated to a temperature of about 750 °C [12]. Thus created NbN film characterized by a high superconducting transition temperature of about (11–12) K and a critical current density of ∼5·106 A/cm2 [2]. 3. Experiment Modification of NbN films were performed by oxygen ion beam irradiation extracted from the high-frequency plasma discharge. Fig. 1 showed the ion irradiation setup. RF plasma discharge chamber was placed above the water-cooled table with the samples. Ions were extracted from the plasma by applying a negative bias voltage in the form of a pulsed square wave to the specimen table. The value of the square
Corresponding author at: National Research Centre “Kurchatov Institute”, Kurchatov sq.1, Moscow 123182, Russia. E-mail address: [email protected] (K.E. Prikhodko).
https://doi.org/10.1016/j.nimb.2018.03.023 Received 20 July 2017; Received in revised form 19 October 2017; Accepted 15 March 2018 0168-583X/ © 2018 Published by Elsevier B.V.
Please cite this article as: Gurovich, B.A., Nuclear Inst, and Methods in Physics Research B (2018), https://doi.org/10.1016/j.nimb.2018.03.023
Nuclear Inst, and Methods in Physics Research B xxx (xxxx) xxx–xxx
B.A. Gurovich et al.
Fig. 1. Irradiation setup. Fig. 2. Energy dependence of SRIM calculated values of maximum projected range (Rmax) and lateral range (Rp) for oxygen irradiation of NbN target. Horizontal line indicates the thickness of the initial NbN film.
voltage negative bias voltage was in the range from 0.1 to 1 keV to prevent sputtering of the thin film sputtering. Every negative voltage square pulse was followed by the positive voltage square pulse for extracting the electrons from the plasma discharge to minimize the charging effect during irradiation. The typical frequency of high voltage bias was about 50 kHz. The current density of the oxygen ions measured by the Faraday cup was ∼(0.1–1) mA/cm2 and corresponding ion flux ∼(0.62–6.25)* 1015 ions/cm2s. The irradiation temperature was controlled by the water cooled table in the range of ∼(20–40) °C. To check the degree of transformation of niobium nitride to niobium oxide in this work we used bright field HRTEM images in TEM mode and the low energy part of electron energy loss spectra (EELS) in transmission scanning electron microscopy (STEM) mode with lateral resolution ∼0.14 nm determined by the size of focused electron probe. For TEM end STEM analysis we used “Titan 80-300 ST” (FEI) transmission electron microscope operated at 200 kV equipped with “GIF2001” (Gatan) EELS spectrometer. The cross-section thin lamellas for TEM were cut out from the surface region of the samples after ion beam irradiation using “Helios NanoLab 650” (FEI) focused ion beam facility. We used SRIM code [13], (version 2013) in full damage cascade mode to calculate the oxygen ion propagation into NbN thin film (ρ = 8.448 g/cm3) with N = 106 incident ions to get “tails” of ion distribution carefully.
energy. It was clear from Fig. 2 that the maximum projected range of oxygen ions equals to the thickness of the NbN film at oxygen ion energy of ∼400 eV. This presents an opportunity to use low energy ions to control the remaining thickness of the niobium nitride film by ion irradiation. From this point of view, we used oxygen ions energy of 0.2 keV to demonstrate the decreasing of the thickness of NbN thin film under ion irradiation. The particular unirradiated sample plate had ∼1.7 nm of niobium oxide on the surface and the thickness of thin film of niobium nitride of ∼5.4 nm (see TEM cross-section image on Fig. 3a). Fig. 3b–e shows the set of HRTEM cross-section images of samples, irradiated up to various doses. Lines indicate the boundaries of different layers formed under oxygen ions irradiation. Fig. 4 indicates the dose dependencies of the remain niobium nitride thickness and the thickness of niobium oxide formed under ion irradiation on the top of the sample close to the surface, obtained from the data on Fig. 3a–e. It is important to note that the thickness of niobium oxide obtained from the TEM cross section bright field images did not directly reveal the radiation-induced degree of oxygen atoms replacement of nitrogen atoms but the degree of crystal to amorphous transformation under irradiation. Nevertheless, we have found that the amorphous structure formation under oxygen ions irradiation is followed by the full loss of superconductivity and insulator-like behavior of the electrical properties of the film [12]. Fig. 4 showed the saturation level of the remained NbN layer at high doses of about 2 nm. To confirm the value of remain NbN thickness, we performed the special TRIM simulation of oxygen ions propagation through NbN film taking into account the presence of thin oxide layer on the top of virgin sample (see Fig. 3a). Fig. 6 showed the calculated profile of ions distribution for this case. As we can see from Fig. 6 the experimental value of the thickness of residual NbN film corresponded to the maximum projected range (Rmax) of oxygen ions. The increasing of the thickness of oxidized layer with increasing of the dose was due to the inevitable volume changes during the displacement of the nitrogen atoms by the oxygen atoms during irradiation taking into account the atomic density difference between the niobium 3 3 nitride ( ρNbN = 0.095 at/Å ) and niobium oxide ( ρ Nb2 O5 = 0.072 at/Å ) phases. The corresponding volume changes was: VNb2 O5/ VNbN ≈ 2.32 .
4. Results and discussion As an example, Fig. 5 shows the typical calculated oxygen ions depth profile at 0.2 keV irradiation of NbN on a subsrate. The arrows indicate the calculated lateral range with straggling (Rp) and the maximum projected range (Rmax) of oxygen ions. The maximum projected range (Rmax) was defined as the maximum depth with non zero concentration of oxygen ions. The Rmax from our point of view was the most important value because it determined the ion beam induced modification depth at high irradiation dose. These calculations were performed in the range of ion energies from 0.02 to 10 keV and results are shown on Fig. 2. Fig. 2 showed that, in spite of the low values of the calculated lateral range with straggling, the maximum ion ranges were much higher. For instance, at 1 keV the lateral range of oxygen ions in NbN was 1.8 nm only, while the maximum range was 8.5 nm. The difference between lateral range with straggling and maximum range was increased with increasing of ion
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Nuclear Inst, and Methods in Physics Research B xxx (xxxx) xxx–xxx
B.A. Gurovich et al.
Fig. 3. TEM bright field cross section view of NbN thin film irradiated by oxygen ions with different doses: (a) — initial sample; (b) — 1016 cm−2; (c)— 2·1016 cm−2; (d)— 4·1016 cm−2; (e)— 2·1017 cm−2.
NbN (down) part of the film did not indicate any presence of the corresponding lines of EELS low loss signal.
Our resent TEM studies have shown that the virgin film grains contains NbN cubic phase (Fm3m ) with lattice parameter a = 0.4394 nm [14]. At the same time a high doses of oxygen irradiation lead to the formation of NbN to an amorphous niobium oxide [12]. By means of our experience in the structure study of NbN [14] and Nb2O5 [12], we paid attention to the low energy region EELS spectra, collected in STEM mode, for the residual NbN part of the film as well as the corresponding spectra for the upper oxidized part in comparing with the spectra for virgin film (Fig. 6). Fig. 6 showed the specific Nb2O5 EELS features, indicated by arrows, at the spectra of the oxidized (upper) part of irradiated film, whereas the spectra from the residual
5. Conclusions We have found that low energy oxygen ion beam irradiation can be used to decrease the thickness of NbN thin films (5 nm). The oxidation thickness of the top layer was controlled by the maximum projected range of oxygen ions. This oxidation process was confirmed by the TEM cross section images by the amorphous contrast and corresponding changes of plasmon loss EELS spectra.
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Nuclear Inst, and Methods in Physics Research B xxx (xxxx) xxx–xxx
B.A. Gurovich et al.
Fig. 6. Experimental low energy EELS spectra (plasmon loss) for unirradiated NbN sample, residual NbN layer and oxidized niobium layer. Spectra intensities were normalized by the main plasmon peak (∼23 eV).
Fig. 4. Dose dependencies of NbN residual thickness and top Nb oxide thickness under oxygen irradiation.
Acknowledgments The authors express their gratitude to Stolyarov V.L. and Olshansky E.D. for carrying out ultra-thin NbN films. References [1] I. Tretyakov, S. Ryabchun, M. Finkel, A. Maslennikova, N. Kaurova, A. Lobastova, B. Voronov, G. Gol’tsman, Appl. Phys. Lett. 98 (2011) 033507. [2] B. Gurovich, M. Tarkhov, K. Prikhodko, Nanotechnol. Russ. 9 (7–8) (2014) 386–390. [3] S. Khasminskaya, F. Pyatkov, K. Słowik, S. Ferrari, O. Kahl, V. Kovalyuk, P. Rath, A. Vetter, F. Hennrich, M. Kappes, G. Gol'tsman, A. Korneev, C. Rockstuhl, R. Krupke, W. Pernice, Nat. Photonics 10 (2016) 727–732. [4] G. Aschermann, E. Friedrich, E. Justi, J. Kramer, Phys. Z. 42 (1941) 349–360. [5] R. Warmekraft, Z. Phys. 132 (1) (1952) 446–467. [6] T. Orlando, K. Delin, Foundations of Applied Superconductivity, Prentice Hall, 1991 ISBN-13: 978-0201183238. [7] B. Gurovich, K. Prikhodko, Phys.-Usp. 52 (1) (2009) 165–178. [8] B. Gurovich, K. Prikhodko, E. Kuleshova, J. Exp. Theor. Phys. 116 (6) (2013) 916–927. [9] B. Gurovich, K. Prikhod’ko, A. Taldenkov, J. Vac. Sci. Technol. B 29 (2) (2011) 021013-1–021013-5. [10] B. Gurovich, K. Prikhod’ko, D. Komarov, A. Taldenkov, Nanotechnol. Russ. 8 (3) (2013) 199–204. [11] B. Gurovich, K. Prikhod’ko, E. Kuleshova, et al., J. Magn. Magn. Mater. 322 (2013) 3060–3063. [12] B. Gurovich, K. Prikhod’ko, M. Tarkhov, Nanotechnol. Russ. 10 (7-8) (2015) 530–536. [13] J. Ziegler, M. Ziegler, J. Biersack, SRIM – the stopping and range of ions in matter, Nucl. Instrum. Methods Phys. Res. B 2010 (268) (2010) 1818–1823. [14] K. Prikhodko, B. Gurovich, M. Dementewa, IOP Conference Series, Mater. Sci. Eng. 130 (1) (2016) 012046.
Fig. 5. SRIM code calculated oxygen ions depth distribution in the model layer sample with the structure close to the initial NbN experimental sample (included top oxidized layer). Arrow indicates the TEM experimental interface position of remain NbN crystal layer.
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Contents lists available at ScienceDirect
Nuclear Inst. and Methods in Physics Research B journal homepage: www.elsevier.com/locate/nimb
The use of ion irradiation to control the thickness of thin superconducting films ⁎
B.A. Gurovicha, K.E. Prikhodkoa,b, , D.A. Komarova, M.M. Dement'evaa, L.V. Kutuzova a b
National Research Centre “Kurchatov Institute”, Kurchatov sq.1, Moscow 123182, Russia National Research Nuclear University (MEPhI), Kashirskoe sh., 31, 115409, Russia
A R T I C LE I N FO
A B S T R A C T
Keywords: Ion beam irradiation Superconductive thin films Thickness control
Low energy oxygen ion beam irradiation was used to decrease the thickness of 5 nm NbN film. It was shown that the irradiation-induced NbN oxidation thickness was controlled by the full projected range of oxygen ions. High Resolution TEM (HRTEM) images analysis and Electron Energy Loss Spectroscopy (EELS) techniques on FIB-cut cross section samples were used to monitor the process of the NbN top layer oxidation under irradiation.
1. Introduction Superconducting thin film materials are very attractive to make cryo-electronic devices with high frequency and low energy release applications [1]. The superconducting properties of thin film materials – the value of transition temperature Tc, critical current Ic and resistivity in the normal state depend on the thickness of the film [2]. Sometimes it is difficult to form areas with differing thicknesses on different parts of the plate because of the limitations of the film growing process: usually a film of uniform thickness is grown on the substrate and then the desired topology of the superconducting elements is shaped by an etching procedure. Niobium nitride has been widely studied and used for modern low-temperature superconductive devises [3] because of the high transition temperature and critical current values [4,5,6]. During last years we were developing a complex ion-irradiation based technique to make composite micro-and nanostructures for various purposes from metals, semiconductors and insulators with different chemical and physical properties. We have shown that the chemical composition and properties of materials could be controlled by means of ion beam irradiation. The technique is implemented in three ways: by selective removal of atoms (SRA) [7] – to produce metals and semiconductors from insulators; the selective displacement of atoms (SDA) – to change the atomic composition from one atom to another; and the selective association of atoms (SAA) – to produce insulators from metals and semiconductors [8]. This technique have been successfully used in different fields of nanotechnology for formation of: metal and semiconductor nanowires [9,10]; high density patterned magnetic media [11]; low temperature superconductive thin film electrical properties modification under ion ⁎
irradiation [2]. As it was shown in [12], oxygen ion beam irradiation can be used to transform 5 nm NbN to Nb2O5 up to the full film thickness without significant sputtering of the film. In the case of full thickness oxidation, it was important that the maximum projected range of oxygen ions have to be corresponded to the thickness of the film. One of the modern implementation of this technique— to tune the thickness and properties of ultrathin NbN film is the subject of this work. Because of the projected range of oxygen ions depends on the energy and may be made a few nanometers, this opens the opportunity to decrease the thickness of the original film by creating the niobium oxide at the top of the film by means of oxygen ion irradiation. 2. Materials and methods Ultrathin niobium nitride films with thickness of 5 nm were deposited by sputtering niobium target by nitrogen ions on the oxidized (∼0.15 µm amorphous SiO2) monocrystalline silicon substrate heated to a temperature of about 750 °C [12]. Thus created NbN film characterized by a high superconducting transition temperature of about (11–12) K and a critical current density of ∼5·106 A/cm2 [2]. 3. Experiment Modification of NbN films were performed by oxygen ion beam irradiation extracted from the high-frequency plasma discharge. Fig. 1 showed the ion irradiation setup. RF plasma discharge chamber was placed above the water-cooled table with the samples. Ions were extracted from the plasma by applying a negative bias voltage in the form of a pulsed square wave to the specimen table. The value of the square
Corresponding author at: National Research Centre “Kurchatov Institute”, Kurchatov sq.1, Moscow 123182, Russia. E-mail address: [email protected] (K.E. Prikhodko).
https://doi.org/10.1016/j.nimb.2018.03.023 Received 20 July 2017; Received in revised form 19 October 2017; Accepted 15 March 2018 0168-583X/ © 2018 Published by Elsevier B.V.
Please cite this article as: Gurovich, B.A., Nuclear Inst, and Methods in Physics Research B (2018), https://doi.org/10.1016/j.nimb.2018.03.023
Nuclear Inst, and Methods in Physics Research B xxx (xxxx) xxx–xxx
B.A. Gurovich et al.
Fig. 1. Irradiation setup. Fig. 2. Energy dependence of SRIM calculated values of maximum projected range (Rmax) and lateral range (Rp) for oxygen irradiation of NbN target. Horizontal line indicates the thickness of the initial NbN film.
voltage negative bias voltage was in the range from 0.1 to 1 keV to prevent sputtering of the thin film sputtering. Every negative voltage square pulse was followed by the positive voltage square pulse for extracting the electrons from the plasma discharge to minimize the charging effect during irradiation. The typical frequency of high voltage bias was about 50 kHz. The current density of the oxygen ions measured by the Faraday cup was ∼(0.1–1) mA/cm2 and corresponding ion flux ∼(0.62–6.25)* 1015 ions/cm2s. The irradiation temperature was controlled by the water cooled table in the range of ∼(20–40) °C. To check the degree of transformation of niobium nitride to niobium oxide in this work we used bright field HRTEM images in TEM mode and the low energy part of electron energy loss spectra (EELS) in transmission scanning electron microscopy (STEM) mode with lateral resolution ∼0.14 nm determined by the size of focused electron probe. For TEM end STEM analysis we used “Titan 80-300 ST” (FEI) transmission electron microscope operated at 200 kV equipped with “GIF2001” (Gatan) EELS spectrometer. The cross-section thin lamellas for TEM were cut out from the surface region of the samples after ion beam irradiation using “Helios NanoLab 650” (FEI) focused ion beam facility. We used SRIM code [13], (version 2013) in full damage cascade mode to calculate the oxygen ion propagation into NbN thin film (ρ = 8.448 g/cm3) with N = 106 incident ions to get “tails” of ion distribution carefully.
energy. It was clear from Fig. 2 that the maximum projected range of oxygen ions equals to the thickness of the NbN film at oxygen ion energy of ∼400 eV. This presents an opportunity to use low energy ions to control the remaining thickness of the niobium nitride film by ion irradiation. From this point of view, we used oxygen ions energy of 0.2 keV to demonstrate the decreasing of the thickness of NbN thin film under ion irradiation. The particular unirradiated sample plate had ∼1.7 nm of niobium oxide on the surface and the thickness of thin film of niobium nitride of ∼5.4 nm (see TEM cross-section image on Fig. 3a). Fig. 3b–e shows the set of HRTEM cross-section images of samples, irradiated up to various doses. Lines indicate the boundaries of different layers formed under oxygen ions irradiation. Fig. 4 indicates the dose dependencies of the remain niobium nitride thickness and the thickness of niobium oxide formed under ion irradiation on the top of the sample close to the surface, obtained from the data on Fig. 3a–e. It is important to note that the thickness of niobium oxide obtained from the TEM cross section bright field images did not directly reveal the radiation-induced degree of oxygen atoms replacement of nitrogen atoms but the degree of crystal to amorphous transformation under irradiation. Nevertheless, we have found that the amorphous structure formation under oxygen ions irradiation is followed by the full loss of superconductivity and insulator-like behavior of the electrical properties of the film [12]. Fig. 4 showed the saturation level of the remained NbN layer at high doses of about 2 nm. To confirm the value of remain NbN thickness, we performed the special TRIM simulation of oxygen ions propagation through NbN film taking into account the presence of thin oxide layer on the top of virgin sample (see Fig. 3a). Fig. 6 showed the calculated profile of ions distribution for this case. As we can see from Fig. 6 the experimental value of the thickness of residual NbN film corresponded to the maximum projected range (Rmax) of oxygen ions. The increasing of the thickness of oxidized layer with increasing of the dose was due to the inevitable volume changes during the displacement of the nitrogen atoms by the oxygen atoms during irradiation taking into account the atomic density difference between the niobium 3 3 nitride ( ρNbN = 0.095 at/Å ) and niobium oxide ( ρ Nb2 O5 = 0.072 at/Å ) phases. The corresponding volume changes was: VNb2 O5/ VNbN ≈ 2.32 .
4. Results and discussion As an example, Fig. 5 shows the typical calculated oxygen ions depth profile at 0.2 keV irradiation of NbN on a subsrate. The arrows indicate the calculated lateral range with straggling (Rp) and the maximum projected range (Rmax) of oxygen ions. The maximum projected range (Rmax) was defined as the maximum depth with non zero concentration of oxygen ions. The Rmax from our point of view was the most important value because it determined the ion beam induced modification depth at high irradiation dose. These calculations were performed in the range of ion energies from 0.02 to 10 keV and results are shown on Fig. 2. Fig. 2 showed that, in spite of the low values of the calculated lateral range with straggling, the maximum ion ranges were much higher. For instance, at 1 keV the lateral range of oxygen ions in NbN was 1.8 nm only, while the maximum range was 8.5 nm. The difference between lateral range with straggling and maximum range was increased with increasing of ion
2
Nuclear Inst, and Methods in Physics Research B xxx (xxxx) xxx–xxx
B.A. Gurovich et al.
Fig. 3. TEM bright field cross section view of NbN thin film irradiated by oxygen ions with different doses: (a) — initial sample; (b) — 1016 cm−2; (c)— 2·1016 cm−2; (d)— 4·1016 cm−2; (e)— 2·1017 cm−2.
NbN (down) part of the film did not indicate any presence of the corresponding lines of EELS low loss signal.
Our resent TEM studies have shown that the virgin film grains contains NbN cubic phase (Fm3m ) with lattice parameter a = 0.4394 nm [14]. At the same time a high doses of oxygen irradiation lead to the formation of NbN to an amorphous niobium oxide [12]. By means of our experience in the structure study of NbN [14] and Nb2O5 [12], we paid attention to the low energy region EELS spectra, collected in STEM mode, for the residual NbN part of the film as well as the corresponding spectra for the upper oxidized part in comparing with the spectra for virgin film (Fig. 6). Fig. 6 showed the specific Nb2O5 EELS features, indicated by arrows, at the spectra of the oxidized (upper) part of irradiated film, whereas the spectra from the residual
5. Conclusions We have found that low energy oxygen ion beam irradiation can be used to decrease the thickness of NbN thin films (5 nm). The oxidation thickness of the top layer was controlled by the maximum projected range of oxygen ions. This oxidation process was confirmed by the TEM cross section images by the amorphous contrast and corresponding changes of plasmon loss EELS spectra.
3
Nuclear Inst, and Methods in Physics Research B xxx (xxxx) xxx–xxx
B.A. Gurovich et al.
Fig. 6. Experimental low energy EELS spectra (plasmon loss) for unirradiated NbN sample, residual NbN layer and oxidized niobium layer. Spectra intensities were normalized by the main plasmon peak (∼23 eV).
Fig. 4. Dose dependencies of NbN residual thickness and top Nb oxide thickness under oxygen irradiation.
Acknowledgments The authors express their gratitude to Stolyarov V.L. and Olshansky E.D. for carrying out ultra-thin NbN films. References [1] I. Tretyakov, S. Ryabchun, M. Finkel, A. Maslennikova, N. Kaurova, A. Lobastova, B. Voronov, G. Gol’tsman, Appl. Phys. Lett. 98 (2011) 033507. [2] B. Gurovich, M. Tarkhov, K. Prikhodko, Nanotechnol. Russ. 9 (7–8) (2014) 386–390. [3] S. Khasminskaya, F. Pyatkov, K. Słowik, S. Ferrari, O. Kahl, V. Kovalyuk, P. Rath, A. Vetter, F. Hennrich, M. Kappes, G. Gol'tsman, A. Korneev, C. Rockstuhl, R. Krupke, W. Pernice, Nat. Photonics 10 (2016) 727–732. [4] G. Aschermann, E. Friedrich, E. Justi, J. Kramer, Phys. Z. 42 (1941) 349–360. [5] R. Warmekraft, Z. Phys. 132 (1) (1952) 446–467. [6] T. Orlando, K. Delin, Foundations of Applied Superconductivity, Prentice Hall, 1991 ISBN-13: 978-0201183238. [7] B. Gurovich, K. Prikhodko, Phys.-Usp. 52 (1) (2009) 165–178. [8] B. Gurovich, K. Prikhodko, E. Kuleshova, J. Exp. Theor. Phys. 116 (6) (2013) 916–927. [9] B. Gurovich, K. Prikhod’ko, A. Taldenkov, J. Vac. Sci. Technol. B 29 (2) (2011) 021013-1–021013-5. [10] B. Gurovich, K. Prikhod’ko, D. Komarov, A. Taldenkov, Nanotechnol. Russ. 8 (3) (2013) 199–204. [11] B. Gurovich, K. Prikhod’ko, E. Kuleshova, et al., J. Magn. Magn. Mater. 322 (2013) 3060–3063. [12] B. Gurovich, K. Prikhod’ko, M. Tarkhov, Nanotechnol. Russ. 10 (7-8) (2015) 530–536. [13] J. Ziegler, M. Ziegler, J. Biersack, SRIM – the stopping and range of ions in matter, Nucl. Instrum. Methods Phys. Res. B 2010 (268) (2010) 1818–1823. [14] K. Prikhodko, B. Gurovich, M. Dementewa, IOP Conference Series, Mater. Sci. Eng. 130 (1) (2016) 012046.
Fig. 5. SRIM code calculated oxygen ions depth distribution in the model layer sample with the structure close to the initial NbN experimental sample (included top oxidized layer). Arrow indicates the TEM experimental interface position of remain NbN crystal layer.
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