Lithuanian Journal of Physics article / Lietuvos fizikos žurnalo straipsnis

STRAIN ENGINEERING OF ELECTRICAL CONDUCTIVITY IN EPITAXIAL THIN Ba_0.7Sr_0.3TiO₃ FILM HETEROSTRUCTURES
Rūta Mackevičiūtė^a, Šarūnas Bagdzevičius^a, Maksim Ivanov^a, Barbara Fraygola^b, Robertas Grigalaitis^a, Nava Setter^b, and Jūras Banys^a
^aFaculty of Physics, Vilnius University, Saulėtekio 9, LT-10222 Vilnius, Lithuania
^bCeramics Laboratory, Swiss Federal Institute of Technology (EPFL), CH-1015 Lausanne, Switzerland
E-mail: ruta.mackeviciute@ff.vu.lt

Received 5 February 2016; revised 1 March 2016; accepted 21 June 2016

Thin epitaxial films have a great potential to be used in real life applications, such as oxide-on-silicon. However, they often contain a large amount of defects, leading to an enhanced electrical conductivity. This could be desirable in some applications (i. e. memristors), but the mechanism is not fully understood. Here we report on the investigation of epitaxial barium strontium titanate thin films deposited on strontium titanate single crystal substrates (Ba_0.7Sr_0.3TiO₃/SrRuO₃//SrTiO₃ heterostructures) with a controlled epitaxial strain. The impedance analysis allowed us to propose a model, which explains changes in the temperature dependence of the conductivity based on the strain-dependent anisotropic change of electron/hole mobility.

Keywords: thin films, impedance spectroscopy, electron mobility, ferroelectrics
PACS: 77.55.-g, 84.37.+g, 73.50.Gr, 77.80.B-

ĮTEMPIAIS VALDOMAS ELEKTRINIS LAIDUMAS EPITAKSINĖSE Ba_0,7Sr_0,3TiO₃ PLONŲJŲ SLUOKSNIŲ HETEROSTRUKTŪROSE

Rūta Mackevičiūtė^a, Šarūnas Bagdzevičius^a, Maksim Ivanov^a, Barbara Fraygola^b, Robertas Grigalaitis^a, Nava Setter^b, Jūras Banys^a
^aVilniaus universiteto Kietojo kūno elektronikos katedra, Vilnius, Lietuva
^bŠveicarijos federalinis technologijos institutas (EPFL), Lozana, Šveicarija

Plonieji epitaksiniai sluoksniai yra patrauklūs įvairiems komerciniams taikymams, pavyzdžiui, silicio lustams su integruotomis oksidų heterostruktūromis. Deja, defektų koncentracija juose dažniausiai būna didelė, o tokie sluoksniai – elektriškai laidūs. Tai gali būti naudinga kai kuriems taikymams (pvz., memristoriuose), tačiau pats laidumo mechanizmas nėra iki galo suprastas. Straipsnyje pateikiame epitaksinių plonųjų bario stroncio titanato sluoksnių ant kristalinio stroncio titanato padėklo (Ba_0.7Sr_0.3TiO₃/SrRuO₃//SrTiO₃ heterostruktūros) tyrimus kontroliuojant epitaksinius įtempimus. Remiantis elektrinės pilnutinės varžos analize, pateiktas teorinis modelis, paaiškinantis temperatūrinę elektrinio laidumo elgseną įtempimų sukeltu anizotropiniu elektronų / skylių judrio kitimu.

References / Nuorodos

[1] A.I. Kingon, J.-P. Maria, and S.K. Streiffer, Alternative dielectrics to silicon dioxide for memory and logic devices, Nature 406(6799), 1032–1038 (2000),
http://dx.doi.org/10.1038/35023243
[2] H. Zhu, J. Miao, M. Noda, and M. Okuyama, Preparation of BST ferroelectric thin film by metal organic decomposition for infrared sensor, Sensors Actuators A Phys. 110(1–3), 371–377 (2004),
http://dx.doi.org/10.1016/j.sna.2003.10.074
[3] M. Jain, S.B. Majumder, R.S. Katiyar, and A.S. Bhalla, Novel barium strontium titanate Ba_0.5Sr_0.5TiO₃/MgO thin film composites for tunable microwave devices, Mater. Lett. 57(26–27), 4232–4236 (2003),
http://dx.doi.org/10.1016/S0167-577X(03)00296-9
[4] S. Agarwal, G.L. Sharma, and R. Manchanda, Electrical conduction in (Ba, Sr)TiO₃ thin film MIS capacitor under humid conditions, Solid State Commun. 119(12), 681–686 (2001),
http://dx.doi.org/10.1016/S0038-1098(01)00284-8
[5] S. Agarwal and G.L. Sharma, Humidity sensing properties of (Ba, Sr) TiO₃ thin films grown by hydrothermal–electrochemical method, Sensors Actuators B Chem. 85(3), 205–211 (2002),
http://dx.doi.org/10.1016/S0925-4005(02)00109-0
[6] W. Zhu, O.K. Tan, Q. Yan, and J.T. Oh, Microstructure and hydrogen gas sensitivity of amorphous (Ba, Sr)TiO₃ thin film sensors, Sensors Actuators B Chem. 65(1–3), 366–370 (2000),
http://dx.doi.org/10.1016/S0925-4005(99)00402-5
[7] F. Jona and G. Shirane, Ferroelectric Crystals (Dover Publications, New York, 1993),
https://www.amazon.co.uk/Ferroelectric-Crystals-F-Jona/dp/0486673863/
[8] L. Benguigui, Disordered ferroelectrics: Ba_xSr_1–xTiO₃ single crystals, Phys. Status Solidi A 46(1), 337–342 (1978),
http://dx.doi.org/10.1002/pssa.2210460144
[9] V.B. Shirokov, V.I. Torgashev, A.A. Bakirov, and V.V. Lemanov, Concentration phase diagram of Ba_xSr_1–xTiO₃ solid solutions, Phys. Rev. B 73(10), 104116 (2006),
http://dx.doi.org/10.1103/PhysRevB.73.104116
[10] V.V. Lemanov, E.P. Smirnova, P.P. Syrnikov, and E.A. Tarakanov, Phase transitions and glasslike behavior in Sr_1–xBa_xTiO₃, Phys. Rev. B 54(5), 3151–3157 (1996),
http://dx.doi.org/10.1103/PhysRevB.54.3151
[11] C. Ménoret, J.M. Kiat, B. Dkhil, M. Dunlop, H. Dammak, and O. Hernandez, Structural evolution and polar order in Sr_1–xBa_xTiO₃, Phys. Rev. B 65(22), 224104 (2002),
http://dx.doi.org/10.1103/PhysRevB.65.224104
[12] E.P. Smirnova, A.V. Sotnikov, R. Kunze, M. Weihnacht, O.E. Kvyatkovskii, and V.V. Lemanov, Interrelation of antiferrodistortive and ferroelectric phase transitions in Sr_1–xA_xTiO₃ (A=Ba, Pb), Solid State Commun. 133(7), 421–425 (2005),
http://dx.doi.org/10.1016/j.ssc.2004.12.016
[13] Z.-G. Ban and S.P. Alpay, Phase diagrams and dielectric response of epitaxial barium strontium titanate films: A theoretical analysis, J. Appl. Phys. 91(11), 9288–9296 (2002),
http://dx.doi.org/10.1063/1.1473675
[14] W. Känzig, Space charge layer near the surface of a ferroelectric, Phys. Rev. 98(2), 549–550 (1955),
http://dx.doi.org/10.1103/PhysRev.98.549
[15] I. Grinberg, D.V. West, M. Torres, G. Gou, D.M. Stein, L. Wu, G. Chen, E.M. Gallo, A.R. Akbashev, P.K. Davies, J.E. Spanier, and A.M. Rappe, Perovskite oxides for visible-light-absorbing ferroelectric and photovoltaic materials, Nature 503(7477), 509–512 (2013),
http://dx.doi.org/10.1038/nature12622
[16] P. Papet, J.P. Dougherty, and T.R. Shrout, Particle and grain size effects on the dielectric behavior of the relaxor ferroelectric Pb(Mg_1/3Nb_2/3)O₃, J. Mater. Res. 5(12), 2902–2909 (1990),
http://dx.doi.org/10.1557/JMR.1990.2902
[17] M.H. Frey, Z. Xu, P. Han, and D.A. Payne, The role of interfaces on an apparent grain size effect on the dielectric properties for ferroelectric barium titanate ceramics, Ferroelectrics 206(1), 337–353 (1998),
http://dx.doi.org/10.1080/00150199808009168
[18] H.L. Tuller and S.R. Bishop, Point defects in oxides: tailoring materials through defect engineering, Annu. Rev. Mater. Res. 41(1), 369–398 (2011),
http://dx.doi.org/10.1146/annurev-matsci-062910-100442
[19] R.A. De Souza, V. Metlenko, D. Park, and T.E. Weirich, Behavior of oxygen vacancies in single-crystal SrTiO₃: Equilibrium distribution and diffusion kinetics, Phys. Rev. B 85(17), 174109 (2012),
http://dx.doi.org/10.1103/PhysRevB.85.174109
[20] R. Meyer, R. Waser, J. Helmbold, and G. Borchardt, Observation of vacancy defect migration in the cation sublattice of complex oxides by ¹⁸O tracer experiments, Phys. Rev. Lett. 90(10), 105901 (2003),
http://dx.doi.org/10.1103/PhysRevLett.90.105901
[21] R. Waser, T. Baiatu, and K.-H. Härdtl, DC electrical degradation of perovskite-type titanates: I, ceramics, J. Am. Ceram. Soc. 73(6), 1645–1653 (1990),
http://dx.doi.org/10.1111/j.1151-2916.1990.tb09809.x
[22] M. Morozov, D. Damjanovic, and N. Setter, The nonlinearity and subswitching hysteresis in hard and soft PZT, J. Eur. Ceram. Soc. 25(12), 2483–2486 (2005),
http://dx.doi.org/10.1016/j.jeurceramsoc.2005.03.086
[23] K. Carl and K.H. Hardtl, Electrical after-effects in Pb(Ti, Zr)O₃ ceramics, Ferroelectrics 17(1), 473–486 (1977),
http://dx.doi.org/10.1080/00150197808236770
[24] M. Grossmann, S. Hoffmann, S. Gusowski, R. Waser, S.K. Streiffer, C. Basceri, C.B. Parker, S.E. Lash, and A.I. Kingon, Resistance degradation behavior of Ba_0.7Sr_0.3TiO₃ thin films compared to mechanisms found in titanate ceramics and single crystals, Integr. Ferroelectr. 22(1–4), 83–94 (1998),
http://dx.doi.org/10.1080/10584589808208032
[25] W.L. Warren, D. Dimos, G.E. Pike, B.A. Tuttle, M.V. Raymond, R. Ramesh, and J.T. Evans Jr., Voltage shifts and imprint in ferroelectric capacitors, Appl. Phys. Lett. 67(6), 866–868 (1995),
http://dx.doi.org/10.1063/1.115531
[26] G. Koster, B.L. Kropman, G.J.H.M. Rijnders, D.H.A. Blank, and H. Rogalla, Quasi-ideal strontium titanate crystal surfaces through formation of strontium hydroxide, Appl. Phys. Lett. 73(20), 2920–2922 (1998),
http://dx.doi.org/10.1063/1.122630
[27] B.J. Rodriguez, C. Callahan, S.V. Kalinin, and R. Proksch, Dual-frequency resonance-tracking atomic force microscopy, Nanotechnology 18(47), 475504 (2007),
http://dx.doi.org/10.1088/0957-4484/18/47/475504
[28] S. Havriliak and S. Negami, A complex plane analysis of α-dispersions in some polymer systems, J. Polym. Sci. Polymer Sci. Part C 14(1), 99–117 (1966),
http://dx.doi.org/10.1002/polc.5070140111
[29] Z. Zhao, V. Buscaglia, M. Viviani, M.T. Buscaglia, L. Mitoseriu, A. Testino, M. Nygren, M. Johnsson, and P. Nanni, Grain-size effects on the ferroelectric behavior of dense nanocrystalline BaTiO₃ ceramics, Phys. Rev. B 70(2), 024107 (2004),
http://dx.doi.org/10.1103/PhysRevB.70.024107
[30] J.W. Matthews and A.E. Blakeslee, Defects in epitaxial multilayers: I. Misfit dislocations, J. Cryst. Growth 27, 118–125 (1974),
http://dx.doi.org/10.1016/S0022-0248(74)80055-2
[31] J.Q. He, E. Vasco, C.L. Jia, R. Dittmann, and R.H. Wang, Microstructure of epitaxial Ba_0.7Sr_0.3TiO₃∕SrRuO₃ bilayer films on SrTiO₃ substrates, J. Appl. Phys. 97(10), 104907 (2005),
http://dx.doi.org/10.1063/1.1897067
[32] Y. Fan, S. Yu, R. Sun, L. Li, Y. Yin, K.-W. Wong, and R. Du, Microstructure and electrical properties of Mn-doped barium strontium titanate thin films prepared on copper foils, Appl. Surf. Sci. 256(22), 6531–6535 (2010),
http://dx.doi.org/10.1016/j.apsusc.2010.04.042
[33] P.-E. Janolin, A.S. Anokhin, Z. Gui, V.M. Mukhortov, Y.I. Golovko, N. Guiblin, S. Ravy, M.E. Marssi, Y.I. Yuzyuk, L. Bellaiche, and B. Dkhil, Strain engineering of perovskite thin films using a single substrate, J. Phys. Condens. Matter 26(29), 292201 (2014),
http://dx.doi.org/10.1088/0953-8984/26/29/292201