Sandwich-type composite multilayer films of strontium titanate and barium strontium titanate and their controllable dielectric properties

doi:10.1016/j.jmst.2020.12.030

Abstract

Abstract:

It is a challenge to reduce the dielectric loss and increase the tunability of pure barium strontium titanate (BST) films for microwave tunable application because these two properties change simultaneously. Herein, a novel composite of strontium titanate (ST) and potassium-doped BST (KBST) has been designed as ST/KBST/ST sandwich-type film with various ST and KBST layers. X-ray diffraction patterns show that the film exhibits cubic perovskite polycrystalline structure composed of BST and ST phase, mainly grow along (110) crystal plane with average grain size of less than 20 nm and decreasing BST phase/ST phase ratio with increasing film thickness. Scanning electron microscope shows that no interfacial layer can be observed, indicating that ST and KBST are fully compounded. Low dielectric loss and high tunability at -10 - 10 V and stable and excellent dielectric properties at 1 GHz are achieved, meeting the needs of microwave tunable application at high frequency. The surface structures are also studied by other analysis methods, and ST/MgBST/ST sandwich-type film is compared.

Key words: ST/KBST/ST, Sandwich-type, Multilayer film, Controllable dielectric performance, High frequency application

Wenlong Liu, Lin Tao, Wei Feng, Jiaxuan Liao, Lingzhao Zhang. Sandwich-type composite multilayer films of strontium titanate and barium strontium titanate and their controllable dielectric properties[J]. J. Mater. Sci. Technol., 2021, 85: 245-254.

Figures/Tables 11

Fig. 1. Processes of the sandwich-type films and the film capacitors: (a) schematic diagrams of the ST/KBST/ST/…/KBST/ST and ST/MgBST/ST/…/MgBST/ST films and the film capacitors, (b) and (c) three-dimensional schematic diagrams of 3 layer-ST/KBST/ST and ST/MgBST/ST films, respectively, (d) preparation process of the films and the film capacitors including film annealing, preparation of capacitor top electrode Au and etching of the capacitors before testing, and performance testing, (e) and (f) schematic diagrams of 3 layer-ST/KBST/ST and ST/MgBST/ST films preheated at 600 °C.

Fig. 2. XRD patterns of six sandwich-type multilayer films and an internal standard substance of pure Ba0.6Sr0.4TiO3 (BST) powder, where dotted lines 1, 2 and 3 correspond to the diffraction peaks of Pt.

Fig. 3. Specific distribution of BST phase and ST phase by fitting (110) peaks.

Fig. 4. Specific distribution of BST phase and ST phase by fitting (211) peaks.

Table 1 Phase structure (PS), intensity ratio of BST phase/ST phase (IR), peak position (PP), full-width at half maximum (X), lattice parameter (LP) and average grain size (AGS) calculated by (110) and (211) peaks shown in Fig. 3. The AGS is calculated by the Scherrer formula of D = 0.9λ/(Xcosθ), where D is grain size and λ is 0.15405 nm.

Films	Parameters
Films	PS		PP (°)	X (°)	AGS (nm)	LP (Å)	IR
2ST + 1KBST	BST	(110)	31.95	0.416	19.9	3.957
	BST	(211)	56.90	0.70	12.9	3.960	2.15 (110)
	ST	(110)	32.38	0.350	23.6	3.906	2.06 (211)
	ST	(211)	57.70	0.70	13.0	3.910
3ST + 2KBST	BST	(110)	31.98	0.518	16.0	3.954
	BST	(211)	56.90	0.70	12.9	3.960	1.19 (110)
	ST	(110)	32.42	0.524	15.8	3.901	1.44 (211)
	ST	(211)	57.65	0.70	13.0	3.913
4ST + 3KBST	BST	(110)	32.12	0.465	17.8	3.937
	BST	(211)	57.10	0.50	18.1	3.948	1.38 (110) 0.92
	ST	(110)	32.44	0.455	18.2	3.899	(211)
	ST	(211)	57.80	0.44	20.6	3.904
5ST + 4KBST	BST	(110)	32.04	0.495	16.7	3.947
	BST	(211)	56.88	0.80	11.3	3.962	0.92 (110)
	ST	(110)	32.35	0.465	17.8	3.910	0.75 (211)
	ST	(211)	57.56	0.80	11.3	3.919
6ST + 5KBST	BST	(110)	31.99	0.520	15.9	3.953
	BST	(211)	57.10	0.85	10.6	3.948	0.83 (110)
	ST	(110)	32.35	0.455	18.2	3.910	0.92 (211)
	ST	(211)	57.67	0.85	10.7	3.912
4ST+3MgBST	BST	(110)	32.01	0.390	21.2	3.950
	BST	(211)	57.10	0.60	18.1	3.948	0.68 (110)
	ST	(110)	32.39	0.380	21.8	3.905	0.96 (211)
	ST	(211)	57.83	0.50	18.2	3.902

Fig. 5. (a)-(e) the AFM surface morphologies of the 2ST + 1KBST-6ST + 5KBST films, (f) the AFM surface morphology of the 4ST+3MgBST film, (g) the cross-section SEM morphology of 4ST + 3KBST film, (h) the cross-section SEM morphology of 4ST+3MgBST film, (i) EDS mapping images of Ba, Sr, Ti and O in the selected rectangle in Fig. 4(g), and (j) EDS mapping images of Ba, Sr, Ti and O in the selected rectangle in Fig. 4(h).

Fig. 6. The chemical states of (a) Sr3d, (b) Ti2p, (c) O1s and (d) C1s, where Sr3d, Ti2p or O1s are composed of three or four peaks.

Table 2 The atomic concentration on the surfaces of four films tested by XPS spectra.

XPS pattern	Sr3d (%)	Ti2p (%)	O1s (%)	C1s (%)	Sr/Ti
2ST + 1KBST	10.16	10.82	37.42	41.60	0.939
4ST + 3KBST	12.24	12.77	35.53	39.46	0.958
6ST + 5KBST	14.75	15.06	33.66	36.53	0.979
4ST+3MgBST	14.03	14.36	34.96	36.65	0.977

Table 3 Fitted peak positions (PP) of Sr3d, Ti2p, O1s and C1s peaks of 2ST + 1KBST, 4ST + 3KBST, 6ST + 5KBST and 4ST+3MgBST four films. Except C1s peak, Sr3d, Ti2p or O1s peak can be divided into three or four peaks, where the first two fitted peaks for Sr3d or Ti2p peak and the first fitted peak for O1s peak correspond to perovskite structures, and the other fitted peaks together with C1s peak correspond to non-perovskite structures. I1 shows the total intensity of perovskite structure, I2 reveals the total intensity of non-perovskite structure, and I2/(I1+I2) exhibits the ratio of non-perovskite structure.

Peaks	Films	Parameters
Peaks	Films	PP1	PP2	PP3	PP4	I₂/(I₁+I₂)
Sr3d	2ST + 1KBST	133.15	134.80	134.15	135.80	18%
	4ST + 3KBST	132.95	134.6	133.95	135.60	14%
	6ST + 5KBST	132.80	134.45	133.80	135.45	9.0%
	4ST+3MgBST	133.15	134.80	134.15	135.80	12%
Ti2p	2ST + 1KBST	458.65	464.45	457.65	463.45	17%
	4ST + 3KBST	458.50	464.30	457.50	463.30	12%
	6ST + 5KBST	458.40	464.20	457.40	463.20	8%
	4ST+3MgBST	458.80	464.60	457.80	463.60	10%
O1s	2ST + 1KBST	529.70	531.25	532.95		43 %
	4ST + 3KBST	529.65	531.20	532.90		36%
	6ST + 5KBST	529.70	531.25	532.95		28 %
	4ST+3MgBST	529.70	531.25	532.95		32%
C1s	2ST + 1KBST	284.70
	4ST + 3KBST	284.65
	6ST + 5KBST	284.50
	4ST+3MgBST	284.50

Fig. 7. Dielectric properties as functions of the applied voltages of -10 V - 10 V and the test frequency of 100 kHz.

Fig. 8. Permittivity and dielectric loss of the as-prepared films as a function of the test frequencies.

References 44

[1]	M.W. Cole, P.C. Joshi, M.H. Ervin, J. Appl. Phys. 89 (2001) 6336-6340. DOI URL
[2]	H.Z. Wang, Y.X. Dong, Z.M. Wang, J. Alloys. Compd. 745 (2018) 651-658. DOI URL
[3]	D. Popovici, M. Noda, M. Okuyama, Y. Sasaki, M. Komaru, J. Eur. Ceram. Soc. 26 (2006) 1879-1882. DOI URL
[4]	P. Bao, T.J. Jackson, X. Wang, M.J. Lancaster, J. Phys. D Appl. Phys. 41 (2008),063001. DOI URL
[5]	J.H. Leach, H. Liu, V. Avrutin, B. Xiao, Ü. Özgür, H. Morkoc¸, J. Das, Y.Y. Song, C.E. Patton, J. Appl. Phys. 107 (2010), 084511. DOI URL
[6]	J.X. Liao, X.B. Wei, Z.Q. Xu, X.B. Wei, P. Wang, Mater. Chem. Phys. 135 (2012) 1030-1035. DOI URL
[7]	Z. Song, H.X. Liu, S.J. Zhang, Z.J. Wang, Y.T. Shi, H. Hao, M.H. Cao, Z.H. Yao, Z.Y. Yu, J. Eur. Ceram. Soc. 34 (2014) 1209-1217. DOI URL
[8]	J. Xie, H. Hao, Z.H. Yao, L. Zhang, Q. Xu, H.X. Liu, M.H. Cao, Ceram. Int. 44 (2018) 5867-5873. DOI URL
[9]	Y.Z. Fan, Z.Y. Zhou, Y. Chen, W. Huang, X.L. Dong, J. Mater. Chem. C 8 (2020) 50-57. DOI URL
[10]	D.S. Yoon, J.S. Roh, S.M. Lee, H.K. Baik, Prog. Mater. Sci. 48 (2003) 275-371. DOI URL
[11]	Y. Jeong, H.J. Jin, J.H. Park, Y. Cho, M. Kim, S. Hong, W. Jo, Y. Yi, S. Im, Adv. Funct. Mater. 30 (2020), 908210.
[12]	K. Hashimoto, H. Xu, T. Mukaigawa, R. Kubo, H. Zhu, M. Noda, M. Okuyama, Sens. Actuators A 88 (2001) 10-19. DOI URL
[13]	M.W. Cole, P.C. Joshi, M.H. Ervin, M.C. Wood, R.L. Pfeffer, Thin Solid Films 374 (2000) 34-41. DOI URL
[14]	L. Xiao, K.L. Choy, I. Harrison, Surf. Coatings Technol. 205 (2011) 2989-2993. DOI URL
[15]	M.W. Cole, C.V. Weiss, E. Ngo, S. Hirsch, L.A. Coryell, S.P. Alpay, Appl. Phys. Lett. 92 (2008) 182906. DOI URL
[16]	K.H. Ahn, S. Baik, S.S. Kim, J. Appl. Phys. 92 (2002) 2651-2654. DOI URL
[17]	R.V. Wang, P.C. McIntyre, J.D. Baniecki, K. Nomura, T. Shioga, K. Kurihara, M. Ishii, Appl. Phys. Lett. 87 (2005) 192906. DOI URL
[18]	J.X. Liao, Z.Q. Xu, X.B. Wei, X.B. Wei, P. Wang, B.C. Yang, Surf. Coatings Technol. 206 (2012) 4518-4524. DOI URL
[19]	W.C. Yi, T.S. Kalkur, E. Philofsky, L. Kammerdiner, Thin Solid Films 402 (2002) 307-310. DOI URL
[20]	S. Basu, A. Verma, D.C. Agrawal, Y.N. Mohapatra, R.S. Katiyar, J. Electroceram. 19 (2007) 229-236. DOI URL
[21]	L.R. Song, Y.C. Chen, G.S. Wang, L.H. Yang, T. Li, F. Gao, X.L. Dong, Ceram. Int. l40 (2014) 12573-12577.
[22]	X.H. Sun, B.L. Zhu, T. Liu, M.Y. Li, X.Z. Zhao, D.Y. Wang, C.L. Sun, H.L.W. Chan, J. Appl. Phys. 99 (2006) 084103. DOI URL
[23]	J.Q. Huang, J.X. Liao, W.F. Zhang, S.Z. Wang, H.Y. Yang, M.Q. Wu, Integ. Ferroelectr. 162 (2015) 94-101. DOI URL
[24]	S.Z. Wang, J.X. Liao, Y.M. Hu, F. Gong, Z.Q. Xu, M.Q. Wu, Mater. Chem. Phys. 193 (2017) 50-56. DOI URL
[25]	W.L. Liu, J.X. Liao, S.Z. Wang, X.F. Huang, Y.F. Zhang, Ceram. Int. 44 (2018) 15653-15659. DOI URL
[26]	S.Z. Wang, J.X. Liao, T.T. Feng, Y.M. Hu, H.Y. Yang, M.Q. Wu, Integ. Ferroelectr. 170 (2016) 120-129. DOI URL
[27]	J.X. Liao, X.B. Wei, Z.Q. Xu, P. Wang, Vacuum 107 (2014) 291-296. DOI URL
[28]	J.Q. Huang, J.X. Liao, P. Wang, W.F. Zhang, X.B. Wei, Z.Q. Xu, Surf. Coatings Technol. 251 (2014) 307-312. DOI URL
[29]	J. Im, O. Auciello, P.K. Baumann, S.K. Streiffer, D.Y. Kaufman, A.R. Krauss, Appl. Phys. Lett. 76 (2000) 1-3. DOI URL
[30]	M. Jain, S.B. Majumder, R.S. Katiyar, D.C. Agrawal, A.S. Bhalla, Appl. Phys. Lett. 81 (2002) 1-3. DOI URL
[31]	W. Ren, S.S.T. McKinstry, C.A. Randall, T.R. Shrout, J. Appl. Phys. 89 (2001) 767-774. DOI URL
[32]	W.Y. Fu, L.Z. Cao, S.F. Wang, Z.H. Sun, B.L. Cheng, Q. Wang, H. Wang, Appl. Phys. Lett. 89 (2006) 132908. DOI URL
[33]	Z. Wang, W. Ren, X.L. Zhan, P. Shi, X.Q. Wu, J. Appl. Phys. 116 (2014) 194107. DOI URL
[34]	L.H. Yang, G.S. Wang, X.L. Dong, F. Ponchel, D. Rémiens, J. Am. Ceram. Soc. 94 (2011) 2262-2265. DOI URL
[35]	W.L. Liu, Y.F. Zhang, J.X. Liao, Z.Q. Xu, Integr. Ferroelectr. 191 (2018) 46-59. DOI URL
[36]	W.L. Liu, Y.Y. Liu, J.S. Do, IEEE Sens. J. 16 (2016) 1872-1879. DOI URL
[37]	Y. Gong, W.Y. Zhou, Z.J. Wang, L. Xu, Y.J. Kou, H.W. Cai, X.R. Liu, Q.G. Chen, Z.M. Dang, J. Mater. Sci. Technol. 34 (2018) 2415-2423. DOI
[38]	D.P. Cao, J.B. Zhang, A.C. Wang, X.H. Yu, B.X. Mi, J. Mater. Sci. Technol. 56 (2020) 189-195. DOI URL
[39]	Q.Q. Liu, J.X. Huang, H. Tang, X.H. Yu, J. Shen, J. Mater. Sci. Technol. 56 (2020) 196-205. DOI URL
[40]	J.Y. Baek, L.T. Duy, S.Y. Lee, H. Seo, J. Mater. Sci. Technol. 42 (2020) 28-37. DOI URL
[41]	D.Q. Liu, Y.X. Wang, X. Jiang, H.J. Kang, X. Yang, X.Y. Zhang, T.M. Wang, J. Mater. Sci. Technol. 52 (2020) 172-179. DOI URL
[42]	X.S. Fang, C.H. Ye, L.D. Zhang, T. Xie, Adv. Mater. 17 (2005) 1661-1665. DOI URL
[43]	J.X. Liao, C.R. Yang, J.H. Zhang, C.L. Fu, H.W. Chen, W.J. Leng, Appl. Surf. Sci. 252 (2006) 7407-7414. DOI URL
[44]	J.X. Liao, C.R. Yang, Z. Tian, H.G. Yang, L. Jin, J. Phys. D Appl. Phys. 39 (2006) 2473-2479. DOI URL