Soft-mode hardening in SrTiO3 thin films

被引:249
作者
Sirenko, AA [1 ]
Bernhard, C
Golnik, A
Clark, AM
Hao, JH
Si, WD
Xi, XX
机构
[1] Penn State Univ, Dept Phys, University Pk, PA 16802 USA
[2] Max Planck Inst Festkorperforsch, D-70569 Stuttgart, Germany
关键词
D O I
10.1038/35006023
中图分类号
O [数理科学和化学]; P [天文学、地球科学]; Q [生物科学]; N [自然科学总论];
学科分类号
07 ; 0710 ; 09 ;
摘要
Understanding the behaviour of the dielectric constant in ferroelectric thin films remains a challenging problem, These ferroelectric materials have high static dielectric constants, and so are important for their applications in high-storage-density capacitor structures such as dynamic random access memory (DRAM)(1), But the dielectric constant tends to be significantly reduced in thin films, thereby limiting the potential benefit of ferroelectrics for memory devices(2). Extensive studies have shown that this phenomenon could be caused by a 'dead layer' of very low dielectric constant between the ferroelectric film and the electrode(2,3). And, although very few direct measurements are in fact available, it has been recognized that the lattice dynamical properties in the thin films should also play a key role in the reduction(2) of the dielectric constant. Here we report far-infrared ellipsometry and low-frequency dielectric measurements in SrTiO3 thin films, which demonstrate that the Lyddane-Sachs-Teller relation between the optical-phonon eigenfrequencies and the dielectric constant is fully maintained, as is the case in the bulk material. This indicates that the dramatic reduction of the dielectric constant is a consequence of a profound change of the lattice dynamical properties, in particular of the reduced softening of its lowest optical-phonon mode. Our results therefore provide a better understanding of the fundamental limitations of the dielectric constant values in ferroelectric thin films.
引用
收藏
页码:373 / 376
页数:4
相关论文
共 22 条
[1]  
AKIMOV IA, UNPUB PHYS REV LETT
[2]   The dielectric response as a function of temperature and film thickness of fiber-textured (Ba,Sr)TiO3 thin films grown by chemical vapor deposition [J].
Basceri, C ;
Streiffer, SK ;
Kingon, AI ;
Waser, R .
JOURNAL OF APPLIED PHYSICS, 1997, 82 (05) :2497-2504
[3]   INFRARED ABSORPTION AT LONGITUDINAL OPTIC FREQUENCY IN CUBIC CRYSTAL FILMS [J].
BERREMAN, DW .
PHYSICAL REVIEW, 1963, 130 (06) :2193-&
[4]   Electric-field penetration into metals: Consequences for high-dielectric-constant capacitors [J].
Black, CT ;
Welser, JJ .
IEEE TRANSACTIONS ON ELECTRON DEVICES, 1999, 46 (04) :776-780
[5]   CRYSTAL STABILITY AND THE THEORY OF FERROELECTRICITY [J].
COCHRAN, W .
ADVANCES IN PHYSICS, 1960, 9 (36) :387-423
[6]   Far-infrared spectroscopy of a SrTiO3 thin film [J].
Fedorov, I ;
Zelezny, V ;
Petzelt, J ;
Trepakov, V ;
Jelinek, M ;
Trtik, V ;
Cernansky, M ;
Studnicka, V .
FERROELECTRICS, 1998, 208 (1-4) :413-427
[7]   Grain-size effect on structure and phase transformations for barium titanate [J].
Frey, MH ;
Payne, DA .
PHYSICAL REVIEW B, 1996, 54 (05) :3158-3168
[8]   High dielectric constant and tunability of epitaxial SrTiO3 thin film capacitors [J].
Fuchs, D ;
Schneider, CW ;
Schneider, R ;
Rietschel, H .
JOURNAL OF APPLIED PHYSICS, 1999, 85 (10) :7362-7369
[9]   Far infrared ellipsometry using synchrotron radiation:: the out-of-plane response of La2-xSrxCuO4 [J].
Henn, R ;
Bernhard, C ;
Wittlin, A ;
Cardona, M ;
Uchida, S .
THIN SOLID FILMS, 1998, 313 :642-648
[10]   Non-fermi-liquid behavior of SrRuO3:: Evidence from infrared conductivity [J].
Kostic, P ;
Okada, Y ;
Collins, NC ;
Schlesinger, Z ;
Reiner, JW ;
Klein, L ;
Kapitulnik, A ;
Geballe, TH ;
Beasley, MR .
PHYSICAL REVIEW LETTERS, 1998, 81 (12) :2498-2501