Effect of the thermal expansion matching on the dielectric tunability of (100)-one-axis-oriented (Ba0.5Sr0.5)TiO3 thin films

Abstract

The impact of the residual strain induced by the thermal strain on the dielectric tunability was systematically studied for rf sputtered ͑100͒-one-axis-oriented polycrystalline ͑Ba 0.5 Sr 0.5 ͒TiO 3 films. These films were grown on various substrates with different thermal expansion coefficients ͓␣ ͑sub͒ ͔ covered with a stack of ͑100͒ c SrRuO 3 / ͑100͒ c LaNiO 3 / ͑111͒Pt layers. The residual strain was ascertained to linearly increase with the increase in ␣ ͑sub͒ by enhancement of the surface-normal lattice spacing of ͑Ba 0.5 Sr 0.5 ͒TiO 3 and Pt. Dielectric tunability of the films also linearly increased with the increase in ␣ ͑sub͒. These results clearly demonstrate that dielectric tunability tailoring of the ͑Ba 0.5 Sr 0.5 ͒TiO 3 films can be achieved by using residual thermal strain.

Stress engineering of the alkoxide derived ferroelectric thin film on Si wafer

“…Ito et al reported that the dielectric constant of BaTiO3 thin film increased concomitantly with increasing compressive thermal stress. 8) Therefore, the tendency shown here is a very reasonable result. Figure 10 portrays the change in the reciprocal of the dielectric constant at 1 kHz as a function of the residual stress.…”

“…For example, Ito et al reported that large compressive residual stress engenders increased dielectric properties and increased tunability. 8) Ong et al reported that the tensile residual stress decreases the piezoelectric property. 9) Therefore, control of the residual stress in thin films is an important research field to obtain ferroelectric thin films with high electrical properties.…”

Fabrication and Characterization of a (100) Three‐Axis‐Oriented Single‐Crystal (Ba0.7Sr0.3)TiO3 Thin Film Prepared by the Chemical Solution Deposition Method

“…BST thin films have been fabricated by various techniques such as rf sputtering, 2 pulsed laser deposition, 3,4 metal-organic chemical vapor deposition (MOCVD), 5 and chemical solution deposition (CSD). 6,7 Among these methods, the CSD method has an edge over the other deposition techniques in terms of achieving good homogeneity, chemical composition control, high purity, low-processing temperature, and applicability to large substrate areas, using simple and inexpensive equipment.…”

Combined effects of thickness, grain size and residual stress on the dielectric properties of Ba0.5Sr0.5TiO3 thin films

“…These stresses have an important influence on the behavior of ferroelectrics-based films and can cause the stabilization of ferroelectricity, i.e., an upward shift of the Curie temperature [29], induced ferroelectricity in SrTiO 3 [30] and KTaO 3 [31] incipient ferroelectrics, the orientation of the spontaneous polarization in certain directions [32], the modification of the domain state and the mobility of domain walls [19] and the stabilization of the phases with a preferred size of the cell in systems with the proximity of thermodynamically stable phases [33,34], i.e., morphotropic phase boundaries and polymorphic phase transitions. The exact influence depends on the sign of the stress (tensile or compressive) and its magnitude [20,22,23]. As a consequence, the piezoelectric, dielectric and ferroelectric properties of the films are greatly modified [33,34,35].…”

“…However, their functional response can be significantly different from their bulk counterparts. The main factors that modify the functional response of polycrystalline thin films include the interaction with the electrodes (i.e., the electrode effect [4]), porosity [5], chemical homogeneity [6,7], texture [8][9][10] grain size and film thickness [11][12][13][14][15][16][17][18] as well as interactions with the substrates causing residual stresses [19][20][21][22][23]. These complex phenomena occur across various length scales and are still not completely understood [24,25].…”