Depletion layer thickness and Schottky type carrier injection at the interface between Pt electrodes and (Ba, Sr)TiO3 thin films

Abstract

The electrical conduction properties of rf sputter-deposited (Ba, Sr)TiO3 (BST) films on Pt and IrO2 electrodes and metalorganic chemical vapor deposited (MOCVD) BST films on a Pt electrode were investigated and a new energy band model that satisfactorily explains the observed leakage current characteristics and film thickness dependent dielectric properties is proposed. The BST and Pt junction constituted a blocking contact with interface potential barrier heights of 1.6–1.7 eV and 1.2 eV for the sputtered and MOCVD films, respectively. Schottky emission behavior was observed at measurement temperatures higher than 120 °C and tunneling related conduction behavior appeared below that temperature for a film thickness of 40 nm. A partial depletion model with a very thin (about 1 nm) layer devoid of space charge at the interface with the Pt electrode is proposed to explain the V1/2 dependent variation of ln(Jo) as well as the decreasing dielectric constant with decreasing film thickness.

Dielectric properties of BaMg1∕3Nb2∕3O3 doped Ba0.45Sr0.55Tio3 thin films for tunable microwave applications

“…40 The values of " r extracted from the SE plots for the undoped BST film are in the range of 5.76 to 1.49 (Table 1, column 2), decreasing with the increase of temperature from 300 to 450 K. These " r values agree well with the reported results ranging between 3.5 and 6.0. 36,[39][40][41][42] The well-fitted curve along with the rational " r values confirm that the SE is the dominant conduction mechanism in the undoped BST film. Conversely, the " r values extracted by fitting the current data for the doped film against the SE model (data not shown) were found to be unrealistically small (ranging from 1.50 to 0.47, see Table 1, column 3), suggesting that the conduction method in the BMN doped BST film is non-SE mechanism.…”

Effect of manganese doping on the size effect of lead zirconate titanate thin films and the extrinsic nature of ‘dead layers’

“…Although the interfacial-layer concept has been shown to be successful in explaining many of the experimental data in the literature, an experimentally consistent explanation for the nature of such layers is still lacking. Various models proposed in the past include a defect/space-charge layer with low ε at the electrode-ferroelectric interface, 9 termination of chemical bonds at the interface, 10 interdiffusion of elements, 11 chemically different phases/layers, 12 changes in spontaneous polarization and polarizability of surface layers, [13][14][15] polarization reduction at the film surface due to an increase in the depolarization field as film thickness decreases, 16 Schottky barrier formation and the resultant surface depletion layer, 17 finite electronic screening length in metallic electrodes, 18 strain 19 /strain-gradient coupling 20 at the ferroelectric-electrode interface and so forth. However, none of the above is fully consistent with the extensive body of experimental observations published previously, and a complete understanding of the origin of size effects in ferroelectric thin-film capacitors has not been achieved so far.…”

Thickness-dependent dielectric properties of nanoscale Pt/(Pb,Ba)ZrO3/BaPbO3 capacitors

“…There are many researchers who reported similar reduction of dielectric constant in thin films. Various origins have been proposed [3][4][5][6][7][8]. In order to explain the dependence, Fig.…”

“…The origin of this reduced capacitance is often discussed in terms of a low-permittivity interfacial ''dead'' layer [2]. Many possible factors have been proposed for this interfacial layers such as (i) defects and heterogeneous stresses near the electrode interface [3], (ii) the interfacial discontinuity affecting the polarization states in the ferroelectric close to the electrode-dielectric interface [2,4], (iii) field penetration into the metal electrode [4,5], (iv) Schottky barriers formed as a result of mismatch in the band structure between dielectric and electrode [6,7], and (v) grain-boundary dead layer [8].…”

“…(b) Grazing-incident (0.31) X-ray diffraction patterns of thin PBZ (9-40 nm) films. (c) Grazing-incident X-ray diffraction patterns of the 40 nm PBZ under different grazing angles (0 [3][4][5][6][7][8][9][10][11]…”