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Research was conducted to examine the conducting oxide electrode (Ba,Sr)RuO3 (BSR) for (Ba,Sr)TiO3 (BST). The electrode was assumed to be advantageous for BST because of its similarity in structure and chemical composition. By changing the Ba/Sr ratio or (Ba+Sr)/Ru ratio in BSR films, the effects of structural and chemical variation in BSR electrodes on the properties of BST films were investigated. Results show that the BSR electrode is the most promising one for BST dielectric material among the oxide electrodes.

1% Ni-doped barium strontium titanate (BST) thin film deposited at room temperature reveals the significantly enhanced leakage current performance which is extraordinarily effective for low temperature applications. Significant leakage current suppression of >2 orders was achieved for electric fields from 0.25 to 2 MV/cm in Pt/Ni-doped BST/Pt metal-insulator-metal (MIM) capacitor cells compared to undoped BST. For Ni doping at the 1% level, the spectral dependence of (i) the imaginary part of the complex dielectric constant, [variant_greek_epsilon]2, obtained from the rotating compensator enhanced spectroscopic ellipsometry and (ii) OK1 absorption spectra obtained from synchrotron x-ray absorption spectroscopy shows significant differences (0.26±0.15 eV) in the conduction band edge trap depth relative to undoped BST. The valence band (VB) edge x-ray photoelectron spectroscopy analysis reveals the Fermi energy level downshift of 0.4 eV for Ni-doped BST toward the VB edge. There is a direct correlation between these changes in band edge states of BST thin films with Ni doping and the improved electrical performance in MIM capacitors led by the qualitatively different charge injection mechanism. The proposed transition metal doping process and analysis approach provide a pathway for charge injection control driven by band edge state changes in other perovskite oxides for low temperature (i.e., room temperature) applications. [ABSTRACT FROM AUTHOR]

Degradation of (Ba,Sr)TiO[sub 3] during a forming gas anneal was examined and the effect of a SiO[sub 2] capped (Ba,Sr)RuO[sub 3] electrode was studied. All the samples were prepared by a rf magnetron sputtering technique and the forming gas (10% H[sub 2]+90% N[sub 2]) anneal was carried out at 400 °C for 30 min. The (Ba,Sr)RuO[sub 3] film directly exposed to H[sub 2] ambient was damaged severely, which resulted in the reduction and phase separation into BaO and Ru. On the other hand, the SiO[sub 2] capped (Ba,Sr)RuO[sub 3] film was not damaged during H[sub 2] annealing. By adopting the SiO[sub 2] capped (Ba,Sr)RuO[sub 3] as an electrode of (Ba,Sr)TiO[sub 3], the degradation of (Ba,Sr)TiO[sub 3] could be inhibited. SiO[sub 2] capping also decreased the extent of the reduction of a Pt/(Ba,Sr)TiO[sub 3]/Pt structured capacitor, which is known to degrade dramatically. It is believed that the major cause of the tolerance to the forming gas anneal is the blocking capability of SiO[sub 2] against the diffusion of reaction products such as H[sub 2]O. © 2003 American Institute of Physics. [ABSTRACT FROM AUTHOR]

The (Ba,Sr)RuO[sub 3] (BSR) oxide electrode which can enhance electrical properties of (Ba,Sr)TiO[sub 3] (BST) dielectric film due to structural and chemical matches with BST, was evaluated as an oxygen diffusion barrier. It was possible to restrain the oxidation of TiN layer under BSR to TiO[sub 2] by sequential depositions of amorphous BSR and crystalline BSR, in which the amorphous BSR eventually crystallized into crystalline BSR during the deposition of crystalline BSR. When two-step BSR layers on TiN, however, were annealed in oxygen ambient at 700 °C, oxygen atoms diffused and oxidized TiN layer to TiO[sub 2]. On the other hand, oxygen could be effectively blocked by the BSR/Ru bilayer. In this system, the Ru sublayer plays a role as an oxygen getter and the bilayer tends to block oxygen diffusion. The blocking effect was more obvious when the thickness of BSR in the bilayer increased. The BST/bilayer showed higher dielectric constant due to the suppression of formation of a low dielectric layer between BST and the bilayer. Although the BST/bilayer showed a slightly higher leakage current density, it was possible to reduce the leakage current density to 10[sup -8] order A/cm² at 1 V by increasing the BSR thickness in the bilayer. [ABSTRACT FROM AUTHOR]

Perovskite type conducting materials (Ca, Sr)RuO[sub 3] and (Ba, Sr)RuO[sub 3] were prepared by rf magnetron sputtering as bottom electrodes for (Ba, Sr)TiO[sub 3] thin film capacitors. The crystallinity, interface property, and electrical properties of the (Ba, Sr)TiO[sub 3] capacitor applying the perovskite oxide electrodes were investigated. The interface between the dielectric and the electrode were analyzed by high-resolution electron microscopy and Auger electron spectroscopy. The interface had a marked effect on the electrical properties of the (Ba, Sr)TiO[sub 3] thin films. Dielectric constant for the (Ba, Sr)TiO[sub 3] had considerable dependence on the thickness of interfacial layer. The leakage current density of the capacitor was sensitive not only to the structural match but also to the chemical match between (Ba, Sr)TiO[sub 3] and the electrode. © 2000 American Institute of Physics. [ABSTRACT FROM AUTHOR]

A study was conducted to investigate the oxygen diffusion properties of (Ba,Sr)TiO3 (BST) dielectric films deposited on TiN coated Si wafers. The result indicates that the ability of blocking oxygen diffusion for the two-step BSR layer on TiN is poor and similar to that of the Pt electrode, except that the degree of oxidation in two-step BSR/TiN is slightly less than that in Pt/TiN.