A high-temperature series for the spin-glass order-parameter susceptibility is presented for n-component spins on a &dimensional hypercubic lattice. The coupling between neighbouring spins is taken to be a Gaussian random variable. The series is analysed for the cases of XY (n = 2) and Heisenberg (n = 3) spins. In each case the transition temperature falls to zero near four dimensions, indicating that there is no Edwards-Anderson order in less than four dimensions.

Pt/(Ba, Sr)TiO 3 /Pt capacitors fabricated by sputtering technique showed abnormally higher leakage current when negative bias was applied to the top electrode. In this letter, two kinds of processes were attempted to reduce high leakage current of Pt/BST/Pt capacitors for dynamic random access memory devices: (1) postannealing under O2 atmosphere and (2) adding oxygen into sputtering gas of platinum top electrode. These processes were very effective to reduce the oxygen vacancy in the BST films which are mostly responsible for such a high leakage current. The higher reverse currents were significantly lowered by these processes, so that we could obtain symmetric current versus voltage curves of Pt/BST/Pt capacitors.

Pt/(Ba, Sr)TiO3/Pt capacitors were fabricated on TiN/Ti/ Poly–Si/SiO2/Si substrate by sputtering technique and effects of post-annealing conditions on the current vs. voltage ( I–V ) characteristics of the capacitors were investigated. It was found that leakage currents of Pt/BST/Pt capacitors were greatly depended on the annealing sequence as well as annealing atmosphere. BST films annealed under Ar/H2 or N2 showed much higher leakage current than as-deposited films regardless of the fabrication of top electrode. On the contrary, annealing under O2 atmosphere was effective to reduce leakage currents of the BST films if annealing process was carried out after fabrication of top electrode. Leakage current of Pt/BST(50 nm)/Pt capacitors annealed under O2 atmosphere at 500° C for 1 h after fabrication of Pt top electrode was 5×10-7 A/cm2 even at 7 V. In this work, effects of annealing conditions on the I–V properties of Pt/BST/Pt capacitors were explained with energy band diagram in which oxygen vacancies play a key role.

Ir films deposited on polycrystalline silicon (poly-Si), with and without barrier layer, were annealed and the thermal stability was investigated to check the feasibility of the structure for bottom electrode of integrated ferroelectric capacitors. Ir did not form silicide up to 700 °C and did not get oxidized up to 550 °C. It was found that Ir prevented diffusion of oxygen through it when annealed at 700 °C. Ir/poly-Si is believed to be most promising for bottom electrode structure from the results.

Electrode materials such as Pt, Ru, and Ir on polycrystalline silicon were annealed and the thermal stability was investigated to check the feasibility of the structure. Sputtered Pt reacted w i t h silicon to form PtSi at a low temperature of 400°C and the top layer of silicide was oxidized in oxygen ambient. Ru and Ir films by sputtering were also silicidized above 550°C and it made voids beneath silicide layers. All of the films are found to allow oxygen to diffuse through them and to get the underlying layers oxidized. However, Ir deposited by e-beam evaporation did not form silicide up to 700°C and did not get oxidized up to 550°C. Ir also allowed oxygen diffusion when annealed at 550°C or lower temperature, but it was prevented when annealed at 700 "C .