Conduction mechanisms and an evidence for phonon-assisted conduction process in thin high-k HfxTiySizO films
Abstract Electrical behavior of high-k Hf x Ti y Si z O layers with different Hf:Ti ratios in the film have been investigated. The films are prepared by MOCVD using novel single-source precursors chemistry. Oxide and interface charges, leakage currents and conduction mechanisms are found to be a strong function of the film composition. The films with lower Hf content show lower level of oxide and interface charges and higher dielectric constant whereas those with higher Hf content have better leakage current properties. It is established that in the films with lower Hf content the conduction is governed by a phonon-assisted process. The change of the conduction mechanism from Poole–Frenkel emission to phonon-assisted tunneling is assigned to possible structural changes which take place when changing the composition of the films.
Analysis of current‐voltage characteristics of metal‐insulator composite films
We present a method for analyzing current‐voltage relationships to obtain information on the dominant conduction mechanisms. The method is based on the analysis of the derivative of the logarithmic conductivity with respect to inverse applied electrical field. To illustrate the method we apply it to the study of Co‐Al2O3 and Au‐Al2O3 composite films. The former material displays space‐charge‐limited conduction, which is due to a high density of trap states in the oxide matrix. On the other hand, Au‐Al2O3 shows evidence of percolation and tunneling between metal particles.
Private nursing homes: Providing good value?
The well‐documented expansion in the supply of residential and nursing home care over the past decade has been fuelled by public funds. About half of the patients receiving care in private homes are receiving income support towards their fees. There is now growing concern that the substantial amounts involved should represent value for money.