We have studied the atomic layer deposition (ALD) of ruthenium using bis(2,4-dimethylpentadienyl) ruthenium and oxygen. We show that the process is achievable at a low operating temperature of 185 °C. Variation in the exposure time and pressure of the oxygen counterreactant has significant effects on the nucleation, growth rate and composition of the deposited ruthenium films. High oxygen pressure helps to promote the nucleation of ruthenium on a silicon dioxide substrate. Although saturation conditions are achieved with the Ru precursor, saturation of the ruthenium growth rate with oxygen exposure is observed only for a small range of oxygen exposure. Increasing the oxygen exposure further results in the incorporation of oxygen in the deposited film to form ruthenium oxide, a process which is enhanced at higher deposition temperature. We propose that the slow diffusion of oxygen to the subsurface region is a rate-limiting step in this process. We demonstrate that the composition of the deposited films from metallic ruthenium to ruthenium oxide, as well as the average grain size, may be regulated by tuning the pressure and exposure time of the oxygen counterreactant. Hence, this low temperature ALD process provides a flexible route to the deposition of Ru-based films.

We have investigated human anterior lens capsule as a potential replacement for Bruch's membrane as a treatment for age-related macular degeneration. Any substrate to replace Bruch's membrane should possess certain characteristics to maintain proper function of the overlying retina. One of the important properties of Bruch's membrane is allowing the flow of nutrients and waste between the retinal pigment epithelium and the choriocapillaris. Here, we measured the permeability of the lens capsule by studying the diffusion of various molecular weight FITC–dextran molecules. Expressions for extraction of diffusion coefficients from concentration vs. time data from a blind-well chamber apparatus were derived for both a single and double membrane experiments. The diffusion coefficients in the lens capsule were found to be in the range of 10−6 to 10−10 cm2/s. We demonstrated a power law relationship, with the diffusion coefficient possessing a −0.6 order dependence on molecular weight. The molecular weight exclusion limit was determined to be 150±40 kDa. We have compared this value with reported values of Bruch's membrane molecular weight exclusion limit and find that the lens capsule has the potential to act as a substitute Bruch's membrane.

The choice of filament material has an influence on the decomposition of silane during the hot wire chemical vapor deposition of amorphous and microcrystalline silicon films. In this paper, the Si radicals produced from W, Re, Mo and Ta filament materials are probed by laser-based single photon ionization as a function of hot wire temperature. The apparent activation energy of the Si radical production in the surface reaction regime from Ta (140–180 kcal/mol) and Mo (120–160 kcal/mol) are found to be close to the corresponding Si thermal desorption energies from these surfaces, suggesting that the Si production is controlled by the desorption process from the bare metal. On the other hand, the Si activation energies from W and Re (60 kcal/mol) are lower than the related desorption energies, suggesting silicon desorption from a silicon layer formed on the surfaces. Kinetic modeling supports this desorption mechanism. In addition to the Si radical study, the corresponding film deposition is detected in situ by multiple internal reflection infrared spectroscopy, from which growth rates are estimated. The results show similar activation energies for both the growth rate and Si formation from the various filaments, implying that Si radical production and subsequent film growth are dominated by the same elementary reactions at low pressure.

We have studied the atomic layer deposition (ALD) of ruthenium using bis(2,4-dimethylpentadienyl) ruthenium and oxygen. We show that the process is achievable at a low operating temperature of 185 °C. Variation in the exposure time and pressure of the oxygen counterreactant has significant effects on the nucleation, growth rate and composition of the deposited ruthenium films. High oxygen pressure helps to promote the nucleation of ruthenium on a silicon dioxide substrate. Although saturation conditions are achieved with the Ru precursor, saturation of the ruthenium growth rate with oxygen exposure is observed only for a small range of oxygen exposure. Increasing the oxygen exposure further results in the incorporation of oxygen in the deposited film to form ruthenium oxide, a process which is enhanced at higher deposition temperature. We propose that the slow diffusion of oxygen to the subsurface region is a rate-limiting step in this process. We demonstrate that the composition of the deposited films from metallic ruthenium to ruthenium oxide, as well as the average grain size, may be regulated by tuning the pressure and exposure time of the oxygen counterreactant. Hence, this low temperature ALD process provides a flexible route to the deposition of Ru-based films.