No abstract

Atomic layer deposition (ALD) can be used to deposit ultra-thin and conformal films on flat substrates, high aspect ratios structures and particles. In this paper, we demonstrate that insulating, multilayered and functionalized ALD coatings can also be deposited conformally on carbon nanotubes. Multilayered coatings consisting of alternating layers of dielectric and conductive materials, such as Al2O3 and W, respectively, are deposited on conductive multi-walled carbon nanotubes. This coated carbon nanotube can function as a nanoscale coaxial cable. Thin layers of Al2O3 ALD are also used as a seed layer to functionalize nanotubes. A carbon nanotube was made highly hydrophobic using an Al2O3 ALD seed layer followed by the attachment of perfluorinated molecules.

Presented in this paper is a study of the biocompatibility of an atomic layer-deposited (ALD) alumina (Al 2 O 3 ) thin film and an ALD hydrophobic coating on standard glass cover slips. The pure ALD alumina coating exhibited a water contact angle of 558 6 58 attributed, in part, to a high concentration of À ÀOH groups on the surface. In contrast, the hydrophobic coating (tridecafluoro-1,1,2,2-tetrahydro-octyl-methyl-bis(dimethylamino)silane) had a water contact angle of 1088 6 28. Observations using differential interference contrast microscopy on human coronary artery smooth muscle cells showed normal cell proliferation on both the ALD alumina and hydrophobic coatings when compared to cells grown on control substrates. These observations suggested good biocompatibility over a period of 7 days in vitro. Using a colorimetric assay technique to assess cell viability, the cellular response between the three substrates can be differentiated to show that the ALD alumina coating is more biocompatible and that the hydrophobic coating is less biocompatible when compared to the control. These results suggest that patterning a substrate with hydrophilic and hydrophobic groups can control cell growth. This patterning can further enhance the known advantages of ALD alumina, such as conformality and excellent dielectric properties for biomicro electro mechanical systems (Bio-MEMS) in sensors, actuators, and microfluidics devices.

A dynamical scanning tunneling microscopy and density functional theory study of the thermodynamic stability of halogen-terminated Si(100) surfaces is presented. Significant steric repulsion is shown to exist on all halogen-terminated Si(100) surfaces. This repulsion is the driving force for a roughening phenomenon, which is favored for all halogens except fluorine. Since roughening is an intrinsic property of these surfaces, it sets a lower bound on the atomic scale perfection that can be achieved using halogen etch processing.

No abstract