A novel atomic layer deposition (ALD) route of Y2O3 thin films was developed and demonstrated utilizing Y(iPrCp)3 and O3. The ALD growth characteristics were investigated by varying precursor dosage, reactor temperature, and number of deposition cycles. The growth rate of Y2O3 was found to be 0.17 {plus minus} 0.01 nm/cycle within the ALD temperature window of 245 - 300 ºC. The resulting films were analyzed with spectral ellipsometry and x-ray photoelectron spectroscopy, in order to determine stoichiometry, impurity, annealing behavior, and refractive index. The results of this work demonstrate the potential for suggesting Y(iPrCp)3 as a suitable ALD precursor and Ar+ beam as an effective means of removing surface Y(OH)3 on Y2O3 films.
The authors report a new chemical approach for the selective atomic layer deposition of ultrathin layers of zirconium oxide (ZrO2) on copper patterned silicon surfaces. Instead of using common atomic layer deposition (ALD) oxygen sources such as water, oxygen, or ozone, the authors use ethanol, which serves as oxygen source for the ALD on the silicon side and as effective reducing agent on the copper side, thereby selectively depositing ZrO2 film on the silicon surface of the substrate without any deposition on copper up to at least 70 ALD cycles. The resulting ZrO2 nanofilm is found to be an effective copper diffusion barrier at temperatures at least up to 700 °C.
Atomic layer deposition (ALD) is a technique increasingly used in nanotechnology and ultrathin film deposition; it is ideal for films in the nanometer and Angstrom length scales. ALD can effectively be used to modify the surface chemistry and functionalization of engineering-related and biologically important surfaces. It can also be used to alter the mechanical, electrical, chemical, and other properties of materials that are increasingly used in biomedical engineering and biological sciences. ALD is a relatively new technique for optimizing materials for use in bio-nanotechnology. Here, after a brief review of the more widely used modes of ALD and a few of its applications in biotechnology, selected results that show the potential of ALD in bio-nanotechnology are presented. ALD seems to be a promising means for tuning the hydrophilicity/hydrophobicity characteristics of biomedical surfaces, forming conformal ultrathin coatings with desirable properties on biomedical substrates with a high aspect ratio, tuning the antibacterial properties of substrate surfaces of interest, and yielding multifunctional biomaterials for medical implants and other devices.
Inspired by the need to discover environmentally friendly, lead-free ferroelectric materials, here the authors report the atomic layer deposition of tin titanate (SnTiO x) aiming to obtain the theoretically predicted perovskite structure that possesses ferroelectricity. In order to establish the growth conditions and probe the film structure and ferroelectric behavior, the authors grew SnTiO x films on the commonly used Si(100) substrate. Thin films of SnTiO x have been successfully grown at a deposition temperature of 200 C, with a Sn/Ti atomic layer deposition (ALD) cycle ratio of 2:3 and postdeposition heat treatments under different conditions. X-ray photoelectron spectroscopy revealed excellent composition tunability of ALD. X-ray diffraction spectra suggested anatase phase for all films annealed at 650 and 350 C, with peak positions shifted toward lower 2-theta angles indicating enlarged unit cell volume. The film annealed in O 2 at 350 C exhibited piezoresponse amplitude and phase hysteresis loops, indicative of the existence of switchable polarization. V
We report the development of a novel portable atomic layer deposition chemical vapor deposition (ALD/CVD) hybrid reactor setup. Unique feature of this reactor is the use of ALD/CVD mode in a single portable deposition system to fabricate multi-layer thin films over a broad range from "bulk-like" multi-micrometer to nanometer atomic dimensions. The precursor delivery system and control-architecture are designed so that continuous reactant flows for CVD and cyclic pulsating flows for ALD mode are facilitated. A custom-written LabVIEW program controls the valve sequencing to allow synthesis of different kinds of film structures under either ALD or CVD mode or both. The entire reactor setup weighs less than 40 lb and has a relatively small footprint of 8 × 9 in., making it compact and easy for transportation. The reactor is tested in the ALD mode with titanium oxide (TiO2) ALD using tetrakis(diethylamino)titanium and water vapor. The resulting growth rate of 0.04 nm/cycle and purity of the films are in good agreement with literature values. The ALD/CVD hybrid mode is demonstrated with ALD of TiO2 and CVD of tin oxide (SnOx). Transmission electron microscopy images of the resulting films confirm the formation of successive distinct TiO2-ALD and SnO(x)-CVD layers.
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