The molecular layer deposition (MLD) of a hybrid organic-inorganic polymer based on zinc is demonstrated using sequential exposures of diethyl zinc (DEZ, Zn(CH 2 CH 3 ) 2 ) and ethylene glycol (EG, HOCH 2 CH 2 OH). This polymer is representative of a class of zinc alkoxide polymers with an approximate formula of (ÀZnÀOÀRÀOÀ) n that can be called ''zincones''. The film growth and surface chemistry during zincone MLD is studied using in-situ Fourier transform infrared (FTIR) measurements. The absorbance of the infrared features of the zincone film increase progressively versus the number of MLD cycles. The FTIR spectra after the DEZ and EG exposures are consistent with the gain and loss of absorbance from CÀH, OÀH, CÀO, and ZnÀO stretching vibrations. FTIR studies also confirm the self-limiting nature of the surface reactions and monitor the temperature dependence of the film growth. Transmission electron microscope (TEM) images of ZrO 2 nanoparticles show very conformal zincone films and determine that the growth rate varies from 4.0 Å per MLD cycle at 90 8C to 0.25 Å per MLD cycle at 170 8C. Quartz crystal microbalance (QCM) and X-ray reflectivity (XRR) measurements show linear zincone growth versus the number of MLD cycles. XRR studies on silicon wafers are consistent with a growth rate of 0.7 Å per MLD cycle at 130 8C. The higher growth rate on the ZrO 2 nanoparticles is attributed to the lower gas conductance and possible CVD reactions in the ZrO 2 nanoparticles. The reaction mechanism for zincone MLD is dependent on temperature. At higher temperatures, there is evidence for ''double'' reactions of EG because no free hydroxyl groups are observed in the FTIR spectrum after the EG exposures. The zincone film can grow in the absence of free hydroxyl groups if DEZ can diffuse into the zincone film and react during the subsequent EG exposure. The zincone films initially adsorb H 2 O upon exposure to air and then are very stable with time.

Polymers in space may be subjected to a barrage of incident atoms, photons, and/or ions. Atomic layer deposition (ALD) techniques can produce films that mitigate many of the current challenges for space polymers. We have studied the efficacy of various ALD coatings to protect Kapton polyimide, FEP Teflon, and poly(methyl methacrylate) films from atomic-oxygen and vacuum ultraviolet (VUV) attack. Atomic-oxygen and VUV studies were conducted with the use of a laser-detonation source for hyperthermal O atoms and a D2 lamp as a source of VUV light. These studies used a quartz crystal microbalance (QCM) to monitor mass loss in situ, as well as surface profilometry and scanning electron microscopy to study the surface recession and morphology changes ex situ. Al2O3 ALD coatings protected the underlying substrates from atomic-oxygen attack, and the addition of TiO2 coatings protected the substrates from VUV-induced damage. The results indicate that ALD coatings can simultaneously protect polymers from oxygen-atom erosion and VUV radiation damage.

The mechanical robustness of atomic layer deposited alumina and recently developed molecular layer deposited aluminum alkoxide ͑"alucone"͒ films, as well as laminated composite films composed of both materials, was characterized using mechanical tensile tests along with a recently developed fluorescent tag to visualize channel cracks in the transparent films. All coatings were deposited on polyethylene naphthalate substrates and demonstrated a similar evolution of damage morphology according to applied strain, including channel crack initiation, crack propagation at the critical strain, crack densification up to saturation, and transverse crack formation associated with buckling and delamination. From measurements of crack density versus applied tensile strain coupled with a fracture mechanics model, the mode I fracture toughness of alumina and alucone films was determined to be K IC = 1.89Ϯ 0.10 and 0.17Ϯ 0.02 MPa m 0.5 , respectively. From measurements of the saturated crack density, the critical interfacial shear stress was estimated to be c = 39.5Ϯ 8.3 and 66.6Ϯ 6.1 MPa, respectively. The toughness of nanometer-scale alumina was comparable to that of alumina thin films grown using other techniques, whereas alucone was quite brittle. The use of alucone as a spacer layer between alumina films was not found to increase the critical strain at fracture for the composite films. This performance is attributed to the low toughness of alucone. The experimental results were supported by companion simulations using fracture mechanics formalism for multilayer films. To aid future development, the modeling method was used to study the increase in the toughness and elastic modulus of the spacer layer required to render improved critical strain at fracture. These results may be applied to a broad variety of multilayer material systems composed of ceramic and spacer layers to yield robust coatings for use in chemical barrier and other applications.Public reporting burden for the collection of information is estimated to average 1 hour per response, including the time for reviewing instructions, searching existing data sources, gathering and maintaining the data needed, and completing and reviewing the collection of information. Send comments regarding this burden estimate or any other aspect of this collection of information, including suggestions for reducing this burden, to Washington Headquarters Services, Directorate for Information Operations and Reports, 1215 Jefferson Davis Highway, Suite 1204, Arlington VA 22202-4302. Respondents should be aware that notwithstanding any other provision of law, no person shall be subject to a penalty for failing to comply with a collection of information if it does not display a currently valid OMB control number.