What properties do nanolaminates have that are absent in thicker multilayer films

1. What properties do nanolaminates have that are absent in thicker multilayer films Berseneva Natalia

2. What are nanolaminates? Nanolaminates are man made layered structures synthesized atom by atom using sputter deposition technology

3. Nanolaminates • Nanolaminates can be comprised of two or more different materials(A, B, C, etc…)‏ • Two key parameters of structural dimension are: • the characteristic layer pair spacing dA/B=ℓA+ℓB (also known as the composition wavelength) for a repeat sequence of A and B layers with thickness ℓA and ℓB, respectively • the grain size (dg)‏

4. Multilayers Multilayers can be divided into two categories: Isostructural multilayers are multilayers in which the individual layers have the same structure. They generally have the same dislocation slip systems, and therefore it is possible for dislocations to move across layer interfaces. 2) Non-isostructural multilayers consist of layers with different structures, and different dislocation slip systems, and this provides a further barrier to dislocation motion.

5. Hardness • Isostructural • - Material (for studying)‏ • Various transition-metal nitrides • such as TiN, VN, NbN, etc. (these • materials have a naturally high hardness)‏ • A maximum hardness of 5560 kg/mm2 • Material (for practical application)‏ • TiN/NbN multilayers were deposited on tool • steel substrates at low temperatures • <300C using magnetron sputtering. • A maximum hardness of 5200 kg/mm2 • Non-isostructural • The analysis of the hardness data is generally more complicated due to the epitaxial stabilization effect.

6. Reflectance • The difficulty in producing efficient X-ray optics is due primarily to the fact that at incidence angles much larger than the critical angle for total external reflection, the X-ray reflectance at the interface between any two materials is exceedingly low • Solution • stack of layers - or a stack of interfaces, really - is arranged such that the reflections from each interface add in phase, giving rise to high reflectance over a limited range of incidence angles and photon wavelengths • the bilayer period varies continuously throughout the film stack, so that each bilayer is effectively tuned to a specific wavelength (for a given incidence angle); the overall response of the film can thus be adjusted to provide high reflectance over a wide range of photon energies, simply by adjusting the specific distribution of bilayer thicknesses.

7. Electrical properties • Capacitors based on nanolaminate dielectrics (combination of Gd2O3 or Er2O3 with ZrO2) demonstrated high capacitance and good insulating properties with low leakage current density at approximately 10-7A/cm2 • Low thermal conductivity of around 0.6 W/m2/K

8. Electrical properties • k- dielectric constant • J- leakage current density

9. Nanocrystalline nanolaminates are widely used in fundamental studies of material behaviors and in a variety of industries with applications as: - X-ray optics for lithography - low-temperature stability - ultra-hardwear-resistant coatings Application of nanocrystalline nanolaminates

10. Conclusion • Nanolaminates show unique physical properties when the nanolayer thickness is less than the characteristic length scale that defines the physical property. For example, thermal conductivity is reduced when the nanolayer thickness is less than the mean free path of the phonon that transfers the heat. • Hardness is increased when the nanolayer thickness is less than the dislocation length for the slip plane motion that characterizes the response of the material to stress. • By depositing nanolaminates with various compositional ratios and different nanolayer thicknesses, the electrical and structural properties of the film can be tuned over a wide range.

11. References • J.M. Jungk at all, PROPERTIES AND FRACTURE OF TUNGSTEN-ALUMINA ATOMIC LAYER DEPOSITED NANOLAMINATES • P.C. Yashar, W.D. Sproul / Vacuum 55 (1999) 179}190 • Surface & Coatings Technology 203 (2008) 484–489 • David L. Windt, Multilayer Films for Figured X-Ray Optics • Aile Tamm at all, ATOMIC LAYER DEPOSITION AND CHARACTERIZATION OF ZrO2-Er2O3 AND ZrO2-Gd2O3 NANOLAMINATES • H. Zhang at all, High permittivity thin film nanolaminates

12. Thank you for your attention!