Search

Herein, the fabrication of bioinspired moth‐eye antireflective (AR) films based on surface nanocomposites of poly vinylidene fluoride (PVDF) and TiO2 nanoparticles produced in a single thermal nanoimprint lithography step is described. The incorporation of nanoparticles enhances the mechanical and thermal stability of the AR topography as demonstrated by nanoindentation tests and in situ temperature‐dependent grazing incidence X‐ray scattering measurements using synchrotron radiation. The effect of thermal annealing and UV radiation on the degradation in the optical performance and durability of the AR films is also evaluated in weathering tests. Improving the thermal and mechanical behavior as well as the long‐term durability of nanoimprinted polymer AR films will significantly expand their potential for implementation in solar devices. [ABSTRACT FROM AUTHOR]

Multilayer thin films consisting of titanium nitride (TiN) and silicon nitride (SiNx) layers with compositional modulation periodicities between 3.7 and 101.7 nm have been grown on silicon wafers using reactive magnetron sputtering. The TiN and SiNx layer thicknesses were varied between 2–100 nm and 0.1–2.8 nm, respectively. Electron microscopy and x-ray diffraction studies showed that the layering is flat with distinct interfaces. The deposited TiN layers were crystalline and exhibited a preferred 002 orientation for layer thicknesses of 4.5 nm and below. For larger TiN layer thicknesses, a mixed 111/002 preferred orientation was present as the competitive growth favored 111 texture in monolithic TiN films. SiNx layers exhibited an amorphous structure for layer thicknesses >=0.8 nm; however, cubic crystalline silicon nitride phase was observed for layer thicknesses <=0.3 nm. The formation of this metastable SiNx phase is explained by epitaxial stabilization to TiN. The microstructure of the multilayers displayed a columnar growth within the TiN layers with intermittent TiN renucleation after each SiNx layer. A nano-brick-wall structure was thus demonstrated over a range of periodicities. As-deposited films exhibited relatively constant residual stress levels of 1.3±0.7 GPa (compressive), independent of the layering. Nanoindentation was used to determine the hardness of the films, and the measurements showed an increase in hardness for the multilayered films compared to those for the monolithic SiNx and TiN films. The hardness results varied between 18 GPa for the monolithic TiN film up to 32 GPa for the hardest multilayer, which corresponds to the presence of cubic SiNx. For larger wavelengths, >=20 nm, the observed hardness correlated to the layer thickness similar to a Hall–Petch dependence, but with a generalized power of 0.4. Sources of the hardness increase for shorter wavelengths are discussed, e.g., epitaxial stabilization of metastable cubic SiNx, coherency stress, and impeded dislocation activity. [ABSTRACT FROM AUTHOR]

Epitaxial Ti3SiC2(0001) thin films have been deposited by dc magnetron sputtering from three elemental targets of Ti, C, and Si onto MgO(111) and Al2O3(0001) substrates at temperatures of 800-900 ° C. This process allows composition control to synthesize Mn+1 AXn (MAX) phases (M: early transition metal; A: A-group element; X: C and/or N; n= 1 -3) including Ti4SiC3. Depositions on MgO(100) substrates yielding the Ti-Si-C MAX phases with (1015), as the preferred orientation. Samples grown at different substrate temperatures, studied by means of transmission electron microscopy and x-ray diffraction investigations, revealed the constraints of Ti3SiC2 nucleation due to kinetic limitations at substrate temperatures below 700 °C. Instead, there is a competitive Ticx growth with Si segregation to form twin boundaries or Si substitutional incorporation in TiCx. Physical properties ot the as-deposited single-crystal Ti3SiC2 films were determined. A low resistivity of 25 µω cm was measured. The Young's modulus, ascertained by nanoindentation, yielded a value of 343 -370 GPa. For the mechanical deformation response of the material, probing with cube corner and Berkovich indenters showed an initial high hardness of almost 30 GPa. With increased maximum indentation loads, the hardness was observed to decrease toward bulk values as the characteristic kink formation sets in with dislocation ordering and delamination at basal planes. [ABSTRACT FROM AUTHOR]

Multilayer thin films consisting of titanium nitride (TiN) and silicon nitride (SiNx) layers with compositional modulation periodicities between 3.7 and 101.7 nm are grown on silicon wafers using reactive magnetron sputtering. Electron microscopy and X-ray diffration studies showed that the layering is flat with distinct interfaces.