GIWAXS Characterization of Metal–Organic Framework Thin Films and Heterostructures: Quantifying Structure and Orientation

Abstract

For optoelectronic applications of metal–organic framework (MOF) thin films, it is important to be able to fabricate films and heterostructures that are highly oriented relative to the substrate's surface normal. However, process optimization to achieve this is difficult without sufficiently detailed structural characterization of the deposited films. It is demonstrated that 2D grazing‐incidence wide‐angle X‐ray scattering (GIWAXS) data from a laboratory system go a long way to providing such characterization and can 1) better test structural models than 1D scans, 2) provide a quantitative estimate—useful for process optimization—of the fraction of the deposited film that has the desired surface‐oriented texture (2D powder), and 3) deliver such information as a function of depth into the film—useful for heterostructure characterization. Herein, GIWAXS data collection and analysis are introduced in the context of understanding MOF thin films, then it is shown how the desired oriented fraction (2D powder fraction) of UiO‐66 fabricated by vapor‐assisted conversion can be increased from 4% to over 95% by minimizing nucleation in solution. Finally, it is demonstrated that heterostructures of UiO‐66 and UiO‐67 can be grown wherein both layers are highly ordered (UiO‐66 83%, UiO‐67 >94%) once synthetic protocols are optimized.

Icephobic Gradient Polymer Coatings Deposited via iCVD: A Novel Approach for Icing Control and Mitigation

“…This correction is valid if the crystallites have an isotropic orientation with respect to the surface normal, which both the 2D and 3D powder textures possess. 53 Figure 2b shows the comparison of the corrected intensity profiles of the gradient polymers for each angle (ϕ) of the arc (i.e., from 0 to 90°). The three distinguished areas correspond to the estimated fraction of crystallites at different orientations.…”

“…The intensity profiles were extracted from the two-dimensional (2D) maps and later corrected by applying a Lorentz correction factor (sin­(ϕ)). This correction is valid if the crystallites have an isotropic orientation with respect to the surface normal, which both the 2D and 3D powder textures possess …”

[001]-Oriented heteroepitaxy for fabricating emissive surface mounted metal–organic frameworks

“…The scattering of this chosen peak does not position on q⃑ z axis, so that we can extrapolate the intensity of the corresponding ring to the origin and measure the entire intensity of the peak by Gaussian fitting as we have done in previous work. 37 As the penetration depth of the X-rays is dependent on the incidence angle, α i , of the primary beam in the GIWAXS technique, we collected a diffractogram for 18C/2C-(Zn/Cu) 2 (BDC) 2 (DABCO) at α i = 0.6° to obtain the scattering from the entire sample thickness (Fig. 4a).…”

“…In addition, a correction to the pole figure to account for the fraction of the scattering signal observed at each γ was introduced. 37 This can be accomplished by multiplying the measured intensity, I ( γ ), by sin( γ ). The sin( γ ) corrected pole figure so generated (shown in Fig.…”

Morphology and orientation change of layer-by-layer deposited one- and two-dimensional coordination polymer nanocrystals containing rhodium paddle-wheel units

“…36 The preferred orientation is usually investigated by means of X-ray diffraction methods. 37 Hence, we have applied also X-ray scattering methods 38 under grazing incidence (GI) conditions in addition to conventional powder X-ray diffraction to confirm and to complement the AFM results. The GI methods for small and wide angle X-ray scattering (GISAXS, GIWAXS) allow a statistical interpretation of the microscopic data because of the comparably large probed volume.…”