Search results for "Thin layers"
showing 10 items of 38 documents
Guest Effect on Nanopatterned Spin-Crossover Thin Films
2011
International audience; Nanopatterned thin films of the metal–organic framework {Fe(bpac)[Pt(CN)4]} (bpac=bis(4‐pyridyl)acetylene) are elaborated by the combination of a sequential assembly process and a lithographic method. Raman microspectroscopy is used to probe the temperature dependence of the spin state of the iron(II) ions in the films (40–90 nm in thickness), and reveals an incomplete but cooperative spin transition comparable to that of the bulk material. Adsorption/desorption of pyridine guest molecules is found to have a substantial influence on the spin‐crossover properties of the thin layers. This interplay between host–guest and spin‐crossover properties in thin films and nano…
The organization of aliphatic chains in ultra-thin layers and its importance for layer properties
2007
Colloidal crystallization in the quasi-two-dimensional induced by electrolyte gradients.
2012
We investigated driven crystal formation events in thin layers of sedimented colloidal particles under low salt conditions. Using optical microscopy, we observe particles in a thermodynamically stable colloidal fluid to move radially converging towards cation exchange resin fragments acting as seed particles. When the local particle concentration has become sufficiently large, subsequently crystallization occurs. Brownian dynamics simulations of a 2D system of purely repulsive point-like particles exposed to an attractive potential, yield strikingly similar scenarios, and kinetics of accumulation and micro-structure formation. This offers the possibility of flexibly designing and manufactur…
Raman signal reveals the rhombohedral crystallographic structure in ultra-thin layers of bismuth thermally evaporated on amorphous substrate
2021
Under the challenge of growing a single bilayer of Bi oriented in the (111) crystallographic direction over amorphous substrates, we have studied different thicknesses of Bi thermally evaporated onto silicon oxide in order to shed light on the dominant atomic structures and their oxidation. We have employed atomic force microscope, X-ray diffraction, and scanning electron microscope approaches to demonstrate that Bi is crystalline and oriented in the (111) direction for thicknesses over 20 nm. Surprisingly, Raman spectroscopy indicates that the rhombohedral structure is preserved even for ultra-thin layers of Bi, down to $\sim 5$ nm. Moreover, the signals also reveal that bismuth films expo…
Coexistence of structural and magnetic phases in van der Waals magnet CrI3
2021
CrI3 has raised as an important system to the emergent field of two-dimensional van der Waals magnetic materials. However, it is still unclear why CrI3 which has a ferromagnetic rhombohedral structure in bulk, changed to anti-ferromagnetic monoclinic at thin layers. Here we show that this behaviour is due to the coexistence of both monoclinic and rhombohedral crystal phases followed by three magnetic transitions at TC1 = 61 K, TC2 = 50 K and TC3 = 25 K. Each transition corresponds to a certain fraction of the magnetically ordered volume as well as monoclinic and rhombohedral proportion. The different phases are continuously accessed as a function of the temperature over a broad range of mag…
Corrosion processes and their inhibition as studied by Mössbauer conversion and other electron spectroscopies
1989
To study corrosion processes of iron and steel and measures of their inhibition, a detailed knowledge of the phase composition and of phase transformations in very thin layers close to the attacked surface of the material is necessary. The information depths of integral (ICEMS) and depth selective (DCEMS) conversion electron Mossbauer spectroscopy are well suited for such investigations, but some effort is necessary if technical samples, i.e. nonenriched in57Fe, are to be studied. In many cases of practical importance, full information on the corroded surfaces cannot be got from Mossbauer spectra only, and a combination with Auger and photoelectron spectroscopies, in-including scanning and …
Icems and dcems study of Fe layers evaporated onto Al and Si
1990
Thin layers of57Fe (2.5 nm, 10 nm and 70 nm thickness), vacuum evaporated onto Al and Si plates, have been investigated by conversion electron Mossbauer spectroscopy (CEMS). The measurements were performed employing both a proportional counter and a channeltron for conventional and ultrahigh-vacuum integral CEMS (UHV-ICEMS) studies, respectively, and a channeltron for depth-selective CEMS (DCEMS). The phase analysis of the layers on base of experimental results has indicated the presence of metallic iron and one or two iron compounds, ascribed to iron reaction products formed with the residual gas during evaporation. These products are most likely rather stable iron nitrides, are more or le…
4-(Diethylamino)salicylaldehyde-based twin compounds as NLO-active materials
2016
Abstract 4-(Diethylamino)salicylaldehyde-based twin compounds containing 1,3-indandione and 1,3-bisdicianovinylindane moieties were synthesized and their thermal, optical, photophysical, electrochemical, photoelectrical and nonlinear optical properties were studied. The synthesized compounds form glasses with the glass transition temperatures ranging from 79 to 103 °C. Photoluminescence spectra of the solutions of compounds exhibited red-shifts with the increase of the solvent polarity that was caused by the positive solvatochromic effect. The linear dependencies between the position of the photoluminescence maxima of compounds and the empirical parameter E T (30) of the different solvents …
Development and characterization of a Drop-on-Demand inkjet printing system for nuclear target fabrication
2017
Abstract A novel target preparation method based on Drop-on-Demand (DoD) inkjet printing has been developed. Conventional preparation methods like the electrochemical method “Molecular Plating” or the “Polymer-Assisted Deposition Method” are often limited, e.g., concerning the dimensions and geometries of depositions or by the requirement for electrically conducting substrates. Here, we report on the development of a new technique, which overcomes such limits by using a commercially available DoD dispenser. A variety of solutions with volumes down to 5 nL can be dispensed onto every manageable substrate. The dispensed volumes were determined with a radioactive tracer and the deposits of eva…
ODIn — A setup for Off-line Deposit Irradiations of thin layers for nuclear physics applications
2020
Abstract A table top setup was developed for the irradiation of thin layers with low-energy electrons and ions of gaseous species. This serves to gain a better understanding of the chemical microprocesses involved during irradiations. The gained insights will complement the understanding of heavy-ion beam induced transformations at on-line facilities and will be used to develop an accelerator-independent method to transform freshly produced targets into a long-term stable form. The pilot experiment for these Off-line Deposit Irradiations (ODIn) is installed at the Helmholtz Institute Mainz. The setup, beam characterization and first commissioning are described.