RESUMEN
Aqueous solutions of zirconium and hafnium (M) halides (X) with atomic ratios α = X/M near 1 form glasses on evaporation. Herein, we describe the preparation and properties of these glasses and discuss the nature of the crystal-glass equilibria beyond the pure glass compositions. Small- and wide-angle X-ray scattering (SWAXS) studies reveal increased polymerization as α decreases from 2 to 1. The glasses are found to be much denser than their crystalline counterparts. Crystals forming in contact with glasses retain the well-known Zr-tetrameric hydroxo cluster unit with hydroxide compensating for the lowered halide content. We find that the chemical formulas for all of the solid hydroxohalides may be described by the single parameter α, according to the formula M(OH)4-αXα·(4α - 1)H2O. This description is valid for the crystalline chloride (MOX2·8H2O = M(OH)2X2·7H2O), the glassy solids with α < 2, and hydrolyzed products (α ≈ 0.5). The water content is also determined by α with hydroxide-hydrogen bonding replacing halide-hydrogen bonding as α decreases. A Eu3+-doped Zr,Cl glass exhibits photoluminescence transitions 5D0 â 7Fn (n = 1, 2, and 4) of Eu3+, illustrating the asymmetric nature of the dopant sites in the glass.
RESUMEN
This work complements our recent discovery of new phases derived from zirconium perchlorate by addition of hydrogen peroxide. Here, we investigate analogous reactions with hafnium perchlorate, which is found to have modifications of the Clearfield-Vaughan tetramer (CVT). For hafnium perchlorate derivatives, we find distorted versions of CVT by X-ray diffraction and study the reaction solutions by SAXS, Raman spectroscopy, and ESI-MS. Furthermore, we investigate mixed Hf-Zr solution and solid phases and find the latter resemble the zirconium family at low Hf concentrations and the hafnium family at higher hafnium contents.
RESUMEN
Selective dissolution of hafnium-peroxo-sulfate films in aqueous tetramethylammonium hydroxide enables extreme UV lithographic patterning of sub-10â nm HfO2 structures. Hafnium speciation under these basic conditions (pH>10), however, is unknown, as studies of hafnium aqueous chemistry have been limited to acid. Here, we report synthesis, crystal growth, and structural characterization of the first polynuclear hydroxo hafnium cluster isolated from base, [TMA]6 [Hf6 (µ-O2 )6 (µ-OH)6 (OH)12 ]â 38 H2 O. The solution behavior of the cluster, including supramolecular assembly via hydrogen bonding is detailed via small-angle X-ray scattering (SAXS) and electrospray ionization mass spectrometry (ESI-MS). The study opens a new chapter in the aqueous chemistry of hafnium, exemplifying the concept of amphoteric clusters and informing a critical process in single-digit-nm lithography.
RESUMEN
Recently, monoalkyl oxo-hydroxo tin clusters have emerged as a new class of metal-oxide resist to support the semiconductor industry's transition to extreme ultraviolet (EUV) lithography. Under EUV exposure, these tin-based clusters exhibit higher performance and wider process windows than conventional polymer materials. A promising new monoalkyl precursor, [(BuSn)12 O14 (OH)6 ][OH]2 (BuSn), is still in its infancy in terms of film formation. However, understanding potential environmental effects could significantly affect future development as a commercial product. We synthesized and explored the toxicity of nano-BuSn in the alga Chlamydomonas reinhardtii and the crustacean Daphnia magna at exposure concentrations ranging from 0 to 250 mg/L. Nano-BuSn had no effect on C. reinhardtii growth rate irrespective of concentration, whereas high nanoparticle concentrations (≥100 mg/L) increased D. magna immobilization and mortality significantly. To simulate an end-of-life disposal and leachate contamination, BuSn-coated film wafers were incubated in water at various pH values and temperatures for 14 and 90 d to investigate leaching rates and subsequent toxicity of the leachates. Although small quantities of tin (1.1-3.4% of deposited mass) leached from the wafers, it was insufficient to elicit a toxic response regardless of pH, incubation time, or temperature. The low toxicity of the tin-based thin films suggests that they can be an environmentally friendly addition to the material sets useful for semiconductor manufacturing. Environ Toxicol Chem 2019;38:2651-2658. © 2019 SETAC.