Hafnia: Energetics of thin films and nanoparticles

Abstract

Articles you may be interested inEffect of postdeposition annealing on the electrical properties of β-Ga2O3 thin films grown on p-Si by plasmaenhanced atomic layer deposition J. Vac. Sci. Technol. A 32, 041504 (2014); 10.1116/1.4875935 High temperature phase transformation studies in magnetite nanoparticles doped with Co2+ ion J. Appl. Phys. 112, 054320 (2012); 10.1063/1.4748318Copper coverage effect on tungsten crystallites texture development in W/Cu nanocomposite thin films Crystallization energetics of amorphous hafnia powders and thin films on platinum substrates was studied by differential scanning calorimetry and time-resolved high temperature x-ray diffraction. For initially amorphous 25 and 20 nm films from atomic layer deposition, crystallization enthalpy decreases from Ϫ38 to Ϫ32 kJ/mol, and crystallization temperature increases from 388 to 417°C as thickness decreases. Enthalpy of water vapor adsorption on the surface of monoclinic hafnia was measured for both bulk powder and nanoparticles and was found to vary from Ϫ110 to Ϫ130 kJ/mol for coverage of ϳ5 H 2 O / nm 2 . The enthalpies of monoclinic hafnia with various surface areas, prepared by crystallization and annealing of an amorphous hafnia precursor, were measured by high temperature oxide melt solution calorimetry. Under the previously used assumption that the interfacial enthalpy is 20% of the surface enthalpy, the surface enthalpy was calculated from experimental data as 2.8Ϯ 0.1 J / m 2 for the hydrated surface and 3.7Ϯ 0.1 J / m 2 for the anhydrous hafnia surface. These values are similar to those measured previously for monoclinic zirconia.⌬H ds is the drop solution enthalpy measured by high temperature oxide melt solution calorimetry. e ⌬H ds−1 is the corrected drop solution enthalpy of hydrated monoclinic hafnia. f ⌬H ds−2 is the corrected drop solution enthalpy of anhydrous monoclinic hafnia nanoparticles. 123514-4Zhou et al.

Cadmium selenide: Surface and nanoparticle energetics

“…Similar differences between the experimental and the theoretical surface enthalpies have been seen for several oxide nanomaterials, namely ZnO, 21 ZrO 2 , 22 and HfO 2 . 29 We conclude that CdSe has a smaller surface energy than most oxides, including wurtzite ZnO (the surface energy of its hydrated surface is 1.31 6 0.07 J/m 2 and that of the anhydrous surface is 2.55 6 0.23 J/m 2 ). 21 The value of surface energy for CdSe obtained by calorimetry is significantly larger than that from theoretical calculations, possibly reflecting the variety and the imperfection of surfaces exposed in the real material.…”

“…SA can be obtained directly by BET measurement, and the IA not accessible directly can be estimated as follows 22,29 :…”

The energetics of nanophase calcite

“…Thus the BET surface area values will be used for further analysis of calorimetric data. This has also been done in many of our earlier studies on surface energies of oxides (Levchenko et al, 2006;Mazeina et al, 2006;Park et al, 2010;Zhou et al, 2010).…”

The origin of ferroelectricity in Hf1−xZrxO2: A computational investigation and a surface energy model

“…These ZrO2 films with grain size below 30 nm are typically in the t-phase and the involved surface energy relative to the m-phase was experimentally measured by Pitcher et al and other groups 20,21 and calculated by Christensen and Carter 22 . The same effect is known for HfO2 which undergoes a phase transformation at a critical particle size of about 4 nm, but the surface energy has only been measured for the m-phase 23 . Müller 2 observed the size effect in ferroelectric Hf0.5Zr0.5O2 thin films by identifying the thinner 7.5 nm film as less ferroelectric and more antiferroelectric than the thicker 9 nm film.…”