Search for: All records

Post deposition annealing of molecular layer- deposited (MLD) hafnicone films was examined and compared to that of hafnium oxide atomic layer-deposited (ALD) films. Hafnicone films were deposited using tetrakis(dimethylamido)- hafnium (TDMAH), and ethylene glycol and hafnia films were deposited using TDMAH and water at 120 °C. The changes in the properties of the as-deposited hafnicone films with annealing were probed by various techniques and then compared to the as-deposited and annealed ALD hafnia films. In situ X-ray reflectivity indicated a 70% decrease in thickness and ∼100% increase in density upon heating to 400 °C yet the density remained lower than that of hafnia control samples. The largest decreases in thickness of the hafnicone films were observed from 150 to 350 °C. In situ X-ray diffraction indicated an increase in the temperature required for crystallization in the hafnicone films (600 °C) relative to the hafnia films (350 °C). The changes in chemistry of the hafnicone films annealed with and without UV exposure were probed using Fourier transformed infrared spectroscopy and X-ray photoelectron spectroscopy with no significant differences attributed to the UV exposure. The hafnicone films exhibited lower dielectric constants than hafnia control samples over the entire temperature range examined. The CF4/O2 etch rate of the hafnicone films was comparable to the etch rate of hafnia films after annealing at 350 °C. The thermal conductivity of the hafnicone films initially decreased with thermal processing (up to 250 °C) and then increased (350 °C), likely due to porosity generation and subsequent densification, respectively. This work demonstrates that annealing MLD films is a promising strategy for generating thin films with a low density and relative permittivity. 

Atomic layer deposition (ALD) of ruthenium (Ru) is being investigated for next generation interconnects and conducting liners for copper metallization. However, integration of ALD Ru with diffusion barrier refractory metal nitrides, such as tantalum nitride (TaN), continues to be a challenge due to its slow nucleation rates. Here, we demonstrate that an ultraviolet-ozone (UV-O3) pretreatment of TaN leads to an oxidized surface that favorably alters the deposition characteristics of ALD Ru from islandlike to layer-by-layer growth. The film morphology and properties are evaluated via spectroscopic ellipsometry, atomic force microscopy, electrical sheet resistance measurements, and thermoreflectance. We report a 1.83 nm continuous Ru film with a roughness of 0.19 nm and a sheet resistance of 10.8 KΩ/□. The interface chemistry between TaN and Ru is studied by x-ray photoelectron spectroscopy. It is shown that UV-O3 pretreatment, while oxidizing TaN, enhances Ru film nucleation and limits further oxidation of the underlying TaN during ALD. An oxygen “gettering” mechanism by TaN is proposed to explain reduced oxygen content in the Ru film and higher electrical conductivity compared to Ru deposited on native-TaN. This work provides a simple and effective approach using UV-O3 pretreatment for obtaining sub-2 nm, smooth, and conducting Ru films on TaN surfaces. 

As various property studies continue to emerge on high entropy and entropy-stabilized ceramics, we seek a further understanding of the property changes across the phase boundary between “high-entropy” and “entropy-stabilized” phases. The thermal and mechanical properties of bulk ceramic entropy stabilized oxide composition Mg 0.2 Co 0.2 Ni 0.2 Cu 0.2 Zn 0.2 O are investigated across this critical transition temperature via the transient plane-source method, temperature-dependent x-ray diffraction, and nano-indentation. The thermal conductivity remains constant within uncertainty across the multi-to-single phase transition at a value of ≈2.5 W/mK, while the linear coefficient of thermal expansion increases nearly 24% from 10.8 to 14.1 × 10 −6 K −1 . Mechanical softening is also observed across the transition. 

Abstract Amorphous chalcogenide alloys are key materials for data storage and energy scavenging applications due to their large non-linearities in optical and electrical properties as well as low vibrational thermal conductivities. Here, we report on a mechanism to suppress the thermal transport in a representative amorphous chalcogenide system, silicon telluride (SiTe), by nearly an order of magnitude via systematically tailoring the cross-linking network among the atoms. As such, we experimentally demonstrate that in fully dense amorphous SiTe the thermal conductivity can be reduced to as low as 0.10 ± 0.01 W m −1 K −1 for high tellurium content with a density nearly twice that of amorphous silicon. Using ab-initio simulations integrated with lattice dynamics, we attribute the ultralow thermal conductivity of SiTe to the suppressed contribution of extended modes of vibration, namely propagons and diffusons. This leads to a large shift in the mobility edge - a factor of five - towards lower frequency and localization of nearly 42% of the modes. This localization is the result of reductions in coordination number and a transition from over-constrained to under-constrained atomic network.