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Smooth and continuous films of nickel nitride (NiN x ) with excellent step coverage were deposited from a novel nickel amidinate precursor, Ni(MeC(N t Bu)2)2, and either ammonia (NH3) or a mixture of NH3 and hydrogen (H2) gases as co-reactants. The reactants were injected together in direct-liquid-injection chemical vapor deposition (DLI-CVD) processes at substrate temperatures of 160−200 °C. Depending on the ratio of NH3 to H2 gases during deposition, the Ni:N atomic ratio in DLI-CVD NiN x films could be varied from ∼3:1 to ∼15:1, having either a cubic nickel structure or a mixture of hexagonal Ni3N and cubic Ni4N crystal structures with an incorporation of nitrogen as low as 6%. The chemical vapor deposition (CVD) growth rates of NiN x could be increased to more than 5 nm/min. The CVD films were smooth and continuous, and they had ∼100% step coverage in high-aspect-ratio (>50:1) holes. The as-deposited NiN x films had resistivities as low as ∼50 μΩ cm for film thicknesses of ∼25 nm. Annealing of the films in H2 at 160 °C or hydrogen plasma treatment at room temperature removed the nitrogen and led to pure nickel films.

The mechanism of thermal dry etching of cobalt films is discussed for a thermal process utilizing sequential exposures to chlorine gas and a diketone [either 1,1,1,5,5,5-hexafluoro-2,4-pentanedione (hexafluoroacetylacetone, hfacH) or 2,4-pentanedione (acetylacetone, acacH)]. The process can be optimized experimentally to approach atomic layer etching (ALE); a sequential exposure to Cl 2 and hfacH dry etchants at 140°C is shown to proceed efficiently. The use of acacH as a diketone does not result in ALE with chlorine even at 180°C, but the decrease of surface chlorine concentration and chemical reduction of cobalt is noted. However, thermal desorption analysis suggests that the reaction of chlorinated cobalt surface exposed to the ambient conditions (oxidized) with hfacH does produce volatile Co-containing products within the desired temperature range and the products contain Co 3+. The effect of adsorption of ligands on the energy required to remove surface cobalt atoms is evaluated using the density functional theory.

Synthesis and growth of Vanadium dioxide on Silicon substrates has been investigated by Atomic Layer Deposition (ALD). ALD Vanadium oxide films were synthesized by using the novel Tetrakis[ethylmethylamino] vanadium {V(NEtMe)4} [TEMAV], as the vanadium precursor source and H2O vapor as the oxidizing source. The as-prepared ALD thin films were amorphous due to low temperature growth at 150 oC and exhibit a mixture of V2O5 and VO2 phases, which originiate from the V4+ and V5+ valence states of Vanadium found in the initially amorphous ALD thin film. We found that VO2 formation is strongly dependent on the amount of pressure and oxygen. The VO2 films were formed at 450 -500 oC and with an oxygen flow rate of less than 1 sccm in a vacuum of 2.7 E-2 Torr. ALD VO2 films, after furnace annealing, demonstrate well-formed roundish grains. The ALD VO2 thin films yielded an rms roughness of 3 nm by AFM analysis and are random polycrystalline after annealing.

Among the many vanadium suboxides and different stoichiometries, VO 2 has received considerable attention due to its remarkable metal-insulator transition (MIT) behavior, which causes a significant reversible change in its electrical and optical properties occurring across the phase transition at 67 • C. The initially amorphous VO 2 thin films were fabricated by the emerging, Atomic Layer Deposition (ALD) technique with (tetrakis [ethylmethylamino]vanadium) {V(NEtMe) 4 } as precursor and H 2 O vapor as oxidation agent. For benchmarking we have also used the RF Magnetron Sputtering technique to deposit metallic vanadium thin films, which were later oxidized during furnace annealing. Post annealing of the as-deposited ALD films was performed in order to obtain the technologically important form of crystallized VO 2 thin films using furnace annealing. All film depositions were carried out on native oxide covered (100) Si substrates. The conditions for successful furnace annealing are reported in terms of temperature and annealing gas composition and the physical characterization results are presented. VO 2 exhibits many technologically remarkable properties that lie at the core of the renewed interest in this material. In particular, VO 2 shows a semiconductor-metal transition (SMT) or metal-insulator transition (MIT) at ∼67• C. This (MIT) phase transition at ∼67 • C is accompanied by a reversible change in its electrical and optical properties.1-3 At low-temperatures below the transition, VO 2 shows a semiconducting phase that has a monoclinic crystal structure. When the temperature rises above the transition temperature, the VO 2 exhibits its metallic phase which has a rutile crystal structure. The MIT of VO 2 is attributed to the combination of Mott-Hubbard transition with Peierls transition. 4 Electrically, the change in resistivity of bulk VO 2 across the MIT temperature can be as large as four or five orders of magnitude. Optically, crystalline VO 2 thin films exhibit good infrared transmission in the insulating monoclinic phase below the MIT temperature, while the metallic rutile phase is highly reflective in the infrared region. 5,6 Based on these temperature dependent optical transmission changes crystalline VO 2 is also known as a thermochromic material, which can be employed as thin films in smart window applications to reduce air condition and heating costs. Because of these physical properties VO 2 films have the potential to be used in nonvolatile resistive memories, switches in microelectronics and optical sensors and smart window applications.However, the V-O system has been reported to contain about 25 compounds and suboxide phase. 7,8 It is experimentally challenging to find the optimum combination of different furnace annealing parameters that would result in the accurate mixture of vanadium and oxygen in the desired proportion to obtain the stoichiometric VO 2 phase. Even a 1% change in the oxygen content of the annealing atmosphere in the furnace would further oxidize the initially amorphous va...