Atomic layer deposition of nickel oxide films using $Ni(dmamp)2$ and water

A precursor originally synthesized for the chemical vapor deposition of metallic nickel, $Ni(dmamp)2$ (⁠$dmamp=$1-dimethylamino-2-methyl-2-propanolate, -$OCMe2CH2NMe2$⁠), has been adopted as a nickel source for the atomic layer deposition of nickel oxide (NiO) using water $(H2O)$ as the oxygen source. The precursor is a solid at room temperature, but readily sublimes at 90 °C. The self-limiting atomic layer deposition (ALD) process by alternate surface reactions of $Ni(dmamp)2$ and $H2O$ was confirmed from thickness measurements of the NiO films grown with varying $Ni(dmamp)2$ supply times and numbers of the $Ni(dmamp)2-H2O$ ALD cycles. The ALD temperature window for this precursor was found to be between 90 and 150 °C. Under optimal reaction conditions, the growth rate of the NiO films was $∼0.8Å∕cycle$⁠. The NiO films deposited on Si(001) at 120 °C were characterized by x-ray diffraction, x-ray photoelectron spectroscopy, scanning electron microscopy, and atomic force microscopy. The x-ray diffraction patterns showed no distinct peaks for NiO, indicating that the films deposited at this temperature were amorphous. X-ray photoelectron spectroscopy analysis showed the films to be stoichiometric with no detectable amount of carbon impurities. For a film with the thickness of 810 Å (with 1000 ALD cycles) the root-mean-square surface roughness was only $∼4Å$ as measured by atomic force microscopy. To elucidate the ALD mechanism of the Ni precursor with water, a quadrupole mass analyzer was employed with $D2O$ as the oxygen source in lieu of $H2O$⁠. Interestingly, unlike the usual ALD fashion, the $Ni(dmamp)2$ precursor does not seem to decompose but only coordinatively bond to the OH-terminated surface when it was introduced. Next, the $Ni(dmamp)2$-surface species decompose to produce a hydroxylated nickel oxide surface and the alcohol dmampH when water was supplied.