Aluminum nitride (AlN) is a semiconductor with a very wide band gap and a potential dielectric material. Deposition of thin AlN films is routinely done by several techniques, including atomic layer deposition (ALD). In this study, we deposited AlN using ALD with trimethylaluminum (TMA) as the Al precursor and ammonia (NH3) with and without plasma activation as the N precursor in the temperature range from 100 to 400 degrees C while monitoring the surface reactions using mass spectrometry. Our results, combined with recent quantum chemical modelling, suggest that the surface chemistry of the deposition process is chemisorption of TMA followed by reductive elimination of the methyl groups to render mono methyl aluminum species. The NH3 chemisorption is done by ligand exchange to form CH4 and an -NH2 terminated surface.

Dialkylamido compounds, such as tris-dimethylamido aluminum (TDMAA, Al(NMe2)3) and tetrakis-dimethylamido titanium (TDMAT, Ti(NMe2)4) are interesting precursors for depositing nitrides using atomic layer deposition (ALD) due to their high volatility and reactivity at low temperatures. In this study, we explored surface chemistry using mass spectrometry and discovered that the surface mechanisms involved beta-hydride elimination and ligand decomposition, as well as transamination and hydrogenation reactions which facilitate ligand exchange. This is mainly based on the -N(Me)2 and HN(Me)2 detected during both TDMAA and NH3 pulses, and CH4 signals detected during the NH3 pulse stage. The expected reductive elimination of the two dimethylamido ligands, via a direct nitrogen-nitrogen coupling reaction was not observed, suggesting that it is less thermodynamically favorable compared to reduction by NH3. Arrhenius analysis between 150 and 300 degrees C found activation energies (Ea) = 27-30 kJ mol-1 and pre-exponential factors (A) = 3-5 s-1 for the reaction between TDMAA and NH3.

Different approaches are used in tailoring properties of thin films to meet the requirements of specific applications. This study comprises work done on atomic layer deposition of Al (x) Ti1-x N employing the co-evaporation approach using tris-dimethylamido aluminum [Al(NMe2)(3)], tetrakis(dimethylamido)titanium (IV) [Ti(NMe2)(4)], and ammonia (NH3) plasma. High Al-content, low impurity (O and C, both <5 at. %) films with uniform grain size distribution and dense morphology were deposited. The as-deposited films were x-ray amorphous, but mixed crystallographic phases were observed when the films were annealed at 700 degrees C. The deposited aluminum-rich Al (x) Ti1-x N films show an alternative way for ternary material depositions.

Aluminum titanium nitride (AlxTi1-xN, 0 < x < 1) is a critical hard coating material for cutting tools due to its exceptional hardness, thermal stability, wear resistance, and oxidation resistance, all of which are influenced by its Al content. A common method to swiftly estimate the Al content in production of such coatings is by the size of the AlxTi1-xN unit cell – determined by standard θ-2θ X-ray diffraction – and the equilibrium cell size of the binary constituents AlN and TiN in the framework of Vegard's law. However, in most cases, the measured unit cell size does not merely depend on Al content as AlxTi1-xN is a metastable phase that may exhibit crystalline defects, non-ideal mixing of the binaries, differences in bonding characteristics, strain relaxation, and phase separation. We seek to investigate the resulting uncertainty in Vegard's-law-based estimation by comparing estimated Al content with elemental composition of AlxTi1-xN coatings – grown industrially by chemical vapor deposition on cemented tungsten carbide substrates – using energy-dispersive X-ray spectroscopy, hard X-ray photoelectron spectroscopy, time-of-flight elastic recoil detection analysis, and Rutherford backscattering spectrometry. Our results demonstrate that the uncertainties in Al content estimated by Vegard's law are relatively small, rendering this method a good first-order approach for compositional analysis of the metal sub-lattices in AlxTi1-xN. Moreover, our data indicate that a multimethod strategy is required for precise composition determination that includes both the metal and the non-metal sublattices and impurity level.