Aluminum nitride (AlN) thin films obtained by pulsed laser deposition (PLD) with a KrF * laser source (λ=248nm, τ≥7ns) at a substrate temperature of 800°C and different values of ambient nitrogen pressure up to 10Pa have been studied. Precursors in the plasma plume were studied by optical multichannel emission spectroscopy. Emission spectra taken close to the target revealed the presence of atomic, single and multiple ionized Al and N species, as well as AlN molecular species. The analysis of the XRD patterns revealed that all films had a polycrystalline structure with mixed cubic and hexagonal phases. For AlN films deposited in vacuum, the structure is predominantly cubic with a small fraction of hexagonal phase. The cubic phase had a lattice parameter of 0.4045nm. The films deposited in nitrogen ambient have a cubic crystalline structure. At maximum nitrogen pressure of 10Pa the lattice parameter decreases to a=0.3949nm.