We present a study of the electrical, structural and chemical properties of Ti contacts on atomic layer deposited α-Ga2O3 fi lms. Ti forms an ohmic contact with α-Ga2O3. The contact performance is highly dependent on the post-evaporation annealing temperature, where an improved conductivity is obtained for annealing at 450 ⁰C, and a strong degradation for annealing at greater temperatures. Structural and chemical characterisation by transmission electron microscopy techniques reveal that the electrical improvement or degradation of the contact upon annealing can be attributed to oxidation of the Ti metallic layer by the Ga2O3 film in combination with the possibility for Ti diffusion into the Au layer. The results highlight that the grain boundaries and inclusions in the Ga2O3 film provide fast diffusion pathways for this reaction, leaving the α-Ga2O3 crystallites relatively unaffected { this result differs from previous reports conducted on α -Ga2O3. This study underlines the necessity for a phase-speci c and growth method-speci c study of contacts on Ga2O3 devices.