Comparative study of Ti and Cr adhesion to the AlN ceramic: Experiments and calculations

In this manuscript, ceramic substrates with different adhesion layers were prepared by the direct-plated-copper (DPC) method. Microstructure and mechanical properties were investigated by scanning electron microscopy (SEM) and adhesion strength tests. SEM results showed that the AlN/Ti/Cu interface had fewer defects than AlN/Cr/Cu and AlN/Cu. The adhesion strength of the Ti layer samples was about 16.5 MPa, which is much higher compared with Cr and no adhesion layer samples. The adhesion strength of the AlN/Ti/Cu sample was the highest, followed by AlN/Cr/Cu, and AlN/Cu adhesion was the lowest. The AlN (0 0 1)/Ti (0 0 1) and AlN (0 0 1)/Cr (1 1 0) interfaces were studied by the first principles calculations based on the density functional theory (DFT). It appears that the Ti-N bonds were formed by the Ti-spd and N-p orbital hybridization. Moreover, the electron transition from Ti atom to N atom was higher than that from Cr to N. The bond length of Ti-N bond is shorter than Cr-N bond length, and its population has proven that Ti-N has stronger covalent character, which may be the reason why the AlN/Ti/Cu interface has higher interfacial stability than AlN/Cr/Cu.