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 TiN 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 TiN bond is shorter than CrN bond length, and its population has proven that TiN has stronger covalent character, which may be the reason why the AlN/Ti/Cu interface has higher interfacial stability than AlN/Cr/Cu.