Microstructure and electrical conductivity in shape and size controlled molybdenum particle thick film

We study the effects of particle morphology on the microstructure and electrical conductivity of Mo particle thick films. In our study, the shape and size of molybdenum (Mo) particles are modified by mechanical ball-milling and atomic layer deposition (ALD). As the total number of collisions between Mo particles and ball-milling media increases, Mo particles are deformed, and the shape of Mo particles changed from irregular polyhedrons to thin flakes. In the ball-milling process, stress frequency is an important processing parameter governing the deformation and breakage of Mo particles. In addition, ALD-grown TiO2 layer is found to significantly suppress the growth of Mo particles at high temperature. After 1000 °C annealing, the particle size of the TiO2 layer-coated film is only half of that of bare Mo particle films. The shape of the particles changes electrical conductivity of the Mo thick films. Large contact area between flake shape particles can increase the carrier mobility of the film and the 5-nm thick TiO2 layer can provide the inter-particle carrier transport path via a tunneling mechanism. Our results show that the combined use of the ball-milling and the ALD coating leads to Mo thick films with high electric conductivity and large surface area.