Correlation of interface chemistry to electrical properties of metal contacts on diamond
Three different metals (Au, Al and Ti) were deposited on polycrystalline diamond films. The effects of post-deposition annealing and pre-deposition Ar+ sputtering were examined. Au and Al did not chemically interact with diamond and formed rectifying contacts on the as-grown surface. The non-reactive interface is an important factor in forming rectifying contacts on diamond. On the contrary, Ti formed a carbide at the interface upon annealing. The resulting contact showed ohmic characteristics. Au was nonreactive even on an Ar+-sputtered diamond surface, while Ti and Al formed carbides on this surface upon annealing at temperatures as low as 430 °C. Ti and Al on the sputtered surface resulted in ohmic contacts. Based on these observations, a model of the metal-diamond interface band structure is presented. Combining experimental results with bulk thermodynamic data of carbides has allowed an understanding of the interface chemistry between diamond and various metals.