“…Bonding without an intermediate layer, known as direct or fusion bonding, is simple in the sense that no foreign material is introduced to the process and the number of material interfaces is minimized. Silicon-silicon (Christiansen, Singh, & Gösele, 2006), glass-glass (Xue et al, 1997;Chiem et al, 2000;Jia, Fang, & Fang, 2004), quartz-quartz , PMMA-PMMA (Chen et al, 2004), and many other direct bonding processes are in use. The most general purpose bonding technique, however, is adhesive bonding (Niklaus et al, 2001a(Niklaus et al, , 2006, where an intermediate layer of material is added to the system to facilitate bonding.…”