TEMPERATURE-INDUCED DIFFUSION IN MO SI MULTILAYER MIRRORS/

To optimize the growth process of Mo/Si multilayers, the effect of an elevated substrate temperature during deposition has been studied in t he temperature range between 300 K and 550 K. Multilayer properties, s uch as interface roughness, d-spacing, and structure of the layers, ha ve been investigated during deposition and cool-down, after cool-down, and during heating. A number of techniques have been used: small-angl e, near-normal incidence, and in situ reflectivity measurements. It is found that the increased substrate temperature changes the interface roughness to a minimum value for samples produced at 488 K. Also, a ch ange of the d-spacing as a function of time and temperature is observe d and is explained by annihilation of free volume of the Si layer. The atomic structures of the layers deposited at different temperatures h ave been analyzed with high resolution electron microscopy (TEM), whic h shows that both materials are amorphous for the entire temperature r ange investigated. At the extremes of the temperature range investigat ed irregular layer structures, such as ripples and V-shaped structures , have been observed by TEM. (C) 1998 American Institute of Physics.