We compare the performance, stability and microstructure of Si/Gd multilayers containing thin barrier layers of W, ${\mathrm{B}}_4\mathrm{C}$ , or $\mathrm{Si}{\mathrm{N}}_x$ , and determine that multilayers containing $0.6\mathrm{nm}$ thick W barrier layers at each interface provide the best compromise between high peak reflectance in the extreme ultraviolet near $\lambda =60\mathrm{nm}$ and good stability upon heating. The Si/W/Gd films have sharper interfaces and also show vastly superior thermal stability relative to Si/Gd multilayers without barrier layers. We find that these structures have relatively small compressive film stresses, and show good temporal stability thus far. We measured a peak reflectance of 29.7% at $\lambda =62.5\mathrm{nm}$ , and a spectral bandpass of $\mathrm{\Delta }\lambda =9\mathrm{nm}$ (FWHM), for an optimized Si/W/Gd multilayer having a period $d=32.0\mathrm{nm}$ .