Boron-based multilayer mirrors have theoretical reflectivities > 50% for wavelengths between 65 and approximately 120 angstrom. Such multilayers would be quite useful, since this wavelength region lies above that for which W/C functions, and below that for which Mo/Si works well. We have studied the growth of several candidate materials on boron in order to determine their growth modes, the chemical sharpness of the interfaces, and the structure of the layers formed. The films were deposited in ultrahigh vacuum and studied with in situ Auger electron spectroscopy (AES), x-ray photoelectron spectroscopy (XPS), and reflection high-energy electron diffraction. Scanning tunneling microscopy characterization and Rutherford backscattering calibrations were performed after removing the samples from the vacuum system. For all of these studies amorphous B films were first formed by depositing at room temperature onto oxidized Si wafers. Following deposition of each B film, overlayers of Pd, Ag, or Si were deposited at substrate temperatures of approximately 50 degree(s)C and immediately studied with AES and XPS. In the Pd case, we find that it reacts with the B to form a smooth, amorphous PdxB1-x layer, with x approximately equals 0.9. This reaction occurred for all Pd coverages studied, from 2.3 to 230 angstrom. However, due to high Pd content of this reacted compound, our calculations show that the PdxB1-x should perform as a good absorber layer as part of PdxB1-x/B multilayer mirrors. We find that Si deposited onto B forms a sharp interface and an amorphous overlayer of pure Si. Depositing Ag on B results in a polycrystalline layer, composed of large Ag islands.