X-ray reflectivity using energy dispersive x-ray detection has been used to investigate the characteristics of vacuum-deposited thin films. A resolution of 0.3 nm for thicknesses in the range 3-200 nm and of 0.05 nm for roughness in the range 0.1-3 nm has been demonstrated. Furthermore, it is shown that by using energy dispersive detection, spectra can be obtained in less than 500 s allowing real time studies to be performed. Thin, discrete Cr/Al deposits on quartz substrates have been investigated, and the presence of a 1.5 nm thick Al/Cr intermetallic layer formed during room-temperature deposition has been determined. During annealing at 250-degrees-C, the Cr layer thickness decreases linearly with time until approximately 4 nm is consumed in additional intermetallic formation; further annealing does not change the Cr layer thickness.